[PATCH v15 00/12] Implement copy offload support

[PATCH v15 00/12] Implement copy offload support

[Nitesh Shetty]

The patch series covers the points discussed in past and most recently
in LSFMM'23[0].
We have covered the initial agreed requirements in this patch set and
further additional features suggested by community.

This is next iteration of our previous patch set v14[1].
Copy offload is performed using two bio's -
1. Take a plug
2. The first bio containing source info is prepared and sent,
        a request is formed.
3. This is followed by preparing and sending the second bio containing the
        destination info.
4. This bio is merged with the request containing the source info.
5. The plug is released, and the request containing source and destination
        bio's is sent to the driver.

So copy offload works only for request based storage drivers.
For failures, partial completion, absence of copy offload capability,
we can fallback to copy emulation.

Overall series supports:
========================
	1. Driver
		- NVMe Copy command (single NS, TP 4065), including support
		in nvme-target (for block and file back end).

	2. Block layer
		- Block-generic copy (REQ_OP_COPY_DST/SRC), operation with
                  interface accommodating two block-devs
                - Merging copy requests in request layer
		- Emulation, for in-kernel user when offload is natively 
                absent
		- dm-linear support (for cases not requiring split)

	3. User-interface
		- copy_file_range

Testing
=======
	Copy offload can be tested on:
	a. QEMU: NVME simple copy (TP 4065). By setting nvme-ns
		parameters mssrl,mcl, msrc. For more info [2].
	b. Null block device
        c. NVMe Fabrics loopback.
	d. blktests[3]

	Emulation can be tested on any device.

	fio[4].

Infra and plumbing:
===================
        We populate copy_file_range callback in def_blk_fops. 
        For devices that support copy-offload, use blkdev_copy_offload to
        achieve in-device copy.
        However for cases, where device doesn't support offload,
        fallback to generic_copy_file_range.
        For in-kernel users (like NVMe fabrics), use blkdev_copy_offload
        if device is copy offload capable or else fallback to emulation 
        using blkdev_copy_emulation.
        Modify checks in generic_copy_file_range to support block-device.

Blktests[3]
======================
	tests/block/035-040: Runs copy offload and emulation on null
                              block device.
	tests/block/050,055: Runs copy offload and emulation on test
                              nvme block device.
        tests/nvme/056-067: Create a loop backed fabrics device and
                              run copy offload and emulation.

Future Work
===========
	- loopback device copy offload support
	- upstream fio to use copy offload
	- upstream blktest to test copy offload
        - update man pages for copy_file_range
        - expand in-kernel users of copy offload

	These are to be taken up after this minimal series is agreed upon.

Additional links:
=================
	[0] https://lore.kernel.org/linux-nvme/CA+1E3rJ7BZ7LjQXXTdX+-0Edz=zT14mmPGMiVCzUgB33C60tbQ@mail.gmail.com/
            https://lore.kernel.org/linux-nvme/f0e19ae4-b37a-e9a3-2be7-a5afb334a5c3@nvidia.com/
            https://lore.kernel.org/linux-nvme/20230113094648.15614-1-nj.shetty@samsung.com/
	[1] https://lore.kernel.org/lkml/20230811105300.15889-1-nj.shetty@samsung.com/T/#t
	[2] https://qemu-project.gitlab.io/qemu/system/devices/nvme.html#simple-copy
	[3] https://github.com/nitesh-shetty/blktests/tree/feat/copy_offload/v15
	[4] https://github.com/OpenMPDK/fio/tree/copyoffload-3.35-v14

Changes since v14:
=================
        - block: (Bart Van Assche)
            1. BLK_ prefix addition to COPY_MAX_BYES and COPY_MAX_SEGMENTS
            2. Improved function,patch,cover-letter description
            3. Simplified refcount updating.
        - null-blk, nvme:
            4. static warning fixes (kernel test robot)

Changes since v13:
=================
        - block:
            1. Simplified copy offload and emulation helpers, now
                  caller needs to decide between offload/emulation fallback
            2. src,dst bio order change (Christoph Hellwig)
            3. refcount changes similar to dio (Christoph Hellwig)
            4. Single outstanding IO for copy emulation (Christoph Hellwig)
            5. use copy_max_sectors to identify copy offload
                  capability and other reviews (Damien, Christoph)
            6. Return status in endio handler (Christoph Hellwig)
        - nvme-fabrics: fallback to emulation in case of partial
          offload completion
        - in kernel user addition (Ming lei)
        - indentation, documentation, minor fixes, misc changes (Damien,
          Christoph)
        - blktests changes to test kernel changes

Changes since v12:
=================
        - block,nvme: Replaced token based approach with request based
          single namespace capable approach (Christoph Hellwig)

Changes since v11:
=================
        - Documentation: Improved documentation (Damien Le Moal)
        - block,nvme: ssize_t return values (Darrick J. Wong)
        - block: token is allocated to SECTOR_SIZE (Matthew Wilcox)
        - block: mem leak fix (Maurizio Lombardi)

Changes since v10:
=================
        - NVMeOF: optimization in NVMe fabrics (Chaitanya Kulkarni)
        - NVMeOF: sparse warnings (kernel test robot)

Changes since v9:
=================
        - null_blk, improved documentation, minor fixes(Chaitanya Kulkarni)
        - fio, expanded testing and minor fixes (Vincent Fu)

Changes since v8:
=================
        - null_blk, copy_max_bytes_hw is made config fs parameter
          (Damien Le Moal)
        - Negative error handling in copy_file_range (Christian Brauner)
        - minor fixes, better documentation (Damien Le Moal)
        - fio upgraded to 3.34 (Vincent Fu)

Changes since v7:
=================
        - null block copy offload support for testing (Damien Le Moal)
        - adding direct flag check for copy offload to block device,
	  as we are using generic_copy_file_range for cached cases.
        - Minor fixes

Changes since v6:
=================
        - copy_file_range instead of ioctl for direct block device
        - Remove support for multi range (vectored) copy
        - Remove ioctl interface for copy.
        - Remove offload support in dm kcopyd.

Changes since v5:
=================
	- Addition of blktests (Chaitanya Kulkarni)
        - Minor fix for fabrics file backed path
        - Remove buggy zonefs copy file range implementation.

Changes since v4:
=================
	- make the offload and emulation design asynchronous (Hannes
	  Reinecke)
	- fabrics loopback support
	- sysfs naming improvements (Damien Le Moal)
	- use kfree() instead of kvfree() in cio_await_completion
	  (Damien Le Moal)
	- use ranges instead of rlist to represent range_entry (Damien
	  Le Moal)
	- change argument ordering in blk_copy_offload suggested (Damien
	  Le Moal)
	- removed multiple copy limit and merged into only one limit
	  (Damien Le Moal)
	- wrap overly long lines (Damien Le Moal)
	- other naming improvements and cleanups (Damien Le Moal)
	- correctly format the code example in description (Damien Le
	  Moal)
	- mark blk_copy_offload as static (kernel test robot)
	
Changes since v3:
=================
	- added copy_file_range support for zonefs
	- added documentation about new sysfs entries
	- incorporated review comments on v3
	- minor fixes

Changes since v2:
=================
	- fixed possible race condition reported by Damien Le Moal
	- new sysfs controls as suggested by Damien Le Moal
	- fixed possible memory leak reported by Dan Carpenter, lkp
	- minor fixes

Changes since v1:
=================
	- sysfs documentation (Greg KH)
        - 2 bios for copy operation (Bart Van Assche, Mikulas Patocka,
          Martin K. Petersen, Douglas Gilbert)
        - better payload design (Darrick J. Wong)

Anuj Gupta (1):
  fs/read_write: Enable copy_file_range for block device.

Nitesh Shetty (11):
  block: Introduce queue limits and sysfs for copy-offload support
  Add infrastructure for copy offload in block and request layer.
  block: add copy offload support
  block: add emulation for copy
  fs, block: copy_file_range for def_blk_ops for direct block device
  nvme: add copy offload support
  nvmet: add copy command support for bdev and file ns
  dm: Add support for copy offload
  dm: Enable copy offload for dm-linear target
  null: Enable trace capability for null block
  null_blk: add support for copy offload

 Documentation/ABI/stable/sysfs-block |  23 ++
 Documentation/block/null_blk.rst     |   5 +
 block/blk-core.c                     |   7 +
 block/blk-lib.c                      | 425 +++++++++++++++++++++++++++
 block/blk-merge.c                    |  41 +++
 block/blk-settings.c                 |  24 ++
 block/blk-sysfs.c                    |  36 +++
 block/blk.h                          |  16 +
 block/elevator.h                     |   1 +
 block/fops.c                         |  25 ++
 drivers/block/null_blk/Makefile      |   2 -
 drivers/block/null_blk/main.c        | 100 ++++++-
 drivers/block/null_blk/null_blk.h    |   1 +
 drivers/block/null_blk/trace.h       |  25 ++
 drivers/block/null_blk/zoned.c       |   1 -
 drivers/md/dm-linear.c               |   1 +
 drivers/md/dm-table.c                |  37 +++
 drivers/md/dm.c                      |   7 +
 drivers/nvme/host/constants.c        |   1 +
 drivers/nvme/host/core.c             |  79 +++++
 drivers/nvme/host/trace.c            |  19 ++
 drivers/nvme/target/admin-cmd.c      |   9 +-
 drivers/nvme/target/io-cmd-bdev.c    |  97 ++++++
 drivers/nvme/target/io-cmd-file.c    |  50 ++++
 drivers/nvme/target/nvmet.h          |   4 +
 drivers/nvme/target/trace.c          |  19 ++
 fs/read_write.c                      |   8 +-
 include/linux/bio.h                  |   6 +-
 include/linux/blk_types.h            |  10 +
 include/linux/blkdev.h               |  22 ++
 include/linux/device-mapper.h        |   3 +
 include/linux/nvme.h                 |  43 ++-
 32 files changed, 1128 insertions(+), 19 deletions(-)


base-commit: c50216cfa084d5eb67dc10e646a3283da1595bb6
-- 
2.35.1.500.gb896f729e2

[PATCH v15 01/12] block: Introduce queue limits and sysfs for copy-offload support

[Nitesh Shetty]

Add device limits as sysfs entries,
	- copy_max_bytes (RW)
	- copy_max_hw_bytes (RO)

Above limits help to split the copy payload in block layer.
copy_max_bytes: maximum total length of copy in single payload.
copy_max_hw_bytes: Reflects the device supported maximum limit.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
---
 Documentation/ABI/stable/sysfs-block | 23 ++++++++++++++++++
 block/blk-settings.c                 | 24 +++++++++++++++++++
 block/blk-sysfs.c                    | 36 ++++++++++++++++++++++++++++
 include/linux/blkdev.h               | 13 ++++++++++
 4 files changed, 96 insertions(+)

diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block
index 1fe9a553c37b..96ba701e57da 100644
--- a/Documentation/ABI/stable/sysfs-block
+++ b/Documentation/ABI/stable/sysfs-block
@@ -155,6 +155,29 @@ Description:
 		last zone of the device which may be smaller.
 
 
+What:		/sys/block/<disk>/queue/copy_max_bytes
+Date:		August 2023
+Contact:	linux-block@vger.kernel.org
+Description:
+		[RW] This is the maximum number of bytes that the block layer
+		will allow for a copy request. This is always smaller or
+		equal to the maximum size allowed by the hardware, indicated by
+		'copy_max_hw_bytes'. An attempt to set a value higher than
+		'copy_max_hw_bytes' will truncate this to 'copy_max_hw_bytes'.
+		Writing '0' to this file will disable offloading copies for this
+		device, instead copy is done via emulation.
+
+
+What:		/sys/block/<disk>/queue/copy_max_hw_bytes
+Date:		August 2023
+Contact:	linux-block@vger.kernel.org
+Description:
+		[RO] This is the maximum number of bytes that the hardware
+		will allow for single data copy request.
+		A value of 0 means that the device does not support
+		copy offload.
+
+
 What:		/sys/block/<disk>/queue/crypto/
 Date:		February 2022
 Contact:	linux-block@vger.kernel.org
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 0046b447268f..4441711ac364 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -59,6 +59,8 @@ void blk_set_default_limits(struct queue_limits *lim)
 	lim->zoned = BLK_ZONED_NONE;
 	lim->zone_write_granularity = 0;
 	lim->dma_alignment = 511;
+	lim->max_copy_hw_sectors = 0;
+	lim->max_copy_sectors = 0;
 }
 
 /**
@@ -82,6 +84,8 @@ void blk_set_stacking_limits(struct queue_limits *lim)
 	lim->max_dev_sectors = UINT_MAX;
 	lim->max_write_zeroes_sectors = UINT_MAX;
 	lim->max_zone_append_sectors = UINT_MAX;
+	lim->max_copy_hw_sectors = UINT_MAX;
+	lim->max_copy_sectors = UINT_MAX;
 }
 EXPORT_SYMBOL(blk_set_stacking_limits);
 
@@ -183,6 +187,22 @@ void blk_queue_max_discard_sectors(struct request_queue *q,
 }
 EXPORT_SYMBOL(blk_queue_max_discard_sectors);
 
+/*
+ * blk_queue_max_copy_hw_sectors - set max sectors for a single copy payload
+ * @q:	the request queue for the device
+ * @max_copy_sectors: maximum number of sectors to copy
+ */
+void blk_queue_max_copy_hw_sectors(struct request_queue *q,
+				   unsigned int max_copy_sectors)
+{
+	if (max_copy_sectors > (BLK_COPY_MAX_BYTES >> SECTOR_SHIFT))
+		max_copy_sectors = BLK_COPY_MAX_BYTES >> SECTOR_SHIFT;
+
+	q->limits.max_copy_hw_sectors = max_copy_sectors;
+	q->limits.max_copy_sectors = max_copy_sectors;
+}
+EXPORT_SYMBOL_GPL(blk_queue_max_copy_hw_sectors);
+
 /**
  * blk_queue_max_secure_erase_sectors - set max sectors for a secure erase
  * @q:  the request queue for the device
@@ -578,6 +598,10 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 	t->max_segment_size = min_not_zero(t->max_segment_size,
 					   b->max_segment_size);
 
+	t->max_copy_sectors = min(t->max_copy_sectors, b->max_copy_sectors);
+	t->max_copy_hw_sectors = min(t->max_copy_hw_sectors,
+				     b->max_copy_hw_sectors);
+
 	t->misaligned |= b->misaligned;
 
 	alignment = queue_limit_alignment_offset(b, start);
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 63e481262336..4840e21adefa 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -199,6 +199,37 @@ static ssize_t queue_discard_zeroes_data_show(struct request_queue *q, char *pag
 	return queue_var_show(0, page);
 }
 
+static ssize_t queue_copy_hw_max_show(struct request_queue *q, char *page)
+{
+	return sprintf(page, "%llu\n", (unsigned long long)
+		       q->limits.max_copy_hw_sectors << SECTOR_SHIFT);
+}
+
+static ssize_t queue_copy_max_show(struct request_queue *q, char *page)
+{
+	return sprintf(page, "%llu\n", (unsigned long long)
+		       q->limits.max_copy_sectors << SECTOR_SHIFT);
+}
+
+static ssize_t queue_copy_max_store(struct request_queue *q, const char *page,
+				    size_t count)
+{
+	unsigned long max_copy;
+	ssize_t ret = queue_var_store(&max_copy, page, count);
+
+	if (ret < 0)
+		return ret;
+
+	if (max_copy & (queue_logical_block_size(q) - 1))
+		return -EINVAL;
+
+	max_copy >>= SECTOR_SHIFT;
+	q->limits.max_copy_sectors = min_t(unsigned int, max_copy,
+					   q->limits.max_copy_hw_sectors);
+
+	return count;
+}
+
 static ssize_t queue_write_same_max_show(struct request_queue *q, char *page)
 {
 	return queue_var_show(0, page);
@@ -517,6 +548,9 @@ QUEUE_RO_ENTRY(queue_nr_zones, "nr_zones");
 QUEUE_RO_ENTRY(queue_max_open_zones, "max_open_zones");
 QUEUE_RO_ENTRY(queue_max_active_zones, "max_active_zones");
 
+QUEUE_RO_ENTRY(queue_copy_hw_max, "copy_max_hw_bytes");
+QUEUE_RW_ENTRY(queue_copy_max, "copy_max_bytes");
+
 QUEUE_RW_ENTRY(queue_nomerges, "nomerges");
 QUEUE_RW_ENTRY(queue_rq_affinity, "rq_affinity");
 QUEUE_RW_ENTRY(queue_poll, "io_poll");
@@ -633,6 +667,8 @@ static struct attribute *queue_attrs[] = {
 	&queue_discard_max_entry.attr,
 	&queue_discard_max_hw_entry.attr,
 	&queue_discard_zeroes_data_entry.attr,
+	&queue_copy_hw_max_entry.attr,
+	&queue_copy_max_entry.attr,
 	&queue_write_same_max_entry.attr,
 	&queue_write_zeroes_max_entry.attr,
 	&queue_zone_append_max_entry.attr,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index eef450f25982..7548f1685ee9 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -309,6 +309,9 @@ struct queue_limits {
 	unsigned int		discard_alignment;
 	unsigned int		zone_write_granularity;
 
+	unsigned int		max_copy_hw_sectors;
+	unsigned int		max_copy_sectors;
+
 	unsigned short		max_segments;
 	unsigned short		max_integrity_segments;
 	unsigned short		max_discard_segments;
@@ -893,6 +896,8 @@ extern void blk_queue_chunk_sectors(struct request_queue *, unsigned int);
 extern void blk_queue_max_segments(struct request_queue *, unsigned short);
 extern void blk_queue_max_discard_segments(struct request_queue *,
 		unsigned short);
+extern void blk_queue_max_copy_hw_sectors(struct request_queue *q,
+					  unsigned int max_copy_sectors);
 void blk_queue_max_secure_erase_sectors(struct request_queue *q,
 		unsigned int max_sectors);
 extern void blk_queue_max_segment_size(struct request_queue *, unsigned int);
@@ -1211,6 +1216,14 @@ static inline unsigned int bdev_discard_granularity(struct block_device *bdev)
 	return bdev_get_queue(bdev)->limits.discard_granularity;
 }
 
+/* maximum copy offload length, this is set to 128MB based on current testing */
+#define BLK_COPY_MAX_BYTES		(1 << 27)
+
+static inline unsigned int bdev_max_copy_sectors(struct block_device *bdev)
+{
+	return bdev_get_queue(bdev)->limits.max_copy_sectors;
+}
+
 static inline unsigned int
 bdev_max_secure_erase_sectors(struct block_device *bdev)
 {
-- 
2.35.1.500.gb896f729e2

[PATCH v15 02/12] Add infrastructure for copy offload in block and request layer.

[Nitesh Shetty]

We add two new opcode REQ_OP_COPY_SRC, REQ_OP_COPY_DST.
Since copy is a composite operation involving src and dst sectors/lba,
each needs to be represented by a separate bio to make it compatible
with device mapper.
We expect caller to take a plug and send bio with source information,
followed by bio with destination information.
Once the src bio arrives we form a request and wait for destination
bio. Upon arrival of destination we merge these two bio's and send
corresponding request down to device driver.

Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
---
 block/blk-core.c          |  7 +++++++
 block/blk-merge.c         | 41 +++++++++++++++++++++++++++++++++++++++
 block/blk.h               | 16 +++++++++++++++
 block/elevator.h          |  1 +
 include/linux/bio.h       |  6 +-----
 include/linux/blk_types.h | 10 ++++++++++
 6 files changed, 76 insertions(+), 5 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 9d51e9894ece..33aadafdb7f9 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -121,6 +121,8 @@ static const char *const blk_op_name[] = {
 	REQ_OP_NAME(ZONE_FINISH),
 	REQ_OP_NAME(ZONE_APPEND),
 	REQ_OP_NAME(WRITE_ZEROES),
+	REQ_OP_NAME(COPY_SRC),
+	REQ_OP_NAME(COPY_DST),
 	REQ_OP_NAME(DRV_IN),
 	REQ_OP_NAME(DRV_OUT),
 };
@@ -792,6 +794,11 @@ void submit_bio_noacct(struct bio *bio)
 		if (!q->limits.max_write_zeroes_sectors)
 			goto not_supported;
 		break;
+	case REQ_OP_COPY_SRC:
+	case REQ_OP_COPY_DST:
+		if (!q->limits.max_copy_sectors)
+			goto not_supported;
+		break;
 	default:
 		break;
 	}
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 65e75efa9bd3..bcb55ba48107 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -158,6 +158,20 @@ static struct bio *bio_split_write_zeroes(struct bio *bio,
 	return bio_split(bio, lim->max_write_zeroes_sectors, GFP_NOIO, bs);
 }
 
+static struct bio *bio_split_copy(struct bio *bio,
+				  const struct queue_limits *lim,
+				  unsigned int *nsegs)
+{
+	*nsegs = 1;
+	if (bio_sectors(bio) <= lim->max_copy_sectors)
+		return NULL;
+	/*
+	 * We don't support splitting for a copy bio. End it with EIO if
+	 * splitting is required and return an error pointer.
+	 */
+	return ERR_PTR(-EIO);
+}
+
 /*
  * Return the maximum number of sectors from the start of a bio that may be
  * submitted as a single request to a block device. If enough sectors remain,
@@ -366,6 +380,12 @@ struct bio *__bio_split_to_limits(struct bio *bio,
 	case REQ_OP_WRITE_ZEROES:
 		split = bio_split_write_zeroes(bio, lim, nr_segs, bs);
 		break;
+	case REQ_OP_COPY_SRC:
+	case REQ_OP_COPY_DST:
+		split = bio_split_copy(bio, lim, nr_segs);
+		if (IS_ERR(split))
+			return NULL;
+		break;
 	default:
 		split = bio_split_rw(bio, lim, nr_segs, bs,
 				get_max_io_size(bio, lim) << SECTOR_SHIFT);
@@ -922,6 +942,9 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
 	if (!rq_mergeable(rq) || !bio_mergeable(bio))
 		return false;
 
+	if (blk_copy_offload_mergable(rq, bio))
+		return true;
+
 	if (req_op(rq) != bio_op(bio))
 		return false;
 
@@ -951,6 +974,8 @@ enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
 {
 	if (blk_discard_mergable(rq))
 		return ELEVATOR_DISCARD_MERGE;
+	else if (blk_copy_offload_mergable(rq, bio))
+		return ELEVATOR_COPY_OFFLOAD_MERGE;
 	else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
 		return ELEVATOR_BACK_MERGE;
 	else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
@@ -1053,6 +1078,20 @@ static enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q,
 	return BIO_MERGE_FAILED;
 }
 
+static enum bio_merge_status bio_attempt_copy_offload_merge(struct request *req,
+							    struct bio *bio)
+{
+	if (req->__data_len != bio->bi_iter.bi_size)
+		return BIO_MERGE_FAILED;
+
+	req->biotail->bi_next = bio;
+	req->biotail = bio;
+	req->nr_phys_segments++;
+	req->__data_len += bio->bi_iter.bi_size;
+
+	return BIO_MERGE_OK;
+}
+
 static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q,
 						   struct request *rq,
 						   struct bio *bio,
@@ -1073,6 +1112,8 @@ static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q,
 		break;
 	case ELEVATOR_DISCARD_MERGE:
 		return bio_attempt_discard_merge(q, rq, bio);
+	case ELEVATOR_COPY_OFFLOAD_MERGE:
+		return bio_attempt_copy_offload_merge(rq, bio);
 	default:
 		return BIO_MERGE_NONE;
 	}
diff --git a/block/blk.h b/block/blk.h
index 08a358bc0919..b0c17ad635a5 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -159,6 +159,20 @@ static inline bool blk_discard_mergable(struct request *req)
 	return false;
 }
 
+/*
+ * Copy offload sends a pair of bio with REQ_OP_COPY_SRC and REQ_OP_COPY_DST
+ * operation by taking a plug.
+ * Initially SRC bio is sent which forms a request and
+ * waits for DST bio to arrive. Once DST bio arrives
+ * we merge it and send request down to driver.
+ */
+static inline bool blk_copy_offload_mergable(struct request *req,
+					     struct bio *bio)
+{
+	return (req_op(req) == REQ_OP_COPY_SRC &&
+		bio_op(bio) == REQ_OP_COPY_DST);
+}
+
 static inline unsigned int blk_rq_get_max_segments(struct request *rq)
 {
 	if (req_op(rq) == REQ_OP_DISCARD)
@@ -300,6 +314,8 @@ static inline bool bio_may_exceed_limits(struct bio *bio,
 	case REQ_OP_DISCARD:
 	case REQ_OP_SECURE_ERASE:
 	case REQ_OP_WRITE_ZEROES:
+	case REQ_OP_COPY_SRC:
+	case REQ_OP_COPY_DST:
 		return true; /* non-trivial splitting decisions */
 	default:
 		break;
diff --git a/block/elevator.h b/block/elevator.h
index 7ca3d7b6ed82..eec442bbf384 100644
--- a/block/elevator.h
+++ b/block/elevator.h
@@ -18,6 +18,7 @@ enum elv_merge {
 	ELEVATOR_FRONT_MERGE	= 1,
 	ELEVATOR_BACK_MERGE	= 2,
 	ELEVATOR_DISCARD_MERGE	= 3,
+	ELEVATOR_COPY_OFFLOAD_MERGE	= 4,
 };
 
 struct blk_mq_alloc_data;
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 41d417ee1349..ed746738755a 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -53,11 +53,7 @@ static inline unsigned int bio_max_segs(unsigned int nr_segs)
  */
 static inline bool bio_has_data(struct bio *bio)
 {
-	if (bio &&
-	    bio->bi_iter.bi_size &&
-	    bio_op(bio) != REQ_OP_DISCARD &&
-	    bio_op(bio) != REQ_OP_SECURE_ERASE &&
-	    bio_op(bio) != REQ_OP_WRITE_ZEROES)
+	if (bio && (bio_op(bio) == REQ_OP_READ || bio_op(bio) == REQ_OP_WRITE))
 		return true;
 
 	return false;
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index d5c5e59ddbd2..78624e8f4ab4 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -393,6 +393,10 @@ enum req_op {
 	/* reset all the zone present on the device */
 	REQ_OP_ZONE_RESET_ALL	= (__force blk_opf_t)17,
 
+	/* copy offload dst and src operation */
+	REQ_OP_COPY_SRC		= (__force blk_opf_t)19,
+	REQ_OP_COPY_DST		= (__force blk_opf_t)21,
+
 	/* Driver private requests */
 	REQ_OP_DRV_IN		= (__force blk_opf_t)34,
 	REQ_OP_DRV_OUT		= (__force blk_opf_t)35,
@@ -481,6 +485,12 @@ static inline bool op_is_write(blk_opf_t op)
 	return !!(op & (__force blk_opf_t)1);
 }
 
+static inline bool op_is_copy(blk_opf_t op)
+{
+	return ((op & REQ_OP_MASK) == REQ_OP_COPY_SRC ||
+		(op & REQ_OP_MASK) == REQ_OP_COPY_DST);
+}
+
 /*
  * Check if the bio or request is one that needs special treatment in the
  * flush state machine.
-- 
2.35.1.500.gb896f729e2

[PATCH v15 03/12] block: add copy offload support

[Nitesh Shetty]

Introduce blkdev_copy_offload to perform copy offload.
Issue REQ_OP_COPY_SRC with source info along with taking a plug.
This flows till request layer and waits for dst bio to arrive.
Issue REQ_OP_COPY_DST with destination info and this bio reaches request
layer and merges with src request.
For any reason, if a request comes to the driver with only one of src/dst
bio, we fail the copy offload.

Larger copy will be divided, based on max_copy_sectors limit.

Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
---
 block/blk-lib.c        | 202 +++++++++++++++++++++++++++++++++++++++++
 include/linux/blkdev.h |   4 +
 2 files changed, 206 insertions(+)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index e59c3069e835..d22e1e7417ca 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -10,6 +10,22 @@
 
 #include "blk.h"
 
+/* Keeps track of all outstanding copy IO */
+struct blkdev_copy_io {
+	atomic_t refcount;
+	ssize_t copied;
+	int status;
+	struct task_struct *waiter;
+	void (*endio)(void *private, int status, ssize_t copied);
+	void *private;
+};
+
+/* Keeps track of single outstanding copy offload IO */
+struct blkdev_copy_offload_io {
+	struct blkdev_copy_io *cio;
+	loff_t offset;
+};
+
 static sector_t bio_discard_limit(struct block_device *bdev, sector_t sector)
 {
 	unsigned int discard_granularity = bdev_discard_granularity(bdev);
@@ -115,6 +131,192 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 }
 EXPORT_SYMBOL(blkdev_issue_discard);
 
+static inline ssize_t blkdev_copy_sanity_check(struct block_device *bdev_in,
+					       loff_t pos_in,
+					       struct block_device *bdev_out,
+					       loff_t pos_out, size_t len)
+{
+	unsigned int align = max(bdev_logical_block_size(bdev_out),
+				 bdev_logical_block_size(bdev_in)) - 1;
+
+	if ((pos_in & align) || (pos_out & align) || (len & align) || !len ||
+	    len >= BLK_COPY_MAX_BYTES)
+		return -EINVAL;
+
+	return 0;
+}
+
+static inline void blkdev_copy_endio(struct blkdev_copy_io *cio)
+{
+	if (cio->endio) {
+		cio->endio(cio->private, cio->status, cio->copied);
+		kfree(cio);
+	} else {
+		struct task_struct *waiter = cio->waiter;
+
+		WRITE_ONCE(cio->waiter, NULL);
+		blk_wake_io_task(waiter);
+	}
+}
+
+/*
+ * This must only be called once all bios have been issued so that the refcount
+ * can only decrease. This just waits for all bios to complete.
+ * Returns the length of bytes copied or error
+ */
+static ssize_t blkdev_copy_wait_io_completion(struct blkdev_copy_io *cio)
+{
+	ssize_t ret;
+
+	for (;;) {
+		__set_current_state(TASK_UNINTERRUPTIBLE);
+		if (!READ_ONCE(cio->waiter))
+			break;
+		blk_io_schedule();
+	}
+	__set_current_state(TASK_RUNNING);
+	ret = cio->copied;
+	kfree(cio);
+
+	return ret;
+}
+
+static void blkdev_copy_offload_dst_endio(struct bio *bio)
+{
+	struct blkdev_copy_offload_io *offload_io = bio->bi_private;
+	struct blkdev_copy_io *cio = offload_io->cio;
+
+	if (bio->bi_status) {
+		cio->copied = min_t(ssize_t, offload_io->offset, cio->copied);
+		if (!cio->status)
+			cio->status = blk_status_to_errno(bio->bi_status);
+	}
+	bio_put(bio);
+
+	if (atomic_dec_and_test(&cio->refcount))
+		blkdev_copy_endio(cio);
+}
+
+/*
+ * @bdev:	block device
+ * @pos_in:	source offset
+ * @pos_out:	destination offset
+ * @len:	length in bytes to be copied
+ * @endio:	endio function to be called on completion of copy operation,
+ *		for synchronous operation this should be NULL
+ * @private:	endio function will be called with this private data,
+ *		for synchronous operation this should be NULL
+ * @gfp_mask:	memory allocation flags (for bio_alloc)
+ *
+ * For synchronous operation returns the length of bytes copied or error
+ * For asynchronous operation returns -EIOCBQUEUED or error
+ *
+ * Description:
+ *	Copy source offset to destination offset within block device, using
+ *	device's native copy offload feature. This function can fail, and
+ *	in that case the caller can fallback to emulation.
+ *	We perform copy operation using 2 bio's.
+ *	1. We take a plug and send a REQ_OP_COPY_SRC bio along with source
+ *	sector and length. Once this bio reaches request layer, we form a
+ *	request and wait for dst bio to arrive.
+ *	2. We issue REQ_OP_COPY_DST bio along with destination sector, length.
+ *	Once this bio reaches request layer and find a request with previously
+ *	sent source info we merge the destination bio and return.
+ *	3. Release the plug and request is sent to driver
+ *	This design works only for drivers with request queue.
+ */
+ssize_t blkdev_copy_offload(struct block_device *bdev, loff_t pos_in,
+			    loff_t pos_out, size_t len,
+			    void (*endio)(void *, int, ssize_t),
+			    void *private, gfp_t gfp)
+{
+	struct blkdev_copy_io *cio;
+	struct blkdev_copy_offload_io *offload_io;
+	struct bio *src_bio, *dst_bio;
+	ssize_t rem, chunk, ret;
+	ssize_t max_copy_bytes = bdev_max_copy_sectors(bdev) << SECTOR_SHIFT;
+	struct blk_plug plug;
+
+	if (!max_copy_bytes)
+		return -EINVAL;
+
+	ret = blkdev_copy_sanity_check(bdev, pos_in, bdev, pos_out, len);
+	if (ret)
+		return ret;
+
+	cio = kzalloc(sizeof(*cio), GFP_KERNEL);
+	if (!cio)
+		return -ENOMEM;
+	atomic_set(&cio->refcount, 1);
+	cio->waiter = current;
+	cio->endio = endio;
+	cio->private = private;
+
+	/*
+	 * If there is a error, copied will be set to least successfully
+	 * completed copied length
+	 */
+	cio->copied = len;
+	for (rem = len; rem > 0; rem -= chunk) {
+		chunk = min(rem, max_copy_bytes);
+
+		offload_io = kzalloc(sizeof(*offload_io), GFP_KERNEL);
+		if (!offload_io)
+			goto err_free_cio;
+		offload_io->cio = cio;
+		/*
+		 * For partial completion, we use offload_io->offset to truncate
+		 * successful copy length
+		 */
+		offload_io->offset = len - rem;
+
+		src_bio = bio_alloc(bdev, 0, REQ_OP_COPY_SRC, gfp);
+		if (!src_bio)
+			goto err_free_offload_io;
+		src_bio->bi_iter.bi_size = chunk;
+		src_bio->bi_iter.bi_sector = pos_in >> SECTOR_SHIFT;
+
+		blk_start_plug(&plug);
+		dst_bio = blk_next_bio(src_bio, bdev, 0, REQ_OP_COPY_DST, gfp);
+		if (!dst_bio)
+			goto err_free_src_bio;
+		dst_bio->bi_iter.bi_size = chunk;
+		dst_bio->bi_iter.bi_sector = pos_out >> SECTOR_SHIFT;
+		dst_bio->bi_end_io = blkdev_copy_offload_dst_endio;
+		dst_bio->bi_private = offload_io;
+
+		atomic_inc(&cio->refcount);
+		submit_bio(dst_bio);
+		blk_finish_plug(&plug);
+		pos_in += chunk;
+		pos_out += chunk;
+	}
+
+	if (atomic_dec_and_test(&cio->refcount))
+		blkdev_copy_endio(cio);
+	if (cio->endio)
+		return -EIOCBQUEUED;
+
+	return blkdev_copy_wait_io_completion(cio);
+
+err_free_src_bio:
+	bio_put(src_bio);
+err_free_offload_io:
+	kfree(offload_io);
+err_free_cio:
+	cio->copied = min_t(ssize_t, cio->copied, (len - rem));
+	cio->status = -ENOMEM;
+	if (rem == len) {
+		kfree(cio);
+		return cio->status;
+	}
+	if (cio->endio)
+		return cio->status;
+
+	return blkdev_copy_wait_io_completion(cio);
+}
+EXPORT_SYMBOL_GPL(blkdev_copy_offload);
+
 static int __blkdev_issue_write_zeroes(struct block_device *bdev,
 		sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
 		struct bio **biop, unsigned flags)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 7548f1685ee9..5405499bcf22 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1042,6 +1042,10 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 		sector_t nr_sects, gfp_t gfp_mask, struct bio **biop);
 int blkdev_issue_secure_erase(struct block_device *bdev, sector_t sector,
 		sector_t nr_sects, gfp_t gfp);
+ssize_t blkdev_copy_offload(struct block_device *bdev, loff_t pos_in,
+			    loff_t pos_out, size_t len,
+			    void (*endio)(void *, int, ssize_t),
+			    void *private, gfp_t gfp_mask);
 
 #define BLKDEV_ZERO_NOUNMAP	(1 << 0)  /* do not free blocks */
 #define BLKDEV_ZERO_NOFALLBACK	(1 << 1)  /* don't write explicit zeroes */
-- 
2.35.1.500.gb896f729e2

[PATCH v15 04/12] block: add emulation for copy

[Nitesh Shetty]

For the devices which does not support copy, copy emulation is added.
It is required for in-kernel users like fabrics, where file descriptor is
not available and hence they can't use copy_file_range.
Copy-emulation is implemented by reading from source into memory and
writing to the corresponding destination.
Also emulation can be used, if copy offload fails or partially completes.
At present in kernel user of emulation is NVMe fabrics.

Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
Signed-off-by: Vincent Fu <vincent.fu@samsung.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
---
 block/blk-lib.c        | 223 +++++++++++++++++++++++++++++++++++++++++
 include/linux/blkdev.h |   4 +
 2 files changed, 227 insertions(+)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index d22e1e7417ca..b18871ea7281 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -26,6 +26,20 @@ struct blkdev_copy_offload_io {
 	loff_t offset;
 };
 
+/* Keeps track of single outstanding copy emulation IO */
+struct blkdev_copy_emulation_io {
+	struct blkdev_copy_io *cio;
+	struct work_struct emulation_work;
+	void *buf;
+	ssize_t buf_len;
+	loff_t pos_in;
+	loff_t pos_out;
+	ssize_t len;
+	struct block_device *bdev_in;
+	struct block_device *bdev_out;
+	gfp_t gfp;
+};
+
 static sector_t bio_discard_limit(struct block_device *bdev, sector_t sector)
 {
 	unsigned int discard_granularity = bdev_discard_granularity(bdev);
@@ -317,6 +331,215 @@ ssize_t blkdev_copy_offload(struct block_device *bdev, loff_t pos_in,
 }
 EXPORT_SYMBOL_GPL(blkdev_copy_offload);
 
+static void *blkdev_copy_alloc_buf(ssize_t req_size, ssize_t *alloc_size,
+				   gfp_t gfp)
+{
+	int min_size = PAGE_SIZE;
+	char *buf;
+
+	while (req_size >= min_size) {
+		buf = kvmalloc(req_size, gfp);
+		if (buf) {
+			*alloc_size = req_size;
+			return buf;
+		}
+		req_size >>= 1;
+	}
+
+	return NULL;
+}
+
+static struct bio *bio_map_buf(void *data, unsigned int len, gfp_t gfp)
+{
+	unsigned long kaddr = (unsigned long)data;
+	unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	unsigned long start = kaddr >> PAGE_SHIFT;
+	const int nr_pages = end - start;
+	bool is_vmalloc = is_vmalloc_addr(data);
+	struct page *page;
+	int offset, i;
+	struct bio *bio;
+
+	bio = bio_kmalloc(nr_pages, gfp);
+	if (!bio)
+		return ERR_PTR(-ENOMEM);
+	bio_init(bio, NULL, bio->bi_inline_vecs, nr_pages, 0);
+
+	if (is_vmalloc) {
+		flush_kernel_vmap_range(data, len);
+		bio->bi_private = data;
+	}
+
+	offset = offset_in_page(kaddr);
+	for (i = 0; i < nr_pages; i++) {
+		unsigned int bytes = PAGE_SIZE - offset;
+
+		if (len <= 0)
+			break;
+
+		if (bytes > len)
+			bytes = len;
+
+		if (!is_vmalloc)
+			page = virt_to_page(data);
+		else
+			page = vmalloc_to_page(data);
+		if (bio_add_page(bio, page, bytes, offset) < bytes) {
+			/* we don't support partial mappings */
+			bio_uninit(bio);
+			kfree(bio);
+			return ERR_PTR(-EINVAL);
+		}
+
+		data += bytes;
+		len -= bytes;
+		offset = 0;
+	}
+
+	return bio;
+}
+
+static void blkdev_copy_emulation_work(struct work_struct *work)
+{
+	struct blkdev_copy_emulation_io *emulation_io = container_of(work,
+			struct blkdev_copy_emulation_io, emulation_work);
+	struct blkdev_copy_io *cio = emulation_io->cio;
+	struct bio *read_bio, *write_bio;
+	loff_t pos_in = emulation_io->pos_in, pos_out = emulation_io->pos_out;
+	ssize_t rem, chunk;
+	int ret = 0;
+
+	for (rem = emulation_io->len; rem > 0; rem -= chunk) {
+		chunk = min_t(int, emulation_io->buf_len, rem);
+
+		read_bio = bio_map_buf(emulation_io->buf,
+				       emulation_io->buf_len,
+				       emulation_io->gfp);
+		if (IS_ERR(read_bio)) {
+			ret = PTR_ERR(read_bio);
+			break;
+		}
+		read_bio->bi_opf = REQ_OP_READ | REQ_SYNC;
+		bio_set_dev(read_bio, emulation_io->bdev_in);
+		read_bio->bi_iter.bi_sector = pos_in >> SECTOR_SHIFT;
+		read_bio->bi_iter.bi_size = chunk;
+		ret = submit_bio_wait(read_bio);
+		kfree(read_bio);
+		if (ret)
+			break;
+
+		write_bio = bio_map_buf(emulation_io->buf,
+					emulation_io->buf_len,
+					emulation_io->gfp);
+		if (IS_ERR(write_bio)) {
+			ret = PTR_ERR(write_bio);
+			break;
+		}
+		write_bio->bi_opf = REQ_OP_WRITE | REQ_SYNC;
+		bio_set_dev(write_bio, emulation_io->bdev_out);
+		write_bio->bi_iter.bi_sector = pos_out >> SECTOR_SHIFT;
+		write_bio->bi_iter.bi_size = chunk;
+		ret = submit_bio_wait(write_bio);
+		kfree(write_bio);
+		if (ret)
+			break;
+
+		pos_in += chunk;
+		pos_out += chunk;
+	}
+	cio->status = ret;
+	kvfree(emulation_io->buf);
+	kfree(emulation_io);
+	blkdev_copy_endio(cio);
+}
+
+static inline ssize_t queue_max_hw_bytes(struct request_queue *q)
+{
+	return min_t(ssize_t, queue_max_hw_sectors(q) << SECTOR_SHIFT,
+		     queue_max_segments(q) << PAGE_SHIFT);
+}
+/*
+ * @bdev_in:	source block device
+ * @pos_in:	source offset
+ * @bdev_out:	destination block device
+ * @pos_out:	destination offset
+ * @len:	length in bytes to be copied
+ * @endio:	endio function to be called on completion of copy operation,
+ *		for synchronous operation this should be NULL
+ * @private:	endio function will be called with this private data,
+ *		for synchronous operation this should be NULL
+ * @gfp_mask:	memory allocation flags (for bio_alloc)
+ *
+ * For synchronous operation returns the length of bytes copied or error
+ * For asynchronous operation returns -EIOCBQUEUED or error
+ *
+ * Description:
+ *	If native copy offload feature is absent, caller can use this function
+ *	as fallback to perform copy.
+ *	We store information required to perform the copy along with temporary
+ *	buffer allocation. We async punt copy emulation to a worker. And worker
+ *	performs copy in 2 steps.
+ *	1. Read data from source to temporary buffer
+ *	2. Write data to destination from temporary buffer
+ */
+ssize_t blkdev_copy_emulation(struct block_device *bdev_in, loff_t pos_in,
+			      struct block_device *bdev_out, loff_t pos_out,
+			      size_t len, void (*endio)(void *, int, ssize_t),
+			      void *private, gfp_t gfp)
+{
+	struct request_queue *in = bdev_get_queue(bdev_in);
+	struct request_queue *out = bdev_get_queue(bdev_out);
+	struct blkdev_copy_emulation_io *emulation_io;
+	struct blkdev_copy_io *cio;
+	ssize_t ret;
+	size_t max_hw_bytes = min(queue_max_hw_bytes(in),
+				  queue_max_hw_bytes(out));
+
+	ret = blkdev_copy_sanity_check(bdev_in, pos_in, bdev_out, pos_out, len);
+	if (ret)
+		return ret;
+
+	cio = kzalloc(sizeof(*cio), GFP_KERNEL);
+	if (!cio)
+		return -ENOMEM;
+
+	cio->waiter = current;
+	cio->copied = len;
+	cio->endio = endio;
+	cio->private = private;
+
+	emulation_io = kzalloc(sizeof(*emulation_io), gfp);
+	if (!emulation_io)
+		goto err_free_cio;
+	emulation_io->cio = cio;
+	INIT_WORK(&emulation_io->emulation_work, blkdev_copy_emulation_work);
+	emulation_io->pos_in = pos_in;
+	emulation_io->pos_out = pos_out;
+	emulation_io->len = len;
+	emulation_io->bdev_in = bdev_in;
+	emulation_io->bdev_out = bdev_out;
+	emulation_io->gfp = gfp;
+
+	emulation_io->buf = blkdev_copy_alloc_buf(min(max_hw_bytes, len),
+						  &emulation_io->buf_len, gfp);
+	if (!emulation_io->buf)
+		goto err_free_emulation_io;
+
+	schedule_work(&emulation_io->emulation_work);
+
+	if (cio->endio)
+		return -EIOCBQUEUED;
+
+	return blkdev_copy_wait_io_completion(cio);
+
+err_free_emulation_io:
+	kfree(emulation_io);
+err_free_cio:
+	kfree(cio);
+	return -ENOMEM;
+}
+EXPORT_SYMBOL_GPL(blkdev_copy_emulation);
+
 static int __blkdev_issue_write_zeroes(struct block_device *bdev,
 		sector_t sector, sector_t nr_sects, gfp_t gfp_mask,
 		struct bio **biop, unsigned flags)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 5405499bcf22..e0a832a1c3a7 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1046,6 +1046,10 @@ ssize_t blkdev_copy_offload(struct block_device *bdev, loff_t pos_in,
 			    loff_t pos_out, size_t len,
 			    void (*endio)(void *, int, ssize_t),
 			    void *private, gfp_t gfp_mask);
+ssize_t blkdev_copy_emulation(struct block_device *bdev_in, loff_t pos_in,
+			      struct block_device *bdev_out, loff_t pos_out,
+			      size_t len, void (*endio)(void *, int, ssize_t),
+			      void *private, gfp_t gfp);
 
 #define BLKDEV_ZERO_NOUNMAP	(1 << 0)  /* do not free blocks */
 #define BLKDEV_ZERO_NOFALLBACK	(1 << 1)  /* don't write explicit zeroes */
-- 
2.35.1.500.gb896f729e2

[PATCH v15 05/12] fs/read_write: Enable copy_file_range for block device.

[Nitesh Shetty]

From: Anuj Gupta <anuj20.g@samsung.com>

This is a prep patch. Allow copy_file_range to work for block devices.
Relaxing generic_copy_file_checks allows us to reuse the existing infra,
instead of adding a new user interface for block copy offload.
Change generic_copy_file_checks to use ->f_mapping->host for both inode_in
and inode_out. Allow block device in generic_file_rw_checks.

Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
---
 fs/read_write.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 4771701c896b..f0f52bf48f57 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1405,8 +1405,8 @@ static int generic_copy_file_checks(struct file *file_in, loff_t pos_in,
 				    struct file *file_out, loff_t pos_out,
 				    size_t *req_count, unsigned int flags)
 {
-	struct inode *inode_in = file_inode(file_in);
-	struct inode *inode_out = file_inode(file_out);
+	struct inode *inode_in = file_in->f_mapping->host;
+	struct inode *inode_out = file_out->f_mapping->host;
 	uint64_t count = *req_count;
 	loff_t size_in;
 	int ret;
@@ -1708,7 +1708,9 @@ int generic_file_rw_checks(struct file *file_in, struct file *file_out)
 	/* Don't copy dirs, pipes, sockets... */
 	if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->i_mode))
 		return -EISDIR;
-	if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
+	if (!S_ISREG(inode_in->i_mode) && !S_ISBLK(inode_in->i_mode))
+		return -EINVAL;
+	if ((inode_in->i_mode & S_IFMT) != (inode_out->i_mode & S_IFMT))
 		return -EINVAL;
 
 	if (!(file_in->f_mode & FMODE_READ) ||
-- 
2.35.1.500.gb896f729e2

[PATCH v15 06/12] fs, block: copy_file_range for def_blk_ops for direct block device

[Nitesh Shetty]

For direct block device opened with O_DIRECT, use copy_file_range to
issue device copy offload, and fallback to generic_copy_file_range incase
device copy offload capability is absent or the device files are not open
with O_DIRECT.

Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
---
 block/fops.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/block/fops.c b/block/fops.c
index a24a624d3bf7..2d96459f3277 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -739,6 +739,30 @@ static ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	return ret;
 }
 
+static ssize_t blkdev_copy_file_range(struct file *file_in, loff_t pos_in,
+				      struct file *file_out, loff_t pos_out,
+				      size_t len, unsigned int flags)
+{
+	struct block_device *in_bdev = I_BDEV(bdev_file_inode(file_in));
+	struct block_device *out_bdev = I_BDEV(bdev_file_inode(file_out));
+	ssize_t copied = 0;
+
+	if ((in_bdev == out_bdev) && bdev_max_copy_sectors(in_bdev) &&
+	    (file_in->f_iocb_flags & IOCB_DIRECT) &&
+	    (file_out->f_iocb_flags & IOCB_DIRECT)) {
+		copied = blkdev_copy_offload(in_bdev, pos_in, pos_out, len,
+					     NULL, NULL, GFP_KERNEL);
+		if (copied < 0)
+			copied = 0;
+	}
+	if (copied != len)
+		copied = generic_copy_file_range(file_in, pos_in + copied,
+						 file_out, pos_out + copied,
+						 len - copied, flags);
+
+	return copied;
+}
+
 #define	BLKDEV_FALLOC_FL_SUPPORTED					\
 		(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |		\
 		 FALLOC_FL_ZERO_RANGE | FALLOC_FL_NO_HIDE_STALE)
@@ -832,6 +856,7 @@ const struct file_operations def_blk_fops = {
 	.splice_read	= filemap_splice_read,
 	.splice_write	= iter_file_splice_write,
 	.fallocate	= blkdev_fallocate,
+	.copy_file_range = blkdev_copy_file_range,
 };
 
 static __init int blkdev_init(void)
-- 
2.35.1.500.gb896f729e2

[PATCH v15 07/12] nvme: add copy offload support

[Nitesh Shetty]

Current design only supports single source range.
We receive a request with REQ_OP_COPY_SRC.
Parse this request which consists of src(1st) and dst(2nd) bios.
Form a copy command (TP 4065)

trace event support for nvme_copy_cmd.
Set the device copy limits to queue limits.

Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
Signed-off-by: Javier González <javier.gonz@samsung.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
---
 drivers/nvme/host/constants.c |  1 +
 drivers/nvme/host/core.c      | 79 +++++++++++++++++++++++++++++++++++
 drivers/nvme/host/trace.c     | 19 +++++++++
 include/linux/blkdev.h        |  1 +
 include/linux/nvme.h          | 43 +++++++++++++++++--
 5 files changed, 140 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/host/constants.c b/drivers/nvme/host/constants.c
index 20f46c230885..2f504a2b1fe8 100644
--- a/drivers/nvme/host/constants.c
+++ b/drivers/nvme/host/constants.c
@@ -19,6 +19,7 @@ static const char * const nvme_ops[] = {
 	[nvme_cmd_resv_report] = "Reservation Report",
 	[nvme_cmd_resv_acquire] = "Reservation Acquire",
 	[nvme_cmd_resv_release] = "Reservation Release",
+	[nvme_cmd_copy] = "Copy Offload",
 	[nvme_cmd_zone_mgmt_send] = "Zone Management Send",
 	[nvme_cmd_zone_mgmt_recv] = "Zone Management Receive",
 	[nvme_cmd_zone_append] = "Zone Append",
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index f3a01b79148c..ca47af74afcc 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -763,6 +763,63 @@ static inline void nvme_setup_flush(struct nvme_ns *ns,
 	cmnd->common.nsid = cpu_to_le32(ns->head->ns_id);
 }
 
+static inline blk_status_t nvme_setup_copy_offload(struct nvme_ns *ns,
+						   struct request *req,
+						   struct nvme_command *cmnd)
+{
+	struct nvme_copy_range *range = NULL;
+	struct bio *bio;
+	u64 dst_lba = 0, src_lba, n_lba;
+	u16 nr_range = 1, control = 0, seg = 1;
+
+	if (blk_rq_nr_phys_segments(req) != BLK_COPY_MAX_SEGMENTS)
+		return BLK_STS_IOERR;
+
+	/*
+	 * First bio contains information about source and last bio contains
+	 * information about destination.
+	 */
+	__rq_for_each_bio(bio, req) {
+		if (seg == blk_rq_nr_phys_segments(req)) {
+			dst_lba = nvme_sect_to_lba(ns, bio->bi_iter.bi_sector);
+			if (n_lba != bio->bi_iter.bi_size >> ns->lba_shift)
+				return BLK_STS_IOERR;
+		} else {
+			src_lba = nvme_sect_to_lba(ns, bio->bi_iter.bi_sector);
+			n_lba = bio->bi_iter.bi_size >> ns->lba_shift;
+		}
+		seg++;
+	}
+
+	if (req->cmd_flags & REQ_FUA)
+		control |= NVME_RW_FUA;
+
+	if (req->cmd_flags & REQ_FAILFAST_DEV)
+		control |= NVME_RW_LR;
+
+	memset(cmnd, 0, sizeof(*cmnd));
+	cmnd->copy.opcode = nvme_cmd_copy;
+	cmnd->copy.nsid = cpu_to_le32(ns->head->ns_id);
+	cmnd->copy.control = cpu_to_le16(control);
+	cmnd->copy.sdlba = cpu_to_le64(dst_lba);
+	cmnd->copy.nr_range = 0;
+
+	range = kmalloc_array(nr_range, sizeof(*range),
+			      GFP_ATOMIC | __GFP_NOWARN);
+	if (!range)
+		return BLK_STS_RESOURCE;
+
+	range[0].slba = cpu_to_le64(src_lba);
+	range[0].nlb = cpu_to_le16(n_lba - 1);
+
+	req->special_vec.bv_page = virt_to_page(range);
+	req->special_vec.bv_offset = offset_in_page(range);
+	req->special_vec.bv_len = sizeof(*range) * nr_range;
+	req->rq_flags |= RQF_SPECIAL_PAYLOAD;
+
+	return BLK_STS_OK;
+}
+
 static blk_status_t nvme_setup_discard(struct nvme_ns *ns, struct request *req,
 		struct nvme_command *cmnd)
 {
@@ -1005,6 +1062,11 @@ blk_status_t nvme_setup_cmd(struct nvme_ns *ns, struct request *req)
 	case REQ_OP_ZONE_APPEND:
 		ret = nvme_setup_rw(ns, req, cmd, nvme_cmd_zone_append);
 		break;
+	case REQ_OP_COPY_SRC:
+		ret = nvme_setup_copy_offload(ns, req, cmd);
+		break;
+	case REQ_OP_COPY_DST:
+		return BLK_STS_IOERR;
 	default:
 		WARN_ON_ONCE(1);
 		return BLK_STS_IOERR;
@@ -1745,6 +1807,21 @@ static void nvme_config_discard(struct gendisk *disk, struct nvme_ns *ns)
 		blk_queue_max_write_zeroes_sectors(queue, UINT_MAX);
 }
 
+static void nvme_config_copy(struct gendisk *disk, struct nvme_ns *ns,
+		struct nvme_id_ns *id)
+{
+	struct nvme_ctrl *ctrl = ns->ctrl;
+	struct request_queue *q = disk->queue;
+
+	if (!(ctrl->oncs & NVME_CTRL_ONCS_COPY)) {
+		blk_queue_max_copy_hw_sectors(q, 0);
+		return;
+	}
+
+	blk_queue_max_copy_hw_sectors(q, nvme_lba_to_sect(ns,
+				      le16_to_cpu(id->mssrl)));
+}
+
 static bool nvme_ns_ids_equal(struct nvme_ns_ids *a, struct nvme_ns_ids *b)
 {
 	return uuid_equal(&a->uuid, &b->uuid) &&
@@ -1944,6 +2021,7 @@ static void nvme_update_disk_info(struct gendisk *disk,
 	set_capacity_and_notify(disk, capacity);
 
 	nvme_config_discard(disk, ns);
+	nvme_config_copy(disk, ns, id);
 	blk_queue_max_write_zeroes_sectors(disk->queue,
 					   ns->ctrl->max_zeroes_sectors);
 }
@@ -4638,6 +4716,7 @@ static inline void _nvme_check_size(void)
 	BUILD_BUG_ON(sizeof(struct nvme_download_firmware) != 64);
 	BUILD_BUG_ON(sizeof(struct nvme_format_cmd) != 64);
 	BUILD_BUG_ON(sizeof(struct nvme_dsm_cmd) != 64);
+	BUILD_BUG_ON(sizeof(struct nvme_copy_command) != 64);
 	BUILD_BUG_ON(sizeof(struct nvme_write_zeroes_cmd) != 64);
 	BUILD_BUG_ON(sizeof(struct nvme_abort_cmd) != 64);
 	BUILD_BUG_ON(sizeof(struct nvme_get_log_page_command) != 64);
diff --git a/drivers/nvme/host/trace.c b/drivers/nvme/host/trace.c
index 1c36fcedea20..82c6aef77c31 100644
--- a/drivers/nvme/host/trace.c
+++ b/drivers/nvme/host/trace.c
@@ -150,6 +150,23 @@ static const char *nvme_trace_read_write(struct trace_seq *p, u8 *cdw10)
 	return ret;
 }
 
+static const char *nvme_trace_copy(struct trace_seq *p, u8 *cdw10)
+{
+	const char *ret = trace_seq_buffer_ptr(p);
+	u64 sdlba = get_unaligned_le64(cdw10);
+	u8 nr_range = get_unaligned_le16(cdw10 + 8);
+	u16 control = get_unaligned_le16(cdw10 + 10);
+	u32 dsmgmt = get_unaligned_le32(cdw10 + 12);
+	u32 reftag = get_unaligned_le32(cdw10 + 16);
+
+	trace_seq_printf(p,
+		"sdlba=%llu, nr_range=%u, ctrl=0x%x, dsmgmt=%u, reftag=%u",
+		sdlba, nr_range, control, dsmgmt, reftag);
+	trace_seq_putc(p, 0);
+
+	return ret;
+}
+
 static const char *nvme_trace_dsm(struct trace_seq *p, u8 *cdw10)
 {
 	const char *ret = trace_seq_buffer_ptr(p);
@@ -243,6 +260,8 @@ const char *nvme_trace_parse_nvm_cmd(struct trace_seq *p,
 		return nvme_trace_zone_mgmt_send(p, cdw10);
 	case nvme_cmd_zone_mgmt_recv:
 		return nvme_trace_zone_mgmt_recv(p, cdw10);
+	case nvme_cmd_copy:
+		return nvme_trace_copy(p, cdw10);
 	default:
 		return nvme_trace_common(p, cdw10);
 	}
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index e0a832a1c3a7..ce2009b693c8 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1226,6 +1226,7 @@ static inline unsigned int bdev_discard_granularity(struct block_device *bdev)
 
 /* maximum copy offload length, this is set to 128MB based on current testing */
 #define BLK_COPY_MAX_BYTES		(1 << 27)
+#define BLK_COPY_MAX_SEGMENTS		2
 
 static inline unsigned int bdev_max_copy_sectors(struct block_device *bdev)
 {
diff --git a/include/linux/nvme.h b/include/linux/nvme.h
index 26dd3f859d9d..7744538c4ca4 100644
--- a/include/linux/nvme.h
+++ b/include/linux/nvme.h
@@ -337,7 +337,7 @@ struct nvme_id_ctrl {
 	__u8			nvscc;
 	__u8			nwpc;
 	__le16			acwu;
-	__u8			rsvd534[2];
+	__le16			ocfs;
 	__le32			sgls;
 	__le32			mnan;
 	__u8			rsvd544[224];
@@ -365,6 +365,7 @@ enum {
 	NVME_CTRL_ONCS_WRITE_ZEROES		= 1 << 3,
 	NVME_CTRL_ONCS_RESERVATIONS		= 1 << 5,
 	NVME_CTRL_ONCS_TIMESTAMP		= 1 << 6,
+	NVME_CTRL_ONCS_COPY			= 1 << 8,
 	NVME_CTRL_VWC_PRESENT			= 1 << 0,
 	NVME_CTRL_OACS_SEC_SUPP                 = 1 << 0,
 	NVME_CTRL_OACS_NS_MNGT_SUPP		= 1 << 3,
@@ -414,7 +415,10 @@ struct nvme_id_ns {
 	__le16			npdg;
 	__le16			npda;
 	__le16			nows;
-	__u8			rsvd74[18];
+	__le16			mssrl;
+	__le32			mcl;
+	__u8			msrc;
+	__u8			rsvd91[11];
 	__le32			anagrpid;
 	__u8			rsvd96[3];
 	__u8			nsattr;
@@ -831,6 +835,7 @@ enum nvme_opcode {
 	nvme_cmd_resv_report	= 0x0e,
 	nvme_cmd_resv_acquire	= 0x11,
 	nvme_cmd_resv_release	= 0x15,
+	nvme_cmd_copy		= 0x19,
 	nvme_cmd_zone_mgmt_send	= 0x79,
 	nvme_cmd_zone_mgmt_recv	= 0x7a,
 	nvme_cmd_zone_append	= 0x7d,
@@ -854,7 +859,8 @@ enum nvme_opcode {
 		nvme_opcode_name(nvme_cmd_resv_release),	\
 		nvme_opcode_name(nvme_cmd_zone_mgmt_send),	\
 		nvme_opcode_name(nvme_cmd_zone_mgmt_recv),	\
-		nvme_opcode_name(nvme_cmd_zone_append))
+		nvme_opcode_name(nvme_cmd_zone_append),		\
+		nvme_opcode_name(nvme_cmd_copy))
 
 
 
@@ -1031,6 +1037,36 @@ struct nvme_dsm_range {
 	__le64			slba;
 };
 
+struct nvme_copy_command {
+	__u8			opcode;
+	__u8			flags;
+	__u16			command_id;
+	__le32			nsid;
+	__u64			rsvd2;
+	__le64			metadata;
+	union nvme_data_ptr	dptr;
+	__le64			sdlba;
+	__u8			nr_range;
+	__u8			rsvd12;
+	__le16			control;
+	__le16			rsvd13;
+	__le16			dspec;
+	__le32			ilbrt;
+	__le16			lbat;
+	__le16			lbatm;
+};
+
+struct nvme_copy_range {
+	__le64			rsvd0;
+	__le64			slba;
+	__le16			nlb;
+	__le16			rsvd18;
+	__le32			rsvd20;
+	__le32			eilbrt;
+	__le16			elbat;
+	__le16			elbatm;
+};
+
 struct nvme_write_zeroes_cmd {
 	__u8			opcode;
 	__u8			flags;
@@ -1792,6 +1828,7 @@ struct nvme_command {
 		struct nvme_download_firmware dlfw;
 		struct nvme_format_cmd format;
 		struct nvme_dsm_cmd dsm;
+		struct nvme_copy_command copy;
 		struct nvme_write_zeroes_cmd write_zeroes;
 		struct nvme_zone_mgmt_send_cmd zms;
 		struct nvme_zone_mgmt_recv_cmd zmr;
-- 
2.35.1.500.gb896f729e2

[PATCH v15 08/12] nvmet: add copy command support for bdev and file ns

[Nitesh Shetty]

Add support for handling nvme_cmd_copy command on target.

For bdev-ns if backing device supports copy offload we call device copy
offload (blkdev_copy_offload).
In case of partial completion from above or absence of device copy offload
capability, we fallback to copy emulation (blkdev_copy_emulation)

For file-ns we call vfs_copy_file_range to service our request.

Currently target always shows copy capability by setting
NVME_CTRL_ONCS_COPY in controller ONCS.

loop target has copy support, which can be used to test copy offload.
trace event support for nvme_cmd_copy.

Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
---
 drivers/nvme/target/admin-cmd.c   |  9 ++-
 drivers/nvme/target/io-cmd-bdev.c | 97 +++++++++++++++++++++++++++++++
 drivers/nvme/target/io-cmd-file.c | 50 ++++++++++++++++
 drivers/nvme/target/nvmet.h       |  4 ++
 drivers/nvme/target/trace.c       | 19 ++++++
 5 files changed, 177 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
index 39cb570f833d..4e1a6ca09937 100644
--- a/drivers/nvme/target/admin-cmd.c
+++ b/drivers/nvme/target/admin-cmd.c
@@ -433,8 +433,7 @@ static void nvmet_execute_identify_ctrl(struct nvmet_req *req)
 	id->nn = cpu_to_le32(NVMET_MAX_NAMESPACES);
 	id->mnan = cpu_to_le32(NVMET_MAX_NAMESPACES);
 	id->oncs = cpu_to_le16(NVME_CTRL_ONCS_DSM |
-			NVME_CTRL_ONCS_WRITE_ZEROES);
-
+			NVME_CTRL_ONCS_WRITE_ZEROES | NVME_CTRL_ONCS_COPY);
 	/* XXX: don't report vwc if the underlying device is write through */
 	id->vwc = NVME_CTRL_VWC_PRESENT;
 
@@ -536,6 +535,12 @@ static void nvmet_execute_identify_ns(struct nvmet_req *req)
 
 	if (req->ns->bdev)
 		nvmet_bdev_set_limits(req->ns->bdev, id);
+	else {
+		id->msrc = (__force u8)to0based(BIO_MAX_VECS - 1);
+		id->mssrl = cpu_to_le16(BIO_MAX_VECS <<
+					(PAGE_SHIFT - SECTOR_SHIFT));
+		id->mcl = cpu_to_le32(le16_to_cpu(id->mssrl));
+	}
 
 	/*
 	 * We just provide a single LBA format that matches what the
diff --git a/drivers/nvme/target/io-cmd-bdev.c b/drivers/nvme/target/io-cmd-bdev.c
index 468833675cc9..444447df9222 100644
--- a/drivers/nvme/target/io-cmd-bdev.c
+++ b/drivers/nvme/target/io-cmd-bdev.c
@@ -46,6 +46,18 @@ void nvmet_bdev_set_limits(struct block_device *bdev, struct nvme_id_ns *id)
 	id->npda = id->npdg;
 	/* NOWS = Namespace Optimal Write Size */
 	id->nows = to0based(bdev_io_opt(bdev) / bdev_logical_block_size(bdev));
+
+	if (bdev_max_copy_sectors(bdev)) {
+		id->msrc = id->msrc;
+		id->mssrl = cpu_to_le16((bdev_max_copy_sectors(bdev) <<
+				SECTOR_SHIFT) /	bdev_logical_block_size(bdev));
+		id->mcl = cpu_to_le32((__force u32)id->mssrl);
+	} else {
+		id->msrc = (__force u8)to0based(BIO_MAX_VECS - 1);
+		id->mssrl = cpu_to_le16((BIO_MAX_VECS << PAGE_SHIFT) /
+					bdev_logical_block_size(bdev));
+		id->mcl = cpu_to_le32((__force u32)id->mssrl);
+	}
 }
 
 void nvmet_bdev_ns_disable(struct nvmet_ns *ns)
@@ -449,6 +461,87 @@ static void nvmet_bdev_execute_write_zeroes(struct nvmet_req *req)
 	}
 }
 
+static void nvmet_bdev_copy_emulation_endio(void *private, int status,
+					    ssize_t copied)
+{
+	struct nvmet_req *rq = (struct nvmet_req *)private;
+	u16 nvme_status;
+
+	if (rq->copied + copied == rq->copy_len)
+		rq->cqe->result.u32 = cpu_to_le32(1);
+	else
+		rq->cqe->result.u32 = cpu_to_le32(0);
+
+	nvme_status = errno_to_nvme_status(rq, status);
+	nvmet_req_complete(rq, nvme_status);
+}
+
+static void nvmet_bdev_copy_offload_endio(void *private, int status,
+					  ssize_t copied)
+{
+	struct nvmet_req *rq = (struct nvmet_req *)private;
+	u16 nvme_status;
+	ssize_t ret;
+
+	if (copied == rq->copy_len) {
+		rq->cqe->result.u32 = cpu_to_le32(1);
+		nvme_status = errno_to_nvme_status(rq, status);
+	} else {
+		rq->copied = copied;
+		ret = blkdev_copy_emulation(rq->ns->bdev, rq->copy_dst + copied,
+					    rq->ns->bdev, rq->copy_src + copied,
+					    rq->copy_len - copied,
+					    nvmet_bdev_copy_emulation_endio,
+					    (void *)rq, GFP_KERNEL);
+		if (ret == -EIOCBQUEUED)
+			return;
+		rq->cqe->result.u32 = cpu_to_le32(0);
+		nvme_status = errno_to_nvme_status(rq, status);
+	}
+	nvmet_req_complete(rq, nvme_status);
+}
+
+/*
+ * At present we handle only one range entry, since copy offload is aligned with
+ * copy_file_range, only one entry is passed from block layer.
+ */
+static void nvmet_bdev_execute_copy(struct nvmet_req *rq)
+{
+	struct nvme_copy_range range;
+	struct nvme_command *cmd = rq->cmd;
+	ssize_t ret;
+	u16 status;
+
+	status = nvmet_copy_from_sgl(rq, 0, &range, sizeof(range));
+	if (status)
+		goto err_rq_complete;
+
+	rq->copy_dst = le64_to_cpu(cmd->copy.sdlba) << rq->ns->blksize_shift;
+	rq->copy_src = le64_to_cpu(range.slba) << rq->ns->blksize_shift;
+	rq->copy_len = (range.nlb + 1) << rq->ns->blksize_shift;
+	rq->copied = 0;
+
+	if (bdev_max_copy_sectors(rq->ns->bdev)) {
+		ret = blkdev_copy_offload(rq->ns->bdev, rq->copy_dst,
+					  rq->copy_src, rq->copy_len,
+					  nvmet_bdev_copy_offload_endio,
+					  (void *)rq, GFP_KERNEL);
+		if (ret == -EIOCBQUEUED)
+			return;
+	}
+	ret = blkdev_copy_emulation(rq->ns->bdev, rq->copy_dst, rq->ns->bdev,
+				    rq->copy_src, rq->copy_len,
+				    nvmet_bdev_copy_emulation_endio, (void *)rq,
+				    GFP_KERNEL);
+	if (ret == -EIOCBQUEUED)
+		return;
+
+	rq->cqe->result.u32 = cpu_to_le32(0);
+	status = blk_to_nvme_status(rq, ret);
+err_rq_complete:
+	nvmet_req_complete(rq, status);
+}
+
 u16 nvmet_bdev_parse_io_cmd(struct nvmet_req *req)
 {
 	switch (req->cmd->common.opcode) {
@@ -467,6 +560,10 @@ u16 nvmet_bdev_parse_io_cmd(struct nvmet_req *req)
 	case nvme_cmd_write_zeroes:
 		req->execute = nvmet_bdev_execute_write_zeroes;
 		return 0;
+	case nvme_cmd_copy:
+		req->execute = nvmet_bdev_execute_copy;
+		return 0;
+
 	default:
 		return nvmet_report_invalid_opcode(req);
 	}
diff --git a/drivers/nvme/target/io-cmd-file.c b/drivers/nvme/target/io-cmd-file.c
index 2d068439b129..4524cfffa4c6 100644
--- a/drivers/nvme/target/io-cmd-file.c
+++ b/drivers/nvme/target/io-cmd-file.c
@@ -322,6 +322,47 @@ static void nvmet_file_dsm_work(struct work_struct *w)
 	}
 }
 
+static void nvmet_file_copy_work(struct work_struct *w)
+{
+	struct nvmet_req *req = container_of(w, struct nvmet_req, f.work);
+	int nr_range = req->cmd->copy.nr_range + 1;
+	u16 status = 0;
+	int src, id;
+	ssize_t len, ret;
+	loff_t pos;
+
+	pos = le64_to_cpu(req->cmd->copy.sdlba) << req->ns->blksize_shift;
+	if (unlikely(pos + req->transfer_len > req->ns->size)) {
+		nvmet_req_complete(req, errno_to_nvme_status(req, -ENOSPC));
+		return;
+	}
+
+	for (id = 0 ; id < nr_range; id++) {
+		struct nvme_copy_range range;
+
+		status = nvmet_copy_from_sgl(req, id * sizeof(range), &range,
+					     sizeof(range));
+		if (status)
+			break;
+
+		src = (le64_to_cpu(range.slba) << (req->ns->blksize_shift));
+		len = (le16_to_cpu(range.nlb) + 1) << (req->ns->blksize_shift);
+		ret = vfs_copy_file_range(req->ns->file, src, req->ns->file,
+					  pos, len, 0);
+		pos += ret;
+		if (ret != len) {
+			req->cqe->result.u32 = cpu_to_le32(id);
+			if (ret < 0)
+				status = errno_to_nvme_status(req, ret);
+			else
+				status = errno_to_nvme_status(req, -EIO);
+			break;
+		}
+	}
+
+	nvmet_req_complete(req, status);
+}
+
 static void nvmet_file_execute_dsm(struct nvmet_req *req)
 {
 	if (!nvmet_check_data_len_lte(req, nvmet_dsm_len(req)))
@@ -330,6 +371,12 @@ static void nvmet_file_execute_dsm(struct nvmet_req *req)
 	queue_work(nvmet_wq, &req->f.work);
 }
 
+static void nvmet_file_execute_copy(struct nvmet_req *req)
+{
+	INIT_WORK(&req->f.work, nvmet_file_copy_work);
+	queue_work(nvmet_wq, &req->f.work);
+}
+
 static void nvmet_file_write_zeroes_work(struct work_struct *w)
 {
 	struct nvmet_req *req = container_of(w, struct nvmet_req, f.work);
@@ -376,6 +423,9 @@ u16 nvmet_file_parse_io_cmd(struct nvmet_req *req)
 	case nvme_cmd_write_zeroes:
 		req->execute = nvmet_file_execute_write_zeroes;
 		return 0;
+	case nvme_cmd_copy:
+		req->execute = nvmet_file_execute_copy;
+		return 0;
 	default:
 		return nvmet_report_invalid_opcode(req);
 	}
diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index 8cfd60f3b564..42aa7bac6f7a 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -393,6 +393,10 @@ struct nvmet_req {
 	struct device		*p2p_client;
 	u16			error_loc;
 	u64			error_slba;
+	off_t			copy_dst;
+	off_t			copy_src;
+	size_t			copy_len;
+	size_t			copied;
 };
 
 #define NVMET_MAX_MPOOL_BVEC		16
diff --git a/drivers/nvme/target/trace.c b/drivers/nvme/target/trace.c
index bff454d46255..551fdf029381 100644
--- a/drivers/nvme/target/trace.c
+++ b/drivers/nvme/target/trace.c
@@ -92,6 +92,23 @@ static const char *nvmet_trace_dsm(struct trace_seq *p, u8 *cdw10)
 	return ret;
 }
 
+static const char *nvmet_trace_copy(struct trace_seq *p, u8 *cdw10)
+{
+	const char *ret = trace_seq_buffer_ptr(p);
+	u64 sdlba = get_unaligned_le64(cdw10);
+	u8 nr_range = get_unaligned_le16(cdw10 + 8);
+	u16 control = get_unaligned_le16(cdw10 + 10);
+	u32 dsmgmt = get_unaligned_le32(cdw10 + 12);
+	u32 reftag = get_unaligned_le32(cdw10 +  16);
+
+	trace_seq_printf(p,
+		"sdlba=%llu, nr_range=%u, ctrl=1x%x, dsmgmt=%u, reftag=%u",
+		sdlba, nr_range, control, dsmgmt, reftag);
+	trace_seq_putc(p, 0);
+
+	return ret;
+}
+
 static const char *nvmet_trace_common(struct trace_seq *p, u8 *cdw10)
 {
 	const char *ret = trace_seq_buffer_ptr(p);
@@ -129,6 +146,8 @@ const char *nvmet_trace_parse_nvm_cmd(struct trace_seq *p,
 		return nvmet_trace_read_write(p, cdw10);
 	case nvme_cmd_dsm:
 		return nvmet_trace_dsm(p, cdw10);
+	case nvme_cmd_copy:
+		return nvmet_trace_copy(p, cdw10);
 	default:
 		return nvmet_trace_common(p, cdw10);
 	}
-- 
2.35.1.500.gb896f729e2

[PATCH v15 09/12] dm: Add support for copy offload

[Nitesh Shetty]

Before enabling copy for dm target, check if underlying devices and
dm target support copy. Avoid split happening inside dm target.
Fail early if the request needs split, currently splitting copy
request is not supported.

Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
---
 drivers/md/dm-table.c         | 37 +++++++++++++++++++++++++++++++++++
 drivers/md/dm.c               |  7 +++++++
 include/linux/device-mapper.h |  3 +++
 3 files changed, 47 insertions(+)

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 7d208b2b1a19..a192c19b68e4 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1862,6 +1862,38 @@ static bool dm_table_supports_nowait(struct dm_table *t)
 	return true;
 }
 
+static int device_not_copy_capable(struct dm_target *ti, struct dm_dev *dev,
+				   sector_t start, sector_t len, void *data)
+{
+	struct request_queue *q = bdev_get_queue(dev->bdev);
+
+	return !q->limits.max_copy_sectors;
+}
+
+static bool dm_table_supports_copy(struct dm_table *t)
+{
+	struct dm_target *ti;
+	unsigned int i;
+
+	for (i = 0; i < t->num_targets; i++) {
+		ti = dm_table_get_target(t, i);
+
+		if (!ti->copy_offload_supported)
+			return false;
+
+		/*
+		 * target provides copy support (as implied by setting
+		 * 'copy_offload_supported')
+		 * and it relies on _all_ data devices having copy support.
+		 */
+		if (!ti->type->iterate_devices ||
+		    ti->type->iterate_devices(ti, device_not_copy_capable, NULL))
+			return false;
+	}
+
+	return true;
+}
+
 static int device_not_discard_capable(struct dm_target *ti, struct dm_dev *dev,
 				      sector_t start, sector_t len, void *data)
 {
@@ -1944,6 +1976,11 @@ int dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 		q->limits.discard_misaligned = 0;
 	}
 
+	if (!dm_table_supports_copy(t)) {
+		q->limits.max_copy_sectors = 0;
+		q->limits.max_copy_hw_sectors = 0;
+	}
+
 	if (!dm_table_supports_secure_erase(t))
 		q->limits.max_secure_erase_sectors = 0;
 
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index f0f118ab20fa..f9d6215e6d4d 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1732,6 +1732,13 @@ static blk_status_t __split_and_process_bio(struct clone_info *ci)
 	if (unlikely(ci->is_abnormal_io))
 		return __process_abnormal_io(ci, ti);
 
+	if ((unlikely(op_is_copy(ci->bio->bi_opf)) &&
+	    max_io_len(ti, ci->sector) < ci->sector_count)) {
+		DMERR("Error, IO size(%u) > max target size(%llu)\n",
+		      ci->sector_count, max_io_len(ti, ci->sector));
+		return BLK_STS_IOERR;
+	}
+
 	/*
 	 * Only support bio polling for normal IO, and the target io is
 	 * exactly inside the dm_io instance (verified in dm_poll_dm_io)
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 69d0435c7ebb..98db52d1c773 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -396,6 +396,9 @@ struct dm_target {
 	 * bio_set_dev(). NOTE: ideally a target should _not_ need this.
 	 */
 	bool needs_bio_set_dev:1;
+
+	/* copy offload is supported */
+	bool copy_offload_supported:1;
 };
 
 void *dm_per_bio_data(struct bio *bio, size_t data_size);
-- 
2.35.1.500.gb896f729e2

[PATCH v15 10/12] dm: Enable copy offload for dm-linear target

[Nitesh Shetty]

Setting copy_offload_supported flag to enable offload.

Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
---
 drivers/md/dm-linear.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
index f4448d520ee9..1d1ee30bbefb 100644
--- a/drivers/md/dm-linear.c
+++ b/drivers/md/dm-linear.c
@@ -62,6 +62,7 @@ static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	ti->num_discard_bios = 1;
 	ti->num_secure_erase_bios = 1;
 	ti->num_write_zeroes_bios = 1;
+	ti->copy_offload_supported = 1;
 	ti->private = lc;
 	return 0;
 
-- 
2.35.1.500.gb896f729e2

[PATCH v15 11/12] null: Enable trace capability for null block

[Nitesh Shetty]

This is a prep patch to enable copy trace capability.
At present only zoned null_block is using trace, so we decoupled trace
and zoned dependency to make it usable in null_blk driver also.

Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
---
 drivers/block/null_blk/Makefile | 2 --
 drivers/block/null_blk/main.c   | 3 +++
 drivers/block/null_blk/trace.h  | 2 ++
 drivers/block/null_blk/zoned.c  | 1 -
 4 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/block/null_blk/Makefile b/drivers/block/null_blk/Makefile
index 84c36e512ab8..672adcf0ad24 100644
--- a/drivers/block/null_blk/Makefile
+++ b/drivers/block/null_blk/Makefile
@@ -5,7 +5,5 @@ ccflags-y			+= -I$(src)
 
 obj-$(CONFIG_BLK_DEV_NULL_BLK)	+= null_blk.o
 null_blk-objs			:= main.o
-ifeq ($(CONFIG_BLK_DEV_ZONED), y)
 null_blk-$(CONFIG_TRACING) 	+= trace.o
-endif
 null_blk-$(CONFIG_BLK_DEV_ZONED) += zoned.o
diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index 864013019d6b..b48901b2b573 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -11,6 +11,9 @@
 #include <linux/init.h>
 #include "null_blk.h"
 
+#define CREATE_TRACE_POINTS
+#include "trace.h"
+
 #undef pr_fmt
 #define pr_fmt(fmt)	"null_blk: " fmt
 
diff --git a/drivers/block/null_blk/trace.h b/drivers/block/null_blk/trace.h
index 6b2b370e786f..91446c34eac2 100644
--- a/drivers/block/null_blk/trace.h
+++ b/drivers/block/null_blk/trace.h
@@ -30,6 +30,7 @@ static inline void __assign_disk_name(char *name, struct gendisk *disk)
 }
 #endif
 
+#ifdef CONFIG_BLK_DEV_ZONED
 TRACE_EVENT(nullb_zone_op,
 	    TP_PROTO(struct nullb_cmd *cmd, unsigned int zone_no,
 		     unsigned int zone_cond),
@@ -67,6 +68,7 @@ TRACE_EVENT(nullb_report_zones,
 	    TP_printk("%s nr_zones=%u",
 		      __print_disk_name(__entry->disk), __entry->nr_zones)
 );
+#endif /* CONFIG_BLK_DEV_ZONED */
 
 #endif /* _TRACE_NULLB_H */
 
diff --git a/drivers/block/null_blk/zoned.c b/drivers/block/null_blk/zoned.c
index 55c5b48bc276..9694461a31a4 100644
--- a/drivers/block/null_blk/zoned.c
+++ b/drivers/block/null_blk/zoned.c
@@ -3,7 +3,6 @@
 #include <linux/bitmap.h>
 #include "null_blk.h"
 
-#define CREATE_TRACE_POINTS
 #include "trace.h"
 
 #undef pr_fmt
-- 
2.35.1.500.gb896f729e2

[PATCH v15 12/12] null_blk: add support for copy offload

[Nitesh Shetty]

Implementation is based on existing read and write infrastructure.
copy_max_bytes: A new configfs and module parameter is introduced, which
can be used to set hardware/driver supported maximum copy limit.
Only request based queue mode will support for copy offload.
Added tracefs support to copy IO tracing.

Suggested-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
Signed-off-by: Vincent Fu <vincent.fu@samsung.com>
---
 Documentation/block/null_blk.rst  |  5 ++
 drivers/block/null_blk/main.c     | 97 ++++++++++++++++++++++++++++++-
 drivers/block/null_blk/null_blk.h |  1 +
 drivers/block/null_blk/trace.h    | 23 ++++++++
 4 files changed, 123 insertions(+), 3 deletions(-)

diff --git a/Documentation/block/null_blk.rst b/Documentation/block/null_blk.rst
index 4dd78f24d10a..6153e02fcf13 100644
--- a/Documentation/block/null_blk.rst
+++ b/Documentation/block/null_blk.rst
@@ -149,3 +149,8 @@ zone_size=[MB]: Default: 256
 zone_nr_conv=[nr_conv]: Default: 0
   The number of conventional zones to create when block device is zoned.  If
   zone_nr_conv >= nr_zones, it will be reduced to nr_zones - 1.
+
+copy_max_bytes=[size in bytes]: Default: COPY_MAX_BYTES
+  A module and configfs parameter which can be used to set hardware/driver
+  supported maximum copy offload limit.
+  COPY_MAX_BYTES(=128MB at present) is defined in fs.h
diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index b48901b2b573..26124f2baadc 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -160,6 +160,10 @@ static int g_max_sectors;
 module_param_named(max_sectors, g_max_sectors, int, 0444);
 MODULE_PARM_DESC(max_sectors, "Maximum size of a command (in 512B sectors)");
 
+static unsigned long g_copy_max_bytes = BLK_COPY_MAX_BYTES;
+module_param_named(copy_max_bytes, g_copy_max_bytes, ulong, 0444);
+MODULE_PARM_DESC(copy_max_bytes, "Maximum size of a copy command (in bytes)");
+
 static unsigned int nr_devices = 1;
 module_param(nr_devices, uint, 0444);
 MODULE_PARM_DESC(nr_devices, "Number of devices to register");
@@ -412,6 +416,7 @@ NULLB_DEVICE_ATTR(home_node, uint, NULL);
 NULLB_DEVICE_ATTR(queue_mode, uint, NULL);
 NULLB_DEVICE_ATTR(blocksize, uint, NULL);
 NULLB_DEVICE_ATTR(max_sectors, uint, NULL);
+NULLB_DEVICE_ATTR(copy_max_bytes, uint, NULL);
 NULLB_DEVICE_ATTR(irqmode, uint, NULL);
 NULLB_DEVICE_ATTR(hw_queue_depth, uint, NULL);
 NULLB_DEVICE_ATTR(index, uint, NULL);
@@ -553,6 +558,7 @@ static struct configfs_attribute *nullb_device_attrs[] = {
 	&nullb_device_attr_queue_mode,
 	&nullb_device_attr_blocksize,
 	&nullb_device_attr_max_sectors,
+	&nullb_device_attr_copy_max_bytes,
 	&nullb_device_attr_irqmode,
 	&nullb_device_attr_hw_queue_depth,
 	&nullb_device_attr_index,
@@ -659,7 +665,8 @@ static ssize_t memb_group_features_show(struct config_item *item, char *page)
 			"poll_queues,power,queue_mode,shared_tag_bitmap,size,"
 			"submit_queues,use_per_node_hctx,virt_boundary,zoned,"
 			"zone_capacity,zone_max_active,zone_max_open,"
-			"zone_nr_conv,zone_offline,zone_readonly,zone_size\n");
+			"zone_nr_conv,zone_offline,zone_readonly,zone_size,"
+			"copy_max_bytes\n");
 }
 
 CONFIGFS_ATTR_RO(memb_group_, features);
@@ -725,6 +732,7 @@ static struct nullb_device *null_alloc_dev(void)
 	dev->queue_mode = g_queue_mode;
 	dev->blocksize = g_bs;
 	dev->max_sectors = g_max_sectors;
+	dev->copy_max_bytes = g_copy_max_bytes;
 	dev->irqmode = g_irqmode;
 	dev->hw_queue_depth = g_hw_queue_depth;
 	dev->blocking = g_blocking;
@@ -1274,6 +1282,81 @@ static int null_transfer(struct nullb *nullb, struct page *page,
 	return err;
 }
 
+static inline int nullb_setup_copy(struct nullb *nullb, struct request *req,
+				   bool is_fua)
+{
+	sector_t sector_in = 0, sector_out = 0;
+	loff_t offset_in, offset_out;
+	void *in, *out;
+	ssize_t chunk, rem = 0;
+	struct bio *bio;
+	struct nullb_page *t_page_in, *t_page_out;
+	u16 seg = 1;
+	int status = -EIO;
+
+	if (blk_rq_nr_phys_segments(req) != BLK_COPY_MAX_SEGMENTS)
+		return status;
+
+	/*
+	 * First bio contains information about source and last bio contains
+	 * information about destination.
+	 */
+	__rq_for_each_bio(bio, req) {
+		if (seg == blk_rq_nr_phys_segments(req)) {
+			sector_out = bio->bi_iter.bi_sector;
+			if (rem != bio->bi_iter.bi_size)
+				return status;
+		} else {
+			sector_in = bio->bi_iter.bi_sector;
+			rem = bio->bi_iter.bi_size;
+		}
+		seg++;
+	}
+
+	trace_nullb_copy_op(req, sector_out << SECTOR_SHIFT,
+			    sector_in << SECTOR_SHIFT, rem);
+
+	spin_lock_irq(&nullb->lock);
+	while (rem > 0) {
+		chunk = min_t(size_t, nullb->dev->blocksize, rem);
+		offset_in = (sector_in & SECTOR_MASK) << SECTOR_SHIFT;
+		offset_out = (sector_out & SECTOR_MASK) << SECTOR_SHIFT;
+
+		if (null_cache_active(nullb) && !is_fua)
+			null_make_cache_space(nullb, PAGE_SIZE);
+
+		t_page_in = null_lookup_page(nullb, sector_in, false,
+					     !null_cache_active(nullb));
+		if (!t_page_in)
+			goto err;
+		t_page_out = null_insert_page(nullb, sector_out,
+					      !null_cache_active(nullb) ||
+					      is_fua);
+		if (!t_page_out)
+			goto err;
+
+		in = kmap_local_page(t_page_in->page);
+		out = kmap_local_page(t_page_out->page);
+
+		memcpy(out + offset_out, in + offset_in, chunk);
+		kunmap_local(out);
+		kunmap_local(in);
+		__set_bit(sector_out & SECTOR_MASK, t_page_out->bitmap);
+
+		if (is_fua)
+			null_free_sector(nullb, sector_out, true);
+
+		rem -= chunk;
+		sector_in += chunk >> SECTOR_SHIFT;
+		sector_out += chunk >> SECTOR_SHIFT;
+	}
+
+	status = 0;
+err:
+	spin_unlock_irq(&nullb->lock);
+	return status;
+}
+
 static int null_handle_rq(struct nullb_cmd *cmd)
 {
 	struct request *rq = cmd->rq;
@@ -1283,13 +1366,16 @@ static int null_handle_rq(struct nullb_cmd *cmd)
 	sector_t sector = blk_rq_pos(rq);
 	struct req_iterator iter;
 	struct bio_vec bvec;
+	bool fua = rq->cmd_flags & REQ_FUA;
+
+	if (op_is_copy(req_op(rq)))
+		return nullb_setup_copy(nullb, rq, fua);
 
 	spin_lock_irq(&nullb->lock);
 	rq_for_each_segment(bvec, rq, iter) {
 		len = bvec.bv_len;
 		err = null_transfer(nullb, bvec.bv_page, len, bvec.bv_offset,
-				     op_is_write(req_op(rq)), sector,
-				     rq->cmd_flags & REQ_FUA);
+				    op_is_write(req_op(rq)), sector, fua);
 		if (err) {
 			spin_unlock_irq(&nullb->lock);
 			return err;
@@ -2045,6 +2131,9 @@ static int null_validate_conf(struct nullb_device *dev)
 		return -EINVAL;
 	}
 
+	if (dev->queue_mode == NULL_Q_BIO)
+		dev->copy_max_bytes = 0;
+
 	return 0;
 }
 
@@ -2164,6 +2253,8 @@ static int null_add_dev(struct nullb_device *dev)
 		dev->max_sectors = queue_max_hw_sectors(nullb->q);
 	dev->max_sectors = min(dev->max_sectors, BLK_DEF_MAX_SECTORS);
 	blk_queue_max_hw_sectors(nullb->q, dev->max_sectors);
+	blk_queue_max_copy_hw_sectors(nullb->q,
+				      dev->copy_max_bytes >> SECTOR_SHIFT);
 
 	if (dev->virt_boundary)
 		blk_queue_virt_boundary(nullb->q, PAGE_SIZE - 1);
diff --git a/drivers/block/null_blk/null_blk.h b/drivers/block/null_blk/null_blk.h
index 929f659dd255..e82e53a2e2df 100644
--- a/drivers/block/null_blk/null_blk.h
+++ b/drivers/block/null_blk/null_blk.h
@@ -107,6 +107,7 @@ struct nullb_device {
 	unsigned int queue_mode; /* block interface */
 	unsigned int blocksize; /* block size */
 	unsigned int max_sectors; /* Max sectors per command */
+	unsigned long copy_max_bytes; /* Max copy offload length in bytes */
 	unsigned int irqmode; /* IRQ completion handler */
 	unsigned int hw_queue_depth; /* queue depth */
 	unsigned int index; /* index of the disk, only valid with a disk */
diff --git a/drivers/block/null_blk/trace.h b/drivers/block/null_blk/trace.h
index 91446c34eac2..2f2c1d1c2b48 100644
--- a/drivers/block/null_blk/trace.h
+++ b/drivers/block/null_blk/trace.h
@@ -70,6 +70,29 @@ TRACE_EVENT(nullb_report_zones,
 );
 #endif /* CONFIG_BLK_DEV_ZONED */
 
+TRACE_EVENT(nullb_copy_op,
+		TP_PROTO(struct request *req,
+			 sector_t dst, sector_t src, size_t len),
+		TP_ARGS(req, dst, src, len),
+		TP_STRUCT__entry(
+				 __array(char, disk, DISK_NAME_LEN)
+				 __field(enum req_op, op)
+				 __field(sector_t, dst)
+				 __field(sector_t, src)
+				 __field(size_t, len)
+		),
+		TP_fast_assign(
+			       __entry->op = req_op(req);
+			       __assign_disk_name(__entry->disk, req->q->disk);
+			       __entry->dst = dst;
+			       __entry->src = src;
+			       __entry->len = len;
+		),
+		TP_printk("%s req=%-15s: dst=%llu, src=%llu, len=%lu",
+			  __print_disk_name(__entry->disk),
+			  blk_op_str(__entry->op),
+			  __entry->dst, __entry->src, __entry->len)
+);
 #endif /* _TRACE_NULLB_H */
 
 #undef TRACE_INCLUDE_PATH
-- 
2.35.1.500.gb896f729e2

Re: [PATCH v15 12/12] null_blk: add support for copy offload

[kernel test robot]

Hi Nitesh,

kernel test robot noticed the following build warnings:

[auto build test WARNING on c50216cfa084d5eb67dc10e646a3283da1595bb6]

url:    https://github.com/intel-lab-lkp/linux/commits/Nitesh-Shetty/block-Introduce-queue-limits-and-sysfs-for-copy-offload-support/20230907-015817
base:   c50216cfa084d5eb67dc10e646a3283da1595bb6
patch link:    https://lore.kernel.org/r/20230906163844.18754-13-nj.shetty%40samsung.com
patch subject: [PATCH v15 12/12] null_blk: add support for copy offload
config: arm-randconfig-001-20230907 (https://download.01.org/0day-ci/archive/20230907/202309070542.P9utuu9p-lkp@intel.com/config)
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project.git f28c006a5895fc0e329fe15fead81e37457cb1d1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20230907/202309070542.P9utuu9p-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202309070542.P9utuu9p-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from drivers/block/null_blk/main.c:15:
   In file included from drivers/block/null_blk/./trace.h:104:
   In file included from include/trace/define_trace.h:102:
   In file included from include/trace/trace_events.h:237:
>> drivers/block/null_blk/./trace.h:94:34: warning: format specifies type 'unsigned long' but the argument has type 'size_t' (aka 'unsigned int') [-Wformat]
                             __entry->dst, __entry->src, __entry->len)
                             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~
   include/trace/stages/stage3_trace_output.h:6:17: note: expanded from macro '__entry'
   #define __entry field
                   ^
   include/trace/stages/stage3_trace_output.h:9:43: note: expanded from macro 'TP_printk'
   #define TP_printk(fmt, args...) fmt "\n", args
                                   ~~~       ^
   include/trace/trace_events.h:45:16: note: expanded from macro 'TRACE_EVENT'
                                PARAMS(print));                   \
                                ~~~~~~~^~~~~~~
   include/linux/tracepoint.h:107:25: note: expanded from macro 'PARAMS'
   #define PARAMS(args...) args
                           ^~~~
   include/trace/trace_events.h:203:27: note: expanded from macro 'DECLARE_EVENT_CLASS'
           trace_event_printf(iter, print);                                \
                                    ^~~~~
   1 warning generated.


vim +94 drivers/block/null_blk/./trace.h

    72	
    73	TRACE_EVENT(nullb_copy_op,
    74			TP_PROTO(struct request *req,
    75				 sector_t dst, sector_t src, size_t len),
    76			TP_ARGS(req, dst, src, len),
    77			TP_STRUCT__entry(
    78					 __array(char, disk, DISK_NAME_LEN)
    79					 __field(enum req_op, op)
    80					 __field(sector_t, dst)
    81					 __field(sector_t, src)
    82					 __field(size_t, len)
    83			),
    84			TP_fast_assign(
    85				       __entry->op = req_op(req);
    86				       __assign_disk_name(__entry->disk, req->q->disk);
    87				       __entry->dst = dst;
    88				       __entry->src = src;
    89				       __entry->len = len;
    90			),
    91			TP_printk("%s req=%-15s: dst=%llu, src=%llu, len=%lu",
    92				  __print_disk_name(__entry->disk),
    93				  blk_op_str(__entry->op),
  > 94				  __entry->dst, __entry->src, __entry->len)
    95	);
    96	#endif /* _TRACE_NULLB_H */
    97	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v15 12/12] null_blk: add support for copy offload

[kernel test robot]

Hi Nitesh,

kernel test robot noticed the following build warnings:

[auto build test WARNING on c50216cfa084d5eb67dc10e646a3283da1595bb6]

url:    https://github.com/intel-lab-lkp/linux/commits/Nitesh-Shetty/block-Introduce-queue-limits-and-sysfs-for-copy-offload-support/20230907-015817
base:   c50216cfa084d5eb67dc10e646a3283da1595bb6
patch link:    https://lore.kernel.org/r/20230906163844.18754-13-nj.shetty%40samsung.com
patch subject: [PATCH v15 12/12] null_blk: add support for copy offload
config: parisc-allyesconfig (https://download.01.org/0day-ci/archive/20230907/202309070607.akFEF327-lkp@intel.com/config)
compiler: hppa-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20230907/202309070607.akFEF327-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202309070607.akFEF327-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from include/trace/define_trace.h:102,
                    from drivers/block/null_blk/trace.h:104,
                    from drivers/block/null_blk/main.c:15:
   drivers/block/null_blk/./trace.h: In function 'trace_raw_output_nullb_copy_op':
>> drivers/block/null_blk/./trace.h:91:27: warning: format '%lu' expects argument of type 'long unsigned int', but argument 7 has type 'size_t' {aka 'unsigned int'} [-Wformat=]
      91 |                 TP_printk("%s req=%-15s: dst=%llu, src=%llu, len=%lu",
         |                           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/trace/trace_events.h:203:34: note: in definition of macro 'DECLARE_EVENT_CLASS'
     203 |         trace_event_printf(iter, print);                                \
         |                                  ^~~~~
   include/trace/trace_events.h:45:30: note: in expansion of macro 'PARAMS'
      45 |                              PARAMS(print));                   \
         |                              ^~~~~~
   drivers/block/null_blk/./trace.h:73:1: note: in expansion of macro 'TRACE_EVENT'
      73 | TRACE_EVENT(nullb_copy_op,
         | ^~~~~~~~~~~
   drivers/block/null_blk/./trace.h:91:17: note: in expansion of macro 'TP_printk'
      91 |                 TP_printk("%s req=%-15s: dst=%llu, src=%llu, len=%lu",
         |                 ^~~~~~~~~
   In file included from include/trace/trace_events.h:237:
   drivers/block/null_blk/./trace.h:91:68: note: format string is defined here
      91 |                 TP_printk("%s req=%-15s: dst=%llu, src=%llu, len=%lu",
         |                                                                  ~~^
         |                                                                    |
         |                                                                    long unsigned int
         |                                                                  %u


vim +91 drivers/block/null_blk/./trace.h

    72	
    73	TRACE_EVENT(nullb_copy_op,
    74			TP_PROTO(struct request *req,
    75				 sector_t dst, sector_t src, size_t len),
    76			TP_ARGS(req, dst, src, len),
    77			TP_STRUCT__entry(
    78					 __array(char, disk, DISK_NAME_LEN)
    79					 __field(enum req_op, op)
    80					 __field(sector_t, dst)
    81					 __field(sector_t, src)
    82					 __field(size_t, len)
    83			),
    84			TP_fast_assign(
    85				       __entry->op = req_op(req);
    86				       __assign_disk_name(__entry->disk, req->q->disk);
    87				       __entry->dst = dst;
    88				       __entry->src = src;
    89				       __entry->len = len;
    90			),
  > 91			TP_printk("%s req=%-15s: dst=%llu, src=%llu, len=%lu",
    92				  __print_disk_name(__entry->disk),
    93				  blk_op_str(__entry->op),
    94				  __entry->dst, __entry->src, __entry->len)
    95	);
    96	#endif /* _TRACE_NULLB_H */
    97	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v15 02/12] Add infrastructure for copy offload in block and request layer.

[Hannes Reinecke]

On 9/6/23 18:38, Nitesh Shetty wrote:
> We add two new opcode REQ_OP_COPY_SRC, REQ_OP_COPY_DST.
> Since copy is a composite operation involving src and dst sectors/lba,
> each needs to be represented by a separate bio to make it compatible
> with device mapper.
> We expect caller to take a plug and send bio with source information,
> followed by bio with destination information.
> Once the src bio arrives we form a request and wait for destination
> bio. Upon arrival of destination we merge these two bio's and send
> corresponding request down to device driver.
> 
> Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
> Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
> ---
>   block/blk-core.c          |  7 +++++++
>   block/blk-merge.c         | 41 +++++++++++++++++++++++++++++++++++++++
>   block/blk.h               | 16 +++++++++++++++
>   block/elevator.h          |  1 +
>   include/linux/bio.h       |  6 +-----
>   include/linux/blk_types.h | 10 ++++++++++
>   6 files changed, 76 insertions(+), 5 deletions(-)
> 
Having two separate bios is okay, and what one would expect.
What is slightly strange is the merging functionality;
That could do with some more explanation why this approach was taken.
And also some checks in the merging code to avoid merging non-copy 
offload  bios.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman

Re: [PATCH v15 03/12] block: add copy offload support

[Hannes Reinecke]

On 9/6/23 18:38, Nitesh Shetty wrote:
> Introduce blkdev_copy_offload to perform copy offload.
> Issue REQ_OP_COPY_SRC with source info along with taking a plug.
> This flows till request layer and waits for dst bio to arrive.
> Issue REQ_OP_COPY_DST with destination info and this bio reaches request
> layer and merges with src request.
> For any reason, if a request comes to the driver with only one of src/dst
> bio, we fail the copy offload.
> 
> Larger copy will be divided, based on max_copy_sectors limit.
> 
> Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
> Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
> ---
>   block/blk-lib.c        | 202 +++++++++++++++++++++++++++++++++++++++++
>   include/linux/blkdev.h |   4 +
>   2 files changed, 206 insertions(+)
> 
> diff --git a/block/blk-lib.c b/block/blk-lib.c
> index e59c3069e835..d22e1e7417ca 100644
> --- a/block/blk-lib.c
> +++ b/block/blk-lib.c
> @@ -10,6 +10,22 @@
>   
>   #include "blk.h"
>   
> +/* Keeps track of all outstanding copy IO */
> +struct blkdev_copy_io {
> +	atomic_t refcount;
> +	ssize_t copied;
> +	int status;
> +	struct task_struct *waiter;
> +	void (*endio)(void *private, int status, ssize_t copied);
> +	void *private;
> +};
> +
> +/* Keeps track of single outstanding copy offload IO */
> +struct blkdev_copy_offload_io {
> +	struct blkdev_copy_io *cio;
> +	loff_t offset;
> +};
> +
>   static sector_t bio_discard_limit(struct block_device *bdev, sector_t sector)
>   {
>   	unsigned int discard_granularity = bdev_discard_granularity(bdev);
> @@ -115,6 +131,192 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
>   }
>   EXPORT_SYMBOL(blkdev_issue_discard);
>   
> +static inline ssize_t blkdev_copy_sanity_check(struct block_device *bdev_in,
> +					       loff_t pos_in,
> +					       struct block_device *bdev_out,
> +					       loff_t pos_out, size_t len)
> +{
> +	unsigned int align = max(bdev_logical_block_size(bdev_out),
> +				 bdev_logical_block_size(bdev_in)) - 1;
> +
> +	if ((pos_in & align) || (pos_out & align) || (len & align) || !len ||
> +	    len >= BLK_COPY_MAX_BYTES)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
> +static inline void blkdev_copy_endio(struct blkdev_copy_io *cio)
> +{
> +	if (cio->endio) {
> +		cio->endio(cio->private, cio->status, cio->copied);
> +		kfree(cio);
> +	} else {
> +		struct task_struct *waiter = cio->waiter;
> +
> +		WRITE_ONCE(cio->waiter, NULL);
> +		blk_wake_io_task(waiter);
> +	}
> +}
> +
> +/*
> + * This must only be called once all bios have been issued so that the refcount
> + * can only decrease. This just waits for all bios to complete.
> + * Returns the length of bytes copied or error
> + */
> +static ssize_t blkdev_copy_wait_io_completion(struct blkdev_copy_io *cio)
> +{
> +	ssize_t ret;
> +
> +	for (;;) {
> +		__set_current_state(TASK_UNINTERRUPTIBLE);
> +		if (!READ_ONCE(cio->waiter))
> +			break;
> +		blk_io_schedule();
> +	}
> +	__set_current_state(TASK_RUNNING);
> +	ret = cio->copied;
> +	kfree(cio);
> +
> +	return ret;
> +}
> +
> +static void blkdev_copy_offload_dst_endio(struct bio *bio)
> +{
> +	struct blkdev_copy_offload_io *offload_io = bio->bi_private;
> +	struct blkdev_copy_io *cio = offload_io->cio;
> +
> +	if (bio->bi_status) {
> +		cio->copied = min_t(ssize_t, offload_io->offset, cio->copied);
> +		if (!cio->status)
> +			cio->status = blk_status_to_errno(bio->bi_status);
> +	}
> +	bio_put(bio);
> +
> +	if (atomic_dec_and_test(&cio->refcount))
> +		blkdev_copy_endio(cio);
> +}
> +
> +/*
> + * @bdev:	block device
> + * @pos_in:	source offset
> + * @pos_out:	destination offset
> + * @len:	length in bytes to be copied
> + * @endio:	endio function to be called on completion of copy operation,
> + *		for synchronous operation this should be NULL
> + * @private:	endio function will be called with this private data,
> + *		for synchronous operation this should be NULL
> + * @gfp_mask:	memory allocation flags (for bio_alloc)
> + *
> + * For synchronous operation returns the length of bytes copied or error
> + * For asynchronous operation returns -EIOCBQUEUED or error
> + *
> + * Description:
> + *	Copy source offset to destination offset within block device, using
> + *	device's native copy offload feature. This function can fail, and
> + *	in that case the caller can fallback to emulation.
> + *	We perform copy operation using 2 bio's.
> + *	1. We take a plug and send a REQ_OP_COPY_SRC bio along with source
> + *	sector and length. Once this bio reaches request layer, we form a
> + *	request and wait for dst bio to arrive.
> + *	2. We issue REQ_OP_COPY_DST bio along with destination sector, length.
> + *	Once this bio reaches request layer and find a request with previously
> + *	sent source info we merge the destination bio and return.
> + *	3. Release the plug and request is sent to driver
> + *	This design works only for drivers with request queue.
> + */
> +ssize_t blkdev_copy_offload(struct block_device *bdev, loff_t pos_in,
> +			    loff_t pos_out, size_t len,
> +			    void (*endio)(void *, int, ssize_t),
> +			    void *private, gfp_t gfp)
> +{
> +	struct blkdev_copy_io *cio;
> +	struct blkdev_copy_offload_io *offload_io;
> +	struct bio *src_bio, *dst_bio;
> +	ssize_t rem, chunk, ret;
> +	ssize_t max_copy_bytes = bdev_max_copy_sectors(bdev) << SECTOR_SHIFT;
> +	struct blk_plug plug;
> +
> +	if (!max_copy_bytes)
> +		return -EINVAL;
> +
> +	ret = blkdev_copy_sanity_check(bdev, pos_in, bdev, pos_out, len);
> +	if (ret)
> +		return ret;
> +
> +	cio = kzalloc(sizeof(*cio), GFP_KERNEL);
> +	if (!cio)
> +		return -ENOMEM;
> +	atomic_set(&cio->refcount, 1);
> +	cio->waiter = current;
> +	cio->endio = endio;
> +	cio->private = private;
> +
> +	/*
> +	 * If there is a error, copied will be set to least successfully
> +	 * completed copied length
> +	 */
> +	cio->copied = len;
> +	for (rem = len; rem > 0; rem -= chunk) {
> +		chunk = min(rem, max_copy_bytes);
> +
> +		offload_io = kzalloc(sizeof(*offload_io), GFP_KERNEL);
> +		if (!offload_io)
> +			goto err_free_cio;
> +		offload_io->cio = cio;
> +		/*
> +		 * For partial completion, we use offload_io->offset to truncate
> +		 * successful copy length
> +		 */
> +		offload_io->offset = len - rem;
> +
> +		src_bio = bio_alloc(bdev, 0, REQ_OP_COPY_SRC, gfp);
> +		if (!src_bio)
> +			goto err_free_offload_io;
> +		src_bio->bi_iter.bi_size = chunk;
> +		src_bio->bi_iter.bi_sector = pos_in >> SECTOR_SHIFT;
> +
> +		blk_start_plug(&plug);
> +		dst_bio = blk_next_bio(src_bio, bdev, 0, REQ_OP_COPY_DST, gfp);
> +		if (!dst_bio)
> +			goto err_free_src_bio;
> +		dst_bio->bi_iter.bi_size = chunk;
> +		dst_bio->bi_iter.bi_sector = pos_out >> SECTOR_SHIFT;
> +		dst_bio->bi_end_io = blkdev_copy_offload_dst_endio;
> +		dst_bio->bi_private = offload_io;
> +
> +		atomic_inc(&cio->refcount);
> +		submit_bio(dst_bio);
> +		blk_finish_plug(&plug);
> +		pos_in += chunk;
> +		pos_out += chunk;
> +	}
> +
> +	if (atomic_dec_and_test(&cio->refcount))
> +		blkdev_copy_endio(cio);
> +	if (cio->endio)
> +		return -EIOCBQUEUED;
> +
> +	return blkdev_copy_wait_io_completion(cio);
> +
> +err_free_src_bio:
> +	bio_put(src_bio);
> +err_free_offload_io:
> +	kfree(offload_io);
> +err_free_cio:
> +	cio->copied = min_t(ssize_t, cio->copied, (len - rem));
> +	cio->status = -ENOMEM;
> +	if (rem == len) {
> +		kfree(cio);
> +		return cio->status;
> +	}
> +	if (cio->endio)
> +		return cio->status;
> +
> +	return blkdev_copy_wait_io_completion(cio);
> +}
> +EXPORT_SYMBOL_GPL(blkdev_copy_offload);

Hmm. That looks a bit odd. Why do you have to use wait_for_completion?
Can't you submit the 'src' bio, and then submit the 'dst' bio from the 
endio handler of the 'src' bio?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman

Re: [PATCH v15 02/12] Add infrastructure for copy offload in block and request layer.

[Nitesh Shetty]

[-- Attachment #1: Type: text/plain, Size: 1997 bytes --]

On 07/09/23 07:39AM, Hannes Reinecke wrote:
>On 9/6/23 18:38, Nitesh Shetty wrote:
>>We add two new opcode REQ_OP_COPY_SRC, REQ_OP_COPY_DST.
>>Since copy is a composite operation involving src and dst sectors/lba,
>>each needs to be represented by a separate bio to make it compatible
>>with device mapper.
>>We expect caller to take a plug and send bio with source information,
>>followed by bio with destination information.
>>Once the src bio arrives we form a request and wait for destination
>>bio. Upon arrival of destination we merge these two bio's and send
>>corresponding request down to device driver.
>>
>>Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
>>Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
>>---
>>  block/blk-core.c          |  7 +++++++
>>  block/blk-merge.c         | 41 +++++++++++++++++++++++++++++++++++++++
>>  block/blk.h               | 16 +++++++++++++++
>>  block/elevator.h          |  1 +
>>  include/linux/bio.h       |  6 +-----
>>  include/linux/blk_types.h | 10 ++++++++++
>>  6 files changed, 76 insertions(+), 5 deletions(-)
>>
>Having two separate bios is okay, and what one would expect.
>What is slightly strange is the merging functionality;
>That could do with some more explanation why this approach was taken.

Combining the two bios is necessary to form a single copy command.
And that's what we do by putting two bios in the single request, and send
this down to the driver.
This helps to avoid putting payload (token) in the request.
This change came as a feedback, as sending payload that is not data to the
device is considered a bad idea [1].
Current approach is similar to bio merging in discard.

>And also some checks in the merging code to avoid merging non-copy 
>offload  bios.
blk_copy_offload_mergable takes care of this, as this checks REQ_OP_COPY_SRC
and REQ_OP_COPY_DST

[1] https://lore.kernel.org/lkml/20230605121732.28468-1-nj.shetty@samsung.com/T/#mfa7104c5f5f8579cd20f668a9d5e83b4ac8bc58a
 
Thank You,
Nitesh Shetty


[-- Attachment #2: Type: text/plain, Size: 0 bytes --]

Re: [PATCH v15 03/12] block: add copy offload support

[Nitesh Shetty]

[-- Attachment #1: Type: text/plain, Size: 671 bytes --]

On 07/09/23 07:49AM, Hannes Reinecke wrote:
>On 9/6/23 18:38, Nitesh Shetty wrote:
>
>Hmm. That looks a bit odd. Why do you have to use wait_for_completion?

wait_for_completion is waiting for all the copy IOs to complete,
when caller does not pass endio handler.
Copy IO submissions are still async, as in previous revisions.

>Can't you submit the 'src' bio, and then submit the 'dst' bio from the 
>endio handler of the 'src' bio?
We can't do this with the current bio merging approach.
'src' bio waits for the 'dst' bio to arrive in request layer.
Note that both bio's should be present in request reaching the driver,
to form the copy-cmd.

Thank You,
Nitesh Shetty

[-- Attachment #2: Type: text/plain, Size: 0 bytes --]

Re: [PATCH v15 01/12] block: Introduce queue limits and sysfs for copy-offload support

[Luis Chamberlain]

On Wed, Sep 06, 2023 at 10:08:26PM +0530, Nitesh Shetty wrote:
> Add device limits as sysfs entries,
> 	- copy_max_bytes (RW)
> 	- copy_max_hw_bytes (RO)
> 
> Above limits help to split the copy payload in block layer.
> copy_max_bytes: maximum total length of copy in single payload.
> copy_max_hw_bytes: Reflects the device supported maximum limit.
> 
> Reviewed-by: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
> Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
> Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>

Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>

  Luis

Re: [PATCH v15 03/12] block: add copy offload support

[Hannes Reinecke]

On 9/7/23 09:16, Nitesh Shetty wrote:
> On 07/09/23 07:49AM, Hannes Reinecke wrote:
>> On 9/6/23 18:38, Nitesh Shetty wrote:
>>
>> Hmm. That looks a bit odd. Why do you have to use wait_for_completion?
> 
> wait_for_completion is waiting for all the copy IOs to complete,
> when caller does not pass endio handler.
> Copy IO submissions are still async, as in previous revisions.
> 
>> Can't you submit the 'src' bio, and then submit the 'dst' bio from the 
>> endio handler of the 'src' bio?
> We can't do this with the current bio merging approach.
> 'src' bio waits for the 'dst' bio to arrive in request layer.
> Note that both bio's should be present in request reaching the driver,
> to form the copy-cmd.
> 
Hmm. I guess it would be possible, but in the end we can always change
it later once the infrastructure is in.

So:

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman

Re: [PATCH v15 04/12] block: add emulation for copy

[Hannes Reinecke]

On 9/6/23 18:38, Nitesh Shetty wrote:
> For the devices which does not support copy, copy emulation is added.
> It is required for in-kernel users like fabrics, where file descriptor is
> not available and hence they can't use copy_file_range.
> Copy-emulation is implemented by reading from source into memory and
> writing to the corresponding destination.
> Also emulation can be used, if copy offload fails or partially completes.
> At present in kernel user of emulation is NVMe fabrics.
> 
Leave out the last sentence; I really would like to see it enabled for 
SCSI, too (we do have copy offload commands for SCSI ...).

And it raises all the questions which have bogged us down right from the 
start: where is the point in calling copy offload if copy offload is not 
implemented or slower than copying it by hand?
And how can the caller differentiate whether copy offload bring a 
benefit to him?

IOW: wouldn't it be better to return -EOPNOTSUPP if copy offload is not 
available?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman

Re: [PATCH v15 05/12] fs/read_write: Enable copy_file_range for block device.

[Hannes Reinecke]

On 9/6/23 18:38, Nitesh Shetty wrote:
> From: Anuj Gupta <anuj20.g@samsung.com>
> 
> This is a prep patch. Allow copy_file_range to work for block devices.
> Relaxing generic_copy_file_checks allows us to reuse the existing infra,
> instead of adding a new user interface for block copy offload.
> Change generic_copy_file_checks to use ->f_mapping->host for both inode_in
> and inode_out. Allow block device in generic_file_rw_checks.
> 
> Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
> Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
> ---
>   fs/read_write.c | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
> 

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman

Re: [PATCH v15 06/12] fs, block: copy_file_range for def_blk_ops for direct block device

[Hannes Reinecke]

On 9/6/23 18:38, Nitesh Shetty wrote:
> For direct block device opened with O_DIRECT, use copy_file_range to
> issue device copy offload, and fallback to generic_copy_file_range incase
> device copy offload capability is absent or the device files are not open
> with O_DIRECT.
> 
> Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
> Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
> ---
>   block/fops.c | 25 +++++++++++++++++++++++++
>   1 file changed, 25 insertions(+)
> 

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman

Re: [PATCH v15 07/12] nvme: add copy offload support

[Hannes Reinecke]

On 9/6/23 18:38, Nitesh Shetty wrote:
> Current design only supports single source range.
> We receive a request with REQ_OP_COPY_SRC.
> Parse this request which consists of src(1st) and dst(2nd) bios.
> Form a copy command (TP 4065)
> 
> trace event support for nvme_copy_cmd.
> Set the device copy limits to queue limits.
> 
> Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
> Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
> Signed-off-by: Javier González <javier.gonz@samsung.com>
> Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
> ---
>   drivers/nvme/host/constants.c |  1 +
>   drivers/nvme/host/core.c      | 79 +++++++++++++++++++++++++++++++++++
>   drivers/nvme/host/trace.c     | 19 +++++++++
>   include/linux/blkdev.h        |  1 +
>   include/linux/nvme.h          | 43 +++++++++++++++++--
>   5 files changed, 140 insertions(+), 3 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman

Re: [PATCH v15 08/12] nvmet: add copy command support for bdev and file ns

[Hannes Reinecke]

On 9/6/23 18:38, Nitesh Shetty wrote:
> Add support for handling nvme_cmd_copy command on target.
> 
> For bdev-ns if backing device supports copy offload we call device copy
> offload (blkdev_copy_offload).
> In case of partial completion from above or absence of device copy offload
> capability, we fallback to copy emulation (blkdev_copy_emulation)
> 
> For file-ns we call vfs_copy_file_range to service our request.
> 
> Currently target always shows copy capability by setting
> NVME_CTRL_ONCS_COPY in controller ONCS.
> 
> loop target has copy support, which can be used to test copy offload.
> trace event support for nvme_cmd_copy.
> 
> Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
> Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
> ---
>   drivers/nvme/target/admin-cmd.c   |  9 ++-
>   drivers/nvme/target/io-cmd-bdev.c | 97 +++++++++++++++++++++++++++++++
>   drivers/nvme/target/io-cmd-file.c | 50 ++++++++++++++++
>   drivers/nvme/target/nvmet.h       |  4 ++
>   drivers/nvme/target/trace.c       | 19 ++++++
>   5 files changed, 177 insertions(+), 2 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman

Re: [PATCH v15 09/12] dm: Add support for copy offload

[Hannes Reinecke]

On 9/6/23 18:38, Nitesh Shetty wrote:
> Before enabling copy for dm target, check if underlying devices and
> dm target support copy. Avoid split happening inside dm target.
> Fail early if the request needs split, currently splitting copy
> request is not supported.
> 
And here is where I would have expected the emulation to take place;
didn't you have it in one of the earlier iterations?
After all, device-mapper already has the infrastructure for copying
data between devices, so adding a copy-offload emulation for 
device-mapper should be trivial.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman

Re: [PATCH v15 10/12] dm: Enable copy offload for dm-linear target

[Hannes Reinecke]

On 9/6/23 18:38, Nitesh Shetty wrote:
> Setting copy_offload_supported flag to enable offload.
> 
> Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
> ---
>   drivers/md/dm-linear.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
> index f4448d520ee9..1d1ee30bbefb 100644
> --- a/drivers/md/dm-linear.c
> +++ b/drivers/md/dm-linear.c
> @@ -62,6 +62,7 @@ static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv)
>   	ti->num_discard_bios = 1;
>   	ti->num_secure_erase_bios = 1;
>   	ti->num_write_zeroes_bios = 1;
> +	ti->copy_offload_supported = 1;
>   	ti->private = lc;
>   	return 0;
>   
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman

Re: [PATCH v15 11/12] null: Enable trace capability for null block

[Hannes Reinecke]

On 9/6/23 18:38, Nitesh Shetty wrote:
> This is a prep patch to enable copy trace capability.
> At present only zoned null_block is using trace, so we decoupled trace
> and zoned dependency to make it usable in null_blk driver also.
> 
> Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
> Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
> ---
>   drivers/block/null_blk/Makefile | 2 --
>   drivers/block/null_blk/main.c   | 3 +++
>   drivers/block/null_blk/trace.h  | 2 ++
>   drivers/block/null_blk/zoned.c  | 1 -
>   4 files changed, 5 insertions(+), 3 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman

Re: [PATCH v15 12/12] null_blk: add support for copy offload

[Hannes Reinecke]

On 9/6/23 18:38, Nitesh Shetty wrote:
> Implementation is based on existing read and write infrastructure.
> copy_max_bytes: A new configfs and module parameter is introduced, which
> can be used to set hardware/driver supported maximum copy limit.
> Only request based queue mode will support for copy offload.
> Added tracefs support to copy IO tracing.
> 
> Suggested-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
> Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
> Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
> Signed-off-by: Vincent Fu <vincent.fu@samsung.com>
> ---
>   Documentation/block/null_blk.rst  |  5 ++
>   drivers/block/null_blk/main.c     | 97 ++++++++++++++++++++++++++++++-
>   drivers/block/null_blk/null_blk.h |  1 +
>   drivers/block/null_blk/trace.h    | 23 ++++++++
>   4 files changed, 123 insertions(+), 3 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman

Re: [PATCH v15 09/12] dm: Add support for copy offload

[Nitesh Shetty]

[-- Attachment #1: Type: text/plain, Size: 958 bytes --]

On Fri, Sep 08, 2023 at 08:13:37AM +0200, Hannes Reinecke wrote:
> On 9/6/23 18:38, Nitesh Shetty wrote:
> > Before enabling copy for dm target, check if underlying devices and
> > dm target support copy. Avoid split happening inside dm target.
> > Fail early if the request needs split, currently splitting copy
> > request is not supported.
> > 
> And here is where I would have expected the emulation to take place;
> didn't you have it in one of the earlier iterations?

No, but it was the other way round.
In dm-kcopyd we used device offload, if that was possible, before using default
dm-mapper copy. It was dropped in the current series,
to streamline the patches and make the series easier to review.

> After all, device-mapper already has the infrastructure for copying
> data between devices, so adding a copy-offload emulation for device-mapper
> should be trivial.
I did not understand this, can you please elaborate ?

Thank you,
Nitesh Shetty

[-- Attachment #2: Type: text/plain, Size: 0 bytes --]

Re: [PATCH v15 04/12] block: add emulation for copy

[Nitesh Shetty]

[-- Attachment #1: Type: text/plain, Size: 1445 bytes --]

On Fri, Sep 08, 2023 at 08:06:38AM +0200, Hannes Reinecke wrote:
> On 9/6/23 18:38, Nitesh Shetty wrote:
> > For the devices which does not support copy, copy emulation is added.
> > It is required for in-kernel users like fabrics, where file descriptor is
> > not available and hence they can't use copy_file_range.
> > Copy-emulation is implemented by reading from source into memory and
> > writing to the corresponding destination.
> > Also emulation can be used, if copy offload fails or partially completes.
> > At present in kernel user of emulation is NVMe fabrics.
> > 
> Leave out the last sentence; I really would like to see it enabled for SCSI,
> too (we do have copy offload commands for SCSI ...).
> 
Sure, will do that

> And it raises all the questions which have bogged us down right from the
> start: where is the point in calling copy offload if copy offload is not
> implemented or slower than copying it by hand?
> And how can the caller differentiate whether copy offload bring a benefit to
> him?
> 
> IOW: wouldn't it be better to return -EOPNOTSUPP if copy offload is not
> available?

Present approach treats copy as a background operation and the idea is to
maximize the chances of achieving copy by falling back to emulation.
Having said that, it should be possible to return -EOPNOTSUPP,
in case of offload IO failure or device not supporting offload.
We will update this in next version.

Thank you,
Nitesh Shetty

[-- Attachment #2: Type: text/plain, Size: 0 bytes --]

Re: [PATCH v15 04/12] block: add emulation for copy

[Hannes Reinecke]

On 9/11/23 09:09, Nitesh Shetty wrote:
> On Fri, Sep 08, 2023 at 08:06:38AM +0200, Hannes Reinecke wrote:
>> On 9/6/23 18:38, Nitesh Shetty wrote:
>>> For the devices which does not support copy, copy emulation is added.
>>> It is required for in-kernel users like fabrics, where file descriptor is
>>> not available and hence they can't use copy_file_range.
>>> Copy-emulation is implemented by reading from source into memory and
>>> writing to the corresponding destination.
>>> Also emulation can be used, if copy offload fails or partially completes.
>>> At present in kernel user of emulation is NVMe fabrics.
>>>
>> Leave out the last sentence; I really would like to see it enabled for SCSI,
>> too (we do have copy offload commands for SCSI ...).
>>
> Sure, will do that
> 
>> And it raises all the questions which have bogged us down right from the
>> start: where is the point in calling copy offload if copy offload is not
>> implemented or slower than copying it by hand?
>> And how can the caller differentiate whether copy offload bring a benefit to
>> him?
>>
>> IOW: wouldn't it be better to return -EOPNOTSUPP if copy offload is not
>> available?
> 
> Present approach treats copy as a background operation and the idea is to
> maximize the chances of achieving copy by falling back to emulation.
> Having said that, it should be possible to return -EOPNOTSUPP,
> in case of offload IO failure or device not supporting offload.
> We will update this in next version.
> 
That is also what I meant with my comments to patch 09/12: I don't see 
it as a benefit to _always_ fall back to a generic copy-offload 
emulation. After all, that hardly brings any benefit.
Where I do see a benefit is to tie in the generic copy-offload 
_infrastructure_ to existing mechanisms (like dm-kcopyd).
But if there is no copy-offload infrastructure available then we really 
should return -EOPNOTSUPP as it really is not supported.

In the end, copy offload is not a command which 'always works'.
It's a command which _might_ deliver benefits (ie better performance) if 
dedicated implementations are available and certain parameters are met. 
If not then copy offload is not the best choice, and applications will 
need to be made aware of that.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman

Re: [PATCH v15 09/12] dm: Add support for copy offload

[Hannes Reinecke]

On 9/11/23 09:07, Nitesh Shetty wrote:
> On Fri, Sep 08, 2023 at 08:13:37AM +0200, Hannes Reinecke wrote:
>> On 9/6/23 18:38, Nitesh Shetty wrote:
>>> Before enabling copy for dm target, check if underlying devices and
>>> dm target support copy. Avoid split happening inside dm target.
>>> Fail early if the request needs split, currently splitting copy
>>> request is not supported.
>>>
>> And here is where I would have expected the emulation to take place;
>> didn't you have it in one of the earlier iterations?
> 
> No, but it was the other way round.
> In dm-kcopyd we used device offload, if that was possible, before using default
> dm-mapper copy. It was dropped in the current series,
> to streamline the patches and make the series easier to review.
> 
>> After all, device-mapper already has the infrastructure for copying
>> data between devices, so adding a copy-offload emulation for device-mapper
>> should be trivial.
> I did not understand this, can you please elaborate ?
> 
Please see my comments to patch 04.
We should only implement copy-offload if there is a dedicated 
infrastructure in place. But we should not have a 'generic' copy-offload 
emulation.
Problem is that 'real' copy-offload functionalities (ie for NVMe or 
SCSI) are riddled with corner-cases where copy-offload does _not_ work,
and where commands might fail if particular conditions are not met.
Falling back to a generic implementation will cause applications to 
assume that copy-offload worked, and that it gained performance as
the application just had to issue a single command.
Whereas in fact the opposite is true; it wasn't a single command, and 
the application might have performed better by issuing the commands
itself.
Returning -EOPNOTSUPP in these cases will inform the application that 
the attempt didn't work, and that it will have to fall back to the
'normal' copy.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman

Re: [PATCH v15 04/12] block: add emulation for copy

[Nitesh Shetty]

[-- Attachment #1: Type: text/plain, Size: 2896 bytes --]

On 11/09/23 09:39AM, Hannes Reinecke wrote:
>On 9/11/23 09:09, Nitesh Shetty wrote:
>>On Fri, Sep 08, 2023 at 08:06:38AM +0200, Hannes Reinecke wrote:
>>>On 9/6/23 18:38, Nitesh Shetty wrote:
>>>>For the devices which does not support copy, copy emulation is added.
>>>>It is required for in-kernel users like fabrics, where file descriptor is
>>>>not available and hence they can't use copy_file_range.
>>>>Copy-emulation is implemented by reading from source into memory and
>>>>writing to the corresponding destination.
>>>>Also emulation can be used, if copy offload fails or partially completes.
>>>>At present in kernel user of emulation is NVMe fabrics.
>>>>
>>>Leave out the last sentence; I really would like to see it enabled for SCSI,
>>>too (we do have copy offload commands for SCSI ...).
>>>
>>Sure, will do that
>>
>>>And it raises all the questions which have bogged us down right from the
>>>start: where is the point in calling copy offload if copy offload is not
>>>implemented or slower than copying it by hand?
>>>And how can the caller differentiate whether copy offload bring a benefit to
>>>him?
>>>
>>>IOW: wouldn't it be better to return -EOPNOTSUPP if copy offload is not
>>>available?
>>
>>Present approach treats copy as a background operation and the idea is to
>>maximize the chances of achieving copy by falling back to emulation.
>>Having said that, it should be possible to return -EOPNOTSUPP,
>>in case of offload IO failure or device not supporting offload.
>>We will update this in next version.
>>
>That is also what I meant with my comments to patch 09/12: I don't see 
>it as a benefit to _always_ fall back to a generic copy-offload 
>emulation. After all, that hardly brings any benefit.

Agreed, we will correct this by returning error to user in case copy offload
fails, instead of falling back to block layer emulation.

We do need block layer emulation for fabrics, where we call emulation
if target doesn't support offload. In fabrics scenarios sending
offload command from host and achieve copy using block layer
emulation on target is better than sending read+write from host.

>Where I do see a benefit is to tie in the generic copy-offload 
>_infrastructure_ to existing mechanisms (like dm-kcopyd).
>But if there is no copy-offload infrastructure available then we 
>really should return -EOPNOTSUPP as it really is not supported.
>
Agreed, we will add this in next phase, once present series gets merged.

>In the end, copy offload is not a command which 'always works'.
>It's a command which _might_ deliver benefits (ie better performance) 
>if dedicated implementations are available and certain parameters are 
>met. If not then copy offload is not the best choice, and applications 
>will need to be made aware of that.

Agreed. We will leave the choice to user, to use either block layer offload
or emulation.


Thank you,
Nitesh Shetty

[-- Attachment #2: Type: text/plain, Size: 0 bytes --]