[PATCH v8 2/9] block: Add copy offload support infrastructure

Anuj Gupta
2023-03-29T08:16:25Z

From: Nitesh Shetty <nj.shetty@samsung.com>

Introduce blkdev_issue_copy which takes similar arguments as
copy_file_range and performs copy offload between two bdevs.
Introduce REQ_COPY copy offload operation flag. Create a read-write
bio pair with a token as payload and submitted to the device in order.
Read request populates token with source specific information which
is then passed with write request.
This design is courtesy Mikulas Patocka's token based copy

Larger copy will be divided, based on max_copy_sectors limit.

Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
---
block/blk-lib.c | 236 ++++++++++++++++++++++++++++++++++++++
block/blk.h | 2 +
include/linux/blk_types.h | 25 ++++
include/linux/blkdev.h | 3 +
4 files changed, 266 insertions(+)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index e59c3069e835..cbc6882d1e7a 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -115,6 +115,242 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
}
EXPORT_SYMBOL(blkdev_issue_discard);

+/*
+ * For synchronous copy offload/emulation, wait and process all in-flight BIOs.
+ * 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 make it through
+ * bio_copy_*_write_end_io. IO errors are propagated through cio->io_error.
+ */
+static int cio_await_completion(struct cio *cio)
+{
+ int ret = 0;
+
+ if (cio->endio)
+ return 0;
+
+ if (atomic_read(&cio->refcount)) {
+ __set_current_state(TASK_UNINTERRUPTIBLE);
+ blk_io_schedule();
+ }
+
+ ret = cio->comp_len;
+ kfree(cio);
+
+ return ret;
+}
+
+static void blk_copy_offload_write_end_io(struct bio *bio)
+{
+ struct copy_ctx *ctx = bio->bi_private;
+ struct cio *cio = ctx->cio;
+ sector_t clen;
+
+ if (bio->bi_status) {
+ clen = (bio->bi_iter.bi_sector << SECTOR_SHIFT) - cio->pos_out;
+ cio->comp_len = min_t(sector_t, clen, cio->comp_len);
+ }
+ __free_page(bio->bi_io_vec[0].bv_page);
+ bio_put(bio);
+
+ kfree(ctx);
+ if (atomic_dec_and_test(&cio->refcount)) {
+ if (cio->endio) {
+ cio->endio(cio->private, cio->comp_len);
+ kfree(cio);
+ } else
+ blk_wake_io_task(cio->waiter);
+ }
+}
+
+static void blk_copy_offload_read_end_io(struct bio *read_bio)
+{
+ struct copy_ctx *ctx = read_bio->bi_private;
+ struct cio *cio = ctx->cio;
+ sector_t clen;
+
+ if (read_bio->bi_status) {
+ clen = (read_bio->bi_iter.bi_sector << SECTOR_SHIFT)
+ - cio->pos_in;
+ cio->comp_len = min_t(sector_t, clen, cio->comp_len);
+ __free_page(read_bio->bi_io_vec[0].bv_page);
+ bio_put(ctx->write_bio);
+ bio_put(read_bio);
+ kfree(ctx);
+ if (atomic_dec_and_test(&cio->refcount)) {
+ if (cio->endio) {
+ cio->endio(cio->private, cio->comp_len);
+ kfree(cio);
+ } else
+ blk_wake_io_task(cio->waiter);
+ }
+ return;
+ }
+
+ schedule_work(&ctx->dispatch_work);
+ bio_put(read_bio);
+}
+
+static void blk_copy_dispatch_work_fn(struct work_struct *work)
+{
+ struct copy_ctx *ctx = container_of(work, struct copy_ctx,
+ dispatch_work);
+
+ submit_bio(ctx->write_bio);
+}
+
+/*
+ * __blk_copy_offload - Use device's native copy offload feature.
+ * we perform copy operation by sending 2 bio.
+ * 1. First we send a read bio with REQ_COPY flag along with a token and source
+ * and length. Once read bio reaches driver layer, device driver adds all the
+ * source info to token and does a fake completion.
+ * 2. Once read operation completes, we issue write with REQ_COPY flag with same
+ * token. In driver layer, token info is used to form a copy offload command.
+ *
+ * returns the length of bytes copied or negative error value
+ */
+static int __blk_copy_offload(struct block_device *bdev_in, loff_t pos_in,
+ struct block_device *bdev_out, loff_t pos_out, size_t len,
+ cio_iodone_t end_io, void *private, gfp_t gfp_mask)
+{
+ struct cio *cio;
+ struct copy_ctx *ctx;
+ struct bio *read_bio, *write_bio;
+ struct page *token;
+ sector_t copy_len;
+ sector_t rem, max_copy_len;
+
+ cio = kzalloc(sizeof(struct cio), GFP_KERNEL);
+ if (!cio)
+ return -ENOMEM;
+ atomic_set(&cio->refcount, 0);
+ cio->waiter = current;
+ cio->endio = end_io;
+ cio->private = private;
+
+ max_copy_len = min(bdev_max_copy_sectors(bdev_in),
+ bdev_max_copy_sectors(bdev_out)) << SECTOR_SHIFT;
+
+ cio->pos_in = pos_in;
+ cio->pos_out = pos_out;
+ cio->comp_len = len;
+ for (rem = len; rem > 0; rem -= copy_len) {
+ copy_len = min(rem, max_copy_len);
+
+ token = alloc_page(gfp_mask);
+ if (unlikely(!token))
+ goto err_token;
+
+ ctx = kzalloc(sizeof(struct copy_ctx), gfp_mask);
+ if (!ctx)
+ goto err_ctx;
+ read_bio = bio_alloc(bdev_in, 1, REQ_OP_READ | REQ_COPY
+ | REQ_SYNC | REQ_NOMERGE, gfp_mask);
+ if (!read_bio)
+ goto err_read_bio;
+ write_bio = bio_alloc(bdev_out, 1, REQ_OP_WRITE
+ | REQ_COPY | REQ_SYNC | REQ_NOMERGE, gfp_mask);
+ if (!write_bio)
+ goto err_write_bio;
+
+ ctx->cio = cio;
+ ctx->write_bio = write_bio;
+ INIT_WORK(&ctx->dispatch_work, blk_copy_dispatch_work_fn);
+
+ __bio_add_page(read_bio, token, PAGE_SIZE, 0);
+ read_bio->bi_iter.bi_size = copy_len;
+ read_bio->bi_iter.bi_sector = pos_in >> SECTOR_SHIFT;
+ read_bio->bi_end_io = blk_copy_offload_read_end_io;
+ read_bio->bi_private = ctx;
+
+ __bio_add_page(write_bio, token, PAGE_SIZE, 0);
+ write_bio->bi_iter.bi_size = copy_len;
+ write_bio->bi_end_io = blk_copy_offload_write_end_io;
+ write_bio->bi_iter.bi_sector = pos_out >> SECTOR_SHIFT;
+ write_bio->bi_private = ctx;
+
+ atomic_inc(&cio->refcount);
+ submit_bio(read_bio);
+ pos_in += copy_len;
+ pos_out += copy_len;
+ }
+
+ /* Wait for completion of all IO's*/
+ return cio_await_completion(cio);
+
+err_write_bio:
+ bio_put(read_bio);
+err_read_bio:
+ kfree(ctx);
+err_ctx:
+ __free_page(token);
+err_token:
+ cio->comp_len = min_t(sector_t, cio->comp_len, (len - rem));
+ return cio_await_completion(cio);
+}
+
+static inline int blk_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 (bdev_read_only(bdev_out))
+ return -EPERM;
+
+ if ((pos_in & align) || (pos_out & align) || (len & align) || !len ||
+ len >= MAX_COPY_TOTAL_LENGTH)
+ return -EINVAL;
+
+ return 0;
+}
+
+static inline bool blk_check_copy_offload(struct request_queue *q_in,
+ struct request_queue *q_out)
+{
+ return blk_queue_copy(q_in) && blk_queue_copy(q_out);
+}
+
+/*
+ * @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
+ * @end_io: end_io function to be called on completion of copy operation,
+ * for synchronous operation this should be NULL
+ * @private: end_io function will be called with this private data, should be
+ * NULL, if operation is synchronous in nature
+ * @gfp_mask: memory allocation flags (for bio_alloc)
+ *
+ * Returns the length of bytes copied or a negative error value
+ *
+ * Description:
+ * Copy source offset from source block device to destination block
+ * device. length of a source range cannot be zero. Max total length of
+ * copy is limited to MAX_COPY_TOTAL_LENGTH
+ */
+int blkdev_issue_copy(struct block_device *bdev_in, loff_t pos_in,
+ struct block_device *bdev_out, loff_t pos_out, size_t len,
+ cio_iodone_t end_io, void *private, gfp_t gfp_mask)
+{
+ struct request_queue *q_in = bdev_get_queue(bdev_in);
+ struct request_queue *q_out = bdev_get_queue(bdev_out);
+ int ret = -EINVAL;
+
+ ret = blk_copy_sanity_check(bdev_in, pos_in, bdev_out, pos_out, len);
+ if (ret)
+ return ret;
+
+ if (blk_check_copy_offload(q_in, q_out))
+ ret = __blk_copy_offload(bdev_in, pos_in, bdev_out, pos_out,
+ len, end_io, private, gfp_mask);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(blkdev_issue_copy);
+
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/block/blk.h b/block/blk.h
index d65d96994a94..684b8fa121db 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -311,6 +311,8 @@ static inline bool bio_may_exceed_limits(struct bio *bio,
break;
}

+ if (unlikely(op_is_copy(bio->bi_opf)))
+ return false;
/*
* All drivers must accept single-segments bios that are <= PAGE_SIZE.
* This is a quick and dirty check that relies on the fact that
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index a0e339ff3d09..7f586c4b9954 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -423,6 +423,7 @@ enum req_flag_bits {
*/
/* for REQ_OP_WRITE_ZEROES: */
__REQ_NOUNMAP, /* do not free blocks when zeroing */
+ __REQ_COPY, /* copy request */

__REQ_NR_BITS, /* stops here */
};
@@ -452,6 +453,7 @@ enum req_flag_bits {

#define REQ_DRV (__force blk_opf_t)(1ULL << __REQ_DRV)
#define REQ_SWAP (__force blk_opf_t)(1ULL << __REQ_SWAP)
+#define REQ_COPY ((__force blk_opf_t)(1ULL << __REQ_COPY))

#define REQ_FAILFAST_MASK \
(REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER)
@@ -478,6 +480,11 @@ 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_COPY);
+}
+
/*
* Check if the bio or request is one that needs special treatment in the
* flush state machine.
@@ -537,4 +544,22 @@ struct blk_rq_stat {
u64 batch;
};

+typedef void (cio_iodone_t)(void *private, int comp_len);
+
+struct cio {
+ struct task_struct *waiter; /* waiting task (NULL if none) */
+ atomic_t refcount;
+ loff_t pos_in;
+ loff_t pos_out;
+ size_t comp_len;
+ cio_iodone_t *endio; /* applicable for async operation */
+ void *private; /* applicable for async operation */
+};
+
+struct copy_ctx {
+ struct cio *cio;
+ struct work_struct dispatch_work;
+ struct bio *write_bio;
+};
+
#endif /* __LINUX_BLK_TYPES_H */
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 200338f2ec2e..1bb43697d43d 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1054,6 +1054,9 @@ 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);
+int blkdev_issue_copy(struct block_device *bdev_in, loff_t pos_in,
+ struct block_device *bdev_out, loff_t pos_out, size_t len,
+ cio_iodone_t end_io, 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