[dm-devel] [PATCH v6 3/9] block: add emulation for copy

[Nitesh Shetty <nj.shetty@samsung.com>]

For the devices which does not support copy, copy emulation is
added. Copy-emulation is implemented by reading from source ranges
into memory and writing to the corresponding destination asynchronously.
For zoned device we maintain a linked list of read submission and try to
submit corresponding write in same order.
Also emulation is used, if copy offload fails or partially completes.

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        | 241 ++++++++++++++++++++++++++++++++++++++++-
 block/blk-map.c        |   4 +-
 include/linux/blkdev.h |   3 +
 3 files changed, 245 insertions(+), 3 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 2ce3c872ca49..43b1d0ef5732 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -428,6 +428,239 @@ static inline int blk_copy_sanity_check(struct block_device *src_bdev,
 	return 0;
 }
 
+static void *blk_alloc_buf(sector_t req_size, sector_t *alloc_size,
+		gfp_t gfp_mask)
+{
+	int min_size = PAGE_SIZE;
+	void *buf;
+
+	while (req_size >= min_size) {
+		buf = kvmalloc(req_size, gfp_mask);
+		if (buf) {
+			*alloc_size = req_size;
+			return buf;
+		}
+		/* retry half the requested size */
+		req_size >>= 1;
+	}
+
+	return NULL;
+}
+
+static void blk_copy_emulate_write_end_io(struct bio *bio)
+{
+	struct copy_ctx *ctx = bio->bi_private;
+	struct cio *cio = ctx->cio;
+	sector_t clen;
+	int ri = ctx->range_idx;
+
+	if (bio->bi_status) {
+		cio->io_err = blk_status_to_errno(bio->bi_status);
+		clen = (bio->bi_iter.bi_sector << SECTOR_SHIFT) -
+			cio->ranges[ri].dst;
+		cio->ranges[ri].comp_len = min_t(sector_t, clen,
+				cio->ranges[ri].comp_len);
+	}
+	kvfree(page_address(bio->bi_io_vec[0].bv_page));
+	bio_map_kern_endio(bio);
+	if (atomic_dec_and_test(&ctx->refcount))
+		kfree(ctx);
+	if (atomic_dec_and_test(&cio->refcount)) {
+		if (cio->endio) {
+			cio->endio(cio->private, cio->io_err);
+			kfree(cio);
+		} else
+			blk_wake_io_task(cio->waiter);
+	}
+}
+
+static void blk_copy_emulate_read_end_io(struct bio *read_bio)
+{
+	struct copy_ctx *ctx = read_bio->bi_private;
+	struct cio *cio = ctx->cio;
+	sector_t clen;
+	int ri = ctx->range_idx;
+	unsigned long flags;
+
+	if (read_bio->bi_status) {
+		cio->io_err = blk_status_to_errno(read_bio->bi_status);
+		goto err_rw_bio;
+	}
+
+	/* For zoned device, we check if completed bio is first entry in linked
+	 * list,
+	 * if yes, we start the worker to submit write bios.
+	 * if not, then we just update status of bio in ctx,
+	 * once the worker gets scheduled, it will submit writes for all
+	 * the consecutive REQ_COPY_READ_COMPLETE bios.
+	 */
+	if (bdev_is_zoned(ctx->write_bio->bi_bdev)) {
+		spin_lock_irqsave(&cio->list_lock, flags);
+		ctx->status = REQ_COPY_READ_COMPLETE;
+		if (ctx == list_first_entry(&cio->list,
+					struct copy_ctx, list)) {
+			spin_unlock_irqrestore(&cio->list_lock, flags);
+			schedule_work(&ctx->dispatch_work);
+			goto free_read_bio;
+		}
+		spin_unlock_irqrestore(&cio->list_lock, flags);
+	} else
+		schedule_work(&ctx->dispatch_work);
+
+free_read_bio:
+	kfree(read_bio);
+
+	return;
+
+err_rw_bio:
+	clen = (read_bio->bi_iter.bi_sector << SECTOR_SHIFT) -
+					cio->ranges[ri].src;
+	cio->ranges[ri].comp_len = min_t(sector_t, clen,
+					cio->ranges[ri].comp_len);
+	__free_page(read_bio->bi_io_vec[0].bv_page);
+	bio_map_kern_endio(read_bio);
+	if (atomic_dec_and_test(&ctx->refcount))
+		kfree(ctx);
+	if (atomic_dec_and_test(&cio->refcount)) {
+		if (cio->endio) {
+			cio->endio(cio->private, cio->io_err);
+			kfree(cio);
+		} else
+			blk_wake_io_task(cio->waiter);
+	}
+}
+
+/*
+ * If native copy offload feature is absent, this function tries to emulate,
+ * by copying data from source to a temporary buffer and from buffer to
+ * destination device.
+ */
+static int blk_copy_emulate(struct block_device *src_bdev,
+		struct block_device *dst_bdev, struct range_entry *ranges,
+		int nr, cio_iodone_t end_io, void *private, gfp_t gfp_mask)
+{
+	struct request_queue *sq = bdev_get_queue(src_bdev);
+	struct request_queue *dq = bdev_get_queue(dst_bdev);
+	struct bio *read_bio, *write_bio;
+	void *buf = NULL;
+	struct copy_ctx *ctx;
+	struct cio *cio;
+	sector_t src, dst, offset, buf_len, req_len, rem = 0;
+	int ri = 0, ret = 0;
+	unsigned long flags;
+	sector_t max_src_hw_len = min_t(unsigned int, queue_max_hw_sectors(sq),
+			queue_max_segments(sq) << (PAGE_SHIFT - SECTOR_SHIFT))
+			<< SECTOR_SHIFT;
+	sector_t max_dst_hw_len = min_t(unsigned int, queue_max_hw_sectors(dq),
+			queue_max_segments(dq) << (PAGE_SHIFT - SECTOR_SHIFT))
+			<< SECTOR_SHIFT;
+	sector_t max_hw_len = min_t(unsigned int,
+			max_src_hw_len, max_dst_hw_len);
+
+	cio = kzalloc(sizeof(struct cio), GFP_KERNEL);
+	if (!cio)
+		return -ENOMEM;
+	cio->ranges = ranges;
+	atomic_set(&cio->refcount, 1);
+	cio->waiter = current;
+	cio->endio = end_io;
+	cio->private = private;
+
+	if (bdev_is_zoned(dst_bdev)) {
+		INIT_LIST_HEAD(&cio->list);
+		spin_lock_init(&cio->list_lock);
+	}
+
+	for (ri = 0; ri < nr; ri++) {
+		offset = ranges[ri].comp_len;
+		src = ranges[ri].src + offset;
+		dst = ranges[ri].dst + offset;
+		/* If IO fails, we truncate comp_len */
+		ranges[ri].comp_len = ranges[ri].len;
+
+		for (rem = ranges[ri].len - offset; rem > 0; rem -= buf_len) {
+			req_len = min_t(int, max_hw_len, rem);
+
+			buf = blk_alloc_buf(req_len, &buf_len, gfp_mask);
+			if (!buf) {
+				ret = -ENOMEM;
+				goto err_alloc_buf;
+			}
+
+			ctx = kzalloc(sizeof(struct copy_ctx), gfp_mask);
+			if (!ctx) {
+				ret = -ENOMEM;
+				goto err_ctx;
+			}
+
+			read_bio = bio_map_kern(sq, buf, buf_len, gfp_mask);
+			if (IS_ERR(read_bio)) {
+				ret = PTR_ERR(read_bio);
+				goto err_read_bio;
+			}
+
+			write_bio = bio_map_kern(dq, buf, buf_len, gfp_mask);
+			if (IS_ERR(write_bio)) {
+				ret = PTR_ERR(write_bio);
+				goto err_write_bio;
+			}
+
+			ctx->cio = cio;
+			ctx->range_idx = ri;
+			ctx->write_bio = write_bio;
+			atomic_set(&ctx->refcount, 1);
+
+			read_bio->bi_iter.bi_sector = src >> SECTOR_SHIFT;
+			read_bio->bi_iter.bi_size = buf_len;
+			read_bio->bi_opf = REQ_OP_READ | REQ_SYNC;
+			bio_set_dev(read_bio, src_bdev);
+			read_bio->bi_end_io = blk_copy_emulate_read_end_io;
+			read_bio->bi_private = ctx;
+
+			write_bio->bi_iter.bi_size = buf_len;
+			write_bio->bi_opf = REQ_OP_WRITE | REQ_SYNC;
+			bio_set_dev(write_bio, dst_bdev);
+			write_bio->bi_end_io = blk_copy_emulate_write_end_io;
+			write_bio->bi_iter.bi_sector = dst >> SECTOR_SHIFT;
+			write_bio->bi_private = ctx;
+
+			if (bdev_is_zoned(dst_bdev)) {
+				INIT_WORK(&ctx->dispatch_work,
+					blk_zoned_copy_dispatch_work_fn);
+				INIT_LIST_HEAD(&ctx->list);
+				spin_lock_irqsave(&cio->list_lock, flags);
+				ctx->status = REQ_COPY_READ_PROGRESS;
+				list_add_tail(&ctx->list, &cio->list);
+				spin_unlock_irqrestore(&cio->list_lock, flags);
+			} else
+				INIT_WORK(&ctx->dispatch_work,
+					blk_copy_dispatch_work_fn);
+
+			atomic_inc(&cio->refcount);
+			submit_bio(read_bio);
+
+			src += buf_len;
+			dst += buf_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:
+	kvfree(buf);
+err_alloc_buf:
+	ranges[ri].comp_len -= min_t(sector_t,
+			ranges[ri].comp_len, (ranges[ri].len - rem));
+
+	cio->io_err = ret;
+	return cio_await_completion(cio);
+}
+
 static inline bool blk_check_copy_offload(struct request_queue *src_q,
 		struct request_queue *dst_q)
 {
@@ -460,15 +693,21 @@ int blkdev_issue_copy(struct block_device *src_bdev,
 	struct request_queue *src_q = bdev_get_queue(src_bdev);
 	struct request_queue *dst_q = bdev_get_queue(dst_bdev);
 	int ret = -EINVAL;
+	bool offload = false;
 
 	ret = blk_copy_sanity_check(src_bdev, dst_bdev, ranges, nr);
 	if (ret)
 		return ret;
 
-	if (blk_check_copy_offload(src_q, dst_q))
+	offload = blk_check_copy_offload(src_q, dst_q);
+	if (offload)
 		ret = blk_copy_offload(src_bdev, dst_bdev, ranges, nr,
 				end_io, private, gfp_mask);
 
+	if (ret || !offload)
+		ret = blk_copy_emulate(src_bdev, dst_bdev, ranges, nr,
+				end_io, private, gfp_mask);
+
 	return ret;
 }
 EXPORT_SYMBOL_GPL(blkdev_issue_copy);
diff --git a/block/blk-map.c b/block/blk-map.c
index 19940c978c73..bcf8db2b75f1 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -363,7 +363,7 @@ static void bio_invalidate_vmalloc_pages(struct bio *bio)
 #endif
 }
 
-static void bio_map_kern_endio(struct bio *bio)
+void bio_map_kern_endio(struct bio *bio)
 {
 	bio_invalidate_vmalloc_pages(bio);
 	bio_uninit(bio);
@@ -380,7 +380,7 @@ static void bio_map_kern_endio(struct bio *bio)
  *	Map the kernel address into a bio suitable for io to a block
  *	device. Returns an error pointer in case of error.
  */
-static struct bio *bio_map_kern(struct request_queue *q, void *data,
+struct bio *bio_map_kern(struct request_queue *q, void *data,
 		unsigned int len, gfp_t gfp_mask)
 {
 	unsigned long kaddr = (unsigned long)data;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 48e9160b7195..c5621550e5b4 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1066,6 +1066,9 @@ int blkdev_issue_secure_erase(struct block_device *bdev, sector_t sector,
 int blkdev_issue_copy(struct block_device *src_bdev,
 		struct block_device *dst_bdev, struct range_entry *ranges,
 		int nr, cio_iodone_t end_io, void *private, gfp_t gfp_mask);
+struct bio *bio_map_kern(struct request_queue *q, void *data, unsigned int len,
+		gfp_t gfp_mask);
+void bio_map_kern_endio(struct bio *bio);
 
 #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

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