[PATCH 09/19] btrfs: pass the iomap bio to btrfs_submit_bio

[Christoph Hellwig <hch@lst.de>]

Now that btrfs_submit_bio splits the bio when crossing stripe boundaries,
there is no need for the higher level code to do that manually.

For direct I/O this is really helpful, as btrfs_submit_io can now simply
take the bio allocated by iomap and send it on to btrfs_submit_bio
instead of allocating clones.

For that to work, the bio embedded into struct btrfs_dio_private needs to
become a full btrfs_bio as expected by btrfs_submit_bio.

With this change there is a single work item to offload the entire iomap
bio so the heuristics to skip async processing for bios that were split
isn't needed anymore either.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
---
 fs/btrfs/bio.c   |  19 +-----
 fs/btrfs/bio.h   |   6 +-
 fs/btrfs/inode.c | 161 ++++++++++-------------------------------------
 3 files changed, 36 insertions(+), 150 deletions(-)

diff --git a/fs/btrfs/bio.c b/fs/btrfs/bio.c
index 393fe453fb4876..f5e677588df07b 100644
--- a/fs/btrfs/bio.c
+++ b/fs/btrfs/bio.c
@@ -31,7 +31,7 @@ struct btrfs_failed_bio {
  * Initialize a btrfs_bio structure.  This skips the embedded bio itself as it
  * is already initialized by the block layer.
  */
-static void btrfs_bio_init(struct btrfs_bio *bbio, struct btrfs_inode *inode,
+void btrfs_bio_init(struct btrfs_bio *bbio, struct btrfs_inode *inode,
 			   btrfs_bio_end_io_t end_io, void *private)
 {
 	memset(bbio, 0, offsetof(struct btrfs_bio, bio));
@@ -59,23 +59,6 @@ struct bio *btrfs_bio_alloc(unsigned int nr_vecs, blk_opf_t opf,
 	return bio;
 }
 
-struct bio *btrfs_bio_clone_partial(struct bio *orig, u64 offset, u64 size,
-				    struct btrfs_inode *inode,
-				    btrfs_bio_end_io_t end_io, void *private)
-{
-	struct bio *bio;
-	struct btrfs_bio *bbio;
-
-	ASSERT(offset <= UINT_MAX && size <= UINT_MAX);
-
-	bio = bio_alloc_clone(orig->bi_bdev, orig, GFP_NOFS, &btrfs_bioset);
-	bbio = btrfs_bio(bio);
-	btrfs_bio_init(bbio, inode, end_io, private);
-
-	bio_trim(bio, offset >> 9, size >> 9);
-	return bio;
-}
-
 static struct bio *btrfs_split_bio(struct bio *orig, u64 map_length)
 {
 	struct btrfs_bio *orig_bbio = btrfs_bio(orig);
diff --git a/fs/btrfs/bio.h b/fs/btrfs/bio.h
index 7c50f757cf5106..5acbcc18026d52 100644
--- a/fs/btrfs/bio.h
+++ b/fs/btrfs/bio.h
@@ -73,13 +73,11 @@ static inline struct btrfs_bio *btrfs_bio(struct bio *bio)
 int __init btrfs_bioset_init(void);
 void __cold btrfs_bioset_exit(void);
 
+void btrfs_bio_init(struct btrfs_bio *bbio, struct btrfs_inode *inode,
+		    btrfs_bio_end_io_t end_io, void *private);
 struct bio *btrfs_bio_alloc(unsigned int nr_vecs, blk_opf_t opf,
 			    struct btrfs_inode *inode,
 			    btrfs_bio_end_io_t end_io, void *private);
-struct bio *btrfs_bio_clone_partial(struct bio *orig, u64 offset, u64 size,
-				    struct btrfs_inode *inode,
-				    btrfs_bio_end_io_t end_io, void *private);
-
 
 static inline void btrfs_bio_end_io(struct btrfs_bio *bbio, blk_status_t status)
 {
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 8f768863cbebbc..5e73f571b57ce9 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -84,24 +84,12 @@ struct btrfs_dio_data {
 };
 
 struct btrfs_dio_private {
-	struct btrfs_inode *inode;
-
-	/*
-	 * Since DIO can use anonymous page, we cannot use page_offset() to
-	 * grab the file offset, thus need a dedicated member for file offset.
-	 */
+	/* Range of I/O */
 	u64 file_offset;
-	/* Used for bio::bi_size */
 	u32 bytes;
 
-	/*
-	 * References to this structure. There is one reference per in-flight
-	 * bio plus one while we're still setting up.
-	 */
-	refcount_t refs;
-
 	/* This must be last */
-	struct bio bio;
+	struct btrfs_bio bbio;
 };
 
 static struct bio_set btrfs_dio_bioset;
@@ -7765,131 +7753,48 @@ static int btrfs_dio_iomap_end(struct inode *inode, loff_t pos, loff_t length,
 	return ret;
 }
 
-static void btrfs_dio_private_put(struct btrfs_dio_private *dip)
+static void btrfs_dio_end_io(struct btrfs_bio *bbio)
 {
-	/*
-	 * This implies a barrier so that stores to dio_bio->bi_status before
-	 * this and loads of dio_bio->bi_status after this are fully ordered.
-	 */
-	if (!refcount_dec_and_test(&dip->refs))
-		return;
-
-	if (btrfs_op(&dip->bio) == BTRFS_MAP_WRITE) {
-		btrfs_mark_ordered_io_finished(dip->inode, NULL,
-					       dip->file_offset, dip->bytes,
-					       !dip->bio.bi_status);
-	} else {
-		unlock_extent(&dip->inode->io_tree,
-			      dip->file_offset,
-			      dip->file_offset + dip->bytes - 1, NULL);
-	}
-
-	bio_endio(&dip->bio);
-}
-
-static void btrfs_end_dio_bio(struct btrfs_bio *bbio)
-{
-	struct btrfs_dio_private *dip = bbio->private;
+	struct btrfs_dio_private *dip =
+		container_of(bbio, struct btrfs_dio_private, bbio);
+	struct btrfs_inode *inode = bbio->inode;
 	struct bio *bio = &bbio->bio;
-	blk_status_t err = bio->bi_status;
 
-	if (err) {
-		btrfs_warn(dip->inode->root->fs_info,
-			   "direct IO failed ino %llu rw %d,%u sector %#Lx len %u err no %d",
-			   btrfs_ino(dip->inode), bio_op(bio),
-			   bio->bi_opf, bio->bi_iter.bi_sector,
-			   bio->bi_iter.bi_size, err);
-		dip->bio.bi_status = err;
+	if (bio->bi_status) {
+		btrfs_warn(inode->root->fs_info,
+			   "direct IO failed ino %llu op 0x%0x offset %#llx len %u err no %d",
+			   btrfs_ino(inode), bio->bi_opf,
+			   dip->file_offset, dip->bytes, bio->bi_status);
 	}
 
-	bio_put(bio);
-	btrfs_dio_private_put(dip);
+	if (btrfs_op(bio) == BTRFS_MAP_WRITE)
+		btrfs_mark_ordered_io_finished(inode, NULL, dip->file_offset,
+					       dip->bytes, !bio->bi_status);
+	else
+		unlock_extent(&inode->io_tree, dip->file_offset,
+			      dip->file_offset + dip->bytes - 1, NULL);
+
+	bbio->bio.bi_private = bbio->private;
+	iomap_dio_bio_end_io(bio);
 }
 
-static void btrfs_submit_direct(const struct iomap_iter *iter,
-		struct bio *dio_bio, loff_t file_offset)
+static void btrfs_dio_submit_io(const struct iomap_iter *iter, struct bio *bio,
+				loff_t file_offset)
 {
+	struct btrfs_bio *bbio = btrfs_bio(bio);
 	struct btrfs_dio_private *dip =
-		container_of(dio_bio, struct btrfs_dio_private, bio);
-	struct inode *inode = iter->inode;
-	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
-	struct bio *bio;
-	u64 start_sector;
-	u64 submit_len;
-	u64 clone_offset = 0;
-	u64 clone_len;
-	u64 logical;
-	int ret;
-	blk_status_t status;
-	struct btrfs_io_geometry geom;
+		container_of(bbio, struct btrfs_dio_private, bbio);
 	struct btrfs_dio_data *dio_data = iter->private;
-	struct extent_map *em = NULL;
 
-	dip->inode = BTRFS_I(inode);
-	dip->file_offset = file_offset;
-	dip->bytes = dio_bio->bi_iter.bi_size;
-	refcount_set(&dip->refs, 1);
+	btrfs_bio_init(bbio, BTRFS_I(iter->inode), btrfs_dio_end_io,
+			bio->bi_private);
+	bbio->file_offset = file_offset;
 
-	start_sector = dio_bio->bi_iter.bi_sector;
-	submit_len = dio_bio->bi_iter.bi_size;
-
-	do {
-		logical = start_sector << 9;
-		em = btrfs_get_chunk_map(fs_info, logical, submit_len);
-		if (IS_ERR(em)) {
-			status = errno_to_blk_status(PTR_ERR(em));
-			em = NULL;
-			goto out_err;
-		}
-		ret = btrfs_get_io_geometry(fs_info, em, btrfs_op(dio_bio),
-					    logical, &geom);
-		if (ret) {
-			status = errno_to_blk_status(ret);
-			goto out_err_em;
-		}
-
-		clone_len = min(submit_len, geom.len);
-		ASSERT(clone_len <= UINT_MAX);
-
-		/*
-		 * This will never fail as it's passing GPF_NOFS and
-		 * the allocation is backed by btrfs_bioset.
-		 */
-		bio = btrfs_bio_clone_partial(dio_bio, clone_offset, clone_len,
-					      BTRFS_I(inode), btrfs_end_dio_bio,
-					      dip);
-		btrfs_bio(bio)->file_offset = file_offset;
-
-		ASSERT(submit_len >= clone_len);
-		submit_len -= clone_len;
-
-		/*
-		 * Increase the count before we submit the bio so we know
-		 * the end IO handler won't happen before we increase the
-		 * count. Otherwise, the dip might get freed before we're
-		 * done setting it up.
-		 *
-		 * We transfer the initial reference to the last bio, so we
-		 * don't need to increment the reference count for the last one.
-		 */
-		if (submit_len > 0)
-			refcount_inc(&dip->refs);
-
-		btrfs_submit_bio(fs_info, bio, 0);
-
-		dio_data->submitted += clone_len;
-		clone_offset += clone_len;
-		start_sector += clone_len >> 9;
-		file_offset += clone_len;
-
-		free_extent_map(em);
-	} while (submit_len > 0);
-	return;
+	dip->file_offset = file_offset;
+	dip->bytes = bio->bi_iter.bi_size;
 
-out_err_em:
-	free_extent_map(em);
-	dio_bio->bi_status = status;
-	btrfs_dio_private_put(dip);
+	dio_data->submitted += bio->bi_iter.bi_size;
+	btrfs_submit_bio(btrfs_sb(iter->inode->i_sb), bio, 0);
 }
 
 static const struct iomap_ops btrfs_dio_iomap_ops = {
@@ -7898,7 +7803,7 @@ static const struct iomap_ops btrfs_dio_iomap_ops = {
 };
 
 static const struct iomap_dio_ops btrfs_dio_ops = {
-	.submit_io		= btrfs_submit_direct,
+	.submit_io		= btrfs_dio_submit_io,
 	.bio_set		= &btrfs_dio_bioset,
 };
 
@@ -8733,7 +8638,7 @@ int __init btrfs_init_cachep(void)
 		goto fail;
 
 	if (bioset_init(&btrfs_dio_bioset, BIO_POOL_SIZE,
-			offsetof(struct btrfs_dio_private, bio),
+			offsetof(struct btrfs_dio_private, bbio.bio),
 			BIOSET_NEED_BVECS))
 		goto fail;
 
-- 
2.35.1