[PATCH RFC 03/11] btrfs: move btrfs_bio_wq_end_io() calls into submit_stripe_bio()

[Qu Wenruo <wqu@suse.com>]

This is a preparation patch for the incoming chunk mapping layer bio
split.

Function btrfs_bio_wq_end_io() is going to remap bio::bi_private and
bio::bi_end_io so that the real endio function will be executed in a
workqueue.

The problem is, remapped bio::bi_private will be a newly allocated
memory, and after the original endio executed, the memory will be freed.

This will not work well with split bio.

So this patch will move all btrfs_bio_wq_end_io() call into one helper
function, btrfs_bio_final_endio_remap(), and call that helper in
submit_stripe_bio().

This refactor also unified all data bio behaviors.

Before this patch, compressed bio no matter if read or write, will
always be delayed using workqueue.

However all data write operations are already delayed using ordered
extent, and all metadata write doesn't need any delayed execution.

Thus this patch will make compressed bios follow the same data
read/write behavior.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/compression.c |  4 +---
 fs/btrfs/disk-io.c     |  9 +--------
 fs/btrfs/inode.c       | 20 +++++---------------
 fs/btrfs/volumes.c     | 41 +++++++++++++++++++++++++++++++++++++----
 fs/btrfs/volumes.h     |  9 ++++++++-
 5 files changed, 52 insertions(+), 31 deletions(-)

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 32da97c3c19d..64f931fc11f0 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -428,10 +428,8 @@ static blk_status_t submit_compressed_bio(struct btrfs_fs_info *fs_info,
 {
 	blk_status_t ret;
 
+	btrfs_bio(bio)->endio_type = BTRFS_WQ_ENDIO_DATA;
 	ASSERT(bio->bi_iter.bi_size);
-	ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
-	if (ret)
-		return ret;
 	ret = btrfs_map_bio(fs_info, bio, mirror_num);
 	return ret;
 }
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 9d66d48945c6..83218d3dae00 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -920,14 +920,7 @@ blk_status_t btrfs_submit_metadata_bio(struct inode *inode, struct bio *bio,
 	blk_status_t ret;
 
 	if (btrfs_op(bio) != BTRFS_MAP_WRITE) {
-		/*
-		 * called for a read, do the setup so that checksum validation
-		 * can happen in the async kernel threads
-		 */
-		ret = btrfs_bio_wq_end_io(fs_info, bio,
-					  BTRFS_WQ_ENDIO_METADATA);
-		if (ret)
-			goto out_w_error;
+		btrfs_bio(bio)->endio_type = BTRFS_WQ_ENDIO_METADATA;
 		ret = btrfs_map_bio(fs_info, bio, mirror_num);
 	} else if (!should_async_write(fs_info, BTRFS_I(inode))) {
 		ret = btree_csum_one_bio(bio);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 91c59b6e279d..8e6901aeeb89 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2510,7 +2510,7 @@ blk_status_t btrfs_submit_data_bio(struct inode *inode, struct bio *bio,
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	struct btrfs_root *root = BTRFS_I(inode)->root;
-	enum btrfs_wq_endio_type metadata = BTRFS_WQ_ENDIO_DATA;
+	enum btrfs_wq_endio_type endio_type = BTRFS_WQ_ENDIO_DATA;
 	blk_status_t ret = 0;
 	int skip_sum;
 	int async = !atomic_read(&BTRFS_I(inode)->sync_writers);
@@ -2519,7 +2519,7 @@ blk_status_t btrfs_submit_data_bio(struct inode *inode, struct bio *bio,
 		   !fs_info->csum_root;
 
 	if (btrfs_is_free_space_inode(BTRFS_I(inode)))
-		metadata = BTRFS_WQ_ENDIO_FREE_SPACE;
+		endio_type = BTRFS_WQ_ENDIO_FREE_SPACE;
 
 	if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
 		struct page *page = bio_first_bvec_all(bio)->bv_page;
@@ -2531,10 +2531,7 @@ blk_status_t btrfs_submit_data_bio(struct inode *inode, struct bio *bio,
 	}
 
 	if (btrfs_op(bio) != BTRFS_MAP_WRITE) {
-		ret = btrfs_bio_wq_end_io(fs_info, bio, metadata);
-		if (ret)
-			goto out;
-
+		btrfs_bio(bio)->endio_type = endio_type;
 		if (bio_flags & EXTENT_BIO_COMPRESSED) {
 			ret = btrfs_submit_compressed_read(inode, bio,
 							   mirror_num,
@@ -8085,10 +8082,6 @@ static blk_status_t submit_dio_repair_bio(struct inode *inode, struct bio *bio,
 
 	BUG_ON(bio_op(bio) == REQ_OP_WRITE);
 
-	ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
-	if (ret)
-		return ret;
-
 	refcount_inc(&dip->refs);
 	ret = btrfs_map_bio(fs_info, bio, mirror_num);
 	if (ret)
@@ -8207,11 +8200,8 @@ static inline blk_status_t btrfs_submit_dio_bio(struct bio *bio,
 	if (async_submit)
 		async_submit = !atomic_read(&BTRFS_I(inode)->sync_writers);
 
-	if (!write) {
-		ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
-		if (ret)
-			goto err;
-	}
+	if (!write)
+		btrfs_bio(bio)->endio_type = BTRFS_WQ_ENDIO_DATA;
 
 	if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
 		goto map;
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 1d40f4fa64a3..f7449bf7a595 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6720,10 +6720,31 @@ static void btrfs_end_bio(struct bio *bio)
 	}
 }
 
-static void submit_stripe_bio(struct btrfs_io_context *bioc, struct bio *bio,
-			      u64 physical, struct btrfs_device *dev)
+/*
+ * Endio remaps which can't handle cloned bio needs to go here.
+ *
+ * Currently it's only btrfs_bio_wq_end_io().
+ */
+static int btrfs_bio_final_endio_remap(struct btrfs_fs_info *fs_info,
+				       struct bio *bio)
+{
+	blk_status_t sts;
+
+	/* For write bio, we don't to put their endio into wq */
+	if (btrfs_op(bio) == BTRFS_MAP_WRITE)
+		return 0;
+
+	sts = btrfs_bio_wq_end_io(fs_info, bio, btrfs_bio(bio)->endio_type);
+	if (sts != BLK_STS_OK)
+		return blk_status_to_errno(sts);
+	return 0;
+}
+
+static int submit_stripe_bio(struct btrfs_io_context *bioc, struct bio *bio,
+			     u64 physical, struct btrfs_device *dev)
 {
 	struct btrfs_fs_info *fs_info = bioc->fs_info;
+	int ret;
 
 	bio->bi_private = bioc;
 	btrfs_bio(bio)->device = dev;
@@ -6750,9 +6771,14 @@ static void submit_stripe_bio(struct btrfs_io_context *bioc, struct bio *bio,
 		dev->devid, bio->bi_iter.bi_size);
 	bio_set_dev(bio, dev->bdev);
 
-	btrfs_bio_counter_inc_noblocked(fs_info);
+	/* Do the final endio remap if needed */
+	ret = btrfs_bio_final_endio_remap(fs_info, bio);
+	if (ret < 0)
+		return ret;
 
+	btrfs_bio_counter_inc_noblocked(fs_info);
 	btrfsic_submit_bio(bio);
+	return ret;
 }
 
 static void bioc_error(struct btrfs_io_context *bioc, struct bio *bio, u64 logical)
@@ -6826,9 +6852,16 @@ static int submit_one_mapped_range(struct btrfs_fs_info *fs_info, struct bio *bi
 		else
 			bio = first_bio;
 
-		submit_stripe_bio(bioc, bio, bioc->stripes[dev_nr].physical, dev);
+		ret = submit_stripe_bio(bioc, bio,
+					bioc->stripes[dev_nr].physical, dev);
+		if (ret < 0)
+			goto error;
 	}
 	return 0;
+error:
+	for (; dev_nr < total_devs; dev_nr++)
+		bioc_error(bioc, first_bio, logical);
+	return ret;
 }
 
 blk_status_t btrfs_map_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 3b8130680749..27d396c152c6 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -328,7 +328,14 @@ struct btrfs_fs_devices {
  * Mostly for btrfs specific features like csum and mirror_num.
  */
 struct btrfs_bio {
-	unsigned int mirror_num;
+	u16 mirror_num;
+
+	/*
+	 * To tell which workqueue the bio's endio should be exeucted in.
+	 *
+	 * Only for read bios.
+	 */
+	u16 endio_type;
 
 	/* @device is for stripe IO submission. */
 	struct btrfs_device *device;
-- 
2.34.0