btrfs: handle bio_split() error

From: Johannes Thumshirn <[email protected]>

Now that bio_split() can return errors, add error handling for it in btrfs_split_bio() and ultimately btrfs_submit_chunk().

Signed-off-by Johannes Thumshirn <[email protected]>

---

This is based on top of John Garry's series "bio_split() error handling rework" explicitly on the patch titled "block: Rework bio_split() return value", which are as of now (Tue Oct 29 10:02:16 2024) not yet merged into any tree.

Changes to v1:
- convert ERR_PTR to blk_status_t
- correctly fail already split bbios

---
  fs/btrfs/bio.c | 16 ++++++++++++----
  1 file changed, 12 insertions(+), 4 deletions(-)

fs/btrfs/bio.c +3 -0

index 1f216d07eff6..d2cfef5e4d4a 100644
@@ -81,6 +81,9 @@ static struct btrfs_bio *btrfs_split_bio(struct btrfs_fs_info *fs_info,
 
  	bio = bio_split(&orig_bbio->bio, map_length >> SECTOR_SHIFT, GFP_NOFS,
  			&btrfs_clone_bioset);
+	if (IS_ERR(bio))
+		return ERR_CAST(bio);
+
  	bbio = btrfs_bio(bio);
  	btrfs_bio_init(bbio, fs_info, NULL, orig_bbio);
  	bbio->inode = orig_bbio->inode;

fs/btrfs/bio.c +7 -4

+			goto fail;
+		}
  		bio = &bbio->bio;
  	}
 

@@ -698,7 +705,7 @@ static bool btrfs_submit_chunk(struct btrfs_bio *bbio, int mirror_num)
  		bbio->saved_iter = bio->bi_iter;
  		ret = btrfs_lookup_bio_sums(bbio);
  		if (ret)
-			goto fail;
+			goto fail_split;
  	}
 
  	if (btrfs_op(bio) == BTRFS_MAP_WRITE) {

@@ -732,13 +739,13 @@ static bool btrfs_submit_chunk(struct btrfs_bio *bbio, int mirror_num)
 
  			ret = btrfs_bio_csum(bbio);
  			if (ret)
-				goto fail;
+				goto fail_split;
  		} else if (use_append ||
  			   (btrfs_is_zoned(fs_info) && inode &&
  			    inode->flags & BTRFS_INODE_NODATASUM)) {
  			ret = btrfs_alloc_dummy_sum(bbio);
  			if (ret)
-				goto fail;
+				goto fail_split;
  		}
  	}
 

@@ -746,7 +753,7 @@ static bool btrfs_submit_chunk(struct btrfs_bio *bbio, int mirror_num)
  done:
  	return map_length == length;
 
-fail:
+fail_split:
  	btrfs_bio_counter_dec(fs_info);
  	/*
  	 * We have split the original bbio, now we have to end both the current

@@ -760,6 +767,7 @@ static bool btrfs_submit_chunk(struct btrfs_bio *bbio, int mirror_num)
 
  		btrfs_bio_end_io(remaining, ret);
  	}
+fail:
  	btrfs_bio_end_io(bbio, ret);
  	/* Do not submit another chunk */
  	return true;

fs/btrfs/bio.c static bool btrfs_submit_chunk(struct btrfs_bio *bbio, int mirror_num) · line 694

Quoted 5 lines

   
   	if (map_length < length) {
   		bbio = btrfs_split_bio(fs_info, bbio, map_length);

fs/btrfs/bio.c +2 -0

+		if (IS_ERR(bbio)) {
+			ret = errno_to_blk_status(PTR_ERR(bbio));

btrfs_split_bio() does splitting, but error means "goto fail". However other failure points "goto fail_split". I find that label naming odd.

Furthermore, at "fail", we call btrfs_bio_end_io() and that function dereferences bbio (which is -EINVAL or something like that)