btrfs: handle bio_split() errors

Commit e546fe1 ("block: Rework bio_split() return value") changed
bio_split() so that it can return errors.

Add error handling for it in btrfs_split_bio() and ultimately
btrfs_submit_chunk(). As the bio is not submitted, the bio counter must
be decremented to pair btrfs_bio_counter_inc_blocked().

Reviewed-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/bio.c

@@ -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;
@@ -678,15 +681,24 @@ static bool btrfs_submit_chunk(struct btrfs_bio *bbio, int mirror_num)
 				&bioc, &smap, &mirror_num);
 	if (error) {
 		ret = errno_to_blk_status(error);
-		goto fail;
+		btrfs_bio_counter_dec(fs_info);
+		goto end_bbio;
 	}
 
 	map_length = min(map_length, length);
 	if (use_append)
 		map_length = btrfs_append_map_length(bbio, map_length);
 
 	if (map_length < length) {
-		bbio = btrfs_split_bio(fs_info, bbio, map_length);
+		struct btrfs_bio *split;
+
+		split = btrfs_split_bio(fs_info, bbio, map_length);
+		if (IS_ERR(split)) {
+			ret = errno_to_blk_status(PTR_ERR(split));
+			btrfs_bio_counter_dec(fs_info);
+			goto end_bbio;
+		}
+		bbio = split;
 		bio = &bbio->bio;
 	}
 
@@ -760,6 +772,7 @@ static bool btrfs_submit_chunk(struct btrfs_bio *bbio, int mirror_num)
 
 		btrfs_bio_end_io(remaining, ret);
 	}
+end_bbio:
 	btrfs_bio_end_io(bbio, ret);
 	/* Do not submit another chunk */
 	return true;