ext4: fix iloc.bh leak in ext4_fc_replay_inode() error paths

During code review, Joseph found that ext4_fc_replay_inode() calls
ext4_get_fc_inode_loc() to get the inode location, which holds a
reference to iloc.bh that must be released via brelse().

However, several error paths jump to the 'out' label without
releasing iloc.bh:

 - ext4_handle_dirty_metadata() failure
 - sync_dirty_buffer() failure
 - ext4_mark_inode_used() failure
 - ext4_iget() failure

Fix this by introducing an 'out_brelse' label placed just before
the existing 'out' label to ensure iloc.bh is always released.

Additionally, make ext4_fc_replay_inode() propagate errors
properly instead of always returning 0.

Reported-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Fixes: 8016e29 ("ext4: fast commit recovery path")
Signed-off-by: Baokun Li <libaokun@linux.alibaba.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20260323060836.3452660-1-libaokun@linux.alibaba.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org

Author: Baokun Li

fs/ext4/fast_commit.c

@@ -1613,19 +1613,21 @@ static int ext4_fc_replay_inode(struct super_block *sb,
 	/* Immediately update the inode on disk. */
 	ret = ext4_handle_dirty_metadata(NULL, NULL, iloc.bh);
 	if (ret)
-		goto out;
+		goto out_brelse;
 	ret = sync_dirty_buffer(iloc.bh);
 	if (ret)
-		goto out;
+		goto out_brelse;
 	ret = ext4_mark_inode_used(sb, ino);
 	if (ret)
-		goto out;
+		goto out_brelse;
 
 	/* Given that we just wrote the inode on disk, this SHOULD succeed. */
 	inode = ext4_iget(sb, ino, EXT4_IGET_NORMAL);
 	if (IS_ERR(inode)) {
 		ext4_debug("Inode not found.");
-		return -EFSCORRUPTED;
+		inode = NULL;
+		ret = -EFSCORRUPTED;
+		goto out_brelse;
 	}
 
 	/*
@@ -1642,13 +1644,14 @@ static int ext4_fc_replay_inode(struct super_block *sb,
 	ext4_inode_csum_set(inode, ext4_raw_inode(&iloc), EXT4_I(inode));
 	ret = ext4_handle_dirty_metadata(NULL, NULL, iloc.bh);
 	sync_dirty_buffer(iloc.bh);
+out_brelse:
 	brelse(iloc.bh);
 out:
 	iput(inode);
 	if (!ret)
 		blkdev_issue_flush(sb->s_bdev);
 
-	return 0;
+	return ret;
 }
 
 /*