ext4: use ext4_grp_locked_error in mb_find_extent

Commit 5d1b1b3 ("ext4: fix BUG when calling ext4_error with locked
block group") introduces ext4_grp_locked_error to handle unlocking a
group in error cases. Otherwise, there is a possibility of a sleep while
atomic. However, since 43c7322 ("ext4: replace BUG_ON with WARN_ON
in mb_find_extent()"), mb_find_extent() has contained a ext4_error()
call while a group spinlock is held. Replace this with
ext4_grp_locked_error.

Fixes: 43c7322 ("ext4: replace BUG_ON with WARN_ON in mb_find_extent()")
Cc: <stable@vger.kernel.org> # 4.14+
Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
Reviewed-by: Junxiao Bi <junxiao.bi@oracle.com>
Link: https://lore.kernel.org/r/20210623232114.34457-1-stephen.s.brennan@oracle.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: brenns10

fs/ext4/mballoc.c

@@ -1909,10 +1909,11 @@ static int mb_find_extent(struct ext4_buddy *e4b, int block,
 	if (ex->fe_start + ex->fe_len > EXT4_CLUSTERS_PER_GROUP(e4b->bd_sb)) {
 		/* Should never happen! (but apparently sometimes does?!?) */
 		WARN_ON(1);
-		ext4_error(e4b->bd_sb, "corruption or bug in mb_find_extent "
-			   "block=%d, order=%d needed=%d ex=%u/%d/%d@%u",
-			   block, order, needed, ex->fe_group, ex->fe_start,
-			   ex->fe_len, ex->fe_logical);
+		ext4_grp_locked_error(e4b->bd_sb, e4b->bd_group, 0, 0,
+			"corruption or bug in mb_find_extent "
+			"block=%d, order=%d needed=%d ex=%u/%d/%d@%u",
+			block, order, needed, ex->fe_group, ex->fe_start,
+			ex->fe_len, ex->fe_logical);
 		ex->fe_len = 0;
 		ex->fe_start = 0;
 		ex->fe_group = 0;