ext4: convert some BUG_ON's in mballoc to use WARN_RATELIMITED instead

In cases where we have an obvious way of continuing, let's use
WARN_RATELIMITED() instead of BUG_ON().
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/mballoc.c

@@ -1487,7 +1487,13 @@ ext4_mb_load_buddy_gfp(struct super_block *sb, ext4_group_t group,
 			put_page(page);
 		page = find_or_create_page(inode->i_mapping, pnum, gfp);
 		if (page) {
-			BUG_ON(page->mapping != inode->i_mapping);
+			if (WARN_RATELIMIT(page->mapping != inode->i_mapping,
+	"ext4: bitmap's paging->mapping != inode->i_mapping\n")) {
+				/* should never happen */
+				unlock_page(page);
+				ret = -EINVAL;
+				goto err;
+			}
 			if (!PageUptodate(page)) {
 				ret = ext4_mb_init_cache(page, NULL, gfp);
 				if (ret) {
@@ -1523,7 +1529,13 @@ ext4_mb_load_buddy_gfp(struct super_block *sb, ext4_group_t group,
 			put_page(page);
 		page = find_or_create_page(inode->i_mapping, pnum, gfp);
 		if (page) {
-			BUG_ON(page->mapping != inode->i_mapping);
+			if (WARN_RATELIMIT(page->mapping != inode->i_mapping,
+	"ext4: buddy bitmap's page->mapping != inode->i_mapping\n")) {
+				/* should never happen */
+				unlock_page(page);
+				ret = -EINVAL;
+				goto err;
+			}
 			if (!PageUptodate(page)) {
 				ret = ext4_mb_init_cache(page, e4b->bd_bitmap,
 							 gfp);
@@ -2221,7 +2233,9 @@ void ext4_mb_simple_scan_group(struct ext4_allocation_context *ac,
 			continue;
 
 		buddy = mb_find_buddy(e4b, i, &max);
-		BUG_ON(buddy == NULL);
+		if (WARN_RATELIMIT(buddy == NULL,
+			 "ext4: mb_simple_scan_group: mb_find_buddy failed, (%d)\n", i))
+			continue;
 
 		k = mb_find_next_zero_bit(buddy, max, 0);
 		if (k >= max) {
@@ -4229,15 +4243,14 @@ static void ext4_discard_allocated_blocks(struct ext4_allocation_context *ac)
 		if (ac->ac_f_ex.fe_len == 0)
 			return;
 		err = ext4_mb_load_buddy(ac->ac_sb, ac->ac_f_ex.fe_group, &e4b);
-		if (err) {
+		if (WARN_RATELIMIT(err,
+				   "ext4: mb_load_buddy failed (%d)", err))
 			/*
 			 * This should never happen since we pin the
 			 * pages in the ext4_allocation_context so
 			 * ext4_mb_load_buddy() should never fail.
 			 */
-			WARN(1, "mb_load_buddy failed (%d)", err);
 			return;
-		}
 		ext4_lock_group(ac->ac_sb, ac->ac_f_ex.fe_group);
 		mb_free_blocks(ac->ac_inode, &e4b, ac->ac_f_ex.fe_start,
 			       ac->ac_f_ex.fe_len);