ext4: cond_resched in work-heavy group loops

mainline inclusion
from mainline-5.2-rc1
commit 4b99faa2
category: bugfix
bugzilla: 18685
CVE: NA
---------------------------
Signed-off-by: NKhazhismel Kumykov <khazhy@google.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Reviewed-by: NAndreas Dilger <adilger@dilger.ca>
Signed-off-by: Nzhangyi (F) <yi.zhang@huawei.com>
Reviewed-by: Nyangerkun <yangerkun@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

fs/ext4/block_validity.c

@@ -198,6 +198,7 @@ int ext4_setup_system_zone(struct super_block *sb)
 		return 0;
 
 	for (i=0; i < ngroups; i++) {
+		cond_resched();
 		if (ext4_bg_has_super(sb, i) &&
 		    ((i < 5) || ((i % flex_size) == 0)))
 			add_system_zone(sbi, ext4_group_first_block_no(sb, i),

fs/ext4/mballoc.c

@@ -2490,6 +2490,7 @@ static int ext4_mb_init_backend(struct super_block *sb)
 	sbi->s_buddy_cache->i_ino = EXT4_BAD_INO;
 	EXT4_I(sbi->s_buddy_cache)->i_disksize = 0;
 	for (i = 0; i < ngroups; i++) {
+		cond_resched();
 		desc = ext4_get_group_desc(sb, i, NULL);
 		if (desc == NULL) {
 			ext4_msg(sb, KERN_ERR, "can't read descriptor %u", i);
@@ -2705,6 +2706,7 @@ int ext4_mb_release(struct super_block *sb)
 
 	if (sbi->s_group_info) {
 		for (i = 0; i < ngroups; i++) {
+			cond_resched();
 			grinfo = ext4_get_group_info(sb, i);
 #ifdef DOUBLE_CHECK
 			kfree(grinfo->bb_bitmap);