Commit 5036ab8d authored by Wang Jianchao's avatar Wang Jianchao Committed by Theodore Ts'o
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ext4: flush background discard kwork when retry allocation 



The background discard kwork tries to mark blocks used and issue
discard. This can make filesystem suffer from NOSPC error, xfstest
generic/371 can fail due to it. Fix it by flushing discard kwork
in ext4_should_retry_alloc. At the same time, give up discard at
the moment.

Signed-off-by: default avatarWang Jianchao <wangjianchao@kuaishou.com>
Link: https://lore.kernel.org/r/20210830075246.12516-6-jianchao.wan9@gmail.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 55cdd0af

fs/ext4/balloc.c

+7 −1
Original line number Diff line number Diff line
@@ -652,8 +652,14 @@ int ext4_should_retry_alloc(struct super_block *sb, int *retries) 
	 * possible we just missed a transaction commit that did so

	 */

	smp_mb();

	if (sbi->s_mb_free_pending == 0)

	if (sbi->s_mb_free_pending == 0) {

		if (test_opt(sb, DISCARD)) {

			atomic_inc(&sbi->s_retry_alloc_pending);

			flush_work(&sbi->s_discard_work);

			atomic_dec(&sbi->s_retry_alloc_pending);

		}

		return ext4_has_free_clusters(sbi, 1, 0);

	}



	/*

	 * it's possible we've just missed a transaction commit here,

fs/ext4/ext4.h

+1 −0
Original line number Diff line number Diff line
@@ -1538,6 +1538,7 @@ struct ext4_sb_info { 
						   after commit completed */

	struct list_head s_discard_list;

	struct work_struct s_discard_work;

	atomic_t s_retry_alloc_pending;

	struct rb_root s_mb_avg_fragment_size_root;

	rwlock_t s_mb_rb_lock;

	struct list_head *s_mb_largest_free_orders;

fs/ext4/mballoc.c

+5 −2
Original line number Diff line number Diff line
@@ -3331,9 +3331,11 @@ static void ext4_discard_work(struct work_struct *work) 
	load_grp = UINT_MAX;

	list_for_each_entry_safe(fd, nfd, &discard_list, efd_list) {

		/*

		 * If filesystem is umounting or no memory, give up the discard

		 * If filesystem is umounting or no memory or suffering

		 * from no space, give up the discard

		 */

		if ((sb->s_flags & SB_ACTIVE) && !err) {

		if ((sb->s_flags & SB_ACTIVE) && !err &&

		    !atomic_read(&sbi->s_retry_alloc_pending)) {

			grp = fd->efd_group;

			if (grp != load_grp) {

				if (load_grp != UINT_MAX)
@@ -3431,6 +3433,7 @@ int ext4_mb_init(struct super_block *sb) 
	INIT_LIST_HEAD(&sbi->s_freed_data_list);

	INIT_LIST_HEAD(&sbi->s_discard_list);

	INIT_WORK(&sbi->s_discard_work, ext4_discard_work);

	atomic_set(&sbi->s_retry_alloc_pending, 0);



	sbi->s_mb_max_to_scan = MB_DEFAULT_MAX_TO_SCAN;

	sbi->s_mb_min_to_scan = MB_DEFAULT_MIN_TO_SCAN;