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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: Wang Jianchao <wangjianchao@kuaishou.com>
Link: https://lore.kernel.org/r/20210830075246.12516-6-jianchao.wan9@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Wang Jianchao 2021-08-30 15:52:46 +08:00 committed by Theodore Ts'o
parent 55cdd0af2b
commit 5036ab8df2
3 changed files with 13 additions and 3 deletions
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8
fs/ext4/balloc.c
View File

@ -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,

1
fs/ext4/ext4.h
View File

@ -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;

7
fs/ext4/mballoc.c
View File

@ -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;