As we test disk offline/online with running fsstress, we find fsstress
process is keeping running state.
kworker/u32:3-262 [004] ...1 140.787471: ext4_mb_discard_preallocations: dev 8,32 needed 114
....
kworker/u32:3-262 [004] ...1 140.787471: ext4_mb_discard_preallocations: dev 8,32 needed 114
ext4_mb_new_blocks
repeat:
ext4_mb_discard_preallocations_should_retry(sb, ac, &seq)
freed = ext4_mb_discard_preallocations
ext4_mb_discard_group_preallocations
this_cpu_inc(discard_pa_seq);
---> freed == 0
seq_retry = ext4_get_discard_pa_seq_sum
for_each_possible_cpu(__cpu)
__seq += per_cpu(discard_pa_seq, __cpu);
if (seq_retry != *seq) {
*seq = seq_retry;
ret = true;
}
As we see seq_retry is sum of discard_pa_seq every cpu, if
ext4_mb_discard_group_preallocations return zero discard_pa_seq in this
cpu maybe increase one, so condition "seq_retry != *seq" have always
been met.
To Fix this problem, in ext4_mb_discard_group_preallocations function increase
discard_pa_seq only when it found preallocation to discard.
Fixes: 07b5b8e1ac40 ("ext4: mballoc: introduce pcpu seqcnt for freeing PA to improve ENOSPC handling")
Signed-off-by: Ye Bin <yebin10@xxxxxxxxxx>
---
fs/ext4/mballoc.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index f386fe62727d..fd55264dc3fe 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4191,7 +4191,6 @@ ext4_mb_discard_group_preallocations(struct super_block *sb,
INIT_LIST_HEAD(&list);
repeat:
ext4_lock_group(sb, group);
- this_cpu_inc(discard_pa_seq);
list_for_each_entry_safe(pa, tmp,
&grp->bb_prealloc_list, pa_group_list) {
spin_lock(&pa->pa_lock);
@@ -4233,6 +4232,9 @@ ext4_mb_discard_group_preallocations(struct super_block *sb,
goto out;
}
+ /* only increase when find reallocation to discard */
+ this_cpu_inc(discard_pa_seq);
+
/* now free all selected PAs */
list_for_each_entry_safe(pa, tmp, &list, u.pa_tmp_list) {
--
2.25.4
