This is a note to let you know that I've just added the patch titled
ext4: discard preallocations before releasing group lock
to the 5.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ext4-discard-preallocations-before-releasing-group-l.patch
and it can be found in the queue-5.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit f7e79eebadb85deb94e6953ebabbc774a6efb708
Author: Jan Kara <jack@xxxxxxx>
Date: Thu Sep 24 17:09:59 2020 +0200
ext4: discard preallocations before releasing group lock
[ Upstream commit 5b3dc19dda6691e8ab574e8eede1aef6f02a4f1c ]
ext4_mb_discard_group_preallocations() can be releasing group lock with
preallocations accumulated on its local list. Thus although
discard_pa_seq was incremented and concurrent allocating processes will
be retrying allocations, it can happen that premature ENOSPC error is
returned because blocks used for preallocations are not available for
reuse yet. Make sure we always free locally accumulated preallocations
before releasing group lock.
Fixes: 07b5b8e1ac40 ("ext4: mballoc: introduce pcpu seqcnt for freeing PA to improve ENOSPC handling")
Signed-off-by: Jan Kara <jack@xxxxxxx>
Link: https://lore.kernel.org/r/20200924150959.4335-1-jack@xxxxxxx
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index ff47347012f4b..a8d99f676fb1f 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4160,7 +4160,7 @@ ext4_mb_discard_group_preallocations(struct super_block *sb,
struct ext4_buddy e4b;
int err;
int busy = 0;
- int free = 0;
+ int free, free_total = 0;
mb_debug(sb, "discard preallocation for group %u\n", group);
if (list_empty(&grp->bb_prealloc_list))
@@ -4188,6 +4188,7 @@ ext4_mb_discard_group_preallocations(struct super_block *sb,
INIT_LIST_HEAD(&list);
repeat:
+ free = 0;
ext4_lock_group(sb, group);
list_for_each_entry_safe(pa, tmp,
&grp->bb_prealloc_list, pa_group_list) {
@@ -4217,22 +4218,6 @@ ext4_mb_discard_group_preallocations(struct super_block *sb,
list_add(&pa->u.pa_tmp_list, &list);
}
- /* if we still need more blocks and some PAs were used, try again */
- if (free < needed && busy) {
- busy = 0;
- ext4_unlock_group(sb, group);
- cond_resched();
- goto repeat;
- }
-
- /* found anything to free? */
- if (list_empty(&list)) {
- BUG_ON(free != 0);
- mb_debug(sb, "Someone else may have freed PA for this group %u\n",
- group);
- goto out;
- }
-
/* now free all selected PAs */
list_for_each_entry_safe(pa, tmp, &list, u.pa_tmp_list) {
@@ -4250,14 +4235,22 @@ ext4_mb_discard_group_preallocations(struct super_block *sb,
call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
}
-out:
+ free_total += free;
+
+ /* if we still need more blocks and some PAs were used, try again */
+ if (free_total < needed && busy) {
+ ext4_unlock_group(sb, group);
+ cond_resched();
+ busy = 0;
+ goto repeat;
+ }
ext4_unlock_group(sb, group);
ext4_mb_unload_buddy(&e4b);
put_bh(bitmap_bh);
out_dbg:
mb_debug(sb, "discarded (%d) blocks preallocated for group %u bb_free (%d)\n",
- free, group, grp->bb_free);
- return free;
+ free_total, group, grp->bb_free);
+ return free_total;
}
/*
