>From ce4bb26350da47a6c07be378bf478e5a81bc96d4 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 15 Sep 2020 13:54:20 +0200 Subject: [PATCH] ext4: Discard preallocations before releasing group lock 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 --- fs/ext4/mballoc.c | 26 ++++++++++---------------- 1 file changed, 10 insertions(+), 16 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 132c118d12e1..0ded25d55d9b 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -4215,22 +4215,6 @@ 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) { @@ -4248,6 +4232,16 @@ ext4_mb_discard_group_preallocations(struct super_block *sb, call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback); } + /* if we still need more blocks and some PAs were used, try again */ + if (free < needed && busy) { + ext4_unlock_group(sb, group); + cond_resched(); + busy = 0; + /* Make sure we increment discard_pa_seq again */ + needed -= free; + free = 0; + goto repeat; + } out: ext4_unlock_group(sb, group); ext4_mb_unload_buddy(&e4b); -- 2.16.4