]> git.ipfire.org Git - thirdparty/kernel/stable.git/commitdiff
ext4: discard preallocations before releasing group lock
authorJan Kara <jack@suse.cz>
Thu, 24 Sep 2020 15:09:59 +0000 (17:09 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 29 Oct 2020 09:08:08 +0000 (10:08 +0100)
[ 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@suse.cz>
Link: https://lore.kernel.org/r/20200924150959.4335-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
fs/ext4/mballoc.c

index 787a894f5d1da1b71025cb29dc904bf5acc1cb92..79d32ea606aa16e716c2520818ff8b023dfc489e 100644 (file)
@@ -4037,7 +4037,7 @@ 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))
@@ -4065,6 +4065,7 @@ 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) {
@@ -4094,22 +4095,6 @@ repeat:
                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) {
 
@@ -4127,14 +4112,22 @@ repeat:
                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;
 }
 
 /*