diff options
author | Jeff Mahoney <jeffm@suse.com> | 2014-03-26 14:11:26 -0400 |
---|---|---|
committer | Chris Mason <clm@fb.com> | 2014-04-07 09:08:40 -0700 |
commit | ed55b6ac077fe7f9c6490ff55172c4b563562d7c (patch) | |
tree | a126c4cdc858dc1886aa0e56c0b97a8dee32546f /fs | |
parent | 3f8a18cc53bd1be26eb5b5247e1386ad0e21b623 (diff) |
btrfs: fix lockdep warning with reclaim lock inversion
When encountering memory pressure, testers have run into the following
lockdep warning. It was caused by __link_block_group calling kobject_add
with the groups_sem held. kobject_add calls kvasprintf with GFP_KERNEL,
which gets us into reclaim context. The kobject doesn't actually need
to be added under the lock -- it just needs to ensure that it's only
added for the first block group to be linked.
=========================================================
[ INFO: possible irq lock inversion dependency detected ]
3.14.0-rc8-default #1 Not tainted
---------------------------------------------------------
kswapd0/169 just changed the state of lock:
(&delayed_node->mutex){+.+.-.}, at: [<ffffffffa018baea>] __btrfs_release_delayed_node+0x3a/0x200 [btrfs]
but this lock took another, RECLAIM_FS-unsafe lock in the past:
(&found->groups_sem){+++++.}
and interrupts could create inverse lock ordering between them.
other info that might help us debug this:
Possible interrupt unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&found->groups_sem);
local_irq_disable();
lock(&delayed_node->mutex);
lock(&found->groups_sem);
<Interrupt>
lock(&delayed_node->mutex);
*** DEADLOCK ***
2 locks held by kswapd0/169:
#0: (shrinker_rwsem){++++..}, at: [<ffffffff81159e8a>] shrink_slab+0x3a/0x160
#1: (&type->s_umount_key#27){++++..}, at: [<ffffffff811bac6f>] grab_super_passive+0x3f/0x90
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/btrfs/extent-tree.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 4d2508bbf6f0..1341163abe68 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -8337,9 +8337,15 @@ static void __link_block_group(struct btrfs_space_info *space_info, struct btrfs_block_group_cache *cache) { int index = get_block_group_index(cache); + bool first = false; down_write(&space_info->groups_sem); - if (list_empty(&space_info->block_groups[index])) { + if (list_empty(&space_info->block_groups[index])) + first = true; + list_add_tail(&cache->list, &space_info->block_groups[index]); + up_write(&space_info->groups_sem); + + if (first) { struct kobject *kobj = &space_info->block_group_kobjs[index]; int ret; @@ -8351,8 +8357,6 @@ static void __link_block_group(struct btrfs_space_info *space_info, kobject_put(&space_info->kobj); } } - list_add_tail(&cache->list, &space_info->block_groups[index]); - up_write(&space_info->groups_sem); } static struct btrfs_block_group_cache * |