Btrfs: fix lockdep deadlock warning due to dev_replace
Xfstests btrfs/011 complains about a deadlock warning,
[ 1226.649039] =========================================================
[ 1226.649039] [ INFO: possible irq lock inversion dependency detected ]
[ 1226.649039] 4.1.0+ #270 Not tainted
[ 1226.649039] ---------------------------------------------------------
[ 1226.652955] kswapd0/46 just changed the state of lock:
[ 1226.652955] (&delayed_node->mutex){+.+.-.}, at: [<ffffffff81458735>] __btrfs_release_delayed_node+0x45/0x1d0
[ 1226.652955] but this lock took another, RECLAIM_FS-unsafe lock in the past:
[ 1226.652955] (&fs_info->dev_replace.lock){+.+.+.}
and interrupts could create inverse lock ordering between them.
[ 1226.652955]
other info that might help us debug this:
[ 1226.652955] Chain exists of:
&delayed_node->mutex --> &found->groups_sem --> &fs_info->dev_replace.lock
[ 1226.652955] Possible interrupt unsafe locking scenario:
[ 1226.652955] CPU0 CPU1
[ 1226.652955] ---- ----
[ 1226.652955] lock(&fs_info->dev_replace.lock);
[ 1226.652955] local_irq_disable();
[ 1226.652955] lock(&delayed_node->mutex);
[ 1226.652955] lock(&found->groups_sem);
[ 1226.652955] <Interrupt>
[ 1226.652955] lock(&delayed_node->mutex);
[ 1226.652955]
*** DEADLOCK ***
Commit 084b6e7c7607 ("btrfs: Fix a lockdep warning when running xfstest.") tried
to fix a similar one that has the exactly same warning, but with that, we still
run to this.
The above lock chain comes from
btrfs_commit_transaction
->btrfs_run_delayed_items
...
->__btrfs_update_delayed_inode
...
->__btrfs_cow_block
...
->find_free_extent
->cache_block_group
->load_free_space_cache
->btrfs_readpages
->submit_one_bio
...
->__btrfs_map_block
->btrfs_dev_replace_lock
However, with high memory pressure, tasks which hold dev_replace.lock can
be interrupted by kswapd and then kswapd is intended to release memory occupied
by superblock, inodes and dentries, where we may call evict_inode, and it comes
to
[ 1226.652955] [<ffffffff81458735>] __btrfs_release_delayed_node+0x45/0x1d0
[ 1226.652955] [<ffffffff81459e74>] btrfs_remove_delayed_node+0x24/0x30
[ 1226.652955] [<ffffffff8140c5fe>] btrfs_evict_inode+0x34e/0x700
delayed_node->mutex may be acquired in __btrfs_release_delayed_node(), and it leads
to a ABBA deadlock.
To fix this, we can use "blocking rwlock" used in the case of extent_buffer, but
things are simpler here since we only needs read's spinlock to blocking lock.
With this, btrfs/011 no more produces warnings in dmesg.
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 366b335..858a2e4 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1714,12 +1714,12 @@
} while (read_seqretry(&root->fs_info->profiles_lock, seq));
num_devices = root->fs_info->fs_devices->num_devices;
- btrfs_dev_replace_lock(&root->fs_info->dev_replace);
+ btrfs_dev_replace_lock(&root->fs_info->dev_replace, 0);
if (btrfs_dev_replace_is_ongoing(&root->fs_info->dev_replace)) {
WARN_ON(num_devices < 1);
num_devices--;
}
- btrfs_dev_replace_unlock(&root->fs_info->dev_replace);
+ btrfs_dev_replace_unlock(&root->fs_info->dev_replace, 0);
if ((all_avail & BTRFS_BLOCK_GROUP_RAID10) && num_devices <= 4) {
ret = BTRFS_ERROR_DEV_RAID10_MIN_NOT_MET;
@@ -3686,12 +3686,12 @@
}
num_devices = fs_info->fs_devices->num_devices;
- btrfs_dev_replace_lock(&fs_info->dev_replace);
+ btrfs_dev_replace_lock(&fs_info->dev_replace, 0);
if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace)) {
BUG_ON(num_devices < 1);
num_devices--;
}
- btrfs_dev_replace_unlock(&fs_info->dev_replace);
+ btrfs_dev_replace_unlock(&fs_info->dev_replace, 0);
allowed = BTRFS_AVAIL_ALLOC_BIT_SINGLE;
if (num_devices == 1)
allowed |= BTRFS_BLOCK_GROUP_DUP;
@@ -5062,10 +5062,10 @@
ret = 1;
free_extent_map(em);
- btrfs_dev_replace_lock(&fs_info->dev_replace);
+ btrfs_dev_replace_lock(&fs_info->dev_replace, 0);
if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace))
ret++;
- btrfs_dev_replace_unlock(&fs_info->dev_replace);
+ btrfs_dev_replace_unlock(&fs_info->dev_replace, 0);
return ret;
}
@@ -5325,10 +5325,12 @@
if (!bbio_ret)
goto out;
- btrfs_dev_replace_lock(dev_replace);
+ btrfs_dev_replace_lock(dev_replace, 0);
dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(dev_replace);
if (!dev_replace_is_ongoing)
- btrfs_dev_replace_unlock(dev_replace);
+ btrfs_dev_replace_unlock(dev_replace, 0);
+ else
+ btrfs_dev_replace_set_lock_blocking(dev_replace);
if (dev_replace_is_ongoing && mirror_num == map->num_stripes + 1 &&
!(rw & (REQ_WRITE | REQ_DISCARD | REQ_GET_READ_MIRRORS)) &&
@@ -5751,8 +5753,10 @@
bbio->mirror_num = map->num_stripes + 1;
}
out:
- if (dev_replace_is_ongoing)
- btrfs_dev_replace_unlock(dev_replace);
+ if (dev_replace_is_ongoing) {
+ btrfs_dev_replace_clear_lock_blocking(dev_replace);
+ btrfs_dev_replace_unlock(dev_replace, 0);
+ }
free_extent_map(em);
return ret;
}