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author | Liu Bo <bo.li.liu@oracle.com> | 2015-07-17 16:49:19 +0800 |
---|---|---|
committer | David Sterba <dsterba@suse.com> | 2016-02-23 13:10:10 +0100 |
commit | 73beece9ca07c003e0e4f4825b12be167334d4ad (patch) | |
tree | b0575466fc5e0c7a493826963e7a4ffa49e31210 /fs/btrfs/reada.c | |
parent | 18558cae0272f8fd9647e69d3fec1565a7949865 (diff) | |
download | linux-73beece9ca07c003e0e4f4825b12be167334d4ad.tar.bz2 |
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>
Diffstat (limited to 'fs/btrfs/reada.c')
-rw-r--r-- | fs/btrfs/reada.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c index 619f92963e27..fe3d4c7b6342 100644 --- a/fs/btrfs/reada.c +++ b/fs/btrfs/reada.c @@ -396,7 +396,7 @@ static struct reada_extent *reada_find_extent(struct btrfs_root *root, } /* insert extent in reada_tree + all per-device trees, all or nothing */ - btrfs_dev_replace_lock(&fs_info->dev_replace); + btrfs_dev_replace_lock(&fs_info->dev_replace, 0); spin_lock(&fs_info->reada_lock); ret = radix_tree_insert(&fs_info->reada_tree, index, re); if (ret == -EEXIST) { @@ -404,12 +404,12 @@ static struct reada_extent *reada_find_extent(struct btrfs_root *root, BUG_ON(!re_exist); re_exist->refcnt++; spin_unlock(&fs_info->reada_lock); - btrfs_dev_replace_unlock(&fs_info->dev_replace); + btrfs_dev_replace_unlock(&fs_info->dev_replace, 0); goto error; } if (ret) { spin_unlock(&fs_info->reada_lock); - btrfs_dev_replace_unlock(&fs_info->dev_replace); + btrfs_dev_replace_unlock(&fs_info->dev_replace, 0); goto error; } prev_dev = NULL; @@ -456,12 +456,12 @@ static struct reada_extent *reada_find_extent(struct btrfs_root *root, BUG_ON(fs_info == NULL); radix_tree_delete(&fs_info->reada_tree, index); spin_unlock(&fs_info->reada_lock); - btrfs_dev_replace_unlock(&fs_info->dev_replace); + btrfs_dev_replace_unlock(&fs_info->dev_replace, 0); goto error; } } spin_unlock(&fs_info->reada_lock); - btrfs_dev_replace_unlock(&fs_info->dev_replace); + btrfs_dev_replace_unlock(&fs_info->dev_replace, 0); btrfs_put_bbio(bbio); return re; |