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authorZhao Lei <zhaolei@cn.fujitsu.com>2015-07-15 11:48:14 +0800
committerChris Mason <clm@fb.com>2015-07-22 18:20:51 -0700
commit8a7330130470e173832385861c1aa6e37a4e50d2 (patch)
treed1ec0c10008e9970fd1c42fb2e7d9ae2addc0464 /fs
parentBtrfs: fix file corruption after cloning inline extents (diff)
downloadlinux-dev-8a7330130470e173832385861c1aa6e37a4e50d2.tar.xz
linux-dev-8a7330130470e173832385861c1aa6e37a4e50d2.zip
btrfs: Fix lockdep warning of btrfs_run_delayed_iputs()
Liu Bo <bo.li.liu@oracle.com> reported a lockdep warning of delayed_iput_sem in xfstests generic/241: [ 2061.345955] ============================================= [ 2061.346027] [ INFO: possible recursive locking detected ] [ 2061.346027] 4.1.0+ #268 Tainted: G W [ 2061.346027] --------------------------------------------- [ 2061.346027] btrfs-cleaner/3045 is trying to acquire lock: [ 2061.346027] (&fs_info->delayed_iput_sem){++++..}, at: [<ffffffff814063ab>] btrfs_run_delayed_iputs+0x6b/0x100 [ 2061.346027] but task is already holding lock: [ 2061.346027] (&fs_info->delayed_iput_sem){++++..}, at: [<ffffffff814063ab>] btrfs_run_delayed_iputs+0x6b/0x100 [ 2061.346027] other info that might help us debug this: [ 2061.346027] Possible unsafe locking scenario: [ 2061.346027] CPU0 [ 2061.346027] ---- [ 2061.346027] lock(&fs_info->delayed_iput_sem); [ 2061.346027] lock(&fs_info->delayed_iput_sem); [ 2061.346027] *** DEADLOCK *** It is rarely happened, about 1/400 in my test env. The reason is recursion of btrfs_run_delayed_iputs(): cleaner_kthread -> btrfs_run_delayed_iputs() *1 -> get delayed_iput_sem lock *2 -> iput() -> ... -> btrfs_commit_transaction() -> btrfs_run_delayed_iputs() *1 -> get delayed_iput_sem lock (dead lock) *2 *1: recursion of btrfs_run_delayed_iputs() *2: warning of lockdep about delayed_iput_sem When fs is in high stress, new iputs may added into fs_info->delayed_iputs list when btrfs_run_delayed_iputs() is running, which cause second btrfs_run_delayed_iputs() run into down_read(&fs_info->delayed_iput_sem) again, and cause above lockdep warning. Actually, it will not cause real problem because both locks are read lock, but to avoid lockdep warning, we can do a fix. Fix: Don't do btrfs_run_delayed_iputs() in btrfs_commit_transaction() for cleaner_kthread thread to break above recursion path. cleaner_kthread is calling btrfs_run_delayed_iputs() explicitly in code, and don't need to call btrfs_run_delayed_iputs() again in btrfs_commit_transaction(), it also give us a bonus to avoid stack overflow. Test: No above lockdep warning after patch in 1200 generic/241 tests. Reported-by: Liu Bo <bo.li.liu@oracle.com> Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com> Reviewed-by: Liu Bo <bo.li.liu@oracle.com> Signed-off-by: Chris Mason <clm@fb.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/btrfs/transaction.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 51e0f0d0053e..f5021fcb154e 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -2152,7 +2152,8 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
kmem_cache_free(btrfs_trans_handle_cachep, trans);
- if (current != root->fs_info->transaction_kthread)
+ if (current != root->fs_info->transaction_kthread &&
+ current != root->fs_info->cleaner_kthread)
btrfs_run_delayed_iputs(root);
return ret;