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Subject[PATCH 2/2] btrfs: add lockdep annotation for btrfs_log_inode
Date
Add a proper subclass to get rid of the following lockdep
error.

[ INFO: possible recursive locking detected ]
4.9.0+ #279 Not tainted
---------------------------------------------
vim/4801 is trying to acquire lock:
(&ei->log_mutex){+.+...}, at: [<000003ff82057592>]
btrfs_log_inode+0x182/0xfa8 [btrfs]

(&ei->log_mutex){+.+...}, at: [<000003ff82057592>]
btrfs_log_inode+0x182/0xfa8 [btrfs]

Possible unsafe locking scenario:
CPU0
----
lock(&ei->log_mutex);
lock(&ei->log_mutex);

*** DEADLOCK ***
May be due to missing lock nesting notation
3 locks held by vim/4801:
#0: (&sb->s_type->i_mutex_key#15){+.+.+.}, at: [<000003ff81fc274c>]
btrfs_sync_file+0x204/0x728 [btrfs]
#1: (sb_internal#2){.+.+..}, at: [<000003ff81fa38e0>]
start_transaction+0x318/0x770 [btrfs]
#2: (&ei->log_mutex){+.+...}, at: [<000003ff82057592>]

[...]
Call Trace:
([<0000000000115ffc>] show_trace+0xe4/0x108)
[<00000000001160f8>] show_stack+0x68/0xe0
[<0000000000652d52>] dump_stack+0x9a/0xd8
[<0000000000209bb0>] __lock_acquire+0xac8/0x1bd0
[<000000000020b3c6>] lock_acquire+0x106/0x4a0
[<0000000000a1fb36>] mutex_lock_nested+0xa6/0x428
[<000003ff82057592>] btrfs_log_inode+0x182/0xfa8 [btrfs]
[<000003ff82057c76>] btrfs_log_inode+0x866/0xfa8 [btrfs]
[<000003ff81ffe278>] btrfs_log_inode_parent+0x218/0x988 [btrfs]
[<000003ff81ffffaa>] btrfs_log_dentry_safe+0x7a/0xa0 [btrfs]
[<000003ff81fc29b6>] btrfs_sync_file+0x46e/0x728 [btrfs]
[<000000000044aeee>] do_fsync+0x5e/0x90
[<000000000044b2ba>] SyS_fsync+0x32/0x40
[<0000000000a26786>] system_call+0xd6/0x288

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
fs/btrfs/tree-log.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 3d33c4e..a3ec717 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -4648,7 +4648,7 @@ static int btrfs_log_inode(struct btrfs_trans_handle *trans,
return ret;
}

- mutex_lock(&BTRFS_I(inode)->log_mutex);
+ mutex_lock_nested(&BTRFS_I(inode)->log_mutex, inode_only);

/*
* a brute force approach to making sure we get the most uptodate
--
2.7.4
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