From: Tahsin Erdogan <tahsin@google.com>
To: Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Jan Kara <jack@suse.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
Tahsin Erdogan <tahsin@google.com>
Subject: [PATCH v2] writeback: inode cgroup wb switch should not call ihold()
Date: Wed, 15 Jun 2016 13:35:10 -0700 [thread overview]
Message-ID: <1466022910-11243-1-git-send-email-tahsin@google.com> (raw)
Asynchronous wb switching of inodes takes an additional ref count on an
inode to make sure inode remains valid until switchover is completed.
However, anyone calling ihold() must already have a ref count on inode,
but in this case inode->i_count may already be zero:
------------[ cut here ]------------
WARNING: CPU: 1 PID: 917 at fs/inode.c:397 ihold+0x2b/0x30
CPU: 1 PID: 917 Comm: kworker/u4:5 Not tainted 4.7.0-rc2+ #49
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs
01/01/2011
Workqueue: writeback wb_workfn (flush-8:16)
0000000000000000 ffff88007ca0fb58 ffffffff805990af 0000000000000000
0000000000000000 ffff88007ca0fb98 ffffffff80268702 0000018d000004e2
ffff88007cef40e8 ffff88007c9b89a8 ffff880079e3a740 0000000000000003
Call Trace:
[<ffffffff805990af>] dump_stack+0x4d/0x6e
[<ffffffff80268702>] __warn+0xc2/0xe0
[<ffffffff802687d8>] warn_slowpath_null+0x18/0x20
[<ffffffff8035b4ab>] ihold+0x2b/0x30
[<ffffffff80367ecc>] inode_switch_wbs+0x11c/0x180
[<ffffffff80369110>] wbc_detach_inode+0x170/0x1a0
[<ffffffff80369abc>] writeback_sb_inodes+0x21c/0x530
[<ffffffff80369f7e>] wb_writeback+0xee/0x1e0
[<ffffffff8036a147>] wb_workfn+0xd7/0x280
[<ffffffff80287531>] ? try_to_wake_up+0x1b1/0x2b0
[<ffffffff8027bb09>] process_one_work+0x129/0x300
[<ffffffff8027be06>] worker_thread+0x126/0x480
[<ffffffff8098cde7>] ? __schedule+0x1c7/0x561
[<ffffffff8027bce0>] ? process_one_work+0x300/0x300
[<ffffffff80280ff4>] kthread+0xc4/0xe0
[<ffffffff80335578>] ? kfree+0xc8/0x100
[<ffffffff809903cf>] ret_from_fork+0x1f/0x40
[<ffffffff80280f30>] ? __kthread_parkme+0x70/0x70
---[ end trace aaefd2fd9f306bc4 ]---
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tahsin Erdogan <tahsin@google.com>
---
v2:
removed inode->i_count == 0 check
replaced ihold() with __iget()
updated commit description
fs/fs-writeback.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 989a2cef6b76..fe7e83a45eff 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -483,9 +483,9 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id)
goto out_free;
}
inode->i_state |= I_WB_SWITCH;
+ __iget(inode);
spin_unlock(&inode->i_lock);
- ihold(inode);
isw->inode = inode;
atomic_inc(&isw_nr_in_flight);
--
2.8.0.rc3.226.g39d4020
next reply other threads:[~2016-06-15 20:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-15 20:35 Tahsin Erdogan [this message]
2016-06-16 7:13 ` [PATCH v2] writeback: inode cgroup wb switch should not call ihold() Jan Kara
2016-06-16 12:09 ` Tahsin Erdogan
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