On 06/30/2016 12:00 AM, Jan Kara wrote:
On Fri 17-06-16 20:04:34, Jan Kara wrote:
On Fri 17-06-16 13:40:33, Calvin Owens wrote:
On Thursday 06/16 at 10:33 +0200, Jan Kara wrote:
Hi Calvin,
On Wed 15-06-16 16:49:39, Calvin Owens wrote:
I'm hitting the following warning on a 4.0 kernel:
WARNING: CPU: 15 PID: 1005611 at fs/ext4/inode.c:233 ext4_evict_inode+0x4be/0x4d0()
CPU: 15 PID: 1005611 Comm: rocksdb:bg0 Not tainted 4.0.9-60_fbk10_rc1_3974_g796b9b6 #1
Call Trace:
[<ffffffff8176af8e>] dump_stack+0x4d/0x63
[<ffffffff8106c4dc>] warn_slowpath_common+0x8c/0xd0
[<ffffffff8106c5da>] warn_slowpath_null+0x1a/0x20
[<ffffffff81242c0e>] ext4_evict_inode+0x4be/0x4d0
[<ffffffff811d248b>] evict+0xbb/0x190
[<ffffffff811d2d6d>] iput+0x17d/0x1e0
[<ffffffff811ce0e0>] __dentry_kill+0x190/0x1e0
[<ffffffff811ce2d1>] dput+0x1a1/0x1f0
[<ffffffff811b952a>] __fput+0x17a/0x210
[<ffffffff811b960e>] ____fput+0xe/0x10
[<ffffffff81086dbf>] task_work_run+0xbf/0x100
[<ffffffff81002bcc>] do_notify_resume+0x7c/0x90
[<ffffffff81771529>] int_signal+0x12/0x17
Commit 822dbba ("ext4: fix warning in ext4_evict_inode()") proportedly fixed
this in 3.11. The check was entirely removed in 4.6.
OK, so this is the warning:
WARN_ON(atomic_read(&EXT4_I(inode)->i_ioend_count));
It was removed in 4.6 since we maintained i_ioend_count only to be able to
do this check and it didn't trigger for a long time. So it is interesting
that it actually triggered for you with 4.0.
Is it interesting to you that this triggers on 4.0? I can revert 600be30 and
see if I can reproduce it on upstream, but since the check got removed I
was wondering if there was post-4.0 work that makes it obsolete?
It would be great. I'm attaching a revert and an additional debug patch. If
you can run with these two on the latest kernel (or even just apply the debug
patch on top of 4.0) and reproduce the issue with it, I would be grateful.
Forgot to attach the patches? Or did my mailserver eat them? :)
Sorry, probably forgot to attach. Here they are.
Any luck with the patch?
No luck at all :/
Whatever triggers this is extraordinarily rare, and I haven't been able to pin it
down: I see the WARN from 1-2 random hosts each day across all of FB's servers.
I'll keep at it and let you know if I get anything, hopefully soon.
Thanks,
Calvin
Honza
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