linux-kernel - Re: [PATCH] fs: fix data races on inode->i

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Message-ID: <CACT4Y+YYGrryrRJuX+Y1jJtxMO=3xEjgMiC81eWM46kaGzDuWg@mail.gmail.com>
Date:	Mon, 19 Oct 2015 17:27:21 +0200
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	William Dauchy <wdauchy@...il.com>
Cc:	Jeff Layton <jlayton@...chiereds.net>,
	Bruce Fields <bfields@...ldses.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Kostya Serebryany <kcc@...gle.com>,
	Andrey Konovalov <andreyknvl@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	ktsan <ktsan@...glegroups.com>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH] fs: fix data races on inode->i_flctx

I would expect that you see something else.
The issue that I fixed would fire very infrequently and unreproducibly.


On Mon, Oct 19, 2015 at 5:18 PM, William Dauchy <wdauchy@...il.com> wrote:
> Hello Dmitry,
>
> On Mon, Sep 21, 2015 at 1:44 PM, Jeff Layton <jlayton@...chiereds.net> wrote:
>> Ok, thanks for the explanation. Patch looks fine to me. I'll go ahead
>> and merge it for v4.4. Let me know though if you think this needs to go
>> in sooner.
>
> I am getting a null deref on a v4.1.x
> Do you think your patch could fix the following trace? It looks
> similar in my opinion.
>
> BUG: unable to handle kernel NULL pointer dereference at 00000000000001c8
> IP: [<ffffffff811d0cf3>] locks_get_lock_context+0x3/0xc0
> PGD 0
> Oops: 0000 [#1] SMP
> CPU: 1 PID: 1773 Comm: kworker/1:1H Not tainted 4.1.11-rc1 #1
> Workqueue: rpciod ffffffff8164fff0
> task: ffff8810374deba0 ti: ffff8810374df150 task.ti: ffff8810374df150
> RIP: 0010:[<ffffffff811d0cf3>]  [<ffffffff811d0cf3>]
> locks_get_lock_context+0x3/0xc0
> RSP: 0000:ffff881036007bb0  EFLAGS: 00010246
> RAX: ffff881036007c30 RBX: ffff881001981880 RCX: 0000000000000002
> RDX: 00000000000006ed RSI: 0000000000000002 RDI: 0000000000000000
> RBP: ffff881036007c08 R08: 0000000000000000 R09: 0000000000000001
> R10: 0000000000000000 R11: ffff88101db69948 R12: ffff8810019818d8
> R13: ffff881036007bc8 R14: ffff880e225d81c0 R15: ffff881edfd2b400
> FS:  0000000000000000(0000) GS:ffff88103fc20000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000000001c8 CR3: 000000000169b000 CR4: 00000000000606f0
> Stack:
>  ffffffff811d2710 ffff881036007bc8 ffffffff819f1af1 ffff881036007bc8
>  ffff881036007bc8 ffff881036007c08 ffff881001981880 ffff8810019818d8
>  ffff881036007c48 ffff880e225d81c0 ffff881edfd2b400 ffff881036007c88
> Call Trace:
>  [<ffffffff811d2710>] ? flock_lock_file+0x30/0x270
>  [<ffffffff811d3ad1>] flock_lock_file_wait+0x41/0xf0
>  [<ffffffff8168be66>] ? _raw_spin_unlock+0x26/0x40
>  [<ffffffff81268de9>] do_vfs_lock+0x19/0x40
>  [<ffffffff812695cc>] nfs4_locku_done+0x5c/0xf0
>  [<ffffffff8164f3f4>] rpc_exit_task+0x34/0xb0
>  [<ffffffff8164fcd9>] __rpc_execute+0x79/0x390
>  [<ffffffff81650000>] rpc_async_schedule+0x10/0x20
>  [<ffffffff81086095>] process_one_work+0x1a5/0x450
>  [<ffffffff81086024>] ? process_one_work+0x134/0x450
>  [<ffffffff8108638b>] worker_thread+0x4b/0x4a0
>  [<ffffffff81086340>] ? process_one_work+0x450/0x450
>  [<ffffffff81086340>] ? process_one_work+0x450/0x450
>  [<ffffffff8108d777>] kthread+0xf7/0x110
>  [<ffffffff8108d680>] ? __kthread_parkme+0xa0/0xa0
>  [<ffffffff8168ce3e>] ret_from_fork+0x3e/0x70
>  [<ffffffff8108d680>] ? __kthread_parkme+0xa0/0xa0
> Code: 48 b8 00 00 00 00 00 00 00 80 55 48 89 e5 48 09 c1 ff d1 5d 85
> c0 0f 95 c0 0f b6 c0 eb b9 66 2e 0f 1f 84 00 00 00 00 00 83 fe 02 <48>
> 8b 87 c8 01 00 00 0f 84 a0 00 00 00 48 85 c0 0f 85 97 00 00
> RIP  [<ffffffff811d0cf3>] locks_get_lock_context+0x3/0xc0
>  RSP <ffff881036007bb0>
> CR2: 00000000000001c8
> ---[ end trace 2da9686dda1b5574 ]---
>
>
> Thanks,
> --
> William
>
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