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From: Tejun Heo <tj@kernel.org>
To: Tahsin Erdogan <tahsin@google.com>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, David Rientjes <rientjes@google.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5] blkcg: allocate struct blkcg_gq outside request queue spinlock
Date: Thu, 9 Mar 2017 13:27:24 -0500	[thread overview]
Message-ID: <20170309182724.GE28982@htj.duckdns.org> (raw)
In-Reply-To: <20170309080531.9048-1-tahsin@google.com>

On Thu, Mar 09, 2017 at 12:05:31AM -0800, Tahsin Erdogan wrote:
> blkg_conf_prep() currently calls blkg_lookup_create() while holding
> request queue spinlock. This means allocating memory for struct
> blkcg_gq has to be made non-blocking. This causes occasional -ENOMEM
> failures in call paths like below:
> 
>   pcpu_alloc+0x68f/0x710
>   __alloc_percpu_gfp+0xd/0x10
>   __percpu_counter_init+0x55/0xc0
>   cfq_pd_alloc+0x3b2/0x4e0
>   blkg_alloc+0x187/0x230
>   blkg_create+0x489/0x670
>   blkg_lookup_create+0x9a/0x230
>   blkg_conf_prep+0x1fb/0x240
>   __cfqg_set_weight_device.isra.105+0x5c/0x180
>   cfq_set_weight_on_dfl+0x69/0xc0
>   cgroup_file_write+0x39/0x1c0
>   kernfs_fop_write+0x13f/0x1d0
>   __vfs_write+0x23/0x120
>   vfs_write+0xc2/0x1f0
>   SyS_write+0x44/0xb0
>   entry_SYSCALL_64_fastpath+0x18/0xad
> 
> In the code path above, percpu allocator cannot call vmalloc() due to
> queue spinlock.
> 
> A failure in this call path gives grief to tools which are trying to
> configure io weights. We see occasional failures happen shortly after
> reboots even when system is not under any memory pressure. Machines
> with a lot of cpus are more vulnerable to this condition.
> 
> Update blkg_create() function to temporarily drop the rcu and queue
> locks when it is allowed by gfp mask.
> 
> Suggested-by: Tejun Heo <tj@kernel.org>
> Signed-off-by: Tahsin Erdogan <tahsin@google.com>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

  reply	other threads:[~2017-03-09 18:27 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-28  2:49 [PATCH] blkcg: allocate struct blkcg_gq outside request queue spinlock Tahsin Erdogan
2017-02-28 22:47 ` Tejun Heo
2017-02-28 23:51   ` Tahsin Erdogan
2017-03-01 16:55     ` Tejun Heo
2017-03-01 23:43       ` [PATCH v2] " Tahsin Erdogan
2017-03-01 23:49         ` Tahsin Erdogan
2017-03-02 19:32         ` Tejun Heo
2017-03-02 22:33           ` Tahsin Erdogan
2017-03-03 19:23             ` Tejun Heo
2017-03-04  1:40               ` [PATCH v3] " Tahsin Erdogan
2017-03-04 19:23                 ` Tejun Heo
2017-03-05 14:12                   ` [PATCH v4] " Tahsin Erdogan
2017-03-05 14:24                     ` Tahsin Erdogan
2017-03-06 20:03                     ` Tejun Heo
2017-03-09  8:05                       ` [PATCH v5] " Tahsin Erdogan
2017-03-09 18:27                         ` Tejun Heo [this message]
2017-03-11 22:42                         ` Jens Axboe
2017-03-11 22:52                           ` Jens Axboe
2017-03-12  4:35                             ` Tahsin Erdogan
2017-03-13 14:32                               ` Jens Axboe
2017-03-13 16:17                                 ` Tahsin Erdogan
2017-03-24 21:56                                   ` [PATCH] " Tahsin Erdogan
2017-03-24 22:04                                     ` Jens Axboe
2017-03-28 21:53                                       ` Tejun Heo
2017-03-28 21:59                         ` [PATCH v5] " Jens Axboe
2017-03-28 22:01                           ` Tahsin Erdogan
2017-03-09  5:25                 ` [lkp-robot] [blkcg] ad63af3cb7: BUG:sleeping_function_called_from_invalid_context_at_mm/slab.h kernel test robot
2017-03-09  7:59                   ` Tahsin Erdogan

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