linux-kernel - Re: [PATCH] slub: missing test for partial pages flush work in flush

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Date:	Sun, 13 May 2012 09:53:15 +0300
From:	Gilad Ben-Yossef <gilad@...yossef.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	majianpeng <majianpeng@...il.com>, linux-mm <linux-mm@...ck.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] slub: missing test for partial pages flush work in flush_all

On Fri, May 11, 2012 at 7:14 PM, Christoph Lameter <cl@...ux.com> wrote:
> Didn't I already ack this before?
>
> Acked-by: Christoph Lameter <cl@...ux.com>
>

Yes, you did, but the patch description and title was lacking and
Majianpeng kindly fixed it, hence the re-send, I guess.

I've added Andrew, since he took my original commit that introduces
the bug that this patch by Majianpeng  fixes (and also LKML).

This fix really needs to get into 3.4, otherwise we'll be breaking
slub. What's the best way to go about that?

Thanks!
Gilad

> On Fri, 11 May 2012, majianpeng wrote:
>
>> Subject: [PATCH] slub: missing test for partial pages flush work in flush_all
>>
>> Find some kernel message like:
>> SLUB raid5-md127: kmem_cache_destroy called for cache that still has objects.
>> Pid: 6143, comm: mdadm Tainted: G           O 3.4.0-rc6+        #75
>> Call Trace:
>> [<ffffffff811227f8>] kmem_cache_destroy+0x328/0x400
>> [<ffffffffa005ff1d>] free_conf+0x2d/0xf0 [raid456]
>> [<ffffffffa0060791>] stop+0x41/0x60 [raid456]
>> [<ffffffffa000276a>] md_stop+0x1a/0x60 [md_mod]
>> [<ffffffffa000c974>] do_md_stop+0x74/0x470 [md_mod]
>> [<ffffffffa000d0ff>] md_ioctl+0xff/0x11f0 [md_mod]
>> [<ffffffff8127c958>] blkdev_ioctl+0xd8/0x7a0
>> [<ffffffff8115ef6b>] block_ioctl+0x3b/0x40
>> [<ffffffff8113b9c6>] do_vfs_ioctl+0x96/0x560
>> [<ffffffff8113bf21>] sys_ioctl+0x91/0xa0
>> [<ffffffff816e9d22>] system_call_fastpath+0x16/0x1b
>>
>> Then using kmemleak can found those messages:
>> unreferenced object 0xffff8800b6db7380 (size 112):
>>   comm "mdadm", pid 5783, jiffies 4294810749 (age 90.589s)
>>   hex dump (first 32 bytes):
>>     01 01 db b6 ad 4e ad de ff ff ff ff ff ff ff ff  .....N..........
>>     ff ff ff ff ff ff ff ff 98 40 4a 82 ff ff ff ff  .........@......
>>   backtrace:
>>     [<ffffffff816b52c1>] kmemleak_alloc+0x21/0x50
>>     [<ffffffff8111a11b>] kmem_cache_alloc+0xeb/0x1b0
>>     [<ffffffff8111c431>] kmem_cache_open+0x2f1/0x430
>>     [<ffffffff8111c6c8>] kmem_cache_create+0x158/0x320
>>     [<ffffffffa008f979>] setup_conf+0x649/0x770 [raid456]
>>     [<ffffffffa009044b>] run+0x68b/0x840 [raid456]
>>     [<ffffffffa000bde9>] md_run+0x529/0x940 [md_mod]
>>     [<ffffffffa000c218>] do_md_run+0x18/0xc0 [md_mod]
>>     [<ffffffffa000dba8>] md_ioctl+0xba8/0x11f0 [md_mod]
>>     [<ffffffff81272b28>] blkdev_ioctl+0xd8/0x7a0
>>     [<ffffffff81155bfb>] block_ioctl+0x3b/0x40
>>     [<ffffffff811326d6>] do_vfs_ioctl+0x96/0x560
>>     [<ffffffff81132c31>] sys_ioctl+0x91/0xa0
>>     [<ffffffff816dd3a2>] system_call_fastpath+0x16/0x1b
>>     [<ffffffffffffffff>] 0xffffffffffffffff
>>
>> This bug introduced by Commit a8364d5555b2030d093cde0f0795.The
>> commit did not include checks for per cpu partial pages being present on a
>> cpu.
>>
>> Signed-off-by: majianpeng <majianpeng@...il.com>
>> ---
>>  mm/slub.c |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/mm/slub.c b/mm/slub.c
>> index ffe13fd..6fce08f 100644
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -2040,7 +2040,7 @@ static bool has_cpu_slab(int cpu, void *info)
>>       struct kmem_cache *s = info;
>>       struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);
>>
>> -     return !!(c->page);
>> +     return c->page || c->partial;
>>  }
>>
>>  static void flush_all(struct kmem_cache *s)
>>



-- 
Gilad Ben-Yossef
Chief Coffee Drinker
gilad@...yossef.com
Israel Cell: +972-52-8260388
US Cell: +1-973-8260388
http://benyossef.com

"If you take a class in large-scale robotics, can you end up in a
situation where the homework eats your dog?"
 -- Jean-Baptiste Queru
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