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From: Jens Axboe <axboe@fb.com>
To: David Rientjes <rientjes@google.com>
Cc: Lars Ellenberg <drbd-dev@lists.linbit.com>,
	<linux-kernel@vger.kernel.org>, <drbd-user@lists.linbit.com>
Subject: Re: [patch 1/2] block, drbd: fix drbd_req_new() initialization
Date: Sat, 7 Mar 2015 18:03:30 -0700	[thread overview]
Message-ID: <54FB9FE2.5040707@fb.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1503071650270.2926@chino.kir.corp.google.com>

On 03/07/2015 05:53 PM, David Rientjes wrote:
> On Sat, 7 Mar 2015, Jens Axboe wrote:
> 
>>> mempool_alloc() does not support __GFP_ZERO since elements may come from
>>> memory that has already been released by mempool_free().
>>>
>>> Remove __GFP_ZERO from mempool_alloc() in drbd_req_new() and properly
>>> initialize it to 0.
>>
>> You should add it to mempool instead, avoid having this issue show up for
>> other folks as well. It'd be trivial to do. Normal ->alloc() should honor
>> __GFP_ZERO, just do the same manually for removing an item from the internal
>> pool.
>>
> 
> Umm, it's not trivial to do and wouldn't make sense to do it.  Mempools 

Uhm, it would make sense, though.

> don't know the element size, in other words it wouldn't know the length to 
> memset() to 0 for mempool_alloc().  It shouldn't be modified to know the 
> element size since elements are allocated by the implementation of 
> mempool_alloc_t and they could easily become inconsistent.  This patch is 
> what you want to merge, really.
> 

I forgot we don't have the size in there. Then I would suggest adding a
WARN_ON() for __GFP_ZERO being set in mempool_alloc(), at the very least.

-- 
Jens Axboe


  reply	other threads:[~2015-03-08  1:03 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-08  0:24 David Rientjes
2015-03-08  0:24 ` [patch 2/2] block, drbd: use mempool_create_slab_pool() David Rientjes
2015-03-08  0:33 ` [patch 1/2] block, drbd: fix drbd_req_new() initialization Jens Axboe
2015-03-08  0:53   ` David Rientjes
2015-03-08  1:03     ` Jens Axboe [this message]
2015-03-08  1:27       ` David Rientjes
2015-03-08  1:45         ` Jens Axboe
2015-03-13 23:24         ` David Rientjes
2015-03-10 10:38 ` [DRBD-user] " Lars Ellenberg
2015-03-10 19:28   ` David Rientjes

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