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Date: Tue, 08 Apr 2008 01:42:28 +0300
From: Pekka Enberg <penberg@cs.helsinki.fi>
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To: Linus Torvalds <torvalds@linux-foundation.org>
CC: Hugh Dickins <hugh@veritas.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Christoph Lameter <clameter@sgi.com>,
       James Bottomley <James.Bottomley@HansenPartnership.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>,
       Jens Axboe <jens.axboe@oracle.com>, "Rafael J. Wysocki" <rjw@sisk.pl>,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH] scsi: fix sense_slab/bio swapping livelock
References: <Pine.LNX.4.64.0804062348001.19446@blonde.site>  <Pine.LNX.4.64.0804062213230.18148@schroedinger.engr.sgi.com>  <Pine.LNX.4.64.0804072000410.18591@blonde.site> <1207598115.29991.23.camel@lappy> <Pine.LNX.4.64.0804072121320.28744@blonde.site> <47FA8B5A.5090104@cs.helsinki.fi> <47FA8CB0.6070106@cs.helsinki.fi> <alpine.LFD.1.00.0804071409150.2886@woody.linux-foundation.org> <47FA937E.6000009@cs.helsinki.fi> <47FA94AE.4070803@cs.helsinki.fi> <Pine.LNX.4.64.0804080104170.23980@sbz-30.cs.Helsinki.FI> <alpine.LFD.1.00.0804071515320.2886@woody.linux-foundation.org>
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On Tue, 8 Apr 2008, Pekka J Enberg wrote:
>> So something like the following (totally untested) patch modulo the 
>> pre-allocation bits.

Linus Torvalds wrote:
> Hmm. I didn't check, but won't this cause problems on the freeing path 
> when we call kmem_cache_free() on the result but with the wrong "struct 
> kmem_cache" pointer?

Aah, yes. I was thinking of kmalloc() here for which it works as 
expected because kfree() will return the page to the proper cache. But 
we can relax the rules of kmem_cache_free() a bit to make this work (but 
perhaps add a WARN_ON() there if cache doesn't match page->slab).

			Pekka