linux-kernel - Re: [PATCH] mm: non-atomically mark page accessed during page cache allocation where possible -fix

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Message-Id: <20140521151142.9d084dd64251bce4c44c214d@linux-foundation.org>
Date:	Wed, 21 May 2014 15:11:42 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Johannes Weiner <hannes@...xchg.org>,
	Vlastimil Babka <vbabka@...e.cz>, Jan Kara <jack@...e.cz>,
	Michal Hocko <mhocko@...e.cz>, Hugh Dickins <hughd@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Dave Hansen <dave.hansen@...el.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>,
	Linux-FSDevel <linux-fsdevel@...r.kernel.org>,
	Prabhakar Lad <prabhakar.csengg@...il.com>
Subject: Re: [PATCH] mm: non-atomically mark page accessed during page cache
 allocation where possible -fix

On Wed, 21 May 2014 13:09:16 +0100 Mel Gorman <mgorman@...e.de> wrote:

> > From: Andrew Morton <akpm@...ux-foundation.org>
> > Subject: mm/shmem.c: don't run init_page_accessed() against an uninitialised pointer
> > 
> > If shmem_getpage() returned an error then it didn't necessarily initialise
> > *pagep.  So shmem_write_begin() shouldn't be playing with *pagep in this
> > situation.
> > 
> > Fixes an oops when "mm: non-atomically mark page accessed during page
> > cache allocation where possible" (quite reasonably) left *pagep
> > uninitialized.
> > 
> > Reported-by: Prabhakar Lad <prabhakar.csengg@...il.com>
> > Cc: Johannes Weiner <hannes@...xchg.org>
> > Cc: Vlastimil Babka <vbabka@...e.cz>
> > Cc: Jan Kara <jack@...e.cz>
> > Cc: Michal Hocko <mhocko@...e.cz>
> > Cc: Hugh Dickins <hughd@...gle.com>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Dave Hansen <dave.hansen@...el.com>
> > Cc: Mel Gorman <mgorman@...e.de>
> > Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> 
> Acked-by: Mel Gorman <mgorman@...e.de>

What to do with
http://ozlabs.org/~akpm/mmots/broken-out/mm-non-atomically-mark-page-accessed-during-page-cache-allocation-where-possible-fix.patch?

We shouldn't need it any more.  otoh it's pretty harmless.  otooh it
will hide bugs such as this one.

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