linux-kernel - Re: possible regression on 3.13 when calling flush_dcache

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Message-ID: <20131223224435.GD16592@ldesroches-Latitude-E6320>
Date:	Mon, 23 Dec 2013 23:44:35 +0100
From:	Ludovic Desroches <ludovic.desroches@...el.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>, <linux-mmc@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
CC:	Ludovic Desroches <ludovic.desroches@...el.com>
Subject: Re: possible regression on 3.13 when calling flush_dcache_page

On Fri, Dec 20, 2013 at 09:08:51AM +0100, Ludovic Desroches wrote:
> Hello,
> 
> On Wed, Dec 18, 2013 at 04:21:17PM +0900, Joonsoo Kim wrote:
> > On Mon, Dec 16, 2013 at 03:43:43PM +0100, Ludovic Desroches wrote:
> > > Hello,
> > > 
> > > On Fri, Dec 13, 2013 at 10:59:09AM +0900, Joonsoo Kim wrote:
> > > > On Thu, Dec 12, 2013 at 03:36:19PM +0100, Ludovic Desroches wrote:
> > > > > fix mmc mailing list address error
> > > > > 
> > > > > On Thu, Dec 12, 2013 at 03:31:50PM +0100, Ludovic Desroches wrote:
> > > > > > Hi,
> > > > > > 
> > > > > > With v3.13-rc3 I have an error when the atmel-mci driver calls
> > > > > > flush_dcache_page (log at the end of the message).
> > > > > > 
> > > > > > Since I didn't have it before, I did a git bisect and the commit introducing
> > > > > > the error is the following one:
> > > > > > 
> > > > > > 106a74e slab: replace free and inuse in struct slab with newly introduced active
> > > > > > 
> > > > > > I don't know if this commit has introduced a bug or if it has revealed a bug
> > > > > > in the atmel-mci driver.
> > > > 
> > > > Hello,
> > > > 
> > > > I think that this commit may not introduce a bug. This patch remove one
> > > > variable on slab management structure and replace variable name. So there
> > > > is no functional change.
> > > > 
> > > 
> > > If I have reverted this patch and other ones you did on top of it and
> > > the issue disappear.
> > 
> > Hello,
> > 
> > Could you give me your '/proc/slabinfo' before/after this commit (106a74e)?
> > 
> > And how about testing with artificially increasing size of struct slab on
> > top of this commit (106a74e)?
> > 
> > I really wonder why the problem happens, because this doesn't cause any
> > functional change as far as I know. Only side-effect from this patch is
> > decreasing size of struct slab.
> 
> Sorry I am not at the office, I have tried to reproduce it with a
> different device and a different sdcard but without success. I'll test
> it on Monday.

I am still not at the office but I get the same device and the same
sdcard and I don't reproduce it. I am not totally in the same
conditions. It seems there is an extra parameter causing this bug but I
don't figure out which one at the moment.

> 
> Regards
> 
> Ludovic
> 
> > 
> > Thanks.
> > 
> > diff --git a/mm/slab.c b/mm/slab.c
> > index 2ec2336..d2240fd 100644
> > --- a/mm/slab.c
> > +++ b/mm/slab.c
> > @@ -174,6 +174,7 @@ struct slab {
> >         struct {
> >                 struct list_head list;
> >                 void *s_mem;            /* including colour offset */
> > +               unsigned int x;
> >                 unsigned int active;    /* num of objs active in slab */
> >         };
> >  };
> > 
> > > 
> > > > I doubt that side-effect of this patch reveals a bug in other place.
> > > > Side-effect is reduced memory usage for slab management structure. It would
> > > > makes some slabs have more objects with more density since slab management
> > > > structure is sometimes on the page for objects. So if it diminishes, more
> > > > objects can be in the page.
> > > > 
> > > > Anyway, I will look at it more. If you have any progress, please let me know.
> > > 
> > > No progress at the moment.
> > 
> > --
> > To unsubscribe, send a message with 'unsubscribe linux-mm' in
> > the body to majordomo@...ck.org.  For more info on Linux MM,
> > see: http://www.linux-mm.org/ .
> > Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>
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