Re: possible regression on 3.13 when calling flush_dcache_page

From: Ludovic Desroches
Date: Fri Dec 20 2013 - 03:09:05 EST


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.

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.
>
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