Re: [PATCH 0/4] ipc/shm.c: increase the limits for SHMMAX, SHMALL

From: Davidlohr Bueso
Date: Tue May 06 2014 - 16:43:41 EST


On Tue, 2014-05-06 at 13:06 -0700, Davidlohr Bueso wrote:
> On Fri, 2014-05-02 at 15:16 +0200, Michael Kerrisk (man-pages) wrote:
> > Hi Manfred,
> >
> > On Mon, Apr 21, 2014 at 4:26 PM, Manfred Spraul
> > <manfred@xxxxxxxxxxxxxxxx> wrote:
> > > Hi all,
> > >
> > > the increase of SHMMAX/SHMALL is now a 4 patch series.
> > > I don't have ideas how to improve it further.
> >
> > On the assumption that your patches are heading to mainline, could you
> > send me a man-pages patch for the changes?
>
> Btw, I think that the code could still use some love wrt documentation.
> Andrew, please consider this for -next if folks agree. Thanks.
>
> 8<----------------------------------------------------------
>
> From: Davidlohr Bueso <davidlohr@xxxxxx>
> Subject: [PATCH] ipc,shm: document new limits in the uapi header
>
> This is useful in the future and allows users to
> better understand the reasoning behind the changes.
>
> Also use UL as we're dealing with it anyways.
>
> Signed-off-by: Davidlohr Bueso <davidlohr@xxxxxx>
> ---
> include/uapi/linux/shm.h | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/include/uapi/linux/shm.h b/include/uapi/linux/shm.h
> index 74e786d..e37fb08 100644
> --- a/include/uapi/linux/shm.h
> +++ b/include/uapi/linux/shm.h
> @@ -8,17 +8,19 @@
> #endif
>
> /*
> - * SHMMAX, SHMMNI and SHMALL are upper limits are defaults which can
> - * be modified by sysctl.
> + * SHMMNI, SHMMAX and SHMALL are the default upper limits which can be
> + * modified by sysctl. Both SHMMAX and SHMALL have their default values
> + * to the maximum limit which is as large as it can be without helping
> + * userspace overflow the values. There is really nothing the kernel
> + * can do to avoid this any variables. It is therefore not advised to
^^^^^^^^^^ should be 'further', sorry.

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