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

From: Davidlohr Bueso
Date: Tue May 06 2014 - 18:08:10 EST


On Tue, 2014-05-06 at 22:40 +0200, Michael Kerrisk (man-pages) wrote:
> Hi Davidlohr,
>
> On Tue, May 6, 2014 at 10:06 PM, Davidlohr Bueso <davidlohr@xxxxxx> 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.
>
> (Agreed.)
>
> > 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
>
> Something is wrong in the line above (missing word(s)?) ("are upper
> limits are defaults")
>
> > - * 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
>
> Something is missing in that last line.
>
> > + * make them any larger. This is suitable for both 32 and 64-bit systems.
>
> "This" is not so clear. I suggest replacing with an actual noun.

Good point. Perhaps 'These values are ...' would do instead.

Thanks,
Davidlohr

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