[PATCH:shmfd 2/2] Use /var/tmp instead of /run/shm on non-linux OS'es

[Thomas Klausner]

On Fri, Nov 08, 2013 at 09:42:57AM -0500, Jasper St. Pierre wrote:
> We want to make sure we don't write files to disk. /tmp on some systems is
> backed by a disk, not tmpfs.

If you want real temporary files that don't survive a reboot, /tmp is
a better bet than /var/tmp.

See e.g.
http://refspecs.linuxfoundation.org/FHS_2.3/fhs-2.3.html#VARTMPTEMPORARYFILESPRESERVEDBETWEE
which says:

"The /var/tmp directory is made available for programs that require
temporary files or directories that are preserved between system
reboots. Therefore, data stored in /var/tmp is more persistent than
data in /tmp.

Files and directories located in /var/tmp must not be deleted when the
system is booted. Although data stored in /var/tmp is typically
deleted in a site-specific manner, it is recommended that deletions
occur at a less frequent interval than /tmp."

On NetBSD for example, /var/tmp is where the vi recovery files live.

 Thomas

> On Fri, Nov 8, 2013 at 2:53 AM, Mark Kettenis <mark.kettenis at xs4all.nl>wrote:
> 
> > > From: Alan Coopersmith <alan.coopersmith at oracle.com>
> > > Date: Thu,  7 Nov 2013 20:55:44 -0800
> > >
> > > Signed-off-by: Alan Coopersmith <alan.coopersmith at oracle.com>
> > > ---
> > >  Makefile |    9 +++++----
> > >  shmfd.c  |    4 ++++
> > >  2 files changed, 9 insertions(+), 4 deletions(-)
> >
> > Ah, is this the example code I have been looking for the last couple
> > of days?
> >
> > Anyway, wouldn't it be better to use /tmp instead of adding this
> > (admittedly small) #ifdef spaghetti?
> >
> > > diff --git a/Makefile b/Makefile
> > > index e77f938..672979e 100644
> > > --- a/Makefile
> > > +++ b/Makefile
> > > @@ -1,7 +1,8 @@
> > > -CFLAGS=-Wall -O0 -g $(shell pkg-config --cflags xcb-shm xcb-aux
> > xcb-dri3 xcb-present xshmfence)
> > > -LIBS=$(shell pkg-config --libs xcb-shm xcb-aux xcb-dri3 xcb-present
> > xshmfence)
> > > +CFLAGS=-Wall -O0 -g $(shell pkg-config --cflags xcb-shm xcb-aux
> > xcb-dri3 xcb-present) -m64
> > > +LIBS=$(LDFLAGS) $(shell pkg-config --libs xcb-shm xcb-aux xcb-dri3
> > xcb-present)
> > >
> > > -all: shmfd dri3 futex xfence present pipefence shmtest
> > > +#all: shmfd dri3 futex xfence present pipefence shmtest
> > > +all: shmfd present
> > >
> > >  SHMFD_OBJS=shmfd.o
> > >
> > > @@ -42,4 +43,4 @@ clean:
> > >       rm -f shmfd $(SHMFD_OBJS)
> > >       rm -f dri3 $(DRI3_OBJS)
> > >       rm -f futex $(FUTEX_OBJS)
> > > -     rm -f present $(PRESENT_OBJS)
> > > \ No newline at end of file
> > > +     rm -f present $(PRESENT_OBJS)
> > > diff --git a/shmfd.c b/shmfd.c
> > > index 4dee9de..cdd3889 100644
> > > --- a/shmfd.c
> > > +++ b/shmfd.c
> > > @@ -32,7 +32,11 @@ int
> > >  make_shm(int size, void **addrp)
> > >  {
> > >       void    *addr;
> > > +#ifdef linux
> > >       char    template[] = "/run/shm/shmfd-XXXXXX";
> > > +#else
> > > +     char    template[] = "/var/tmp/shmfd-XXXXXX";
> > > +#endif
> > >       int     fd = mkstemp(template);
> > >
> > >       if (fd < 0)
> > > --
> > > 1.7.9.2
> > >
> > > _______________________________________________
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> > >
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> >
> 
> 
> 
> -- 
>   Jasper

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