[systemd-devel] PATCH: do not run fsck on tmpfs mountpoint

[Karel Zak]

On Wed, Nov 02, 2011 at 12:15:29PM +0100, Kay Sievers wrote:
> On Wed, Nov 2, 2011 at 11:21, Frederic Crozat <fcrozat at suse.com> wrote:
> > Le mardi 01 novembre 2011 à 16:54 +0100, Lennart Poettering a écrit :
> >> On Thu, 27.10.11 16:19, Frederic Crozat (fcrozat at suse.com) wrote:
> >>
> >> > You really don't want to fsck a tmpfs, even if passno is non-null (it
> >> > was causing many issue, forcing system to go to emergency).
> >>
> >> Hmm, I wonder if this is the right fix. I wonder what fsck -a does if it
> >> finds a passno != 0 for an entry where /sbin/fsck.xxx. If that fails on
> >> it we should probably do so too. If it silently ignores passno != 0
> >> where the fsck is missing then we probably should implement a similar
> >> logic. However doing an explicit check for tmpfs sounds wrong to me:
> >> there are other fs where fsck makes little sense, and we would have to
> >> either check them all or none?
> >
> > I've just checked fsck code :
> > - it has a list of "ignore" filesystems :
> 
> Please let's not start copying that stuff, fsck is hardly an example
> how things should be done today. Such lists can never be up-to-date,
> and they are not today.
> 
> I guess, if such broken configs should be supported, which I'm really
> not sure about, fsck itself should be made to find that out and return
> successful without doing anything. Such things should not be guarded
> in systemd with just another static blacklist.
> 
> Not sure if there are valid use cases, maybe we are able to skip all
> mounts which are not backed by a device, where major(s.st_rdev) == 0?

 Unfortunately major(s.st_rdev) is probably useless, try to mount any
 btrfs device :-)

 $ ll /dev/sdb1
 brw-rw---- 1 root disk 8, 17 Nov  2 14:59 /dev/sdb1

 $ findmnt /mnt
 TARGET SOURCE    FSTYPE OPTIONS
 /mnt   /dev/sdb1 btrfs  rw,relatime,ssd

 ./a /mnt
 0:42

 (./a is stat(argv[1], &st) call)


 BTW, in systemd/src/fsck.c I see:

        /* Virtual root devices don't need an fsck */
        if (major(st.st_dev) == 0)
              return 0;

 it means that btrfs root will be interpreted as a virtual device :-)

    Karel

-- 
 Karel Zak  <kzak at redhat.com>
 http://karelzak.blogspot.com