[parted-devel] [PATCH] unneeded stats...

[Karel Zak]

On Mon, Feb 23, 2009 at 04:10:58PM +0000, Bryn M. Reeves wrote:
> Joel Granados wrote:
> > On Mon, Feb 23, 2009 at 03:50:02PM +0000, Bryn M. Reeves wrote:
> >> Joel Granados Moreno wrote:
> >>> Hello List
> >>>
> >>> Here is the reviewed patch for the unneeded stats that we are doing when
> >>> looking for mounted devices.  It is modified to not search for "server
> >>> strings" (//servername/path/to/somewhere)
> >>>
> >>> Review appreciated
> >> There's a slight gotcha with this approach in that the kernel will  
> >> honour the names that userspace gives it in a mount syscall. E.g. if I  
> >> mount /dev/sda then that's what appears in /proc/mounts but if I mount  
> >> //dev/sda, then that's the string that will appear.
> >>
> >> E.g.:
> >>
> >> # mount //dev/mapper/cyan /mnt
> >> # grep cyan /proc/mounts
> >> //dev/mapper/cyan /mnt ext3 rw,data=ordered 0 0
> > 
> > I tested for this situation in my fedora10 environment  With the latest
> > parted.  And if I do the mount with "//" /proc/mounts will show it with
> 
> Yep, just confirmed that on my f10 box so this has changed somewhere 
> between RHEL5's 2.6.18 (where I tested previously) and current upstream.

 The current mount(8) always canonicalize all paths, so it never call
 mount(2) syscall with '//'. (RHEL5 != current:-) The more important
 thing is kernel behaviour. You cannot rely on mount(8) -- there is
 more ways how to mount devices.

 I think the best way how to resolve this problem is to call stat(2)
 and ignore everything from /proc/mounts what is not S_IFBLK. It seems
 that paths are unreliable...

    Karel

-- 
 Karel Zak  <kzak at redhat.com>