• Lee Schermerhorn's avatar
    mempolicy: fix parsing of tmpfs mpol mount option · a43361cf
    Lee Schermerhorn authored
    Parsing of new mode flags in the tmpfs mpol mount option is slightly broken:
    
    Setting a valid flag works OK:
    	#mount -o remount,mpol=bind=static:1-2 /dev/shm
    	#mount
    	...
    	tmpfs on /dev/shm type tmpfs (rw,mpol=bind=static:1-2)
    	...
    
    However, we can't remove them or change them, once we've
    set a valid flag:
    
    	#mount -o remount,mpol=bind:1-2 /dev/shm
    	#mount
    	...
    	tmpfs on /dev/shm type tmpfs (rw,mpol=bind:1-2)
    	...
    
    It SAYS it removed it, but that's just a copy of the input
    string.  If we now try to set it to a different flag, we
    get:
    
    	#mount -o remount,mpol=bind=relative:1-2 /dev/shm
    	mount: /dev/shm not mounted already, or bad option
    
    And on the console, we see:
    	tmpfs: Bad value 'bind' for mount option 'mpol'
    	                      ^ lost remainder of string
    
    Furthermore, bogus flags are accepted with out error.
    Granted, they are a no-op:
    
    	#mount -o remount,mpol=interleave=foo:0-3 /dev/shm
    	#mount
    	...
    	tmpfs on /dev/shm type tmpfs (rw,mpol=interleave=foo:0-3)
    
    Again, that's just a copy of the input string shown by the mount command.
    
    This patch fixes the behavior by pre-zeroing the flags so that only one of the
    mutually exclusive flags can be set at one time.  It also reports an error
    when an unrecognized flag is specified.
    
    The check for both flags being set is removed because it can't happen with
    this implementation.  If we ever want to support multiple non-exclusive flags,
    this area will need rework and we will need to check that any mutually
    exclusive flags aren't specified.
    Signed-off-by: default avatarLee Schermerhorn <lee.schermerhorn@hp.com>
    Cc: David Rientjes <rientjes@google.com>
    Cc: Paul Jackson <pj@sgi.com>
    Cc: Christoph Lameter <clameter@sgi.com>
    Cc: Andi Kleen <ak@suse.de>
    Cc: Eric Whitney <eric.whitney@hp.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    a43361cf
shmem.c 67.7 KB