From a43361cf3cb6fb6431fdbfb0f3ef26a334826160 Mon Sep 17 00:00:00 2001 From: Lee Schermerhorn Date: Mon, 28 Apr 2008 02:12:36 -0700 Subject: [PATCH] mempolicy: fix parsing of tmpfs mpol mount option 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: Lee Schermerhorn Cc: David Rientjes Cc: Paul Jackson Cc: Christoph Lameter Cc: Andi Kleen Cc: Eric Whitney Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/shmem.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index 9435f298dd7..177c7a7d2bb 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1125,20 +1125,26 @@ static int shmem_parse_mpol(char *value, unsigned short *policy, *policy_nodes = node_states[N_HIGH_MEMORY]; err = 0; } + + *mode_flags = 0; if (flags) { + /* + * Currently, we only support two mutually exclusive + * mode flags. + */ if (!strcmp(flags, "static")) *mode_flags |= MPOL_F_STATIC_NODES; - if (!strcmp(flags, "relative")) + else if (!strcmp(flags, "relative")) *mode_flags |= MPOL_F_RELATIVE_NODES; - - if ((*mode_flags & MPOL_F_STATIC_NODES) && - (*mode_flags & MPOL_F_RELATIVE_NODES)) - err = 1; + else + err = 1; /* unrecognized flag */ } out: /* Restore string for error message */ if (nodelist) *--nodelist = ':'; + if (flags) + *--flags = '='; return err; } -- 2.41.1