From a43361cf3cb6fb6431fdbfb0f3ef26a334826160 Mon Sep 17 00:00:00 2001
From: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
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 <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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
mm/shmem.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index 9435f298dd7556..177c7a7d2bb38c 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;
}
--
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