mempolicy: rework shmem mpol parsing and display

mm/shmem.c currently contains functions to parse and display memory policy
strings for the tmpfs 'mpol' mount option.  Move this to mm/mempolicy.c with
the rest of the mempolicy support.  With subsequent patches, we'll be able to
remove knowledge of the details [mode, flags, policy, ...] completely from
shmem.c

1) replace shmem_parse_mpol() in mm/shmem.c with mpol_parse_str() in
   mm/mempolicy.c.  Rework to use the policy_types[] array [used by
   mpol_to_str()] to look up mode by name.

2) use mpol_to_str() to format policy for shmem_show_mpol().  mpol_to_str()
   expects a pointer to a struct mempolicy, so temporarily construct one.
   This will be replaced with a reference to a struct mempolicy in the tmpfs
   superblock in a subsequent patch.

   NOTE 1: I changed mpol_to_str() to use a colon ':' rather than an equal
   sign '=' as the nodemask delimiter to match mpol_parse_str() and the
   tmpfs/shmem mpol mount option formatting that now uses mpol_to_str().  This
   is a user visible change to numa_maps, but then the addition of the mode
   flags already changed the display.  It makes sense to me to have the mounts
   and numa_maps display the policy in the same format.  However, if anyone
   objects strongly, I can pass the desired nodemask delimeter as an arg to
   mpol_to_str().

   Note 2: Like show_numa_map(), I don't check the return code from
   mpol_to_str().  I do use a longer buffer than the one provided by
   show_numa_map(), which seems to have sufficed so far.

Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index b0fab9e..dcc1737 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -214,6 +214,13 @@ static inline void check_highest_zone(enum zone_type k)
 int do_migrate_pages(struct mm_struct *mm,
 	const nodemask_t *from_nodes, const nodemask_t *to_nodes, int flags);
 
+
+#ifdef CONFIG_TMPFS
+extern int mpol_parse_str(char *str, unsigned short *mode,
+			unsigned short *mode_flags, nodemask_t *policy_nodes);
+
+extern int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol);
+#endif
 #else
 
 struct mempolicy {};
@@ -313,6 +320,20 @@ static inline int do_migrate_pages(struct mm_struct *mm,
 static inline void check_highest_zone(int k)
 {
 }
+
+#ifdef CONFIG_TMPFS
+static inline int mpol_parse_str(char *value, unsigned short *policy,
+				unsigned short flags, nodemask_t *policy_nodes)
+{
+	return 1;
+}
+
+static inline int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
+{
+	return 0;
+}
+#endif
+
 #endif /* CONFIG_NUMA */
 #endif /* __KERNEL__ */