[PATCH] tmpfs: fix mount mpol nodelist parsing

I've been dissatisfied with the mpol_nodelist mount option which was
added to tmpfs earlier in -rc.  Replace it by mpol=policy:nodelist.

And it was broken: a nodelist is a comma-separated list of numbers and
ranges; the mount options are a comma-separated list of token=values.
Whoops, blindly strsep'ing on commas doesn't work so well: since we've
no numeric tokens, and unlikely to add them, use that to distinguish.

Move the mpol= parsing to shmem_parse_mpol under CONFIG_NUMA, reject
all its options as invalid if not NUMA.  /proc shows MPOL_PREFERRED
as "prefer", so use that name for the policy instead of "preferred".

Enforce that mpol=default has no nodelist; that mpol=prefer has one
node only; that mpol=bind has a nodelist; but let mpol=interleave use
node_online_map if no nodelist given.  Describe this in tmpfs.txt.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Acked-by: Robin Holt <holt@sgi.com>
Acked-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 69 insertions, 12 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index f7ac7b812f9..7c455fbaff7 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -45,6 +45,7 @@
 #include <linux/swapops.h>
 #include <linux/mempolicy.h>
 #include <linux/namei.h>
+#include <linux/ctype.h>
 #include <asm/uaccess.h>
 #include <asm/div64.h>
 #include <asm/pgtable.h>
@@ -874,6 +875,51 @@ redirty:
 }
 
 #ifdef CONFIG_NUMA
+static int shmem_parse_mpol(char *value, int *policy, nodemask_t *policy_nodes)
+{
+        char *nodelist = strchr(value, ':');
+        int err = 1;
+
+        if (nodelist) {
+                /* NUL-terminate policy string */
+                *nodelist++ = '\0';
+                if (nodelist_parse(nodelist, *policy_nodes))
+                        goto out;
+        }
+        if (!strcmp(value, "default")) {
+                *policy = MPOL_DEFAULT;
+                /* Don't allow a nodelist */
+                if (!nodelist)
+                        err = 0;
+        } else if (!strcmp(value, "prefer")) {
+                *policy = MPOL_PREFERRED;
+                /* Insist on a nodelist of one node only */
+                if (nodelist) {
+                        char *rest = nodelist;
+                        while (isdigit(*rest))
+                                rest++;
+                        if (!*rest)
+                                err = 0;
+                }
+        } else if (!strcmp(value, "bind")) {
+                *policy = MPOL_BIND;
+                /* Insist on a nodelist */
+                if (nodelist)
+                        err = 0;
+        } else if (!strcmp(value, "interleave")) {
+                *policy = MPOL_INTERLEAVE;
+                /* Default to nodes online if no nodelist */
+                if (!nodelist)
+                        *policy_nodes = node_online_map;
+                err = 0;
+        }
+out:
+        /* Restore string for error message */
+        if (nodelist)
+                *--nodelist = ':';
+        return err;
+}
+
 static struct page *shmem_swapin_async(struct shared_policy *p,
                                        swp_entry_t entry, unsigned long idx)
 {
@@ -926,6 +972,11 @@ shmem_alloc_page(gfp_t gfp, struct shmem_inode_info *info,
         return page;
 }
 #else
+static inline int shmem_parse_mpol(char *value, int *policy, nodemask_t *policy_nodes)
+{
+        return 1;
+}
+
 static inline struct page *
 shmem_swapin(struct shmem_inode_info *info,swp_entry_t entry,unsigned long idx)
 {
@@ -1859,7 +1910,23 @@ static int shmem_parse_options(char *options, int *mode, uid_t *uid,
 {
         char *this_char, *value, *rest;
 
-        while ((this_char = strsep(&options, ",")) != NULL) {
+        while (options != NULL) {
+                this_char = options;
+                for (;;) {
+                        /*
+                         * NUL-terminate this option: unfortunately,
+                         * mount options form a comma-separated list,
+                         * but mpol's nodelist may also contain commas.
+                         */
+                        options = strchr(options, ',');
+                        if (options == NULL)
+                                break;
+                        options++;
+                        if (!isdigit(*options)) {
+                                options[-1] = '\0';
+                                break;
+                        }
+                }
                 if (!*this_char)
                         continue;
                 if ((value = strchr(this_char,'=')) != NULL) {
@@ -1910,18 +1977,8 @@ static int shmem_parse_options(char *options, int *mode, uid_t *uid,
                         if (*rest)
                                 goto bad_val;
                 } else if (!strcmp(this_char,"mpol")) {
-                        if (!strcmp(value,"default"))
-                                *policy = MPOL_DEFAULT;
-                        else if (!strcmp(value,"preferred"))
-                                *policy = MPOL_PREFERRED;
-                        else if (!strcmp(value,"bind"))
-                                *policy = MPOL_BIND;
-                        else if (!strcmp(value,"interleave"))
-                                *policy = MPOL_INTERLEAVE;
-                        else
+                        if (shmem_parse_mpol(value,policy,policy_nodes))
                                 goto bad_val;
-                } else if (!strcmp(this_char,"mpol_nodelist")) {
-                        nodelist_parse(value, *policy_nodes);
                 } else {
                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
                                this_char);