[PATCH] Add tmpfs options for memory placement policies

Anything that writes into a tmpfs filesystem is liable to disproportionately
decrease the available memory on a particular node.  Since there's no telling
what sort of application (e.g.  dd/cp/cat) might be dropping large files
there, this lets the admin choose the appropriate default behavior for their
site's situation.

Introduce a tmpfs mount option which allows specifying a memory policy and
a second option to specify the nodelist for that policy.  With the default
policy, tmpfs will behave as it does today.  This patch adds support for
preferred, bind, and interleave policies.

The default policy will cause pages to be added to tmpfs files on the node
which is doing the writing.  Some jobs expect a single process to create
and manage the tmpfs files.  This results in a node which has a
significantly reduced number of free pages.

With this patch, the administrator can specify the policy and nodes for
that policy where they would prefer allocations.

This patch was originally written by Brent Casavant and Hugh Dickins.  I
added support for the bind and preferred policies and the mpol_nodelist
mount option.

Signed-off-by: Brent Casavant <bcasavan@sgi.com>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Robin Holt <holt@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 24 insertions, 0 deletions

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index b62cab575a84..3171f884d245 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1359,6 +1359,30 @@ restart:
         return 0;
 }
 
+void mpol_shared_policy_init(struct shared_policy *info, int policy,
+                                nodemask_t *policy_nodes)
+{
+        info->root = RB_ROOT;
+        spin_lock_init(&info->lock);
+
+        if (policy != MPOL_DEFAULT) {
+                struct mempolicy *newpol;
+
+                /* Falls back to MPOL_DEFAULT on any error */
+                newpol = mpol_new(policy, policy_nodes);
+                if (!IS_ERR(newpol)) {
+                        /* Create pseudo-vma that contains just the policy */
+                        struct vm_area_struct pvma;
+
+                        memset(&pvma, 0, sizeof(struct vm_area_struct));
+                        /* Policy covers entire file */
+                        pvma.vm_end = TASK_SIZE;
+                        mpol_set_shared_policy(info, &pvma, newpol);
+                        mpol_free(newpol);
+                }
+        }
+}
+
 int mpol_set_shared_policy(struct shared_policy *info,
                         struct vm_area_struct *vma, struct mempolicy *npol)
 {