Allow huge page allocations to use GFP_HIGH_MOVABLE

Huge pages are not movable so are not allocated from ZONE_MOVABLE.  However,
as ZONE_MOVABLE will always have pages that can be migrated or reclaimed, it
can be used to satisfy hugepage allocations even when the system has been
running a long time.  This allows an administrator to resize the hugepage pool
at runtime depending on the size of ZONE_MOVABLE.

This patch adds a new sysctl called hugepages_treat_as_movable.  When a
non-zero value is written to it, future allocations for the huge page pool
will use ZONE_MOVABLE.  Despite huge pages being non-movable, we do not
introduce additional external fragmentation of note as huge pages are always
the largest contiguous block we care about.

[akpm@linux-foundation.org: various fixes]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 4c0f99996811..9f4e9b95e8f2 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1203,7 +1203,8 @@ static inline unsigned interleave_nid(struct mempolicy *pol,
 
 #ifdef CONFIG_HUGETLBFS
 /* Return a zonelist suitable for a huge page allocation. */
-struct zonelist *huge_zonelist(struct vm_area_struct *vma, unsigned long addr)
+struct zonelist *huge_zonelist(struct vm_area_struct *vma, unsigned long addr,
+                                                        gfp_t gfp_flags)
 {
         struct mempolicy *pol = get_vma_policy(current, vma, addr);
 
@@ -1211,7 +1212,7 @@ struct zonelist *huge_zonelist(struct vm_area_struct *vma, unsigned long addr)
                 unsigned nid;
 
                 nid = interleave_nid(pol, vma, addr, HPAGE_SHIFT);
-                return NODE_DATA(nid)->node_zonelists + gfp_zone(GFP_HIGHUSER);
+                return NODE_DATA(nid)->node_zonelists + gfp_zone(gfp_flags);
         }
         return zonelist_policy(GFP_HIGHUSER, pol);
 }