[PATCH 8/8] prepare to remove /proc/sys/vm/hugepages_treat_as_movable

[Naoya Horiguchi]

Now hugepages are definitely movable. So allocating hugepages from
ZONE_MOVABLE is natural and we have no reason to keep this parameter.
In order to allow userspace to prepare for the removal, let's leave
this sysctl handler as noop for a while.

ChangeLog v3:
 - use WARN_ON_ONCE

ChangeLog v2:
 - shift to noop function instead of completely removing the parameter
 - rename patch title

Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
---
 Documentation/sysctl/vm.txt | 13 ++-----------
 mm/hugetlb.c                | 17 ++++++-----------
 2 files changed, 8 insertions(+), 22 deletions(-)

diff --git v3.11-rc1.orig/Documentation/sysctl/vm.txt v3.11-rc1/Documentation/sysctl/vm.txt
index 36ecc26..6e211a1 100644
--- v3.11-rc1.orig/Documentation/sysctl/vm.txt
+++ v3.11-rc1/Documentation/sysctl/vm.txt
@@ -200,17 +200,8 @@ fragmentation index is <= extfrag_threshold. The default value is 500.
 
 hugepages_treat_as_movable
 
-This parameter is only useful when kernelcore= is specified at boot time to
-create ZONE_MOVABLE for pages that may be reclaimed or migrated. Huge pages
-are not movable so are not normally allocated from ZONE_MOVABLE. A non-zero
-value written to hugepages_treat_as_movable allows huge pages to be allocated
-from ZONE_MOVABLE.
-
-Once enabled, the ZONE_MOVABLE is treated as an area of memory the huge
-pages pool can easily grow or shrink within. Assuming that applications are
-not running that mlock() a lot of memory, it is likely the huge pages pool
-can grow to the size of ZONE_MOVABLE by repeatedly entering the desired value
-into nr_hugepages and triggering page reclaim.
+This parameter is obsolete and planned to be removed. The value has no effect
+on kernel's behavior.
 
 ==============================================================
 
diff --git v3.11-rc1.orig/mm/hugetlb.c v3.11-rc1/mm/hugetlb.c
index 9575e8a..aab5aef 100644
--- v3.11-rc1.orig/mm/hugetlb.c
+++ v3.11-rc1/mm/hugetlb.c
@@ -34,7 +34,6 @@
 #include "internal.h"
 
 const unsigned long hugetlb_zero = 0, hugetlb_infinity = ~0UL;
-static gfp_t htlb_alloc_mask = GFP_HIGHUSER;
 unsigned long hugepages_treat_as_movable;
 
 int hugetlb_max_hstate __read_mostly;
@@ -546,7 +545,7 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
 retry_cpuset:
 	cpuset_mems_cookie = get_mems_allowed();
 	zonelist = huge_zonelist(vma, address,
-					htlb_alloc_mask, &mpol, &nodemask);
+					GFP_HIGHUSER_MOVABLE, &mpol, &nodemask);
 	/*
 	 * A child process with MAP_PRIVATE mappings created by their parent
 	 * have no page reserves. This check ensures that reservations are
@@ -562,7 +561,7 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
 
 	for_each_zone_zonelist_nodemask(zone, z, zonelist,
 						MAX_NR_ZONES - 1, nodemask) {
-		if (cpuset_zone_allowed_softwall(zone, htlb_alloc_mask)) {
+		if (cpuset_zone_allowed_softwall(zone, GFP_HIGHUSER_MOVABLE)) {
 			page = dequeue_huge_page_node(h, zone_to_nid(zone));
 			if (page) {
 				if (!avoid_reserve)
@@ -719,7 +718,7 @@ static struct page *alloc_fresh_huge_page_node(struct hstate *h, int nid)
 		return NULL;
 
 	page = alloc_pages_exact_node(nid,
-		htlb_alloc_mask|__GFP_COMP|__GFP_THISNODE|
+		GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_THISNODE|
 						__GFP_REPEAT|__GFP_NOWARN,
 		huge_page_order(h));
 	if (page) {
@@ -944,12 +943,12 @@ static struct page *alloc_buddy_huge_page(struct hstate *h, int nid)
 	spin_unlock(&hugetlb_lock);
 
 	if (nid == NUMA_NO_NODE)
-		page = alloc_pages(htlb_alloc_mask|__GFP_COMP|
+		page = alloc_pages(GFP_HIGHUSER_MOVABLE|__GFP_COMP|
 				   __GFP_REPEAT|__GFP_NOWARN,
 				   huge_page_order(h));
 	else
 		page = alloc_pages_exact_node(nid,
-			htlb_alloc_mask|__GFP_COMP|__GFP_THISNODE|
+			GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_THISNODE|
 			__GFP_REPEAT|__GFP_NOWARN, huge_page_order(h));
 
 	if (page && arch_prepare_hugepage(page)) {
@@ -2128,11 +2127,7 @@ int hugetlb_treat_movable_handler(struct ctl_table *table, int write,
 			void __user *buffer,
 			size_t *length, loff_t *ppos)
 {
-	proc_dointvec(table, write, buffer, length, ppos);
-	if (hugepages_treat_as_movable)
-		htlb_alloc_mask = GFP_HIGHUSER_MOVABLE;
-	else
-		htlb_alloc_mask = GFP_HIGHUSER;
+	WARN_ON_ONCE("This knob is obsolete and has no effect. It is scheduled for removal.\n");
 	return 0;
 }
 
-- 
1.8.3.1

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