mm/compaction: pass only pageblock aligned range to pageblock_pfn_to_page

pageblock_pfn_to_page() is used to check there is valid pfn and all
pages in the pageblock is in a single zone.  If there is a hole in the
pageblock, passing arbitrary position to pageblock_pfn_to_page() could
cause to skip whole pageblock scanning, instead of just skipping the
hole page.  For deterministic behaviour, it's better to always pass
pageblock aligned range to pageblock_pfn_to_page().  It will also help
further optimization on pageblock_pfn_to_page() in the following patch.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Aaron Lu <aaron.lu@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 30 insertions, 11 deletions

diff --git a/mm/compaction.c b/mm/compaction.c
index 56fa3216a6b4..8ce36ebc8d15 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -555,13 +555,17 @@ unsigned long
 isolate_freepages_range(struct compact_control *cc,
                         unsigned long start_pfn, unsigned long end_pfn)
 {
-        unsigned long isolated, pfn, block_end_pfn;
+        unsigned long isolated, pfn, block_start_pfn, block_end_pfn;
         LIST_HEAD(freelist);
 
         pfn = start_pfn;
+        block_start_pfn = pfn & ~(pageblock_nr_pages - 1);
+        if (block_start_pfn < cc->zone->zone_start_pfn)
+                block_start_pfn = cc->zone->zone_start_pfn;
         block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
 
         for (; pfn < end_pfn; pfn += isolated,
+                                block_start_pfn = block_end_pfn,
                                 block_end_pfn += pageblock_nr_pages) {
                 /* Protect pfn from changing by isolate_freepages_block */
                 unsigned long isolate_start_pfn = pfn;
@@ -574,11 +578,13 @@ isolate_freepages_range(struct compact_control *cc,
                  * scanning range to right one.
                  */
                 if (pfn >= block_end_pfn) {
+                        block_start_pfn = pfn & ~(pageblock_nr_pages - 1);
                         block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
                         block_end_pfn = min(block_end_pfn, end_pfn);
                 }
 
-                if (!pageblock_pfn_to_page(pfn, block_end_pfn, cc->zone))
+                if (!pageblock_pfn_to_page(block_start_pfn,
+                                        block_end_pfn, cc->zone))
                         break;
 
                 isolated = isolate_freepages_block(cc, &isolate_start_pfn,
@@ -864,18 +870,23 @@ unsigned long
 isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
                                                         unsigned long end_pfn)
 {
-        unsigned long pfn, block_end_pfn;
+        unsigned long pfn, block_start_pfn, block_end_pfn;
 
         /* Scan block by block. First and last block may be incomplete */
         pfn = start_pfn;
+        block_start_pfn = pfn & ~(pageblock_nr_pages - 1);
+        if (block_start_pfn < cc->zone->zone_start_pfn)
+                block_start_pfn = cc->zone->zone_start_pfn;
         block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
 
         for (; pfn < end_pfn; pfn = block_end_pfn,
+                                block_start_pfn = block_end_pfn,
                                 block_end_pfn += pageblock_nr_pages) {
 
                 block_end_pfn = min(block_end_pfn, end_pfn);
 
-                if (!pageblock_pfn_to_page(pfn, block_end_pfn, cc->zone))
+                if (!pageblock_pfn_to_page(block_start_pfn,
+                                        block_end_pfn, cc->zone))
                         continue;
 
                 pfn = isolate_migratepages_block(cc, pfn, block_end_pfn,
@@ -1104,7 +1115,9 @@ int sysctl_compact_unevictable_allowed __read_mostly = 1;
 static isolate_migrate_t isolate_migratepages(struct zone *zone,
                                         struct compact_control *cc)
 {
-        unsigned long low_pfn, end_pfn;
+        unsigned long block_start_pfn;
+        unsigned long block_end_pfn;
+        unsigned long low_pfn;
         unsigned long isolate_start_pfn;
         struct page *page;
         const isolate_mode_t isolate_mode =
@@ -1116,16 +1129,21 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
          * initialized by compact_zone()
          */
         low_pfn = cc->migrate_pfn;
+        block_start_pfn = cc->migrate_pfn & ~(pageblock_nr_pages - 1);
+        if (block_start_pfn < zone->zone_start_pfn)
+                block_start_pfn = zone->zone_start_pfn;
 
         /* Only scan within a pageblock boundary */
-        end_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages);
+        block_end_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages);
 
         /*
          * Iterate over whole pageblocks until we find the first suitable.
          * Do not cross the free scanner.
          */
-        for (; end_pfn <= cc->free_pfn;
-                        low_pfn = end_pfn, end_pfn += pageblock_nr_pages) {
+        for (; block_end_pfn <= cc->free_pfn;
+                        low_pfn = block_end_pfn,
+                        block_start_pfn = block_end_pfn,
+                        block_end_pfn += pageblock_nr_pages) {
 
                 /*
                  * This can potentially iterate a massively long zone with
@@ -1136,7 +1154,8 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
                                                 && compact_should_abort(cc))
                         break;
 
-                page = pageblock_pfn_to_page(low_pfn, end_pfn, zone);
+                page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
+                                                                        zone);
                 if (!page)
                         continue;
 
@@ -1155,8 +1174,8 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
 
                 /* Perform the isolation */
                 isolate_start_pfn = low_pfn;
-                low_pfn = isolate_migratepages_block(cc, low_pfn, end_pfn,
-                                                                isolate_mode);
+                low_pfn = isolate_migratepages_block(cc, low_pfn,
+                                                block_end_pfn, isolate_mode);
 
                 if (!low_pfn || cc->contended) {
                         acct_isolated(zone, cc);