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Subject[PATCH 4.4 26/87] mm/compaction: pass only pageblock aligned range to pageblock_pfn_to_page
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Joonsoo Kim <iamjoonsoo.kim@lge.com>

commit e1409c325fdc1fef7b3d8025c51892355f065d15 upstream.

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>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
mm/compaction.c | 41 ++++++++++++++++++++++++++++++-----------
1 file changed, 30 insertions(+), 11 deletions(-)

--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -553,13 +553,17 @@ 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;
@@ -572,11 +576,13 @@ isolate_freepages_range(struct compact_c
* 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,
@@ -862,18 +868,23 @@ 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,
@@ -1091,7 +1102,9 @@ int sysctl_compact_unevictable_allowed _
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 =
@@ -1103,16 +1116,21 @@ static isolate_migrate_t isolate_migrate
* 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
@@ -1123,7 +1141,8 @@ static isolate_migrate_t isolate_migrate
&& 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;

@@ -1142,8 +1161,8 @@ static isolate_migrate_t isolate_migrate

/* 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);

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