mm: fix zone_watermark_ok_safe() accounting of isolated pages

Commit 702d1a6e0766 ("memory-hotplug: fix kswapd looping forever
problem") added an isolated pageblocks counter (nr_pageblock_isolate in
struct zone) and used it to adjust free pages counter in
zone_watermark_ok_safe() to prevent kswapd looping forever problem.

Then later, commit 2139cbe627b8 ("cma: fix counting of isolated pages")
fixed accounting of isolated pages in global free pages counter.  It
made the previous zone_watermark_ok_safe() fix unnecessary and
potentially harmful (cause now isolated pages may be accounted twice
making free pages counter incorrect).

This patch removes the special isolated pageblocks counter altogether
which fixes zone_watermark_ok_safe() free pages check.

Reported-by: Tomasz Stanislawski <t.stanislaws@samsung.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Aaditya Kumar <aaditya.kumar.30@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 4bec5be82cab5fe2f873cd867c84c8ac18993dba..73b64a38b984a985259c468049cff50a6c44fdd3 100644 (file)
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -503,14 +503,6 @@ struct zone {
         * rarely used fields:
         */
        const char              *name;
-#ifdef CONFIG_MEMORY_ISOLATION
-       /*
-        * the number of MIGRATE_ISOLATE *pageblock*.
-        * We need this for free page counting. Look at zone_watermark_ok_safe.
-        * It's protected by zone->lock
-        */
-       int             nr_pageblock_isolate;
-#endif
 } ____cacheline_internodealigned_in_smp;
 
 typedef enum {

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 4ba5e37127fca863af15fe3090f068ac295c0386..bc6cc0e913bd7d18214218b5fe3d7226e42e24d6 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -221,11 +221,6 @@ EXPORT_SYMBOL(nr_online_nodes);
 
 int page_group_by_mobility_disabled __read_mostly;
 
-/*
- * NOTE:
- * Don't use set_pageblock_migratetype(page, MIGRATE_ISOLATE) directly.
- * Instead, use {un}set_pageblock_isolate.
- */
 void set_pageblock_migratetype(struct page *page, int migratetype)
 {
 
@@ -1655,20 +1650,6 @@ static bool __zone_watermark_ok(struct zone *z, int order, unsigned long mark,
        return true;
 }
 
-#ifdef CONFIG_MEMORY_ISOLATION
-static inline unsigned long nr_zone_isolate_freepages(struct zone *zone)
-{
-       if (unlikely(zone->nr_pageblock_isolate))
-               return zone->nr_pageblock_isolate * pageblock_nr_pages;
-       return 0;
-}
-#else
-static inline unsigned long nr_zone_isolate_freepages(struct zone *zone)
-{
-       return 0;
-}
-#endif
-
 bool zone_watermark_ok(struct zone *z, int order, unsigned long mark,
                      int classzone_idx, int alloc_flags)
 {
@@ -1684,14 +1665,6 @@ bool zone_watermark_ok_safe(struct zone *z, int order, unsigned long mark,
        if (z->percpu_drift_mark && free_pages < z->percpu_drift_mark)
                free_pages = zone_page_state_snapshot(z, NR_FREE_PAGES);
 
-       /*
-        * If the zone has MIGRATE_ISOLATE type free pages, we should consider
-        * it.  nr_zone_isolate_freepages is never accurate so kswapd might not
-        * sleep although it could do so.  But this is more desirable for memory
-        * hotplug than sleeping which can cause a livelock in the direct
-        * reclaim path.
-        */
-       free_pages -= nr_zone_isolate_freepages(z);
        return __zone_watermark_ok(z, order, mark, classzone_idx, alloc_flags,
                                                                free_pages);
 }

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 9d2264ea460617b6aef2b59271e61933c15fbffd..383bdbb98b04ca22726fe3d243db2ce789642975 100644 (file)
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -8,28 +8,6 @@
 #include <linux/memory.h>
 #include "internal.h"
 
-/* called while holding zone->lock */
-static void set_pageblock_isolate(struct page *page)
-{
-       if (get_pageblock_migratetype(page) == MIGRATE_ISOLATE)
-               return;
-
-       set_pageblock_migratetype(page, MIGRATE_ISOLATE);
-       page_zone(page)->nr_pageblock_isolate++;
-}
-
-/* called while holding zone->lock */
-static void restore_pageblock_isolate(struct page *page, int migratetype)
-{
-       struct zone *zone = page_zone(page);
-       if (WARN_ON(get_pageblock_migratetype(page) != MIGRATE_ISOLATE))
-               return;
-
-       BUG_ON(zone->nr_pageblock_isolate <= 0);
-       set_pageblock_migratetype(page, migratetype);
-       zone->nr_pageblock_isolate--;
-}
-
 int set_migratetype_isolate(struct page *page, bool skip_hwpoisoned_pages)
 {
        struct zone *zone;
@@ -80,7 +58,7 @@ out:
                unsigned long nr_pages;
                int migratetype = get_pageblock_migratetype(page);
 
-               set_pageblock_isolate(page);
+               set_pageblock_migratetype(page, MIGRATE_ISOLATE);
                nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE);
 
                __mod_zone_freepage_state(zone, -nr_pages, migratetype);
@@ -103,7 +81,7 @@ void unset_migratetype_isolate(struct page *page, unsigned migratetype)
                goto out;
        nr_pages = move_freepages_block(zone, page, migratetype);
        __mod_zone_freepage_state(zone, nr_pages, migratetype);
-       restore_pageblock_isolate(page, migratetype);
+       set_pageblock_migratetype(page, migratetype);
 out:
        spin_unlock_irqrestore(&zone->lock, flags);
 }