mm: take pagevecs off reclaim stack

Replace pagevecs in putback_lru_pages() and move_active_pages_to_lru()
by lists of pages_to_free: then apply Konstantin Khlebnikov's
free_hot_cold_page_list() to them instead of pagevec_release().

Which simplifies the flow (no need to drop and retake lock whenever
pagevec fills up) and reduces stale addresses in stack backtraces
(which often showed through the pagevecs); but more importantly,
removes another 120 bytes from the deepest stacks in page reclaim.
Although I've not recently seen an actual stack overflow here with
a vanilla kernel, move_active_pages_to_lru() has often featured in
deep backtraces.

However, free_hot_cold_page_list() does not handle compound pages
(nor need it: a Transparent HugePage would have been split by the
time it reaches the call in shrink_page_list()), but it is possible
for putback_lru_pages() or move_active_pages_to_lru() to be left
holding the last reference on a THP, so must exclude the unlikely
compound case before putting on pages_to_free.

Remove pagevec_strip(), its work now done in move_active_pages_to_lru().
The pagevec in scan_mapping_unevictable_pages() remains in mm/vmscan.c,
but that is never on the reclaim path, and cannot be replaced by a list.

Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 40 insertions, 37 deletions

diff --git a/mm/swap.c b/mm/swap.c
index db6defaf2e55..79c22a649a3e 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -23,7 +23,6 @@
 #include <linux/init.h>
 #include <linux/export.h>
 #include <linux/mm_inline.h>
-#include <linux/buffer_head.h>  /* for try_to_release_page() */
 #include <linux/percpu_counter.h>
 #include <linux/percpu.h>
 #include <linux/cpu.h>
@@ -730,24 +729,6 @@ void ____pagevec_lru_add(struct pagevec *pvec, enum lru_list lru)
 
 EXPORT_SYMBOL(____pagevec_lru_add);
 
-/*
- * Try to drop buffers from the pages in a pagevec
- */
-void pagevec_strip(struct pagevec *pvec)
-{
-        int i;
-
-        for (i = 0; i < pagevec_count(pvec); i++) {
-                struct page *page = pvec->pages[i];
-
-                if (page_has_private(page) && trylock_page(page)) {
-                        if (page_has_private(page))
-                                try_to_release_page(page, 0);
-                        unlock_page(page);
-                }
-        }
-}
-
 /**
  * pagevec_lookup - gang pagecache lookup
  * @pvec:       Where the resulting pages are placed
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 25f90383b391..7724fb8e7498 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1398,12 +1398,10 @@ putback_lru_pages(struct mem_cgroup_zone *mz, struct scan_control *sc,
                   struct list_head *page_list)
 {
         struct page *page;
-        struct pagevec pvec;
+        LIST_HEAD(pages_to_free);
         struct zone *zone = mz->zone;
         struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
 
-        pagevec_init(&pvec, 1);
-
         /*
          * Put back any unfreeable pages.
          */
@@ -1427,17 +1425,24 @@ putback_lru_pages(struct mem_cgroup_zone *mz, struct scan_control *sc,
                         int numpages = hpage_nr_pages(page);
                         reclaim_stat->recent_rotated[file] += numpages;
                 }
-                if (!pagevec_add(&pvec, page)) {
-                        spin_unlock_irq(&zone->lru_lock);
-                        __pagevec_release(&pvec);
-                        spin_lock_irq(&zone->lru_lock);
+                if (put_page_testzero(page)) {
+                        __ClearPageLRU(page);
+                        __ClearPageActive(page);
+                        del_page_from_lru_list(zone, page, lru);
+
+                        if (unlikely(PageCompound(page))) {
+                                spin_unlock_irq(&zone->lru_lock);
+                                (*get_compound_page_dtor(page))(page);
+                                spin_lock_irq(&zone->lru_lock);
+                        } else
+                                list_add(&page->lru, &pages_to_free);
                 }
         }
         __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
         __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
 
         spin_unlock_irq(&zone->lru_lock);
-        pagevec_release(&pvec);
+        free_hot_cold_page_list(&pages_to_free, 1);
 }
 
 static noinline_for_stack void
@@ -1647,13 +1652,23 @@ shrink_inactive_list(unsigned long nr_to_scan, struct mem_cgroup_zone *mz,
 
 static void move_active_pages_to_lru(struct zone *zone,
                                      struct list_head *list,
+                                     struct list_head *pages_to_free,
                                      enum lru_list lru)
 {
         unsigned long pgmoved = 0;
-        struct pagevec pvec;
         struct page *page;
 
-        pagevec_init(&pvec, 1);
+        if (buffer_heads_over_limit) {
+                spin_unlock_irq(&zone->lru_lock);
+                list_for_each_entry(page, list, lru) {
+                        if (page_has_private(page) && trylock_page(page)) {
+                                if (page_has_private(page))
+                                        try_to_release_page(page, 0);
+                                unlock_page(page);
+                        }
+                }
+                spin_lock_irq(&zone->lru_lock);
+        }
 
         while (!list_empty(list)) {
                 struct lruvec *lruvec;
@@ -1667,12 +1682,17 @@ static void move_active_pages_to_lru(struct zone *zone,
                 list_move(&page->lru, &lruvec->lists[lru]);
                 pgmoved += hpage_nr_pages(page);
 
-                if (!pagevec_add(&pvec, page) || list_empty(list)) {
-                        spin_unlock_irq(&zone->lru_lock);
-                        if (buffer_heads_over_limit)
-                                pagevec_strip(&pvec);
-                        __pagevec_release(&pvec);
-                        spin_lock_irq(&zone->lru_lock);
+                if (put_page_testzero(page)) {
+                        __ClearPageLRU(page);
+                        __ClearPageActive(page);
+                        del_page_from_lru_list(zone, page, lru);
+
+                        if (unlikely(PageCompound(page))) {
+                                spin_unlock_irq(&zone->lru_lock);
+                                (*get_compound_page_dtor(page))(page);
+                                spin_lock_irq(&zone->lru_lock);
+                        } else
+                                list_add(&page->lru, pages_to_free);
                 }
         }
         __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
@@ -1766,12 +1786,14 @@ static void shrink_active_list(unsigned long nr_pages,
          */
         reclaim_stat->recent_rotated[file] += nr_rotated;
 
-        move_active_pages_to_lru(zone, &l_active,
+        move_active_pages_to_lru(zone, &l_active, &l_hold,
                                                 LRU_ACTIVE + file * LRU_FILE);
-        move_active_pages_to_lru(zone, &l_inactive,
+        move_active_pages_to_lru(zone, &l_inactive, &l_hold,
                                                 LRU_BASE   + file * LRU_FILE);
         __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
         spin_unlock_irq(&zone->lru_lock);
+
+        free_hot_cold_page_list(&l_hold, 1);
 }
 
 #ifdef CONFIG_SWAP