vmscan: set up pagevec as late as possible in shrink_page_list()

shrink_page_list() sets up a pagevec to release pages as according as they
are free.  It uses significant amounts of stack on the pagevec.  This
patch adds pages to be freed via pagevec to a linked list which is then
freed en-masse at the end.  This avoids using stack in the main path that
potentially calls writepage().

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 12b6921..512f463 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -622,6 +622,24 @@ static enum page_references page_check_references(struct page *page,
        return PAGEREF_RECLAIM;
 }
 
+static noinline_for_stack void free_page_list(struct list_head *free_pages)
+{
+       struct pagevec freed_pvec;
+       struct page *page, *tmp;
+
+       pagevec_init(&freed_pvec, 1);
+
+       list_for_each_entry_safe(page, tmp, free_pages, lru) {
+               list_del(&page->lru);
+               if (!pagevec_add(&freed_pvec, page)) {
+                       __pagevec_free(&freed_pvec);
+                       pagevec_reinit(&freed_pvec);
+               }
+       }
+
+       pagevec_free(&freed_pvec);
+}
+
 /*
  * shrink_page_list() returns the number of reclaimed pages
  */
@@ -630,13 +648,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                                        enum pageout_io sync_writeback)
 {
        LIST_HEAD(ret_pages);
-       struct pagevec freed_pvec;
+       LIST_HEAD(free_pages);
        int pgactivate = 0;
        unsigned long nr_reclaimed = 0;
 
        cond_resched();
 
-       pagevec_init(&freed_pvec, 1);
        while (!list_empty(page_list)) {
                enum page_references references;
                struct address_space *mapping;
@@ -811,10 +828,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                __clear_page_locked(page);
 free_it:
                nr_reclaimed++;
-               if (!pagevec_add(&freed_pvec, page)) {
-                       __pagevec_free(&freed_pvec);
-                       pagevec_reinit(&freed_pvec);
-               }
+
+               /*
+                * Is there need to periodically free_page_list? It would
+                * appear not as the counts should be low
+                */
+               list_add(&page->lru, &free_pages);
                continue;
 
 cull_mlocked:
@@ -837,9 +856,10 @@ keep:
                list_add(&page->lru, &ret_pages);
                VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
        }
+
+       free_page_list(&free_pages);
+
        list_splice(&ret_pages, page_list);
-       if (pagevec_count(&freed_pvec))
-               __pagevec_free(&freed_pvec);
        count_vm_events(PGACTIVATE, pgactivate);
        return nr_reclaimed;
 }