[PATCH] grab swap token reordered

Make sure the contention for the token happens _before_ any read-in and
kicks the swap-token algo only when the VM is under pressure.

Signed-off-by: Ashwin Chaugule <ashwin.chaugule@celunite.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 1 insertions, 2 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 13df01c50479..af7e2f5caea9 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1445,7 +1445,6 @@ no_cached_page:
          * effect.
          */
         error = page_cache_read(file, pgoff);
-        grab_swap_token();
 
         /*
          * The page we want has now been added to the page cache.
diff --git a/mm/memory.c b/mm/memory.c
index 156861fcac43..a07120da868b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1991,6 +1991,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
         delayacct_set_flag(DELAYACCT_PF_SWAPIN);
         page = lookup_swap_cache(entry);
         if (!page) {
+                grab_swap_token(); /* Contend for token _before_ read-in */
                 swapin_readahead(entry, address, vma);
                 page = read_swap_cache_async(entry, vma, address);
                 if (!page) {
@@ -2008,7 +2009,6 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
                 /* Had to read the page from swap area: Major fault */
                 ret = VM_FAULT_MAJOR;
                 count_vm_event(PGMAJFAULT);
-                grab_swap_token();
         }
 
         delayacct_clear_flag(DELAYACCT_PF_SWAPIN);