[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>

diff --git a/mm/filemap.c b/mm/filemap.c
index 13df01c..af7e2f5 100644 (file)
--- 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 156861f..a07120d 100644 (file)
--- 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);