mm: spinlock tree_lock

mapping->tree_lock has no read lockers.  convert the lock from an rwlock
to a spinlock.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 2f33edb8bee9..af283933c14e 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -369,13 +369,13 @@ int remove_exclusive_swap_page(struct page *page)
         retval = 0;
         if (p->swap_map[swp_offset(entry)] == 1) {
                 /* Recheck the page count with the swapcache lock held.. */
-                write_lock_irq(&swapper_space.tree_lock);
+                spin_lock_irq(&swapper_space.tree_lock);
                 if ((page_count(page) == 2) && !PageWriteback(page)) {
                         __delete_from_swap_cache(page);
                         SetPageDirty(page);
                         retval = 1;
                 }
-                write_unlock_irq(&swapper_space.tree_lock);
+                spin_unlock_irq(&swapper_space.tree_lock);
         }
         spin_unlock(&swap_lock);