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, 4 insertions, 4 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 0075eac1cd04..8f71761bc4b7 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -399,7 +399,7 @@ static int __remove_mapping(struct address_space *mapping, struct page *page)
         BUG_ON(!PageLocked(page));
         BUG_ON(mapping != page_mapping(page));
 
-        write_lock_irq(&mapping->tree_lock);
+        spin_lock_irq(&mapping->tree_lock);
         /*
          * The non racy check for a busy page.
          *
@@ -436,17 +436,17 @@ static int __remove_mapping(struct address_space *mapping, struct page *page)
         if (PageSwapCache(page)) {
                 swp_entry_t swap = { .val = page_private(page) };
                 __delete_from_swap_cache(page);
-                write_unlock_irq(&mapping->tree_lock);
+                spin_unlock_irq(&mapping->tree_lock);
                 swap_free(swap);
         } else {
                 __remove_from_page_cache(page);
-                write_unlock_irq(&mapping->tree_lock);
+                spin_unlock_irq(&mapping->tree_lock);
         }
 
         return 1;
 
 cannot_free:
-        write_unlock_irq(&mapping->tree_lock);
+        spin_unlock_irq(&mapping->tree_lock);
         return 0;
 }