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, 3 insertions, 3 deletions

diff --git a/mm/truncate.c b/mm/truncate.c
index b8961cb63414..e68443d74567 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -349,18 +349,18 @@ invalidate_complete_page2(struct address_space *mapping, struct page *page)
         if (PagePrivate(page) && !try_to_release_page(page, GFP_KERNEL))
                 return 0;
 
-        write_lock_irq(&mapping->tree_lock);
+        spin_lock_irq(&mapping->tree_lock);
         if (PageDirty(page))
                 goto failed;
 
         BUG_ON(PagePrivate(page));
         __remove_from_page_cache(page);
-        write_unlock_irq(&mapping->tree_lock);
+        spin_unlock_irq(&mapping->tree_lock);
         ClearPageUptodate(page);
         page_cache_release(page);       /* pagecache ref */
         return 1;
 failed:
-        write_unlock_irq(&mapping->tree_lock);
+        spin_unlock_irq(&mapping->tree_lock);
         return 0;
 }