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/fs/buffer.c b/fs/buffer.c
index d48caee12e2a..109b261192d9 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -706,7 +706,7 @@ static int __set_page_dirty(struct page *page,
         if (TestSetPageDirty(page))
                 return 0;
 
-        write_lock_irq(&mapping->tree_lock);
+        spin_lock_irq(&mapping->tree_lock);
         if (page->mapping) {    /* Race with truncate? */
                 WARN_ON_ONCE(warn && !PageUptodate(page));
 
@@ -719,7 +719,7 @@ static int __set_page_dirty(struct page *page,
                 radix_tree_tag_set(&mapping->page_tree,
                                 page_index(page), PAGECACHE_TAG_DIRTY);
         }
-        write_unlock_irq(&mapping->tree_lock);
+        spin_unlock_irq(&mapping->tree_lock);
         __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
 
         return 1;