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, 5 insertions, 5 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index feb8448d8618..2ed8b0389c51 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -109,7 +109,7 @@
 /*
  * Remove a page from the page cache and free it. Caller has to make
  * sure the page is locked and that nobody else uses it - or that usage
- * is safe.  The caller must hold a write_lock on the mapping's tree_lock.
+ * is safe.  The caller must hold the mapping's tree_lock.
  */
 void __remove_from_page_cache(struct page *page)
 {
@@ -141,9 +141,9 @@ void remove_from_page_cache(struct page *page)
 
         BUG_ON(!PageLocked(page));
 
-        write_lock_irq(&mapping->tree_lock);
+        spin_lock_irq(&mapping->tree_lock);
         __remove_from_page_cache(page);
-        write_unlock_irq(&mapping->tree_lock);
+        spin_unlock_irq(&mapping->tree_lock);
 }
 
 static int sync_page(void *word)
@@ -469,7 +469,7 @@ int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
                 page->mapping = mapping;
                 page->index = offset;
 
-                write_lock_irq(&mapping->tree_lock);
+                spin_lock_irq(&mapping->tree_lock);
                 error = radix_tree_insert(&mapping->page_tree, offset, page);
                 if (likely(!error)) {
                         mapping->nrpages++;
@@ -480,7 +480,7 @@ int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
                         page_cache_release(page);
                 }
 
-                write_unlock_irq(&mapping->tree_lock);
+                spin_unlock_irq(&mapping->tree_lock);
                 radix_tree_preload_end();
         } else
                 mem_cgroup_uncharge_cache_page(page);