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, 6 insertions, 6 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 94c6d8988ab3..24de8b65fdbd 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1088,7 +1088,7 @@ int __set_page_dirty_nobuffers(struct page *page)
                 if (!mapping)
                         return 1;
 
-                write_lock_irq(&mapping->tree_lock);
+                spin_lock_irq(&mapping->tree_lock);
                 mapping2 = page_mapping(page);
                 if (mapping2) { /* Race with truncate? */
                         BUG_ON(mapping2 != mapping);
@@ -1102,7 +1102,7 @@ int __set_page_dirty_nobuffers(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);
                 if (mapping->host) {
                         /* !PageAnon && !swapper_space */
                         __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
@@ -1258,7 +1258,7 @@ int test_clear_page_writeback(struct page *page)
                 struct backing_dev_info *bdi = mapping->backing_dev_info;
                 unsigned long flags;
 
-                write_lock_irqsave(&mapping->tree_lock, flags);
+                spin_lock_irqsave(&mapping->tree_lock, flags);
                 ret = TestClearPageWriteback(page);
                 if (ret) {
                         radix_tree_tag_clear(&mapping->page_tree,
@@ -1269,7 +1269,7 @@ int test_clear_page_writeback(struct page *page)
                                 __bdi_writeout_inc(bdi);
                         }
                 }
-                write_unlock_irqrestore(&mapping->tree_lock, flags);
+                spin_unlock_irqrestore(&mapping->tree_lock, flags);
         } else {
                 ret = TestClearPageWriteback(page);
         }
@@ -1287,7 +1287,7 @@ int test_set_page_writeback(struct page *page)
                 struct backing_dev_info *bdi = mapping->backing_dev_info;
                 unsigned long flags;
 
-                write_lock_irqsave(&mapping->tree_lock, flags);
+                spin_lock_irqsave(&mapping->tree_lock, flags);
                 ret = TestSetPageWriteback(page);
                 if (!ret) {
                         radix_tree_tag_set(&mapping->page_tree,
@@ -1300,7 +1300,7 @@ int test_set_page_writeback(struct page *page)
                         radix_tree_tag_clear(&mapping->page_tree,
                                                 page_index(page),
                                                 PAGECACHE_TAG_DIRTY);
-                write_unlock_irqrestore(&mapping->tree_lock, flags);
+                spin_unlock_irqrestore(&mapping->tree_lock, flags);
         } else {
                 ret = TestSetPageWriteback(page);
         }