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/swap_state.c b/mm/swap_state.c
index 3e3381d6c7ee..2c217e33d497 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -39,7 +39,7 @@ static struct backing_dev_info swap_backing_dev_info = {
 
 struct address_space swapper_space = {
         .page_tree      = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN),
-        .tree_lock      = __RW_LOCK_UNLOCKED(swapper_space.tree_lock),
+        .tree_lock      = __SPIN_LOCK_UNLOCKED(swapper_space.tree_lock),
         .a_ops          = &swap_aops,
         .i_mmap_nonlinear = LIST_HEAD_INIT(swapper_space.i_mmap_nonlinear),
         .backing_dev_info = &swap_backing_dev_info,
@@ -80,7 +80,7 @@ int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
                 SetPageSwapCache(page);
                 set_page_private(page, entry.val);
 
-                write_lock_irq(&swapper_space.tree_lock);
+                spin_lock_irq(&swapper_space.tree_lock);
                 error = radix_tree_insert(&swapper_space.page_tree,
                                                 entry.val, page);
                 if (likely(!error)) {
@@ -88,7 +88,7 @@ int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
                         __inc_zone_page_state(page, NR_FILE_PAGES);
                         INC_CACHE_INFO(add_total);
                 }
-                write_unlock_irq(&swapper_space.tree_lock);
+                spin_unlock_irq(&swapper_space.tree_lock);
                 radix_tree_preload_end();
 
                 if (unlikely(error)) {
@@ -182,9 +182,9 @@ void delete_from_swap_cache(struct page *page)
 
         entry.val = page_private(page);
 
-        write_lock_irq(&swapper_space.tree_lock);
+        spin_lock_irq(&swapper_space.tree_lock);
         __delete_from_swap_cache(page);
-        write_unlock_irq(&swapper_space.tree_lock);
+        spin_unlock_irq(&swapper_space.tree_lock);
 
         swap_free(entry);
         page_cache_release(page);