[PATCH] find_lock_page(): call __lock_page() directly.

As find_lock_page() already checks with TestSetPageLocked() that page is
locked, there is no need to call lock_page() that will try-lock page again
(chances of page being unlocked in between are small).  Call __lock_page()
directly, this saves one atomic operation.

Also, mark truncate-while-slept path as unlikely while we are here.

(akpm: ug.  But this is actually a common path for normal old read()s against
a page which is under readahead I/O so ho-hum.)

Signed-off-by: Nikita Danilov <danilov@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 6e1d08a2b8b9..4ef24a397684 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -555,11 +555,12 @@ repeat:
                 page_cache_get(page);
                 if (TestSetPageLocked(page)) {
                         read_unlock_irq(&mapping->tree_lock);
-                        lock_page(page);
+                        __lock_page(page);
                         read_lock_irq(&mapping->tree_lock);
 
                         /* Has the page been truncated while we slept? */
-                        if (page->mapping != mapping || page->index != offset) {
+                        if (unlikely(page->mapping != mapping ||
+                                     page->index != offset)) {
                                 unlock_page(page);
                                 page_cache_release(page);
                                 goto repeat;