[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>

diff --git a/mm/filemap.c b/mm/filemap.c
index 6e1d08a..4ef24a3 100644 (file)
--- 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;