readahead: introduce PG_readahead

Introduce a new page flag: PG_readahead.

It acts as a look-ahead mark, which tells the page reader: Hey, it's time to
invoke the read-ahead logic.  For the sake of I/O pipelining, don't wait until
it runs out of cached pages!

Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Steven Pratt <slpratt@austin.ibm.com>
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e2a10b957f23..2165be9462c0 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -617,7 +617,7 @@ static int prep_new_page(struct page *page, int order, gfp_t gfp_flags)
         if (PageReserved(page))
                 return 1;
 
-        page->flags &= ~(1 << PG_uptodate | 1 << PG_error |
+        page->flags &= ~(1 << PG_uptodate | 1 << PG_error | 1 << PG_readahead |
                         1 << PG_referenced | 1 << PG_arch_1 |
                         1 << PG_owner_priv_1 | 1 << PG_mappedtodisk);
         set_page_private(page, 0);