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>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e2a10b9..2165be9 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -617,7 +617,7 @@
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);