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 <[email protected]>
---
include/linux/page-flags.h | 5 +++++
mm/page_alloc.c | 2 +-
2 files changed, 6 insertions(+), 1 deletion(-)
--- linux-2.6.22-rc1-mm1.orig/include/linux/page-flags.h
+++ linux-2.6.22-rc1-mm1/include/linux/page-flags.h
@@ -92,6 +92,7 @@
#define PG_lazyfree 20 /* MADV_FREE potential throwaway */
#define PG_booked 21 /* Has blocks reserved on-disk */
+#define PG_readahead 22 /* Reminder to do async read-ahead */
/* PG_owner_priv_1 users should have descriptive aliases */
#define PG_checked PG_owner_priv_1 /* Used by some filesystems */
@@ -206,6 +207,10 @@ static inline void SetPageUptodate(struc
#define SetPageBooked(page) set_bit(PG_booked, &(page)->flags)
#define ClearPageBooked(page) clear_bit(PG_booked, &(page)->flags)
+#define PageReadahead(page) test_bit(PG_readahead, &(page)->flags)
+#define SetPageReadahead(page) set_bit(PG_readahead, &(page)->flags)
+#define ClearPageReadahead(page) clear_bit(PG_readahead, &(page)->flags)
+
#define PageReclaim(page) test_bit(PG_reclaim, &(page)->flags)
#define SetPageReclaim(page) set_bit(PG_reclaim, &(page)->flags)
#define ClearPageReclaim(page) clear_bit(PG_reclaim, &(page)->flags)
--- linux-2.6.22-rc1-mm1.orig/mm/page_alloc.c
+++ linux-2.6.22-rc1-mm1/mm/page_alloc.c
@@ -659,7 +659,7 @@ static int prep_new_page(struct page *pa
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);
--
-
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