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Commit d77c2d7c authored by Fengguang Wu's avatar Fengguang Wu Committed by Linus Torvalds
Browse files

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: default avatarFengguang 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2ba2d003

include/linux/page-flags.h

+5 −0
Original line number Diff line number Diff line
@@ -83,6 +83,7 @@ 
#define PG_private		11	/* If pagecache, has fs-private data */



#define PG_writeback		12	/* Page is under writeback */

#define PG_readahead		13	/* Reminder to do async read-ahead */

#define PG_compound		14	/* Part of a compound page */

#define PG_swapcache		15	/* Swap page: swp_entry_t in private */
@@ -226,6 +227,10 @@ static inline void SetPageUptodate(struct page *page) 
#define SetPageMappedToDisk(page) set_bit(PG_mappedtodisk, &(page)->flags)

#define ClearPageMappedToDisk(page) clear_bit(PG_mappedtodisk, &(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)

mm/page_alloc.c

+1 −1
Original line number Diff line number Diff line
@@ -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);