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Commit f615bfca authored by Fengguang Wu's avatar Fengguang Wu Committed by Linus Torvalds
Browse files

readahead: MIN_RA_PAGES/MAX_RA_PAGES macros 



Define two convenient macros for read-ahead:
	- MAX_RA_PAGES: rounded down counterpart of VM_MAX_READAHEAD
	- MIN_RA_PAGES: rounded _up_ counterpart of VM_MIN_READAHEAD

Note that the rounded up MIN_RA_PAGES will work flawlessly with _large_
page sizes like 64k.

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>
Cc: <stable@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 46fc3e7b

mm/readahead.c

+10 −2
Original line number Original line Diff line number Diff line
@@ -21,8 +21,16 @@ void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page) 
}

}

EXPORT_SYMBOL(default_unplug_io_fn);

EXPORT_SYMBOL(default_unplug_io_fn);





/*

 * Convienent macros for min/max read-ahead pages.

 * Note that MAX_RA_PAGES is rounded down, while MIN_RA_PAGES is rounded up.

 * The latter is necessary for systems with large page size(i.e. 64k).

 */

#define MAX_RA_PAGES	(VM_MAX_READAHEAD*1024 / PAGE_CACHE_SIZE)

#define MIN_RA_PAGES	DIV_ROUND_UP(VM_MIN_READAHEAD*1024, PAGE_CACHE_SIZE)



struct backing_dev_info default_backing_dev_info = {

struct backing_dev_info default_backing_dev_info = {

	.ra_pages	= (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE,

	.ra_pages	= MAX_RA_PAGES,

	.state		= 0,

	.state		= 0,

	.capabilities	= BDI_CAP_MAP_COPY,

	.capabilities	= BDI_CAP_MAP_COPY,

	.unplug_io_fn	= default_unplug_io_fn,

	.unplug_io_fn	= default_unplug_io_fn,
@@ -51,7 +59,7 @@ static inline unsigned long get_max_readahead(struct file_ra_state *ra) 




static inline unsigned long get_min_readahead(struct file_ra_state *ra)

static inline unsigned long get_min_readahead(struct file_ra_state *ra)

{

{

	return (VM_MIN_READAHEAD * 1024) / PAGE_CACHE_SIZE;

	return MIN_RA_PAGES;

}

}





static inline void reset_ahead_window(struct file_ra_state *ra)

static inline void reset_ahead_window(struct file_ra_state *ra)