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Subject[PATCH 3/4] cleanup ahead window calculation
This patch moves some code into the get_next_ra_size()
and renames it into 'set_next_ahead_window'.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>

--- 2.6.11-rc2/mm/readahead.c~ 2005-01-25 15:17:13.000000000 +0300
+++ 2.6.11-rc2/mm/readahead.c 2005-01-25 16:51:50.000000000 +0300
@@ -85,20 +85,23 @@ static unsigned long get_init_ra_size(un
* not for each call to readahead. If a cache miss occured, reduce next I/O
* size, else increase depending on how close to max we are.
*/
-static unsigned long get_next_ra_size(unsigned long cur, unsigned long max,
- unsigned long min, unsigned long * flags)
+static void set_next_ahead_window(struct file_ra_state *ra,
+ unsigned long max, unsigned long min)
{
unsigned long newsize;
+ unsigned long cur = ra->size;

- if (*flags & RA_FLAG_MISS) {
+ ra->ahead_start = ra->start + cur;
+
+ if (ra->flags & RA_FLAG_MISS) {
+ ra->flags &= ~RA_FLAG_MISS;
newsize = max((cur - 2), min);
- *flags &= ~RA_FLAG_MISS;
- } else if (cur < max / 16) {
+ } else if (cur < max / 16)
newsize = 4 * cur;
- } else {
+ else
newsize = 2 * cur;
- }
- return min(newsize, max);
+
+ ra->ahead_size = min(newsize, max);
}

#define list_to_page(head) (list_entry((head)->prev, struct page, lru))
@@ -457,9 +460,7 @@ page_cache_readahead(struct address_spac
* immediately.
*/
if (req_size >= max) {
- ra->ahead_size = get_next_ra_size(ra->size, max, min,
- &ra->flags);
- ra->ahead_start = ra->start + ra->size;
+ set_next_ahead_window(ra, max, min);
blockable_page_cache_readahead(mapping, filp,
ra->ahead_start, ra->ahead_size, ra, 1);
}
@@ -497,9 +498,7 @@ page_cache_readahead(struct address_spac
ra->size = ra->ahead_size;
}

- ra->ahead_size = get_next_ra_size(ra->size, max, min,
- &ra->flags);
- ra->ahead_start = ra->start + ra->size;
+ set_next_ahead_window(ra, max, min);

block = ((offset + newsize - 1) >= ra->ahead_start);
if (!blockable_page_cache_readahead(mapping, filp,
-
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