From: Oleg Nesterov <oleg@tv-sign.ru>
Currently page_cache_readahead() treats ra->size == 0 (first read) and
ra->size == -1 (ra_off was called) separately, but does exactly the same in
both cases.
With this patch we may assume that the reading starts in 'ra_off()' state,
so we don't need to consider the first read as a special case.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/mm/readahead.c | 10 ++++------
1 files changed, 4 insertions(+), 6 deletions(-)
diff -puN mm/readahead.c~readahead-simplify-ra-size-testing mm/readahead.c
--- 25/mm/readahead.c~readahead-simplify-ra-size-testing 2005-03-02 17:57:50.000000000 -0800
+++ 25-akpm/mm/readahead.c 2005-03-02 17:57:52.000000000 -0800
@@ -55,7 +55,7 @@ static inline void ra_off(struct file_ra
{
ra->start = 0;
ra->flags = 0;
- ra->size = -1;
+ ra->size = 0;
ra->ahead_start = 0;
ra->ahead_size = 0;
return;
@@ -452,7 +452,7 @@ page_cache_readahead(struct address_spac
* perturbing the readahead window expansion logic.
* If size is zero, there is no read ahead window so we need one
*/
- if (offset == ra->prev_page && req_size == 1 && ra->size != 0)
+ if (offset == ra->prev_page && req_size == 1)
goto out;
ra->prev_page = offset;
@@ -471,9 +471,7 @@ page_cache_readahead(struct address_spac
* at start of file, and grow the window fast. Or detect first
* sequential access
*/
- if ((ra->size == 0 && offset == 0) /* first io and start of file */
- || (ra->size == -1 && sequential)) {
- /* First sequential */
+ if (sequential && ra->size == 0) {
ra->size = get_init_ra_size(newsize, max);
ra->start = offset;
if (!blockable_page_cache_readahead(mapping, filp, offset,
@@ -499,7 +497,7 @@ page_cache_readahead(struct address_spac
* partial page reads and first access were handled above,
* so this must be the next page otherwise it is random
*/
- if (!sequential || (ra->size == 0)) {
+ if (!sequential) {
ra_off(ra);
blockable_page_cache_readahead(mapping, filp, offset,
newsize, ra, 1);
_