Cases "no ahead window" and "crossed into ahead window"
can be unified.
Signed-off-by: Oleg Nesterov <[EMAIL PROTECTED]>
--- 2.6.11-rc2/mm/readahead.c~ 2005-01-25 14:28:22.000000000 +0300
+++ 2.6.11-rc2/mm/readahead.c 2005-01-25 15:17:13.000000000 +0300
@@ -483,43 +483,24 @@ page_cache_readahead(struct address_spac
* occurence (ie we have an existing window)
*/
- if (ra->ahead_start == 0) { /* no ahead window yet */
- ra->ahead_size = get_next_ra_size(ra->size, max, min,
- &ra->flags);
- ra->ahead_start = ra->start + ra->size;
- block = ((offset + newsize -1) >= ra->ahead_start);
- if (!blockable_page_cache_readahead(mapping, filp,
- ra->ahead_start, ra->ahead_size, ra, block)) {
- /* A read failure in blocking mode, implies pages are
- * all cached. So we can safely assume we have taken
- * care of all the pages requested in this call. A read
- * failure in non-blocking mode, implies we are reading
- * more pages than requested in this call. So we safely
- * assume we have taken care of all the pages requested
- * in this call.
- *
- * Just reset the ahead window in case we failed due to
- * congestion. The ahead window will any way be closed
- * in case we failed due to exessive page cache hits.
- */
- ra->ahead_start = 0;
- ra->ahead_size = 0;
- goto out;
- }
- }
/*
- * Already have an ahead window, check if we crossed into it.
+ * Check if we crossed into ahead window.
* If so, shift windows and issue a new ahead window.
* Only return the #pages that are in the current window, so that
* we get called back on the first page of the ahead window which
* will allow us to submit more IO.
*/
if ((offset + newsize - 1) >= ra->ahead_start) {
- ra->start = ra->ahead_start;
- ra->size = ra->ahead_size;
- ra->ahead_start = ra->ahead_start + ra->ahead_size;
- ra->ahead_size = get_next_ra_size(ra->ahead_size,
- max, min, &ra->flags);
+ /* Check if we already have an ahead window */
+ if (ra->ahead_start != 0) {
+ ra->start = ra->ahead_start;
+ 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;
+
block = ((offset + newsize - 1) >= ra->ahead_start);
if (!blockable_page_cache_readahead(mapping, filp,
ra->ahead_start, ra->ahead_size, ra, block)) {
-
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