Wu Fengguang wrote:
Define some common used macros for the read-ahead logics.
Signed-off-by: Wu Fengguang <[email protected]>
---
mm/readahead.c | 14 ++++++++++++--
1 files changed, 12 insertions(+), 2 deletions(-)
--- linux-2.6.17-rc4-mm3.orig/mm/readahead.c
+++ linux-2.6.17-rc4-mm3/mm/readahead.c
@@ -5,6 +5,8 @@
*
* 09Apr2002 [email protected]
* Initial version.
+ * 21May2006 Wu Fengguang <[email protected]>
+ * Adaptive read-ahead framework.
*/
#include <linux/kernel.h>
@@ -14,6 +16,14 @@
#include <linux/blkdev.h>
#include <linux/backing-dev.h>
#include <linux/pagevec.h>
+#include <linux/writeback.h>
+#include <linux/nfsd/const.h>
How come you're adding these includes?
+
+#define PAGES_BYTE(size) (((size) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT)
+#define PAGES_KB(size) PAGES_BYTE((size)*1024)
Don't really like the names. Don't think they do anything for clarity, but
if you can come up with something better for PAGES_BYTE I might change my
mind ;) (just forget about PAGES_KB - people know what *1024 means)
Also: the replacements are wrong: if you've defined VM_MAX_READAHEAD to be
4095 bytes, you don't want the _actual_ readahead to be 4096 bytes, do you?
It is saying nothing about minimum, so presumably 0 is the correct choice.
+
+#define next_page(pg) (list_entry((pg)->lru.prev, struct page, lru))
+#define prev_page(pg) (list_entry((pg)->lru.next, struct page, lru))
Again, it is probably easier just to use the expanded version. Then the
reader can immediately say: ah, the next page on the LRU list (rather
than, maybe, the next page in the pagecache).
void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
{
@@ -21,7 +31,7 @@ void default_unplug_io_fn(struct backing
EXPORT_SYMBOL(default_unplug_io_fn);
struct backing_dev_info default_backing_dev_info = {
- .ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE,
+ .ra_pages = PAGES_KB(VM_MAX_READAHEAD),
.state = 0,
.capabilities = BDI_CAP_MAP_COPY,
.unplug_io_fn = default_unplug_io_fn,
@@ -50,7 +60,7 @@ static inline unsigned long get_max_read
static inline unsigned long get_min_readahead(struct file_ra_state *ra)
{
- return (VM_MIN_READAHEAD * 1024) / PAGE_CACHE_SIZE;
+ return PAGES_KB(VM_MIN_READAHEAD);
}
static inline void reset_ahead_window(struct file_ra_state *ra)
--
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