[PATCH 06/33] readahead: refactor __do_page_cache_readahead()

Wu Fengguang
2006-05-24T11:29:17Z

[-- Attachment #1: readahead-refactor-__do_page_cache_readahead.patch --]
[-- Type: text/plain, Size: 2546 bytes --]

Add look-ahead support to __do_page_cache_readahead(),
which is needed by the adaptive read-ahead logic.

Signed-off-by: Wu Fengguang <wfg@mail.ustc.edu.cn>
---

mm/readahead.c | 15 +++++++++------
1 files changed, 9 insertions(+), 6 deletions(-)

--- linux-2.6.17-rc4-mm3.orig/mm/readahead.c
+++ linux-2.6.17-rc4-mm3/mm/readahead.c
@@ -266,7 +266,8 @@ out:
*/
static int
__do_page_cache_readahead(struct address_space *mapping, struct file *filp,
- pgoff_t offset, unsigned long nr_to_read)
+ pgoff_t offset, unsigned long nr_to_read,
+ unsigned long lookahead_size)
{
struct inode *inode = mapping->host;
struct page *page;
@@ -279,7 +280,7 @@ __do_page_cache_readahead(struct address
if (isize == 0)
goto out;

- end_index = ((isize - 1) >> PAGE_CACHE_SHIFT);
+ end_index = ((isize - 1) >> PAGE_CACHE_SHIFT);

/*
* Preallocate as many pages as we will need.
@@ -302,6 +303,8 @@ __do_page_cache_readahead(struct address
break;
page->index = page_offset;
list_add(&page->lru, &page_pool);
+ if (page_idx == nr_to_read - lookahead_size)
+ __SetPageReadahead(page);
ret++;
}
read_unlock_irq(&mapping->tree_lock);
@@ -338,7 +341,7 @@ int force_page_cache_readahead(struct ad
if (this_chunk > nr_to_read)
this_chunk = nr_to_read;
err = __do_page_cache_readahead(mapping, filp,
- offset, this_chunk);
+ offset, this_chunk, 0);
if (err < 0) {
ret = err;
break;
@@ -385,7 +388,7 @@ int do_page_cache_readahead(struct addre
if (bdi_read_congested(mapping->backing_dev_info))
return -1;

- return __do_page_cache_readahead(mapping, filp, offset, nr_to_read);
+ return __do_page_cache_readahead(mapping, filp, offset, nr_to_read, 0);
}

/*
@@ -405,7 +408,7 @@ blockable_page_cache_readahead(struct ad
if (!block && bdi_read_congested(mapping->backing_dev_info))
return 0;

- actual = __do_page_cache_readahead(mapping, filp, offset, nr_to_read);
+ actual = __do_page_cache_readahead(mapping, filp, offset, nr_to_read, 0);

return check_ra_success(ra, nr_to_read, actual);
}
@@ -450,7 +453,7 @@ static int make_ahead_window(struct addr
* @req_size: hint: total size of the read which the caller is performing in
* PAGE_CACHE_SIZE units
*
- * page_cache_readahead() is the main function. If performs the adaptive
+ * page_cache_readahead() is the main function. It performs the adaptive
* readahead window size management and submits the readahead I/O.
*
* Note that @filp is purely used for passing on to the ->readpage[s]()

--