On Tue 10-04-07 19:27:22, Andrew Morton wrote:
> And shouldn't offset be called prev_offset? Or should prev_page be called
> page? Or index? Or prev_index? Or Marmaduke? The naming is all a mess.
>
> Wanna take a look at all of this, please?
OK, attached is a patch which changes prev_page to prev_index and offset
to prev_offset. It's still a bit misleading that in mm/filemap.c, variables
with page-numbers are called <something>_index while in mm/readahead.c they
are often called just offset... But let's leave it for next time.
Honza
--
Jan Kara <[email protected]>
SuSE CR Labs
Rename file_ra_state.prev_page to prev_index and file_ra_state.offset to
prev_offset. Also update of prev_index in do_generic_mapping_read() is now
moved close to the update of prev_offset.
Signed-off-by: Jan Kara <[email protected]>
diff -rupX /home/jack/.kerndiffexclude linux-2.6.21-rc6-1-readahead/include/linux/fs.h linux-2.6.21-rc6-2-readahead-tidy/include/linux/fs.h
--- linux-2.6.21-rc6-1-readahead/include/linux/fs.h 2007-04-10 17:14:42.000000000 +0200
+++ linux-2.6.21-rc6-2-readahead-tidy/include/linux/fs.h 2007-04-12 17:01:08.000000000 +0200
@@ -696,13 +696,13 @@ struct file_ra_state {
unsigned long size;
unsigned long flags; /* ra flags RA_FLAG_xxx*/
unsigned long cache_hit; /* cache hit count*/
- unsigned long prev_page; /* Cache last read() position */
+ unsigned long prev_index; /* Cache last read() position */
unsigned long ahead_start; /* Ahead window */
unsigned long ahead_size;
unsigned long ra_pages; /* Maximum readahead window */
unsigned long mmap_hit; /* Cache hit stat for mmap accesses */
unsigned long mmap_miss; /* Cache miss stat for mmap accesses */
- unsigned int offset; /* Offset where last read() ended in a page */
+ unsigned int prev_offset; /* Offset where last read() ended in a page */
};
#define RA_FLAG_MISS 0x01 /* a cache miss occured against this file */
#define RA_FLAG_INCACHE 0x02 /* file is already in cache */
diff -rupX /home/jack/.kerndiffexclude linux-2.6.21-rc6-1-readahead/mm/filemap.c linux-2.6.21-rc6-2-readahead-tidy/mm/filemap.c
--- linux-2.6.21-rc6-1-readahead/mm/filemap.c 2007-04-10 17:18:10.000000000 +0200
+++ linux-2.6.21-rc6-2-readahead-tidy/mm/filemap.c 2007-04-12 16:19:25.000000000 +0200
@@ -877,8 +877,8 @@ void do_generic_mapping_read(struct addr
cached_page = NULL;
index = *ppos >> PAGE_CACHE_SHIFT;
next_index = index;
- prev_index = ra.prev_page;
- prev_offset = ra.offset;
+ prev_index = ra.prev_index;
+ prev_offset = ra.prev_offset;
last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
offset = *ppos & ~PAGE_CACHE_MASK;
@@ -931,7 +931,6 @@ page_ok:
*/
if (prev_index != index || offset != prev_offset)
mark_page_accessed(page);
- prev_index = index;
/*
* Ok, we have the page, and it's up-to-date, so
@@ -947,7 +946,8 @@ page_ok:
offset += ret;
index += offset >> PAGE_CACHE_SHIFT;
offset &= ~PAGE_CACHE_MASK;
- prev_offset = ra.offset = offset;
+ prev_index = index;
+ prev_offset = ra.prev_offset = offset;
page_cache_release(page);
if (ret == nr && desc->count)
diff -rupX /home/jack/.kerndiffexclude linux-2.6.21-rc6-1-readahead/mm/readahead.c linux-2.6.21-rc6-2-readahead-tidy/mm/readahead.c
--- linux-2.6.21-rc6-1-readahead/mm/readahead.c 2007-04-10 17:14:42.000000000 +0200
+++ linux-2.6.21-rc6-2-readahead-tidy/mm/readahead.c 2007-04-12 17:03:18.000000000 +0200
@@ -37,7 +37,7 @@ void
file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping)
{
ra->ra_pages = mapping->backing_dev_info->ra_pages;
- ra->prev_page = -1;
+ ra->prev_index = -1;
}
EXPORT_SYMBOL_GPL(file_ra_state_init);
@@ -202,19 +202,19 @@ out:
* size: Number of pages in that read
* Together, these form the "current window".
* Together, start and size represent the `readahead window'.
- * prev_page: The page which the readahead algorithm most-recently inspected.
+ * prev_index: The page which the readahead algorithm most-recently inspected.
* It is mainly used to detect sequential file reading.
* If page_cache_readahead sees that it is again being called for
* a page which it just looked at, it can return immediately without
* making any state changes.
- * offset: Offset in the prev_page where the last read ended - used for
+ * offset: Offset in the prev_index where the last read ended - used for
* detection of sequential file reading.
* ahead_start,
* ahead_size: Together, these form the "ahead window".
* ra_pages: The externally controlled max readahead for this fd.
*
* When readahead is in the off state (size == 0), readahead is disabled.
- * In this state, prev_page is used to detect the resumption of sequential I/O.
+ * In this state, prev_index is used to detect the resumption of sequential I/O.
*
* The readahead code manages two windows - the "current" and the "ahead"
* windows. The intent is that while the application is walking the pages
@@ -417,7 +417,7 @@ static int make_ahead_window(struct addr
ra->ahead_size = get_next_ra_size(ra);
ra->ahead_start = ra->start + ra->size;
- block = force || (ra->prev_page >= ra->ahead_start);
+ block = force || (ra->prev_index >= ra->ahead_start);
ret = blockable_page_cache_readahead(mapping, filp,
ra->ahead_start, ra->ahead_size, ra, block);
@@ -469,13 +469,13 @@ page_cache_readahead(struct address_spac
* We avoid doing extra work and bogusly perturbing the readahead
* window expansion logic.
*/
- if (offset == ra->prev_page && --req_size)
+ if (offset == ra->prev_index && --req_size)
++offset;
- /* Note that prev_page == -1 if it is a first read */
- sequential = (offset == ra->prev_page + 1);
- ra->prev_page = offset;
- ra->offset = 0;
+ /* Note that prev_index == -1 if it is a first read */
+ sequential = (offset == ra->prev_index + 1);
+ ra->prev_index = offset;
+ ra->prev_offset = 0;
max = get_max_readahead(ra);
newsize = min(req_size, max);
@@ -484,7 +484,7 @@ page_cache_readahead(struct address_spac
if (newsize == 0 || (ra->flags & RA_FLAG_INCACHE))
goto out;
- ra->prev_page += newsize - 1;
+ ra->prev_index += newsize - 1;
/*
* Special case - first read at start of file. We'll assume it's
@@ -540,18 +540,18 @@ page_cache_readahead(struct address_spac
* we get called back on the first page of the ahead window which
* will allow us to submit more IO.
*/
- if (ra->prev_page >= ra->ahead_start) {
+ if (ra->prev_index >= ra->ahead_start) {
ra->start = ra->ahead_start;
ra->size = ra->ahead_size;
make_ahead_window(mapping, filp, ra, 0);
recheck:
- /* prev_page shouldn't overrun the ahead window */
- ra->prev_page = min(ra->prev_page,
+ /* prev_index shouldn't overrun the ahead window */
+ ra->prev_index = min(ra->prev_index,
ra->ahead_start + ra->ahead_size - 1);
}
out:
- return ra->prev_page + 1;
+ return ra->prev_index + 1;
}
EXPORT_SYMBOL_GPL(page_cache_readahead);
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