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readahead: remove the local copy of ra in do_generic_mapping_read() 

The local copy of ra in do_generic_mapping_read() can now go away.

It predates readanead(req_size).  In a time when the readahead code was called
on *every* single page.  Hence a local has to be made to reduce the chance of
the readahead state being overwritten by a concurrent reader.  More details
in: Linux: Random File I/O Regressions In 2.6
<http://kerneltrap.org/node/3039>

Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Fengguang Wu 2007-10-16 01:24:35 -07:00 committed by Linus Torvalds
parent 6b10c6c9fb
commit 7ff81078d8
1 changed files with 9 additions and 11 deletions
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20
mm/filemap.c
View File

@ -859,7 +859,7 @@ static void shrink_readahead_size_eio(struct file *filp,
* It may be NULL.
*/
void do_generic_mapping_read(struct address_space *mapping,
struct file_ra_state *_ra,
struct file_ra_state *ra,
struct file *filp,
loff_t *ppos,
read_descriptor_t *desc,
@ -874,13 +874,12 @@ void do_generic_mapping_read(struct address_space *mapping,
unsigned int prev_offset;
struct page *cached_page;
int error;
struct file_ra_state ra = *_ra;
cached_page = NULL;
index = *ppos >> PAGE_CACHE_SHIFT;
next_index = index;
prev_index = ra.prev_pos >> PAGE_CACHE_SHIFT;
prev_offset = ra.prev_pos & (PAGE_CACHE_SIZE-1);
prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
offset = *ppos & ~PAGE_CACHE_MASK;
@ -895,7 +894,7 @@ find_page:
page = find_get_page(mapping, index);
if (!page) {
page_cache_sync_readahead(mapping,
&ra, filp,
ra, filp,
index, last_index - index);
page = find_get_page(mapping, index);
if (unlikely(page == NULL))
@ -903,7 +902,7 @@ find_page:
}
if (PageReadahead(page)) {
page_cache_async_readahead(mapping,
&ra, filp, page,
ra, filp, page,
index, last_index - index);
}
if (!PageUptodate(page))
@ -1014,7 +1013,7 @@ readpage:
}
unlock_page(page);
error = -EIO;
shrink_readahead_size_eio(filp, &ra);
shrink_readahead_size_eio(filp, ra);
goto readpage_error;
}
unlock_page(page);
@ -1054,10 +1053,9 @@ no_cached_page:
}
out:
*_ra = ra;
_ra->prev_pos = prev_index;
_ra->prev_pos <<= PAGE_CACHE_SHIFT;
_ra->prev_pos |= prev_offset;
ra->prev_pos = prev_index;
ra->prev_pos <<= PAGE_CACHE_SHIFT;
ra->prev_pos |= prev_offset;
*ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
if (cached_page)