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| author | Fengguang Wu <wfg@mail.ustc.edu.cn> | 2007-10-16 01:24:35 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-10-16 09:42:52 -0700 |
| commit | 7ff81078d8b9f3d05a27b7bd3786ffb1ef1b0d1f (patch) | |
| tree | ac73cf0c8325783a28c4d16c783f6fd96d17be7c /mm/filemap.c | |
| parent | 6b10c6c9fbfe754e8482efb8c8b84f8e40c0f2eb (diff) | |
| download | lwn-7ff81078d8b9f3d05a27b7bd3786ffb1ef1b0d1f.tar.gz lwn-7ff81078d8b9f3d05a27b7bd3786ffb1ef1b0d1f.zip | |
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>
Diffstat (limited to 'mm/filemap.c')
| -rw-r--r-- | mm/filemap.c | 20 |
1 files changed, 9 insertions, 11 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index bbcca456d8a6..3c97bdc74a85 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -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) |