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 Cc: Nick Piggin Signed-off-by: Fengguang Wu --- mm/filemap.c | 20 +++++++++----------- 1 file changed, 9 insertions(+), 11 deletions(-) --- linux-2.6.22-rc6-mm1.orig/mm/filemap.c +++ linux-2.6.22-rc6-mm1/mm/filemap.c @@ -863,7 +863,7 @@ static void shrink_readahead_size_eio(st * 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, @@ -877,12 +877,11 @@ void do_generic_mapping_read(struct addr unsigned long prev_index; unsigned int prev_offset; int error; - struct file_ra_state ra = *_ra; 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; @@ -897,7 +896,7 @@ 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)) @@ -905,7 +904,7 @@ find_page: } if (PageReadahead(page)) { page_cache_async_readahead(mapping, - &ra, filp, page, + ra, filp, page, index, last_index - index); } if (!PageUptodate(page)) @@ -1016,7 +1015,7 @@ readpage: } unlock_page(page); error = -EIO; - shrink_readahead_size_eio(filp, &ra); + shrink_readahead_size_eio(filp, ra); goto readpage_error; } unlock_page(page); @@ -1053,10 +1052,9 @@ 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 (filp) -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/