readahead: increase interleaved readahead size

Make sure interleaved readahead size is larger than request size.  This
also makes the readahead window grow up more quickly.

Reported-by: Xu Chenfeng <xcf@ustc.edu.cn>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Ying Han <yinghan@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/readahead.c b/mm/readahead.c
index 5673115..16378b9 100644 (file)
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -403,6 +403,7 @@ ondemand_readahead(struct address_space *mapping,
 
                ra->start = start;
                ra->size = start - offset;      /* old async_size */
+               ra->size += req_size;
                ra->size = get_next_ra_size(ra, max);
                ra->async_size = ra->size;
                goto readit;