readahead: move synchronous readahead call out of splice loop
Move synchronous page_cache_readahead_ondemand() call out of splice loop.
This avoids one pointless page allocation/insertion in case of non-zero
ra_pages, or many pointless readahead calls in case of zero ra_pages.
Note that if a user sets ra_pages to less than PIPE_BUFFERS=16 pages, he will
not get expected readahead behavior anyway. The splice code works in batches
of 16 pages, which can be taken as another form of synchronous readahead.
Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Jens Axboe <jens.axboe@oracle.com>
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>
diff --git a/fs/splice.c b/fs/splice.c
index 722449f..421b3b8 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -290,13 +290,17 @@
* Lookup the (hopefully) full range of pages we need.
*/
spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
+ index += spd.nr_pages;
/*
* If find_get_pages_contig() returned fewer pages than we needed,
- * allocate the rest and fill in the holes.
+ * readahead/allocate the rest and fill in the holes.
*/
+ if (spd.nr_pages < nr_pages)
+ page_cache_readahead_ondemand(mapping, &in->f_ra, in,
+ NULL, index, nr_pages - spd.nr_pages);
+
error = 0;
- index += spd.nr_pages;
while (spd.nr_pages < nr_pages) {
/*
* Page could be there, find_get_pages_contig() breaks on
@@ -304,9 +308,6 @@
*/
page = find_get_page(mapping, index);
if (!page) {
- page_cache_readahead_ondemand(mapping, &in->f_ra, in,
- NULL, index, nr_pages - spd.nr_pages);
-
/*
* page didn't exist, allocate one.
*/