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Commit 431a4820 authored by Fengguang Wu's avatar Fengguang Wu Committed by Linus Torvalds
Browse files

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: default avatarFengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c743d96b

fs/splice.c

+6 −5
Original line number Diff line number Diff line
@@ -290,13 +290,17 @@ __generic_file_splice_read(struct file *in, loff_t *ppos, 
	 * 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 @@ __generic_file_splice_read(struct file *in, loff_t *ppos, 
		 */

		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.

			 */