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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>
This commit is contained in:
Fengguang Wu 2007-07-19 01:48:05 -07:00 committed by Linus Torvalds
parent c743d96b6d
commit 431a4820bf
1 changed files with 6 additions and 5 deletions
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11
fs/splice.c
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@ -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.
*/