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Commit eb20796b authored by Jens Axboe's avatar Jens Axboe
Browse files

[PATCH] splice: make the read-side do batched page lookups 



Use the new find_get_pages_contig() to potentially look up the entire
splice range in one single call. This speeds up generic_file_splice_read()
quite a bit.

Signed-off-by: default avatarJens Axboe <axboe@suse.de>
parent ebf43500

fs/splice.c

+65 −30
Original line number Diff line number Diff line
@@ -279,7 +279,7 @@ __generic_file_splice_read(struct file *in, loff_t *ppos, 
	pgoff_t index, end_index;

	loff_t isize;

	size_t total_len;

	int error;

	int error, page_nr;

	struct splice_pipe_desc spd = {

		.pages = pages,

		.partial = partial,
@@ -307,24 +307,26 @@ __generic_file_splice_read(struct file *in, loff_t *ppos, 
	 */

	error = 0;

	total_len = 0;

	for (spd.nr_pages = 0; spd.nr_pages < nr_pages; spd.nr_pages++, index++) {

		unsigned int this_len;



		if (!len)

			break;

	/*

	 * Lookup the (hopefully) full range of pages we need.

	 */

	spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);



	/*

		 * this_len is the max we'll use from this page

	 * If find_get_pages_contig() returned fewer pages than we needed,

	 * allocate the rest.

	 */

		this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);

find_page:

	index += spd.nr_pages;

	while (spd.nr_pages < nr_pages) {

		/*

		 * lookup the page for this index

		 * Page could be there, find_get_pages_contig() breaks on

		 * the first hole.

		 */

		page = find_get_page(mapping, index);

		if (!page) {

			/*

			 * page didn't exist, allocate one

			 * page didn't exist, allocate one.

			 */

			page = page_cache_alloc_cold(mapping);

			if (!page)
@@ -336,10 +338,36 @@ find_page: 
				page_cache_release(page);

				break;

			}

			/*

			 * add_to_page_cache() locks the page, unlock it

			 * to avoid convoluting the logic below even more.

			 */

			unlock_page(page);

		}



			goto readpage;

		pages[spd.nr_pages++] = page;

		index++;

	}



	/*

	 * Now loop over the map and see if we need to start IO on any

	 * pages, fill in the partial map, etc.

	 */

	index = *ppos >> PAGE_CACHE_SHIFT;

	nr_pages = spd.nr_pages;

	spd.nr_pages = 0;

	for (page_nr = 0; page_nr < nr_pages; page_nr++) {

		unsigned int this_len;



		if (!len)

			break;



		/*

		 * this_len is the max we'll use from this page

		 */

		this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);

		page = pages[page_nr];



		/*

		 * If the page isn't uptodate, we may need to start io on it

		 */
@@ -360,7 +388,6 @@ find_page: 
			 */

			if (!page->mapping) {

				unlock_page(page);

				page_cache_release(page);

				break;

			}

			/*
@@ -371,16 +398,20 @@ find_page: 
				goto fill_it;

			}



readpage:

			/*

			 * need to read in the page

			 */

			error = mapping->a_ops->readpage(in, page);



			if (unlikely(error)) {

				page_cache_release(page);

				/*

				 * We really should re-lookup the page here,

				 * but it complicates things a lot. Instead

				 * lets just do what we already stored, and

				 * we'll get it the next time we are called.

				 */

				if (error == AOP_TRUNCATED_PAGE)

					goto find_page;

					error = 0;



				break;

			}
@@ -389,10 +420,8 @@ readpage: 
			 */

			isize = i_size_read(mapping->host);

			end_index = (isize - 1) >> PAGE_CACHE_SHIFT;

			if (unlikely(!isize || index > end_index)) {

				page_cache_release(page);

			if (unlikely(!isize || index > end_index))

				break;

			}



			/*

			 * if this is the last page, see if we need to shrink
@@ -400,27 +429,33 @@ readpage: 
			 */

			if (end_index == index) {

				loff = PAGE_CACHE_SIZE - (isize & ~PAGE_CACHE_MASK);

				if (total_len + loff > isize) {

					page_cache_release(page);

				if (total_len + loff > isize)

					break;

				}

				/*

				 * force quit after adding this page

				 */

				nr_pages = spd.nr_pages;

				len = this_len;

				this_len = min(this_len, loff);

				loff = 0;

			}

		}

fill_it:

		pages[spd.nr_pages] = page;

		partial[spd.nr_pages].offset = loff;

		partial[spd.nr_pages].len = this_len;

		partial[page_nr].offset = loff;

		partial[page_nr].len = this_len;

		len -= this_len;

		total_len += this_len;

		loff = 0;

		spd.nr_pages++;

		index++;

	}



	/*

	 * Release any pages at the end, if we quit early. 'i' is how far

	 * we got, 'nr_pages' is how many pages are in the map.

	 */

	while (page_nr < nr_pages)

		page_cache_release(pages[page_nr++]);



	if (spd.nr_pages)

		return splice_to_pipe(pipe, &spd);