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Commit 3ea89ee8 authored by Fengguang Wu's avatar Fengguang Wu Committed by Linus Torvalds
Browse files

readahead: convert filemap invocations 



Convert filemap reads to use on-demand readahead.

The new call scheme is to
- call readahead on non-cached page
- call readahead on look-ahead page
- update prev_index when finished with the read request

Signed-off-by: default avatarFengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Steven Pratt <slpratt@austin.ibm.com>
Cc: Ram Pai <linuxram@us.ibm.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 122a21d1

mm/filemap.c

+31 −20
Original line number Diff line number Diff line
@@ -891,16 +891,21 @@ void do_generic_mapping_read(struct address_space *mapping, 
		unsigned long nr, ret;



		cond_resched();

		if (index == next_index)

			next_index = page_cache_readahead(mapping, &ra, filp,

					index, last_index - index);



find_page:

		page = find_get_page(mapping, index);

		if (unlikely(page == NULL)) {

			handle_ra_miss(mapping, &ra, index);

		if (!page) {

			page_cache_readahead_ondemand(mapping,

					&ra, filp, page,

					index, last_index - index);

			page = find_get_page(mapping, index);

			if (unlikely(page == NULL))

				goto no_cached_page;

		}

		if (PageReadahead(page)) {

			page_cache_readahead_ondemand(mapping,

					&ra, filp, page,

					index, last_index - index);

		}

		if (!PageUptodate(page))

			goto page_not_up_to_date;

page_ok:
@@ -1051,6 +1056,7 @@ no_cached_page: 


out:

	*_ra = ra;

	_ra->prev_index = prev_index;



	*ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;

	if (cached_page)
@@ -1332,27 +1338,31 @@ int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) 
	if (VM_RandomReadHint(vma))

		goto no_cached_page;



	/*

	 * The readahead code wants to be told about each and every page

	 * so it can build and shrink its windows appropriately

	 *

	 * For sequential accesses, we use the generic readahead logic.

	 */

	if (VM_SequentialReadHint(vma))

		page_cache_readahead(mapping, ra, file, vmf->pgoff, 1);



	/*

	 * Do we have something in the page cache already?

	 */

retry_find:

	page = find_lock_page(mapping, vmf->pgoff);

	if (!page) {

		unsigned long ra_pages;



	/*

	 * For sequential accesses, we use the generic readahead logic.

	 */

	if (VM_SequentialReadHint(vma)) {

			handle_ra_miss(mapping, ra, vmf->pgoff);

		if (!page) {

			page_cache_readahead_ondemand(mapping, ra, file, page,

							   vmf->pgoff, 1);

			page = find_lock_page(mapping, vmf->pgoff);

			if (!page)

				goto no_cached_page;

		}

		if (PageReadahead(page)) {

			page_cache_readahead_ondemand(mapping, ra, file, page,

							   vmf->pgoff, 1);

		}

	}



	if (!page) {

		unsigned long ra_pages;



		ra->mmap_miss++;



		/*
@@ -1405,6 +1415,7 @@ retry_find: 
	 * Found the page and have a reference on it.

	 */

	mark_page_accessed(page);

	ra->prev_index = page->index;

	vmf->page = page;

	return ret | VM_FAULT_LOCKED;