Commit c1f6925e authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Linus Torvalds
Browse files

mm: put readahead pages in cache earlier 



When populating the page cache for readahead, mappings that use
->readpages must populate the page cache themselves as the pages are
passed on a linked list which would normally be used for the page
cache's LRU.  For mappings that use ->readpage or the upcoming
->readahead method, we can put the pages into the page cache as soon as
they're allocated, which solves a race between readahead and direct IO.
It also lets us remove the gfp argument from read_pages().

Use the new readahead_page() API to implement the repeated calls to
->readpage(), just like most filesystems will.

Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarWilliam Kucharski <william.kucharski@oracle.com>
Cc: Chao Yu <yuchao0@huawei.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Gao Xiang <gaoxiang25@huawei.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Link: http://lkml.kernel.org/r/20200414150233.24495-11-willy@infradead.org


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ef8153b6

mm/readahead.c

+28 −18
Original line number Diff line number Diff line
@@ -114,14 +114,14 @@ int read_cache_pages(struct address_space *mapping, struct list_head *pages, 
EXPORT_SYMBOL(read_cache_pages);



static void read_pages(struct readahead_control *rac, struct list_head *pages,

		gfp_t gfp)

		bool skip_page)

{

	const struct address_space_operations *aops = rac->mapping->a_ops;

	struct page *page;

	struct blk_plug plug;

	unsigned page_idx;



	if (!readahead_count(rac))

		return;

		goto out;



	blk_start_plug(&plug);
@@ -130,23 +130,23 @@ static void read_pages(struct readahead_control *rac, struct list_head *pages, 
				readahead_count(rac));

		/* Clean up the remaining pages */

		put_pages_list(pages);

		goto out;

	}



	for (page_idx = 0; page_idx < readahead_count(rac); page_idx++) {

		struct page *page = lru_to_page(pages);

		list_del(&page->lru);

		if (!add_to_page_cache_lru(page, rac->mapping, page->index,

				gfp))

		rac->_index += rac->_nr_pages;

		rac->_nr_pages = 0;

	} else {

		while ((page = readahead_page(rac))) {

			aops->readpage(rac->file, page);

			put_page(page);

		}

	}



out:

	blk_finish_plug(&plug);



	BUG_ON(!list_empty(pages));

	rac->_nr_pages = 0;

	BUG_ON(readahead_count(rac));



out:

	if (skip_page)

		rac->_index++;

}



/*
@@ -168,6 +168,7 @@ void __do_page_cache_readahead(struct address_space *mapping, 
	struct readahead_control rac = {

		.mapping = mapping,

		.file = filp,

		._index = index,

	};

	unsigned long i;
@@ -183,6 +184,8 @@ void __do_page_cache_readahead(struct address_space *mapping, 
		if (index + i > end_index)

			break;



		BUG_ON(index + i != rac._index + rac._nr_pages);



		page = xa_load(&mapping->i_pages, index + i);

		if (page && !xa_is_value(page)) {

			/*
@@ -190,15 +193,22 @@ void __do_page_cache_readahead(struct address_space *mapping, 
			 * contiguous pages before continuing with the next

			 * batch.

			 */

			read_pages(&rac, &page_pool, gfp_mask);

			read_pages(&rac, &page_pool, true);

			continue;

		}



		page = __page_cache_alloc(gfp_mask);

		if (!page)

			break;

		if (mapping->a_ops->readpages) {

			page->index = index + i;

			list_add(&page->lru, &page_pool);

		} else if (add_to_page_cache_lru(page, mapping, index + i,

					gfp_mask) < 0) {

			put_page(page);

			read_pages(&rac, &page_pool, true);

			continue;

		}

		if (i == nr_to_read - lookahead_size)

			SetPageReadahead(page);

		rac._nr_pages++;
@@ -209,7 +219,7 @@ void __do_page_cache_readahead(struct address_space *mapping, 
	 * uptodate then the caller will launch readpage again, and

	 * will then handle the error.

	 */

	read_pages(&rac, &page_pool, gfp_mask);

	read_pages(&rac, &page_pool, false);

}



/*

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