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Commit ebf43500 authored by Jens Axboe's avatar Jens Axboe Committed by Jens Axboe
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[PATCH] Add find_get_pages_contig(): contiguous variant of find_get_pages() 



find_get_pages_contig() will break out if we hit a hole in the page cache.
From Andrew Morton, small modifications and documentation by me.

Signed-off-by: default avatarJens Axboe <axboe@suse.de>
parent eb645a24

include/linux/pagemap.h

+2 −0
Original line number Diff line number Diff line
@@ -78,6 +78,8 @@ extern struct page * find_or_create_page(struct address_space *mapping, 
				unsigned long index, gfp_t gfp_mask);

unsigned find_get_pages(struct address_space *mapping, pgoff_t start,

			unsigned int nr_pages, struct page **pages);

unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,

			       unsigned int nr_pages, struct page **pages);

unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,

			int tag, unsigned int nr_pages, struct page **pages);

mm/filemap.c

+32 −0
Original line number Diff line number Diff line
@@ -697,6 +697,38 @@ unsigned find_get_pages(struct address_space *mapping, pgoff_t start, 
	return ret;

}



/**

 * find_get_pages_contig - gang contiguous pagecache lookup

 * @mapping:	The address_space to search

 * @index:	The starting page index

 * @nr_pages:	The maximum number of pages

 * @pages:	Where the resulting pages are placed

 *

 * find_get_pages_contig() works exactly like find_get_pages(), except

 * that the returned number of pages are guaranteed to be contiguous.

 *

 * find_get_pages_contig() returns the number of pages which were found.

 */

unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,

			       unsigned int nr_pages, struct page **pages)

{

	unsigned int i;

	unsigned int ret;



	read_lock_irq(&mapping->tree_lock);

	ret = radix_tree_gang_lookup(&mapping->page_tree,

				(void **)pages, index, nr_pages);

	for (i = 0; i < ret; i++) {

		if (pages[i]->mapping == NULL || pages[i]->index != index)

			break;



		page_cache_get(pages[i]);

		index++;

	}

	read_unlock_irq(&mapping->tree_lock);

	return i;

}



/*

 * Like find_get_pages, except we only return pages which are tagged with

 * `tag'.   We update *index to index the next page for the traversal.