Commit 91d6ac1d authored Mar 30, 2022 by Sweet Tea Dorminy Committed by David Sterba May 16, 2022

btrfs: allocate page arrays using bulk page allocator



While calling alloc_page() in a loop is an effective way to populate an
array of pages, the MM subsystem provides a method to allocate pages in
bulk.  alloc_pages_bulk_array() populates the NULL slots in a page
array, trying to grab more than one page at a time.

Unfortunately, it doesn't guarantee allocating all slots in the array,
but it's easy to call it in a loop and return an error if no progress
occurs.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

parent dd137dd1

fs/btrfs/extent_io.c

+11 −8

Original line number	Diff line number	Diff line
		@@ -3146,17 +3146,20 @@ static void end_bio_extent_readpage(struct bio *bio)
		*/
		int btrfs_alloc_page_array(unsigned int nr_pages, struct page **page_array)
		{
		int i;
		unsigned int allocated;

		for (i = 0; i < nr_pages; i++) {
		struct page *page;
		for (allocated = 0; allocated < nr_pages;) {
		unsigned int last = allocated;

		if (page_array[i])
		continue;
		page = alloc_page(GFP_NOFS);
		if (!page)
		allocated = alloc_pages_bulk_array(GFP_NOFS, nr_pages, page_array);

		/*
		* During this iteration, no page could be allocated, even
		* though alloc_pages_bulk_array() falls back to alloc_page()
		* if it could not bulk-allocate. So we must be out of memory.
		*/
		if (allocated == last)
		return -ENOMEM;
		page_array[i] = page;
		}
		return 0;
		}