Commit 78a2ef1b authored by Christoph Hellwig's avatar Christoph Hellwig Committed by David Sterba
Browse files

btrfs: check for contiguity in submit_extent_page 



Different loop iterations in btrfs_bio_add_page not only have the same
contiguity parameters, but also any non-initial operation operates on a
fresh bio anyway.

Factor out the contiguity check into a new btrfs_bio_is_contig and only
call it once in submit_extent_page before descending into the
bio_add_page loop.

Reviewed-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 5380311f

fs/btrfs/extent_io.c

+36 −33
Original line number Diff line number Diff line
@@ -866,6 +866,38 @@ int btrfs_alloc_page_array(unsigned int nr_pages, struct page **page_array) 
	return 0;

}



static bool btrfs_bio_is_contig(struct btrfs_bio_ctrl *bio_ctrl,

				struct page *page, u64 disk_bytenr,

				unsigned int pg_offset)

{

	struct bio *bio = bio_ctrl->bio;

	struct bio_vec *bvec = bio_last_bvec_all(bio);

	const sector_t sector = disk_bytenr >> SECTOR_SHIFT;



	if (bio_ctrl->compress_type != BTRFS_COMPRESS_NONE) {

		/*

		 * For compression, all IO should have its logical bytenr set

		 * to the starting bytenr of the compressed extent.

		 */

		return bio->bi_iter.bi_sector == sector;

	}



	/*

	 * The contig check requires the following conditions to be met:

	 *

	 * 1) The pages are belonging to the same inode

	 *    This is implied by the call chain.

	 *

	 * 2) The range has adjacent logical bytenr

	 *

	 * 3) The range has adjacent file offset

	 *    This is required for the usage of btrfs_bio->file_offset.

	 */

	return bio_end_sector(bio) == sector &&

		page_offset(bvec->bv_page) + bvec->bv_offset + bvec->bv_len ==

		page_offset(page) + pg_offset;

}



/*

 * Attempt to add a page to bio.

 *
@@ -890,44 +922,11 @@ static int btrfs_bio_add_page(struct btrfs_bio_ctrl *bio_ctrl, 
	struct bio *bio = bio_ctrl->bio;

	u32 bio_size = bio->bi_iter.bi_size;

	u32 real_size;

	const sector_t sector = disk_bytenr >> SECTOR_SHIFT;

	bool contig = false;



	ASSERT(bio);

	/* The limit should be calculated when bio_ctrl->bio is allocated */

	ASSERT(bio_ctrl->len_to_oe_boundary);



	if (bio->bi_iter.bi_size == 0) {

		/* We can always add a page into an empty bio. */

		contig = true;

	} else if (bio_ctrl->compress_type == BTRFS_COMPRESS_NONE) {

		struct bio_vec *bvec = bio_last_bvec_all(bio);



		/*

		 * The contig check requires the following conditions to be met:

		 * 1) The pages are belonging to the same inode

		 *    This is implied by the call chain.

		 *

		 * 2) The range has adjacent logical bytenr

		 *

		 * 3) The range has adjacent file offset

		 *    This is required for the usage of btrfs_bio->file_offset.

		 */

		if (bio_end_sector(bio) == sector &&

		    page_offset(bvec->bv_page) + bvec->bv_offset +

		    bvec->bv_len == page_offset(page) + pg_offset)

			contig = true;

	} else {

		/*

		 * For compression, all IO should have its logical bytenr

		 * set to the starting bytenr of the compressed extent.

		 */

		contig = bio->bi_iter.bi_sector == sector;

	}



	if (!contig)

		return 0;



	real_size = min(bio_ctrl->len_to_oe_boundary - bio_size, size);



	/*
@@ -1024,6 +1023,10 @@ static void submit_extent_page(struct btrfs_bio_ctrl *bio_ctrl, 


	ASSERT(bio_ctrl->end_io_func);



	if (bio_ctrl->bio &&

	    !btrfs_bio_is_contig(bio_ctrl, page, disk_bytenr, pg_offset))

		submit_one_bio(bio_ctrl);



	while (cur < pg_offset + size) {

		u32 offset = cur - pg_offset;

		int added;