Commit 550cdeb3 authored by Qu Wenruo's avatar Qu Wenruo Committed by David Sterba
Browse files

btrfs: raid56: avoid double for loop inside raid56_rmw_stripe() 



This function doesn't even utilize full stripe skip, just iterate all
the data sectors is definitely enough.

Signed-off-by: default avatarQu Wenruo <wqu@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent aee35e4b

fs/btrfs/raid56.c

+28 −31
Original line number Diff line number Diff line
@@ -1547,9 +1547,9 @@ static int raid56_rmw_stripe(struct btrfs_raid_bio *rbio) 
{

	int bios_to_read = 0;

	struct bio_list bio_list;

	const int nr_data_sectors = rbio->stripe_nsectors * rbio->nr_data;

	int ret;

	int sectornr;

	int stripe;

	int total_sector_nr;

	struct bio *bio;



	bio_list_init(&bio_list);
@@ -1561,19 +1561,17 @@ static int raid56_rmw_stripe(struct btrfs_raid_bio *rbio) 
	index_rbio_pages(rbio);



	atomic_set(&rbio->error, 0);

	/*

	 * build a list of bios to read all the missing parts of this

	 * stripe

	 */

	for (stripe = 0; stripe < rbio->nr_data; stripe++) {

		for (sectornr = 0; sectornr < rbio->stripe_nsectors; sectornr++) {

	/* Build a list of bios to read all the missing data sectors. */

	for (total_sector_nr = 0; total_sector_nr < nr_data_sectors;

	     total_sector_nr++) {

		struct sector_ptr *sector;

		int stripe = total_sector_nr / rbio->stripe_nsectors;

		int sectornr = total_sector_nr % rbio->stripe_nsectors;



		/*

			 * We want to find all the sectors missing from the

			 * rbio and read them from the disk.  If * sector_in_rbio()

			 * finds a page in the bio list we don't need to read

			 * it off the stripe.

		 * We want to find all the sectors missing from the rbio and

		 * read them from the disk.  If sector_in_rbio() finds a page

		 * in the bio list we don't need to read it off the stripe.

		 */

		sector = sector_in_rbio(rbio, stripe, sectornr, 1);

		if (sector)
@@ -1581,8 +1579,8 @@ static int raid56_rmw_stripe(struct btrfs_raid_bio *rbio) 


		sector = rbio_stripe_sector(rbio, stripe, sectornr);

		/*

			 * The bio cache may have handed us an uptodate page.

			 * If so, be happy and use it.

		 * The bio cache may have handed us an uptodate page.  If so,

		 * use it.

		 */

		if (sector->uptodate)

			continue;
@@ -1593,7 +1591,6 @@ static int raid56_rmw_stripe(struct btrfs_raid_bio *rbio) 
		if (ret)

			goto cleanup;

	}

	}



	bios_to_read = bio_list_size(&bio_list);

	if (!bios_to_read) {