Commit 868f604b authored by NeilBrown's avatar NeilBrown Committed by Shaohua Li
Browse files

md/linear: improve bio splitting. 



linear_make_request() uses fs_bio_set, which is meant for filesystems
to use, and loops, possible allocating  from the same bio set multiple
times.
These behaviors can theoretically cause deadlocks, though as
linear requests are hardly ever split, it is unlikely in practice.

Change to use mddev->bio_set - otherwise unused for linear, and submit
the tail of a split request to generic_make_request() for it to
handle.

Signed-off-by: default avatarNeilBrown <neilb@suse.com>
Signed-off-by: default avatarShaohua Li <shli@fb.com>
parent dd7a8f5d

drivers/md/linear.c

+34 −39
Original line number Diff line number Diff line
@@ -249,53 +249,48 @@ static void linear_make_request(struct mddev *mddev, struct bio *bio) 
{

	char b[BDEVNAME_SIZE];

	struct dev_info *tmp_dev;

	struct bio *split;

	sector_t start_sector, end_sector, data_offset;

	sector_t bio_sector = bio->bi_iter.bi_sector;



	if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {

		md_flush_request(mddev, bio);

		return;

	}



	do {

		sector_t bio_sector = bio->bi_iter.bi_sector;

	tmp_dev = which_dev(mddev, bio_sector);

	start_sector = tmp_dev->end_sector - tmp_dev->rdev->sectors;

	end_sector = tmp_dev->end_sector;

	data_offset = tmp_dev->rdev->data_offset;

		bio->bi_bdev = tmp_dev->rdev->bdev;



	if (unlikely(bio_sector >= end_sector ||

		     bio_sector < start_sector))

		goto out_of_bounds;



	if (unlikely(bio_end_sector(bio) > end_sector)) {

			/* This bio crosses a device boundary, so we have to

			 * split it.

			 */

			split = bio_split(bio, end_sector - bio_sector,

					  GFP_NOIO, fs_bio_set);

		/* This bio crosses a device boundary, so we have to split it */

		struct bio *split = bio_split(bio, end_sector - bio_sector,

					      GFP_NOIO, mddev->bio_set);

		bio_chain(split, bio);

		} else {

			split = bio;

		generic_make_request(bio);

		bio = split;

	}



		split->bi_iter.bi_sector = split->bi_iter.bi_sector -

	bio->bi_bdev = tmp_dev->rdev->bdev;

	bio->bi_iter.bi_sector = bio->bi_iter.bi_sector -

		start_sector + data_offset;



		if (unlikely((bio_op(split) == REQ_OP_DISCARD) &&

			 !blk_queue_discard(bdev_get_queue(split->bi_bdev)))) {

	if (unlikely((bio_op(bio) == REQ_OP_DISCARD) &&

		     !blk_queue_discard(bdev_get_queue(bio->bi_bdev)))) {

		/* Just ignore it */

			bio_endio(split);

		bio_endio(bio);

	} else {

		if (mddev->gendisk)

				trace_block_bio_remap(bdev_get_queue(split->bi_bdev),

						      split, disk_devt(mddev->gendisk),

			trace_block_bio_remap(bdev_get_queue(bio->bi_bdev),

					      bio, disk_devt(mddev->gendisk),

					      bio_sector);

			mddev_check_writesame(mddev, split);

			generic_make_request(split);

		mddev_check_writesame(mddev, bio);

		generic_make_request(bio);

	}

	} while (split != bio);

	return;



out_of_bounds:

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