Commit 73d5c38a authored by NeilBrown's avatar NeilBrown
Browse files

md: avoid races when stopping resync. 



There has been a race in raid10 and raid1 for a long time
which has only recently started showing up due to a scheduler changed.

When a sync_read request finishes, as soon as reschedule_retry
is called, another thread can mark the resync request as having
completed, so md_do_sync can finish, ->stop can be called, and
->conf can be freed.  So using conf after reschedule_retry is not
safe.

Similarly, when finishing a sync_write, calling md_done_sync must be
the last thing we do, as it allows a chain of events which will free
conf and other data structures.

The first of these requires action in raid10.c
The second requires action in raid1.c and raid10.c

Cc: stable@kernel.org
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent 78200d45

drivers/md/raid1.c

+2 −1
Original line number Diff line number Diff line
@@ -1237,8 +1237,9 @@ static void end_sync_write(struct bio *bio, int error) 
	update_head_pos(mirror, r1_bio);



	if (atomic_dec_and_test(&r1_bio->remaining)) {

		md_done_sync(mddev, r1_bio->sectors, uptodate);

		sector_t s = r1_bio->sectors;

		put_buf(r1_bio);

		md_done_sync(mddev, s, uptodate);

	}

}

drivers/md/raid10.c

+4 −3
Original line number Diff line number Diff line
@@ -1236,6 +1236,7 @@ static void end_sync_read(struct bio *bio, int error) 
	/* for reconstruct, we always reschedule after a read.

	 * for resync, only after all reads

	 */

	rdev_dec_pending(conf->mirrors[d].rdev, conf->mddev);

	if (test_bit(R10BIO_IsRecover, &r10_bio->state) ||

	    atomic_dec_and_test(&r10_bio->remaining)) {

		/* we have read all the blocks,
@@ -1243,7 +1244,6 @@ static void end_sync_read(struct bio *bio, int error) 
		 */

		reschedule_retry(r10_bio);

	}

	rdev_dec_pending(conf->mirrors[d].rdev, conf->mddev);

}



static void end_sync_write(struct bio *bio, int error)
@@ -1264,11 +1264,13 @@ static void end_sync_write(struct bio *bio, int error) 


	update_head_pos(i, r10_bio);



	rdev_dec_pending(conf->mirrors[d].rdev, mddev);

	while (atomic_dec_and_test(&r10_bio->remaining)) {

		if (r10_bio->master_bio == NULL) {

			/* the primary of several recovery bios */

			md_done_sync(mddev, r10_bio->sectors, 1);

			sector_t s = r10_bio->sectors;

			put_buf(r10_bio);

			md_done_sync(mddev, s, 1);

			break;

		} else {

			r10bio_t *r10_bio2 = (r10bio_t *)r10_bio->master_bio;
@@ -1276,7 +1278,6 @@ static void end_sync_write(struct bio *bio, int error) 
			r10_bio = r10_bio2;

		}

	}

	rdev_dec_pending(conf->mirrors[d].rdev, mddev);

}



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