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Commit d094d686 authored by NeilBrown's avatar NeilBrown Committed by Shaohua Li
Browse files

md/raid10: add rcu protection to rdev access during reshape. 



mirrors[].rdev can become NULL at any point unless:
   - a counted reference is held
   - ->reconfig_mutex is held, or
   - rcu_read_lock() is held

Reshape isn't always suitably careful as in the past rdev couldn't be
removed during reshape.  It can now, so add protection.

Signed-off-by: default avatarNeilBrown <neilb@suse.com>
Signed-off-by: default avatarShaohua Li <shli@fb.com>
parent f90145f3

drivers/md/raid10.c

+22 −8
Original line number Diff line number Diff line
@@ -4361,15 +4361,16 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, 
	blist = read_bio;

	read_bio->bi_next = NULL;



	rcu_read_lock();

	for (s = 0; s < conf->copies*2; s++) {

		struct bio *b;

		int d = r10_bio->devs[s/2].devnum;

		struct md_rdev *rdev2;

		if (s&1) {

			rdev2 = conf->mirrors[d].replacement;

			rdev2 = rcu_dereference(conf->mirrors[d].replacement);

			b = r10_bio->devs[s/2].repl_bio;

		} else {

			rdev2 = conf->mirrors[d].rdev;

			rdev2 = rcu_dereference(conf->mirrors[d].rdev);

			b = r10_bio->devs[s/2].bio;

		}

		if (!rdev2 || test_bit(Faulty, &rdev2->flags))
@@ -4414,6 +4415,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, 
		nr_sectors += len >> 9;

	}

bio_full:

	rcu_read_unlock();

	r10_bio->sectors = nr_sectors;



	/* Now submit the read */
@@ -4465,16 +4467,20 @@ static void reshape_request_write(struct mddev *mddev, struct r10bio *r10_bio) 
		struct bio *b;

		int d = r10_bio->devs[s/2].devnum;

		struct md_rdev *rdev;

		rcu_read_lock();

		if (s&1) {

			rdev = conf->mirrors[d].replacement;

			rdev = rcu_dereference(conf->mirrors[d].replacement);

			b = r10_bio->devs[s/2].repl_bio;

		} else {

			rdev = conf->mirrors[d].rdev;

			rdev = rcu_dereference(conf->mirrors[d].rdev);

			b = r10_bio->devs[s/2].bio;

		}

		if (!rdev || test_bit(Faulty, &rdev->flags))

		if (!rdev || test_bit(Faulty, &rdev->flags)) {

			rcu_read_unlock();

			continue;

		}

		atomic_inc(&rdev->nr_pending);

		rcu_read_unlock();

		md_sync_acct(b->bi_bdev, r10_bio->sectors);

		atomic_inc(&r10_bio->remaining);

		b->bi_next = NULL;
@@ -4535,9 +4541,10 @@ static int handle_reshape_read_error(struct mddev *mddev, 
		if (s > (PAGE_SIZE >> 9))

			s = PAGE_SIZE >> 9;



		rcu_read_lock();

		while (!success) {

			int d = r10b->devs[slot].devnum;

			struct md_rdev *rdev = conf->mirrors[d].rdev;

			struct md_rdev *rdev = rcu_dereference(conf->mirrors[d].rdev);

			sector_t addr;

			if (rdev == NULL ||

			    test_bit(Faulty, &rdev->flags) ||
@@ -4545,11 +4552,15 @@ static int handle_reshape_read_error(struct mddev *mddev, 
				goto failed;



			addr = r10b->devs[slot].addr + idx * PAGE_SIZE;

			atomic_inc(&rdev->nr_pending);

			rcu_read_unlock();

			success = sync_page_io(rdev,

					       addr,

					       s << 9,

					       bvec[idx].bv_page,

					       READ, false);

			rdev_dec_pending(rdev, mddev);

			rcu_read_lock();

			if (success)

				break;

		failed:
@@ -4559,6 +4570,7 @@ static int handle_reshape_read_error(struct mddev *mddev, 
			if (slot == first_slot)

				break;

		}

		rcu_read_unlock();

		if (!success) {

			/* couldn't read this block, must give up */

			set_bit(MD_RECOVERY_INTR,
@@ -4628,16 +4640,18 @@ static void raid10_finish_reshape(struct mddev *mddev) 
		}

	} else {

		int d;

		rcu_read_lock();

		for (d = conf->geo.raid_disks ;

		     d < conf->geo.raid_disks - mddev->delta_disks;

		     d++) {

			struct md_rdev *rdev = conf->mirrors[d].rdev;

			struct md_rdev *rdev = rcu_dereference(conf->mirrors[d].rdev);

			if (rdev)

				clear_bit(In_sync, &rdev->flags);

			rdev = conf->mirrors[d].replacement;

			rdev = rcu_dereference(conf->mirrors[d].replacement);

			if (rdev)

				clear_bit(In_sync, &rdev->flags);

		}

		rcu_read_unlock();

	}

	mddev->layout = mddev->new_layout;

	mddev->chunk_sectors = 1 << conf->geo.chunk_shift;