Commit c46501b2 authored by NeilBrown's avatar NeilBrown
Browse files

md/raid5: use seqcount to protect access to shape in make_request. 



make_request() access various shape parameters (raid_disks, chunk_size
etc) which might be changed by raid5_start_reshape().

If the later is called at and awkward time during the form, the wrong
stripe_head might be used.

So introduce a 'seqcount' and after finding a stripe_head make sure
there is no reason to expect that we got the wrong one.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent b721420e

drivers/md/raid5.c

+13 −1
Original line number Diff line number Diff line
@@ -4408,8 +4408,10 @@ static void make_request(struct mddev *mddev, struct bio * bi) 
	for (;logical_sector < last_sector; logical_sector += STRIPE_SECTORS) {

		DEFINE_WAIT(w);

		int previous;

		int seq;



	retry:

		seq = read_seqcount_begin(&conf->gen_lock);

		previous = 0;

		prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);

		if (unlikely(conf->reshape_progress != MaxSector)) {
@@ -4471,6 +4473,13 @@ static void make_request(struct mddev *mddev, struct bio * bi) 
					goto retry;

				}

			}

			if (read_seqcount_retry(&conf->gen_lock, seq)) {

				/* Might have got the wrong stripe_head

				 * by accident

				 */

				release_stripe(sh);

				goto retry;

			}



			if (rw == WRITE &&

			    logical_sector >= mddev->suspend_lo &&
@@ -5437,6 +5446,7 @@ static struct r5conf *setup_conf(struct mddev *mddev) 
	if (alloc_thread_groups(conf, 0))

		goto abort;

	spin_lock_init(&conf->device_lock);

	seqcount_init(&conf->gen_lock);

	init_waitqueue_head(&conf->wait_for_stripe);

	init_waitqueue_head(&conf->wait_for_overlap);

	INIT_LIST_HEAD(&conf->handle_list);
@@ -6249,6 +6259,7 @@ static int raid5_start_reshape(struct mddev *mddev) 


	atomic_set(&conf->reshape_stripes, 0);

	spin_lock_irq(&conf->device_lock);

	write_seqcount_begin(&conf->gen_lock);

	conf->previous_raid_disks = conf->raid_disks;

	conf->raid_disks += mddev->delta_disks;

	conf->prev_chunk_sectors = conf->chunk_sectors;
@@ -6265,6 +6276,7 @@ static int raid5_start_reshape(struct mddev *mddev) 
	else

		conf->reshape_progress = 0;

	conf->reshape_safe = conf->reshape_progress;

	write_seqcount_end(&conf->gen_lock);

	spin_unlock_irq(&conf->device_lock);



	/* Add some new drives, as many as will fit.

drivers/md/raid5.h

+1 −0
Original line number Diff line number Diff line
@@ -400,6 +400,7 @@ struct r5conf { 
	int			prev_chunk_sectors;

	int			prev_algo;

	short			generation; /* increments with every reshape */

	seqcount_t		gen_lock;	/* lock against generation changes */

	unsigned long		reshape_checkpoint; /* Time we last updated

						     * metadata */

	long long		min_offset_diff; /* minimum difference between

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