Commit ee1aa06b authored by Logan Gunthorpe's avatar Logan Gunthorpe Committed by Jens Axboe
Browse files

md/raid5: Convert prepare_to_wait() to wait_woken() api 

raid5_get_active_stripe() can sleep in various situations and it
is called by make_stripe_request() while inside the
prepare_to_wait()/finish_wait() section. Nested waits like this are
not supported.

This was noticed while making other changes that add different sleeps
to raid5_get_active_stripe() that caused a WARNING with
CONFIG_DEBUG_ATOMIC_SLEEP.

No ill effects have been noticed with the code as is, but theoretically
a nested and here could cause a dead lock so it should be fixed.

To fix this, convert the prepare_to_wait() call to use wake_woken()
which supports nested sleeps.

Link: https://lwn.net/Articles/628628/


Signed-off-by: default avatarLogan Gunthorpe <logang@deltatee.com>
Signed-off-by: default avatarSong Liu <song@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent b9f91d80

drivers/md/raid5.c

+6 −7
Original line number Diff line number Diff line
@@ -6044,12 +6044,12 @@ static enum stripe_result make_stripe_request(struct mddev *mddev, 


static bool raid5_make_request(struct mddev *mddev, struct bio * bi)

{

	DEFINE_WAIT_FUNC(wait, woken_wake_function);

	struct r5conf *conf = mddev->private;

	sector_t logical_sector;

	struct stripe_request_ctx ctx = {};

	const int rw = bio_data_dir(bi);

	enum stripe_result res;

	DEFINE_WAIT(w);

	int s, stripe_cnt;



	if (unlikely(bi->bi_opf & REQ_PREFLUSH)) {
@@ -6112,7 +6112,8 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi) 
		return true;

	}

	md_account_bio(mddev, &bi);

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



	add_wait_queue(&conf->wait_for_overlap, &wait);

	while (1) {

		res = make_stripe_request(mddev, conf, &ctx, logical_sector,

					  bi);
@@ -6135,9 +6136,8 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi) 
				ctx.batch_last = NULL;

			}



			schedule();

			prepare_to_wait(&conf->wait_for_overlap, &w,

					TASK_UNINTERRUPTIBLE);

			wait_woken(&wait, TASK_UNINTERRUPTIBLE,

				   MAX_SCHEDULE_TIMEOUT);

			continue;

		}
@@ -6148,8 +6148,7 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi) 
		logical_sector = ctx.first_sector +

			(s << RAID5_STRIPE_SHIFT(conf));

	}



	finish_wait(&conf->wait_for_overlap, &w);

	remove_wait_queue(&conf->wait_for_overlap, &wait);



	if (ctx.batch_last)

		raid5_release_stripe(ctx.batch_last);