Commit 9f6dc633 authored by Mike Snitzer's avatar Mike Snitzer
Browse files

dm: interlock pending dm_io and dm_wait_for_bios_completion 



Commit d208b894 ("dm: fix mempool NULL pointer race when
completing IO") didn't go far enough.

When bio_end_io_acct ends the count of in-flight I/Os may reach zero
and the DM device may be suspended. There is a possibility that the
suspend races with dm_stats_account_io.

Fix this by adding percpu "pending_io" counters to track outstanding
dm_io. Move kicking of suspend queue to dm_io_dec_pending(). Also,
rename md_in_flight_bios() to dm_in_flight_bios() and update it to
iterate all pending_io counters.

Fixes: d208b894 ("dm: fix mempool NULL pointer race when completing IO")
Cc: stable@vger.kernel.org
Co-developed-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent bcd2be76

drivers/md/dm-core.h

+2 −0
Original line number Diff line number Diff line
@@ -64,6 +64,8 @@ struct mapped_device { 
	struct gendisk *disk;

	struct dax_device *dax_dev;



	unsigned long __percpu *pending_io;



	/*

	 * A list of ios that arrived while we were suspended.

	 */

drivers/md/dm.c

+23 −12
Original line number Diff line number Diff line
@@ -508,10 +508,6 @@ static void end_io_acct(struct mapped_device *md, struct bio *bio, 
		dm_stats_account_io(&md->stats, bio_data_dir(bio),

				    bio->bi_iter.bi_sector, bio_sectors(bio),

				    true, duration, stats_aux);



	/* nudge anyone waiting on suspend queue */

	if (unlikely(wq_has_sleeper(&md->wait)))

		wake_up(&md->wait);

}



static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio)
@@ -530,6 +526,7 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio) 
	io->magic = DM_IO_MAGIC;

	io->status = 0;

	atomic_set(&io->io_count, 1);

	this_cpu_inc(*md->pending_io);

	io->orig_bio = bio;

	io->md = md;

	spin_lock_init(&io->endio_lock);
@@ -827,6 +824,12 @@ void dm_io_dec_pending(struct dm_io *io, blk_status_t error) 
		stats_aux = io->stats_aux;

		free_io(md, io);

		end_io_acct(md, bio, start_time, &stats_aux);

		smp_wmb();

		this_cpu_dec(*md->pending_io);



		/* nudge anyone waiting on suspend queue */

		if (unlikely(wq_has_sleeper(&md->wait)))

			wake_up(&md->wait);



		if (io_error == BLK_STS_DM_REQUEUE)

			return;
@@ -1569,6 +1572,11 @@ static void cleanup_mapped_device(struct mapped_device *md) 
		blk_cleanup_disk(md->disk);

	}



	if (md->pending_io) {

		free_percpu(md->pending_io);

		md->pending_io = NULL;

	}



	cleanup_srcu_struct(&md->io_barrier);



	mutex_destroy(&md->suspend_lock);
@@ -1671,6 +1679,10 @@ static struct mapped_device *alloc_dev(int minor) 
	if (!md->wq)

		goto bad;



	md->pending_io = alloc_percpu(unsigned long);

	if (!md->pending_io)

		goto bad;



	dm_stats_init(&md->stats);



	/* Populate the mapping, nobody knows we exist yet */
@@ -2078,16 +2090,13 @@ void dm_put(struct mapped_device *md) 
}

EXPORT_SYMBOL_GPL(dm_put);



static bool md_in_flight_bios(struct mapped_device *md)

static bool dm_in_flight_bios(struct mapped_device *md)

{

	int cpu;

	struct block_device *part = dm_disk(md)->part0;

	long sum = 0;

	unsigned long sum = 0;



	for_each_possible_cpu(cpu) {

		sum += part_stat_local_read_cpu(part, in_flight[0], cpu);

		sum += part_stat_local_read_cpu(part, in_flight[1], cpu);

	}

	for_each_possible_cpu(cpu)

		sum += *per_cpu_ptr(md->pending_io, cpu);



	return sum != 0;

}
@@ -2100,7 +2109,7 @@ static int dm_wait_for_bios_completion(struct mapped_device *md, unsigned int ta 
	while (true) {

		prepare_to_wait(&md->wait, &wait, task_state);



		if (!md_in_flight_bios(md))

		if (!dm_in_flight_bios(md))

			break;



		if (signal_pending_state(task_state, current)) {
@@ -2112,6 +2121,8 @@ static int dm_wait_for_bios_completion(struct mapped_device *md, unsigned int ta 
	}

	finish_wait(&md->wait, &wait);



	smp_rmb();



	return r;

}