Commit 98423303 authored Feb 24, 2020 by Mikulas Patocka Committed by Greg Kroah-Hartman Mar 11, 2020

dm: report suspended device during destroy



commit adc0daad366b62ca1bce3e2958a40b0b71a8b8b3 upstream.

The function dm_suspended returns true if the target is suspended.
However, when the target is being suspended during unload, it returns
false.

An example where this is a problem: the test "!dm_suspended(wc->ti)" in
writecache_writeback is not sufficient, because dm_suspended returns
zero while writecache_suspend is in progress.  As is, without an
enhanced dm_suspended, simply switching from flush_workqueue to
drain_workqueue still emits warnings:
workqueue writecache-writeback: drain_workqueue() isn't complete after 10 tries
workqueue writecache-writeback: drain_workqueue() isn't complete after 100 tries
workqueue writecache-writeback: drain_workqueue() isn't complete after 200 tries
workqueue writecache-writeback: drain_workqueue() isn't complete after 300 tries
workqueue writecache-writeback: drain_workqueue() isn't complete after 400 tries

writecache_suspend calls flush_workqueue(wc->writeback_wq) - this function
flushes the current work. However, the workqueue may re-queue itself and
flush_workqueue doesn't wait for re-queued works to finish. Because of
this - the function writecache_writeback continues execution after the
device was suspended and then concurrently with writecache_dtr, causing
a crash in writecache_writeback.

We must use drain_workqueue - that waits until the work and all re-queued
works finish.

As a prereq for switching to drain_workqueue, this commit fixes
dm_suspended to return true after the presuspend hook and before the
postsuspend hook - just like during a normal suspend. It allows
simplifying the dm-integrity and dm-writecache targets so that they
don't have to maintain suspended flags on their own.

With this change use of drain_workqueue() can be used effectively.  This
change was tested with the lvm2 testsuite and cryptsetup testsuite and
the are no regressions.

Fixes: 48debafe ("dm: add writecache target")
Cc: stable@vger.kernel.org # 4.18+
Reported-by: Corey Marthaler <cmarthal@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent bc21bbf6

drivers/md/dm-integrity.c

+5 −7

Original line number	Diff line number	Diff line
		@@ -186,12 +186,13 @@ struct dm_integrity_c {
		__u8 sectors_per_block;

		unsigned char mode;
		int suspending;

		int failed;

		struct crypto_shash *internal_hash;

		struct dm_target *ti;

		/* these variables are locked with endio_wait.lock */
		struct rb_root in_progress;
		struct list_head wait_list;
		@@ -2080,7 +2081,7 @@ static void integrity_writer(struct work_struct *w)
		unsigned prev_free_sectors;

		/* the following test is not needed, but it tests the replay code */
		if (READ_ONCE(ic->suspending) && !ic->meta_dev)
		if (unlikely(dm_suspended(ic->ti)) && !ic->meta_dev)
		return;

		spin_lock_irq(&ic->endio_wait.lock);
		@@ -2139,7 +2140,7 @@ static void integrity_recalc(struct work_struct *w)

		next_chunk:

		if (unlikely(READ_ONCE(ic->suspending)))
		if (unlikely(dm_suspended(ic->ti)))
		goto unlock_ret;

		range.logical_sector = le64_to_cpu(ic->sb->recalc_sector);
		@@ -2411,8 +2412,6 @@ static void dm_integrity_postsuspend(struct dm_target *ti)

		del_timer_sync(&ic->autocommit_timer);

		WRITE_ONCE(ic->suspending, 1);

		if (ic->recalc_wq)
		drain_workqueue(ic->recalc_wq);

		@@ -2426,8 +2425,6 @@ static void dm_integrity_postsuspend(struct dm_target *ti)
		dm_integrity_flush_buffers(ic);
		}

		WRITE_ONCE(ic->suspending, 0);

		BUG_ON(!RB_EMPTY_ROOT(&ic->in_progress));

		ic->journal_uptodate = true;
		@@ -3116,6 +3113,7 @@ static int dm_integrity_ctr(struct dm_target ti, unsigned argc, char *argv)
		}
		ti->private = ic;
		ti->per_io_data_size = sizeof(struct dm_integrity_io);
		ic->ti = ti;

		ic->in_progress = RB_ROOT;
		INIT_LIST_HEAD(&ic->wait_list);

drivers/md/dm-writecache.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -844,7 +844,7 @@ static void writecache_suspend(struct dm_target *ti)
		}
		wc_unlock(wc);

		flush_workqueue(wc->writeback_wq);
		drain_workqueue(wc->writeback_wq);

		wc_lock(wc);
		if (flush_on_suspend)

drivers/md/dm.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -2353,6 +2353,7 @@ static void __dm_destroy(struct mapped_device *md, bool wait)
		map = dm_get_live_table(md, &srcu_idx);
		if (!dm_suspended_md(md)) {
		dm_table_presuspend_targets(map);
		set_bit(DMF_SUSPENDED, &md->flags);
		dm_table_postsuspend_targets(map);
		}
		/* dm_put_live_table must be before msleep, otherwise deadlock is possible */