release/5.2.41/dm-report-suspended-device-during-destroy.patch

From 2f36baa4a8721f28acea8eff02510e5f84cdece8 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@redhat.com>
Date: Mon, 24 Feb 2020 10:20:28 +0100
Subject: [PATCH] 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: 48debafe4f2f ("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: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
index 5914ae5c4ba3..41d1c70b5b81 100644
--- a/drivers/md/dm-integrity.c
+++ b/drivers/md/dm-integrity.c
@@ -199,12 +199,13 @@ struct dm_integrity_c {
 	__u8 log2_blocks_per_bitmap_bit;
 
 	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;
@@ -2298,7 +2299,7 @@ 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);
@@ -2360,7 +2361,7 @@ 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);
@@ -2788,8 +2789,6 @@ 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);
 
@@ -2818,8 +2817,6 @@ static void dm_integrity_postsuspend(struct dm_target *ti)
 #endif
 	}
 
-	WRITE_ONCE(ic->suspending, 0);
-
 	BUG_ON(!RB_EMPTY_ROOT(&ic->in_progress));
 
 	ic->journal_uptodate = true;
@@ -3604,6 +3601,7 @@ 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);
diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index 90c3bf95b287..763848b6b259 100644
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -839,7 +839,7 @@ 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)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index f9a62e7eae47..14ca75ae68b5 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2390,6 +2390,7 @@ 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 */
-- 
2.7.4