[PATCH 5.4 108/168] dm: report suspended device during destroy

Greg Kroah-Hartman
2020-03-10T12:53:10Z

From: Mikulas Patocka <mpatocka@redhat.com>

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/dm-integrity.c | 12 +++++-------
drivers/md/dm-writecache.c | 2 +-
drivers/md/dm.c | 1 +
3 files changed, 7 insertions(+), 8 deletions(-)

--- 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;
@@ -2311,7 +2312,7 @@ static void integrity_writer(struct work
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);
@@ -2372,7 +2373,7 @@ static void integrity_recalc(struct work

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);
@@ -2800,8 +2801,6 @@ static void dm_integrity_postsuspend(str

del_timer_sync(&ic->autocommit_timer);

- WRITE_ONCE(ic->suspending, 1);
-
if (ic->recalc_wq)
drain_workqueue(ic->recalc_wq);

@@ -2830,8 +2829,6 @@ static void dm_integrity_postsuspend(str
#endif
}

- WRITE_ONCE(ic->suspending, 0);
-
BUG_ON(!RB_EMPTY_ROOT(&ic->in_progress));

ic->journal_uptodate = true;
@@ -3615,6 +3612,7 @@ static int dm_integrity_ctr(struct dm_ta
}
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);
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -838,7 +838,7 @@ static void writecache_suspend(struct dm
}
wc_unlock(wc);

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

wc_lock(wc);
if (flush_on_suspend)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2389,6 +2389,7 @@ static void __dm_destroy(struct mapped_d
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 */