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 @@ -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 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
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(str
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(str 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_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 @@ -844,7 +844,7 @@ 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 @@ -2353,6 +2353,7 @@ 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 */