[PATCH 8/8] dm-verity: Convert from tasklet to BH workqueue

[Tejun Heo]

The only generic interface to execute asynchronously in the BH context is
tasklet; however, it's marked deprecated and has some design flaws. To
replace tasklets, BH workqueue support was recently added. A BH workqueue
behaves similarly to regular workqueues except that the queued work items
are executed in the BH context.

This patch converts dm-verity from tasklet to BH workqueue.

This is a minimal conversion which doesn't rename the related names
including the "try_verify_in_tasklet" option. If this patch is applied, a
follow-up patch would be necessary. I couldn't decide whether the option
name would need to be updated too.

Only compile tested. I don't know how to verity.

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Alasdair Kergon <agk@xxxxxxxxxx>
Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
Cc: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Cc: dm-devel@xxxxxxxxxxxxxxx
---
 drivers/md/dm-verity-target.c | 8 ++++----
 drivers/md/dm-verity.h        | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 14e58ae70521..911261de2d08 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -645,9 +645,9 @@ static void verity_work(struct work_struct *w)
 	verity_finish_io(io, errno_to_blk_status(verity_verify_io(io)));
 }
 
-static void verity_tasklet(unsigned long data)
+static void verity_bh_work(struct work_struct *w)
 {
-	struct dm_verity_io *io = (struct dm_verity_io *)data;
+	struct dm_verity_io *io = container_of(w, struct dm_verity_io, bh_work);
 	int err;
 
 	io->in_tasklet = true;
@@ -675,8 +675,8 @@ static void verity_end_io(struct bio *bio)
 	}
 
 	if (static_branch_unlikely(&use_tasklet_enabled) && io->v->use_tasklet) {
-		tasklet_init(&io->tasklet, verity_tasklet, (unsigned long)io);
-		tasklet_schedule(&io->tasklet);
+		INIT_WORK(&io->bh_work, verity_bh_work);
+		queue_work(system_bh_wq, &io->bh_work);
 	} else {
 		INIT_WORK(&io->work, verity_work);
 		queue_work(io->v->verify_wq, &io->work);
diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h
index f9d522c870e6..7c16f834f31a 100644
--- a/drivers/md/dm-verity.h
+++ b/drivers/md/dm-verity.h
@@ -83,7 +83,7 @@ struct dm_verity_io {
 	struct bvec_iter iter;
 
 	struct work_struct work;
-	struct tasklet_struct tasklet;
+	struct work_struct bh_work;
 
 	/*
 	 * Three variably-size fields follow this struct:
-- 
2.43.0