[PATCH 6.6] Revert "dm-crypt, dm-verity: disable tasklets"

[Li Lingfeng]

This reverts commit 5735a2671ffb70ea29ca83969fe01316ee2ed6fc which is
commit 0a9bab391e336489169b95cb0d4553d921302189 upstream.

Tasklet is thought to cause memory corruption [1], so it was disabled in
dm-crypt and dm-verity. However, memory corruption may not happen since
cc->io_queue is created without WQ_UNBOUND [2].
Revert commit 5735a2671ffb ("dm-crypt, dm-verity: disable tasklets") to
bring tasklet back.

[1] https://lore.kernel.org/all/d390d7ee-f142-44d3-822a-87949e14608b@xxxxxxx/T/
[2] https://lore.kernel.org/all/4d331659-badd-749d-fba1-271543631a8a@xxxxxxxxxx/

Signed-off-by: Li Lingfeng <lilingfeng3@xxxxxxxxxx>
---
 drivers/md/dm-crypt.c         | 38 +++++++++++++++++++++++++++++++++--
 drivers/md/dm-verity-target.c | 26 ++++++++++++++++++++++--
 drivers/md/dm-verity.h        |  1 +
 3 files changed, 61 insertions(+), 4 deletions(-)

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index aa6bb5b4704b..a60d91d02e28 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -75,8 +75,10 @@ struct dm_crypt_io {
 	struct bio *base_bio;
 	u8 *integrity_metadata;
 	bool integrity_metadata_from_pool:1;
+	bool in_tasklet:1;
 
 	struct work_struct work;
+	struct tasklet_struct tasklet;
 
 	struct convert_context ctx;
 
@@ -1775,6 +1777,7 @@ static void crypt_io_init(struct dm_crypt_io *io, struct crypt_config *cc,
 	io->ctx.r.req = NULL;
 	io->integrity_metadata = NULL;
 	io->integrity_metadata_from_pool = false;
+	io->in_tasklet = false;
 	atomic_set(&io->io_pending, 0);
 }
 
@@ -1785,6 +1788,13 @@ static void crypt_inc_pending(struct dm_crypt_io *io)
 
 static void kcryptd_queue_read(struct dm_crypt_io *io);
 
+static void kcryptd_io_bio_endio(struct work_struct *work)
+{
+	struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work);
+
+	bio_endio(io->base_bio);
+}
+
 /*
  * One of the bios was finished. Check for completion of
  * the whole request and correctly clean up the buffer.
@@ -1817,6 +1827,20 @@ static void crypt_dec_pending(struct dm_crypt_io *io)
 
 	base_bio->bi_status = error;
 
+	/*
+	 * If we are running this function from our tasklet,
+	 * we can't call bio_endio() here, because it will call
+	 * clone_endio() from dm.c, which in turn will
+	 * free the current struct dm_crypt_io structure with
+	 * our tasklet. In this case we need to delay bio_endio()
+	 * execution to after the tasklet is done and dequeued.
+	 */
+	if (io->in_tasklet) {
+		INIT_WORK(&io->work, kcryptd_io_bio_endio);
+		queue_work(cc->io_queue, &io->work);
+		return;
+	}
+
 	bio_endio(base_bio);
 }
 
@@ -2291,6 +2315,11 @@ static void kcryptd_crypt(struct work_struct *work)
 		kcryptd_crypt_write_convert(io);
 }
 
+static void kcryptd_crypt_tasklet(unsigned long work)
+{
+	kcryptd_crypt((struct work_struct *)work);
+}
+
 static void kcryptd_queue_crypt(struct dm_crypt_io *io)
 {
 	struct crypt_config *cc = io->cc;
@@ -2302,10 +2331,15 @@ static void kcryptd_queue_crypt(struct dm_crypt_io *io)
 		 * irqs_disabled(): the kernel may run some IO completion from the idle thread, but
 		 * it is being executed with irqs disabled.
 		 */
-		if (!(in_hardirq() || irqs_disabled())) {
-			kcryptd_crypt(&io->work);
+		if (in_hardirq() || irqs_disabled()) {
+			io->in_tasklet = true;
+			tasklet_init(&io->tasklet, kcryptd_crypt_tasklet, (unsigned long)&io->work);
+			tasklet_schedule(&io->tasklet);
 			return;
 		}
+
+		kcryptd_crypt(&io->work);
+		return;
 	}
 
 	INIT_WORK(&io->work, kcryptd_crypt);
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 49e4a35d7019..0bb126eadc0d 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -701,6 +701,23 @@ 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)
+{
+	struct dm_verity_io *io = (struct dm_verity_io *)data;
+	int err;
+
+	io->in_tasklet = true;
+	err = verity_verify_io(io);
+	if (err == -EAGAIN || err == -ENOMEM) {
+		/* fallback to retrying with work-queue */
+		INIT_WORK(&io->work, verity_work);
+		queue_work(io->v->verify_wq, &io->work);
+		return;
+	}
+
+	verity_finish_io(io, errno_to_blk_status(err));
+}
+
 static void verity_end_io(struct bio *bio)
 {
 	struct dm_verity_io *io = bio->bi_private;
@@ -713,8 +730,13 @@ static void verity_end_io(struct bio *bio)
 		return;
 	}
 
-	INIT_WORK(&io->work, verity_work);
-	queue_work(io->v->verify_wq, &io->work);
+	if (static_branch_unlikely(&use_tasklet_enabled) && io->v->use_tasklet) {
+		tasklet_init(&io->tasklet, verity_tasklet, (unsigned long)io);
+		tasklet_schedule(&io->tasklet);
+	} 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 db93a91169d5..7e495cc375b0 100644
--- a/drivers/md/dm-verity.h
+++ b/drivers/md/dm-verity.h
@@ -87,6 +87,7 @@ struct dm_verity_io {
 	bool in_tasklet;
 
 	struct work_struct work;
+	struct tasklet_struct tasklet;
 
 	char *recheck_buffer;
 
-- 
2.31.1