Merge tag 'for-6.9/dm-bh-wq' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm

Pull device mapper BH workqueue conversion from Mike Snitzer:
 "Convert the DM verity and crypt targets from (ab)using tasklets to
  using BH workqueues.

  These changes were coordinated with Tejun and are based ontop of DM's
  6.9 changes and Tejun's 6.9 workqueue tree"

* tag 'for-6.9/dm-bh-wq' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
  dm-verity: Convert from tasklet to BH workqueue
  dm-crypt: Convert from tasklet to BH workqueue

1 files changed, 42 insertions, 22 deletions

diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 34f58630d7ea..bb5da66da4c1 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -46,7 +46,7 @@ static unsigned int dm_verity_prefetch_cluster = DM_VERITY_DEFAULT_PREFETCH_SIZE
 
 module_param_named(prefetch_cluster, dm_verity_prefetch_cluster, uint, 0644);
 
-static DEFINE_STATIC_KEY_FALSE(use_tasklet_enabled);
+static DEFINE_STATIC_KEY_FALSE(use_bh_wq_enabled);
 
 struct dm_verity_prefetch_work {
 	struct work_struct work;
@@ -299,7 +299,7 @@ static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io,
 
 	verity_hash_at_level(v, block, level, &hash_block, &offset);
 
-	if (static_branch_unlikely(&use_tasklet_enabled) && io->in_tasklet) {
+	if (static_branch_unlikely(&use_bh_wq_enabled) && io->in_bh) {
 		data = dm_bufio_get(v->bufio, hash_block, &buf);
 		if (data == NULL) {
 			/*
@@ -327,15 +327,14 @@ static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io,
 
 		r = verity_hash(v, verity_io_hash_req(v, io),
 				data, 1 << v->hash_dev_block_bits,
-				verity_io_real_digest(v, io), !io->in_tasklet);
+				verity_io_real_digest(v, io), !io->in_bh);
 		if (unlikely(r < 0))
 			goto release_ret_r;
 
 		if (likely(memcmp(verity_io_real_digest(v, io), want_digest,
 				  v->digest_size) == 0))
 			aux->hash_verified = 1;
-		else if (static_branch_unlikely(&use_tasklet_enabled) &&
-			 io->in_tasklet) {
+		else if (static_branch_unlikely(&use_bh_wq_enabled) && io->in_bh) {
 			/*
 			 * Error handling code (FEC included) cannot be run in a
 			 * tasklet since it may sleep, so fallback to work-queue.
@@ -576,7 +575,7 @@ static int verity_verify_io(struct dm_verity_io *io)
 	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
 	unsigned int b;
 
-	if (static_branch_unlikely(&use_tasklet_enabled) && io->in_tasklet) {
+	if (static_branch_unlikely(&use_bh_wq_enabled) && io->in_bh) {
 		/*
 		 * Copy the iterator in case we need to restart
 		 * verification in a work-queue.
@@ -616,7 +615,7 @@ static int verity_verify_io(struct dm_verity_io *io)
 			continue;
 		}
 
-		r = verity_hash_init(v, req, &wait, !io->in_tasklet);
+		r = verity_hash_init(v, req, &wait, !io->in_bh);
 		if (unlikely(r < 0))
 			return r;
 
@@ -635,8 +634,7 @@ static int verity_verify_io(struct dm_verity_io *io)
 			if (v->validated_blocks)
 				set_bit(cur_block, v->validated_blocks);
 			continue;
-		} else if (static_branch_unlikely(&use_tasklet_enabled) &&
-			   io->in_tasklet) {
+		} else if (static_branch_unlikely(&use_bh_wq_enabled) && io->in_bh) {
 			/*
 			 * Error handling code (FEC included) cannot be run in a
 			 * tasklet since it may sleep, so fallback to work-queue.
@@ -690,7 +688,7 @@ static void verity_finish_io(struct dm_verity_io *io, blk_status_t status)
 	bio->bi_end_io = io->orig_bi_end_io;
 	bio->bi_status = status;
 
-	if (!static_branch_unlikely(&use_tasklet_enabled) || !io->in_tasklet)
+	if (!static_branch_unlikely(&use_bh_wq_enabled) || !io->in_bh)
 		verity_fec_finish_io(io);
 
 	bio_endio(bio);
@@ -700,11 +698,28 @@ static void verity_work(struct work_struct *w)
 {
 	struct dm_verity_io *io = container_of(w, struct dm_verity_io, work);
 
-	io->in_tasklet = false;
+	io->in_bh = false;
 
 	verity_finish_io(io, errno_to_blk_status(verity_verify_io(io)));
 }
 
+static void verity_bh_work(struct work_struct *w)
+{
+	struct dm_verity_io *io = container_of(w, struct dm_verity_io, bh_work);
+	int err;
+
+	io->in_bh = 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;
@@ -717,8 +732,13 @@ 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_bh_wq_enabled) && io->v->use_bh_wq) {
+		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);
+	}
 }
 
 /*
@@ -885,7 +905,7 @@ static void verity_status(struct dm_target *ti, status_type_t type,
 			args++;
 		if (v->validated_blocks)
 			args++;
-		if (v->use_tasklet)
+		if (v->use_bh_wq)
 			args++;
 		if (v->signature_key_desc)
 			args += DM_VERITY_ROOT_HASH_VERIFICATION_OPTS;
@@ -912,7 +932,7 @@ static void verity_status(struct dm_target *ti, status_type_t type,
 			DMEMIT(" " DM_VERITY_OPT_IGN_ZEROES);
 		if (v->validated_blocks)
 			DMEMIT(" " DM_VERITY_OPT_AT_MOST_ONCE);
-		if (v->use_tasklet)
+		if (v->use_bh_wq)
 			DMEMIT(" " DM_VERITY_OPT_TASKLET_VERIFY);
 		sz = verity_fec_status_table(v, sz, result, maxlen);
 		if (v->signature_key_desc)
@@ -1031,8 +1051,8 @@ static void verity_dtr(struct dm_target *ti)
 
 	kfree(v->signature_key_desc);
 
-	if (v->use_tasklet)
-		static_branch_dec(&use_tasklet_enabled);
+	if (v->use_bh_wq)
+		static_branch_dec(&use_bh_wq_enabled);
 
 	kfree(v);
 
@@ -1166,8 +1186,8 @@ static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
 			continue;
 
 		} else if (!strcasecmp(arg_name, DM_VERITY_OPT_TASKLET_VERIFY)) {
-			v->use_tasklet = true;
-			static_branch_inc(&use_tasklet_enabled);
+			v->use_bh_wq = true;
+			static_branch_inc(&use_bh_wq_enabled);
 			continue;
 
 		} else if (verity_is_fec_opt_arg(arg_name)) {
@@ -1338,7 +1358,7 @@ static int verity_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	}
 
 	v->tfm = crypto_alloc_ahash(v->alg_name, 0,
-				    v->use_tasklet ? CRYPTO_ALG_ASYNC : 0);
+				    v->use_bh_wq ? CRYPTO_ALG_ASYNC : 0);
 	if (IS_ERR(v->tfm)) {
 		ti->error = "Cannot initialize hash function";
 		r = PTR_ERR(v->tfm);
@@ -1463,7 +1483,7 @@ static int verity_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	v->bufio = dm_bufio_client_create(v->hash_dev->bdev,
 		1 << v->hash_dev_block_bits, 1, sizeof(struct buffer_aux),
 		dm_bufio_alloc_callback, NULL,
-		v->use_tasklet ? DM_BUFIO_CLIENT_NO_SLEEP : 0);
+		v->use_bh_wq ? DM_BUFIO_CLIENT_NO_SLEEP : 0);
 	if (IS_ERR(v->bufio)) {
 		ti->error = "Cannot initialize dm-bufio";
 		r = PTR_ERR(v->bufio);
@@ -1482,7 +1502,7 @@ static int verity_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	 * reducing wait times when reading from a dm-verity device.
 	 *
 	 * Also as required for the "try_verify_in_tasklet" feature: WQ_HIGHPRI
-	 * allows verify_wq to preempt softirq since verification in tasklet
+	 * allows verify_wq to preempt softirq since verification in BH workqueue
 	 * will fall-back to using it for error handling (or if the bufio cache
 	 * doesn't have required hashes).
 	 */