1 files changed, 51 insertions, 16 deletions

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 126ed21..357387f 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -36,7 +36,6 @@ struct dm_crypt_io {
 	struct work_struct work;
 	atomic_t pending;
 	int error;
-	int post_process;
 };
 
 /*
@@ -80,7 +79,8 @@ struct crypt_config {
 	mempool_t *page_pool;
 	struct bio_set *bs;
 
-	struct workqueue_struct *queue;
+	struct workqueue_struct *io_queue;
+	struct workqueue_struct *crypt_queue;
 	/*
 	 * crypto related data
 	 */
@@ -476,19 +476,36 @@ static void dec_pending(struct dm_crypt_io *io, int error)
 }
 
 /*
- * kcryptd:
+ * kcryptd/kcryptd_io:
  *
  * Needed because it would be very unwise to do decryption in an
  * interrupt context.
+ *
+ * kcryptd performs the actual encryption or decryption.
+ *
+ * kcryptd_io performs the IO submission.
+ *
+ * They must be separated as otherwise the final stages could be
+ * starved by new requests which can block in the first stages due
+ * to memory allocation.
  */
 static void kcryptd_do_work(struct work_struct *work);
+static void kcryptd_do_crypt(struct work_struct *work);
 
 static void kcryptd_queue_io(struct dm_crypt_io *io)
 {
 	struct crypt_config *cc = io->target->private;
 
 	INIT_WORK(&io->work, kcryptd_do_work);
-	queue_work(cc->queue, &io->work);
+	queue_work(cc->io_queue, &io->work);
+}
+
+static void kcryptd_queue_crypt(struct dm_crypt_io *io)
+{
+	struct crypt_config *cc = io->target->private;
+
+	INIT_WORK(&io->work, kcryptd_do_crypt);
+	queue_work(cc->crypt_queue, &io->work);
 }
 
 static void crypt_endio(struct bio *clone, int error)
@@ -511,8 +528,7 @@ static void crypt_endio(struct bio *clone, int error)
 	}
 
 	bio_put(clone);
-	io->post_process = 1;
-	kcryptd_queue_io(io);
+	kcryptd_queue_crypt(io);
 	return;
 
 out:
@@ -634,10 +650,16 @@ static void kcryptd_do_work(struct work_struct *work)
 {
 	struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work);
 
-	if (io->post_process)
-		process_read_endio(io);
-	else if (bio_data_dir(io->base_bio) == READ)
+	if (bio_data_dir(io->base_bio) == READ)
 		process_read(io);
+}
+
+static void kcryptd_do_crypt(struct work_struct *work)
+{
+	struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work);
+
+	if (bio_data_dir(io->base_bio) == READ)
+		process_read_endio(io);
 	else
 		process_write(io);
 }
@@ -870,16 +892,24 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	} else
 		cc->iv_mode = NULL;
 
-	cc->queue = create_singlethread_workqueue("kcryptd");
-	if (!cc->queue) {
+	cc->io_queue = create_singlethread_workqueue("kcryptd_io");
+	if (!cc->io_queue) {
+		ti->error = "Couldn't create kcryptd io queue";
+		goto bad_io_queue;
+	}
+
+	cc->crypt_queue = create_singlethread_workqueue("kcryptd");
+	if (!cc->crypt_queue) {
 		ti->error = "Couldn't create kcryptd queue";
-		goto bad_queue;
+		goto bad_crypt_queue;
 	}
 
 	ti->private = cc;
 	return 0;
 
-bad_queue:
+bad_crypt_queue:
+	destroy_workqueue(cc->io_queue);
+bad_io_queue:
 	kfree(cc->iv_mode);
 bad_iv_mode:
 	dm_put_device(ti, cc->dev);
@@ -905,7 +935,8 @@ static void crypt_dtr(struct dm_target *ti)
 {
 	struct crypt_config *cc = (struct crypt_config *) ti->private;
 
-	destroy_workqueue(cc->queue);
+	destroy_workqueue(cc->io_queue);
+	destroy_workqueue(cc->crypt_queue);
 
 	bioset_free(cc->bs);
 	mempool_destroy(cc->page_pool);
@@ -931,9 +962,13 @@ static int crypt_map(struct dm_target *ti, struct bio *bio,
 	io = mempool_alloc(cc->io_pool, GFP_NOIO);
 	io->target = ti;
 	io->base_bio = bio;
-	io->error = io->post_process = 0;
+	io->error = 0;
 	atomic_set(&io->pending, 0);
-	kcryptd_queue_io(io);
+
+	if (bio_data_dir(io->base_bio) == READ)
+		kcryptd_queue_io(io);
+	else
+		kcryptd_queue_crypt(io);
 
 	return DM_MAPIO_SUBMITTED;
 }