1 files changed, 51 insertions, 16 deletions

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 126ed21e6b17..357387fa10ca 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;
 }