ANDROID: dm-crypt: run in a WQ_HIGHPRI workqueue

(cherry pick from commit ad3ac5180979e5dd1f84e4a807f76fb9fb19f814)

Running dm-crypt in a standard workqueue results in IO competing for CPU
time with standard user apps, which can lead to pipeline bubbles and
seriously degraded performance. Move to a WQ_HIGHPRI workqueue to
protect against that.

Signed-off-by: Tim Murray <timmurray@google.com>
Bug: 25392275
Change-Id: I589149a31c7b5d322fe2ed5b2476b1f6e3d5ee6f

drivers/md/dm-crypt.c

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index c3235e0..acff4bb 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -1823,14 +1823,20 @@
 	}
 
 	ret = -ENOMEM;
-	cc->io_queue = alloc_workqueue("kcryptd_io", WQ_MEM_RECLAIM, 1);
+	cc->io_queue = alloc_workqueue("kcryptd_io",
+				       WQ_HIGHPRI |
+				       WQ_NON_REENTRANT|
+				       WQ_MEM_RECLAIM,
+				       1);
 	if (!cc->io_queue) {
 		ti->error = "Couldn't create kcryptd io queue";
 		goto bad;
 	}
 
 	cc->crypt_queue = alloc_workqueue("kcryptd",
-					  WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM, 1);
+					  WQ_HIGHPRI |
+					  WQ_MEM_RECLAIM |
+					  WQ_UNBOUND, num_online_cpus());
 	if (!cc->crypt_queue) {
 		ti->error = "Couldn't create kcryptd queue";
 		goto bad;