dm crypt: use unbound workqueue for request processing

Use unbound workqueue by default so that work is automatically balanced
between available CPUs.  The original behavior of encrypting using the
same cpu that IO was submitted on can still be enabled by setting the
optional 'same_cpu_crypt' table argument.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

Documentation/device-mapper/dm-crypt.txt

@@ -51,7 +51,7 @@ Parameters: <cipher> <key> <iv_offset> <device path> \
     Otherwise #opt_params is the number of following arguments.
 
     Example of optional parameters section:
-        1 allow_discards
+        2 allow_discards same_cpu_crypt
 
 allow_discards
     Block discard requests (a.k.a. TRIM) are passed through the crypt device.
@@ -63,6 +63,11 @@ allow_discards
     used space etc.) if the discarded blocks can be located easily on the
     device later.
 
+same_cpu_crypt
+    Perform encryption using the same cpu that IO was submitted on.
+    The default is to use an unbound workqueue so that encryption work
+    is automatically balanced between available CPUs.
+
 Example scripts
 ===============
 LUKS (Linux Unified Key Setup) is now the preferred way to set up disk

drivers/md/dm-crypt.c

@@ -108,7 +108,7 @@ struct iv_tcw_private {
  * Crypt: maps a linear range of a block device
  * and encrypts / decrypts at the same time.
  */
-enum flags { DM_CRYPT_SUSPENDED, DM_CRYPT_KEY_VALID };
+enum flags { DM_CRYPT_SUSPENDED, DM_CRYPT_KEY_VALID, DM_CRYPT_SAME_CPU };
 
 /*
  * The fields in here must be read only after initialization.
@@ -1688,7 +1688,7 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	char dummy;
 
 	static struct dm_arg _args[] = {
-		{0, 1, "Invalid number of feature args"},
+		{0, 2, "Invalid number of feature args"},
 	};
 
 	if (argc < 5) {
@@ -1788,15 +1788,23 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 		if (ret)
 			goto bad;
 
-		opt_string = dm_shift_arg(&as);
+		while (opt_params--) {
+			opt_string = dm_shift_arg(&as);
+			if (!opt_string) {
+				ti->error = "Not enough feature arguments";
+				goto bad;
+			}
 
-		if (opt_params == 1 && opt_string &&
-		    !strcasecmp(opt_string, "allow_discards"))
-			ti->num_discard_bios = 1;
-		else if (opt_params) {
-			ret = -EINVAL;
-			ti->error = "Invalid feature arguments";
-			goto bad;
+			if (!strcasecmp(opt_string, "allow_discards"))
+				ti->num_discard_bios = 1;
+
+			else if (!strcasecmp(opt_string, "same_cpu_crypt"))
+				set_bit(DM_CRYPT_SAME_CPU, &cc->flags);
+
+			else {
+				ti->error = "Invalid feature arguments";
+				goto bad;
+			}
 		}
 	}
 
@@ -1807,8 +1815,11 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 		goto bad;
 	}
 
-	cc->crypt_queue = alloc_workqueue("kcryptd",
-					  WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM, 1);
+	if (test_bit(DM_CRYPT_SAME_CPU, &cc->flags))
+		cc->crypt_queue = alloc_workqueue("kcryptd", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM, 1);
+	else
+		cc->crypt_queue = alloc_workqueue("kcryptd", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | WQ_UNBOUND,
+						  num_online_cpus());
 	if (!cc->crypt_queue) {
 		ti->error = "Couldn't create kcryptd queue";
 		goto bad;
@@ -1860,6 +1871,7 @@ static void crypt_status(struct dm_target *ti, status_type_t type,
 {
 	struct crypt_config *cc = ti->private;
 	unsigned i, sz = 0;
+	int num_feature_args = 0;
 
 	switch (type) {
 	case STATUSTYPE_INFO:
@@ -1878,8 +1890,15 @@ static void crypt_status(struct dm_target *ti, status_type_t type,
 		DMEMIT(" %llu %s %llu", (unsigned long long)cc->iv_offset,
 				cc->dev->name, (unsigned long long)cc->start);
 
-		if (ti->num_discard_bios)
-			DMEMIT(" 1 allow_discards");
+		num_feature_args += !!ti->num_discard_bios;
+		num_feature_args += test_bit(DM_CRYPT_SAME_CPU, &cc->flags);
+		if (num_feature_args) {
+			DMEMIT(" %d", num_feature_args);
+			if (ti->num_discard_bios)
+				DMEMIT(" allow_discards");
+			if (test_bit(DM_CRYPT_SAME_CPU, &cc->flags))
+				DMEMIT(" same_cpu_crypt");
+		}
 
 		break;
 	}
@@ -1976,7 +1995,7 @@ static int crypt_iterate_devices(struct dm_target *ti,
 
 static struct target_type crypt_target = {
 	.name   = "crypt",
-	.version = {1, 13, 0},
+	.version = {1, 14, 0},
 	.module = THIS_MODULE,
 	.ctr    = crypt_ctr,
 	.dtr    = crypt_dtr,