OpenZFS restructuring - zvol

Refactor the zvol in to platform dependent and independent bits.

Reviewed-by: Allan Jude <allanjude@freebsd.org>
Reviewed-by: Jorgen Lundman <lundman@lundman.net>
Reviewed-by: Igor Kozhukhov <igor@dilos.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matt Macy <mmacy@FreeBSD.org>
Closes #9295

module/zfs/dmu_objset.c

@@ -2856,7 +2856,7 @@ dmu_objset_find_impl(spa_t *spa, const char *name,
  * See comment above dmu_objset_find_impl().
  */
 int
-dmu_objset_find(char *name, int func(const char *, void *), void *arg,
+dmu_objset_find(const char *name, int func(const char *, void *), void *arg,
     int flags)
 {
 	spa_t *spa;

module/zfs/zfs_ioctl.c

@@ -4136,7 +4136,7 @@ static int
 zfs_ioc_rollback(const char *fsname, nvlist_t *innvl, nvlist_t *outnvl)
 {
 	zfsvfs_t *zfsvfs;
-	zvol_state_t *zv;
+	zvol_state_handle_t *zv;
 	char *target = NULL;
 	int error;
 
@@ -4861,7 +4861,7 @@ zfs_ioc_recv_impl(char *tofs, char *tosnap, char *origin, nvlist_t *recvprops,
 
 	if (error == 0) {
 		zfsvfs_t *zfsvfs = NULL;
-		zvol_state_t *zv = NULL;
+		zvol_state_handle_t *zv = NULL;
 
 		if (getzfsvfs(tofs, &zfsvfs) == 0) {
 			/* online recv */
@@ -7671,7 +7671,7 @@ _init(void)
 {
 	int error;
 
-	if ((error = -zvol_init()) != 0)
+	if ((error = zvol_init()) != 0)
 		return (error);
 
 	spa_init(FREAD | FWRITE);