Add snapdev dataset property to control visibility of zvol snapshot d…

…evices

include/sys/fs/zfs.h

@@ -128,6 +128,7 @@ typedef enum {
 	ZFS_PROP_REFRATIO,
 	ZFS_PROP_WRITTEN,
 	ZFS_PROP_CLONES,
+	ZFS_PROP_SNAPDEV,
 	ZFS_NUM_PROPS
 } zfs_prop_t;
 

include/sys/zfs_ioctl.h

@@ -46,6 +46,12 @@ extern "C" {
 #define	ZFS_SNAPDIR_HIDDEN		0
 #define	ZFS_SNAPDIR_VISIBLE		1
 
+/*
+ * Property values for snapdev
+ */
+#define	ZFS_SNAPDEV_HIDDEN		0
+#define	ZFS_SNAPDEV_VISIBLE		1
+
 /*
  * Field manipulation macros for the drr_versioninfo field of the
  * send stream header.

include/sys/zvol.h

@@ -44,6 +44,7 @@ extern int zvol_remove_minor(const char *);
 extern void zvol_remove_minors(const char *);
 extern int zvol_set_volsize(const char *, uint64_t);
 extern int zvol_set_volblocksize(const char *, uint64_t);
+extern int zvol_set_snapdev(const char *, uint64_t);
 
 extern int zvol_init(void);
 extern void zvol_fini(void);

man/man8/zfs.8

@@ -1081,6 +1081,17 @@ When the \fBsharenfs\fR property is changed for a dataset, the dataset and any c
 Provide a hint to ZFS about handling of synchronous requests in this dataset. If \fBlogbias\fR is set to \fBlatency\fR (the default), ZFS will use pool log devices (if configured) to handle the requests at low latency. If \fBlogbias\fR is set to \fBthroughput\fR, ZFS will not use configured pool log devices. ZFS will instead optimize synchronous operations for global pool throughput and efficient use of resources.
 .RE
 
+.sp
+.ne 2
+.mk
+.na
+\fB\fBsnapdev\fR=\fBhidden\fR | \fBvisible\fR\fR
+.ad
+.sp .6
+.RS 4n
+Controls whether the snapshots devices of zvol's are hidden or visible. The default value is \fBhidden\fR.
+.RE
+
 .sp
 .ne 2
 .mk

module/zcommon/zfs_prop.c

@@ -106,6 +106,12 @@ zfs_prop_init(void)
 		{ NULL }
 	};
 
+	static zprop_index_t snapdev_table[] = {
+		{ "hidden",	ZFS_SNAPDEV_HIDDEN },
+		{ "visible",	ZFS_SNAPDEV_VISIBLE },
+		{ NULL }
+	};
+
 	static zprop_index_t acl_inherit_table[] = {
 		{ "discard",	ZFS_ACL_DISCARD },
 		{ "noallow",	ZFS_ACL_NOALLOW },
@@ -217,6 +223,9 @@ zfs_prop_init(void)
 	zprop_register_index(ZFS_PROP_SNAPDIR, "snapdir", ZFS_SNAPDIR_HIDDEN,
 	    PROP_INHERIT, ZFS_TYPE_FILESYSTEM,
 	    "hidden | visible", "SNAPDIR", snapdir_table);
+	zprop_register_index(ZFS_PROP_SNAPDEV, "snapdev", ZFS_SNAPDEV_HIDDEN,
+	    PROP_INHERIT, ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME,
+	    "hidden | visible", "SNAPDEV", snapdev_table);
 	zprop_register_index(ZFS_PROP_ACLINHERIT, "aclinherit",
 	    ZFS_ACL_RESTRICTED, PROP_INHERIT, ZFS_TYPE_FILESYSTEM,
 	    "discard | noallow | restricted | passthrough | passthrough-x",

module/zfs/zfs_ioctl.c

@@ -2184,6 +2184,9 @@ zfs_prop_set_special(const char *dsname, zprop_source_t source,
 	case ZFS_PROP_VOLSIZE:
 		err = zvol_set_volsize(dsname, intval);
 		break;
+	case ZFS_PROP_SNAPDEV:
+		err = zvol_set_snapdev(dsname, intval);
+		break;
 	case ZFS_PROP_VERSION:
 	{
 		zfs_sb_t *zsb;

module/zfs/zvol.c

@@ -1287,14 +1287,17 @@ zvol_free(zvol_state_t *zv)
 }
 
 static int
-__zvol_create_minor(const char *name)
+__zvol_create_minor(const char *name, int filter_snaps)
 {
 	zvol_state_t *zv;
 	objset_t *os;
 	dmu_object_info_t *doi;
 	uint64_t volsize;
+	uint64_t snapdev;
 	unsigned minor = 0;
 	int error = 0;
+	char *parent;
+	char *atp;
 
 	ASSERT(MUTEX_HELD(&zvol_state_lock));
 
@@ -1304,6 +1307,21 @@ __zvol_create_minor(const char *name)
 		goto out;
 	}
 
+	if (filter_snaps) {
+		parent = kmem_alloc(MAXPATHLEN, KM_SLEEP);
+		(void) strlcpy(parent, name, MAXPATHLEN);
+
+		if ((atp = strrchr(parent, '@')) != NULL) {
+			*atp = '\0';
+			if ((dsl_prop_get_integer(parent, "snapdev", &snapdev, NULL) == 0)
+				&& (snapdev == ZFS_SNAPDEV_HIDDEN)) {
+				kmem_free(parent, MAXPATHLEN);
+				return 0;
+			}
+		}
+		kmem_free(parent, MAXPATHLEN);
+	}
+
 	doi = kmem_alloc(sizeof(dmu_object_info_t), KM_SLEEP);
 
 	error = dmu_objset_own(name, DMU_OST_ZVOL, B_TRUE, zvol_tag, &os);
@@ -1383,7 +1401,7 @@ zvol_create_minor(const char *name)
 	int error;
 
 	mutex_enter(&zvol_state_lock);
-	error = __zvol_create_minor(name);
+	error = __zvol_create_minor(name, TRUE);
 	mutex_exit(&zvol_state_lock);
 
 	return (error);
@@ -1431,7 +1449,7 @@ zvol_create_minors_cb(spa_t *spa, uint64_t dsobj,
 	if (strchr(dsname, '/') == NULL)
 		return 0;
 
-	(void) __zvol_create_minor(dsname);
+	(void) __zvol_create_minor(dsname, TRUE);
 	return (0);
 }
 
@@ -1499,6 +1517,40 @@ zvol_remove_minors(const char *pool)
 	kmem_free(str, MAXNAMELEN);
 }
 
+static int
+snapdev_snapshot_changed_cb(const char *dsname, void *arg) {
+	uint64_t snapdev = *(uint64_t *) arg;
+
+	if (strchr(dsname, '@') == NULL) {
+		return 0;
+	}
+
+	switch (snapdev) {
+		case ZFS_SNAPDEV_VISIBLE:
+			mutex_enter(&zvol_state_lock);
+			(void) __zvol_create_minor(dsname, FALSE);
+			mutex_exit(&zvol_state_lock);
+			break;
+		case ZFS_SNAPDEV_HIDDEN:
+			(void) zvol_remove_minor(dsname);
+			break;
+	}
+	return 0;
+}
+
+int
+zvol_set_snapdev(const char *dsname, uint64_t snapdev) {
+	/* Inheritance and range checking should have been done by now */
+	ASSERT(snapdev == ZFS_SNAPDEV_HIDDEN || snapdev == ZFS_SNAPDEV_VISIBLE);
+
+	(void) dmu_objset_find((char *) dsname, snapdev_snapshot_changed_cb,
+		&snapdev, DS_FIND_SNAPSHOTS | DS_FIND_CHILDREN);
+	/* caller should continue to modify snapdev property */
+	return (-1);
+
+}
+
+
 int
 zvol_init(void)
 {