Add snapdev=[hidden|visible] dataset property

The new snapdev dataset property may be set to control the
visibility of zvol snapshot devices.  By default this value
is set to 'hidden' which will prevent zvol snapshots from
appearing under /dev/zvol/ and /dev/<dataset>/.  When set to
'visible' all zvol snapshots for the dataset will be visible.

This functionality was largely added because when automatic
snapshoting is enabled large numbers of read-only zvol snapshots
will be created.  When creating these devices the kernel will
attempt to read their partition tables, and blkid will attempt
to identify any filesystems on those partitions.  This leads
to a variety of issues:

1) The zvol partition tables will be read in the context of
   the `modprobe zfs` for automatically imported pools.  This
   is undesirable and should be done asynchronously, but for
   now reducing the number of visible devices helps.

2) Udev expects to be able to complete its work for a new
   block devices fairly quickly.  When many zvol devices are
   added at the same time this is no longer be true.  It can
   lead to udev timeouts and missing /dev/zvol links.

3) Simply having lots of devices in /dev/ can be aukward from
   a management standpoint.  Hidding the devices your unlikely
   to ever use helps with this.  Any snapshot device which is
   needed can be made visible by changing the snapdev property.

NOTE: This patch changes the default behavior for zvols which
      was effectively 'snapdev=visible'.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1235
Closes #945
Issue #956
Issue #756

diff --git a/include/sys/fs/zfs.h b/include/sys/fs/zfs.h
index 137dd39e6a3612730d4517c5b827868e2e023377..8c949e7671a02843114d6de9b9cd5b9257ee8c04 100644 (file)
--- a/include/sys/fs/zfs.h
+++ b/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;
 

diff --git a/include/sys/zfs_ioctl.h b/include/sys/zfs_ioctl.h
index 4e5c5fba299d162c9a1df3bda1f5c4f26af55e42..740d8eda4e670f19b73c53decacf81d6d1b133ff 100644 (file)
--- a/include/sys/zfs_ioctl.h
+++ b/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.

diff --git a/include/sys/zvol.h b/include/sys/zvol.h
index 185d645231c5a8defbcaddd1a17e023aa791a829..c05f81a5ff54fd4c8466fd5661afb1d4dd1b3a76 100644 (file)
--- a/include/sys/zvol.h
+++ b/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);

diff --git a/lib/libzfs/libzfs_dataset.c b/lib/libzfs/libzfs_dataset.c
index 73d45882a5b2b3accca8c38eda736addbb9f0f17..d4691dd2a178b0ea9de10b4682ff624ce22b6e75 100644 (file)
--- a/lib/libzfs/libzfs_dataset.c
+++ b/lib/libzfs/libzfs_dataset.c
@@ -4016,6 +4016,14 @@ zvol_create_link_common(libzfs_handle_t *hdl, const char *dataset, int ifexists)
                         */
                        return (0);
 
+               case ENODEV:
+                       /*
+                        * snapdev set to hidden :
+                        *  device creation was not permitted (see zvol.c)
+                        *  ignore error quietly
+                        */
+                       return (0);
+
                case ENOENT:
                        /*
                         * Dataset does not exist in the kernel.  If we

diff --git a/man/man8/zfs.8 b/man/man8/zfs.8
index edfd5e797fd2ffc5b60b3499bacd14259a68988c..6f648f7ae4cd4876b93a2d4f2e43cd15dbe2e4d1 100644 (file)
--- a/man/man8/zfs.8
+++ b/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

diff --git a/module/zcommon/zfs_prop.c b/module/zcommon/zfs_prop.c
index 6aa38382b2f4caf9c194ae5ed4c12cbffcb47893..b27e4f36f391afca364a3c0521fc4cb2a64b1376 100644 (file)
--- a/module/zcommon/zfs_prop.c
+++ b/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",

diff --git a/module/zfs/zfs_ioctl.c b/module/zfs/zfs_ioctl.c
index e804cce085a7ad228818279d2fdce3038d2e8e2a..5560b2548f344bb051fbb4d479c55fcb7df04228 100644 (file)
--- a/module/zfs/zfs_ioctl.c
+++ b/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;

diff --git a/module/zfs/zvol.c b/module/zfs/zvol.c
index b0d59fe0c7aa6b0be507f7c2cee2f10dc219d8ba..b41eeb20221d5b37db898a72f80cb1ef23431bcb 100644 (file)
--- a/module/zfs/zvol.c
+++ b/module/zfs/zvol.c
@@ -1288,7 +1288,28 @@ zvol_free(zvol_state_t *zv)
 }
 
 static int
-__zvol_create_minor(const char *name)
+__zvol_snapdev_hidden(const char *name)
+{
+        uint64_t snapdev;
+        char *parent;
+        char *atp;
+        int error = 0;
+
+        parent = kmem_alloc(MAXPATHLEN, KM_SLEEP);
+        (void) strlcpy(parent, name, MAXPATHLEN);
+
+        if ((atp = strrchr(parent, '@')) != NULL) {
+                *atp = '\0';
+                error = dsl_prop_get_integer(parent, "snapdev", &snapdev, NULL);
+                if ((error == 0) && (snapdev == ZFS_SNAPDEV_HIDDEN))
+                        error = ENODEV;
+        }
+        kmem_free(parent, MAXPATHLEN);
+        return (error);
+}
+
+static int
+__zvol_create_minor(const char *name, boolean_t ignore_snapdev)
 {
        zvol_state_t *zv;
        objset_t *os;
@@ -1305,6 +1326,12 @@ __zvol_create_minor(const char *name)
                goto out;
        }
 
+       if (ignore_snapdev == B_FALSE) {
+               error = __zvol_snapdev_hidden(name);
+               if (error)
+                       goto out;
+       }
+
        doi = kmem_alloc(sizeof(dmu_object_info_t), KM_SLEEP);
 
        error = dmu_objset_own(name, DMU_OST_ZVOL, B_TRUE, zvol_tag, &os);
@@ -1386,7 +1413,7 @@ zvol_create_minor(const char *name)
        int error;
 
        mutex_enter(&zvol_state_lock);
-       error = __zvol_create_minor(name);
+       error = __zvol_create_minor(name, B_FALSE);
        mutex_exit(&zvol_state_lock);
 
        return (error);
@@ -1434,7 +1461,7 @@ 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, B_FALSE);
        return (0);
 }
 
@@ -1502,6 +1529,35 @@ 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, B_TRUE);
+                       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) {
+       (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)
 {

diff --git a/scripts/zconfig.sh b/scripts/zconfig.sh
index 83a6fac2246659e88fa5c16acc30a139415d9025..141348c037faf47f66317e04382441299d8c5840 100755 (executable)
--- a/scripts/zconfig.sh
+++ b/scripts/zconfig.sh
@@ -192,6 +192,7 @@ test_3() {
        ${ZFS_SH} zfs="spa_config_path=${TMP_CACHE}" || fail 1
        ${ZPOOL_CREATE_SH} -p ${POOL_NAME} -c lo-raidz2 || fail 2
        ${ZFS} create -V 100M ${FULL_ZVOL_NAME} || fail 3
+       ${ZFS} set snapdev=visible ${FULL_ZVOL_NAME} || fail 3
        label /dev/zvol/${FULL_ZVOL_NAME} msdos || fail 4
        partition /dev/zvol/${FULL_ZVOL_NAME} primary 1% 50% || fail 4
        partition /dev/zvol/${FULL_ZVOL_NAME} primary 51% -1 || fail 4
@@ -245,6 +246,7 @@ test_4() {
        ${ZFS_SH} zfs="spa_config_path=${TMP_CACHE}" || fail 1
        ${ZPOOL_CREATE_SH} -p ${POOL_NAME} -c lo-raidz2 || fail 2
        ${ZFS} create -V 100M ${FULL_ZVOL_NAME} || fail 3
+       ${ZFS} set snapdev=visible ${FULL_ZVOL_NAME} || fail 3
        label /dev/zvol/${FULL_ZVOL_NAME} msdos || fail 4
        partition /dev/zvol/${FULL_ZVOL_NAME} primary 1% 50% || fail 4
        partition /dev/zvol/${FULL_ZVOL_NAME} primary 51% -1 || fail 4
@@ -335,6 +337,7 @@ test_6() {
        ${ZFS_SH} zfs="spa_config_path=${TMP_CACHE}" || fail 1
        ${ZPOOL_CREATE_SH} -p ${POOL_NAME} -c lo-raid0 || fail 2
        ${ZFS} create -V 800M ${FULL_ZVOL_NAME} || fail 3
+       ${ZFS} set snapdev=visible ${FULL_ZVOL_NAME} || fail 3
        label /dev/zvol/${FULL_ZVOL_NAME} msdos || fail 4
        partition /dev/zvol/${FULL_ZVOL_NAME} primary 1 -1 || fail 4
        format /dev/zvol/${FULL_ZVOL_NAME}-part1 ext2 || fail 5
@@ -394,6 +397,7 @@ test_7() {
        ${ZFS_SH} zfs="spa_config_path=${TMP_CACHE}" || fail 1
        ${ZPOOL_CREATE_SH} -p ${POOL_NAME} -c lo-raidz2 || fail 2
        ${ZFS} create -V 300M ${FULL_ZVOL_NAME} || fail 3
+       ${ZFS} set snapdev=visible ${FULL_ZVOL_NAME} || fail 3
        label /dev/zvol/${FULL_ZVOL_NAME} msdos || fail 4
        partition /dev/zvol/${FULL_ZVOL_NAME} primary 1 -1 || fail 4
        format /dev/zvol/${FULL_ZVOL_NAME}-part1 ext2 || fail 5
@@ -481,6 +485,7 @@ test_8() {
        ${ZPOOL_CREATE_SH} -p ${POOL_NAME1} -c lo-raidz2 || fail 2
        ${ZPOOL_CREATE_SH} -p ${POOL_NAME2} -c lo-raidz2 || fail 2
        ${ZFS} create -V 300M ${FULL_ZVOL_NAME1} || fail 3
+       ${ZFS} set snapdev=visible ${FULL_ZVOL_NAME1} || fail 3
        label /dev/zvol/${FULL_ZVOL_NAME1} msdos || fail 4
        partition /dev/zvol/${FULL_ZVOL_NAME1} primary 1 -1 || fail 4
        format /dev/zvol/${FULL_ZVOL_NAME1}-part1 ext2 || fail 5