snapshot: Issue with other processes accessing the mounted brick

Added code for unmount of activated snapshot brick during snapshot
deactivation process which make sense as mount point for deactivated
bricks should not exist.

Removed code for mounting newly created snapshot, as newly created
snapshots should not mount until it is activated.

Added code for mount point creation and snapshot mount during snapshot
activation.

Added validation during glusterd init for mounting only those snapshot
whose status is either STARTED or RESTORED.

During snapshot restore, mount point for stopped snap should exist as
it is required to set extended attribute.

During handshake, after getting updates from friend mount point for
activated snapshot should exist and should not for deactivated
snapshot.

While getting snap status we should show relevent information for
deactivated snapshots, after this pathch 'gluster snap status' command
will show output like-

Snap Name : snap1
Snap UUID : snap-uuid

	Brick Path        :   server1:/run/gluster/snaps/snap-vol-name/brick
	Volume Group      :   N/A (Deactivated Snapshot)
	Brick Running     :   No
	Brick PID         :   N/A
	Data Percentage   :   N/A
	LV Size           :   N/A

Fixes: #276

Change-Id: I65783488e35fac43632615ce1b8ff7b8e84834dc
BUG: 1482023
Signed-off-by: Sunny Kumar <sunkumar@redhat.com>

1 files changed, 85 insertions, 0 deletions

diff --git a/xlators/mgmt/glusterd/src/glusterd-snapshot-utils.c b/xlators/mgmt/glusterd/src/glusterd-snapshot-utils.c
index 38fea9dbaa4..f1a2bbb4c35 100644
--- a/xlators/mgmt/glusterd/src/glusterd-snapshot-utils.c
+++ b/xlators/mgmt/glusterd/src/glusterd-snapshot-utils.c
@@ -1678,10 +1678,31 @@ glusterd_import_friend_snap (dict_t *peer_data, int32_t snap_count,
                                 "for snap %s", peer_snap_name);
                         goto out;
                 }
+                /* During handshake, after getting updates from friend mount
+                 * point for activated snapshot should exist and should not
+                 * for deactivated snapshot.
+                 */
                 if (glusterd_is_volume_started (snap_vol)) {
+                        ret = glusterd_recreate_vol_brick_mounts (this,
+                                                                  snap_vol);
+                        if (ret) {
+                                gf_msg (this->name, GF_LOG_ERROR, 0,
+                                        GD_MSG_BRK_MNT_RECREATE_FAIL,
+                                        "Failed to recreate brick mounts"
+                                        " for %s", snap->snapname);
+                                goto out;
+                        }
+
                         (void) glusterd_start_bricks (snap_vol);
                 } else {
                         (void) glusterd_stop_bricks(snap_vol);
+                        ret = glusterd_snap_unmount(this, snap_vol);
+                        if (ret) {
+                                gf_msg (this->name, GF_LOG_ERROR, 0,
+                                        GD_MSG_GLUSTERD_UMOUNT_FAIL,
+                                        "Failed to unmounts for %s",
+                                        snap->snapname);
+                        }
                 }
 
                 ret = glusterd_import_quota_conf (peer_data, i,
@@ -3337,6 +3358,70 @@ out:
         return ret;
 }
 
+/* This function will do unmount for snaps.
+ */
+int32_t
+glusterd_snap_unmount (xlator_t  *this, glusterd_volinfo_t *volinfo)
+{
+        char                    *brick_mount_path    = NULL;
+        glusterd_brickinfo_t    *brickinfo           = NULL;
+        int32_t                  ret                 = -1;
+        int                      retry_count         = 0;
+
+        GF_ASSERT (this);
+        GF_ASSERT (volinfo);
+
+        cds_list_for_each_entry (brickinfo, &volinfo->bricks, brick_list) {
+                /* If the brick is not of this node, we continue */
+                if (gf_uuid_compare (brickinfo->uuid, MY_UUID)) {
+                        continue;
+                }
+                /* If snapshot is pending, we continue */
+                if  (brickinfo->snap_status == -1) {
+                        continue;
+                }
+
+                /* Fetch the brick mount path from the brickinfo->path */
+                ret = glusterd_get_brick_root (brickinfo->path,
+                                               &brick_mount_path);
+                if (ret) {
+                        gf_msg (this->name, GF_LOG_INFO, 0,
+                                GD_MSG_BRICK_PATH_UNMOUNTED,
+                                "Failed to find brick_mount_path for %s",
+                                brickinfo->path);
+                        /* There is chance that brick path is already
+                         * unmounted. */
+                        ret = 0;
+                        goto out;
+                }
+                /* unmount cannot be done when the brick process is still in
+                 * the process of shutdown, so give three re-tries
+                 */
+                retry_count = 0;
+                while (retry_count <= 2) {
+                        retry_count++;
+                        /* umount2 system call doesn't cleanup mtab entry
+                         * after un-mount, using external umount command.
+                         */
+                        ret = glusterd_umount(brick_mount_path);
+                        if (!ret)
+                                break;
+                        gf_msg (this->name, GF_LOG_ERROR, 0,
+                                GD_MSG_GLUSTERD_UMOUNT_FAIL, "umount failed "
+                                "for path %s (brick: %s): %s. Retry(%d)",
+                                 brick_mount_path, brickinfo->path,
+                                 strerror (errno), retry_count);
+                        sleep (3);
+               }
+        }
+
+out:
+        if (brick_mount_path)
+                GF_FREE(brick_mount_path);
+
+        return ret;
+}
+
 int32_t
 glusterd_umount (const char *path)
 {