Btrfs-progs: Change the label of a mounted file system

With this new ioctl(2), we can set/change the label for a mounted file system.
It still does normal process for an umounted file system.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>

diff --git a/btrfslabel.c b/btrfslabel.c
index a421a8b..7aea996 100644 (file)
--- a/btrfslabel.c
+++ b/btrfslabel.c
@@ -46,26 +46,58 @@
 #define GET_LABEL                      3
 #define SET_LABEL                      4
 
-static int change_label_unmounted(char *dev, char *nLabel)
+static int set_label_unmounted(const char *dev, const char *label)
 {
-       struct btrfs_root *root;
-       struct btrfs_trans_handle *trans;
+       struct btrfs_trans_handle *trans;
+       struct btrfs_root *root;
+       int ret;
 
-       /* Open the super_block at the default location
-        * and as read-write.
-        */
-       root = open_ctree(dev, 0, 1);
-       if (!root) /* errors are printed by open_ctree() */
+       ret = check_mounted(dev);
+       if (ret < 0) {
+              fprintf(stderr, "FATAL: error checking %s mount status\n", dev);
               return -1;
+       }
+       if (ret > 0) {
+               fprintf(stderr, "ERROR: dev %s is mounted, use mount point\n",
+                       dev);
+               return -1;
+       }
 
-       trans = btrfs_start_transaction(root, 1);
-       strncpy(root->fs_info->super_copy.label, nLabel, BTRFS_LABEL_SIZE);
-       root->fs_info->super_copy.label[BTRFS_LABEL_SIZE-1] = 0;
-       btrfs_commit_transaction(trans, root);
+       /* Open the super_block at the default location
+        * and as read-write.
+        */
+       root = open_ctree(dev, 0, 1);
+       if (!root) /* errors are printed by open_ctree() */
+               return -1;
+
+       trans = btrfs_start_transaction(root, 1);
+       strncpy(root->fs_info->super_copy.label, label, BTRFS_LABEL_SIZE);
+       root->fs_info->super_copy.label[BTRFS_LABEL_SIZE-1] = 0;
+       btrfs_commit_transaction(trans, root);
+
+       /* Now we close it since we are done. */
+       close_ctree(root);
+       return 0;
+}
 
-       /* Now we close it since we are done. */
-       close_ctree(root);
-       return 0;
+static int set_label_mounted(const char *mount_path, const char *label)
+{
+       int fd;
+
+       fd = open(mount_path, O_RDONLY | O_NOATIME);
+       if (fd < 0) {
+               fprintf(stderr, "ERROR: unable access to '%s'\n", mount_path);
+               return -1;
+       }
+
+       if (ioctl(fd, BTRFS_IOC_SET_FSLABEL, label) < 0) {
+               fprintf(stderr, "ERROR: unable to set label %s\n",
+                       strerror(errno));
+               close(fd);
+               return -1;
+       }
+
+       return 0;
 }
 
 int get_label_unmounted(char *dev)
@@ -108,21 +140,9 @@ int get_label(char *btrfs_dev)
 }
 
 
-int set_label(char *btrfs_dev, char *nLabel)
+int set_label(char *btrfs_dev, char *label)
 {
-
-       int ret;
-       ret = check_mounted(btrfs_dev);
-       if (ret < 0)
-       {
-              fprintf(stderr, "FATAL: error checking %s mount status\n", btrfs_dev);
-              return -1;
-       }
-
-       if(ret != 0)
-       {
-              fprintf(stderr, "FATAL: the filesystem has to be unmounted\n");
-              return -2;
-       }
-       return change_label_unmounted(btrfs_dev, nLabel);
+       return is_existing_blk_or_reg_file(btrfs_dev) ?
+               set_label_unmounted(btrfs_dev, label) :
+               set_label_mounted(btrfs_dev, label);
 }

diff --git a/ioctl.h b/ioctl.h
index 3e7e451..e841913 100644 (file)
--- a/ioctl.h
+++ b/ioctl.h
@@ -520,6 +520,10 @@ struct btrfs_ioctl_clone_range_args {
                                        struct btrfs_ioctl_qgroup_create_args)
 #define BTRFS_IOC_QGROUP_LIMIT _IOR(BTRFS_IOCTL_MAGIC, 43, \
                                        struct btrfs_ioctl_qgroup_limit_args)
+#define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 49, \
+                                  char[BTRFS_LABEL_SIZE])
+#define BTRFS_IOC_SET_FSLABEL _IOW(BTRFS_IOCTL_MAGIC, 50, \
+                                  char[BTRFS_LABEL_SIZE])
 #define BTRFS_IOC_GET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 52, \
                                      struct btrfs_ioctl_get_dev_stats)
 #define BTRFS_IOC_DEV_REPLACE _IOWR(BTRFS_IOCTL_MAGIC, 53, \