Hi Anand,
please updates the man page, because it says that it is impossible to
change the label of a mounted filesystem
[...]
btrfs filesystem label <dev> [newlabel]
Show or update the label of a filesystem. <dev> is used to iden‐
tify the filesystem. If a newlabel optional argument is passed,
the label is changed. The following costraints exist for a
label:
- the maximum allowable lenght shall be less or equal than 256
chars
- the label shall not contain the '/' or '\' characters.
NOTE: Currently there are the following limitations:
- the filesystem has to be unmounted
- the filesystem should not have more than one device.
[...]
Thanks
G.Baroncelli
On 08/29/2012 10:46 AM, Anand jain wrote:
From: Anand Jain<anand.j...@oracle.com>
Signed-off-by: Anand Jain<anand.j...@oracle.com>
---
btrfslabel.c | 90 ++++++++++++++++++++++++++++++++++++++--------------------
ioctl.h | 2 +
utils.h | 1 +
3 files changed, 62 insertions(+), 31 deletions(-)
diff --git a/btrfslabel.c b/btrfslabel.c
index bf73802..3676db0 100644
--- a/btrfslabel.c
+++ b/btrfslabel.c
@@ -51,6 +51,10 @@ static void change_label_unmounted(char *dev, char *nLabel)
struct btrfs_root *root;
struct btrfs_trans_handle *trans;
+ if(check_mounted(dev)) {
+ fprintf(stderr, "ERROR: dev is mounted, use mount point\n");
+ return;
+ }
/* Open the super_block at the default location
* and as read-write.
*/
@@ -67,10 +71,57 @@ static void change_label_unmounted(char *dev, char *nLabel)
close_ctree(root);
}
+static void set_fs_label(char *mnt, char *label)
+{
+ int fd, e=0;
+ char fslabel[BTRFS_LABEL_SIZE+1];
+
+ memset(fslabel, 0, BTRFS_LABEL_SIZE+1);
+ strncpy(fslabel,label,BTRFS_LABEL_SIZE);
+
+ fd = open(mnt, O_RDONLY| O_NOATIME);
+ if (fd< 0) {
+ fprintf(stderr, "ERROR: Open %s failed\n", mnt);
+ return;
+ }
+
+ if(ioctl(fd, BTRFS_IOC_SET_LABEL, fslabel)< 0) {
+ e = errno;
+ fprintf(stderr, "ERROR: get label failed, %s\n",
+ strerror(e));
+ }
+ close(fd);
+}
+
+static void get_fs_label(char *path)
+{
+ int fd, e=0;
+ char label[BTRFS_LABEL_SIZE+1];
+
+ fd = open(path, O_RDONLY| O_NOATIME);
+ if (fd< 0) {
+ fprintf(stderr, "ERROR: Open %s failed\n", path);
+ return;
+ }
+
+ if(ioctl(fd, BTRFS_IOC_GET_LABEL, label)< 0) {
+ e = errno;
+ fprintf(stderr, "ERROR: get label failed, %s\n",
+ strerror(e));
+ return;
+ }
+ printf("%s\n",label);
+ close(fd);
+}
+
static void get_label_unmounted(char *dev)
{
struct btrfs_root *root;
+ if(check_mounted(dev)) {
+ fprintf(stderr, "ERROR: dev is mounted, use mount point\n");
+ return;
+ }
/* Open the super_block at the default location
* and as read-only.
*/
@@ -84,41 +135,18 @@ static void get_label_unmounted(char *dev)
int get_label(char *btrfs_dev)
{
-
- 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;
- }
- get_label_unmounted(btrfs_dev);
+ if(is_existing_blk_or_reg_file(btrfs_dev))
+ get_label_unmounted(btrfs_dev);
+ else
+ get_fs_label(btrfs_dev);
return 0;
}
-
int set_label(char *btrfs_dev, char *nLabel)
{
-
- 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;
- }
- change_label_unmounted(btrfs_dev, nLabel);
+ if(is_existing_blk_or_reg_file(btrfs_dev))
+ change_label_unmounted(btrfs_dev, nLabel);
+ else
+ set_fs_label(btrfs_dev, nLabel);
return 0;
}
diff --git a/ioctl.h b/ioctl.h
index d6f3d07..7e1dcda 100644
--- a/ioctl.h
+++ b/ioctl.h
@@ -370,4 +370,6 @@ struct btrfs_ioctl_clone_range_args {
struct btrfs_ioctl_received_subvol_args)
#define BTRFS_IOC_SEND _IOW(BTRFS_IOCTL_MAGIC, 38, struct
btrfs_ioctl_send_args)
+#define BTRFS_IOC_GET_LABEL _IOR(BTRFS_IOCTL_MAGIC, 53, __u64)
+#define BTRFS_IOC_SET_LABEL _IOW(BTRFS_IOCTL_MAGIC, 54, __u64)
#endif
diff --git a/utils.h b/utils.h
index c147c12..ba088fe 100644
--- a/utils.h
+++ b/utils.h
@@ -48,4 +48,5 @@ int check_label(char *input);
int get_mountpt(char *dev, char *mntpt, size_t size);
int btrfs_scan_block_devices(int run_ioctl);
+int is_existing_blk_or_reg_file(const char* filename);
#endif
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