Add the "btrfs filesystem label" command

Hi all,

this patch adds the command "btrfs filesystem label" to change (or show) the
label of a filesystem.
This patch is a subset of the one written previously by Morey Roof. I
included the user space part only. So it is possible only to change/show a
label of a *single device* and *unounted* filesystem.

The reason of excluding the kernel space part, is to simplify the patch in
order to speed the check and then the merging of the patch itself. In fact I
have to point out that in the past there was almost three attempts to propose
this patch, without success neither complaints.

Chris, let me know how you want to proceed. I know that you are very busy,
and you prefer to work to stabilize btrfs instead adding new feature. But I
think that changing a label is a *essential* feature for a filesystem
managing tool. Think about a mount by LABEL.

To show a label

$ btrfs filesystem label <device>

To set a label

$ btrfs filesystem label <device> <newlabel>

Please guys, give a look to the source.
Comments are welcome.

You can pull the source from the branch "label" of the repository
http://cassiopea.homelinux.net/git/btrfs-progs-unstable.git

Regards
G.Baroncelli

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 57 insertions, 0 deletions

diff --git a/utils.c b/utils.c
index ad980aed..13373c99 100644
--- a/utils.c
+++ b/utils.c
@@ -812,6 +812,39 @@ out_mntloop_err:
 	return ret;
 }
 
+/* Gets the mount point of btrfs filesystem that is using the specified device.
+ * Returns 0 is everything is good, <0 if we have an error.
+ * TODO: Fix this fucntion and check_mounted to work with multiple drive BTRFS
+ * setups.
+ */
+int get_mountpt(char *dev, char *mntpt, size_t size)
+{
+       struct mntent *mnt;
+       FILE *f;
+       int ret = 0;
+
+       f = setmntent("/proc/mounts", "r");
+       if (f == NULL)
+               return -errno;
+
+       while ((mnt = getmntent(f)) != NULL )
+       {
+               if (strcmp(dev, mnt->mnt_fsname) == 0)
+               {
+                       strncpy(mntpt, mnt->mnt_dir, size);
+                       break;
+               }
+       }
+
+       if (mnt == NULL)
+       {
+               /* We didn't find an entry so lets report an error */
+               ret = -1;
+       }
+
+       return ret;
+}
+
 struct pending_dir {
 	struct list_head list;
 	char name[256];
@@ -1002,3 +1035,27 @@ char *pretty_sizes(u64 size)
 	return pretty;
 }
 
+/*
+ * Checks to make sure that the label matches our requirements.
+ * Returns:
+       0    if everything is safe and usable
+      -1    if the label is too long
+      -2    if the label contains an invalid character
+ */
+int check_label(char *input)
+{
+       int i;
+       int len = strlen(input);
+
+       if (len > BTRFS_LABEL_SIZE) {
+               return -1;
+       }
+
+       for (i = 0; i < len; i++) {
+               if (input[i] == '/' || input[i] == '\\') {
+                       return -2;
+               }
+       }
+
+       return 0;
+}