[PATCH 1/2 v4] Btrfs-progs: add feature to label subvol and snapshot

[Anand Jain <anand.jain@oracle.com>]

btrfs-progs framework to add support to label the subvol and
snapshots. This patch is for the ioctl-way to write label
to the subvol and snapshot. (the other way is to use attribute
if then only this patch has to be backed out in btrfs-progs
and replace with the patch titled
 Btrfs-progs: add attribute label for subvol and snapshot)

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 btrfslabel.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
 btrfslabel.h |  4 +++-
 ctree.h      |  4 +++-
 ioctl.h      |  2 ++
 print-tree.c |  2 ++
 5 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/btrfslabel.c b/btrfslabel.c
index a421a8b..b3ad540 100644
--- a/btrfslabel.c
+++ b/btrfslabel.c
@@ -126,3 +126,48 @@ int set_label(char *btrfs_dev, char *nLabel)
 	}
 	return change_label_unmounted(btrfs_dev, nLabel);
 }
+
+int get_subvol_label(char *subvol, char *labelp)
+{
+	int fd, e=0;
+
+	fd = open_file_or_dir(subvol);
+
+	if(ioctl(fd, BTRFS_IOC_SUBVOL_GETLABEL, labelp) < 0) {
+		e = errno;
+		fprintf(stderr, "ERROR: get subvol label failed, %s\n",
+			strerror(e));
+		close(fd);
+		return -e;
+	}
+	labelp[BTRFS_LABEL_SIZE] = '\0';
+	if (!strlen(labelp))
+		return -1;
+	close(fd);
+	return 0;
+}
+
+int set_subvol_label(char *subvol, char *labelp)
+{
+	int fd, e=0;
+	char label[BTRFS_SUBVOL_LABEL_SIZE+1];
+
+	if (strlen(labelp) > BTRFS_SUBVOL_LABEL_SIZE) {
+		fprintf(stderr, "ERROR: Subvol label is more than max length %d\n",
+			BTRFS_SUBVOL_LABEL_SIZE);
+		return -1;
+	}
+	memset(label, 0, BTRFS_SUBVOL_LABEL_SIZE+1);
+	strcpy(label, labelp);
+	fd = open_file_or_dir(subvol);
+
+	if(ioctl(fd, BTRFS_IOC_SUBVOL_SETLABEL, label) < 0) {
+		e = errno;
+		fprintf(stderr, "ERROR: set subvol label failed, %s\n",
+			strerror(e));
+		close(fd);
+		return -e;
+	}
+	close(fd);
+	return 0;
+}
diff --git a/btrfslabel.h b/btrfslabel.h
index abf43ad..1abc483 100644
--- a/btrfslabel.h
+++ b/btrfslabel.h
@@ -2,4 +2,6 @@
 
 
 int get_label(char *btrfs_dev);
-int set_label(char *btrfs_dev, char *nLabel);
\ No newline at end of file
+int set_label(char *btrfs_dev, char *nLabel);
+int get_subvol_label(char *subvol, char *labelp);
+int set_subvol_label(char *subvol, char *labelp);
diff --git a/ctree.h b/ctree.h
index 12f8fe3..bacb7d1 100644
--- a/ctree.h
+++ b/ctree.h
@@ -332,6 +332,7 @@ struct btrfs_header {
  */
 #define BTRFS_SYSTEM_CHUNK_ARRAY_SIZE 2048
 #define BTRFS_LABEL_SIZE 256
+#define BTRFS_SUBVOL_LABEL_SIZE 32
 
 /*
  * just in case we somehow lose the roots and are not able to mount,
@@ -721,7 +722,8 @@ struct btrfs_root_item {
 	struct btrfs_timespec otime;
 	struct btrfs_timespec stime;
 	struct btrfs_timespec rtime;
-        __le64 reserved[8]; /* for future */
+	char label[BTRFS_SUBVOL_LABEL_SIZE];
+        __le64 reserved[4]; /* for future */
 } __attribute__ ((__packed__));
 
 /*
diff --git a/ioctl.h b/ioctl.h
index 3e7e451..4cbae3a 100644
--- a/ioctl.h
+++ b/ioctl.h
@@ -524,6 +524,8 @@ struct btrfs_ioctl_clone_range_args {
 				      struct btrfs_ioctl_get_dev_stats)
 #define BTRFS_IOC_DEV_REPLACE _IOWR(BTRFS_IOCTL_MAGIC, 53, \
 				    struct btrfs_ioctl_dev_replace_args)
+#define BTRFS_IOC_SUBVOL_GETLABEL _IOWR(BTRFS_IOCTL_MAGIC, 55, __u64)
+#define BTRFS_IOC_SUBVOL_SETLABEL _IOW(BTRFS_IOCTL_MAGIC, 56, __u64)
 
 #ifdef __cplusplus
 }
diff --git a/print-tree.c b/print-tree.c
index c9e891b..3d097dd 100644
--- a/print-tree.c
+++ b/print-tree.c
@@ -366,6 +366,8 @@ static void print_root(struct extent_buffer *leaf, int slot)
 				btrfs_root_stransid(&root_item),
 				btrfs_root_rtransid(&root_item));
 		}
+		if (strlen(root_item.label))
+			printf("\t\tlabel %s\n", root_item.label);
 	}
 	if (btrfs_root_refs(&root_item) == 0) {
 		struct btrfs_key drop_key;
-- 
1.8.1.227.g44fe835