Btrfs-progs: introduce btrfs property subgroup

"btrfs filesystem property" is a generic interface to set/get
properties on filesystem objects (inodes/subvolumes/filesystems
/devs).

This patch adds the generic framework for properties and also
implements two properties. The first is the read-only property
for subvolumes and the second is the label property for devices.

Signed-off-by: Alexander Block <ablock84@googlemail.com>
Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 110 insertions, 0 deletions

diff --git a/props.c b/props.c
new file mode 100644
index 00000000..763fd57e
--- /dev/null
+++ b/props.c
@@ -0,0 +1,110 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include <sys/stat.h>
+#include <sys/ioctl.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "ctree.h"
+#include "commands.h"
+#include "utils.h"
+#include "props.h"
+
+static int prop_read_only(enum prop_object_type type,
+			  const char *object,
+			  const char *name,
+			  const char *value)
+{
+	int ret = 0;
+	int fd = -1;
+	u64 flags = 0;
+
+	fd = open(object, O_RDONLY);
+	if (fd < 0) {
+		ret = -errno;
+		fprintf(stderr, "ERROR: open %s failed. %s\n",
+				object, strerror(-ret));
+		goto out;
+	}
+
+	ret = ioctl(fd, BTRFS_IOC_SUBVOL_GETFLAGS, &flags);
+	if (ret < 0) {
+		ret = -errno;
+		fprintf(stderr, "ERROR: failed to get flags for %s. %s\n",
+				object, strerror(-ret));
+		goto out;
+	}
+
+	if (!value) {
+		if (flags & BTRFS_SUBVOL_RDONLY)
+			fprintf(stdout, "ro=true\n");
+		else
+			fprintf(stdout, "ro=false\n");
+		ret = 0;
+		goto out;
+	}
+
+	if (!strcmp(value, "true")) {
+		flags |= BTRFS_SUBVOL_RDONLY;
+	} else if (!strcmp(value, "false")) {
+		flags = flags & ~BTRFS_SUBVOL_RDONLY;
+	} else {
+		ret = -EINVAL;
+		fprintf(stderr, "ERROR: invalid value for property.\n");
+		goto out;
+	}
+
+	ret = ioctl(fd, BTRFS_IOC_SUBVOL_SETFLAGS, &flags);
+	if (ret < 0) {
+		ret = -errno;
+		fprintf(stderr, "ERROR: failed to set flags for %s. %s\n",
+				object, strerror(-ret));
+		goto out;
+	}
+
+out:
+	if (fd != -1)
+		close(fd);
+	return ret;
+}
+
+static int prop_label(enum prop_object_type type,
+		      const char *object,
+		      const char *name,
+		      const char *value)
+{
+	int ret;
+
+	if (value) {
+		ret = set_label((char *) object, (char *) value);
+	} else {
+		char label[BTRFS_LABEL_SIZE];
+
+		ret = get_label((char *) object, label);
+		if (!ret)
+			fprintf(stdout, "label=%s\n", label);
+	}
+
+	return ret;
+}
+
+const struct prop_handler prop_handlers[] = {
+	{"ro", "Set/get read-only flag of subvolume.", 0, prop_object_subvol,
+	 prop_read_only},
+	{"label", "Set/get label of device.", 0, prop_object_dev, prop_label},
+	{0, 0, 0, 0, 0}
+};