[RFC PATCHv2 0/3] Btrfs-progs: introduce btrfs property subgroup

[RFC PATCHv2 0/3] Btrfs-progs: introduce btrfs property subgroup

[Alexander Block]

This patchset introduces the btrfs property subgroup. It is the
result of a discussion we had on IRC. I tried to make the properties
interface as generic and extensible as possible. Comments are welcome.

Currently the command group looks like this:
btrfs prop set [-t <type>] /path/to/object <name> <value>
btrfs prop get [-t <type>] /path/to/object [<name>] (omitting name dumps all)
btrfs prop list [-t <type>] /path/to/object (lists properties with description)

The type is used to explicitly specify what type of object you mean. This is 
necessary in case the object+property combination is ambiguous.  For example
'/path/to/fs/root' could mean the root subvolume, the directory inode or the 
filesystem itself. Normally, btrfs-progs will try to detect the type 
automatically.

David suggested that it should also be possible to specify objects by
their id/uuid/fsid. I like that idea, but would be happy if someone else
could take over that part :)

For now, I've implemented two properties:
1. read-only. Usable on subvolumes to toggle the read-only flags.
2. label. I looked through btrfs to find good examples of things that
   could be moved to the new properties interface and the filesystem
   label looked like a good one. There are for sure more, but that is
   something for later (and maybe for someone else). I would suggest 
   to move everthing that makes sense over to the props interface and 
   mark the old interfaces as deprecated. Comments on this are welcome.

Patch version history:
v1
  Initial version.
v2
  - Removed the filesystem prefix and implemented it as new command group
  - Switched from the <name>[=<value>] form to the set/get <name> [<value>] 
    form.
  - Removed patches "Btrfs-progs: make filesystem_cmd_group non const"
    and "Btrfs-progs: move skip_prefix and prefixcmp to utils.c". They
    are not needed anymore due to the 'btrfs prop list' command.
  - Udjusted the subvol flags patch to be compatible to the "Btrfs: use 
    _IOR for BTRFS_IOC_SUBVOL_GETFLAGS" patch.
  - Using -t <type> instead of <type>: prefix now.
  - Changes are based on feedback from Ilya and David.

Alex.

Alexander Block (3):
  Btrfs-progs: add BTRFS_IOC_SUBVOL_GET/SETFLAGS to ioctl.h
  Btrfs-progs: let get_label return the label instead of of printing it
  Btrfs-progs: introduce btrfs property subgroup

 Makefile          |    5 +-
 btrfs.c           |    1 +
 btrfslabel.c      |   13 +-
 btrfslabel.h      |    4 +-
 cmds-filesystem.c |   14 +-
 cmds-property.c   |  459 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 commands.h        |    2 +
 ioctl.h           |    2 +
 props.c           |  114 +++++++++++++
 props.h           |   43 +++++
 10 files changed, 645 insertions(+), 12 deletions(-)
 create mode 100644 cmds-property.c
 create mode 100644 props.c
 create mode 100644 props.h

-- 
1.7.10

[RFC PATCHv2 1/3] Btrfs-progs: add BTRFS_IOC_SUBVOL_GET/SETFLAGS to ioctl.h

[Alexander Block]

Btrfs send/receive and btrfs props needs this ioctl. This patch
requires a recent kernel with the "Btrfs: use _IOR for
BTRFS_IOC_SUBVOL_GETFLAGS" patch applied.

Signed-off-by: Alexander Block <ablock84@googlemail.com>
---
 ioctl.h |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/ioctl.h b/ioctl.h
index f2e5d8d..6670e08 100644
--- a/ioctl.h
+++ b/ioctl.h
@@ -312,6 +312,8 @@ struct btrfs_ioctl_logical_ino_args {
 				    struct btrfs_ioctl_space_args)
 #define BTRFS_IOC_SNAP_CREATE_V2 _IOW(BTRFS_IOCTL_MAGIC, 23, \
 				   struct btrfs_ioctl_vol_args_v2)
+#define BTRFS_IOC_SUBVOL_GETFLAGS _IOR(BTRFS_IOCTL_MAGIC, 25, __u64)
+#define BTRFS_IOC_SUBVOL_SETFLAGS _IOW(BTRFS_IOCTL_MAGIC, 26, __u64)
 #define BTRFS_IOC_SCRUB _IOWR(BTRFS_IOCTL_MAGIC, 27, \
 				struct btrfs_ioctl_scrub_args)
 #define BTRFS_IOC_SCRUB_CANCEL _IO(BTRFS_IOCTL_MAGIC, 28)
-- 
1.7.10

[RFC PATCHv2 2/3] Btrfs-progs: let get_label return the label instead of of printing it

[Alexander Block]

get_label prints the label at the moment. Change this so that
the label is returned and printing is done by the caller.

Also bail out when open_ctree failed to avoid a crash when btrfs fi
label is called on a device with no btrfs on it.

Signed-off-by: Alexander Block <ablock84@googlemail.com>
---
 btrfslabel.c      |   13 ++++++++-----
 btrfslabel.h      |    4 ++--
 cmds-filesystem.c |   14 +++++++++++---
 3 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/btrfslabel.c b/btrfslabel.c
index bf73802..59cad82 100644
--- a/btrfslabel.c
+++ b/btrfslabel.c
@@ -67,7 +67,7 @@ static void change_label_unmounted(char *dev, char *nLabel)
        close_ctree(root);
 }
 
-static void get_label_unmounted(char *dev)
+static int get_label_unmounted(char *dev, char **label)
 {
        struct btrfs_root *root;
 
@@ -75,14 +75,18 @@ static void get_label_unmounted(char *dev)
         * and as read-only.
         */
        root = open_ctree(dev, 0, 0);
+       if (!root)
+	       return -1;
 
-       fprintf(stdout, "%s\n", root->fs_info->super_copy.label);
+       *label = strdup(root->fs_info->super_copy.label);
 
        /* Now we close it since we are done. */
        close_ctree(root);
+
+       return 0;
 }
 
-int get_label(char *btrfs_dev)
+int get_label(char *btrfs_dev, char **label)
 {
 
 	int ret;
@@ -98,8 +102,7 @@ int get_label(char *btrfs_dev)
 	       fprintf(stderr, "FATAL: the filesystem has to be unmounted\n");
 	       return -2;
 	}
-	get_label_unmounted(btrfs_dev);
-	return 0;
+	return get_label_unmounted(btrfs_dev, label);
 }
 
 
diff --git a/btrfslabel.h b/btrfslabel.h
index abf43ad..ce6765b 100644
--- a/btrfslabel.h
+++ b/btrfslabel.h
@@ -1,5 +1,5 @@
 /* btrflabel.h */
 
 
-int get_label(char *btrfs_dev);
-int set_label(char *btrfs_dev, char *nLabel);
\ No newline at end of file
+int get_label(char *btrfs_dev, char **label);
+int set_label(char *btrfs_dev, char *nLabel);
diff --git a/cmds-filesystem.c b/cmds-filesystem.c
index b1457de..c5289e3 100644
--- a/cmds-filesystem.c
+++ b/cmds-filesystem.c
@@ -518,13 +518,21 @@ static const char * const cmd_label_usage[] = {
 
 static int cmd_label(int argc, char **argv)
 {
+	int ret;
+	char *label;
 	if (check_argc_min(argc, 2) || check_argc_max(argc, 3))
 		usage(cmd_label_usage);
 
-	if (argc > 2)
+	if (argc > 2) {
 		return set_label(argv[1], argv[2]);
-	else
-		return get_label(argv[1]);
+	} else {
+		ret = get_label(argv[1], &label);
+		if (ret < 0)
+			return ret;
+		fprintf(stdout, "%s\n", label);
+		free(label);
+		return ret;
+	}
 }
 
 const struct cmd_group filesystem_cmd_group = {
-- 
1.7.10

[RFC PATCHv2 3/3] Btrfs-progs: introduce btrfs property subgroup

[Alexander Block]

"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>
---
 Makefile        |    5 +-
 btrfs.c         |    1 +
 cmds-property.c |  459 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 commands.h      |    2 +
 props.c         |  114 ++++++++++++++
 props.h         |   43 ++++++
 6 files changed, 622 insertions(+), 2 deletions(-)
 create mode 100644 cmds-property.c
 create mode 100644 props.c
 create mode 100644 props.h

diff --git a/Makefile b/Makefile
index 9694444..b67c368 100644
--- a/Makefile
+++ b/Makefile
@@ -4,9 +4,10 @@ CFLAGS = -g -O0
 objects = ctree.o disk-io.o radix-tree.o extent-tree.o print-tree.o \
 	  root-tree.o dir-item.o file-item.o inode-item.o \
 	  inode-map.o crc32c.o rbtree.o extent-cache.o extent_io.o \
-	  volumes.o utils.o btrfs-list.o btrfslabel.o repair.o
+	  volumes.o utils.o btrfs-list.o btrfslabel.o repair.o \
+	  props.o
 cmds_objects = cmds-subvolume.o cmds-filesystem.o cmds-device.o cmds-scrub.o \
-	       cmds-inspect.o cmds-balance.o
+	       cmds-inspect.o cmds-balance.o cmds-property.o
 
 CHECKFLAGS= -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ -Wbitwise \
 	    -Wuninitialized -Wshadow -Wundef
diff --git a/btrfs.c b/btrfs.c
index 88238d6..0c8dde3 100644
--- a/btrfs.c
+++ b/btrfs.c
@@ -246,6 +246,7 @@ const struct cmd_group btrfs_cmd_group = {
 		{ "device", cmd_device, NULL, &device_cmd_group, 0 },
 		{ "scrub", cmd_scrub, NULL, &scrub_cmd_group, 0 },
 		{ "inspect-internal", cmd_inspect, NULL, &inspect_cmd_group, 0 },
+		{ "property", cmd_property, NULL, &property_cmd_group, 0 },
 		{ "help", cmd_help, cmd_help_usage, NULL, 0 },
 		{ "version", cmd_version, cmd_version_usage, NULL, 0 },
 		{ 0, 0, 0, 0, 0 }
diff --git a/cmds-property.c b/cmds-property.c
new file mode 100644
index 0000000..04c7b1e
--- /dev/null
+++ b/cmds-property.c
@@ -0,0 +1,459 @@
+/*
+ * 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 <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+
+#include "commands.h"
+#include "props.h"
+#include "ctree.h"
+
+static const char * const property_cmd_group_usage[] = {
+	"btrfs property get/set/list [-t <type>] <object> [<name>] [value]",
+	NULL
+};
+
+static const char * const cmd_get_usage[] = {
+	"btrfs property get [-t <type>] <object> [<name>]",
+	"Gets a property from a btrfs object.",
+	"If no name is specified, all properties for the given object are",
+	"printed.",
+	"A filesystem object can be a the filesystem itself, a subvolume,",
+	"an inode or a device. The '-t <type>' option can be used to explicitly",
+	"specify what type of object you meant. This is only needed when a",
+	"property could be set for more then one object type. Possible types",
+	"are s[ubvol], f[ilesystem], i[node] and d[evice].",
+	NULL
+};
+
+static const char * const cmd_set_usage[] = {
+	"btrfs property set [-t <type>] <object> <name> <value>",
+	"Sets a property on a btrfs object.",
+	"Please see the help of 'btrfs property get' for a description of",
+	"objects and object types.",
+	NULL
+};
+
+static const char * const cmd_list_usage[] = {
+	"btrfs property list [-t <type>] <object>",
+	"Lists available properties with their descriptions for the given object.",
+	"Please see the help of 'btrfs property get' for a description of",
+	"objects and object types.",
+	NULL
+};
+
+static int parse_prop(const char *arg, const struct prop_handler *props,
+		      const struct prop_handler **prop_ret)
+{
+	const struct prop_handler *prop = props;
+
+	for (; prop->name; prop++) {
+		if (!strcmp(prop->name, arg)) {
+			*prop_ret = prop;
+			return 0;
+		}
+	}
+
+	return -1;
+}
+
+static int get_fsid(const char *path, u8 *fsid)
+{
+	int ret;
+	int fd;
+	struct btrfs_ioctl_fs_info_args args;
+
+	fd = open(path, O_RDONLY);
+	if (fd < 0) {
+		ret = -errno;
+		fprintf(stderr, "ERROR: open %s failed. %s\n", path,
+				strerror(-ret));
+		goto out;
+	}
+
+	ret = ioctl(fd, BTRFS_IOC_FS_INFO, &args);
+	if (ret < 0) {
+		ret = -errno;
+		goto out;
+	}
+
+	memcpy(fsid, args.fsid, BTRFS_FSID_SIZE);
+	ret = 0;
+
+out:
+	if (fd != -1)
+		close(fd);
+	return ret;
+}
+
+static int check_btrfs_object(const char *object)
+{
+	int ret;
+	u8 fsid[BTRFS_FSID_SIZE];
+
+	ret = get_fsid(object, fsid);
+	if (ret < 0)
+		ret = 0;
+	else
+		ret = 1;
+	return ret;
+}
+
+static int check_is_root(const char *object)
+{
+	int ret;
+	u8 fsid[BTRFS_FSID_SIZE];
+	u8 fsid2[BTRFS_FSID_SIZE];
+	char *tmp;
+
+	tmp = malloc(strlen(object) + 5);
+	strcpy(tmp, object);
+	if (tmp[strlen(tmp) - 1] != '/')
+		strcat(tmp, "/");
+	strcat(tmp, "..");
+
+	ret = get_fsid(object, fsid);
+	if (ret < 0) {
+		fprintf(stderr, "ERROR: get_fsid for %s failed. %s\n", object,
+				strerror(-ret));
+		goto out;
+	}
+
+	ret = get_fsid(tmp, fsid2);
+	if (ret < 0) {
+		ret = 0;
+		goto out;
+	}
+
+	if (!memcmp(fsid, fsid2, BTRFS_FSID_SIZE)) {
+		ret = 0;
+		goto out;
+	}
+
+	ret = 1;
+
+out:
+	free(tmp);
+	return ret;
+}
+
+static int count_bits(int v)
+{
+	unsigned int tmp = (unsigned int)v;
+	int cnt = 0;
+
+	while (tmp) {
+		if (tmp & 1)
+			cnt++;
+		tmp >>= 1;
+	}
+	return cnt;
+}
+
+static int autodetect_object_types(const char *object, int *types_out)
+{
+	int ret;
+	int is_btrfs_object;
+	int types = 0;
+	struct stat st;
+
+	is_btrfs_object = check_btrfs_object(object);
+
+	ret = lstat(object, &st);
+	if (ret < 0) {
+		ret = -errno;
+		goto out;
+	}
+
+	if (is_btrfs_object) {
+		types |= prop_object_inode;
+		if (st.st_ino == BTRFS_FIRST_FREE_OBJECTID) {
+			types |= prop_object_subvol;
+		}
+
+		ret = check_is_root(object);
+		if (ret < 0)
+			goto out;
+		if (ret)
+			types |= prop_object_root;
+	}
+
+	if (S_ISBLK(st.st_mode))
+		types |= prop_object_dev;
+
+	ret = 0;
+	*types_out = types;
+
+out:
+	return ret;
+}
+
+static int print_prop_help(const struct prop_handler *prop)
+{
+	int ret = 0;
+	fprintf(stdout, "%-20s%s\n", prop->name, prop->desc);
+	return ret;
+}
+
+static int dump_prop(const struct prop_handler *prop,
+		     const char *object,
+		     int types,
+		     int type,
+		     int name_and_help)
+{
+	int ret = 0;
+
+	if ((types & type) && (prop->types & type)) {
+		if (!name_and_help)
+			ret = prop->handler(type, object, prop->name, NULL);
+		else
+			ret = print_prop_help(prop);
+	}
+	return ret;
+}
+
+static int dump_props(int types, const char *object, int name_and_help)
+{
+	int ret;
+	int i;
+	int j;
+	const struct prop_handler *prop;
+
+	for (i = 0; prop_handlers[i].name; i++) {
+		prop = &prop_handlers[i];
+		for (j = 1; j < __prop_object_max; j <<= 1) {
+			ret = dump_prop(prop, object, types, j, name_and_help);
+			if (ret < 0) {
+				fprintf(stderr, "ERROR: failed to get property "
+						"'%s' for object.\n",
+						prop->name);
+				ret = 50;
+				goto out;
+			}
+		}
+	}
+
+	ret = 0;
+
+out:
+	return ret;
+}
+
+static int setget_prop(int types, const char *object, const char *name, const char *value)
+{
+	int ret;
+	const struct prop_handler *prop = NULL;
+
+	ret = parse_prop(name, prop_handlers, &prop);
+	if (ret == -1) {
+		fprintf(stderr, "ERROR: property is unknown\n");
+		ret = 40;
+		goto out;
+	} else if (ret) {
+		fprintf(stderr, "ERROR: parse_prop reported unknown error\n");
+		ret = 42;
+		goto out;
+	}
+
+	types &= prop->types;
+	if (!types) {
+		fprintf(stderr, "ERROR: object is not compatible "
+				"with property\n");
+		ret = 47;
+		goto out;
+	}
+
+	if (count_bits(types) > 1) {
+		fprintf(stderr, "ERROR: type of object is ambiguous. "
+				"Please specify a type by hand.\n");
+		ret = 48;
+		goto out;
+	}
+
+	if (value && prop->read_only) {
+		fprintf(stderr, "ERROR: %s is a read-only property.\n",
+				prop->name);
+		ret = 51;
+		goto out;
+	}
+
+	ret = prop->handler(types, object, name, value);
+
+	if (ret < 0) {
+		fprintf(stderr, "ERROR: failed to set/get property for "
+				"object.\n");
+		ret = 50;
+	} else {
+		ret = 0;
+	}
+
+out:
+	return ret;
+
+}
+
+static void parse_args(int argc, char **argv,
+		       const char * const *usage_str,
+		       int *types, char **object,
+		       char **name, char **value)
+{
+	int ret;
+	char *type_str = NULL;
+
+	optind = 1;
+	while (1) {
+		int c = getopt(argc, argv, "t:");
+		if (c < 0)
+			break;
+
+		switch (c) {
+		case 't':
+			type_str = optarg;
+			break;
+		default:
+			usage(usage_str);
+			break;
+		}
+	}
+
+	*types = 0;
+	if (type_str) {
+		if (!strcmp(type_str, "s") || !strcmp(type_str, "subvol"))
+			*types = prop_object_subvol;
+		else if (!strcmp(type_str, "f") ||
+			 !strcmp(type_str, "filesystem"))
+			*types = prop_object_root;
+		else if (!strcmp(type_str, "i") || !strcmp(type_str, "inode"))
+			*types = prop_object_inode;
+		else if (!strcmp(type_str, "d") || !strcmp(type_str, "device"))
+			*types = prop_object_dev;
+		else {
+			fprintf(stderr, "ERROR: invalid object type.\n");
+			usage(usage_str);
+		}
+	}
+
+	if (object && optind < argc)
+		*object = argv[optind++];
+	if (name && optind < argc)
+		*name = argv[optind++];
+	if (value && optind < argc)
+		*value = argv[optind++];
+
+	if (optind != argc) {
+		fprintf(stderr, "ERROR: invalid arguments.\n");
+		usage(usage_str);
+	}
+
+	if (!*types && object && *object) {
+		ret = autodetect_object_types(*object, types);
+		if (ret < 0) {
+			fprintf(stderr, "ERROR: failed to detect object type. "
+					"%s\n", strerror(-ret));
+			usage(usage_str);
+		}
+		if (!*types) {
+			fprintf(stderr, "ERROR: object is not a btrfs "
+					"object.\n");
+			usage(usage_str);
+		}
+	}
+}
+
+static int cmd_get(int argc, char **argv)
+{
+	int ret;
+	char *object;
+	char *name = NULL;
+	int types = 0;
+
+	if (check_argc_min(argc, 2) || check_argc_max(argc, 4))
+		usage(cmd_get_usage);
+
+	parse_args(argc, argv, cmd_get_usage, &types, &object, &name, NULL);
+	if (!object) {
+		fprintf(stderr, "ERROR: invalid arguments.\n");
+		usage(cmd_set_usage);
+	}
+
+	if (name)
+		ret = setget_prop(types, object, name, NULL);
+	else
+		ret = dump_props(types, object, 0);
+
+	return ret;
+}
+
+static int cmd_set(int argc, char **argv)
+{
+	int ret;
+	char *object;
+	char *name;
+	char *value;
+	int types = 0;
+
+	if (check_argc_min(argc, 4) || check_argc_max(argc, 5))
+		usage(cmd_set_usage);
+
+	parse_args(argc, argv, cmd_set_usage, &types, &object, &name, &value);
+	if (!object || !name || !value) {
+		fprintf(stderr, "ERROR: invalid arguments.\n");
+		usage(cmd_set_usage);
+	}
+
+	ret = setget_prop(types, object, name, value);
+
+	return ret;
+}
+
+static int cmd_list(int argc, char **argv)
+{
+	int ret;
+	char *object = NULL;
+	int types = 0;
+
+	if (check_argc_min(argc, 2) || check_argc_max(argc, 3))
+		usage(cmd_list_usage);
+
+	parse_args(argc, argv, cmd_list_usage, &types, &object, NULL, NULL);
+	if (!object) {
+		fprintf(stderr, "ERROR: invalid arguments.\n");
+		usage(cmd_set_usage);
+	}
+
+	ret = dump_props(types, object, 1);
+
+	return ret;
+}
+
+const struct cmd_group property_cmd_group = {
+	property_cmd_group_usage, NULL, {
+		{ "get", cmd_get, cmd_get_usage, NULL, 0 },
+		{ "set", cmd_set, cmd_set_usage, NULL, 0 },
+		{ "list", cmd_list, cmd_list_usage, NULL, 0 },
+		{ 0, 0, 0, 0, 0 },
+	}
+};
+
+int cmd_property(int argc, char **argv)
+{
+	return handle_command_group(&property_cmd_group, argc, argv);
+}
diff --git a/commands.h b/commands.h
index a303a50..a1cfa2d 100644
--- a/commands.h
+++ b/commands.h
@@ -88,6 +88,7 @@ extern const struct cmd_group balance_cmd_group;
 extern const struct cmd_group device_cmd_group;
 extern const struct cmd_group scrub_cmd_group;
 extern const struct cmd_group inspect_cmd_group;
+extern const struct cmd_group property_cmd_group;
 
 int cmd_subvolume(int argc, char **argv);
 int cmd_filesystem(int argc, char **argv);
@@ -95,3 +96,4 @@ int cmd_balance(int argc, char **argv);
 int cmd_device(int argc, char **argv);
 int cmd_scrub(int argc, char **argv);
 int cmd_inspect(int argc, char **argv);
+int cmd_property(int argc, char **argv);
diff --git a/props.c b/props.c
new file mode 100644
index 0000000..f3e7dd4
--- /dev/null
+++ b/props.c
@@ -0,0 +1,114 @@
+/*
+ * 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 "btrfslabel.h"
+#include "props.h"
+
+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;
+}
+
+int prop_label(enum prop_object_type type,
+	       const char *object,
+	       const char *name,
+	       const char *value)
+{
+	int ret;
+	char *label = NULL;
+
+	if (value) {
+		ret = set_label((char*)object, (char*)value);
+	} else {
+		ret = get_label((char*)object, &label);
+		if (!ret)
+			fprintf(stdout, "label=%s\n", label);
+		free(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}
+};
+
+
diff --git a/props.h b/props.h
new file mode 100644
index 0000000..faa4410
--- /dev/null
+++ b/props.h
@@ -0,0 +1,43 @@
+/*
+ * 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.
+ */
+
+#ifndef PROPS_H_
+#define PROPS_H_
+
+enum prop_object_type {
+	prop_object_dev		= (1 << 0),
+	prop_object_root	= (1 << 1),
+	prop_object_subvol	= (1 << 2),
+	prop_object_inode	= (1 << 3),
+	__prop_object_max,
+};
+
+typedef int (*prop_handler_t)(enum prop_object_type type,
+			      const char *object,
+			      const char *name,
+			      const char *value);
+
+struct prop_handler {
+	const char *name;
+	const char *desc;
+	int read_only;
+	int types;
+	prop_handler_t handler;
+};
+
+extern const struct prop_handler prop_handlers[];
+
+#endif /* PROPS_H_ */
-- 
1.7.10

Re: [RFC PATCHv2 0/3] Btrfs-progs: introduce btrfs property subgroup

[Goffredo Baroncelli]

Hi Alexander,

On 06/27/2012 03:16 PM, Alexander Block wrote:
> This patchset introduces the btrfs property subgroup. It is the
> result of a discussion we had on IRC. I tried to make the properties
> interface as generic and extensible as possible. Comments are welcome.
> 
> Currently the command group looks like this:
> btrfs prop set [-t <type>] /path/to/object <name> <value>
> btrfs prop get [-t <type>] /path/to/object [<name>] (omitting name dumps all)
> btrfs prop list [-t <type>] /path/to/object (lists properties with description)
> 
> The type is used to explicitly specify what type of object you mean. This is 
> necessary in case the object+property combination is ambiguous.  For example
> '/path/to/fs/root' could mean the root subvolume, the directory inode or the 
> filesystem itself. Normally, btrfs-progs will try to detect the type 
> automatically.


Instead of using

   btrfs prop set -t filesystem ....
   btrfs prop set -t subvolume ....
   btrfs prop set -t inode ....

what about

   btrfs filesystem prop set .....
   btrfs subvolume prop set .....
   btrfs inode prop set .....

?

btrfs has already grouped the commands by "category" (even tough I have
to admit that some command doesn't fit its group. Why do not use this
instead of "-t <object type>". If we need new type we could create it on
demand...

> 
> David suggested that it should also be possible to specify objects by
> their id/uuid/fsid. I like that idea, but would be happy if someone else
> could take over that part :)

This proposal makes sense.
> 
> For now, I've implemented two properties:
> 1. read-only. Usable on subvolumes to toggle the read-only flags.
> 2. label. I looked through btrfs to find good examples of things that
>    could be moved to the new properties interface and the filesystem
>    label looked like a good one. There are for sure more, but that is
>    something for later (and maybe for someone else). I would suggest 
>    to move everthing that makes sense over to the props interface and 
>    mark the old interfaces as deprecated. Comments on this are welcome.

What is the suppose goal/benefit/advantage to switch to a new interface
? Really, it is a true question.

> 
> Patch version history:
> v1
>   Initial version.
> v2
>   - Removed the filesystem prefix and implemented it as new command group
>   - Switched from the <name>[=<value>] form to the set/get <name> [<value>] 
>     form.
>   - Removed patches "Btrfs-progs: make filesystem_cmd_group non const"
>     and "Btrfs-progs: move skip_prefix and prefixcmp to utils.c". They
>     are not needed anymore due to the 'btrfs prop list' command.
>   - Udjusted the subvol flags patch to be compatible to the "Btrfs: use 
>     _IOR for BTRFS_IOC_SUBVOL_GETFLAGS" patch.
>   - Using -t <type> instead of <type>: prefix now.
>   - Changes are based on feedback from Ilya and David.
> 
> Alex.
> 
> Alexander Block (3):
>   Btrfs-progs: add BTRFS_IOC_SUBVOL_GET/SETFLAGS to ioctl.h
>   Btrfs-progs: let get_label return the label instead of of printing it
>   Btrfs-progs: introduce btrfs property subgroup
> 
>  Makefile          |    5 +-
>  btrfs.c           |    1 +
>  btrfslabel.c      |   13 +-
>  btrfslabel.h      |    4 +-
>  cmds-filesystem.c |   14 +-
>  cmds-property.c   |  459 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  commands.h        |    2 +
>  ioctl.h           |    2 +
>  props.c           |  114 +++++++++++++
>  props.h           |   43 +++++

Please update the man page too... This could help the process of
creating a new interface.

>  10 files changed, 645 insertions(+), 12 deletions(-)
>  create mode 100644 cmds-property.c
>  create mode 100644 props.c
>  create mode 100644 props.h
> 

Re: [RFC PATCHv2 0/3] Btrfs-progs: introduce btrfs property subgroup

[Alexander Block]

On Wed, Jun 27, 2012 at 7:41 PM, Goffredo Baroncelli <kreijack@libero.it> wrote:
> Hi Alexander,
>
> On 06/27/2012 03:16 PM, Alexander Block wrote:
>> This patchset introduces the btrfs property subgroup. It is the
>> result of a discussion we had on IRC. I tried to make the properties
>> interface as generic and extensible as possible. Comments are welcome.
>>
>> Currently the command group looks like this:
>> btrfs prop set [-t <type>] /path/to/object <name> <value>
>> btrfs prop get [-t <type>] /path/to/object [<name>] (omitting name dumps all)
>> btrfs prop list [-t <type>] /path/to/object (lists properties with description)
>>
>> The type is used to explicitly specify what type of object you mean. This is
>> necessary in case the object+property combination is ambiguous.  For example
>> '/path/to/fs/root' could mean the root subvolume, the directory inode or the
>> filesystem itself. Normally, btrfs-progs will try to detect the type
>> automatically.
>
>
> Instead of using
>
>   btrfs prop set -t filesystem ....
>   btrfs prop set -t subvolume ....
>   btrfs prop set -t inode ....
>
> what about
>
>   btrfs filesystem prop set .....
>   btrfs subvolume prop set .....
>   btrfs inode prop set .....
>
> ?
Specifying the object type is not needed normally, so the form where
the prop commands
are in their own command group is normally shorter and easier to type.
The type argument
is really only needed for ambiguous properties.
>
> btrfs has already grouped the commands by "category" (even tough I have
> to admit that some command doesn't fit its group. Why do not use this
> instead of "-t <object type>". If we need new type we could create it on
> demand...
>
>>
>> David suggested that it should also be possible to specify objects by
>> their id/uuid/fsid. I like that idea, but would be happy if someone else
>> could take over that part :)
>
> This proposal makes sense.
>>
>> For now, I've implemented two properties:
>> 1. read-only. Usable on subvolumes to toggle the read-only flags.
>> 2. label. I looked through btrfs to find good examples of things that
>>    could be moved to the new properties interface and the filesystem
>>    label looked like a good one. There are for sure more, but that is
>>    something for later (and maybe for someone else). I would suggest
>>    to move everthing that makes sense over to the props interface and
>>    mark the old interfaces as deprecated. Comments on this are welcome.
>
> What is the suppose goal/benefit/advantage to switch to a new interface
> ? Really, it is a true question.
>
The reason is that there will come a lot more things that you can
configure on an
inode/subvolume/filesystem/device basis and we agreed that a generic interface
for such configurations will be a good thing in the future.
>>
>> Patch version history:
>> v1
>>   Initial version.
>> v2
>>   - Removed the filesystem prefix and implemented it as new command group
>>   - Switched from the <name>[=<value>] form to the set/get <name> [<value>]
>>     form.
>>   - Removed patches "Btrfs-progs: make filesystem_cmd_group non const"
>>     and "Btrfs-progs: move skip_prefix and prefixcmp to utils.c". They
>>     are not needed anymore due to the 'btrfs prop list' command.
>>   - Udjusted the subvol flags patch to be compatible to the "Btrfs: use
>>     _IOR for BTRFS_IOC_SUBVOL_GETFLAGS" patch.
>>   - Using -t <type> instead of <type>: prefix now.
>>   - Changes are based on feedback from Ilya and David.
>>
>> Alex.
>>
>> Alexander Block (3):
>>   Btrfs-progs: add BTRFS_IOC_SUBVOL_GET/SETFLAGS to ioctl.h
>>   Btrfs-progs: let get_label return the label instead of of printing it
>>   Btrfs-progs: introduce btrfs property subgroup
>>
>>  Makefile          |    5 +-
>>  btrfs.c           |    1 +
>>  btrfslabel.c      |   13 +-
>>  btrfslabel.h      |    4 +-
>>  cmds-filesystem.c |   14 +-
>>  cmds-property.c   |  459 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  commands.h        |    2 +
>>  ioctl.h           |    2 +
>>  props.c           |  114 +++++++++++++
>>  props.h           |   43 +++++
>
> Please update the man page too... This could help the process of
> creating a new interface.
>
>>  10 files changed, 645 insertions(+), 12 deletions(-)
>>  create mode 100644 cmds-property.c
>>  create mode 100644 props.c
>>  create mode 100644 props.h
>>
>