[PATCH v2 0/5] Add user-space support for read-only snapshot creation.

[PATCH v2 0/5] Add user-space support for read-only snapshot creation.

[Andreas Philipp]

Changelog v2:
  - Fixed uninitialized variable (args).
  - Corrected order of patches to make everything compile.
  - Fixed some style errors.

There is kernel side support for the creation of read-only snapshots
for some time now, but I did not find any patches for the userspace
btrfs utilites. Thus I created this patchset which is tested and
working with kernel version 2.6.39-rc2.

Andreas Philipp (5):
  Added support for an additional ioctl.
  Add support for read-only subvolumes.
  Support the new parameters in do_clone(int argc, char** argv).
  Test the additional ioctl.
  Updated manpage for btrfs subvolume snapshot.

 btrfs.c        |    6 +++---
 btrfs_cmds.c   |   48 ++++++++++++++++++++++++++++++++++++++++--------
 ioctl-test.c   |    1 +
 ioctl.h        |   14 ++++++++++++++
 man/btrfs.8.in |   11 ++++++-----
 5 files changed, 64 insertions(+), 16 deletions(-)

-- 
1.7.4.1

[PATCH 1/5] Added support for an additional ioctl.

[Andreas Philipp]

Added BTRFS_IOC_SNAP_CREATE_V2 and struct btrfs_ioctl_vol_args_v2 as
defined in fs/btrfs/ioctl.h in the kernel sources.

Signed-off-by: Andreas Philipp <philipp.andreas@gmail.com>
---
 ioctl.h |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/ioctl.h b/ioctl.h
index 776d7a9..358f814 100644
--- a/ioctl.h
+++ b/ioctl.h
@@ -30,6 +30,17 @@ struct btrfs_ioctl_vol_args {
 	char name[BTRFS_PATH_NAME_MAX + 1];
 };
 
+#define BTRFS_SUBVOL_RDONLY		(1ULL << 1)
+#define BTRFS_SUBVOL_NAME_MAX 4039
+
+struct btrfs_ioctl_vol_args_v2 {
+	__s64 fd;
+	__u64 transid;
+	__u64 flags;
+	__u64 unused[4];
+	char name[BTRFS_SUBVOL_NAME_MAX + 1];
+};
+
 struct btrfs_ioctl_search_key {
 	/* which root are we searching.  0 is the tree of tree roots */
 	__u64 tree_id;
@@ -132,6 +143,7 @@ struct btrfs_ioctl_space_args {
 	struct btrfs_ioctl_space_info spaces[0];
 };
 
+/* BTRFS_IOC_SNAP_CREATE is no longer used by the btrfs command */
 #define BTRFS_IOC_SNAP_CREATE _IOW(BTRFS_IOCTL_MAGIC, 1, \
 				   struct btrfs_ioctl_vol_args)
 #define BTRFS_IOC_DEFRAG _IOW(BTRFS_IOCTL_MAGIC, 2, \
@@ -169,4 +181,6 @@ struct btrfs_ioctl_space_args {
 #define BTRFS_IOC_DEFAULT_SUBVOL _IOW(BTRFS_IOCTL_MAGIC, 19, u64)
 #define BTRFS_IOC_SPACE_INFO _IOWR(BTRFS_IOCTL_MAGIC, 20, \
 				    struct btrfs_ioctl_space_args)
+#define BTRFS_IOC_SNAP_CREATE_V2 _IOW(BTRFS_IOCTL_MAGIC, 23, \
+				   struct btrfs_ioctl_vol_args_v2)
 #endif
-- 
1.7.4.1

[PATCH 2/5] Add support for read-only subvolumes.

[Andreas Philipp]

Use BTRFS_IOC_CREATE_SNAP_V2 instead of BTRFS_IOC_CREATE_SNAP and add
an option for the creation of a readonly snapshot.

Signed-off-by: Andreas Philipp <philipp.andreas@gmail.com>
---
 btrfs_cmds.c |   48 ++++++++++++++++++++++++++++++++++++++++--------
 1 files changed, 40 insertions(+), 8 deletions(-)

diff --git a/btrfs_cmds.c b/btrfs_cmds.c
index 8031c58..9367bac 100644
--- a/btrfs_cmds.c
+++ b/btrfs_cmds.c
@@ -43,7 +43,7 @@
 
 #ifdef __CHECKER__
 #define BLKGETSIZE64 0
-#define BTRFS_IOC_SNAP_CREATE 0
+#define BTRFS_IOC_SNAP_CREATE_V2 0
 #define BTRFS_VOL_NAME_MAX 255
 struct btrfs_ioctl_vol_args { char name[BTRFS_VOL_NAME_MAX]; };
 static inline int ioctl(int fd, int define, void *arg) { return 0; }
@@ -310,13 +310,38 @@ int do_subvol_list(int argc, char **argv)
 int do_clone(int argc, char **argv)
 {
 	char	*subvol, *dst;
-	int	res, fd, fddst, len;
+	int	res, fd, fddst, len, optind = 0, readonly = 0;
 	char	*newname;
 	char	*dstdir;
+	struct btrfs_ioctl_vol_args_v2	args;
 
-	subvol = argv[1];
-	dst = argv[2];
-	struct btrfs_ioctl_vol_args	args;
+	memset(&args, 0, sizeof(args));
+
+	while (1) {
+		int c = getopt(argc, argv, "r");
+
+		if (c < 0)
+			break;
+		switch (c) {
+		case 'r':
+			optind++;
+			readonly = 1;
+			break;
+		default:
+			fprintf(stderr,
+				"Invalid arguments for subvolume snapshot\n");
+			free(argv);
+			return 1;
+		}
+	}
+	if (argc - optind < 2) {
+		fprintf(stderr, "Invalid arguments for subvolume snapshot\n");
+		free(argv);
+		return 1;
+	}
+
+	subvol = argv[optind+1];
+	dst = argv[optind+2];
 
 	res = test_issubvolume(subvol);
 	if(res<0){
@@ -372,11 +397,18 @@ int do_clone(int argc, char **argv)
 		return 12;
 	}
 
-	printf("Create a snapshot of '%s' in '%s/%s'\n",
-	       subvol, dstdir, newname);
+	if (readonly) {
+		args.flags |= BTRFS_SUBVOL_RDONLY;
+		printf("Create a readonly snapshot of '%s' in '%s/%s'\n",
+		       subvol, dstdir, newname);
+	} else {
+		printf("Create a snapshot of '%s' in '%s/%s'\n",
+		       subvol, dstdir, newname);
+	}
+
 	args.fd = fd;
 	strcpy(args.name, newname);
-	res = ioctl(fddst, BTRFS_IOC_SNAP_CREATE, &args);
+	res = ioctl(fddst, BTRFS_IOC_SNAP_CREATE_V2, &args);
 
 	close(fd);
 	close(fddst);
-- 
1.7.4.1

[PATCH 3/5] Support the new parameters in do_clone(int argc, char** argv).

[Andreas Philipp]

Now 'btrfs subvolume snapshot' takes not two but only at least two
parameters. Additionally, the help message is updated accordingly.

Signed-off-by: Andreas Philipp <philipp.andreas@gmail.com>
---
 btrfs.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/btrfs.c b/btrfs.c
index 46314cf..f70d64b 100644
--- a/btrfs.c
+++ b/btrfs.c
@@ -44,9 +44,9 @@ static struct Command commands[] = {
 	/*
 		avoid short commands different for the case only
 	*/
-	{ do_clone, 2,
-	  "subvolume snapshot", "<source> [<dest>/]<name>\n"
-		"Create a writable snapshot of the subvolume <source> with\n"
+	{ do_clone, -2,
+	  "subvolume snapshot", "[-r] <source> [<dest>/]<name>\n"
+		"Create a writable/readonly snapshot of the subvolume <source> with\n"
 		"the name <name> in the <dest> directory."
 	},
 	{ do_delete_subvolume, 1,
-- 
1.7.4.1

[PATCH 4/5] Test the additional ioctl.

[Andreas Philipp]

Signed-off-by: Andreas Philipp <philipp.andreas@gmail.com>
---
 ioctl-test.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/ioctl-test.c b/ioctl-test.c
index 7cf3bc2..1c27d61 100644
--- a/ioctl-test.c
+++ b/ioctl-test.c
@@ -22,6 +22,7 @@ unsigned long ioctls[] = {
 	BTRFS_IOC_INO_LOOKUP,
 	BTRFS_IOC_DEFAULT_SUBVOL,
 	BTRFS_IOC_SPACE_INFO,
+	BTRFS_IOC_SNAP_CREATE_V2,
 	0 };
 
 int main(int ac, char **av)
-- 
1.7.4.1

[PATCH 5/5] Updated manpage for btrfs subvolume snapshot.

[Andreas Philipp]

Signed-off-by: Andreas Philipp <philipp.andreas@gmail.com>
---
 man/btrfs.8.in |   11 ++++++-----
 1 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/man/btrfs.8.in b/man/btrfs.8.in
index 26ef982..b59bc6f 100644
--- a/man/btrfs.8.in
+++ b/man/btrfs.8.in
@@ -5,7 +5,7 @@
 .SH NAME
 btrfs \- control a btrfs filesystem
 .SH SYNOPSIS
-\fBbtrfs\fP \fBsubvolume snapshot\fP\fI <source> [<dest>/]<name>\fP
+\fBbtrfs\fP \fBsubvolume snapshot\fP\fI [-r] <source> [<dest>/]<name>\fP
 .PP
 \fBbtrfs\fP \fBsubvolume delete\fP\fI <subvolume>\fP
 .PP
@@ -70,10 +70,11 @@ command.
 .SH COMMANDS
 .TP
 
-\fBsubvolume snapshot\fR\fI <source> [<dest>/]<name>\fR
-Create a writable snapshot of the subvolume \fI<source>\fR with the name
-\fI<name>\fR in the \fI<dest>\fR directory. If \fI<source>\fR is not a
-subvolume, \fBbtrfs\fR returns an error.
+\fBsubvolume snapshot\fR\fI [-r] <source> [<dest>/]<name>\fR
+Create a writable/readonly snapshot of the subvolume \fI<source>\fR with the
+name \fI<name>\fR in the \fI<dest>\fR directory. If \fI<source>\fR is not a
+subvolume, \fBbtrfs\fR returns an error. If \fI-r\fR is given, the snapshot
+will be readonly.
 .TP
 
 \fBsubvolume delete\fR\fI <subvolume>\fR
-- 
1.7.4.1

Re: Read Only snapshots

[Chris Mason]

Excerpts from David Morgado's message of 2011-04-24 21:24:16 -0400:
> Hi, btrfs-progs patches for read only snapshots aren't in Chris
> repository yet but btrfs already has support for that in place so,
> someone forgot about this?
> 
> It appears that some new patches are coming to Chris btrfs-progs (new
> tmp branch) so this was a nice opportunity to get those patches in.

Right, the tmp branch is the one I'm pushing around and testing for
release.  I'll make sure the readonly snapshots code gets in there too.

-chris

[PATCH 0/5] Add user-space support for read-only snapshot creation.

[Andreas Philipp]

There is kernel side support for the creation of read-only snapshots
for some time now, but I did not find any patches for the userspace
btrfs utilites. Thus I created this patchset which is tested and
working with kernel version 2.6.39-rc2.

Andreas Philipp (5):
  Add support for read-only subvolumes.
  Support the new parameters in do_clone(int argc, char** argv).
  Added support for an additional ioctl.
  Test the additional ioctl.
  Updated documentation for btrfs subvolume snapshot.

 btrfs.c        |    6 +++---
 btrfs_cmds.c   |   44 ++++++++++++++++++++++++++++++++++++--------
 ioctl-test.c   |    1 +
 ioctl.h        |   14 ++++++++++++++
 man/btrfs.8.in |   11 ++++++-----
 5 files changed, 60 insertions(+), 16 deletions(-)

-- 
1.7.4.1

[PATCH 4/5] Test the additional ioctl.

[Andreas Philipp]

Signed-off-by: Andreas Philipp <philipp.andreas@gmail.com>
---
 ioctl-test.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/ioctl-test.c b/ioctl-test.c
index 7cf3bc2..1c27d61 100644
--- a/ioctl-test.c
+++ b/ioctl-test.c
@@ -22,6 +22,7 @@ unsigned long ioctls[] = {
 	BTRFS_IOC_INO_LOOKUP,
 	BTRFS_IOC_DEFAULT_SUBVOL,
 	BTRFS_IOC_SPACE_INFO,
+	BTRFS_IOC_SNAP_CREATE_V2,
 	0 };
 
 int main(int ac, char **av)
-- 
1.7.4.1

[PATCH 0/5] Add user-space support for read-only snapshot creation.

[Andreas Philipp]

There is kernel side support for the creation of read-only snapshots
for some time now, but I did not find any patches for the userspace
btrfs utilites. Thus I created this patchset which is tested and
working with kernel version 2.6.39-rc2.

Andreas Philipp (5):
  Add support for read-only subvolumes.
  Support the new parameters in do_clone(int argc, char** argv).
  Added support for an additional ioctl.
  Test the additional ioctl.
  Updated documentation for btrfs subvolume snapshot.

 btrfs.c        |    6 +++---
 btrfs_cmds.c   |   44 ++++++++++++++++++++++++++++++++++++--------
 ioctl-test.c   |    1 +
 ioctl.h        |   14 ++++++++++++++
 man/btrfs.8.in |   11 ++++++-----
 5 files changed, 60 insertions(+), 16 deletions(-)

-- 
1.7.4.1

[PATCH 4/5] Test the additional ioctl.

[Andreas Philipp]

Signed-off-by: Andreas Philipp <philipp.andreas@gmail.com>
---
 ioctl-test.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/ioctl-test.c b/ioctl-test.c
index 7cf3bc2..1c27d61 100644
--- a/ioctl-test.c
+++ b/ioctl-test.c
@@ -22,6 +22,7 @@ unsigned long ioctls[] = {
 	BTRFS_IOC_INO_LOOKUP,
 	BTRFS_IOC_DEFAULT_SUBVOL,
 	BTRFS_IOC_SPACE_INFO,
+	BTRFS_IOC_SNAP_CREATE_V2,
 	0 };
 
 int main(int ac, char **av)
-- 
1.7.4.1