Btrfs devel - Sep 2010 - [PATCH] 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-all.git

Regards
G.Baroncelli

diff --git a/Makefile b/Makefile
index 525676e..c06e512 100644
--- a/Makefile
+++ b/Makefile
@@ -4,7 +4,7 @@ CFLAGS = -g -Werror -Os
 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
+	  volumes.o utils.o btrfs-list.o btrfslabel.o
 
 #
 CHECKFLAGS=-D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ -Wbitwise \
diff --git a/btrfs.c b/btrfs.c
index ab5e57f..ab0a9da 100644
--- a/btrfs.c
+++ b/btrfs.c
@@ -95,6 +95,10 @@ static struct Command commands[] = {
 	  "filesystem balance", "<path>\n"
 		"Balance the chunks across the device."
 	},
+	{ do_change_label, -1,
+	  "filesystem label", "<device> [<label>]\n"
+		"Get or set a label of a filesystem."
+	},
 	{ do_scan,
 	  999, "device scan", "[<device>
[<device>..]\n"
 		"Scan all device for or the passed device for a btrfs\n"
@@ -108,11 +112,6 @@ static struct Command commands[] = {
 	  "device delete", "<dev> [<dev>..]
<path>\n"
 		"Remove a device from a filesystem."
 	},
-	/* coming soon
-	{ 2, "filesystem label", "<label> <path>\n"
-		"Set the label of a filesystem"
-	}
-	*/
 	{ 0, 0 , 0 }
 };
 
diff --git a/btrfs_cmds.c b/btrfs_cmds.c
index 8031c58..3f632c8 100644
--- a/btrfs_cmds.c
+++ b/btrfs_cmds.c
@@ -40,6 +40,7 @@
 #include "volumes.h"
 
 #include "btrfs_cmds.h"
+#include "btrfslabel.h"
 
 #ifdef __CHECKER__
 #define BLKGETSIZE64 0
@@ -834,6 +835,21 @@ int do_set_default_subvol(int nargs, char **argv)
 	return 0;
 }
 
+int do_change_label(int nargs, char **argv)
+{
+	/* check the number of argument */
+	if ( nargs > 3 ){
+		fprintf(stderr, "ERROR: ''%s'' requires maximum 2
args\n",
+			argv[0]);
+		return -2;
+	}else if (nargs == 2){
+		return get_label(argv[1]);
+	} else {	/* nargs == 0 */
+		return set_label(argv[1], argv[2]);
+	}
+}
+
+
 int do_df_filesystem(int nargs, char **argv)
 {
 	struct btrfs_ioctl_space_args *sargs;
diff --git a/btrfs_cmds.h b/btrfs_cmds.h
index 7bde191..ab722d4 100644
--- a/btrfs_cmds.h
+++ b/btrfs_cmds.h
@@ -32,3 +32,4 @@ int list_subvols(int fd);
 int do_df_filesystem(int nargs, char **argv);
 int find_updated_files(int fd, u64 root_id, u64 oldest_gen);
 int do_find_newer(int argc, char **argv);
+int do_change_label(int argc, char **argv);
diff --git a/btrfslabel.c b/btrfslabel.c
new file mode 100644
index 0000000..c9f4684
--- /dev/null
+++ b/btrfslabel.c
@@ -0,0 +1,121 @@
+/*
+ * Copyright (C) 2008 Morey Roof.   All rights reserved.
+ *
+ * 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.
+ */
+
+#define _GNU_SOURCE
+
+#ifndef __CHECKER__
+#include <sys/ioctl.h>
+#include <sys/mount.h>
+#include "ioctl.h"
+#endif /* __CHECKER__ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <dirent.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <linux/fs.h>
+#include <linux/limits.h>
+#include <ctype.h>
+#include "kerncompat.h"
+#include "ctree.h"
+#include "utils.h"
+#include "version.h"
+#include "disk-io.h"
+#include "transaction.h"
+
+#define MOUNTED                        1
+#define UNMOUNTED                      2
+#define GET_LABEL                      3
+#define SET_LABEL                      4
+
+static void change_label_unmounted(char *dev, char *nLabel)
+{
+       struct btrfs_root *root;
+       struct btrfs_trans_handle *trans;
+
+       /* Open the super_block at the default location
+        * and as read-write.
+        */
+       root = open_ctree(dev, 0, 1);
+
+       trans = btrfs_start_transaction(root, 1);
+       strncpy(root->fs_info->super_copy.label, nLabel,
BTRFS_LABEL_SIZE);
+       btrfs_commit_transaction(trans, root);
+
+       /* Now we close it since we are done. */
+       close_ctree(root);
+}
+
+static void get_label_unmounted(char *dev)
+{
+       struct btrfs_root *root;
+
+       /* Open the super_block at the default location
+        * and as read-only.
+        */
+       root = open_ctree(dev, 0, 0);
+
+       fprintf(stdout, "%s\n",
root->fs_info->super_copy.label);
+
+       /* Now we close it since we are done. */
+       close_ctree(root);
+}
+
+int get_label(char *btrfs_dev)
+{
+
+	int ret;
+	ret = check_mounted(btrfs_dev);
+	if (ret < 0)
+	{
+	       fprintf(stderr, "FATAL: error checking %s mount status\n", 
btrfs_dev);
+	       return -1;
+	}
+
+	if(ret != 0)
+	{
+	       fprintf(stderr, "FATAL: the filesystem has to be 
unmounted\n");
+	       return -2;
+	}
+	get_label_unmounted(btrfs_dev);
+	return 0;
+}
+
+
+int set_label(char *btrfs_dev, char *nLabel)
+{
+
+	int ret;
+	ret = check_mounted(btrfs_dev);
+	if (ret < 0)
+	{
+	       fprintf(stderr, "FATAL: error checking %s mount status\n", 
btrfs_dev);
+	       return -1;
+	}
+
+	if(ret != 0)
+	{
+	       fprintf(stderr, "FATAL: the filesystem has to be 
unmounted\n");
+	       return -2;
+	}
+	change_label_unmounted(btrfs_dev, nLabel);
+	return 0;
+}
diff --git a/btrfslabel.h b/btrfslabel.h
new file mode 100644
index 0000000..abf43ad
--- /dev/null
+++ b/btrfslabel.h
@@ -0,0 +1,5 @@
+/* btrflabel.h */
+
+
+int get_label(char *btrfs_dev);
+int set_label(char *btrfs_dev, char *nLabel);
\ No newline at end of file
diff --git a/man/btrfs.8.in b/man/btrfs.8.in
index 26ef982..c1a8a42 100644
--- a/man/btrfs.8.in
+++ b/man/btrfs.8.in
@@ -21,6 +21,8 @@ btrfs \- control a btrfs filesystem
 .PP
 \fBbtrfs\fP \fBfilesystem resize\fP\fI [+/\-]<size>[gkm]|max
<filesystem>\fP
 .PP
+\fBbtrfs\fP \fBfilesystem label\fP\fI <dev> [newlabel]\fP
+.PP
 \fBbtrfs\fP \fBdevice scan\fP\fI [<device> [<device>..]]\fP
 .PP
 \fBbtrfs\fP \fBdevice show\fP\fI <dev>|<label>
[<dev>|<label>...]\fP
@@ -138,6 +140,23 @@ can expand the partition before enlarging the filesystem 
and shrink the
 partition after reducing the size of the filesystem.
 .TP
 
+\fBbtrfs\fP \fBfilesystem label\fP\fI <dev> [newlabel]\fP
+Show or update the label of a filesystem. \fI<dev>\fR is used to identify
the
+filesystem. 
+If a \fInewlabel\fR optional argument is passed, the label is changed. The
+following costraints exist for a label:
+.IP
+- the maximum allowable lenght shall be less or equal than 256 chars
+.IP
+- the label shall not  contain the ''/'' or
''\\'' characters.
+
+NOTE: Currently there are the following limitations:
+.IP
+- the filesystem has to be unmounted
+.IP
+- the filesystem should not have more than one device.
+.TP
+
 \fBfilesystem show\fR [<uuid>|<label>]\fR
 Show the btrfs filesystem with some additional info. If no UUID or label is
 passed, \fBbtrfs\fR show info of all the btrfs filesystem.
diff --git a/utils.c b/utils.c
index 2f4c6e1..ea8e5b7 100644
--- a/utils.c
+++ b/utils.c
@@ -587,7 +587,7 @@ error:
 }
 
 /*
- * returns 1 if the device was mounted, < 0 on error or 0 if everything
+ * returns 1 if the device is mounted, < 0 on error or 0 if everything
  * is safe to continue.  TODO, this should also scan multi-device 
filesystems
  */
 int check_mounted(char *file)
@@ -638,6 +638,39 @@ int check_mounted(char *file)
 	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];
@@ -820,3 +853,27 @@ 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;
+}
diff --git a/utils.h b/utils.h
index 7ff542b..838b65e 100644
--- a/utils.h
+++ b/utils.h
@@ -40,4 +40,6 @@ int check_mounted(char *devicename);
 int btrfs_device_already_in_root(struct btrfs_root *root, int fd,
 				 int super_offset);
 char *pretty_sizes(u64 size);
+int check_label(char *input);
+int get_mountpt(char *dev, char *mntpt, size_t size);
 #endif


-- 
gpg key@ keyserver.linux.it:Goffredo Baroncelli (ghigo)
<kreijackATinwind.it>
Key fingerprint = 4769 7E51 5293 D36C 814E  C054 BF04 F161 3DC5 0512

Worked like it should for me :)


Thanks a lot for your work.
I hope this patch will be merged soon.

Like G.Baroncelli says: It''s such an essential feature.

Regards,
Felix


Goffredo Baroncelli schrieb:
> 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-all.git
> 
> Regards
> G.Baroncelli
> 
> diff --git a/Makefile b/Makefile
> index 525676e..c06e512 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -4,7 +4,7 @@ CFLAGS = -g -Werror -Os
>  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
> +	  volumes.o utils.o btrfs-list.o btrfslabel.o
>  
>  #
>  CHECKFLAGS=-D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ -Wbitwise \
> diff --git a/btrfs.c b/btrfs.c
> index ab5e57f..ab0a9da 100644
> --- a/btrfs.c
> +++ b/btrfs.c
> @@ -95,6 +95,10 @@ static struct Command commands[] = {
>  	  "filesystem balance", "<path>\n"
>  		"Balance the chunks across the device."
>  	},
> +	{ do_change_label, -1,
> +	  "filesystem label", "<device>
[<label>]\n"
> +		"Get or set a label of a filesystem."
> +	},
>  	{ do_scan,
>  	  999, "device scan", "[<device>
[<device>..]\n"
>  		"Scan all device for or the passed device for a btrfs\n"
> @@ -108,11 +112,6 @@ static struct Command commands[] = {
>  	  "device delete", "<dev> [<dev>..]
<path>\n"
>  		"Remove a device from a filesystem."
>  	},
> -	/* coming soon
> -	{ 2, "filesystem label", "<label>
<path>\n"
> -		"Set the label of a filesystem"
> -	}
> -	*/
>  	{ 0, 0 , 0 }
>  };
>  
> diff --git a/btrfs_cmds.c b/btrfs_cmds.c
> index 8031c58..3f632c8 100644
> --- a/btrfs_cmds.c
> +++ b/btrfs_cmds.c
> @@ -40,6 +40,7 @@
>  #include "volumes.h"
>  
>  #include "btrfs_cmds.h"
> +#include "btrfslabel.h"
>  
>  #ifdef __CHECKER__
>  #define BLKGETSIZE64 0
> @@ -834,6 +835,21 @@ int do_set_default_subvol(int nargs, char **argv)
>  	return 0;
>  }
>  
> +int do_change_label(int nargs, char **argv)
> +{
> +	/* check the number of argument */
> +	if ( nargs > 3 ){
> +		fprintf(stderr, "ERROR: ''%s'' requires maximum 2
args\n",
> +			argv[0]);
> +		return -2;
> +	}else if (nargs == 2){
> +		return get_label(argv[1]);
> +	} else {	/* nargs == 0 */
> +		return set_label(argv[1], argv[2]);
> +	}
> +}
> +
> +
>  int do_df_filesystem(int nargs, char **argv)
>  {
>  	struct btrfs_ioctl_space_args *sargs;
> diff --git a/btrfs_cmds.h b/btrfs_cmds.h
> index 7bde191..ab722d4 100644
> --- a/btrfs_cmds.h
> +++ b/btrfs_cmds.h
> @@ -32,3 +32,4 @@ int list_subvols(int fd);
>  int do_df_filesystem(int nargs, char **argv);
>  int find_updated_files(int fd, u64 root_id, u64 oldest_gen);
>  int do_find_newer(int argc, char **argv);
> +int do_change_label(int argc, char **argv);
> diff --git a/btrfslabel.c b/btrfslabel.c
> new file mode 100644
> index 0000000..c9f4684
> --- /dev/null
> +++ b/btrfslabel.c
> @@ -0,0 +1,121 @@
> +/*
> + * Copyright (C) 2008 Morey Roof.   All rights reserved.
> + *
> + * 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.
> + */
> +
> +#define _GNU_SOURCE
> +
> +#ifndef __CHECKER__
> +#include <sys/ioctl.h>
> +#include <sys/mount.h>
> +#include "ioctl.h"
> +#endif /* __CHECKER__ */
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <dirent.h>
> +#include <fcntl.h>
> +#include <unistd.h>
> +#include <linux/fs.h>
> +#include <linux/limits.h>
> +#include <ctype.h>
> +#include "kerncompat.h"
> +#include "ctree.h"
> +#include "utils.h"
> +#include "version.h"
> +#include "disk-io.h"
> +#include "transaction.h"
> +
> +#define MOUNTED                        1
> +#define UNMOUNTED                      2
> +#define GET_LABEL                      3
> +#define SET_LABEL                      4
> +
> +static void change_label_unmounted(char *dev, char *nLabel)
> +{
> +       struct btrfs_root *root;
> +       struct btrfs_trans_handle *trans;
> +
> +       /* Open the super_block at the default location
> +        * and as read-write.
> +        */
> +       root = open_ctree(dev, 0, 1);
> +
> +       trans = btrfs_start_transaction(root, 1);
> +       strncpy(root->fs_info->super_copy.label, nLabel,
BTRFS_LABEL_SIZE);
> +       btrfs_commit_transaction(trans, root);
> +
> +       /* Now we close it since we are done. */
> +       close_ctree(root);
> +}
> +
> +static void get_label_unmounted(char *dev)
> +{
> +       struct btrfs_root *root;
> +
> +       /* Open the super_block at the default location
> +        * and as read-only.
> +        */
> +       root = open_ctree(dev, 0, 0);
> +
> +       fprintf(stdout, "%s\n",
root->fs_info->super_copy.label);
> +
> +       /* Now we close it since we are done. */
> +       close_ctree(root);
> +}
> +
> +int get_label(char *btrfs_dev)
> +{
> +
> +	int ret;
> +	ret = check_mounted(btrfs_dev);
> +	if (ret < 0)
> +	{
> +	       fprintf(stderr, "FATAL: error checking %s mount
status\n",
> btrfs_dev);
> +	       return -1;
> +	}
> +
> +	if(ret != 0)
> +	{
> +	       fprintf(stderr, "FATAL: the filesystem has to be 
> unmounted\n");
> +	       return -2;
> +	}
> +	get_label_unmounted(btrfs_dev);
> +	return 0;
> +}
> +
> +
> +int set_label(char *btrfs_dev, char *nLabel)
> +{
> +
> +	int ret;
> +	ret = check_mounted(btrfs_dev);
> +	if (ret < 0)
> +	{
> +	       fprintf(stderr, "FATAL: error checking %s mount
status\n",
> btrfs_dev);
> +	       return -1;
> +	}
> +
> +	if(ret != 0)
> +	{
> +	       fprintf(stderr, "FATAL: the filesystem has to be 
> unmounted\n");
> +	       return -2;
> +	}
> +	change_label_unmounted(btrfs_dev, nLabel);
> +	return 0;
> +}
> diff --git a/btrfslabel.h b/btrfslabel.h
> new file mode 100644
> index 0000000..abf43ad
> --- /dev/null
> +++ b/btrfslabel.h
> @@ -0,0 +1,5 @@
> +/* btrflabel.h */
> +
> +
> +int get_label(char *btrfs_dev);
> +int set_label(char *btrfs_dev, char *nLabel);
> \ No newline at end of file
> diff --git a/man/btrfs.8.in b/man/btrfs.8.in
> index 26ef982..c1a8a42 100644
> --- a/man/btrfs.8.in
> +++ b/man/btrfs.8.in
> @@ -21,6 +21,8 @@ btrfs \- control a btrfs filesystem
>  .PP
>  \fBbtrfs\fP \fBfilesystem resize\fP\fI [+/\-]<size>[gkm]|max
<filesystem>\fP
>  .PP
> +\fBbtrfs\fP \fBfilesystem label\fP\fI <dev> [newlabel]\fP
> +.PP
>  \fBbtrfs\fP \fBdevice scan\fP\fI [<device> [<device>..]]\fP
>  .PP
>  \fBbtrfs\fP \fBdevice show\fP\fI <dev>|<label>
[<dev>|<label>...]\fP
> @@ -138,6 +140,23 @@ can expand the partition before enlarging the
filesystem
> and shrink the
>  partition after reducing the size of the filesystem.
>  .TP
>  
> +\fBbtrfs\fP \fBfilesystem label\fP\fI <dev> [newlabel]\fP
> +Show or update the label of a filesystem. \fI<dev>\fR is used to
identify
> the
> +filesystem. 
> +If a \fInewlabel\fR optional argument is passed, the label is changed. The
> +following costraints exist for a label:
> +.IP
> +- the maximum allowable lenght shall be less or equal than 256 chars
> +.IP
> +- the label shall not  contain the ''/'' or
''\\'' characters.
> +
> +NOTE: Currently there are the following limitations:
> +.IP
> +- the filesystem has to be unmounted
> +.IP
> +- the filesystem should not have more than one device.
> +.TP
> +
>  \fBfilesystem show\fR [<uuid>|<label>]\fR
>  Show the btrfs filesystem with some additional info. If no UUID or label
is
>  passed, \fBbtrfs\fR show info of all the btrfs filesystem.
> diff --git a/utils.c b/utils.c
> index 2f4c6e1..ea8e5b7 100644
> --- a/utils.c
> +++ b/utils.c
> @@ -587,7 +587,7 @@ error:
>  }
>  
>  /*
> - * returns 1 if the device was mounted, < 0 on error or 0 if everything
> + * returns 1 if the device is mounted, < 0 on error or 0 if everything
>   * is safe to continue.  TODO, this should also scan multi-device 
> filesystems
>   */
>  int check_mounted(char *file)
> @@ -638,6 +638,39 @@ int check_mounted(char *file)
>  	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];
> @@ -820,3 +853,27 @@ 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;
> +}
> diff --git a/utils.h b/utils.h
> index 7ff542b..838b65e 100644
> --- a/utils.h
> +++ b/utils.h
> @@ -40,4 +40,6 @@ int check_mounted(char *devicename);
>  int btrfs_device_already_in_root(struct btrfs_root *root, int fd,
>  				 int super_offset);
>  char *pretty_sizes(u64 size);
> +int check_label(char *input);
> +int get_mountpt(char *dev, char *mntpt, size_t size);
>  #endif
> 
> 
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On Mon, Sep 13, 2010 at 12:24 PM, Goffredo Baroncelli
<kreijack@gmail.com> wrote:
> +int get_label(char *btrfs_dev)
> +{
> +
> +       int ret;
> +       ret = check_mounted(btrfs_dev);
> +       if (ret < 0)
> +       {
> +              fprintf(stderr, "FATAL: error checking %s mount
status\n",
> btrfs_dev);
> +              return -1;
> +       }
> +
> +       if(ret != 0)
> +       {
> +              fprintf(stderr, "FATAL: the filesystem has to be
> unmounted\n");
> +              return -2;
> +       }
> +       get_label_unmounted(btrfs_dev);
> +       return 0;
> +}
> +
> +
Why can''t the label be read while the fs is mounted?  It
shouldn''t
hurt anything.  I can read the superblock on my ext3 fs while it''s
mounted...  This is what people have come to expect.
> --- a/utils.c
> +++ b/utils.c
> @@ -638,6 +638,39 @@ int check_mounted(char *file)
>        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.
> + */
Typo: s/fucntion/function/g

> +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];
> @@ -820,3 +853,27 @@ 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;
> +}
How can one char equal two chars?

input[i] == ''\\''

This should never be able to happen.  Right?
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Hi,

   > How can one char equal two chars?
   > 
   > input[i] == ''\\''

If the first char is the C escape sequence for string literals.  :)

- Chris.
-- 
Chris Ball   <cjb@laptop.org>   <http://printf.net/>
One Laptop Per Child
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On Wed, Sep 15, 2010 at 7:10 PM, Chris Ball <cjb@laptop.org>
wrote:
> Hi,
>
>   > How can one char equal two chars?
>   >
>   > input[i] == ''\\''
>
> If the first char is the C escape sequence for string literals.  :)
 Why are those characters forbidden in a label?
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On Thursday, 16 September, 2010, Mike Fedyk wrote:
> On Mon, Sep 13, 2010 at 12:24 PM, Goffredo Baroncelli
> <kreijack@gmail.com> wrote:
[...]
> > +
> > +       if(ret != 0)
> > +       {
> > +              fprintf(stderr, "FATAL: the filesystem has to be
> > unmounted\n");
> > +              return -2;
> > +       }
> > +       get_label_unmounted(btrfs_dev);
> > +       return 0;
> > +}
> > +
> > +
> 
> Why can''t the label be read while the fs is mounted?  It
shouldn''t
> hurt anything.  I can read the superblock on my ext3 fs while it''s
> mounted...  This is what people have come to expect.
The main reason is that if a filesystem is mounted, the data read from 
userspace may be outdated by the internal data.

In the original patch (the one of Morey Roof), there was a kernel space code 
that handled this case. In order to simplify the patch I split the code in two 
step the user space and the kernel space.

This is the user space portion, and because it has to work without the kernel 
space portion, when it is required the code fail explicitly.

I hope to publish the 2nd patch during the next weeks.

Regards
G.Baroncelli

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