btrfs-progs: canonicalize pathnames for device commands

PATCH In review Jeff Mahoney 3 participants 6 messages Jun 4, 2014 – Sep 24, 2014 Btrfs file system

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Jeff Mahoney

author

2014-06-04 20:41 UTC #0 lore raw

PATCH 1/1 btrfs-progs: canonicalize pathnames for device commands

mount(8) will canonicalize pathnames before passing them to the kernel. Links to e.g. /dev/sda will be resolved to /dev/sda. Links to /dev/dm-# will be resolved using the name of the device mapper table to /dev/mapper/<name>.

Btrfs will use whatever name the user passes to it, regardless of whether it is canonical or not. That means that if a 'btrfs device ready' is issued on any device node pointing to the original device, it will adopt the new name instead of the name that was used during mount.

Mounting using /dev/sdb2 will result in df:
/dev/sdb2 209715200 39328 207577088 1% /mnt

# ls -la /dev/whatever-i-like
lrwxrwxrwx 1 root root 4 Jun  4 13:36 /dev/whatever-i-like -> sdb2
# btrfs dev ready /dev/whatever-i-like
# df /mnt
/dev/whatever-i-like 209715200 39328 207577088   1% /mnt

Likewise, mounting with /dev/mapper/whatever and using /dev/dm-0 with a btrfs device command results in df showing /dev/dm-0. This can happen with multipath devices with friendly names enabled and doing something like 'partprobe' which (at least with our version) ends up issuing a 'change' uevent on the sysfs node. That *always* uses the dm-# name, and we get confused users.

This patch does the same canonicalization of the paths that mount does so that we don't end up having inconsistent names reported by ->show_devices later.

Signed-off-by Jeff Mahoney <[email protected]>

---
 cmds-device.c  |   60 ++++++++++++++++++++++++++++++++++++++++++++-------------
 cmds-replace.c |   13 ++++++++++--
 utils.c        |   57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 utils.h        |    2 +
 4 files changed, 117 insertions(+), 15 deletions(-)

cmds-device.c +47 ~~-13~~

@@ -95,6 +95,7 @@ static int cmd_add_dev(int argc, char **
 		int	devfd, res;
 		u64 dev_block_count = 0;
 		int mixed = 0;
+		char *path;
 
 		res = test_dev_for_mkfs(argv[i], force, estr);
 		if (res) {

@@ -118,15 +119,24 @@ static int cmd_add_dev(int argc, char **
 			goto error_out;
 		}
 
-		strncpy_null(ioctl_args.name, argv[i]);
+		path = canonicalize_path(argv[i]);
+		if (!path) {
+			fprintf(stderr,
+				"ERROR: Could not canonicalize pathname '%s': %s\n",
+				argv[i], strerror(errno));
+			ret++;
+			goto error_out;
+		}
+
+		strncpy_null(ioctl_args.name, path);
 		res = ioctl(fdmnt, BTRFS_IOC_ADD_DEV, &ioctl_args);
 		e = errno;
-		if(res<0){
+		if (res < 0) {
 			fprintf(stderr, "ERROR: error adding the device '%s' - %s\n",
-				argv[i], strerror(e));
+				path, strerror(e));
 			ret++;
 		}
-
+		free(path);
 	}
 
 error_out:

@@ -242,6 +252,7 @@ static int cmd_scan_dev(int argc, char *
 
 	for( i = devstart ; i < argc ; i++ ){
 		struct btrfs_ioctl_vol_args args;
+		char *path;
 
 		if (!is_block_device(argv[i])) {
 			fprintf(stderr,

@@ -249,9 +260,17 @@ static int cmd_scan_dev(int argc, char *
 			ret = 1;
 			goto close_out;
 		}
-		printf("Scanning for Btrfs filesystems in '%s'\n", argv[i]);
+		path = canonicalize_path(argv[i]);
+		if (!path) {
+			fprintf(stderr,
+				"ERROR: Could not canonicalize path '%s': %s\n",
+				argv[i], strerror(errno));
+			ret = 1;
+			goto close_out;
+		}
+		printf("Scanning for Btrfs filesystems in '%s'\n", path);
 
-		strncpy_null(args.name, argv[i]);
+		strncpy_null(args.name, path);
 		/*
 		 * FIXME: which are the error code returned by this ioctl ?
 		 * it seems that is impossible to understand if there no is

@@ -262,9 +281,11 @@ static int cmd_scan_dev(int argc, char *
 
 		if( ret < 0 ){
 			fprintf(stderr, "ERROR: unable to scan the device '%s' - %s\n",
-				argv[i], strerror(e));
+				path, strerror(e));
+			free(path);
 			goto close_out;
 		}
+		free(path);
 	}
 
 close_out:

@@ -284,6 +305,7 @@ static int cmd_ready_dev(int argc, char
 	struct	btrfs_ioctl_vol_args args;
 	int	fd;
 	int	ret;
+	char	*path;
 
 	if (check_argc_min(argc, 2))
 		usage(cmd_ready_dev_usage);

@@ -293,22 +315,34 @@ static int cmd_ready_dev(int argc, char
 		perror("failed to open /dev/btrfs-control");
 		return 1;
 	}
-	if (!is_block_device(argv[1])) {
+
+	path = canonicalize_path(argv[argc - 1]);
+	if (!path) {
 		fprintf(stderr,
-			"ERROR: %s is not a block device\n", argv[1]);
-		close(fd);
-		return 1;
+			"ERROR: Could not canonicalize pathname '%s': %s\n",
+			argv[argc - 1], strerror(errno));
+		ret = 1;
+		goto out;
 	}
 
-	strncpy(args.name, argv[argc - 1], BTRFS_PATH_NAME_MAX);
+	if (!is_block_device(path)) {
+		fprintf(stderr,
+			"ERROR: %s is not a block device\n", path);
+		ret = 1;
+		goto out;
+	}
+
+	strncpy(args.name, path, BTRFS_PATH_NAME_MAX);
 	ret = ioctl(fd, BTRFS_IOC_DEVICES_READY, &args);
 	if (ret < 0) {
 		fprintf(stderr, "ERROR: unable to determine if the device '%s'"
-			" is ready for mounting - %s\n", argv[argc - 1],
+			" is ready for mounting - %s\n", path,
 			strerror(errno));
 		ret = 1;
 	}
 
+out:
+	free(path);
 	close(fd);
 	return ret;
 }

cmds-replace.c +11 -2

@@ -134,7 +134,7 @@ static int cmd_start_replace(int argc, c
 	int fddstdev = -1;
 	char *path;
 	char *srcdev;
-	char *dstdev;
+	char *dstdev = NULL;
 	int avoid_reading_from_srcdev = 0;
 	int force_using_targetdev = 0;
 	struct stat st;

@@ -204,7 +204,12 @@ static int cmd_start_replace(int argc, c
 	}
 
 	srcdev = argv[optind];
-	dstdev = argv[optind + 1];
+	dstdev = canonicalize_path(argv[optind + 1]);
+	if (!dstdev) {
+		fprintf(stderr,
+			"ERROR: Could not canonicalize path '%s': %s\n",
+			argv[optind + 1], strerror(errno));
+	}
 
 	if (is_numerical(srcdev)) {
 		struct btrfs_ioctl_fs_info_args fi_args;

@@ -278,6 +283,8 @@ static int cmd_start_replace(int argc, c
 
 	close(fddstdev);
 	fddstdev = -1;
+	free(dstdev);
+	dstdev = NULL;
 
 	dev_replace_handle_sigint(fdmnt);
 	if (!do_not_background) {

@@ -312,6 +319,8 @@ static int cmd_start_replace(int argc, c
 	return 0;
 
 leave_with_error:
+	if (dstdev)
+		free(dstdev);
 	if (fdmnt != -1)
 		close(fdmnt);
 	if (fdsrcdev != -1)

utils.c +57 -0

63 lines not on this page · raw message

utils.h +2 -0

@@ -61,6 +61,8 @@ int btrfs_add_to_fsid(struct btrfs_trans
 int btrfs_scan_for_fsid(int run_ioctls);
 void btrfs_register_one_device(char *fname);
 int btrfs_scan_one_dir(char *dirname, int run_ioctl);
+char *canonicalize_dm_name(const char *ptname);
+char *canonicalize_path(const char *path);
 int check_mounted(const char *devicename);
 int check_mounted_where(int fd, const char *file, char *where, int size,
 			struct btrfs_fs_devices **fs_devices_mnt);

Signature · 2 lines

Jeff Mahoney
SUSE Labs

David Sterba

2014-06-18 16:32 UTC #1 lore raw

Quoted 5 lines · Jeff Mahoney

utils.c +0 -0

@@ -987,6 +987,63 @@ static int blk_file_in_dev_list(struct b
 }

utils.c static int blk_file_in_dev_list(struct b · line 998

Quoted 10 lines

utils.c +9 -0

 /*
+ * Resolve a pathname to a device mapper node to /dev/mapper/<name>
+ * Returns NULL on invalid input or malloc failure; Other failures
+ * will be handled by the caller using the input pathame.
+ */
+char *canonicalize_dm_name(const char *ptname)
+{
+	FILE	*f;
+	size_t	sz;
+	char	path[256], name[256], *res = NULL;

FYI, I've changed this to PATH_MAX

Anand Jain

2014-09-13 07:27 UTC #2 lore raw

In reply to Jeff Mahoney

Jeff,

Nice patch. However its better if we do this in the btrfs kernel function btrfs_scan_one_device(). Since the non-canonicalize path can still sneak through the btrfs specific mount option "device=".

Any comments ?

Thanks, Anand

Quoted 288 lines · Jeff Mahoney

Mounting using /dev/sdb2 will result in df:
/dev/sdb2 209715200 39328 207577088 1% /mnt

# ls -la /dev/whatever-i-like
lrwxrwxrwx 1 root root 4 Jun  4 13:36 /dev/whatever-i-like -> sdb2
# btrfs dev ready /dev/whatever-i-like
# df /mnt
/dev/whatever-i-like 209715200 39328 207577088   1% /mnt

This patch does the same canonicalization of the paths that mount does so that we don't end up having inconsistent names reported by ->show_devices later.

Signed-off-by Jeff Mahoney <[email protected]>

---
  cmds-device.c  |   60 ++++++++++++++++++++++++++++++++++++++++++++-------------
  cmds-replace.c |   13 ++++++++++--
  utils.c        |   57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
  utils.h        |    2 +
  4 files changed, 117 insertions(+), 15 deletions(-)

cmds-device.c +47 ~~-13~~

@@ -95,6 +95,7 @@ static int cmd_add_dev(int argc, char **
  		int	devfd, res;
  		u64 dev_block_count = 0;
  		int mixed = 0;
+		char *path;
 
  		res = test_dev_for_mkfs(argv[i], force, estr);
  		if (res) {

@@ -118,15 +119,24 @@ static int cmd_add_dev(int argc, char **
  			goto error_out;
  		}
 
-		strncpy_null(ioctl_args.name, argv[i]);
+		path = canonicalize_path(argv[i]);
+		if (!path) {
+			fprintf(stderr,
+				"ERROR: Could not canonicalize pathname '%s': %s\n",
+				argv[i], strerror(errno));
+			ret++;
+			goto error_out;
+		}
+
+		strncpy_null(ioctl_args.name, path);
  		res = ioctl(fdmnt, BTRFS_IOC_ADD_DEV, &ioctl_args);
  		e = errno;
-		if(res<0){
+		if (res < 0) {
  			fprintf(stderr, "ERROR: error adding the device '%s' - %s\n",
-				argv[i], strerror(e));
+				path, strerror(e));
  			ret++;
  		}
-
+		free(path);
  	}
 
  error_out:

@@ -242,6 +252,7 @@ static int cmd_scan_dev(int argc, char *
 
  	for( i = devstart ; i < argc ; i++ ){
  		struct btrfs_ioctl_vol_args args;
+		char *path;
 
  		if (!is_block_device(argv[i])) {
  			fprintf(stderr,

@@ -249,9 +260,17 @@ static int cmd_scan_dev(int argc, char *
  			ret = 1;
  			goto close_out;
  		}
-		printf("Scanning for Btrfs filesystems in '%s'\n", argv[i]);
+		path = canonicalize_path(argv[i]);
+		if (!path) {
+			fprintf(stderr,
+				"ERROR: Could not canonicalize path '%s': %s\n",
+				argv[i], strerror(errno));
+			ret = 1;
+			goto close_out;
+		}
+		printf("Scanning for Btrfs filesystems in '%s'\n", path);
 
-		strncpy_null(args.name, argv[i]);
+		strncpy_null(args.name, path);
  		/*
  		 * FIXME: which are the error code returned by this ioctl ?
  		 * it seems that is impossible to understand if there no is

@@ -262,9 +281,11 @@ static int cmd_scan_dev(int argc, char *
 
  		if( ret < 0 ){
  			fprintf(stderr, "ERROR: unable to scan the device '%s' - %s\n",
-				argv[i], strerror(e));
+				path, strerror(e));
+			free(path);
  			goto close_out;
  		}
+		free(path);
  	}
 
  close_out:

@@ -284,6 +305,7 @@ static int cmd_ready_dev(int argc, char
  	struct	btrfs_ioctl_vol_args args;
  	int	fd;
  	int	ret;
+	char	*path;
 
  	if (check_argc_min(argc, 2))
  		usage(cmd_ready_dev_usage);

@@ -293,22 +315,34 @@ static int cmd_ready_dev(int argc, char
  		perror("failed to open /dev/btrfs-control");
  		return 1;
  	}
-	if (!is_block_device(argv[1])) {
+
+	path = canonicalize_path(argv[argc - 1]);
+	if (!path) {
  		fprintf(stderr,
-			"ERROR: %s is not a block device\n", argv[1]);
-		close(fd);
-		return 1;
+			"ERROR: Could not canonicalize pathname '%s': %s\n",
+			argv[argc - 1], strerror(errno));
+		ret = 1;
+		goto out;
  	}
 
-	strncpy(args.name, argv[argc - 1], BTRFS_PATH_NAME_MAX);
+	if (!is_block_device(path)) {
+		fprintf(stderr,
+			"ERROR: %s is not a block device\n", path);
+		ret = 1;
+		goto out;
+	}
+
+	strncpy(args.name, path, BTRFS_PATH_NAME_MAX);
  	ret = ioctl(fd, BTRFS_IOC_DEVICES_READY, &args);
  	if (ret < 0) {
  		fprintf(stderr, "ERROR: unable to determine if the device '%s'"
-			" is ready for mounting - %s\n", argv[argc - 1],
+			" is ready for mounting - %s\n", path,
  			strerror(errno));
  		ret = 1;
  	}
 
+out:
+	free(path);
  	close(fd);
  	return ret;
  }

cmds-replace.c +11 -2

@@ -134,7 +134,7 @@ static int cmd_start_replace(int argc, c
  	int fddstdev = -1;
  	char *path;
  	char *srcdev;
-	char *dstdev;
+	char *dstdev = NULL;
  	int avoid_reading_from_srcdev = 0;
  	int force_using_targetdev = 0;
  	struct stat st;

@@ -204,7 +204,12 @@ static int cmd_start_replace(int argc, c
  	}
 
  	srcdev = argv[optind];
-	dstdev = argv[optind + 1];
+	dstdev = canonicalize_path(argv[optind + 1]);
+	if (!dstdev) {
+		fprintf(stderr,
+			"ERROR: Could not canonicalize path '%s': %s\n",
+			argv[optind + 1], strerror(errno));
+	}
 
  	if (is_numerical(srcdev)) {
  		struct btrfs_ioctl_fs_info_args fi_args;

@@ -278,6 +283,8 @@ static int cmd_start_replace(int argc, c
 
  	close(fddstdev);
  	fddstdev = -1;
+	free(dstdev);
+	dstdev = NULL;
 
  	dev_replace_handle_sigint(fdmnt);
  	if (!do_not_background) {

@@ -312,6 +319,8 @@ static int cmd_start_replace(int argc, c
  	return 0;
 
  leave_with_error:
+	if (dstdev)
+		free(dstdev);
  	if (fdmnt != -1)
  		close(fdmnt);
  	if (fdsrcdev != -1)

utils.c +57 -0

@@ -987,6 +987,63 @@ static int blk_file_in_dev_list(struct b
  }
 
  /*
+ * Resolve a pathname to a device mapper node to /dev/mapper/<name>
+ * Returns NULL on invalid input or malloc failure; Other failures
+ * will be handled by the caller using the input pathame.
+ */
+char *canonicalize_dm_name(const char *ptname)
+{
+	FILE	*f;
+	size_t	sz;
+	char	path[256], name[256], *res = NULL;
+
+	if (!ptname || !*ptname)
+		return NULL;
+
+	snprintf(path, sizeof(path), "/sys/block/%s/dm/name", ptname);
+	if (!(f = fopen(path, "r")))
+		return NULL;
+
+	/* read <name>\n from sysfs */
+	if (fgets(name, sizeof(name), f) && (sz = strlen(name)) > 1) {
+		name[sz - 1] = '\0';
+		snprintf(path, sizeof(path), "/dev/mapper/%s", name);
+
+		if (access(path, F_OK) == 0)
+			res = strdup(path);
+	}
+	fclose(f);
+	return res;
+}
+
+/*
+ * Resolve a pathname to a canonical device node, e.g. /dev/sda1 or
+ * to a device mapper pathname.
+ * Returns NULL on invalid input or malloc failure; Other failures
+ * will be handled by the caller using the input pathame.
+ */
+char *canonicalize_path(const char *path)
+{
+	char *canonical, *p;
+
+	if (!path || !*path)
+		return NULL;
+
+	canonical = realpath(path, NULL);
+	if (!canonical)
+		return strdup(path);
+	p = strrchr(canonical, '/');
+	if (p && strncmp(p, "/dm-", 4) == 0 && isdigit(*(p + 4))) {
+		char *dm = canonicalize_dm_name(p + 1);
+		if (dm) {
+			free(canonical);
+			return dm;
+		}
+	}
+	return canonical;
+}
+
+/*
   * returns 1 if the device was mounted, < 0 on error or 0 if everything
   * is safe to continue.
   */

utils.h +2 -0

@@ -61,6 +61,8 @@ int btrfs_add_to_fsid(struct btrfs_trans
  int btrfs_scan_for_fsid(int run_ioctls);
  void btrfs_register_one_device(char *fname);
  int btrfs_scan_one_dir(char *dirname, int run_ioctl);
+char *canonicalize_dm_name(const char *ptname);
+char *canonicalize_path(const char *path);
  int check_mounted(const char *devicename);
  int check_mounted_where(int fd, const char *file, char *where, int size,
  			struct btrfs_fs_devices **fs_devices_mnt);

Jeff Mahoney

author

2014-09-14 22:47 UTC #3 lore raw

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Quoted 9 lines · Anand Jain

Jeff,
Nice patch. However its better if we do this in the btrfs kernel function btrfs_scan_one_device(). Since the non-canonicalize path can still sneak through the btrfs specific mount option "device=".
Any comments ?

My initial reaction is to avoid playing naming names within the kernel. But since it's device mapper-specific, it might not be too messy to do that. In addition to the patch to the progs, we're also carrying a patch to systemd since it has it's own little ioctl wrapper to do the scanning. It needed to be fixed there as well.

- -Jeff

Quoted 175 lines

Thanks, Anand
Quoted 170 lines · Jeff Mahoney
mount(8) will canonicalize pathnames before passing them to the kernel. Links to e.g. /dev/sda will be resolved to /dev/sda. Links to /dev/dm-# will be resolved using the name of the device mapper table to /dev/mapper/<name>.
Btrfs will use whatever name the user passes to it, regardless of whether it is canonical or not. That means that if a 'btrfs device ready' is issued on any device node pointing to the original device, it will adopt the new name instead of the name that was used during mount.
Mounting using /dev/sdb2 will result in df: /dev/sdb2
209715200 39328 207577088 1% /mnt
# ls -la /dev/whatever-i-like lrwxrwxrwx 1 root root 4 Jun  4
13:36 /dev/whatever-i-like -> sdb2 # btrfs dev ready
/dev/whatever-i-like # df /mnt /dev/whatever-i-like 209715200
39328 207577088   1% /mnt
Likewise, mounting with /dev/mapper/whatever and using /dev/dm-0 with a btrfs device command results in df showing /dev/dm-0. This can happen with multipath devices with friendly names enabled and doing something like 'partprobe' which (at least with our version) ends up issuing a 'change' uevent on the sysfs node. That *always* uses the dm-# name, and we get confused users.
This patch does the same canonicalization of the paths that mount does so that we don't end up having inconsistent names reported by ->show_devices later.
Signed-off-by Jeff Mahoney <[email protected]> --- cmds-device.c |
60 ++++++++++++++++++++++++++++++++++++++++++++-------------
cmds-replace.c | 13 ++++++++++-- utils.c | 57
++++++++++++++++++++++++++++++++++++++++++++++++++++++ utils.h
| 2 + 4 files changed, 117 insertions(+), 15 deletions(-)
--- a/cmds-device.c +++ b/cmds-device.c @@ -95,6 +95,7 @@ static
int cmd_add_dev(int argc, char ** int devfd, res; u64
dev_block_count = 0; int mixed = 0; + char *path;
res = test_dev_for_mkfs(argv[i], force, estr); if (res) { @@ -118,15 +119,24 @@ static int cmd_add_dev(int argc, char ** goto error_out; }
- strncpy_null(ioctl_args.name, argv[i]); + path =
canonicalize_path(argv[i]); + if (!path) { +
fprintf(stderr, + "ERROR: Could not canonicalize
pathname '%s': %s\n", + argv[i],
strerror(errno)); + ret++; + goto
error_out; + } + + strncpy_null(ioctl_args.name,
path); res = ioctl(fdmnt, BTRFS_IOC_ADD_DEV, &ioctl_args); e =
errno; - if(res<0){ + if (res < 0) {
fprintf(stderr, "ERROR: error adding the device '%s' - %s\n", -
argv[i], strerror(e)); + path, strerror(e));
ret++; } - + free(path); }
error_out: @@ -242,6 +252,7 @@ static int cmd_scan_dev(int argc, char *
for( i = devstart ; i < argc ; i++ ){ struct btrfs_ioctl_vol_args
args; + char *path;
if (!is_block_device(argv[i])) { fprintf(stderr, @@ -249,9 +260,17 @@ static int cmd_scan_dev(int argc, char * ret = 1; goto
close_out; } - printf("Scanning for Btrfs filesystems in
'%s'\n", argv[i]); + path = canonicalize_path(argv[i]); +
if (!path) { + fprintf(stderr, +
"ERROR: Could not canonicalize path '%s': %s\n", +
argv[i], strerror(errno)); + ret = 1; +
goto close_out; + } + printf("Scanning for Btrfs
filesystems in '%s'\n", path);
- strncpy_null(args.name, argv[i]); +
strncpy_null(args.name, path); /* * FIXME: which are the error code returned by this ioctl ? * it seems that is impossible to understand if there no is @@ -262,9 +281,11 @@ static int cmd_scan_dev(int argc, char *
if( ret < 0 ){ fprintf(stderr, "ERROR: unable to scan the device
'%s' - %s\n", - argv[i], strerror(e)); +
path, strerror(e)); + free(path); goto close_out; } +
free(path); }
close_out: @@ -284,6 +305,7 @@ static int cmd_ready_dev(int argc,
char struct btrfs_ioctl_vol_args args; int fd; int ret;
+ char *path;
if (check_argc_min(argc, 2)) usage(cmd_ready_dev_usage); @@ -293,22 +315,34 @@ static int cmd_ready_dev(int argc, char
perror("failed to open /dev/btrfs-control"); return 1; } - if
(!is_block_device(argv[1])) { + + path =
canonicalize_path(argv[argc - 1]); + if (!path) {
fprintf(stderr, - "ERROR: %s is not a block device\n",
argv[1]); - close(fd); - return 1; +
"ERROR: Could not canonicalize pathname '%s': %s\n", +
argv[argc - 1], strerror(errno)); + ret = 1; + goto
out; }
- strncpy(args.name, argv[argc - 1], BTRFS_PATH_NAME_MAX); +
if (!is_block_device(path)) { + fprintf(stderr, +
"ERROR: %s is not a block device\n", path); + ret = 1; +
goto out; + } + + strncpy(args.name, path,
BTRFS_PATH_NAME_MAX); ret = ioctl(fd, BTRFS_IOC_DEVICES_READY, &args); if (ret < 0) { fprintf(stderr, "ERROR: unable to
determine if the device '%s'" - " is ready for
mounting - %s\n", argv[argc - 1], + " is ready for
mounting - %s\n", path, strerror(errno)); ret = 1; }
+out: + free(path); close(fd); return ret; } ---
a/cmds-replace.c +++ b/cmds-replace.c @@ -134,7 +134,7 @@ static int cmd_start_replace(int argc, c int fddstdev = -1; char *path;
char *srcdev; - char *dstdev; + char *dstdev = NULL; int
avoid_reading_from_srcdev = 0; int force_using_targetdev = 0; struct stat st; @@ -204,7 +204,12 @@ static int cmd_start_replace(int argc, c }
srcdev = argv[optind]; - dstdev = argv[optind + 1]; +
dstdev = canonicalize_path(argv[optind + 1]); + if (!dstdev)
{ + fprintf(stderr, + "ERROR: Could not
canonicalize path '%s': %s\n", + argv[optind + 1],
strerror(errno)); + }
if (is_numerical(srcdev)) { struct btrfs_ioctl_fs_info_args fi_args; @@ -278,6 +283,8 @@ static int cmd_start_replace(int argc, c
close(fddstdev); fddstdev = -1; + free(dstdev); + dstdev =
NULL;
dev_replace_handle_sigint(fdmnt); if (!do_not_background) { @@ -312,6 +319,8 @@ static int cmd_start_replace(int argc, c return 0;
leave_with_error: + if (dstdev) + free(dstdev); if
(fdmnt != -1) close(fdmnt); if (fdsrcdev != -1) --- a/utils.c +++ b/utils.c @@ -987,6 +987,63 @@ static int blk_file_in_dev_list(struct b }
/* + * Resolve a pathname to a device mapper node to /dev/mapper/<name> + * Returns NULL on invalid input or malloc failure; Other failures + * will be handled by the caller using the input pathame. + */ +char *canonicalize_dm_name(const char
*ptname) +{ + FILE *f; + size_t sz; + char
path[256], name[256], *res = NULL; + + if (!ptname ||
!*ptname) + return NULL; + + snprintf(path,
sizeof(path), "/sys/block/%s/dm/name", ptname); + if (!(f =
fopen(path, "r"))) + return NULL; + + /* read <name>\n
from sysfs */ + if (fgets(name, sizeof(name), f) && (sz =
strlen(name)) > 1) { + name[sz - 1] = '\0'; +
snprintf(path, sizeof(path), "/dev/mapper/%s", name); + +
if (access(path, F_OK) == 0) + res = strdup(path); +
} + fclose(f); + return res; +} + +/* + * Resolve a
pathname to a canonical device node, e.g. /dev/sda1 or + * to a device mapper pathname. + * Returns NULL on invalid input or malloc failure; Other failures + * will be handled by the caller using the input pathame. + */ +char *canonicalize_path(const char
*path) +{ + char *canonical, *p; + + if (!path || !*path) +
return NULL; + + canonical = realpath(path, NULL); + if
(!canonical) + return strdup(path); + p =
strrchr(canonical, '/'); + if (p && strncmp(p, "/dm-", 4) == 0
&& isdigit(*(p + 4))) { + char *dm =
canonicalize_dm_name(p + 1); + if (dm) { +
free(canonical); + return dm; + } + } +
return canonical; +} + +/* * returns 1 if the device was mounted, < 0 on error or 0 if everything * is safe to continue. */ --- a/utils.h +++ b/utils.h @@ -61,6 +61,8 @@ int btrfs_add_to_fsid(struct btrfs_trans int btrfs_scan_for_fsid(int run_ioctls); void btrfs_register_one_device(char *fname); int btrfs_scan_one_dir(char *dirname, int run_ioctl); +char *canonicalize_dm_name(const char *ptname); +char

Quoted 9 lines

Quoted 5 lines
*canonicalize_path(const char *path); int check_mounted(const char *devicename); int check_mounted_where(int fd, const char *file, char *where, int size, struct btrfs_fs_devices **fs_devices_mnt);
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- --
Jeff Mahoney
SUSE Labs
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Anand Jain

2014-09-15 18:02 UTC #4 lore raw

Quoted 12 lines · Jeff Mahoney

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
Quoted 8 lines · Anand Jain
Jeff,
Nice patch. However its better if we do this in the btrfs kernel function btrfs_scan_one_device(). Since the non-canonicalize path can still sneak through the btrfs specific mount option "device=".

Quoted 7 lines

Quoted 1 line
Any comments ?
My initial reaction is to avoid playing naming names within the kernel. But since it's device mapper-specific, it might not be too messy to do that. In addition to the patch to the progs, we're also carrying a patch to systemd since it has it's own little ioctl wrapper to do the scanning. It needed to be fixed there as well.

looks like we need to fix systemd as well. As I check systemd is using READY ioctl.

Thanks, Anand

Quoted 214 lines

- -Jeff
Quoted 175 lines
Thanks, Anand
Quoted 170 lines · Jeff Mahoney
mount(8) will canonicalize pathnames before passing them to the kernel. Links to e.g. /dev/sda will be resolved to /dev/sda. Links to /dev/dm-# will be resolved using the name of the device mapper table to /dev/mapper/<name>.
Btrfs will use whatever name the user passes to it, regardless of whether it is canonical or not. That means that if a 'btrfs device ready' is issued on any device node pointing to the original device, it will adopt the new name instead of the name that was used during mount.
Mounting using /dev/sdb2 will result in df: /dev/sdb2
209715200 39328 207577088 1% /mnt
# ls -la /dev/whatever-i-like lrwxrwxrwx 1 root root 4 Jun  4
13:36 /dev/whatever-i-like -> sdb2 # btrfs dev ready
/dev/whatever-i-like # df /mnt /dev/whatever-i-like 209715200
39328 207577088   1% /mnt
Likewise, mounting with /dev/mapper/whatever and using /dev/dm-0 with a btrfs device command results in df showing /dev/dm-0. This can happen with multipath devices with friendly names enabled and doing something like 'partprobe' which (at least with our version) ends up issuing a 'change' uevent on the sysfs node. That *always* uses the dm-# name, and we get confused users.
This patch does the same canonicalization of the paths that mount does so that we don't end up having inconsistent names reported by ->show_devices later.
Signed-off-by Jeff Mahoney <[email protected]> --- cmds-device.c |
60 ++++++++++++++++++++++++++++++++++++++++++++-------------
cmds-replace.c | 13 ++++++++++-- utils.c | 57
++++++++++++++++++++++++++++++++++++++++++++++++++++++ utils.h
| 2 + 4 files changed, 117 insertions(+), 15 deletions(-)
--- a/cmds-device.c +++ b/cmds-device.c @@ -95,6 +95,7 @@ static
int cmd_add_dev(int argc, char ** int devfd, res; u64
dev_block_count = 0; int mixed = 0; + char *path;
res = test_dev_for_mkfs(argv[i], force, estr); if (res) { @@ -118,15 +119,24 @@ static int cmd_add_dev(int argc, char ** goto error_out; }
- strncpy_null(ioctl_args.name, argv[i]); + path =
canonicalize_path(argv[i]); + if (!path) { +
fprintf(stderr, + "ERROR: Could not canonicalize
pathname '%s': %s\n", + argv[i],
strerror(errno)); + ret++; + goto
error_out; + } + + strncpy_null(ioctl_args.name,
path); res = ioctl(fdmnt, BTRFS_IOC_ADD_DEV, &ioctl_args); e =
errno; - if(res<0){ + if (res < 0) {
fprintf(stderr, "ERROR: error adding the device '%s' - %s\n", -
argv[i], strerror(e)); + path, strerror(e));
ret++; } - + free(path); }
error_out: @@ -242,6 +252,7 @@ static int cmd_scan_dev(int argc, char *
for( i = devstart ; i < argc ; i++ ){ struct btrfs_ioctl_vol_args
args; + char *path;
if (!is_block_device(argv[i])) { fprintf(stderr, @@ -249,9 +260,17 @@ static int cmd_scan_dev(int argc, char * ret = 1; goto
close_out; } - printf("Scanning for Btrfs filesystems in
'%s'\n", argv[i]); + path = canonicalize_path(argv[i]); +
if (!path) { + fprintf(stderr, +
"ERROR: Could not canonicalize path '%s': %s\n", +
argv[i], strerror(errno)); + ret = 1; +
goto close_out; + } + printf("Scanning for Btrfs
filesystems in '%s'\n", path);
- strncpy_null(args.name, argv[i]); +
strncpy_null(args.name, path); /* * FIXME: which are the error code returned by this ioctl ? * it seems that is impossible to understand if there no is @@ -262,9 +281,11 @@ static int cmd_scan_dev(int argc, char *
if( ret < 0 ){ fprintf(stderr, "ERROR: unable to scan the device
'%s' - %s\n", - argv[i], strerror(e)); +
path, strerror(e)); + free(path); goto close_out; } +
free(path); }
close_out: @@ -284,6 +305,7 @@ static int cmd_ready_dev(int argc,
char struct btrfs_ioctl_vol_args args; int fd; int ret;
+ char *path;
if (check_argc_min(argc, 2)) usage(cmd_ready_dev_usage); @@ -293,22 +315,34 @@ static int cmd_ready_dev(int argc, char
perror("failed to open /dev/btrfs-control"); return 1; } - if
(!is_block_device(argv[1])) { + + path =
canonicalize_path(argv[argc - 1]); + if (!path) {
fprintf(stderr, - "ERROR: %s is not a block device\n",
argv[1]); - close(fd); - return 1; +
"ERROR: Could not canonicalize pathname '%s': %s\n", +
argv[argc - 1], strerror(errno)); + ret = 1; + goto
out; }
- strncpy(args.name, argv[argc - 1], BTRFS_PATH_NAME_MAX); +
if (!is_block_device(path)) { + fprintf(stderr, +
"ERROR: %s is not a block device\n", path); + ret = 1; +
goto out; + } + + strncpy(args.name, path,
BTRFS_PATH_NAME_MAX); ret = ioctl(fd, BTRFS_IOC_DEVICES_READY, &args); if (ret < 0) { fprintf(stderr, "ERROR: unable to
determine if the device '%s'" - " is ready for
mounting - %s\n", argv[argc - 1], + " is ready for
mounting - %s\n", path, strerror(errno)); ret = 1; }
+out: + free(path); close(fd); return ret; } ---
a/cmds-replace.c +++ b/cmds-replace.c @@ -134,7 +134,7 @@ static int cmd_start_replace(int argc, c int fddstdev = -1; char *path;
char *srcdev; - char *dstdev; + char *dstdev = NULL; int
avoid_reading_from_srcdev = 0; int force_using_targetdev = 0; struct stat st; @@ -204,7 +204,12 @@ static int cmd_start_replace(int argc, c }
srcdev = argv[optind]; - dstdev = argv[optind + 1]; +
dstdev = canonicalize_path(argv[optind + 1]); + if (!dstdev)
{ + fprintf(stderr, + "ERROR: Could not
canonicalize path '%s': %s\n", + argv[optind + 1],
strerror(errno)); + }
if (is_numerical(srcdev)) { struct btrfs_ioctl_fs_info_args fi_args; @@ -278,6 +283,8 @@ static int cmd_start_replace(int argc, c
close(fddstdev); fddstdev = -1; + free(dstdev); + dstdev =
NULL;
dev_replace_handle_sigint(fdmnt); if (!do_not_background) { @@ -312,6 +319,8 @@ static int cmd_start_replace(int argc, c return 0;
leave_with_error: + if (dstdev) + free(dstdev); if
(fdmnt != -1) close(fdmnt); if (fdsrcdev != -1) --- a/utils.c +++ b/utils.c @@ -987,6 +987,63 @@ static int blk_file_in_dev_list(struct b }
/* + * Resolve a pathname to a device mapper node to /dev/mapper/<name> + * Returns NULL on invalid input or malloc failure; Other failures + * will be handled by the caller using the input pathame. + */ +char *canonicalize_dm_name(const char
*ptname) +{ + FILE *f; + size_t sz; + char
path[256], name[256], *res = NULL; + + if (!ptname ||
!*ptname) + return NULL; + + snprintf(path,
sizeof(path), "/sys/block/%s/dm/name", ptname); + if (!(f =
fopen(path, "r"))) + return NULL; + + /* read <name>\n
from sysfs */ + if (fgets(name, sizeof(name), f) && (sz =
strlen(name)) > 1) { + name[sz - 1] = '\0'; +
snprintf(path, sizeof(path), "/dev/mapper/%s", name); + +
if (access(path, F_OK) == 0) + res = strdup(path); +
} + fclose(f); + return res; +} + +/* + * Resolve a
pathname to a canonical device node, e.g. /dev/sda1 or + * to a device mapper pathname. + * Returns NULL on invalid input or malloc failure; Other failures + * will be handled by the caller using the input pathame. + */ +char *canonicalize_path(const char
*path) +{ + char *canonical, *p; + + if (!path || !*path) +
return NULL; + + canonical = realpath(path, NULL); + if
(!canonical) + return strdup(path); + p =
strrchr(canonical, '/'); + if (p && strncmp(p, "/dm-", 4) == 0
&& isdigit(*(p + 4))) { + char *dm =
canonicalize_dm_name(p + 1); + if (dm) { +
free(canonical); + return dm; + } + } +
return canonical; +} + +/* * returns 1 if the device was mounted, < 0 on error or 0 if everything * is safe to continue. */ --- a/utils.h +++ b/utils.h @@ -61,6 +61,8 @@ int btrfs_add_to_fsid(struct btrfs_trans int btrfs_scan_for_fsid(int run_ioctls); void btrfs_register_one_device(char *fname); int btrfs_scan_one_dir(char *dirname, int run_ioctl); +char *canonicalize_dm_name(const char *ptname); +char
Quoted 9 lines
Quoted 5 lines
*canonicalize_path(const char *path); int check_mounted(const char *devicename); int check_mounted_where(int fd, const char *file, char *where, int size, struct btrfs_fs_devices **fs_devices_mnt);
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Jeff Mahoney
SUSE Labs
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Anand Jain

2014-09-24 06:33 UTC #5 lore raw

Quoted 7 lines

Quoted 7 lines
Quoted 6 lines
Nice patch. However its better if we do this in the btrfs kernel function btrfs_scan_one_device(). Since the non-canonicalize path can still sneak through the btrfs specific mount option "device=".
Any comments ?

Quoted 8 lines

Quoted 5 lines
My initial reaction is to avoid playing naming names within the kernel. But since it's device mapper-specific, it might not be too messy to do that. In addition to the patch to the progs, we're also carrying a patch to systemd since it has it's own little ioctl wrapper to do the scanning. It needed to be fixed there as well.
looks like we need to fix systemd as well. As I check systemd is using READY ioctl.

systemd is using device ready ioctl's bug as a feature (if the comment in systemd is true, as below).

./systemd/rules/64-btrfs.rules
----

# let the kernel know about this btrfs filesystem, and check if it is complete
IMPORT{builtin}="btrfs ready $devnode"
----

btrfs dev ready is only to check if the device is ready, not to let the kernel know about it. the bug part in the ioctl is it would update the device path, even when the device is mounted.

Either we need transition the bug as a feature OR fix the bug.

-Anand