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

lrwxrwxrwx 1 root root 4 Jun  4 13:36 /dev/whatever-i-like -> sdb2
/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 <jeffm@suse.com>
[use PATH_MAX in canonicalize_dm_name]
Signed-off-by: David Sterba <dsterba@suse.cz>

1 files changed, 47 insertions, 13 deletions

diff --git a/cmds-device.c b/cmds-device.c
index 29da661e..d7af0901 100644
--- a/cmds-device.c
+++ b/cmds-device.c
@@ -94,6 +94,7 @@ static int cmd_add_dev(int argc, char **argv)
 		int	devfd, res;
 		u64 dev_block_count = 0;
 		int mixed = 0;
+		char *path;
 
 		res = test_dev_for_mkfs(argv[i], force, estr);
 		if (res) {
@@ -117,15 +118,24 @@ static int cmd_add_dev(int argc, char **argv)
 			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:
@@ -241,6 +251,7 @@ static int cmd_scan_dev(int argc, char **argv)
 
 	for( i = devstart ; i < argc ; i++ ){
 		struct btrfs_ioctl_vol_args args;
+		char *path;
 
 		if (!is_block_device(argv[i])) {
 			fprintf(stderr,
@@ -248,9 +259,17 @@ static int cmd_scan_dev(int argc, char **argv)
 			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
@@ -261,9 +280,11 @@ static int cmd_scan_dev(int argc, char **argv)
 
 		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:
@@ -283,6 +304,7 @@ static int cmd_ready_dev(int argc, char **argv)
 	struct	btrfs_ioctl_vol_args args;
 	int	fd;
 	int	ret;
+	char	*path;
 
 	if (check_argc_min(argc, 2))
 		usage(cmd_ready_dev_usage);
@@ -292,22 +314,34 @@ static int cmd_ready_dev(int argc, char **argv)
 		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;
 }