Re: PATCH V3] mkfs.btrfs: allow UUID specification at mkfs time

[Goffredo Baroncelli <kreijack@libero.it>]

On 05/14/2014 07:39 PM, Eric Sandeen wrote:
> Allow the specification of the filesystem UUID at mkfs time.
> 
> Non-unique unique IDs are rejected.  This includes attempting
> to re-mkfs with the same UUID; if you really want to do that,
> you can mkfs with a new UUID, then re-mkfs with the one you
> wanted.  ;)
> 
> (Implemented only for mkfs.btrfs, not btrfs-convert).
> 
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---
> 
> NB: the prior patch didn't work well if you re-mkfs'd with
> the same UUID; to be honest I didn't get to the bottom of it,
> but the fact that that old UUID was already in an internal
> list of present devices seems to have confused things.
> 
> V2: reject non-unique unique IDs.
> V3: test for non-unique unique IDs early in mkfs.
> 
> diff --git a/btrfs-convert.c b/btrfs-convert.c
> index a8b2c51..d62d4f8 100644
> --- a/btrfs-convert.c
> +++ b/btrfs-convert.c
> @@ -2240,7 +2240,7 @@ static int do_convert(const char *devname, int datacsum, int packing,
>  		goto fail;
>  	}
>  	ret = make_btrfs(fd, devname, ext2_fs->super->s_volume_name,
> -			 blocks, total_bytes, blocksize, blocksize,
> +			 NULL, blocks, total_bytes, blocksize, blocksize,
>  			 blocksize, blocksize, 0);
>  	if (ret) {
>  		fprintf(stderr, "unable to create initial ctree: %s\n",
> diff --git a/man/mkfs.btrfs.8.in b/man/mkfs.btrfs.8.in
> index bef509d..4450d03 100644
> --- a/man/mkfs.btrfs.8.in
> +++ b/man/mkfs.btrfs.8.in
> @@ -16,6 +16,7 @@ mkfs.btrfs \- create a btrfs filesystem
>  [ \fB\-r\fP\fI rootdir\fP ]
>  [ \fB\-K\fP ]
>  [ \fB\-O\fP\fI feature1,feature2,...\fP ]
> +[ \fB\-U\fP\fI uuid\fP ]
>  [ \fB\-h\fP ]
>  [ \fB\-V\fP ]
>  \fI device\fP [ \fIdevice ...\fP ]
> @@ -90,6 +91,9 @@ To see all run
>  
>  \fBmkfs.btrfs -O list-all\fR
>  .TP
> +\fB\-U\fR, \fB\-\-uuid \fR
> +Create the filesystem with the specified UUID, which must not already exist on the system.
> +.TP
>  \fB\-V\fR, \fB\-\-version\fR
>  Print the \fBmkfs.btrfs\fP version and exit.
>  .SH UNIT
> diff --git a/mkfs.c b/mkfs.c
> index dbd83f5..d67a5ba 100644
> --- a/mkfs.c
> +++ b/mkfs.c
> @@ -288,6 +288,7 @@ static void print_usage(void)
>  	fprintf(stderr, "\t -r --rootdir the source directory\n");
>  	fprintf(stderr, "\t -K --nodiscard do not perform whole device TRIM\n");
>  	fprintf(stderr, "\t -O --features comma separated list of filesystem features\n");
> +	fprintf(stderr, "\t -U --uuid specify the filesystem UUID\n");
>  	fprintf(stderr, "\t -V --version print the mkfs.btrfs version and exit\n");
>  	fprintf(stderr, "%s\n", BTRFS_BUILD_VERSION);
>  	exit(1);
> @@ -351,6 +352,7 @@ static struct option long_options[] = {
>  	{ "rootdir", 1, NULL, 'r' },
>  	{ "nodiscard", 0, NULL, 'K' },
>  	{ "features", 0, NULL, 'O' },
> +	{ "uuid", 0, NULL, 'U' },
>  	{ NULL, 0, NULL, 0}
>  };
>  
> @@ -1273,11 +1275,12 @@ int main(int ac, char **av)
>  	int dev_cnt = 0;
>  	int saved_optind;
>  	char estr[100];
> +	char *fs_uuid = NULL;
>  	u64 features = DEFAULT_MKFS_FEATURES;
>  
>  	while(1) {
>  		int c;
> -		c = getopt_long(ac, av, "A:b:fl:n:s:m:d:L:O:r:VMK",
> +		c = getopt_long(ac, av, "A:b:fl:n:s:m:d:L:O:r:U:VMK",
>  				long_options, &option_index);
>  		if (c < 0)
>  			break;
> @@ -1346,6 +1349,9 @@ int main(int ac, char **av)
>  				source_dir = optarg;
>  				source_dir_set = 1;
>  				break;
> +			case 'U':
> +				fs_uuid = optarg;
> +				break;
>  			case 'K':
>  				discard = 0;
>  				break;
> @@ -1368,6 +1374,20 @@ int main(int ac, char **av)
>  			"The -r option is limited to a single device\n");
>  		exit(1);
>  	}
> +
> +	if (fs_uuid) {
> +		uuid_t dummy_uuid;
> +
> +		if (uuid_parse(fs_uuid, dummy_uuid) != 0) {
> +			fprintf(stderr, "could not parse UUID: %s\n", fs_uuid);
> +			exit(1);
> +		}
> +		if (!test_uuid_unique(fs_uuid)) {
> +			fprintf(stderr, "non-unique UUID: %s\n", fs_uuid);
> +			exit(1);
> +		}

My test showed that this detect a false positive when the user tries to mkfs two time on the same device with the same uuid.

> +	}
> +	
>  	while (dev_cnt-- > 0) {
>  		file = av[optind++];
>  		if (is_block_device(file))
> @@ -1514,7 +1534,7 @@ int main(int ac, char **av)
>  
>  	process_fs_features(features);
>  
> -	ret = make_btrfs(fd, file, label, blocks, dev_block_count,
> +	ret = make_btrfs(fd, file, label, fs_uuid, blocks, dev_block_count,
>  			 nodesize, leafsize,
>  			 sectorsize, stripesize, features);
>  	if (ret) {
> diff --git a/utils.c b/utils.c
> index 3e9c527..cfac0d4 100644
> --- a/utils.c
> +++ b/utils.c
> @@ -93,12 +93,41 @@ static u64 reference_root_table[] = {
>  	[6] =	BTRFS_CSUM_TREE_OBJECTID,
>  };
>  
> -int make_btrfs(int fd, const char *device, const char *label,
> +int test_uuid_unique(char *fs_uuid)
> +{
> +	int unique = 1;
> +	blkid_dev_iterate iter = NULL;
> +	blkid_dev dev = NULL;
> +	blkid_cache cache = NULL;
> +
> +	if (blkid_get_cache(&cache, 0) < 0) {
> +		printf("ERROR: lblkid cache get failed\n");
> +		return 1;
> +	}
> +	blkid_probe_all(cache);
> +	iter = blkid_dev_iterate_begin(cache);
> +	blkid_dev_set_search(iter, "UUID", fs_uuid);
> +
> +	while (blkid_dev_next(iter, &dev) == 0) {

This function should skip the check for the devices involved in the mkfs.

> +		dev = blkid_verify(cache, dev);
> +		if (dev) {
> +			unique = 0;
> +			break;
> +		}
> +	}
> +
> +	blkid_dev_iterate_end(iter);
> +	blkid_put_cache(cache);
> +
> +	return unique;
> +}
> +
> +int make_btrfs(int fd, const char *device, const char *label, char *fs_uuid,
>  	       u64 blocks[7], u64 num_bytes, u32 nodesize,
>  	       u32 leafsize, u32 sectorsize, u32 stripesize, u64 features)
>  {
>  	struct btrfs_super_block super;
> -	struct extent_buffer *buf;
> +	struct extent_buffer *buf = NULL;
>  	struct btrfs_root_item root_item;
>  	struct btrfs_disk_key disk_key;
>  	struct btrfs_extent_item *extent_item;
> @@ -125,7 +154,20 @@ int make_btrfs(int fd, const char *device, const char *label,
>  	memset(&super, 0, sizeof(super));
>  
>  	num_bytes = (num_bytes / sectorsize) * sectorsize;
> -	uuid_generate(super.fsid);
> +	if (fs_uuid) {
> +		if (uuid_parse(fs_uuid, super.fsid) != 0) {
> +			fprintf(stderr, "could not parse UUID: %s\n", fs_uuid);
> +			ret = -EINVAL;
> +			goto out;
> +		}
> +		if (!test_uuid_unique(fs_uuid)) {
> +			fprintf(stderr, "non-unique UUID: %s\n", fs_uuid);
> +			ret = -EBUSY;
> +			goto out;
> +		}

Why a second call to test_uuid_unique(fs_uuid) ?

> +	} else {
> +		uuid_generate(super.fsid);
> +	}
>  	uuid_generate(super.dev_item.uuid);
>  	uuid_generate(chunk_tree_uuid);
>  
> 
> diff --git a/utils.h b/utils.h
> index 3c62066..4a404ae 100644
> --- a/utils.h
> +++ b/utils.h
> @@ -39,8 +39,9 @@
>  
>  #define BTRFS_UUID_UNPARSED_SIZE	37
>  
> +int test_uuid_unique(char *fs_uuid);
>  int make_btrfs(int fd, const char *device, const char *label,
> -	       u64 blocks[6], u64 num_bytes, u32 nodesize,
> +	       char *fs_uuid, u64 blocks[6], u64 num_bytes, u32 nodesize,
>  	       u32 leafsize, u32 sectorsize, u32 stripesize, u64 features);
>  int btrfs_make_root_dir(struct btrfs_trans_handle *trans,
>  			struct btrfs_root *root, u64 objectid);
> 
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