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

[Eric Sandeen <sandeen@redhat.com>]

On 5/14/14, 2:31 AM, Wang Shilong wrote:
> On 05/14/2014 09:18 AM, Eric Sandeen wrote:
>> Allow the specification of the filesystem UUID at mkfs time.
>>
>> (Implemented only for mkfs.btrfs, not btrfs-convert).
> Just out of curiosity, this option is used for what kind of use case?
> I notice Ext4 also has this option.:-)

I don't actually have any use case myself, but a fedora bug filer
was begging for it.  I'm not sure of their usecase.

And you are right, ext4 has the option as well.

Changing the UUID after mkfs in btrfs would be very hard, but
at mkfs time it's trivial.

-Eric

>>
>> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
>> ---
>>
>> 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.
>> +.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..eccb08f 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;
>> @@ -1514,7 +1520,7 @@ 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..3f46e8f 100644
>> --- a/utils.c
>> +++ b/utils.c
>> @@ -93,12 +93,12 @@ static u64 reference_root_table[] = {
>>       [6] =    BTRFS_CSUM_TREE_OBJECTID,
>>   };
>>   -int make_btrfs(int fd, const char *device, const char *label,
>> +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 +125,14 @@ 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;
>> +        }
>> +    } 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..054cbb6 100644
>> --- a/utils.h
>> +++ b/utils.h
>> @@ -40,7 +40,7 @@
>>   #define BTRFS_UUID_UNPARSED_SIZE    37
>>     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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>>
>