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.:-)


Signed-off-by: Eric Sandeen <sand...@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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