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

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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 <sandeen@xxxxxxxxxx>
---

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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