Timothy Pepper
2014-Jan-08 21:50 UTC
[RFC PATCH] Btrfs-progs: Add optional 'uuid' parameter to mkfs.btrfs
The patch below is a simple quick attempt at allowing the filesystem
UUID to be specified by the user at mkfs time. Googling around I've
seen a lot of people wishing they could "change their btrfs uuid".
I understand why that's not going to happen. But this little patch
seems like it could give them a control somewhat equivalent to what
they're seeking. It works for me anyway, so I thought I'd share it in
case it is upstream acceptable and useful to others.
--
Tim Pepper <timothy.c.pepper@linux.intel.com>
Intel Open Source Technology Center
=============================================================================
From: Tim Pepper <timothy.c.pepper@linux.intel.com>
Date: Wed, 8 Jan 2014 11:20:26 -0800
Subject: [PATCH] Add optional 'uuid' parameter to mkfs.btrfs
Currently the code supports specifying a label, but not UUID. Since the
UUID of a btrfs filesystem can't be modified after the filesystem is made,
it is useful to support specifying the UUID when the filesystem is made.
Signed-off-by: Tim Pepper <timothy.c.pepper@linux.intel.com>
---
btrfs-convert.c | 2 +-
mkfs.c | 23 +++++++++++++++++++++--
utils.c | 7 +++++--
utils.h | 2 +-
4 files changed, 28 insertions(+), 6 deletions(-)
diff --git a/btrfs-convert.c b/btrfs-convert.c
index ae10eed..7ec1ac5 100644
--- a/btrfs-convert.c
+++ b/btrfs-convert.c
@@ -2242,7 +2242,7 @@ static int do_convert(const char *devname, int datacsum,
int packing,
fprintf(stderr, "unable to open %s\n", devname);
goto fail;
}
- ret = make_btrfs(fd, devname, ext2_fs->super->s_volume_name,
+ ret = make_btrfs(fd, devname, ext2_fs->super->s_volume_name, NULL,
blocks, total_bytes, blocksize, blocksize,
blocksize, blocksize, 0);
if (ret) {
diff --git a/mkfs.c b/mkfs.c
index 33369f9..d5e65d9 100644
--- a/mkfs.c
+++ b/mkfs.c
@@ -280,6 +280,7 @@ static void print_usage(void)
fprintf(stderr, "\t -f --force force overwrite of existing
filesystem\n");
fprintf(stderr, "\t -l --leafsize size of btree leaves\n");
fprintf(stderr, "\t -L --label set a label\n");
+ fprintf(stderr, "\t -U --uuid set a UUID\n");
fprintf(stderr, "\t -m --metadata metadata profile, values like data
profile\n");
fprintf(stderr, "\t -M --mixed mix metadata and data together\n");
fprintf(stderr, "\t -n --nodesize size of btree nodes\n");
@@ -335,12 +336,25 @@ static char *parse_label(char *input)
return strdup(input);
}
+static char *parse_uuid(char *input)
+{
+ int len = strlen(input);
+#define BTRFS_UUID_STRING_SIZE (2*BTRFS_UUID_SIZE + 5)
+ if (len >= BTRFS_UUID_STRING_SIZE) {
+ fprintf(stderr, "UUID %s is too long (max %d)\n", input,
+ BTRFS_UUID_STRING_SIZE - 1);
+ exit(1);
+ }
+ return strdup(input);
+}
+
static struct option long_options[] = {
{ "alloc-start", 1, NULL, 'A'},
{ "byte-count", 1, NULL, 'b' },
{ "force", 0, NULL, 'f' },
{ "leafsize", 1, NULL, 'l' },
{ "label", 1, NULL, 'L'},
+ { "uuid", 1, NULL, 'U'},
{ "metadata", 1, NULL, 'm' },
{ "mixed", 0, NULL, 'M' },
{ "nodesize", 1, NULL, 'n' },
@@ -1228,6 +1242,7 @@ int main(int ac, char **av)
struct btrfs_root *root;
struct btrfs_trans_handle *trans;
char *label = NULL;
+ char *uuid = NULL;
char *first_file;
u64 block_count = 0;
u64 dev_block_count = 0;
@@ -1264,7 +1279,7 @@ int main(int ac, char **av)
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:U:O:r:VMK",
long_options, &option_index);
if (c < 0)
break;
@@ -1288,6 +1303,9 @@ int main(int ac, char **av)
case 'L':
label = parse_label(optarg);
break;
+ case 'U':
+ uuid = parse_uuid(optarg);
+ break;
case 'm':
metadata_profile = parse_profile(optarg);
metadata_profile_opt = 1;
@@ -1497,7 +1515,7 @@ 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, uuid, blocks, dev_block_count,
nodesize, leafsize,
sectorsize, stripesize, features);
if (ret) {
@@ -1595,5 +1613,6 @@ raid_groups:
ret = close_ctree(root);
BUG_ON(ret);
free(label);
+ free(uuid);
return 0;
}
diff --git a/utils.c b/utils.c
index f499023..4b85eeb 100644
--- a/utils.c
+++ b/utils.c
@@ -71,7 +71,7 @@ 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, const char *uuid,
u64 blocks[7], u64 num_bytes, u32 nodesize,
u32 leafsize, u32 sectorsize, u32 stripesize, u64 features)
{
@@ -103,7 +103,10 @@ 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 (uuid)
+ uuid_parse(uuid, super.fsid);
+ 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 6f4b10c..3b89ece 100644
--- a/utils.h
+++ b/utils.h
@@ -37,7 +37,7 @@
#define BTRFS_ARG_UUID 2
#define BTRFS_ARG_BLKDEV 3
-int make_btrfs(int fd, const char *device, const char *label,
+int make_btrfs(int fd, const char *device, const char *label, const char *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,
--
1.8.3.1
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