On 22 Sep 2015, at 01:18, Dave Chinner <david@xxxxxxxxxxxxx> wrote: > > On Mon, Sep 21, 2015 at 08:04:20PM +0300, Mika Eloranta wrote: >> The UUID can now be optionally specified during filesystem >> creation. > > Which UUID are you wanting to set - the metadata uuid or the user > visible UUID label? Or both? Can you explain the use case for this? > i.e. I'm trying to work out why Why doesn't mkfs.xfs + > xfs_admin -U <uuid> doesn't work for you? I want to set the user visible UUID (same as xfs_admin -U/-u). Whether this impacts the "metadata uuid” or not, I do not know, I’m not an expert on the XFS internals, just a user. Use case: pre-defined UUID set for the filesystem by an _external system_ so that a detached (network) filesystem can later be correctly identified/verified by its UUID (i.e. by the contents of the filesystem instead of metadata outside the filesystem). For example, first creating a database record for a block filesystem with a random UUIDv4 and creating the actual filesystem with the same UUID only after that. “mkfs.ext4" already supports this with the same exact invocation. xfs_admin -U <uuid> does not seem to be an option because: * xfs_admin -U option is going away? http://oss.sgi.com/pipermail/xfs/2015-April/041265.html * Other people have issues with it: https://bugzilla.redhat.com/show_bug.cgi?id=1233220 * I get inconsistent behavior with it: about half of the time /dev/disk/by-uuid/* or “lsblk" do NOT see the change (Fedora 22). * Pre-assigning the UUID straight away during the filesystem creation will work around any current or future bugs (e.g. above) and limitations regarding changing the UUID. * When you need a filesystem with a specific UUID, it is an unnecessary extra step to first create it with a random UUID and only afterwards set it to the one you need. > We need some explaination in the commit message so that when we look > at this in a couple of years time we know why we added this to > mkfs… Sure, I can update the commit message. Please let me know if you need more clarifications, thanks! Cheers, - Mika > >> @@ -948,6 +948,7 @@ main( >> bool finobtflag; >> int spinodes; >> >> + platform_uuid_clear(&uuid); >> progname = basename(argv[0]); >> setlocale(LC_ALL, ""); >> bindtextdomain(PACKAGE, LOCALEDIR); >> @@ -990,7 +991,7 @@ main( >> xi.isdirect = LIBXFS_DIRECT; >> xi.isreadonly = LIBXFS_EXCLUSIVELY; >> >> - while ((c = getopt(argc, argv, "b:d:i:l:L:m:n:KNp:qr:s:CfV")) != EOF) { >> + while ((c = getopt(argc, argv, "b:d:i:l:L:U:m:n:KNp:qr:s:CfV")) != EOF) { >> switch (c) { >> case 'C': >> case 'f': >> @@ -1465,6 +1466,10 @@ main( >> illegal(optarg, "L"); >> label = optarg; >> break; >> + case 'U': >> + if (platform_uuid_parse(optarg, &uuid)) >> + illegal(optarg, "U"); >> + break; > > I'd prefer not to introduce new top level options if possible - this > seems to fit under the -m (global metadata options) option subgroup > (i.e. -m uuid=<UUID>). > >> case 'm': >> p = optarg; >> while (*p != '\0') { >> @@ -2550,7 +2555,9 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"), >> sbp->sb_dblocks = dblocks; >> sbp->sb_rblocks = rtblocks; >> sbp->sb_rextents = rtextents; >> - platform_uuid_generate(&uuid); >> + if (platform_uuid_is_null(&uuid)) { >> + platform_uuid_generate(&uuid); >> + } > > Just generate the uuid initially and then it gets overwritten by the > CLI option if it is set. No need for null detection and generation > here. > > Cheers, > > Dave. > -- > Dave Chinner > david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
