On Wed, Aug 11, 2021 at 09:25:18PM -0400, Theodore Ts'o wrote: > On Wed, Aug 11, 2021 at 04:32:53PM -0700, Darrick J. Wong wrote: > > +/* > > + * Returns true if the user is forcing an old format (e.g. ext2, ext3). > > + * > > + * If there is no fs_types list, the user invoked us with no explicit type and > > + * gets the default (ext4) format. If we find the latest format (ext4) in the > > + * type list, some combination of program name and -T argument put us in ext4 > > + * mode. Anything else (ext2, ext3, hurd) and we return false. > > + */ > > So that's not actually quite right. Even if the user has no explicit > type, mke2fs will assign a default type --- and it's not necessarily > ext4. You can see what the contents of the fs_types list using the -v > option: Ok, fair, I'll fix the message. "If the user invoked us with no explicit type, mke2fs adds some variant of ext* to the type list by default." > % /bin/rm /tmp/foo.img ; mke2fs -vq /tmp/foo.img 8m > fs_types for mke2fs.conf resolution: 'ext2', 'small' > % /bin/rm /tmp/foo.img ; mke2fs -vq -T news /tmp/foo.img 8m > fs_types for mke2fs.conf resolution: 'ext2', 'news' > % /bin/rm /tmp/foo.img ; mkfs.ext4 -vq /tmp/foo.img 8m > fs_types for mke2fs.conf resolution: 'ext4', 'small' > % /bin/rm /tmp/foo.img ; mkfs.ext4 -T huge -vq /tmp/foo.img 8m > fs_types for mke2fs.conf resolution: 'ext4', 'huge' > % /bin/rm /tmp/foo.img ; mkfs.ext4 -o hurd -vq /tmp/foo.img 8m > fs_types for mke2fs.conf resolution: 'ext2', 'small', 'hurd' > > Also note that the ext2/ext3/ext4 fs_type will always be in > fs_types[0], so it's not necessary to search the entire list, as the > patch is currently doing: But that's not quite right either: # mke2fs -t small -T ext4 -vqn a.img fs_types for mke2fs.conf resolution: 'small', 'ext4' So to find the 'ext4' here, you /do/ have to iterate the whole list. --D > > > + for (i = 0; fs_types[i]; i++) > > + if (!strcmp(fs_types[i], "ext4")) > > + found_ext4 = 1; > > > Cheers, > > - Ted > > P.S. Although I'm not aware of anyone actually doing this, if there > mke2fs is installed as mke3fs or mke4fs, that's the equivalent of > mkfs.ext3 and mkfs.ext4. (See the logic in the parse_fs_type > function.) Although perhaps there is some obscure distro somewhere > out there that I don't know about....
