On Mon, Sep 26, 2016 at 11:11:49AM +0200, Jan Kara wrote: > > in ext4 we have these SECRM, UNRM, COMPR flags which users can set, they > can read them, but which actually don't do anything. This is actually > somewhat confusing - e.g. I've just got report about one tool which > apparently sets SECRM flag on a file in a hope that it is somehow safer. > Also this is a waste of flags. I agree it doesn't seem very likely we'll be using UNRM any time soon. I can imagine using SECRM and COMPR, but in particular for COMPR it will probably be in a different way (the package manager would install a file that would be compressed in userspace, and then using a *different* ioctl from IOC_SETFLAGS, the COMPR flag would be set and that would make the file immutable and the decompression would be done in userspace). > I've checked other filesystems (xfs, btrfs) and they report EOPNOTSUPP if > these flags are not really supported. Should not we do the same in ext4? I > know there is a concern about breaking userspace but since other major > filesystems already behave this way I think there is a good chance tools > handle this reasonably... What do people thing? What we've been doing for other flags that we don't set is that we simply mask them off (see EXT4_FL_USER_MODIFIABLE) so attempt so set them will be a no-op. What I think would make sense is to simply remove UNRM, SECRM, and UNRM from the USER_MODIFIABLE bitmask. I also suspect it might be useful to define a new ioctl which returns the USER_VISIBLE and USER_MODIFIABLE bitmasks, so that tools can know how to expect (and give warning or error messages as desired). What do folks think? - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
