On Sunday 16 February 2025 21:17:55 Amir Goldstein wrote: > On Sun, Feb 16, 2025 at 7:34 PM Eric Biggers <ebiggers@xxxxxxxxxx> wrote: > > > > On Sun, Feb 16, 2025 at 05:40:26PM +0100, Pali Rohár wrote: > > > This allows to get or set FS_COMPR_FL and FS_ENCRYPT_FL bits via FS_IOC_FSGETXATTR/FS_IOC_FSSETXATTR API. > > > > > > Signed-off-by: Pali Rohár <pali@xxxxxxxxxx> > > > > Does this really allow setting FS_ENCRYPT_FL via FS_IOC_FSSETXATTR, and how does > > this interact with the existing fscrypt support in ext4, f2fs, ubifs, and ceph > > which use that flag? > > As far as I can tell, after fileattr_fill_xflags() call in > ioctl_fssetxattr(), the call > to ext4_fileattr_set() should behave exactly the same if it came some > FS_IOC_FSSETXATTR or from FS_IOC_SETFLAGS. > IOW, EXT4_FL_USER_MODIFIABLE mask will still apply. > > However, unlike the legacy API, we now have an opportunity to deal with > EXT4_FL_USER_MODIFIABLE better than this: > /* > * chattr(1) grabs flags via GETFLAGS, modifies the result and > * passes that to SETFLAGS. So we cannot easily make SETFLAGS > * more restrictive than just silently masking off visible but > * not settable flags as we always did. > */ > > if we have the xflags_mask in the new API (not only the xflags) then > chattr(1) can set EXT4_FL_USER_MODIFIABLE in xflags_mask > ext4_fileattr_set() can verify that > (xflags_mask & ~EXT4_FL_USER_MODIFIABLE == 0). > > However, Pali, this is an important point that your RFC did not follow - > AFAICT, the current kernel code of ext4_fileattr_set() and xfs_fileattr_set() > (and other fs) does not return any error for unknown xflags, it just > ignores them. > > This is why a new ioctl pair FS_IOC_[GS]ETFSXATTR2 is needed IMO > before adding support to ANY new xflags, whether they are mapped to > existing flags like in this patch or are completely new xflags. > > Thanks, > Amir. But xflags_mask is available in this new API. It is available if the FS_XFLAG_HASEXTFIELDS flag is set. So I think that the ext4 improvement mentioned above can be included into this new API. Or I'm missing something?
