On Wed, Apr 15, 2020 at 12:14:52PM -0700, Ira Weiny wrote: > On Wed, Apr 15, 2020 at 02:00:02PM +0200, Jan Kara wrote: > > On Mon 13-04-20 21:00:24, ira.weiny@xxxxxxxxx wrote: > > > From: Ira Weiny <ira.weiny@xxxxxxxxx> > > > > > > Verity and DAX are incompatible. Changing the DAX mode due to a verity > > > flag change is wrong without a corresponding address_space_operations > > > update. > > > > > > Make the 2 options mutually exclusive by returning an error if DAX was > > > set first. > > > > > > (Setting DAX is already disabled if Verity is set first.) > > > > > > Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx> > > > --- > > > fs/ext4/verity.c | 3 +++ > > > 1 file changed, 3 insertions(+) > > > > > > diff --git a/fs/ext4/verity.c b/fs/ext4/verity.c > > > index dc5ec724d889..ce3f9a198d3b 100644 > > > --- a/fs/ext4/verity.c > > > +++ b/fs/ext4/verity.c > > > @@ -113,6 +113,9 @@ static int ext4_begin_enable_verity(struct file *filp) > > > handle_t *handle; > > > int err; > > > > > > + if (WARN_ON_ONCE(IS_DAX(inode))) > > > + return -EINVAL; > > > + > > > > Hum, one question, is there a reason for WARN_ON_ONCE()? If I understand > > correctly, user could normally trigger this, couldn't he? > > Ok. I did not think this through but I did think about this. I was following > the code from the encryption side which issues a warning and was thinking that > would be a good way to alert the user they are doing something wrong... > > I think you are right about both of them but we also need to put something in > the verity, dax, and ... (I can't find a file in Documentation which talks > about encryption right off) documentation files.... For verity something like. > > <quote> > Verity and DAX > -------------- > > Verity and DAX are not compatible and attempts to set both of these flags on a > file will fail. > </quote> > > And the same thing in the DAX doc? > > And where would be appropriate for the encrypt doc? > Documentation/filesystems/fscrypt.rst mentions that DAX isn't supported on encrypted files, but it doesn't say what happens if someone tries to do it anyway. Feel free to improve the documentation. - Eric
