Re: [PATCH RFC 2/8] fs/ext4: Disallow verity if inode is DAX

[Ira Weiny <ira.weiny@intel.com>]

On Wed, Apr 15, 2020 at 02:00:02PM +0200, Jan Kara wrote:
> On Mon 13-04-20 21:00:24, ira.weiny@intel.com wrote:
> > From: Ira Weiny <ira.weiny@intel.com>
> > 
> > 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@intel.com>
> > ---
> >  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?

Removed and added to the verity doc.
Ira

> 
> 								Honza
> 
> >  	if (ext4_verity_in_progress(inode))
> >  		return -EBUSY;
> >  
> > -- 
> > 2.25.1
> > 
> -- 
> Jan Kara <jack@suse.com>
> SUSE Labs, CR