linux-ext4 - Re: [PATCH 3/3] ext4: add a new ioctl EXT4_IOC

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Date:   Sun, 11 Aug 2019 14:38:36 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 3/3] ext4: add a new ioctl EXT4_IOC_GETSTATE

On Fri, Aug 09, 2019 at 08:12:47PM -0400, Theodore Y. Ts'o wrote:
> On Fri, Aug 09, 2019 at 12:18:12PM -0700, Eric Biggers wrote:
> > On Fri, Aug 09, 2019 at 02:18:31PM -0400, Theodore Ts'o wrote:
> > > The new ioctl EXT4_IOC_GETSTATE returns some of the dynamic state of
> > > an ext4 inode for debugging purposes.
> > > 
> > > Signed-off-by: Theodore Ts'o <tytso@....edu>
> > > ---
> > >  fs/ext4/ext4.h  | 11 +++++++++++
> > >  fs/ext4/ioctl.c | 17 +++++++++++++++++
> > >  2 files changed, 28 insertions(+)
> > > 
> > > diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> > > index f6c305b43ffa..58b7a0905186 100644
> > > --- a/fs/ext4/ext4.h
> > > +++ b/fs/ext4/ext4.h
> > > @@ -651,6 +651,7 @@ enum {
> > >  #define EXT4_IOC_GET_ENCRYPTION_POLICY	FS_IOC_GET_ENCRYPTION_POLICY
> > >  /* ioctl codes 19--2F are reserved for fscrypt */
> > >  #define EXT4_IOC_CLEAR_ES_CACHE		_IO('f', 30)
> > > +#define EXT4_IOC_GETSTATE		_IOW('f', 30, __u32)
> > 
> > 30 == 0x1e overlaps with the range claimed to be reserved for fscrypt.
> > 
> > Also, these two new ioctls are both number 30, which means they can't be
> > controlled separately by SELinux, which only looks at the number.
> 
> Yeah, that was my screw up.  The range reservation for fscrypt was
> intended to be in decimal starting with 19 decimal
> (FSIOC_SET_ENCRYPTION_POLICY), and I believe with the new key
> management we were up to 26?  So If I reserve up to 39, that should be
> more than enough, do you agree?
> 
> I'll then make EXT4_IOC_CLEAR_ES_CACHE 40 and EXT4_IOC_GETSTATE 41.
> 
> If we're in agreement, then I'll add an update to
> Documentation/ioctl/ioctl-number.rst, which is badly out of date with
> respect to the ioctl's used in ext2 and ext4 (and of course ext3 has
> since been removed from the kernel tree).
> 

Sounds good to me.

- Eric