linux-ext4 - Re: [PATCH v2 01/12] fs-verity: add a documentation file

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Date:   Mon, 17 Dec 2018 08:49:49 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Christoph Hellwig <hch@...radead.org>,
        linux-fscrypt@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Theodore Y . Ts'o" <tytso@....edu>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Victor Hsieh <victorhsieh@...gle.com>,
        Chandan Rajendra <chandan@...ux.vnet.ibm.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v2 01/12] fs-verity: add a documentation file

On Thu, Dec 13, 2018 at 08:48:03PM -0800, Eric Biggers wrote:
> Sure, those specific people (modulo you just now) haven't responded to the
> fs-verity patches yet.  But again, the patches have been out for review for
> months.  Of course, we always prefer more reviews over fewer, and we strongly
> encourage anyone interested to review fs-verity!  (The Documentation/ file may
> be a good place to start.)  But ultimately we cannot force reviews, and as you
> know kernel reviews can be very hard to come by.  Yet, people still need
> fs-verity anyway; it isn't just some toy.  And we're committed to maintaining
> it, similar to fscrypt.  The ext4 and f2fs maintainers are also satisfied with
> the current approach to storing the verity metadata past EOF; in fact it was
> even originally Ted's idea, I think.

But you also can't force inclusion.  And Linus just recently complained
about merging common code patches through trees for a specific fs
without proper VFS ACKs.  And that was a for a case without userspace
ABI implications, so we really need a much better review here.

Including a VFS person ACK, CC to linux-abi and man pages for the
interface.

> > Given that you alread use an ioctl as the interface what is the problem
> > of passing this data through the ioctl?
> 
> Do you mean pass the verity metadata in a buffer?  That cannot work in general,
> because it may be too large to fit into memory.

Have a pointer in the ioctl and do get_user_pages on it.