Date: Tue, 29 Aug 2017 05:45:36 -0700
From: Christoph Hellwig <hch@infradead.org>
To: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>,
        Kees Cook <keescook@chromium.org>, linux-kernel@vger.kernel.org,
        David Windsor <dave@nullcore.net>,
        "Darrick J. Wong" <darrick.wong@oracle.com>, linux-xfs@vger.kernel.org,
        linux-mm@kvack.org, kernel-hardening@lists.openwall.com
Subject: Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab
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On Tue, Aug 29, 2017 at 10:31:26PM +1000, Dave Chinner wrote:
> Probably should.  I've already been looking at killing the inline
> extents array to simplify the management of the extent list (much
> simpler to index by rbtree when we don't have direct/indirect
> structures), so killing the inline data would get rid of the other
> part of the union the inline data sits in.

That's exactly where I came form with my extent list work.  Although
the rbtree performance was horrible due to the memory overhead and
I've switched to a modified b+tree at the moment..

> OTOH, if we're going to have to dynamically allocate the memory for
> the extent/inline data for the data fork, it may just be easier to
> make the entire data fork a dynamic allocation (like the attr fork).

I though about this a bit, but it turned out that we basically
always need the data anyway, so I don't think it's going to buy
us much unless we shrink the inode enough so that they better fit
into a page.