linux-kernel - Re: [GIT PULL] XArray for 4.19

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Date:   Wed, 22 Aug 2018 11:23:02 -0700
From:   Dan Williams <dan.j.williams@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     cl@...ux.com, Matthew Wilcox <willy@...radead.org>,
        linux-mm <linux-mm@...ck.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] XArray for 4.19

On Wed, Aug 22, 2018 at 10:43 AM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> On Wed, Aug 22, 2018 at 10:40 AM Christopher Lameter <cl@...ux.com> wrote:
> >
> > Is this going in this cycle? I have a bunch of stuff on top of this to
> > enable slab object migration.
>
> No.
>
> It was based on a buggy branch that isn't getting pulled

To be clear, I don't think the problem you identified can be triggered
in practice. We are under the equivalent of the page lock for dax in
that path, and if ->mapping is NULL we would bail before finding that
the mapping-size helper returns zero.

> so when I
> started looking at it, the pull request was rejected before I got much
> further.

For the record I think skipping the entirety of the libnvdimm pull
request for this cycle due to that misuse of ilog2() is overkill, but
it's not my kernel.

Andrew, I think this means we need to lean on you to merge
dax-memory-failure and Xarray for 4.20 rather than try to coordinate
our own git branches for these specific topics.

At a minimum for 4.19 I think we should disable MADV_HWPOISON for dax
mappings this cycle to at least close that trivial method to crash the
kernel when using dax.

Dave, I recommend dropping dax-memory-failure and sending the other
libnvdimm topics for 4.19 that have been soaking in -next.