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Date:   Thu, 2 Feb 2023 20:20:03 +0000
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Michael Cree <mcree@orcon.net.nz>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Xu <peterx@redhat.com>, linux-arch@vger.kernel.org,
        linux-alpha@vger.kernel.org,
        Richard Henderson <richard.henderson@linaro.org>
Subject: Re: [RFC][PATCHSET] VM_FAULT_RETRY fixes
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On Thu, Feb 02, 2023 at 03:20:37PM +0000, Al Viro wrote:

> "Racy" probably had been about something along the lines of the scenario
> I'd mentioned just upthread, but in 5.5 that "racy" escalated to "does not
> work at all" - if you ever hit a vmalloc-related fault, you are going
> to get an oops.  You still get 8Gb, but beyond that it's broken.
> 
> And it's almost certainly not the problem you are seeing...

Incidentally, direct store to pgd_val() in there looks fishy wrt barriers -
shouldn't there be an smp_wmb() before we shove that sucker into our
top-level table's entry?