linux-ext4 - Re: [PATCH] mm: replace FAULT_FLAG_SIZE with parameter to huge

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Message-ID: <CAPcyv4g4NBzE9B+-=uZD38NUd4HurCJUYDnOow7CZGppuJs8FQ@mail.gmail.com>
Date:   Fri, 3 Feb 2017 13:47:06 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Dave Jiang <dave.jiang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-xfs@...r.kernel.org, Linux MM <linux-mm@...ck.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Jan Kara <jack@...e.com>,
        linux-ext4 <linux-ext4@...r.kernel.org>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH] mm: replace FAULT_FLAG_SIZE with parameter to huge_fault

On Fri, Feb 3, 2017 at 1:31 PM, Dave Jiang <dave.jiang@...el.com> wrote:
> Since the introduction of FAULT_FLAG_SIZE to the vm_fault flag, it has
> been somewhat painful with getting the flags set and removed at the
> correct locations. More than one kernel oops was introduced due to
> difficulties of getting the placement correctly. Removing the flag
> values and introducing an input parameter to huge_fault that indicates
> the size of the page entry. This makes the code easier to trace and
> should avoid the issues we see with the fault flags where removal of the
> flag was necessary in the fallback paths.
>
> Signed-off-by: Dave Jiang <dave.jiang@...el.com>

Tested-by: Dan Williams <dan.j.williams@...el.com>

This fixes a crash I can produce with the existing ndctl unit tests
[1] on next-20170202.  Now to go extend the tests to go after the PUD
case...

[1]: https://github.com/pmem/ndctl