Re: [PATCH] mm: get rid of WARN if failed to cow user pages

[Dan Williams]

[ drop Ross, add Kirill, linux-mm, and lkml ]

On Tue, Dec 24, 2019 at 9:42 PM Murphy Zhou <jencce.kernel@xxxxxxxxx> wrote:
>
> By running xfstests with fsdax enabled, generic/437 always hits this
> warning[1] since this commit:
>
> commit 83d116c53058d505ddef051e90ab27f57015b025
> Author: Jia He <justin.he@xxxxxxx>
> Date:   Fri Oct 11 22:09:39 2019 +0800
>
>     mm: fix double page fault on arm64 if PTE_AF is cleared
>
> Looking at the test program[2] generic/437 uses, it's pretty easy
> to hit this warning. Remove this WARN as it seems not necessary.

This is not sufficient justification. Does this same test fail without
DAX? If not, why not? At a minimum you need to explain why this is not
indicating a problem.