linux-kernel - Re: [PATCH mm-unstable v1 04/20] mm: add early FAULT_FLAG

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Date:   Fri, 18 Nov 2022 17:45:31 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, linux-alpha@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        sparclinux@...r.kernel.org, linux-um@...ts.infradead.org,
        etnaviv@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-samsung-soc@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-media@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-perf-users@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        John Hubbard <jhubbard@...dia.com>,
        Peter Xu <peterx@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Hugh Dickins <hughd@...gle.com>, Nadav Amit <namit@...are.com>,
        Matthew Wilcox <willy@...radead.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Shuah Khan <shuah@...nel.org>,
        Lucas Stach <l.stach@...gutronix.de>,
        David Airlie <airlied@...il.com>,
        Oded Gabbay <ogabbay@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Christoph Hellwig <hch@...radead.org>,
        Alex Williamson <alex.williamson@...hat.com>
Subject: Re: [PATCH mm-unstable v1 04/20] mm: add early FAULT_FLAG_UNSHARE
 consistency checks

On 11/16/22 11:26, David Hildenbrand wrote:
> For now, FAULT_FLAG_UNSHARE only applies to anonymous pages, which
> implies a COW mapping. Let's hide FAULT_FLAG_UNSHARE early if we're not
> dealing with a COW mapping, such that we treat it like a read fault as
> documented and don't have to worry about the flag throughout all fault
> handlers.
> 
> While at it, centralize the check for mutual exclusion of
> FAULT_FLAG_UNSHARE and FAULT_FLAG_WRITE and just drop the check that
> either flag is set in the WP handler.
> 
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  mm/huge_memory.c |  3 ---
>  mm/hugetlb.c     |  5 -----
>  mm/memory.c      | 23 ++++++++++++++++++++---
>  3 files changed, 20 insertions(+), 11 deletions(-)

Reviewed-by: Vlastimil Babka <vbabka@...e.cz>