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Date:   Fri, 18 Nov 2022 17:45:31 +0100
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Subject: Re: [PATCH mm-unstable v1 04/20] mm: add early FAULT_FLAG_UNSHARE
 consistency checks
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To:     David Hildenbrand <david@redhat.com>, linux-kernel@vger.kernel.org
Cc:     x86@kernel.org, linux-alpha@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
        linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        sparclinux@vger.kernel.org, linux-um@lists.infradead.org,
        etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        linux-samsung-soc@vger.kernel.org, linux-rdma@vger.kernel.org,
        linux-media@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-mm@kvack.org, linux-perf-users@vger.kernel.org,
        linux-security-module@vger.kernel.org,
        linux-kselftest@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        John Hubbard <jhubbard@nvidia.com>,
        Peter Xu <peterx@redhat.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Hugh Dickins <hughd@google.com>, Nadav Amit <namit@vmware.com>,
        Matthew Wilcox <willy@infradead.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Muchun Song <songmuchun@bytedance.com>,
        Shuah Khan <shuah@kernel.org>,
        Lucas Stach <l.stach@pengutronix.de>,
        David Airlie <airlied@gmail.com>,
        Oded Gabbay <ogabbay@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Christoph Hellwig <hch@infradead.org>,
        Alex Williamson <alex.williamson@redhat.com>
References: <20221116102659.70287-1-david@redhat.com>
 <20221116102659.70287-5-david@redhat.com>
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <20221116102659.70287-5-david@redhat.com>
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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@redhat.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@suse.cz>