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Date:   Wed, 18 May 2022 06:09:32 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Vivek Kumar <quic_vivekuma@quicinc.com>
Cc:     corbet@lwn.net, catalin.marinas@arm.com, will@kernel.org,
        tglx@linutronix.de, maz@kernel.org, axboe@kernel.dk,
        rafael@kernel.org, akpm@linux-foundation.org,
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        linux-arm-kernel@lists.infradead.org, linux-block@vger.kernel.org,
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        pasha.tatashin@soleen.com, tabba@google.com, ardb@kernel.org,
        tsoni@quicinc.com, quic_psodagud@quicinc.com,
        quic_svaddagi@quicinc.com,
        Prasanna Kumar <quic_kprasan@quicinc.com>
Subject: Re: [RFC 5/6] Hibernate: Add check for pte_valid in saveable page
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On Wed, May 18, 2022 at 01:18:40PM +0530, Vivek Kumar wrote:
> Add check for pte_valid in saveable page after being checked for
> the rest. This is required as PTE is removed for pages allocated
> with dma_alloc_coherent with DMA_ATTR_NO_KERNEL_MAPPING flag set.
> This patch makes sure that these pages are not considered for
> snapshot.

I don't think we ever remove kernel PTEs for DMA_ATTR_NO_KERNEL_MAPPING.
If the allocation did come from highmem they never had one to start
with.  The logic here looks a bit fishy to me.