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From: Christoph Hellwig <hch@infradead.org>
To: ira.weiny@intel.com
Subject: Re: [PATCH RFC PKS/PMEM 24/58] fs/freevxfs: Utilize new kmap_thread()
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> -	kaddr = kmap(pp);
> +	kaddr = kmap_thread(pp);
>  	memcpy(kaddr, vip->vii_immed.vi_immed + offset, PAGE_SIZE);
> -	kunmap(pp);
> +	kunmap_thread(pp);

You only Cced me on this particular patch, which means I have absolutely
no idea what kmap_thread and kunmap_thread actually do, and thus can't
provide an informed review.

That being said I think your life would be a lot easier if you add
helpers for the above code sequence and its counterpart that copies
to a potential hughmem page first, as that hides the implementation
details from most users.