Re: [RFC PATCH 2/7] block: convert bio_vec.bv_page to bv_pfn

From: Al Viro <viro@ZenIV.linux.org.uk>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	axboe@kernel.dk, riel@redhat.com, linux-nvdimm@ml01.01.org,
	Dave Hansen <dave.hansen@linux.intel.com>,
	linux-raid@vger.kernel.org, mgorman@suse.de, hch@infradead.org,
	linux-fsdevel@vger.kernel.org,
	Matthew Wilcox <willy@linux.intel.com>
Subject: Re: [RFC PATCH 2/7] block: convert bio_vec.bv_page to bv_pfn
Date: Mon, 16 Mar 2015 23:05:33 +0000	[thread overview]
Message-ID: <20150316230533.GH29656@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20150316202537.33102.12944.stgit@dwillia2-desk3.amr.corp.intel.com>

> diff --git a/mm/iov_iter.c b/mm/iov_iter.c
> index 827732047da1..be9a7c5b8703 100644
> --- a/mm/iov_iter.c
> +++ b/mm/iov_iter.c
> @@ -61,7 +61,7 @@
>  	__p = i->bvec;					\
>  	__v.bv_len = min_t(size_t, n, __p->bv_len - skip);	\
>  	if (likely(__v.bv_len)) {			\
> -		__v.bv_page = __p->bv_page;		\
> +		__v.bv_pfn = __p->bv_pfn;		\
>  		__v.bv_offset = __p->bv_offset + skip; 	\
>  		(void)(STEP);				\
>  		skip += __v.bv_len;			\
> @@ -72,7 +72,7 @@
>  		__v.bv_len = min_t(size_t, n, __p->bv_len);	\
>  		if (unlikely(!__v.bv_len))		\
>  			continue;			\
> -		__v.bv_page = __p->bv_page;		\
> +		__v.bv_pfn = __p->bv_pfn;		\
>  		__v.bv_offset = __p->bv_offset;		\
>  		(void)(STEP);				\
>  		skip = __v.bv_len;			\
> @@ -369,7 +369,7 @@ size_t copy_to_iter(void *addr, size_t bytes, struct iov_iter *i)
>  	iterate_and_advance(i, bytes, v,
>  		__copy_to_user(v.iov_base, (from += v.iov_len) - v.iov_len,
>  			       v.iov_len),
> -		memcpy_to_page(v.bv_page, v.bv_offset,
> +		memcpy_to_page(bvec_page(&v), v.bv_offset,

How had memcpy_to_page(NULL, ...) worked for you?