On Tue, Mar 17, 2015 at 6:02 AM, Matthew Wilcox [off-list ref] wrote:

On Mon, Mar 16, 2015 at 11:05:33PM +0000, Al Viro wrote:

quoted

quoted

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?

 static inline struct page *bvec_page(const struct bio_vec *bvec)
 {
-       return bvec->bv_page;
+       return pfn_to_page(bvec->bv_pfn.pfn);
 }

(yes, more work to be done here to make copy_to_iter work to a bvec that
is actually targetting a page-less address, but these are RFC patches
showing the direction we're heading in while keeping current code working)

Right, the next item to tackle is kmap() and kmap_atomic() before we
can start converting paths to be "native" pfn-only.