1 files changed, 435 insertions, 54 deletions

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 0cd522753ff5..f0c7f1481bae 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -3,8 +3,11 @@
 #include <linux/pagemap.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
+#include <linux/splice.h>
 #include <net/checksum.h>
 
+#define PIPE_PARANOIA /* for now */
+
 #define iterate_iovec(i, n, __v, __p, skip, STEP) {	\
 	size_t left;					\
 	size_t wanted = n;				\
@@ -56,37 +59,24 @@
 	n = wanted;					\
 }
 
-#define iterate_bvec(i, n, __v, __p, skip, STEP) {	\
-	size_t wanted = n;				\
-	__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_offset = __p->bv_offset + skip; 	\
-		(void)(STEP);				\
-		skip += __v.bv_len;			\
-		n -= __v.bv_len;			\
-	}						\
-	while (unlikely(n)) {				\
-		__p++;					\
-		__v.bv_len = min_t(size_t, n, __p->bv_len);	\
-		if (unlikely(!__v.bv_len))		\
+#define iterate_bvec(i, n, __v, __bi, skip, STEP) {	\
+	struct bvec_iter __start;			\
+	__start.bi_size = n;				\
+	__start.bi_bvec_done = skip;			\
+	__start.bi_idx = 0;				\
+	for_each_bvec(__v, i->bvec, __bi, __start) {	\
+		if (!__v.bv_len)			\
 			continue;			\
-		__v.bv_page = __p->bv_page;		\
-		__v.bv_offset = __p->bv_offset;		\
 		(void)(STEP);				\
-		skip = __v.bv_len;			\
-		n -= __v.bv_len;			\
 	}						\
-	n = wanted;					\
 }
 
 #define iterate_all_kinds(i, n, v, I, B, K) {			\
 	size_t skip = i->iov_offset;				\
 	if (unlikely(i->type & ITER_BVEC)) {			\
-		const struct bio_vec *bvec;			\
 		struct bio_vec v;				\
-		iterate_bvec(i, n, v, bvec, skip, (B))		\
+		struct bvec_iter __bi;				\
+		iterate_bvec(i, n, v, __bi, skip, (B))		\
 	} else if (unlikely(i->type & ITER_KVEC)) {		\
 		const struct kvec *kvec;			\
 		struct kvec v;					\
@@ -104,15 +94,13 @@
 	if (i->count) {						\
 		size_t skip = i->iov_offset;			\
 		if (unlikely(i->type & ITER_BVEC)) {		\
-			const struct bio_vec *bvec;		\
+			const struct bio_vec *bvec = i->bvec;	\
 			struct bio_vec v;			\
-			iterate_bvec(i, n, v, bvec, skip, (B))	\
-			if (skip == bvec->bv_len) {		\
-				bvec++;				\
-				skip = 0;			\
-			}					\
-			i->nr_segs -= bvec - i->bvec;		\
-			i->bvec = bvec;				\
+			struct bvec_iter __bi;			\
+			iterate_bvec(i, n, v, __bi, skip, (B))	\
+			i->bvec = __bvec_iter_bvec(i->bvec, __bi);	\
+			i->nr_segs -= i->bvec - bvec;		\
+			skip = __bi.bi_bvec_done;		\
 		} else if (unlikely(i->type & ITER_KVEC)) {	\
 			const struct kvec *kvec;		\
 			struct kvec v;				\
@@ -159,7 +147,7 @@ static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t b
 	buf = iov->iov_base + skip;
 	copy = min(bytes, iov->iov_len - skip);
 
-	if (!fault_in_pages_writeable(buf, copy)) {
+	if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_pages_writeable(buf, copy)) {
 		kaddr = kmap_atomic(page);
 		from = kaddr + offset;
 
@@ -190,6 +178,7 @@ static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t b
 		copy = min(bytes, iov->iov_len - skip);
 	}
 	/* Too bad - revert to non-atomic kmap */
+
 	kaddr = kmap(page);
 	from = kaddr + offset;
 	left = __copy_to_user(buf, from, copy);
@@ -208,6 +197,7 @@ static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t b
 		bytes -= copy;
 	}
 	kunmap(page);
+
 done:
 	if (skip == iov->iov_len) {
 		iov++;
@@ -240,7 +230,7 @@ static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t
 	buf = iov->iov_base + skip;
 	copy = min(bytes, iov->iov_len - skip);
 
-	if (!fault_in_pages_readable(buf, copy)) {
+	if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_pages_readable(buf, copy)) {
 		kaddr = kmap_atomic(page);
 		to = kaddr + offset;
 
@@ -271,6 +261,7 @@ static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t
 		copy = min(bytes, iov->iov_len - skip);
 	}
 	/* Too bad - revert to non-atomic kmap */
+
 	kaddr = kmap(page);
 	to = kaddr + offset;
 	left = __copy_from_user(to, buf, copy);
@@ -289,6 +280,7 @@ static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t
 		bytes -= copy;
 	}
 	kunmap(page);
+
 done:
 	if (skip == iov->iov_len) {
 		iov++;
@@ -301,25 +293,92 @@ done:
 	return wanted - bytes;
 }
 
-/*
- * Fault in the first iovec of the given iov_iter, to a maximum length
- * of bytes. Returns 0 on success, or non-zero if the memory could not be
- * accessed (ie. because it is an invalid address).
- *
- * writev-intensive code may want this to prefault several iovecs -- that
- * would be possible (callers must not rely on the fact that _only_ the
- * first iovec will be faulted with the current implementation).
- */
-int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
+#ifdef PIPE_PARANOIA
+static bool sanity(const struct iov_iter *i)
 {
-	if (!(i->type & (ITER_BVEC|ITER_KVEC))) {
-		char __user *buf = i->iov->iov_base + i->iov_offset;
-		bytes = min(bytes, i->iov->iov_len - i->iov_offset);
-		return fault_in_pages_readable(buf, bytes);
+	struct pipe_inode_info *pipe = i->pipe;
+	int idx = i->idx;
+	int next = pipe->curbuf + pipe->nrbufs;
+	if (i->iov_offset) {
+		struct pipe_buffer *p;
+		if (unlikely(!pipe->nrbufs))
+			goto Bad;	// pipe must be non-empty
+		if (unlikely(idx != ((next - 1) & (pipe->buffers - 1))))
+			goto Bad;	// must be at the last buffer...
+
+		p = &pipe->bufs[idx];
+		if (unlikely(p->offset + p->len != i->iov_offset))
+			goto Bad;	// ... at the end of segment
+	} else {
+		if (idx != (next & (pipe->buffers - 1)))
+			goto Bad;	// must be right after the last buffer
 	}
-	return 0;
+	return true;
+Bad:
+	printk(KERN_ERR "idx = %d, offset = %zd\n", i->idx, i->iov_offset);
+	printk(KERN_ERR "curbuf = %d, nrbufs = %d, buffers = %d\n",
+			pipe->curbuf, pipe->nrbufs, pipe->buffers);
+	for (idx = 0; idx < pipe->buffers; idx++)
+		printk(KERN_ERR "[%p %p %d %d]\n",
+			pipe->bufs[idx].ops,
+			pipe->bufs[idx].page,
+			pipe->bufs[idx].offset,
+			pipe->bufs[idx].len);
+	WARN_ON(1);
+	return false;
+}
+#else
+#define sanity(i) true
+#endif
+
+static inline int next_idx(int idx, struct pipe_inode_info *pipe)
+{
+	return (idx + 1) & (pipe->buffers - 1);
+}
+
+static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t bytes,
+			 struct iov_iter *i)
+{
+	struct pipe_inode_info *pipe = i->pipe;
+	struct pipe_buffer *buf;
+	size_t off;
+	int idx;
+
+	if (unlikely(bytes > i->count))
+		bytes = i->count;
+
+	if (unlikely(!bytes))
+		return 0;
+
+	if (!sanity(i))
+		return 0;
+
+	off = i->iov_offset;
+	idx = i->idx;
+	buf = &pipe->bufs[idx];
+	if (off) {
+		if (offset == off && buf->page == page) {
+			/* merge with the last one */
+			buf->len += bytes;
+			i->iov_offset += bytes;
+			goto out;
+		}
+		idx = next_idx(idx, pipe);
+		buf = &pipe->bufs[idx];
+	}
+	if (idx == pipe->curbuf && pipe->nrbufs)
+		return 0;
+	pipe->nrbufs++;
+	buf->ops = &page_cache_pipe_buf_ops;
+	get_page(buf->page = page);
+	buf->offset = offset;
+	buf->len = bytes;
+	i->iov_offset = offset + bytes;
+	i->idx = idx;
+out:
+	i->count -= bytes;
+	return bytes;
 }
-EXPORT_SYMBOL(iov_iter_fault_in_readable);
 
 /*
  * Fault in one or more iovecs of the given iov_iter, to a maximum length of
@@ -328,7 +387,7 @@ EXPORT_SYMBOL(iov_iter_fault_in_readable);
  * Return 0 on success, or non-zero if the memory could not be accessed (i.e.
  * because it is an invalid address).
  */
-int iov_iter_fault_in_multipages_readable(struct iov_iter *i, size_t bytes)
+int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
 {
 	size_t skip = i->iov_offset;
 	const struct iovec *iov;
@@ -337,15 +396,14 @@ int iov_iter_fault_in_multipages_readable(struct iov_iter *i, size_t bytes)
 
 	if (!(i->type & (ITER_BVEC|ITER_KVEC))) {
 		iterate_iovec(i, bytes, v, iov, skip, ({
-			err = fault_in_multipages_readable(v.iov_base,
-					v.iov_len);
+			err = fault_in_pages_readable(v.iov_base, v.iov_len);
 			if (unlikely(err))
 			return err;
 		0;}))
 	}
 	return 0;
 }
-EXPORT_SYMBOL(iov_iter_fault_in_multipages_readable);
+EXPORT_SYMBOL(iov_iter_fault_in_readable);
 
 void iov_iter_init(struct iov_iter *i, int direction,
 			const struct iovec *iov, unsigned long nr_segs,
@@ -387,9 +445,98 @@ static void memzero_page(struct page *page, size_t offset, size_t len)
 	kunmap_atomic(addr);
 }
 
+static inline bool allocated(struct pipe_buffer *buf)
+{
+	return buf->ops == &default_pipe_buf_ops;
+}
+
+static inline void data_start(const struct iov_iter *i, int *idxp, size_t *offp)
+{
+	size_t off = i->iov_offset;
+	int idx = i->idx;
+	if (off && (!allocated(&i->pipe->bufs[idx]) || off == PAGE_SIZE)) {
+		idx = next_idx(idx, i->pipe);
+		off = 0;
+	}
+	*idxp = idx;
+	*offp = off;
+}
+
+static size_t push_pipe(struct iov_iter *i, size_t size,
+			int *idxp, size_t *offp)
+{
+	struct pipe_inode_info *pipe = i->pipe;
+	size_t off;
+	int idx;
+	ssize_t left;
+
+	if (unlikely(size > i->count))
+		size = i->count;
+	if (unlikely(!size))
+		return 0;
+
+	left = size;
+	data_start(i, &idx, &off);
+	*idxp = idx;
+	*offp = off;
+	if (off) {
+		left -= PAGE_SIZE - off;
+		if (left <= 0) {
+			pipe->bufs[idx].len += size;
+			return size;
+		}
+		pipe->bufs[idx].len = PAGE_SIZE;
+		idx = next_idx(idx, pipe);
+	}
+	while (idx != pipe->curbuf || !pipe->nrbufs) {
+		struct page *page = alloc_page(GFP_USER);
+		if (!page)
+			break;
+		pipe->nrbufs++;
+		pipe->bufs[idx].ops = &default_pipe_buf_ops;
+		pipe->bufs[idx].page = page;
+		pipe->bufs[idx].offset = 0;
+		if (left <= PAGE_SIZE) {
+			pipe->bufs[idx].len = left;
+			return size;
+		}
+		pipe->bufs[idx].len = PAGE_SIZE;
+		left -= PAGE_SIZE;
+		idx = next_idx(idx, pipe);
+	}
+	return size - left;
+}
+
+static size_t copy_pipe_to_iter(const void *addr, size_t bytes,
+				struct iov_iter *i)
+{
+	struct pipe_inode_info *pipe = i->pipe;
+	size_t n, off;
+	int idx;
+
+	if (!sanity(i))
+		return 0;
+
+	bytes = n = push_pipe(i, bytes, &idx, &off);
+	if (unlikely(!n))
+		return 0;
+	for ( ; n; idx = next_idx(idx, pipe), off = 0) {
+		size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
+		memcpy_to_page(pipe->bufs[idx].page, off, addr, chunk);
+		i->idx = idx;
+		i->iov_offset = off + chunk;
+		n -= chunk;
+		addr += chunk;
+	}
+	i->count -= bytes;
+	return bytes;
+}
+
 size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 {
 	const char *from = addr;
+	if (unlikely(i->type & ITER_PIPE))
+		return copy_pipe_to_iter(addr, bytes, i);
 	iterate_and_advance(i, bytes, v,
 		__copy_to_user(v.iov_base, (from += v.iov_len) - v.iov_len,
 			       v.iov_len),
@@ -405,6 +552,10 @@ EXPORT_SYMBOL(copy_to_iter);
 size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
 {
 	char *to = addr;
+	if (unlikely(i->type & ITER_PIPE)) {
+		WARN_ON(1);
+		return 0;
+	}
 	iterate_and_advance(i, bytes, v,
 		__copy_from_user((to += v.iov_len) - v.iov_len, v.iov_base,
 				 v.iov_len),
@@ -420,6 +571,10 @@ EXPORT_SYMBOL(copy_from_iter);
 size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
 {
 	char *to = addr;
+	if (unlikely(i->type & ITER_PIPE)) {
+		WARN_ON(1);
+		return 0;
+	}
 	iterate_and_advance(i, bytes, v,
 		__copy_from_user_nocache((to += v.iov_len) - v.iov_len,
 					 v.iov_base, v.iov_len),
@@ -440,14 +595,20 @@ size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
 		size_t wanted = copy_to_iter(kaddr + offset, bytes, i);
 		kunmap_atomic(kaddr);
 		return wanted;
-	} else
+	} else if (likely(!(i->type & ITER_PIPE)))
 		return copy_page_to_iter_iovec(page, offset, bytes, i);
+	else
+		return copy_page_to_iter_pipe(page, offset, bytes, i);
 }
 EXPORT_SYMBOL(copy_page_to_iter);
 
 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
 			 struct iov_iter *i)
 {
+	if (unlikely(i->type & ITER_PIPE)) {
+		WARN_ON(1);
+		return 0;
+	}
 	if (i->type & (ITER_BVEC|ITER_KVEC)) {
 		void *kaddr = kmap_atomic(page);
 		size_t wanted = copy_from_iter(kaddr + offset, bytes, i);
@@ -458,8 +619,34 @@ size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
 }
 EXPORT_SYMBOL(copy_page_from_iter);
 
+static size_t pipe_zero(size_t bytes, struct iov_iter *i)
+{
+	struct pipe_inode_info *pipe = i->pipe;
+	size_t n, off;
+	int idx;
+
+	if (!sanity(i))
+		return 0;
+
+	bytes = n = push_pipe(i, bytes, &idx, &off);
+	if (unlikely(!n))
+		return 0;
+
+	for ( ; n; idx = next_idx(idx, pipe), off = 0) {
+		size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
+		memzero_page(pipe->bufs[idx].page, off, chunk);
+		i->idx = idx;
+		i->iov_offset = off + chunk;
+		n -= chunk;
+	}
+	i->count -= bytes;
+	return bytes;
+}
+
 size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
 {
+	if (unlikely(i->type & ITER_PIPE))
+		return pipe_zero(bytes, i);
 	iterate_and_advance(i, bytes, v,
 		__clear_user(v.iov_base, v.iov_len),
 		memzero_page(v.bv_page, v.bv_offset, v.bv_len),
@@ -474,6 +661,11 @@ size_t iov_iter_copy_from_user_atomic(struct page *page,
 		struct iov_iter *i, unsigned long offset, size_t bytes)
 {
 	char *kaddr = kmap_atomic(page), *p = kaddr + offset;
+	if (unlikely(i->type & ITER_PIPE)) {
+		kunmap_atomic(kaddr);
+		WARN_ON(1);
+		return 0;
+	}
 	iterate_all_kinds(i, bytes, v,
 		__copy_from_user_inatomic((p += v.iov_len) - v.iov_len,
 					  v.iov_base, v.iov_len),
@@ -486,8 +678,49 @@ size_t iov_iter_copy_from_user_atomic(struct page *page,
 }
 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
 
+static void pipe_advance(struct iov_iter *i, size_t size)
+{
+	struct pipe_inode_info *pipe = i->pipe;
+	struct pipe_buffer *buf;
+	int idx = i->idx;
+	size_t off = i->iov_offset;
+	
+	if (unlikely(i->count < size))
+		size = i->count;
+
+	if (size) {
+		if (off) /* make it relative to the beginning of buffer */
+			size += off - pipe->bufs[idx].offset;
+		while (1) {
+			buf = &pipe->bufs[idx];
+			if (size <= buf->len)
+				break;
+			size -= buf->len;
+			idx = next_idx(idx, pipe);
+		}
+		buf->len = size;
+		i->idx = idx;
+		off = i->iov_offset = buf->offset + size;
+	}
+	if (off)
+		idx = next_idx(idx, pipe);
+	if (pipe->nrbufs) {
+		int unused = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
+		/* [curbuf,unused) is in use.  Free [idx,unused) */
+		while (idx != unused) {
+			pipe_buf_release(pipe, &pipe->bufs[idx]);
+			idx = next_idx(idx, pipe);
+			pipe->nrbufs--;
+		}
+	}
+}
+
 void iov_iter_advance(struct iov_iter *i, size_t size)
 {
+	if (unlikely(i->type & ITER_PIPE)) {
+		pipe_advance(i, size);
+		return;
+	}
 	iterate_and_advance(i, size, v, 0, 0, 0)
 }
 EXPORT_SYMBOL(iov_iter_advance);
@@ -497,6 +730,8 @@ EXPORT_SYMBOL(iov_iter_advance);
  */
 size_t iov_iter_single_seg_count(const struct iov_iter *i)
 {
+	if (unlikely(i->type & ITER_PIPE))
+		return i->count;	// it is a silly place, anyway
 	if (i->nr_segs == 1)
 		return i->count;
 	else if (i->type & ITER_BVEC)
@@ -532,6 +767,19 @@ void iov_iter_bvec(struct iov_iter *i, int direction,
 }
 EXPORT_SYMBOL(iov_iter_bvec);
 
+void iov_iter_pipe(struct iov_iter *i, int direction,
+			struct pipe_inode_info *pipe,
+			size_t count)
+{
+	BUG_ON(direction != ITER_PIPE);
+	i->type = direction;
+	i->pipe = pipe;
+	i->idx = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
+	i->iov_offset = 0;
+	i->count = count;
+}
+EXPORT_SYMBOL(iov_iter_pipe);
+
 unsigned long iov_iter_alignment(const struct iov_iter *i)
 {
 	unsigned long res = 0;
@@ -540,6 +788,11 @@ unsigned long iov_iter_alignment(const struct iov_iter *i)
 	if (!size)
 		return 0;
 
+	if (unlikely(i->type & ITER_PIPE)) {
+		if (i->iov_offset && allocated(&i->pipe->bufs[i->idx]))
+			return size | i->iov_offset;
+		return size;
+	}
 	iterate_all_kinds(i, size, v,
 		(res |= (unsigned long)v.iov_base | v.iov_len, 0),
 		res |= v.bv_offset | v.bv_len,
@@ -556,6 +809,11 @@ unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
 	if (!size)
 		return 0;
 
+	if (unlikely(i->type & ITER_PIPE)) {
+		WARN_ON(1);
+		return ~0U;
+	}
+
 	iterate_all_kinds(i, size, v,
 		(res |= (!res ? 0 : (unsigned long)v.iov_base) |
 			(size != v.iov_len ? size : 0), 0),
@@ -568,6 +826,47 @@ unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
 }
 EXPORT_SYMBOL(iov_iter_gap_alignment);
 
+static inline size_t __pipe_get_pages(struct iov_iter *i,
+				size_t maxsize,
+				struct page **pages,
+				int idx,
+				size_t *start)
+{
+	struct pipe_inode_info *pipe = i->pipe;
+	ssize_t n = push_pipe(i, maxsize, &idx, start);
+	if (!n)
+		return -EFAULT;
+
+	maxsize = n;
+	n += *start;
+	while (n > 0) {
+		get_page(*pages++ = pipe->bufs[idx].page);
+		idx = next_idx(idx, pipe);
+		n -= PAGE_SIZE;
+	}
+
+	return maxsize;
+}
+
+static ssize_t pipe_get_pages(struct iov_iter *i,
+		   struct page **pages, size_t maxsize, unsigned maxpages,
+		   size_t *start)
+{
+	unsigned npages;
+	size_t capacity;
+	int idx;
+
+	if (!sanity(i))
+		return -EFAULT;
+
+	data_start(i, &idx, start);
+	/* some of this one + all after this one */
+	npages = ((i->pipe->curbuf - idx - 1) & (i->pipe->buffers - 1)) + 1;
+	capacity = min(npages,maxpages) * PAGE_SIZE - *start;
+
+	return __pipe_get_pages(i, min(maxsize, capacity), pages, idx, start);
+}
+
 ssize_t iov_iter_get_pages(struct iov_iter *i,
 		   struct page **pages, size_t maxsize, unsigned maxpages,
 		   size_t *start)
@@ -578,6 +877,8 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
 	if (!maxsize)
 		return 0;
 
+	if (unlikely(i->type & ITER_PIPE))
+		return pipe_get_pages(i, pages, maxsize, maxpages, start);
 	iterate_all_kinds(i, maxsize, v, ({
 		unsigned long addr = (unsigned long)v.iov_base;
 		size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
@@ -613,6 +914,37 @@ static struct page **get_pages_array(size_t n)
 	return p;
 }
 
+static ssize_t pipe_get_pages_alloc(struct iov_iter *i,
+		   struct page ***pages, size_t maxsize,
+		   size_t *start)
+{
+	struct page **p;
+	size_t n;
+	int idx;
+	int npages;
+
+	if (!sanity(i))
+		return -EFAULT;
+
+	data_start(i, &idx, start);
+	/* some of this one + all after this one */
+	npages = ((i->pipe->curbuf - idx - 1) & (i->pipe->buffers - 1)) + 1;
+	n = npages * PAGE_SIZE - *start;
+	if (maxsize > n)
+		maxsize = n;
+	else
+		npages = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);
+	p = get_pages_array(npages);
+	if (!p)
+		return -ENOMEM;
+	n = __pipe_get_pages(i, maxsize, p, idx, start);
+	if (n > 0)
+		*pages = p;
+	else
+		kvfree(p);
+	return n;
+}
+
 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
 		   struct page ***pages, size_t maxsize,
 		   size_t *start)
@@ -625,6 +957,8 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
 	if (!maxsize)
 		return 0;
 
+	if (unlikely(i->type & ITER_PIPE))
+		return pipe_get_pages_alloc(i, pages, maxsize, start);
 	iterate_all_kinds(i, maxsize, v, ({
 		unsigned long addr = (unsigned long)v.iov_base;
 		size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
@@ -666,6 +1000,10 @@ size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
 	__wsum sum, next;
 	size_t off = 0;
 	sum = *csum;
+	if (unlikely(i->type & ITER_PIPE)) {
+		WARN_ON(1);
+		return 0;
+	}
 	iterate_and_advance(i, bytes, v, ({
 		int err = 0;
 		next = csum_and_copy_from_user(v.iov_base, 
@@ -704,6 +1042,10 @@ size_t csum_and_copy_to_iter(const void *addr, size_t bytes, __wsum *csum,
 	__wsum sum, next;
 	size_t off = 0;
 	sum = *csum;
+	if (unlikely(i->type & ITER_PIPE)) {
+		WARN_ON(1);	/* for now */
+		return 0;
+	}
 	iterate_and_advance(i, bytes, v, ({
 		int err = 0;
 		next = csum_and_copy_to_user((from += v.iov_len) - v.iov_len,
@@ -743,7 +1085,20 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages)
 	if (!size)
 		return 0;
 
-	iterate_all_kinds(i, size, v, ({
+	if (unlikely(i->type & ITER_PIPE)) {
+		struct pipe_inode_info *pipe = i->pipe;
+		size_t off;
+		int idx;
+
+		if (!sanity(i))
+			return 0;
+
+		data_start(i, &idx, &off);
+		/* some of this one + all after this one */
+		npages = ((pipe->curbuf - idx - 1) & (pipe->buffers - 1)) + 1;
+		if (npages >= maxpages)
+			return maxpages;
+	} else iterate_all_kinds(i, size, v, ({
 		unsigned long p = (unsigned long)v.iov_base;
 		npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
 			- p / PAGE_SIZE;
@@ -768,6 +1123,10 @@ EXPORT_SYMBOL(iov_iter_npages);
 const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
 {
 	*new = *old;
+	if (unlikely(new->type & ITER_PIPE)) {
+		WARN_ON(1);
+		return NULL;
+	}
 	if (new->type & ITER_BVEC)
 		return new->bvec = kmemdup(new->bvec,
 				    new->nr_segs * sizeof(struct bio_vec),
@@ -780,6 +1139,28 @@ const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
 }
 EXPORT_SYMBOL(dup_iter);
 
+/**
+ * import_iovec() - Copy an array of &struct iovec from userspace
+ *     into the kernel, check that it is valid, and initialize a new
+ *     &struct iov_iter iterator to access it.
+ *
+ * @type: One of %READ or %WRITE.
+ * @uvector: Pointer to the userspace array.
+ * @nr_segs: Number of elements in userspace array.
+ * @fast_segs: Number of elements in @iov.
+ * @iov: (input and output parameter) Pointer to pointer to (usually small
+ *     on-stack) kernel array.
+ * @i: Pointer to iterator that will be initialized on success.
+ *
+ * If the array pointed to by *@iov is large enough to hold all @nr_segs,
+ * then this function places %NULL in *@iov on return. Otherwise, a new
+ * array will be allocated and the result placed in *@iov. This means that
+ * the caller may call kfree() on *@iov regardless of whether the small
+ * on-stack array was used or not (and regardless of whether this function
+ * returns an error or not).
+ *
+ * Return: 0 on success or negative error code on error.
+ */
 int import_iovec(int type, const struct iovec __user * uvector,
 		 unsigned nr_segs, unsigned fast_segs,
 		 struct iovec **iov, struct iov_iter *i)