1 files changed, 58 insertions, 17 deletions

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 27e3fd942960..044c1d8c230c 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -42,6 +42,7 @@ struct iov_iter_state {
 
 struct iov_iter {
 	u8 iter_type;
+	bool copy_mc;
 	bool nofault;
 	bool data_source;
 	bool user_backed;
@@ -49,14 +50,35 @@ struct iov_iter {
 		size_t iov_offset;
 		int last_offset;
 	};
-	size_t count;
+	/*
+	 * Hack alert: overlay ubuf_iovec with iovec + count, so
+	 * that the members resolve correctly regardless of the type
+	 * of iterator used. This means that you can use:
+	 *
+	 * &iter->__ubuf_iovec or iter->__iov
+	 *
+	 * interchangably for the user_backed cases, hence simplifying
+	 * some of the cases that need to deal with both.
+	 */
 	union {
-		const struct iovec *iov;
-		const struct kvec *kvec;
-		const struct bio_vec *bvec;
-		struct xarray *xarray;
-		struct pipe_inode_info *pipe;
-		void __user *ubuf;
+		/*
+		 * This really should be a const, but we cannot do that without
+		 * also modifying any of the zero-filling iter init functions.
+		 * Leave it non-const for now, but it should be treated as such.
+		 */
+		struct iovec __ubuf_iovec;
+		struct {
+			union {
+				/* use iter_iov() to get the current vec */
+				const struct iovec *__iov;
+				const struct kvec *kvec;
+				const struct bio_vec *bvec;
+				struct xarray *xarray;
+				struct pipe_inode_info *pipe;
+				void __user *ubuf;
+			};
+			size_t count;
+		};
 	};
 	union {
 		unsigned long nr_segs;
@@ -68,6 +90,16 @@ struct iov_iter {
 	};
 };
 
+static inline const struct iovec *iter_iov(const struct iov_iter *iter)
+{
+	if (iter->iter_type == ITER_UBUF)
+		return (const struct iovec *) &iter->__ubuf_iovec;
+	return iter->__iov;
+}
+
+#define iter_iov_addr(iter)	(iter_iov(iter)->iov_base + (iter)->iov_offset)
+#define iter_iov_len(iter)	(iter_iov(iter)->iov_len - (iter)->iov_offset)
+
 static inline enum iter_type iov_iter_type(const struct iov_iter *i)
 {
 	return i->iter_type;
@@ -143,15 +175,6 @@ static inline size_t iov_length(const struct iovec *iov, unsigned long nr_segs)
 	return ret;
 }
 
-static inline struct iovec iov_iter_iovec(const struct iov_iter *iter)
-{
-	return (struct iovec) {
-		.iov_base = iter->iov->iov_base + iter->iov_offset,
-		.iov_len = min(iter->count,
-			       iter->iov->iov_len - iter->iov_offset),
-	};
-}
-
 size_t copy_page_from_iter_atomic(struct page *page, unsigned offset,
 				  size_t bytes, struct iov_iter *i);
 void iov_iter_advance(struct iov_iter *i, size_t bytes);
@@ -173,6 +196,8 @@ static inline size_t copy_folio_to_iter(struct folio *folio, size_t offset,
 {
 	return copy_page_to_iter(&folio->page, offset, bytes, i);
 }
+size_t copy_page_to_iter_nofault(struct page *page, unsigned offset,
+				 size_t bytes, struct iov_iter *i);
 
 static __always_inline __must_check
 size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
@@ -232,8 +257,22 @@ size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i);
 
 #ifdef CONFIG_ARCH_HAS_COPY_MC
 size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
+static inline void iov_iter_set_copy_mc(struct iov_iter *i)
+{
+	i->copy_mc = true;
+}
+
+static inline bool iov_iter_is_copy_mc(const struct iov_iter *i)
+{
+	return i->copy_mc;
+}
 #else
 #define _copy_mc_to_iter _copy_to_iter
+static inline void iov_iter_set_copy_mc(struct iov_iter *i) { }
+static inline bool iov_iter_is_copy_mc(const struct iov_iter *i)
+{
+	return false;
+}
 #endif
 
 size_t iov_iter_zero(size_t bytes, struct iov_iter *);
@@ -356,10 +395,12 @@ static inline void iov_iter_ubuf(struct iov_iter *i, unsigned int direction,
 	WARN_ON(direction & ~(READ | WRITE));
 	*i = (struct iov_iter) {
 		.iter_type = ITER_UBUF,
+		.copy_mc = false,
 		.user_backed = true,
 		.data_source = direction,
 		.ubuf = buf,
-		.count = count
+		.count = count,
+		.nr_segs = 1
 	};
 }
 /* Flags for iov_iter_get/extract_pages*() */