iov_iter: Add a function to extract a page list from an iterator

[sfrench/cifs-2.6.git] / include / linux / uio.h

diff --git a/include/linux/uio.h b/include/linux/uio.h
index eec6ed8a627a305d1eb8ea3787f5815cc1ca01af..514e3b7b06b8082ae087b1c290e4fcc57af6d695 100644 (file)
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -361,9 +361,34 @@ static inline void iov_iter_ubuf(struct iov_iter *i, unsigned int direction,
                .count = count
        };
 }
-
 /* Flags for iov_iter_get/extract_pages*() */
 /* Allow P2PDMA on the extracted pages */
 #define ITER_ALLOW_P2PDMA      ((__force iov_iter_extraction_t)0x01)
 
+ssize_t iov_iter_extract_pages(struct iov_iter *i, struct page ***pages,
+                              size_t maxsize, unsigned int maxpages,
+                              iov_iter_extraction_t extraction_flags,
+                              size_t *offset0);
+
+/**
+ * iov_iter_extract_will_pin - Indicate how pages from the iterator will be retained
+ * @iter: The iterator
+ *
+ * Examine the iterator and indicate by returning true or false as to how, if
+ * at all, pages extracted from the iterator will be retained by the extraction
+ * function.
+ *
+ * %true indicates that the pages will have a pin placed in them that the
+ * caller must unpin.  This is must be done for DMA/async DIO to force fork()
+ * to forcibly copy a page for the child (the parent must retain the original
+ * page).
+ *
+ * %false indicates that no measures are taken and that it's up to the caller
+ * to retain the pages.
+ */
+static inline bool iov_iter_extract_will_pin(const struct iov_iter *iter)
+{
+       return user_backed_iter(iter);
+}
+
 #endif