[PATCH 1/5] new helper: iov_iter_bvec()

[Christoph Hellwig <hch@lst.de>]

From: Al Viro <viro@zeniv.linux.org.uk>

similar to iov_iter_kvec(), for ITER_BVEC ones

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/splice.c         |  7 ++-----
 include/linux/uio.h |  4 +++-
 mm/iov_iter.c       | 17 +++++++++++++++--
 mm/page_io.c        |  9 ++-------
 4 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/fs/splice.c b/fs/splice.c
index 75c6058..7c7176f 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1006,11 +1006,8 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 		}
 
 		/* ... iov_iter */
-		from.type = ITER_BVEC | WRITE;
-		from.bvec = array;
-		from.nr_segs = n;
-		from.count = sd.total_len - left;
-		from.iov_offset = 0;
+		iov_iter_bvec(&from, ITER_BVEC | WRITE, array, n,
+			      sd.total_len - left);
 
 		/* ... and iocb */
 		init_sync_kiocb(&kiocb, out);
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 1c5e453..b447402 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -88,7 +88,9 @@ size_t iov_iter_zero(size_t bytes, struct iov_iter *);
 unsigned long iov_iter_alignment(const struct iov_iter *i);
 void iov_iter_init(struct iov_iter *i, int direction, const struct iovec *iov,
 			unsigned long nr_segs, size_t count);
-void iov_iter_kvec(struct iov_iter *i, int direction, const struct kvec *iov,
+void iov_iter_kvec(struct iov_iter *i, int direction, const struct kvec *kvec,
+			unsigned long nr_segs, size_t count);
+void iov_iter_bvec(struct iov_iter *i, int direction, const struct bio_vec *bvec,
 			unsigned long nr_segs, size_t count);
 ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,
 			size_t maxsize, unsigned maxpages, size_t *start);
diff --git a/mm/iov_iter.c b/mm/iov_iter.c
index a1599ca..8277320 100644
--- a/mm/iov_iter.c
+++ b/mm/iov_iter.c
@@ -501,18 +501,31 @@ size_t iov_iter_single_seg_count(const struct iov_iter *i)
 EXPORT_SYMBOL(iov_iter_single_seg_count);
 
 void iov_iter_kvec(struct iov_iter *i, int direction,
-			const struct kvec *iov, unsigned long nr_segs,
+			const struct kvec *kvec, unsigned long nr_segs,
 			size_t count)
 {
 	BUG_ON(!(direction & ITER_KVEC));
 	i->type = direction;
-	i->kvec = (struct kvec *)iov;
+	i->kvec = kvec;
 	i->nr_segs = nr_segs;
 	i->iov_offset = 0;
 	i->count = count;
 }
 EXPORT_SYMBOL(iov_iter_kvec);
 
+void iov_iter_bvec(struct iov_iter *i, int direction,
+			const struct bio_vec *bvec, unsigned long nr_segs,
+			size_t count)
+{
+	BUG_ON(!(direction & ITER_BVEC));
+	i->type = direction;
+	i->bvec = bvec;
+	i->nr_segs = nr_segs;
+	i->iov_offset = 0;
+	i->count = count;
+}
+EXPORT_SYMBOL(iov_iter_bvec);
+
 unsigned long iov_iter_alignment(const struct iov_iter *i)
 {
 	unsigned long res = 0;
diff --git a/mm/page_io.c b/mm/page_io.c
index 955db8b..e604580 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -269,14 +269,9 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc,
 			.bv_len  = PAGE_SIZE,
 			.bv_offset = 0
 		};
-		struct iov_iter from = {
-			.type = ITER_BVEC | WRITE,
-			.count = PAGE_SIZE,
-			.iov_offset = 0,
-			.nr_segs = 1,
-		};
-		from.bvec = &bv;	/* older gcc versions are broken */
+		struct iov_iter from;
 
+		iov_iter_bvec(&from, ITER_BVEC | WRITE, &bv, 1, PAGE_SIZE);
 		init_sync_kiocb(&kiocb, swap_file);
 		kiocb.ki_pos = page_file_offset(page);
 		kiocb.ki_nbytes = PAGE_SIZE;
-- 
1.9.1