start adding the tag to iov_iter

For now, just use the same thing we pass to ->direct_IO() - it's all
iovec-based at the moment.  Pass it explicitly to iov_iter_init() and
account for kvec vs. iovec in there, by the same kludge NFS ->direct_IO()
uses.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

mm/filemap.c

@@ -1730,7 +1730,7 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
 	size_t count = iov_length(iov, nr_segs);
 	struct iov_iter i;
 
-	iov_iter_init(&i, iov, nr_segs, count, 0);
+	iov_iter_init(&i, READ, iov, nr_segs, count);
 	return generic_file_read_iter(iocb, &i);
 }
 EXPORT_SYMBOL(generic_file_aio_read);
@@ -2596,7 +2596,7 @@ ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
 	if (err)
 		goto out;
 
-	iov_iter_init(&from, iov, nr_segs, count, 0);
+	iov_iter_init(&from, WRITE, iov, nr_segs, count);
 
 	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
 	if (unlikely(file->f_flags & O_DIRECT)) {

mm/iov_iter.c

@@ -220,3 +220,18 @@ unsigned long iov_iter_alignment(const struct iov_iter *i)
 	return res;
 }
 EXPORT_SYMBOL(iov_iter_alignment);
+
+void iov_iter_init(struct iov_iter *i, int direction,
+			const struct iovec *iov, unsigned long nr_segs,
+			size_t count)
+{
+	/* It will get better.  Eventually... */
+	if (segment_eq(get_fs(), KERNEL_DS))
+		direction |= REQ_KERNEL;
+	i->type = direction;
+	i->iov = iov;
+	i->nr_segs = nr_segs;
+	i->iov_offset = 0;
+	i->count = count;
+}
+EXPORT_SYMBOL(iov_iter_init);

mm/page_io.c

@@ -268,7 +268,7 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc,
 		init_sync_kiocb(&kiocb, swap_file);
 		kiocb.ki_pos = page_file_offset(page);
 		kiocb.ki_nbytes = PAGE_SIZE;
-		iov_iter_init(&from, &iov, 1, PAGE_SIZE, 0);
+		iov_iter_init(&from, KERNEL_WRITE, &iov, 1, PAGE_SIZE);
 
 		set_page_writeback(page);
 		unlock_page(page);

mm/process_vm_access.c

@@ -274,7 +274,7 @@ static ssize_t process_vm_rw(pid_t pid,
 	if (rc <= 0)
 		goto free_iovecs;
 
-	iov_iter_init(&iter, iov_l, liovcnt, rc, 0);
+	iov_iter_init(&iter, vm_write ? WRITE : READ, iov_l, liovcnt, rc);
 
 	rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV,
 				   iovstack_r, &iov_r);
@@ -337,7 +337,7 @@ compat_process_vm_rw(compat_pid_t pid,
 						  &iov_l);
 	if (rc <= 0)
 		goto free_iovecs;
-	iov_iter_init(&iter, iov_l, liovcnt, rc, 0);
+	iov_iter_init(&iter, vm_write ? WRITE : READ, iov_l, liovcnt, rc);
 	rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt,
 					  UIO_FASTIOV, iovstack_r,
 					  &iov_r);

mm/shmem.c

@@ -1417,7 +1417,7 @@ static ssize_t shmem_file_aio_read(struct kiocb *iocb,
 	loff_t *ppos = &iocb->ki_pos;
 	struct iov_iter iter;
 
-	iov_iter_init(&iter, iov, nr_segs, count, 0);
+	iov_iter_init(&iter, READ, iov, nr_segs, count);
 
 	/*
 	 * Might this read be for a stacking filesystem?  Then when reading