lift iov_iter into {compat_,}do_readv_writev()

get it closer to matching {compat_,}rw_copy_check_uvector().
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/read_write.c

@@ -695,25 +695,23 @@ unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to)
 }
 EXPORT_SYMBOL(iov_shorten);
 
-static ssize_t do_iter_readv_writev(struct file *filp, int rw, const struct iovec *iov,
-		unsigned long nr_segs, size_t len, loff_t *ppos, iter_fn_t fn)
+static ssize_t do_iter_readv_writev(struct file *filp, struct iov_iter *iter,
+		loff_t *ppos, iter_fn_t fn)
 {
 	struct kiocb kiocb;
-	struct iov_iter iter;
 	ssize_t ret;
 
 	init_sync_kiocb(&kiocb, filp);
 	kiocb.ki_pos = *ppos;
 
-	iov_iter_init(&iter, rw, iov, nr_segs, len);
-	ret = fn(&kiocb, &iter);
+	ret = fn(&kiocb, iter);
 	BUG_ON(ret == -EIOCBQUEUED);
 	*ppos = kiocb.ki_pos;
 	return ret;
 }
 
-static ssize_t do_sync_readv_writev(struct file *filp, const struct iovec *iov,
-		unsigned long nr_segs, size_t len, loff_t *ppos, iov_fn_t fn)
+static ssize_t do_sync_readv_writev(struct file *filp, struct iov_iter *iter,
+		loff_t *ppos, iov_fn_t fn)
 {
 	struct kiocb kiocb;
 	ssize_t ret;
@@ -721,30 +719,23 @@ static ssize_t do_sync_readv_writev(struct file *filp, const struct iovec *iov,
 	init_sync_kiocb(&kiocb, filp);
 	kiocb.ki_pos = *ppos;
 
-	ret = fn(&kiocb, iov, nr_segs, kiocb.ki_pos);
+	ret = fn(&kiocb, iter->iov, iter->nr_segs, kiocb.ki_pos);
 	BUG_ON(ret == -EIOCBQUEUED);
 	*ppos = kiocb.ki_pos;
 	return ret;
 }
 
 /* Do it by hand, with file-ops */
-static ssize_t do_loop_readv_writev(struct file *filp, struct iovec *iov,
-		unsigned long nr_segs, loff_t *ppos, io_fn_t fn)
+static ssize_t do_loop_readv_writev(struct file *filp, struct iov_iter *iter,
+		loff_t *ppos, io_fn_t fn)
 {
-	struct iovec *vector = iov;
 	ssize_t ret = 0;
 
-	while (nr_segs > 0) {
-		void __user *base;
-		size_t len;
+	while (iov_iter_count(iter)) {
+		struct iovec iovec = iov_iter_iovec(iter);
 		ssize_t nr;
 
-		base = vector->iov_base;
-		len = vector->iov_len;
-		vector++;
-		nr_segs--;
-
-		nr = fn(filp, base, len, ppos);
+		nr = fn(filp, iovec.iov_base, iovec.iov_len, ppos);
 
 		if (nr < 0) {
 			if (!ret)
@@ -752,8 +743,9 @@ static ssize_t do_loop_readv_writev(struct file *filp, struct iovec *iov,
 			break;
 		}
 		ret += nr;
-		if (nr != len)
+		if (nr != iovec.iov_len)
 			break;
+		iov_iter_advance(iter, nr);
 	}
 
 	return ret;
@@ -844,6 +836,7 @@ static ssize_t do_readv_writev(int type, struct file *file,
 	size_t tot_len;
 	struct iovec iovstack[UIO_FASTIOV];
 	struct iovec *iov = iovstack;
+	struct iov_iter iter;
 	ssize_t ret;
 	io_fn_t fn;
 	iov_fn_t fnv;
@@ -853,6 +846,7 @@ static ssize_t do_readv_writev(int type, struct file *file,
 				    ARRAY_SIZE(iovstack), iovstack, &iov);
 	if (ret <= 0)
 		goto out;
+	iov_iter_init(&iter, type, iov, nr_segs, ret);
 
 	tot_len = ret;
 	ret = rw_verify_area(type, file, pos, tot_len);
@@ -872,13 +866,11 @@ static ssize_t do_readv_writev(int type, struct file *file,
 	}
 
 	if (iter_fn)
-		ret = do_iter_readv_writev(file, type, iov, nr_segs, tot_len,
-						pos, iter_fn);
+		ret = do_iter_readv_writev(file, &iter, pos, iter_fn);
 	else if (fnv)
-		ret = do_sync_readv_writev(file, iov, nr_segs, tot_len,
-						pos, fnv);
+		ret = do_sync_readv_writev(file, &iter, pos, fnv);
 	else
-		ret = do_loop_readv_writev(file, iov, nr_segs, pos, fn);
+		ret = do_loop_readv_writev(file, &iter, pos, fn);
 
 	if (type != READ)
 		file_end_write(file);
@@ -1024,6 +1016,7 @@ static ssize_t compat_do_readv_writev(int type, struct file *file,
 	compat_ssize_t tot_len;
 	struct iovec iovstack[UIO_FASTIOV];
 	struct iovec *iov = iovstack;
+	struct iov_iter iter;
 	ssize_t ret;
 	io_fn_t fn;
 	iov_fn_t fnv;
@@ -1033,6 +1026,7 @@ static ssize_t compat_do_readv_writev(int type, struct file *file,
 					       UIO_FASTIOV, iovstack, &iov);
 	if (ret <= 0)
 		goto out;
+	iov_iter_init(&iter, type, iov, nr_segs, ret);
 
 	tot_len = ret;
 	ret = rw_verify_area(type, file, pos, tot_len);
@@ -1052,13 +1046,11 @@ static ssize_t compat_do_readv_writev(int type, struct file *file,
 	}
 
 	if (iter_fn)
-		ret = do_iter_readv_writev(file, type, iov, nr_segs, tot_len,
-						pos, iter_fn);
+		ret = do_iter_readv_writev(file, &iter, pos, iter_fn);
 	else if (fnv)
-		ret = do_sync_readv_writev(file, iov, nr_segs, tot_len,
-						pos, fnv);
+		ret = do_sync_readv_writev(file, &iter, pos, fnv);
 	else
-		ret = do_loop_readv_writev(file, iov, nr_segs, pos, fn);
+		ret = do_loop_readv_writev(file, &iter, pos, fn);
 
 	if (type != READ)
 		file_end_write(file);