net/9p: switch the guts of p9_client_{read,write}() to iov_iter

... and have get_user_pages_fast() mapping fewer pages than requested
to generate a short read/write.

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

1 files changed, 8 insertions, 16 deletions

diff --git a/net/9p/protocol.c b/net/9p/protocol.c
index ab9127ec5b7a..e9d0f0c1a048 100644
--- a/net/9p/protocol.c
+++ b/net/9p/protocol.c
@@ -33,6 +33,7 @@
 #include <linux/sched.h>
 #include <linux/stddef.h>
 #include <linux/types.h>
+#include <linux/uio.h>
 #include <net/9p/9p.h>
 #include <net/9p/client.h>
 #include "protocol.h"
@@ -69,10 +70,11 @@ static size_t pdu_write(struct p9_fcall *pdu, const void *data, size_t size)
 }
 
 static size_t
-pdu_write_u(struct p9_fcall *pdu, const char __user *udata, size_t size)
+pdu_write_u(struct p9_fcall *pdu, struct iov_iter *from, size_t size)
 {
 	size_t len = min(pdu->capacity - pdu->size, size);
-	if (copy_from_user(&pdu->sdata[pdu->size], udata, len))
+	struct iov_iter i = *from;
+	if (copy_from_iter(&pdu->sdata[pdu->size], len, &i) != len)
 		len = 0;
 
 	pdu->size += len;
@@ -437,23 +439,13 @@ p9pdu_vwritef(struct p9_fcall *pdu, int proto_version, const char *fmt,
 						 stbuf->extension, stbuf->n_uid,
 						 stbuf->n_gid, stbuf->n_muid);
 			} break;
-		case 'D':{
-				uint32_t count = va_arg(ap, uint32_t);
-				const void *data = va_arg(ap, const void *);
-
-				errcode = p9pdu_writef(pdu, proto_version, "d",
-									count);
-				if (!errcode && pdu_write(pdu, data, count))
-					errcode = -EFAULT;
-			}
-			break;
-		case 'U':{
+		case 'V':{
 				int32_t count = va_arg(ap, int32_t);
-				const char __user *udata =
-						va_arg(ap, const void __user *);
+				struct iov_iter *from =
+						va_arg(ap, struct iov_iter *);
 				errcode = p9pdu_writef(pdu, proto_version, "d",
 									count);
-				if (!errcode && pdu_write_u(pdu, udata, count))
+				if (!errcode && pdu_write_u(pdu, from, count))
 					errcode = -EFAULT;
 			}
 			break;