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;