splice: don't pass the address of ->f_pos to methods

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/read_write.c b/fs/read_write.c
index 0343000..2cefa41 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1064,6 +1064,7 @@
 	struct fd in, out;
 	struct inode *in_inode, *out_inode;
 	loff_t pos;
+	loff_t out_pos;
 	ssize_t retval;
 	int fl;
 
@@ -1077,12 +1078,14 @@
 	if (!(in.file->f_mode & FMODE_READ))
 		goto fput_in;
 	retval = -ESPIPE;
-	if (!ppos)
-		ppos = &in.file->f_pos;
-	else
+	if (!ppos) {
+		pos = in.file->f_pos;
+	} else {
+		pos = *ppos;
 		if (!(in.file->f_mode & FMODE_PREAD))
 			goto fput_in;
-	retval = rw_verify_area(READ, in.file, ppos, count);
+	}
+	retval = rw_verify_area(READ, in.file, &pos, count);
 	if (retval < 0)
 		goto fput_in;
 	count = retval;
@@ -1099,7 +1102,8 @@
 	retval = -EINVAL;
 	in_inode = file_inode(in.file);
 	out_inode = file_inode(out.file);
-	retval = rw_verify_area(WRITE, out.file, &out.file->f_pos, count);
+	out_pos = out.file->f_pos;
+	retval = rw_verify_area(WRITE, out.file, &out_pos, count);
 	if (retval < 0)
 		goto fput_out;
 	count = retval;
@@ -1107,7 +1111,6 @@
 	if (!max)
 		max = min(in_inode->i_sb->s_maxbytes, out_inode->i_sb->s_maxbytes);
 
-	pos = *ppos;
 	if (unlikely(pos + count > max)) {
 		retval = -EOVERFLOW;
 		if (pos >= max)
@@ -1126,18 +1129,23 @@
 	if (in.file->f_flags & O_NONBLOCK)
 		fl = SPLICE_F_NONBLOCK;
 #endif
-	retval = do_splice_direct(in.file, ppos, out.file, count, fl);
+	retval = do_splice_direct(in.file, &pos, out.file, &out_pos, count, fl);
 
 	if (retval > 0) {
 		add_rchar(current, retval);
 		add_wchar(current, retval);
 		fsnotify_access(in.file);
 		fsnotify_modify(out.file);
+		out.file->f_pos = out_pos;
+		if (ppos)
+			*ppos = pos;
+		else
+			in.file->f_pos = pos;
 	}
 
 	inc_syscr(current);
 	inc_syscw(current);
-	if (*ppos > max)
+	if (pos > max)
 		retval = -EOVERFLOW;
 
 fput_out: