fuse: don't bump attr_version in cached write

The attribute version in fuse_inode should be updated whenever the
attributes might have changed on the server.  In case of cached writes this
is not the case, so updating the attr_version is unnecessary and could
possibly affect performance.

Open code the remaining part of fuse_write_update_size().
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/fuse/file.c

@@ -2309,15 +2309,18 @@ static int fuse_write_end(struct file *file, struct address_space *mapping,
 	if (!copied)
 		goto unlock;
 
+	pos += copied;
 	if (!PageUptodate(page)) {
 		/* Zero any unwritten bytes at the end of the page */
-		size_t endoff = (pos + copied) & ~PAGE_MASK;
+		size_t endoff = pos & ~PAGE_MASK;
 		if (endoff)
 			zero_user_segment(page, endoff, PAGE_SIZE);
 		SetPageUptodate(page);
 	}
 
-	fuse_write_update_size(inode, pos + copied);
+	if (pos > inode->i_size)
+		i_size_write(inode, pos);
+
 	set_page_dirty(page);
 
 unlock: