From 9ff5d8fe36745867da8a028b3ea58629f7546155 Mon Sep 17 00:00:00 2001
From: Vitaly Mayatskikh <v.mayatskih@gmail.com>
Date: Fri, 22 Sep 2017 01:18:39 -0400
Subject: [PATCH] fix unbalanced page refcounting in bio_map_user_iov

commit 95d78c28b5a85bacbc29b8dba7c04babb9b0d467 upstream.

bio_map_user_iov and bio_unmap_user do unbalanced pages refcounting if
IO vector has small consecutive buffers belonging to the same page.
bio_add_pc_page merges them into one, but the page reference is never
dropped.

Signed-off-by: Vitaly Mayatskikh <v.mayatskih@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
Reading git-format-patch failed