--- /dev/null
+From 0ea295dd853e0879a9a30ab61f923c26be35b902 Mon Sep 17 00:00:00 2001
+From: Pan Bian <bianpan2016@163.com>
+Date: Thu, 22 Nov 2018 18:58:46 +0800
+Subject: f2fs: read page index before freeing
+
+From: Pan Bian <bianpan2016@163.com>
+
+commit 0ea295dd853e0879a9a30ab61f923c26be35b902 upstream.
+
+The function truncate_node frees the page with f2fs_put_page. However,
+the page index is read after that. So, the patch reads the index before
+freeing the page.
+
+Fixes: bf39c00a9a7f ("f2fs: drop obsolete node page when it is truncated")
+Cc: <stable@vger.kernel.org>
+Signed-off-by: Pan Bian <bianpan2016@163.com>
+Reviewed-by: Chao Yu <yuchao0@huawei.com>
+Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
+Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ fs/f2fs/node.c | 4 +++-
+ 1 file changed, 3 insertions(+), 1 deletion(-)
+
+--- a/fs/f2fs/node.c
++++ b/fs/f2fs/node.c
+@@ -590,6 +590,7 @@ static void truncate_node(struct dnode_o
+ {
+ struct f2fs_sb_info *sbi = F2FS_I_SB(dn->inode);
+ struct node_info ni;
++ pgoff_t index;
+
+ get_node_info(sbi, dn->nid, &ni);
+ if (dn->inode->i_blocks == 0) {
+@@ -613,10 +614,11 @@ invalidate:
+ clear_node_page_dirty(dn->node_page);
+ set_sbi_flag(sbi, SBI_IS_DIRTY);
+
++ index = dn->node_page->index;
+ f2fs_put_page(dn->node_page, 1);
+
+ invalidate_mapping_pages(NODE_MAPPING(sbi),
+- dn->node_page->index, dn->node_page->index);
++ index, index);
+
+ dn->node_page = NULL;
+ trace_f2fs_truncate_node(dn->inode, dn->nid, ni.blk_addr);