FAILED: patch "[PATCH] f2fs: read page index before freeing" failed to apply to 4.14-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

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: [PATCH] f2fs: read page index before freeing

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>

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index e60c7779e114..a2273340991f 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -826,6 +826,7 @@ static int truncate_node(struct dnode_of_data *dn)
 	struct f2fs_sb_info *sbi = F2FS_I_SB(dn->inode);
 	struct node_info ni;
 	int err;
+	pgoff_t index;
 
 	err = f2fs_get_node_info(sbi, dn->nid, &ni);
 	if (err)
@@ -845,10 +846,11 @@ static int truncate_node(struct dnode_of_data *dn)
 	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);