[PATCH 3.16 16/99] f2fs: read page index before freeing

[Ben Hutchings]

3.16.65-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Pan Bian <bianpan2016@xxxxxxx>

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")
Signed-off-by: Pan Bian <bianpan2016@xxxxxxx>
Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>
Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 fs/f2fs/node.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -509,6 +509,7 @@ static void truncate_node(struct dnode_o
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(dn->inode->i_sb);
 	struct node_info ni;
+	pgoff_t index;
 
 	get_node_info(sbi, dn->nid, &ni);
 	if (dn->inode->i_blocks == 0) {
@@ -532,10 +533,11 @@ invalidate:
 	clear_node_page_dirty(dn->node_page);
 	F2FS_SET_SB_DIRT(sbi);
 
+	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);