FAILED: patch "[PATCH] f2fs: fix a problem of using memory after free" failed to apply to 4.4-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.4-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 7855eba4d6102f811b6dd142d6c749f53b591fa3 Mon Sep 17 00:00:00 2001
From: Yunlei He <heyunlei@huawei.com>
Date: Mon, 19 Dec 2016 20:10:48 +0800
Subject: [PATCH] f2fs: fix a problem of using memory after free

This patch fix a problem of using memory after free
in function __try_merge_extent_node.

Fixes: 0f825ee6e873 ("f2fs: add new interfaces for extent tree")
Cc: <stable@vger.kernel.org>
Signed-off-by: Yunlei He <heyunlei@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
index 4db44da7ef69..e02c3d88dc9a 100644
--- a/fs/f2fs/extent_cache.c
+++ b/fs/f2fs/extent_cache.c
@@ -352,11 +352,12 @@ static struct extent_node *__try_merge_extent_node(struct inode *inode,
 	}
 
 	if (next_ex && __is_front_mergeable(ei, &next_ex->ei)) {
-		if (en)
-			__release_extent_node(sbi, et, prev_ex);
 		next_ex->ei.fofs = ei->fofs;
 		next_ex->ei.blk = ei->blk;
 		next_ex->ei.len += ei->len;
+		if (en)
+			__release_extent_node(sbi, et, prev_ex);
+
 		en = next_ex;
 	}