Patch "ext4: unmap metadata when zeroing blocks" has been added to the 4.7-stable tree

Patch "ext4: unmap metadata when zeroing blocks" has been added to the 4.7-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    ext4: unmap metadata when zeroing blocks

to the 4.7-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ext4-unmap-metadata-when-zeroing-blocks.patch
and it can be found in the queue-4.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 9b623df614576680cadeaa4d7e0b5884de8f7c17 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Fri, 30 Sep 2016 02:02:29 -0400
Subject: ext4: unmap metadata when zeroing blocks

From: Jan Kara <jack@suse.cz>

commit 9b623df614576680cadeaa4d7e0b5884de8f7c17 upstream.

When zeroing blocks for DAX allocations, we also have to unmap aliases
in the block device mappings.  Otherwise writeback can overwrite zeros
with stale data from block device page cache.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/ext4/inode.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -647,11 +647,19 @@ found:
 		/*
 		 * We have to zeroout blocks before inserting them into extent
 		 * status tree. Otherwise someone could look them up there and
-		 * use them before they are really zeroed.
+		 * use them before they are really zeroed. We also have to
+		 * unmap metadata before zeroing as otherwise writeback can
+		 * overwrite zeros with stale data from block device.
 		 */
 		if (flags & EXT4_GET_BLOCKS_ZERO &&
 		    map->m_flags & EXT4_MAP_MAPPED &&
 		    map->m_flags & EXT4_MAP_NEW) {
+			ext4_lblk_t i;
+
+			for (i = 0; i < map->m_len; i++) {
+				unmap_underlying_metadata(inode->i_sb->s_bdev,
+							  map->m_pblk + i);
+			}
 			ret = ext4_issue_zeroout(inode, map->m_lblk,
 						 map->m_pblk, map->m_len);
 			if (ret) {


Patches currently in stable-queue which might be from jack@suse.cz are

queue-4.7/ext4-allow-dax-writeback-for-hole-punch.patch
queue-4.7/reiserfs-unlock-superblock-before-calling-reiserfs_quota_on_mount.patch
queue-4.7/ext4-unmap-metadata-when-zeroing-blocks.patch