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Commit 9b623df6 authored by Jan Kara's avatar Jan Kara Committed by Theodore Ts'o
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ext4: unmap metadata when zeroing blocks 



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: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
parent 51e8137b

fs/ext4/inode.c

+9 −1
Original line number Diff line number Diff line
@@ -647,11 +647,19 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode, 
		/*

		 * 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) {