jbd2: clear dirty flag when revoking a buffer from an older transaction
authorzhangyi (F) <yi.zhang@huawei.com>
Mon, 11 Feb 2019 04:23:04 +0000 (23:23 -0500)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sat, 23 Mar 2019 13:35:25 +0000 (14:35 +0100)
commit8c87c8633163f92f141b66556473332eb49e78f0
tree0cc828a3dce3dbb553713875b94523d229c14626
parent05d787ebe2f02b734e32b61d3ebfc024ae996683
jbd2: clear dirty flag when revoking a buffer from an older transaction

commit 904cdbd41d749a476863a0ca41f6f396774f26e4 upstream.

Now, we capture a data corruption problem on ext4 while we're truncating
an extent index block. Imaging that if we are revoking a buffer which
has been journaled by the committing transaction, the buffer's jbddirty
flag will not be cleared in jbd2_journal_forget(), so the commit code
will set the buffer dirty flag again after refile the buffer.

fsx                               kjournald2
                                  jbd2_journal_commit_transaction
jbd2_journal_revoke                commit phase 1~5...
 jbd2_journal_forget
   belongs to older transaction    commit phase 6
   jbddirty not clear               __jbd2_journal_refile_buffer
                                     __jbd2_journal_unfile_buffer
                                      test_clear_buffer_jbddirty
                                       mark_buffer_dirty

Finally, if the freed extent index block was allocated again as data
block by some other files, it may corrupt the file data after writing
cached pages later, such as during unmount time. (In general,
clean_bdev_aliases() related helpers should be invoked after
re-allocation to prevent the above corruption, but unfortunately we
missed it when zeroout the head of extra extent blocks in
ext4_ext_handle_unwritten_extents()).

This patch mark buffer as freed and set j_next_transaction to the new
transaction when it already belongs to the committing transaction in
jbd2_journal_forget(), so that commit code knows it should clear dirty
bits when it is done with the buffer.

This problem can be reproduced by xfstests generic/455 easily with
seeds (3246 3247 3248 3249).

Signed-off-by: zhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
fs/jbd2/transaction.c