• Z
    jbd2: clear dirty flag when revoking a buffer from an older transaction · dbe4bc99
    zhangyi (F) 提交于
    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: Nzhangyi (F) <yi.zhang@huawei.com>
    Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
    Reviewed-by: NJan Kara <jack@suse.cz>
    Cc: stable@vger.kernel.org
    Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    dbe4bc99
transaction.c 80.2 KB