• Nathaniel W. Turner's avatar
    xfs: copy li_lsn before dropping AIL lock · 6c06f072
    Nathaniel W. Turner authored
    Access to log items on the AIL is generally protected by m_ail_lock;
    this is particularly needed when we're getting or setting the 64-bit
    li_lsn on a 32-bit platform.  This patch fixes a couple places where we
    were accessing the log item after dropping the AIL lock on 32-bit
    machines.
    
    This can result in a partially-zeroed log->l_tail_lsn if
    xfs_trans_ail_delete is racing with xfs_trans_ail_update, and in at
    least some cases, this can leave the l_tail_lsn with a zero cycle
    number, which means xlog_space_left will think the log is full (unless
    CONFIG_XFS_DEBUG is set, in which case we'll trip an ASSERT), leading to
    processes stuck forever in xlog_grant_log_space.
    
    Thanks to Adrian VanderSpek for first spotting the race potential and to
    Dave Chinner for debug assistance.
    Signed-off-by: default avatarNathaniel W. Turner <nate@houseofnate.net>
    Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
    Signed-off-by: default avatarAlex Elder <aelder@sgi.com>
    6c06f072
xfs_trans_ail.c 19.1 KB