Hello all, We have a KVM => dm-crypt => dm-thin stack in and a snapshot may have partially completed queued IO out-of-order. EXT4 is giving errors like this after mounting a snapshot, but only on files recently modified near the snapshot time. This might imply out-of-order writes since, presumably, the ext4 journal would handle deletions in journal order and snapshots should be safe at any time: kernel: EXT4-fs error (device dm-2): ext4_lookup:1441: inode #1196093: comm rsync: deleted inode referenced: 1188710 Notably, the ext4 error did not present prior to the snapshot. We have rsync logs from hours before that didn't report this message, but all later rsyncs do. Perhaps related, or perhaps not, crypt_map() notes the following: 1914 * If bio is REQ_FLUSH or REQ_DISCARD, just bypass crypt queues. 1915 * - for REQ_FLUSH device-mapper core ensures that no IO is in-flight 1916 * - for REQ_DISCARD caller must use flush if IO ordering matters However, crypt_map returns DM_MAPIO_SUBMITTED after calling kcryptd_queue_crypt(io) which processes asynchronously on cc->crypto_queue. In crypt_ctr(), alloc_workqueue sets max_active to num_online_cpus() unless 'same_cpu_crypt' is set in the dm table (mine is not), so if I understand correctly, completion could happen out of order with CPUs >1. Does the dm stack know that the bio (dm_crypt_io) hasn't been completed even though it was put on a work queue? If so, I would like to understand that dm bio-tracking mechanism, so please point me at documentation or code. If not, then does crypt_map() need a workqueue_flush(cc->crypto_queue) on REQ_FLUSH? I'm new to the dm-crypt code, so please educate me if I'm missing something here. Thank you for your help! -- Eric Wheeler -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
