1. 10 Apr, 2009 7 commits
  2. 09 Apr, 2009 29 commits
  3. 08 Apr, 2009 4 commits
    • Mikulas Patocka's avatar
      dm kcopyd: fix callback race · 340cd444
      Mikulas Patocka authored
      If the thread calling dm_kcopyd_copy is delayed due to scheduling inside
      split_job/segment_complete and the subjobs complete before the loop in
      split_job completes, the kcopyd callback could be invoked from the
      thread that called dm_kcopyd_copy instead of the kcopyd workqueue.
      
      dm_kcopyd_copy -> split_job -> segment_complete -> job->fn()
      
      Snapshots depend on the fact that callbacks are called from the singlethreaded
      kcopyd workqueue and expect that there is no racing between individual
      callbacks. The racing between callbacks can lead to corruption of exception
      store and it can also mean that exception store callbacks are called twice
      for the same exception - a likely reason for crashes reported inside
      pending_complete() / remove_exception().
      
      This patch fixes two problems:
      
      1. job->fn being called from the thread that submitted the job (see above).
      
      - Fix: hand over the completion callback to the kcopyd thread.
      
      2. job->fn(read_err, write_err, job->context); in segment_complete
      reports the error of the last subjob, not the union of all errors.
      
      - Fix: pass job->write_err to the callback to report all error bits
        (it is done already in run_complete_job)
      
      Cc: stable@kernel.org
      Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
      Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
      340cd444
    • Mikulas Patocka's avatar
      dm kcopyd: prepare for callback race fix · 73830857
      Mikulas Patocka authored
      Use a variable in segment_complete() to point to the dm_kcopyd_client
      struct and only release job->pages in run_complete_job() if any are
      defined.  These changes are needed by the next patch.
      
      Cc: stable@kernel.org
      Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
      Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
      73830857
    • Mikulas Patocka's avatar
      dm: implement basic barrier support · af7e466a
      Mikulas Patocka authored
      Barriers are submitted to a worker thread that issues them in-order.
      
      The thread is modified so that when it sees a barrier request it waits
      for all pending IO before the request then submits the barrier and
      waits for it.  (We must wait, otherwise it could be intermixed with
      following requests.)
      
      Errors from the barrier request are recorded in a per-device barrier_error
      variable. There may be only one barrier request in progress at once.
      
      For now, the barrier request is converted to a non-barrier request when
      sending it to the underlying device.
      
      This patch guarantees correct barrier behavior if the underlying device
      doesn't perform write-back caching. The same requirement existed before
      barriers were supported in dm.
      
      Bottom layer barrier support (sending barriers by target drivers) and
      handling devices with write-back caches will be done in further patches.
      Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
      Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
      af7e466a
    • Mikulas Patocka's avatar
      dm: remove dm_request loop · 92c63902
      Mikulas Patocka authored
      Remove queue_io return value and a loop in dm_request.
      
      IO may be submitted to a worker thread with queue_io().  queue_io() sets
      DMF_QUEUE_IO_TO_THREAD so that all further IO is queued for the thread. When
      the thread finishes its work, it clears DMF_QUEUE_IO_TO_THREAD and from this
      point on, requests are submitted from dm_request again. This will be used
      for processing barriers.
      
      Remove the loop in dm_request. queue_io() can submit I/Os to the worker thread
      even if DMF_QUEUE_IO_TO_THREAD was not set.
      Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
      Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
      92c63902