src/patches/suse-2.6.27.31/patches.fixes/blk-dont-invoke-request_fn-on-stopped-queue

   1 Subject: block: only call ->request_fn when the queue is not stopped
   2 From: Jens Axboe <jens.axboe@oracle.com>
   3 Date: Fri Oct 17 08:46:57 2008 +0200:
   4 Git: 80a4b58e36b63d7b0b592beb1bd6410aadeeb63c
   5 References: bnc#457041
   6
   7 Callers should use either blk_run_queue/__blk_run_queue, or
   8 blk_start_queueing() to invoke request handling instead of calling
   9 ->request_fn() directly as that does not take the queue stopped
  10 flag into account.
  11
  12 Also add appropriate comments on the above functions to detail
  13 their usage.
  14
  15 Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
  16 Signed-off-by: Hannes Reinecke <hare@suse.de>
  17
  18 ---
  19  block/blk-core.c |   19 +++++++++++++++++--
  20  block/elevator.c |    7 +++----
  21  2 files changed, 20 insertions(+), 6 deletions(-)
  22
  23 --- a/block/blk-core.c
  24 +++ b/block/blk-core.c
  25 @@ -324,6 +324,9 @@ EXPORT_SYMBOL(blk_unplug);
  26
  27  static void blk_invoke_request_fn(struct request_queue *q)
  28  {
  29 +       if (unlikely(blk_queue_stopped(q)))
  30 +               return;
  31 +
  32         /*
  33          * one level of recursion is ok and is much faster than kicking
  34          * the unplug handling
  35 @@ -399,8 +402,13 @@ void blk_sync_queue(struct request_queue
  36  EXPORT_SYMBOL(blk_sync_queue);
  37
  38  /**
  39 - * blk_run_queue - run a single device queue
  40 + * __blk_run_queue - run a single device queue
  41   * @q: The queue to run
  42 + *
  43 + * Description:
  44 + *    See @blk_run_queue. This variant must be called with the queue lock
  45 + *    held and interrupts disabled.
  46 + *
  47   */
  48  void __blk_run_queue(struct request_queue *q)
  49  {
  50 @@ -418,6 +426,12 @@ EXPORT_SYMBOL(__blk_run_queue);
  51  /**
  52   * blk_run_queue - run a single device queue
  53   * @q: The queue to run
  54 + *
  55 + * Description:
  56 + *    Invoke request handling on this queue, if it has pending work to do.
  57 + *    May be used to restart queueing when a request has completed. Also
  58 + *    See @blk_start_queueing.
  59 + *
  60   */
  61  void blk_run_queue(struct request_queue *q)
  62  {
  63 @@ -883,7 +897,8 @@ EXPORT_SYMBOL(blk_get_request);
  64   *
  65   * This is basically a helper to remove the need to know whether a queue
  66   * is plugged or not if someone just wants to initiate dispatch of requests
  67 - * for this queue.
  68 + * for this queue. Should be used to start queueing on a device outside
  69 + * of ->request_fn() context. Also see @blk_run_queue.
  70   *
  71   * The queue lock must be held with interrupts disabled.
  72   */
  73 --- a/block/elevator.c
  74 +++ b/block/elevator.c
  75 @@ -620,7 +620,7 @@ void elv_insert(struct request_queue *q,
  76                  *   processing.
  77                  */
  78                 blk_remove_plug(q);
  79 -               q->request_fn(q);
  80 +               blk_start_queueing(q);
  81                 break;
  82
  83         case ELEVATOR_INSERT_SORT:
  84 @@ -951,7 +951,7 @@ void elv_completed_request(struct reques
  85                     blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
  86                     blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {
  87                         blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
  88 -                       q->request_fn(q);
  89 +                       blk_start_queueing(q);
  90                 }
  91         }
  92  }
  93 @@ -1110,8 +1110,7 @@ static int elevator_switch(struct reques
  94         elv_drain_elevator(q);
  95
  96         while (q->rq.elvpriv) {
  97 -               blk_remove_plug(q);
  98 -               q->request_fn(q);
  99 +               blk_start_queueing(q);
 100                 spin_unlock_irq(q->queue_lock);
 101                 msleep(10);
 102                 spin_lock_irq(q->queue_lock);