1. 07 1月, 2011 5 次提交
  2. 05 1月, 2011 2 次提交
    • J
      block: fix accounting bug on cross partition merges · 09e099d4
      Jerome Marchand 提交于
      /proc/diskstats would display a strange output as follows.
      
      $ cat /proc/diskstats |grep sda
         8       0 sda 90524 7579 102154 20464 0 0 0 0 0 14096 20089
         8       1 sda1 19085 1352 21841 4209 0 0 0 0 4294967064 15689 4293424691
                                                      ~~~~~~~~~~
         8       2 sda2 71252 3624 74891 15950 0 0 0 0 232 23995 1562390
         8       3 sda3 54 487 2188 92 0 0 0 0 0 88 92
         8       4 sda4 4 0 8 0 0 0 0 0 0 0 0
         8       5 sda5 81 2027 2130 138 0 0 0 0 0 87 137
      
      Its reason is the wrong way of accounting hd_struct->in_flight. When a bio is
      merged into a request belongs to different partition by ELEVATOR_FRONT_MERGE.
      
      The detailed root cause is as follows.
      
      Assuming that there are two partition, sda1 and sda2.
      
      1. A request for sda2 is in request_queue. Hence sda1's hd_struct->in_flight
         is 0 and sda2's one is 1.
      
              | hd_struct->in_flight
         ---------------------------
         sda1 |          0
         sda2 |          1
         ---------------------------
      
      2. A bio belongs to sda1 is issued and is merged into the request mentioned on
         step1 by ELEVATOR_BACK_MERGE. The first sector of the request is changed
         from sda2 region to sda1 region. However the two partition's
         hd_struct->in_flight are not changed.
      
              | hd_struct->in_flight
         ---------------------------
         sda1 |          0
         sda2 |          1
         ---------------------------
      
      3. The request is finished and blk_account_io_done() is called. In this case,
         sda2's hd_struct->in_flight, not a sda1's one, is decremented.
      
              | hd_struct->in_flight
         ---------------------------
         sda1 |         -1
         sda2 |          1
         ---------------------------
      
      The patch fixes the problem by caching the partition lookup
      inside the request structure, hence making sure that the increment
      and decrement will always happen on the same partition struct. This
      also speeds up IO with accounting enabled, since it cuts down on
      the number of lookups we have to do.
      
      Also add a refcount to struct hd_struct to keep the partition in
      memory as long as users exist. We use kref_test_and_get() to ensure
      we don't add a reference to a partition which is going away.
      Signed-off-by: NJerome Marchand <jmarchan@redhat.com>
      Signed-off-by: NYasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
      Cc: stable@kernel.org
      Signed-off-by: NJens Axboe <jaxboe@fusionio.com>
      09e099d4
    • J
      kref: add kref_test_and_get · e4a683c8
      Jerome Marchand 提交于
      Add kref_test_and_get() function, which atomically add a reference only if
      refcount is not zero. This prevent to add a reference to an object that is
      already being removed.
      Signed-off-by: NJerome Marchand <jmarchan@redhat.com>
      Cc: stable@kernel.org
      Signed-off-by: NJens Axboe <jaxboe@fusionio.com>
      e4a683c8
  3. 03 1月, 2011 2 次提交
  4. 21 12月, 2010 1 次提交
  5. 20 12月, 2010 1 次提交
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  7. 13 12月, 2010 1 次提交
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  9. 28 11月, 2010 1 次提交
  10. 16 11月, 2010 21 次提交