lustre/kernel_patches/patches/raid5-mmp-unplug-dev-sles11sp1.patch

   1 Force MD devices to pass SYNC reads directly to the disk
   2 instead of handling from cache.  This is needed for MMP
   3 on MD RAID devices, and in theory could be accepted in
   4 the upstream kernel.  Not needed for DMU.
   5
   6 Index: linux-2.6.32/drivers/md/raid5.c
   7 ===================================================================
   8 --- linux-2.6.32.orig/drivers/md/raid5.c        2012-06-22 06:09:49.000000000 -0400
   9 +++ linux-2.6.32/drivers/md/raid5.c     2013-01-25 10:11:10.076431000 -0500
  10 @@ -2169,6 +2169,9 @@ static int add_stripe_bio(struct stripe_
  11                 bi->bi_next = *bip;
  12         *bip = bi;
  13         bi->bi_phys_segments++;
  14 +       /* force to read from disk. */
  15 +       if ((bi->bi_rw & REQ_RW_SYNC) && !forwrite)
  16 +               clear_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
  17         spin_unlock_irq(&conf->device_lock);
  18         spin_unlock(&sh->lock);
  19
  20 @@ -4008,6 +4008,10 @@ static int make_request(mddev_t *mddev,
  21
  22                 bio_endio(bi, 0);
  23         }
  24 +
  25 +       if (bi->bi_rw & REQ_RW_SYNC)
  26 +               md_wakeup_thread(mddev->thread);
  27 +
  28         return 0;
  29  }
  30