lustre/kernel_patches/patches/raid5-mmp-unplug-dev-rhel6.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-2.6.32-71.18.1.el6-master/drivers/md/raid5.c
   7 ===================================================================
   8 --- linux-2.6.32-71.18.1.el6-master.orig/drivers/md/raid5.c     2011-02-28 16:57:31.222666050 +0800
   9 +++ linux-2.6.32-71.18.1.el6-master/drivers/md/raid5.c  2011-02-28 16:58:27.011983275 +0800
  10 @@ -2098,6 +2098,8 @@
  11                 bi->bi_next = *bip;
  12         *bip = bi;
  13         bi->bi_phys_segments++;
  14 +       if (bio_rw_flagged(bi, BIO_RW_SYNCIO) && !forwrite)
  15 +               clear_bit(R5_UPTODATE, &sh->dev[dd_idx].flags); /* force to read from disk. */
  16         spin_unlock_irq(&conf->device_lock);
  17         spin_unlock(&sh->lock);
  18
  19 @@ -4031,6 +4033,8 @@
  20                 wait_event(mddev->thread->wqueue,
  21                            atomic_read(&conf->preread_active_stripes) == 0);
  22         }
  23 +       if (bio_rw_flagged(bi, BIO_RW_SYNCIO))
  24 +               raid5_unplug_device(mddev->queue);
  25         return 0;
  26  }
  27