1. 31 Mar, 2015 1 commit
    • Mike Snitzer's avatar
      block: fix blk_stack_limits() regression due to lcm() change · e9637415
      Mike Snitzer authored
      Linux 3.19 commit 69c953c8 ("lib/lcm.c: lcm(n,0)=lcm(0,n) is 0, not n")
      caused blk_stack_limits() to not properly stack queue_limits for stacked
      devices (e.g. DM).
      
      Fix this regression by establishing lcm_not_zero() and switching
      blk_stack_limits() over to using it.
      
      DM uses blk_set_stacking_limits() to establish the initial top-level
      queue_limits that are then built up based on underlying devices' limits
      using blk_stack_limits().  In the case of optimal_io_size (io_opt)
      blk_set_stacking_limits() establishes a default value of 0.  With commit
      69c953c8, lcm(0, n) is no longer n, which compromises proper stacking of
      the underlying devices' io_opt.
      
      Test:
      $ modprobe scsi_debug dev_size_mb=10 num_tgts=1 opt_blks=1536
      $ cat /sys/block/sde/queue/optimal_io_size
      786432
      $ dmsetup create node --table "0 100 linear /dev/sde 0"
      
      Before this fix:
      $ cat /sys/block/dm-5/queue/optimal_io_size
      0
      
      After this fix:
      $ cat /sys/block/dm-5/queue/optimal_io_size
      786432
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      Cc: stable@vger.kernel.org # 3.19+
      Acked-by: Martin K. Petersen's avatarMartin K. Petersen <martin.petersen@oracle.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      e9637415
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