On Mon, Jul 09 2012 at 9:00am -0400, Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > On Sun, Jul 08 2012 at 1:59pm -0400, > Chauhan, Vijay <Vijay.Chauhan@xxxxxxxxxx> wrote: > > > Even though underlying paths are set with larger value for max_sectors, dm > > sets 1024(i.e 512KB) for max_sectors as default. max_sectors for dm > > device can be reset through sysfs but any time map is updated, max_sectors > > is again set back to default. This patch gets the minimum of max_sectors from > > physical paths and sets it to dm device. > > There shouldn't be any need for additional DM overrides for max_sectors. > > DM will stack the limits for all underlying devices each table reload > (via dm_calculate_queue_limits). And max_sectors is properly stacked in > the block layer's bdev_stack_limits (called by dm_set_device_limits). > > So is something resetting max_sectors with sysfs? multipathd? BLK_DEF_MAX_SECTORS = 1024 blk_set_stacking_limits: lim->max_sectors = BLK_DEF_MAX_SECTORS But that just establishes the default, the stacking done by blk_stack_limits will reduce 'max_sectors' accordingly based on the underlying paths' max_sectors. I can clearly see that max_sectors is reduced according to the underlying device(s): # multipath -ll mpathe (36003005700ec1890167a7e5953effb87) dm-5 LSI,RAID 5/6 SAS 6G size=465G features='0' hwhandler='0' wp=rw `-+- policy='round-robin 0' prio=1 status=active `- 0:2:4:0 sde 8:64 active ready running # cat /sys/block/sde/queue/max_sectors_kb 240 # cat /sys/block/dm-5/queue/max_sectors_kb 240 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
