On Thu, Jun 02, 2016 at 04:19:52PM +1000, Neil Brown wrote: > The 'rdev' fields in each personality's config data are often accessed > under rcu_read_lock() protection to avoid races with > ->hot_remove_disk() removing the rdev. > > Originally this was not necessary during resync/recovery etc because > ->hot_remove_disk() was only called from md_check_recovery(), and it > would only make the call if there was no resync etc happening. > > However we now call ->hot_remove_disk() (from > remove_and_add_spares()) from other contexts, so there could be a race > in the resync code. > > So this patch set adds a lot of extra rcu_read_lock protection and > clean up some other bits and pieces on the way. > > My goal was the final patch. If you have a large raid10 array and > fail half of the devices at once (e.g. unplug a rack with half of the > mirrors) then synchronize_rcu() will be called once for each device, > which can add up to a big delay. A single call should suffice. > The final patch makes that change. Thanks, make a lot of sense. Actually there is bug report related to RCU. https://bugzilla.kernel.org/show_bug.cgi?id=116021 I had the same patch of your patch 3 and the bug submitter is trying. I only had some minor issues, will reply separated. Otherwise this patch set is great. Thanks, Shaohua -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
