Commit ee042ec8 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'md/3.17-final-fix' of git://neil.brown.name/md 

Pull raid5 discard fix from Neil Brown:
 "One fix for raid5 discard issue"

* tag 'md/3.17-final-fix' of git://neil.brown.name/md:
  md/raid5: disable 'DISCARD' by default due to safety concerns.
parents 80ad99da 8e0e99ba

drivers/md/raid5.c

+17 −1
Original line number Diff line number Diff line
@@ -64,6 +64,10 @@ 
#define cpu_to_group(cpu) cpu_to_node(cpu)

#define ANY_GROUP NUMA_NO_NODE



static bool devices_handle_discard_safely = false;

module_param(devices_handle_discard_safely, bool, 0644);

MODULE_PARM_DESC(devices_handle_discard_safely,

		 "Set to Y if all devices in each array reliably return zeroes on reads from discarded regions");

static struct workqueue_struct *raid5_wq;

/*

 * Stripe cache
@@ -6208,7 +6212,7 @@ static int run(struct mddev *mddev) 
		mddev->queue->limits.discard_granularity = stripe;

		/*

		 * unaligned part of discard request will be ignored, so can't

		 * guarantee discard_zerors_data

		 * guarantee discard_zeroes_data

		 */

		mddev->queue->limits.discard_zeroes_data = 0;
@@ -6233,6 +6237,18 @@ static int run(struct mddev *mddev) 
			    !bdev_get_queue(rdev->bdev)->

						limits.discard_zeroes_data)

				discard_supported = false;

			/* Unfortunately, discard_zeroes_data is not currently

			 * a guarantee - just a hint.  So we only allow DISCARD

			 * if the sysadmin has confirmed that only safe devices

			 * are in use by setting a module parameter.

			 */

			if (!devices_handle_discard_safely) {

				if (discard_supported) {

					pr_info("md/raid456: discard support disabled due to uncertainty.\n");

					pr_info("Set raid456.devices_handle_discard_safely=Y to override.\n");

				}

				discard_supported = false;

			}

		}



		if (discard_supported &&