Commit bd2ab670 authored by Dan Williams's avatar Dan Williams Committed by Linus Torvalds
Browse files

md: close a livelock window in handle_parity_checks5 



If a failure is detected after a parity check operation has been initiated,
but before it completes handle_parity_checks5 will never quiesce operations on
the stripe.

Explicitly handle this case by "canceling" the parity check, i.e.  clear the
STRIPE_OP_CHECK flags and queue the stripe on the handle list again to refresh
any non-uptodate blocks.

Kernel versions >= 2.6.23 are susceptible.

Cc: <stable@kernel.org>
Cc: NeilBrown <neilb@suse.de>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 231bc2a2

drivers/md/raid5.c

+29 −22
Original line number Diff line number Diff line
@@ -2348,25 +2348,15 @@ static void handle_issuing_new_write_requests6(raid5_conf_t *conf, 
static void handle_parity_checks5(raid5_conf_t *conf, struct stripe_head *sh,

				struct stripe_head_state *s, int disks)

{

	int canceled_check = 0;



	set_bit(STRIPE_HANDLE, &sh->state);

	/* Take one of the following actions:

	 * 1/ start a check parity operation if (uptodate == disks)

	 * 2/ finish a check parity operation and act on the result

	 * 3/ skip to the writeback section if we previously

	 *    initiated a recovery operation

	 */

	if (s->failed == 0 &&

	    !test_bit(STRIPE_OP_MOD_REPAIR_PD, &sh->ops.pending)) {

		if (!test_and_set_bit(STRIPE_OP_CHECK, &sh->ops.pending)) {

			BUG_ON(s->uptodate != disks);

			clear_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags);

			sh->ops.count++;

			s->uptodate--;

		} else if (

		       test_and_clear_bit(STRIPE_OP_CHECK, &sh->ops.complete)) {



	/* complete a check operation */

	if (test_and_clear_bit(STRIPE_OP_CHECK, &sh->ops.complete)) {

	    clear_bit(STRIPE_OP_CHECK, &sh->ops.ack);

	    clear_bit(STRIPE_OP_CHECK, &sh->ops.pending);



		if (s->failed == 0) {

			if (sh->ops.zero_sum_result == 0)

				/* parity is correct (on disc,

				 * not in buffer any more)
@@ -2391,7 +2381,8 @@ static void handle_parity_checks5(raid5_conf_t *conf, struct stripe_head *sh, 
					s->uptodate++;

				}

			}

		}

		} else

			canceled_check = 1; /* STRIPE_INSYNC is not set */

	}



	/* check if we can clear a parity disk reconstruct */
@@ -2404,10 +2395,26 @@ static void handle_parity_checks5(raid5_conf_t *conf, struct stripe_head *sh, 
		clear_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending);

	}



	/* start a new check operation if there are no failures, the stripe is

	 * not insync, and a repair is not in flight

	 */

	if (s->failed == 0 &&

	    !test_bit(STRIPE_INSYNC, &sh->state) &&

	    !test_bit(STRIPE_OP_MOD_REPAIR_PD, &sh->ops.pending)) {

		if (!test_and_set_bit(STRIPE_OP_CHECK, &sh->ops.pending)) {

			BUG_ON(s->uptodate != disks);

			clear_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags);

			sh->ops.count++;

			s->uptodate--;

		}

	}



	/* Wait for check parity and compute block operations to complete

	 * before write-back

	 * before write-back.  If a failure occurred while the check operation

	 * was in flight we need to cycle this stripe through handle_stripe

	 * since the parity block may not be uptodate

	 */

	if (!test_bit(STRIPE_INSYNC, &sh->state) &&

	if (!canceled_check && !test_bit(STRIPE_INSYNC, &sh->state) &&

	    !test_bit(STRIPE_OP_CHECK, &sh->ops.pending) &&

	    !test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending)) {

		struct r5dev *dev;

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