md: handle operation chaining in raid5_run_ops (7b3a871e) · Commits · 戴 / test

From: Dan Williams <dan.j.williams@intel.com> Neil said: > At the end of ops_run_compute5 you have: > /* ack now if postxor is not set to be run */ > if (tx && !test_bit(STRIPE_OP_POSTXOR, &s->ops_run)) > async_tx_ack(tx); > > It looks odd having that test there. Would it fit in raid5_run_ops > better? The intended global interpretation is that raid5_run_ops can build a chain of xor and memcpy operations. When MD registers the compute-xor it tells async_tx to keep the operation handle around so that another item in the dependency chain can be submitted. If we are just computing a block to satisfy a read then we can terminate the chain immediately. raid5_run_ops gives a better context for this test since it cares about the entire chain. Signed-off-by:

Dan Williams <dan.j.williams@intel.com> Signed-off-by:

Neil Brown <neilb@suse.de>

drivers/md/raid5.c

+7 −8

Original line number	Diff line number	Diff line
		@@ -574,8 +574,7 @@ static void ops_complete_compute5(void *stripe_head_ref)
		release_stripe(sh);
		}

		static struct dma_async_tx_descriptor *
		ops_run_compute5(struct stripe_head *sh, unsigned long ops_request)
		static struct dma_async_tx_descriptor ops_run_compute5(struct stripe_head sh)
		{
		/* kernel stack size limits the total number of disks */
		int disks = sh->disks;
		@@ -605,10 +604,6 @@ ops_run_compute5(struct stripe_head *sh, unsigned long ops_request)
		ASYNC_TX_XOR_ZERO_DST, NULL,
		ops_complete_compute5, sh);

		/* ack now if postxor is not set to be run */
		if (tx && !test_bit(STRIPE_OP_POSTXOR, &ops_request))
		async_tx_ack(tx);

		return tx;
		}

		@@ -813,8 +808,12 @@ static void raid5_run_ops(struct stripe_head *sh, unsigned long ops_request)
		overlap_clear++;
		}

		if (test_bit(STRIPE_OP_COMPUTE_BLK, &ops_request))
		tx = ops_run_compute5(sh, ops_request);
		if (test_bit(STRIPE_OP_COMPUTE_BLK, &ops_request)) {
		tx = ops_run_compute5(sh);
		/* terminate the chain if postxor is not set to be run */
		if (tx && !test_bit(STRIPE_OP_POSTXOR, &ops_request))
		async_tx_ack(tx);
		}

		if (test_bit(STRIPE_OP_PREXOR, &ops_request))
		tx = ops_run_prexor(sh, tx);

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