Commit 669ab0b2 authored by Dan Williams's avatar Dan Williams
Browse files

async_tx: fix handling of the "out of descriptor" condition in async_xor 



Ensure forward progress is made when a dmaengine driver is unable to
allocate an xor descriptor by breaking the dependency chain with
async_tx_quisce() and issue any pending descriptors.

Tested with iop-adma by setting device->max_xor = 2 to force multiple
calls to device_prep_dma_xor for each call to async_xor and limiting the
descriptor slot pool to 5.  Discovered that the minimum descriptor pool
size for iop-adma is 2 * iop_chan_xor_slot_cnt(device->max_xor) + 1.

Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent 1e55db2d

crypto/async_tx/async_xor.c

+26 −6
Original line number Diff line number Diff line
@@ -30,6 +30,24 @@ 
#include <linux/raid/xor.h>

#include <linux/async_tx.h>



/**

 * async_tx_quiesce - ensure tx is complete and freeable upon return

 * @tx - transaction to quiesce

 */

static void async_tx_quiesce(struct dma_async_tx_descriptor **tx)

{

	if (*tx) {

		/* if ack is already set then we cannot be sure

		 * we are referring to the correct operation

		 */

		BUG_ON(async_tx_test_ack(*tx));

		if (dma_wait_for_async_tx(*tx) == DMA_ERROR)

			panic("DMA_ERROR waiting for transaction\n");

		async_tx_ack(*tx);

		*tx = NULL;

       }

}



/* do_async_xor - dma map the pages and perform the xor with an engine.

 * 	This routine is marked __always_inline so it can be compiled away

 * 	when CONFIG_DMA_ENGINE=n
@@ -85,15 +103,17 @@ do_async_xor(struct dma_chan *chan, struct page *dest, struct page **src_list, 
		tx = dma->device_prep_dma_xor(chan, dma_dest, &dma_src[src_off],

					      xor_src_cnt, len, dma_flags);



		if (unlikely(!tx && depend_tx))

			dma_wait_for_async_tx(depend_tx);

		if (unlikely(!tx))

			async_tx_quiesce(&depend_tx);



		/* spin wait for the preceeding transactions to complete */

		while (unlikely(!tx))

		while (unlikely(!tx)) {

			dma_async_issue_pending(chan);

			tx = dma->device_prep_dma_xor(chan, dma_dest,

						      &dma_src[src_off],

						      xor_src_cnt, len,

						      dma_flags);

		}



		async_tx_submit(chan, tx, async_flags, depend_tx, _cb_fn,

				_cb_param);
@@ -267,11 +287,11 @@ async_xor_zero_sum(struct page *dest, struct page **src_list, 
		tx = device->device_prep_dma_zero_sum(chan, dma_src, src_cnt,

						      len, result,

						      dma_prep_flags);

		if (!tx) {

			if (depend_tx)

				dma_wait_for_async_tx(depend_tx);

		if (unlikely(!tx)) {

			async_tx_quiesce(&depend_tx);



			while (!tx)

				dma_async_issue_pending(chan);

				tx = device->device_prep_dma_zero_sum(chan,

					dma_src, src_cnt, len, result,

					dma_prep_flags);

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