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: Dan Williams <dan.j.williams@intel.com>
diff --git a/crypto/async_tx/async_xor.c b/crypto/async_tx/async_xor.c
index 1fcf45a..19d16e4 100644
--- a/crypto/async_tx/async_xor.c
+++ b/crypto/async_tx/async_xor.c
@@ -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 @@
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 @@
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);