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

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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>
This commit is contained in:
Dan Williams 2008-07-17 17:59:55 -07:00
parent 1e55db2d6b
commit 669ab0b210
1 changed files with 26 additions and 6 deletions
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32
crypto/async_tx/async_xor.c
View file

@ -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);