async_tx: add support for asynchronous RAID6 recovery operations
async_raid6_2data_recov() recovers two data disk failures async_raid6_datap_recov() recovers a data disk and the P disk These routines are a port of the synchronous versions found in drivers/md/raid6recov.c. The primary difference is breaking out the xor operations into separate calls to async_xor. Two helper routines are introduced to perform scalar multiplication where needed. async_sum_product() multiplies two sources by scalar coefficients and then sums (xor) the result. async_mult() simply multiplies a single source by a scalar. This implemention also includes, in contrast to the original synchronous-only code, special case handling for the 4-disk and 5-disk array cases. In these situations the default N-disk algorithm will present 0-source or 1-source operations to dma devices. To cover for dma devices where the minimum source count is 2 we implement 4-disk and 5-disk handling in the recovery code. [ Impact: asynchronous raid6 recovery routines for 2data and datap cases ] Cc: Yuri Tikhonov <yur@emcraft.com> Cc: Ilya Yanok <yanok@emcraft.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: David Woodhouse <David.Woodhouse@intel.com> Reviewed-by: Andre Noll <maan@systemlinux.org> Acked-by: Maciej Sosnowski <maciej.sosnowski@intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
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@ -67,6 +67,10 @@ xor_val - xor a series of source buffers and set a flag if the
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pq - generate the p+q (raid6 syndrome) from a series of source buffers
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pq_val - validate that a p and or q buffer are in sync with a given series of
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sources
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datap - (raid6_datap_recov) recover a raid6 data block and the p block
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from the given sources
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2data - (raid6_2data_recov) recover 2 raid6 data blocks from the given
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sources
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3.3 Descriptor management:
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The return value is non-NULL and points to a 'descriptor' when the operation
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