• Dan Williams's avatar
    async_tx: add support for asynchronous RAID6 recovery operations · 0a82a623
    Dan Williams authored
     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: default avatarAndre Noll <maan@systemlinux.org>
    Acked-by: default avatarMaciej Sosnowski <maciej.sosnowski@intel.com>
    Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
    
    0a82a623
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