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    [SCSI] aacraid: fix driver failure with Dell PowerEdge Expandable RAID Controller 3/Di · 94cf6ba1
    Salyzyn, Mark 提交于
    As reported in http://bugzilla.kernel.org/show_bug.cgi?id=3D9133 it was
    discovered that the PERC line of controllers lacked a key 64 bit
    ScatterGather capable SCSI pass-through function. The adapters are still
    capable of 64 bit ScatterGather I/O commands, but these two can not be
    mixed. This problem was exacerbated by the introduction of the SCSI
    Generic access to the DASD physical devices.
    
    The fix for users before this patch is applied is aacraid.dacmode=3D0 on
    the kernel command line to disable 64 bit I/O.
    
    The enclosed patch introduces a new adapter quirk and tries to limp
    along by enabling pass-through in situations where memory is 32 bit
    addressable on 64 bit machines, or disable the pass-through functions
    altogether. I expect that the check for 32 bit addressable memory to be
    controversial in that it can be incorrect in non-Dell non-Intel systems
    that PERC would never be installed under, the alternative is to disable
    pass-through in all cases which could be reported as another regression.
    
    Pass-through is used for SCSI Generic access to the physical devices, or
    for the management applications to properly function.
    
    In systems where this patch has disabled pass-through because it is
    unsupportable in combination with I/O performance, the user can choose
    to enable pass-through by turning off dacmode (aacraid.dacmode=3D0) or
    limiting the discovered kernel memory (mem=3D4G) with an associated loss
    in runtime performance. If we chose instead to turn off 64 bit dacmode
    for the adapters with this quirk, then this would be reported as another
    regression.
    Signed-off-by: NMark Salyzyn <aacraid@adaptec.com>
    Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>
    94cf6ba1
linit.c 40.7 KB