Re: [PATCH] ib_srp: Avoid that LUN scanning creates duplicate devices

[Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>]

On Sat, Jun 25, 2011 at 10:10:30AM +0200, Bart Van Assche wrote:
> SCSI scanning of a channel:id:lun triplet in Linux works as follows (function
> scsi_scan_target() in drivers/scsi/scsi_scan.c):
> - If lun == SCAN_WILD_CARD, send a REPORT LUNS command to the target and
>   process the result.
> - If lun != SCAN_WILD_CARD, send an INQUIRY command to the LUN corresponding
>   to the specified channel:id:lun triplet to verify whether the LUN exists.
> So a SCSI driver must either take the channel and target id values in account
> in its quecommand() function or it should declare that it only supports one
> channel and one target id. Currently the ib_srp driver does neither. As a
> result scanning the SCSI bus via e.g. rescan-scsi-bus.sh causes many
> duplicate SCSI devices to be created. For each 0:0:L device, several
> duplicates are created with the same LUN number and with (C:I) != (0:0). Fix
> this by declaring that the ib_srp driver only supports one channel and one
> target id.

Looks good.  We should probably consider chosing sane defaults at least
for max_channel, but for now this is the best fix.

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