Resend, looks like the list does not like html attachments.


This v2 patch is against Christoph's core-for-3.17 branch which
includes scsi-mq V2. Here is a link to a partially updated
version of the scsi_debug html page.
   http://sg.danny.cz/scsi/sdebug26.html


Since v1 of this patch a week ago, this driver has been used
to discover an anomaly in fio and raised questions about the
mid-layer's Task Set Full handling. The addition of sub-jiffy
response delays and control over WCE allows scsi_debug to
better model SSD behaviour.

With fio and four (pseudo) devices I have observed 1.2 M IOPS
on my equipment. Rob Elliott who has done much testing and made
numerous suggestions, has better IOPS results than mine.


ChangeLog v1:
   - add host_lock option whose default value is 0 which
     removes the host_lock around all queued commands
   - accept delay=-1 (_hi_) or -2 which use a tasklet to invoke
     the scsi_done callback into the mid-layer. The default
     is still delay=1 which uses a timer to delay 1 jiffy
   - wire .change_queue_depth and .change_queue_type
     functions to better simulate queueing in a modern LLD
   - add SCSI_DEBUG_OPT_Q_NOISE (0x200) mask to only produce
     debug output associated with queue full, plus from
     .change_queue_depth and .change_queue_type functions
   - add SCSI_DEBUG_OPT_ALL_TSF (0x400) mask which reports
     all queued_arr fulls at TASK_SET_FULL, otherwise
     SCSI_MLQUEUE_HOST_BUSY is returned
   - add SCSI_DEBUG_OPT_RARE_TSF (0x800) mask which works
     together with the every_nth option (> 0) to count
     occurrences of num_in_q==queue_depth. When every_nth
     is reached the victim (a command) yields TASK SET FULL
   - clean up many debug messages.

ChangeLog v2 (since v1):
   - add ndelay=<nanosecs> option that uses high resolution
     timers; active if > 0 and then overrides delay= option
   - expand Unit Attention handling: POR, BUS_RESET and
     MODE PARAMETERS CHANGED
   - support .eh_target_reset_handler and drop .bios_param
   - add OPT_N_WCE mask so caching page yields WCE=0
   - add OPT_RESET_NOISE mask to log aborts and resets
   - add OPT_NO_CDB_NOISE mask to not log each cdb
   - MODE SELECT support for changing caching page's WCE
   - name common ioctls in log
   - when fake_rw=1, do not vmalloc fake store; make
     UNMAP and WRITE SAME obey fake_rw
   - more logging and code improvements including better
     sense buffer handling


Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Tested-by: Robert Elliott <elliott@hp.com>