SCSI: SSSRAID: fix the issue that HDD unexpected high latency occured

3snic inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I77ADC


CVE: NA

------------------------------------------

[issue description]
HDD will occur unexpected high latency when pressure, concurrent, time all big enough.
[steps to reproduce the problem]
1. 16 HDDs create 16 bare disks, each disk starts a thread, each thread
   is bound to a core, and the queue depth is 64
2. Issue read & write mixed I/O to the drive letters corresponding to
   rawdrive
3. After the long read and write IO period is completed, observe the
   maximum delay in the printout of the fio tool
[Probability of occurrence]
100%
[Expected results]
The maximum delay in the printout of the FIO tool does not exceed 10 seconds
[Root cause]
Muti-queue implementation will cause high concurrent in each different hardware
dispatch queue is not suitable for HDD.
[Solution]
Introduce work_mode module parameter to fastened total I/O queue number
equal to 1 and maximum concurrent I/O is 4k (according to RAID cured performance)

Signed-off-by: Steven Song <steven.song@3snic.com>
Reviewed-by:  <liangry&lt;liangry1@3snic.com>
Reviewed-by: Jiang <Yu&lt;yujiang@3snic.com>