Messages in this thread | | | Date | Thu, 23 Mar 2023 13:24:48 -0400 | Subject | Re: [PATCH 0/5]scsi:scsi_debug: Add error injection for single device | From | Douglas Gilbert <> |
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On 2023-03-23 12:25, John Garry wrote: > On 23/03/2023 13:13, haowenchao (C) wrote: >> On 2023/3/23 20:40, John Garry wrote: >>> On 23/03/2023 11:55, Wenchao Hao wrote: >>>> The original error injection mechanism was based on scsi_host which >>>> could not inject fault for a single SCSI device. >>>> >>>> This patchset provides the ability to inject errors for a single >>>> SCSI device. Now we supports inject timeout errors, queuecommand >>>> errors, and hostbyte, driverbyte, statusbyte, and sense data for >>>> specific SCSI Command. >>> >>> There is already a basic mechanism to generate errors - like timeouts - on >>> "nth" command. Can you say why you want this new interface? What special >>> scenarios are you trying to test/validate (which could not be achieved based >>> on the current mechanism)? >>> >> >> I am testing a new error handle policy which is based on single scsi_device >> without set host to RECOVERY. So I need a method to generate errors for >> single SCSI devices. >> >> While we can not generate errors for single device with current mechanism >> because it is designed for host-wide error generation. >> >>> With this series we would have 2x methods to inject errors, which is less >>> than ideal, and they seem to possibly conflict as well, e.g. I set timeout >>> for nth command via current interface and then use the new interface to set >>> timeout for some other cadence. What behavior to expect ...? >> >> I did not take this issue in consideration. I now assume the users would >> not use these 2 methods at same time. >> >> What's more, I don not know where to write the usage of this newly added >> interface, maybe we can explain these in doc? > > sysfs entries are described in Documentation/ABI, but please don't add elaborate > programming interfaces in sysfs files (like in these patches) - a sysfs file > should be just for reading or writing a single value
Hi, Maybe this link might help for scsi_debug documentation: https://doug-gilbert.github.io/scsi_debug.html
And rather than sysfs for complicated, per (pseudo_ device settings, perhaps we could think about a SCSI mechanism like the "Unit Attention" mode page [0x0] which is vendor specific and used by Seagate and WDC for this sort of thing. A framework is already in the scsi_debug driver to change some mode page settings:
# sdparm /dev/sg0 /dev/sg0: Linux scsi_debug 0191 Read write error recovery mode page: AWRE 1 [cha: n, def: 1] ARRE 1 [cha: n, def: 1] PER 0 [cha: n, def: 0] Caching (SBC) mode page: WCE 1 [cha: y, def: 1] RCD 0 [cha: n, def: 0] Control mode page: SWP 0 [cha: n, def: 0] Informational exceptions control mode page: EWASC 0 [cha: n, def: 0] DEXCPT 1 [cha: n, def: 1] MRIE 0 [cha: y, def: 0]
As can be seen WCE and MRIE are changeable, so
# sdparm --clear=WCE /dev/sg0 # sdparm --get=WCE /dev/sg0 /dev/sg0: Linux scsi_debug 0191 WCE 0 [cha: y, def: 1]
Doug Gilbert
>>> I'm not saying that I am a huge fan of the current inject mechanism, but at >>> the very least you need to provide more justification for this series. >>>>> >>>> The first patch add an sysfs interface to add and inquiry single >>>> device's error injection info; the second patch defined how to remove >>>> an injection which has been added. The following 3 patches use the >>>> injection info and generate the related error type. >>>> >>>> Wenchao Hao (5): >>>> scsi:scsi_debug: Add sysfs interface to manage scsi devices' error >>>> injection >>>> scsi:scsi_debug: Define grammar to remove added error injection >>>> scsi:scsi_debug: timeout command if the error is injected >>>> scsi:scsi_debug: Return failed value if the error is injected >>>> scsi:scsi_debug: set command's result and sense data if the error is >>>> injected >>>> >>>> drivers/scsi/scsi_debug.c | 296 ++++++++++++++++++++++++++++++++++++++ >>>> 1 file changed, 296 insertions(+) >>>> >>> >>> >> >
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