From: Hannes Reinecke <hare@suse.de>
To: Bart Van Assche <bvanassche@acm.org>,
John Garry <john.garry@huawei.com>,
"Martin K . Petersen" <martin.petersen@oracle.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>,
Adrian Hunter <adrian.hunter@intel.com>,
linux-scsi@vger.kernel.org,
"James E.J. Bottomley" <jejb@linux.ibm.com>
Subject: Re: [PATCH v2 05/20] scsi: core: Add support for internal commands
Date: Wed, 24 Nov 2021 07:33:17 +0100 [thread overview]
Message-ID: <f0e13859-c9f6-bd7c-4da2-9d11a2268a6d@suse.de> (raw)
In-Reply-To: <64e961f1-f4c4-655a-82af-60d75ab35f7a@acm.org>
On 11/23/21 8:18 PM, Bart Van Assche wrote:
> On 11/23/21 9:46 AM, Bart Van Assche wrote:
>> On 11/23/21 12:13 AM, Hannes Reinecke wrote:
>>> It's actually a bit more involved.
>>>
>>> The biggest issue is that the SCSI layer is littered with the assumption
>>> that there _will_ be a ->device pointer in struct scsi_cmnd.
>>> If we make up a scsi_cmnd structure _without_ that we'll have to audit
>>> the entire stack to ensure we're not tripping over a NULL device
>>> pointer.
>>> And to make matters worse, we also need to audit the completion path in
>>> the driver, which typically have the same 'issue'.
>>>
>>> Case in point:
>>>
>>> # git grep -- '->device' drivers/scsi | wc --lines
>>> 2712
>>>
>>> Which was the primary reason for adding a stub device to the SCSI Host;
>>> simply to avoid all the pointless churn and have a valid device for all
>>> commands.
>>>
>>> The only way I can see how to avoid getting dragged down into that
>>> rat-hole is to _not_ returning a scsi_cmnd, but rather something else
>>> entirely; that's the avenue I've exploited with my last patchset which
>>> would just return a tag number.
>>> But as there are drivers which really need a scsi_cmnd I can't se how we
>>> can get away with not having a stub scsi_device for the scsi host.
>>>
>>> And that won't even show up in sysfs if we assign it a LUN number beyond
>>> the addressable range; 'max_id':0 tends to be a safe choice here.
>>
>> There is no risk that the scsi_cmnd.device member will be dereferenced
>> for
>> internal requests allocated by the UFS driver. But I understand from your
>> email that making sure that the scsi_cmnd.device member is not NULL is
>> important for other SCSI LLDs. I will look into the approach of
>> associating
>> a stub SCSI device with internal requests.
>
> (replying to my own email)
>
> Hi Hannes,
>
> Allocating a struct scsi_device for internal requests seems tricky to
> me. The
> most straightforward approach would be to call scsi_alloc_sdev().
> However, that
> function accepts a scsi_target pointer and calls .slave_alloc(). So a
> scsi_target structure would have to be set up before that function is
> called and
> SCSI LLDs would have to be audited to verify that .slave_alloc() works
> fine for
> the H:C:I:L tuple assigned to the fake SCSI device. Additionally, how
> should the
> inquiry data be initialized that is filled in by scsi_add_lun()?
>
> Since I do not use SCSI hardware that needs a scsi_device to be
> associated with
> internal requests, I prefer that this functionality is implemented in a
> future
> patch series. Changing the hba->host->internal_queue occurrences in the UFS
> driver into something like hba->host->internal_sdev->request_queue once
> this
> functionality is implemented should be easy.
>
Well, I still do have the patchset for implementing it.
Will be reposting it.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer
next prev parent reply other threads:[~2021-11-24 6:33 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-19 19:57 [PATCH v2 00/20] UFS patches for kernel v5.17 Bart Van Assche
2021-11-19 19:57 ` [PATCH v2 01/20] block: Add a flag for internal commands Bart Van Assche
2021-11-22 8:46 ` John Garry
2021-11-22 17:38 ` Bart Van Assche
2021-11-19 19:57 ` [PATCH v2 02/20] scsi: core: Unexport scsi_track_queue_full() Bart Van Assche
2021-11-19 19:57 ` [PATCH v2 03/20] scsi: core: Fix scsi_device_max_queue_depth() Bart Van Assche
2021-11-19 19:57 ` [PATCH v2 04/20] scsi: core: Fix a race between scsi_done() and scsi_times_out() Bart Van Assche
2021-11-19 19:57 ` [PATCH v2 05/20] scsi: core: Add support for internal commands Bart Van Assche
2021-11-22 8:58 ` John Garry
2021-11-22 17:46 ` Bart Van Assche
2021-11-22 18:08 ` John Garry
2021-11-22 19:04 ` Bart Van Assche
2021-11-23 8:13 ` Hannes Reinecke
2021-11-23 17:46 ` Bart Van Assche
2021-11-23 19:18 ` Bart Van Assche
2021-11-24 6:33 ` Hannes Reinecke [this message]
2021-11-19 19:57 ` [PATCH v2 06/20] scsi: core: Add support for reserved tags Bart Van Assche
2021-11-22 8:15 ` John Garry
2021-11-22 17:25 ` Bart Van Assche
2021-11-22 18:13 ` John Garry
2021-11-19 19:57 ` [PATCH v2 07/20] scsi: ufs: Rename a function argument Bart Van Assche
2021-11-22 20:25 ` Bean Huo
2021-11-19 19:57 ` [PATCH v2 08/20] scsi: ufs: Remove is_rpmb_wlun() Bart Van Assche
2021-11-19 19:57 ` [PATCH v2 09/20] scsi: ufs: Remove the sdev_rpmb member Bart Van Assche
2021-11-19 19:57 ` [PATCH v2 10/20] scsi: ufs: Remove dead code Bart Van Assche
2021-11-24 11:11 ` Adrian Hunter
2021-11-29 19:12 ` Bart Van Assche
2021-11-19 19:57 ` [PATCH v2 11/20] scsi: ufs: Switch to scsi_(get|put)_internal_cmd() Bart Van Assche
2021-11-23 12:20 ` Bean Huo
2021-11-23 17:54 ` Bart Van Assche
2021-11-23 19:41 ` Bart Van Assche
2021-11-24 18:18 ` Bean Huo
2021-11-24 11:02 ` Adrian Hunter
2021-11-24 11:15 ` Adrian Hunter
2021-11-29 19:32 ` Bart Van Assche
2021-11-30 6:41 ` Adrian Hunter
2021-11-30 17:51 ` Bart Van Assche
2021-11-30 19:15 ` Adrian Hunter
2021-11-30 19:21 ` Bart Van Assche
2021-11-19 19:57 ` [PATCH v2 12/20] scsi: ufs: Rework ufshcd_change_queue_depth() Bart Van Assche
2021-11-19 19:57 ` [PATCH v2 13/20] scsi: ufs: Fix a deadlock in the error handler Bart Van Assche
2021-11-30 8:54 ` Bean Huo
2021-11-30 17:52 ` Bart Van Assche
2021-11-30 19:32 ` Bart Van Assche
2021-12-01 13:44 ` Bean Huo
2021-12-01 18:31 ` Bart Van Assche
2021-11-19 19:57 ` [PATCH v2 14/20] scsi: ufs: Introduce ufshcd_release_scsi_cmd() Bart Van Assche
2021-11-24 12:03 ` Adrian Hunter
2021-11-30 18:00 ` Bart Van Assche
2021-11-30 19:02 ` Adrian Hunter
2021-11-30 19:16 ` Bart Van Assche
2021-11-19 19:57 ` [PATCH v2 15/20] scsi: ufs: Improve SCSI abort handling Bart Van Assche
2021-11-24 12:28 ` Adrian Hunter
2021-11-30 4:13 ` Bart Van Assche
2021-11-19 19:57 ` [PATCH v2 16/20] scsi: ufs: Fix a kernel crash during shutdown Bart Van Assche
2021-11-19 19:57 ` [PATCH v2 17/20] scsi: ufs: Stop using the clock scaling lock in the error handler Bart Van Assche
2021-11-19 19:57 ` [PATCH v2 18/20] scsi: ufs: Optimize the command queueing code Bart Van Assche
2021-11-22 17:46 ` Asutosh Das (asd)
2021-11-22 18:13 ` Bart Van Assche
2021-11-22 23:02 ` Asutosh Das (asd)
2021-11-22 23:48 ` Bart Van Assche
2021-11-23 18:24 ` Asutosh Das (asd)
2021-12-01 18:33 ` Bart Van Assche
2021-11-19 19:57 ` [PATCH v2 19/20] scsi: ufs: Implement polling support Bart Van Assche
2021-11-30 8:43 ` Bean Huo
2021-11-30 8:57 ` Avri Altman
2021-11-30 9:15 ` Bean Huo
2021-11-30 14:26 ` Bart Van Assche
2021-11-30 15:40 ` Bean Huo
2021-11-30 17:34 ` Bart Van Assche
2021-11-30 17:37 ` Bart Van Assche
2021-11-19 19:57 ` [PATCH v2 20/20] scsi: ufs: Fix race conditions related to driver data Bart Van Assche
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