linux-kernel - Re: [PATCH v2 1/1] scsi: core: Fix error handler encryption support

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Message-ID: <e792b704-6f06-47a9-82b1-af0e4a0da4d9@suse.com>
Date: Thu, 4 Dec 2025 08:55:16 +0100
From: Hannes Reinecke <hare@...e.com>
To: Bart Van Assche <bvanassche@....org>,
 Christoph Hellwig <hch@...radead.org>, Po-Wen Kao <powenkao@...gle.com>
Cc: "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
 "Martin K. Petersen" <martin.petersen@...cle.com>,
 "open list:SCSI SUBSYSTEM" <linux-scsi@...r.kernel.org>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/1] scsi: core: Fix error handler encryption support

On 12/3/25 16:55, Bart Van Assche wrote:
> On 12/2/25 10:42 PM, Hannes Reinecke wrote:
>> There had been an intersection with the reserved command stuff, but
>> now that Bart has dusted things off there I guess I should give it
>> another go.
> 
> Does that patch series perhaps involve allocating a reserved command
> from inside the SCSI error handler? Won't that break SCSI LLDs that
> restrict the queue depth to one? I think that the following SCSI LLDs
> only support one command (.can_queue = 1):

reserved commands are only implemented for adapters which require an
LLD specific 'tag' to send TMFs (eg fnic, aacraid, or hpsa).
Most HBAs (especially the older ones) are not that elaborate, and
there TMFs are not commands per se but rather operations on the HBA.

EG fdomain host_reset is just settings some bits in some registers,
no command allocation needed at all.

So for those we don't need to allocate _any_ commands for TMFs,
consequently we don't need to implement reserved commands and
hence TMFs are not guarded by .can_queue at all.

> * drivers/scsi/fdomain.c
> * drivers/scsi/mac53c94.c
> * drivers/scsi/ppa.c
> * drivers/scsi/imm.c
> * drivers/scsi/aha152x.c
> 
Cheers,
Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@...e.com                               +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich