Re: [PATCH 1/1] scsi: ufs: core: Fix error handler encryption support

[Bart Van Assche]

On 12/14/25 9:58 PM, Christoph Hellwig wrote:
> On Wed, Dec 10, 2025 at 09:44:52AM -0800, Bart Van Assche wrote:
> > On 12/9/25 10:48 PM, Christoph Hellwig wrote:
> > > As mentioned last round, why are you even calling into the crypto
> > > code here?  Calling that for a request without a crypt context,
> > > which includes all of them that do not transfer any data makes no
> > > sense to start with.
> >
> > ufshcd_prepare_lrbp_crypto() only has one caller. Moving the new test
> > from inside ufshcd_prepare_lrbp_crypto() into its caller should be easy.
>
> I don't think callers vs calle is the important part here.  It is to
> check if any actual data is tranferred instead of special casing EH
> commands.

Hi Christoph,

Do you agree with the following?

(a) There is code in the SCSI error handler that submits SCSI commands
    with a data buffer. Hence, disabling encryption if and only if the
    data buffer length is zero can't fix the reported problem. From
    scsi_eh_prep_cmnd() in drivers/scsi/scsi_error.c:

		scmd->sdb.length = min_t(unsigned, SCSI_SENSE_BUFFERSIZE,
					 sense_bytes);
		sg_init_one(&ses->sense_sgl, scmd->sense_buffer,
			    scmd->sdb.length);
		scmd->sdb.table.sgl = &ses->sense_sgl;

(b) In general in the Linux kernel it is strongly preferred to fix the
    root cause of a bug rather than to implement a workaround. This is
    preferred because it makes kernel code easier to maintain and
    reduces the chance that new bugs are introduced.

(c) Disabling encryption in the UFS driver if a command has been
    submitted by the SCSI error handler is a workaround. Patch [1] fixes
    the root cause of the problem, namely the SCSI error handler not
    setting the encryption fields in struct request correctly. We prefer
    [1] because UFS devices that support one million IOPS are expected
    to arrive soon (early 2026). Hence the importance of keeping the hot
    path in the UFS driver fast.

Thanks,

Bart.

[1] [PATCH v2 1/1] scsi: core: Fix error handler encryption support
 
(https://lore.kernel.org/linux-scsi/20251203073310.2248956-1-powenkao@xxxxxxxxxx/)