From: Damien Le Moal <Damien.LeMoal@wdc.com>
To: Hannes Reinecke <hare@suse.de>,
Bart Van Assche <bvanassche@acm.org>,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
"Martin K . Petersen" <martin.petersen@oracle.com>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
"usb-storage@lists.one-eyed-alien.net"
<usb-storage@lists.one-eyed-alien.net>,
Alan Stern <stern@rowland.harvard.edu>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Justin Piszcz <jpiszcz@lucidpixels.com>
Subject: Re: [PATCH v2] scsi: Fix scsi_get/set_resid() interface
Date: Tue, 5 Nov 2019 00:11:01 +0000 [thread overview]
Message-ID: <BYAPR04MB581685E630A8EA91902B2F9BE77E0@BYAPR04MB5816.namprd04.prod.outlook.com> (raw)
In-Reply-To: a640ee15-515b-6811-9883-48b49ead9276@suse.de
Bart,
On 2019/10/31 17:39, Hannes Reinecke wrote:
> On 10/30/19 6:01 PM, Bart Van Assche wrote:
>> On 10/30/19 9:21 AM, Damien Le Moal wrote:
>>> If you feel strongly about it, I have absolutely no problem with
>>> dropping the patch. I just would like that it be dropped for the right
>>> reasons...
>>
>> Hi Damien,
>>
>> What I'm wondering about is how the SCSI core should support residual
>> overflow. Should a new member be introduced in struct scsi_request?
>> Should resid_len be changed from unsigned int to int or should we
>> perhaps follow yet another approach?
>>
> Please introduce a new member to hold any overflow value.
> And document where it is needed.
Yes, I also think this is the best approach. The current resid_len
member of struct scsi_request can be kept as is, encoding actual
underflow of a command (less bytes transferred than asked for). The new
field would only be used in the case of "overflow", which are not actual
buffer overflows as Hannes pointed out (otherwise, we would get memory
corruptions, iommu screaming etc). The SG driver can make use of this
field to keep the io header resid as an int, with negative values
indicating overflows and positive values underflows.
Best regards.
--
Damien Le Moal
Western Digital Research
next prev parent reply other threads:[~2019-11-05 0:11 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-30 9:08 [PATCH v2] scsi: Fix scsi_get/set_resid() interface Damien Le Moal
2019-10-30 15:15 ` Bart Van Assche
2019-10-30 16:21 ` Damien Le Moal
2019-10-30 17:01 ` Bart Van Assche
2019-10-31 8:39 ` Hannes Reinecke
2019-11-05 0:11 ` Damien Le Moal [this message]
2019-11-05 5:18 ` Martin K. Petersen
2019-11-05 5:24 ` Damien Le Moal
2019-11-06 4:31 ` Martin K. Petersen
2019-11-08 16:24 ` Bart Van Assche
2019-11-09 2:36 ` Martin K. Petersen
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