To:     Lee Duncan <lduncan@suse.com>
Cc:     "Martin K. Petersen" <martin.petersen@oracle.com>,
        Lee Duncan <leeman.duncan@gmail.com>,
        Linux regressions mailing list <regressions@lists.linux.dev>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org,
        Martin Wilck <mwilck@suse.com>, Hannes Reinecke <hare@suse.de>,
        Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Subject: Re: [PATCH] scsi: core: Add BLIST_NO_ASK_VPD_SIZE for some VDASD
From:   "Martin K. Petersen" <martin.petersen@oracle.com>
Organization: Oracle Corporation
Message-ID: <yq1edq0jg2h.fsf@ca-mkp.ca.oracle.com>
References: <20220928181350.9948-1-leeman.duncan@gmail.com>
        <88927435-ae58-c24b-e7b7-b675985de433@leemhuis.info>
        <86D685F2-D411-460B-A09B-6BE942372F0A@gmail.com>
        <yq1zg8pl1nq.fsf@ca-mkp.ca.oracle.com>
        <f8c5619f-1e1a-f759-6ab6-ea84bba3d635@suse.com>
Date:   Tue, 07 Mar 2023 18:40:48 -0500
In-Reply-To: <f8c5619f-1e1a-f759-6ab6-ea84bba3d635@suse.com> (Lee Duncan's
        message of "Tue, 7 Mar 2023 08:33:26 -0800")
Content-Type: text/plain
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?P0H+k0iLlzNQ+WaFUz+V9FiuSCTIFeYcdp/C4gCDf+8LSGNBn2jecZ4GEDKo?=
 =?us-ascii?Q?7i47sXWTuDa1cBriGlHx2btB6jwWHbF2IzWwYZUBN526HTxGHahm8MaXN7TQ?=
 =?us-ascii?Q?z83FWTEHH/lluAI63acV1ge4IRG/hOrKYFhr72bMeZ8uk5IUq6yq87I0Gkql?=
 =?us-ascii?Q?Fyl83yxUaEpt+FzVGWPtV9ornsIjSi/v+1iKTGc/VCp+bQfgvJLKU/qTAIJW?=
 =?us-ascii?Q?HY6ONCOpfEterZ6v7/PJF6Vvuj6AehHxMMyc70uYXbC3VMTTP9LKK61u9Bhk?=
 =?us-ascii?Q?2d1eU4BiV4m+VrYo9cwgs4r3pUYKNj5hiqRgmkNwQ3NT3+Pha/lhZsE1eK33?=
 =?us-ascii?Q?LWFF+HbN0N016vkSOjtdGOWLfCsLIwPsO5+PxAZPRwjDnftIeYv+2lioSRCi?=
 =?us-ascii?Q?w8AQpPlYCNNngLAt7ZRULtWnJZBkJuRuQ1YfbQXRJ3ItxcpG8HpBsxPn5ALS?=
 =?us-ascii?Q?1x6brnBi9U4KytRwgVcd7bgkouYisy90sayttq49BxQqWuQAzHRIETLZosSI?=
 =?us-ascii?Q?fzOnOTXVEYGyDVNSu6ABWXr8RIUB3oM4yS4LpbmxA4AfEHE+KWqYEzH4T/d3?=
 =?us-ascii?Q?4liToqBDSMqP//eB91S67EVoK8BpkQt/Jk1g871mkXuZ52n7A6/LCnQXAfeI?=
 =?us-ascii?Q?R+Dy1BkJiItZuouDrG8qvaxJZ2XSrKrimqaUa9PhaLo0m/S5ho0ekzqxPjnv?=
 =?us-ascii?Q?oK+Frdd8adKE5IxvSRoQkFe0uDy21v/FYvV1JAtBl0QQog674RXy3cCfNV6v?=
 =?us-ascii?Q?DjyxtgUy6FF4cREpRDotSgXtlUV67C40KKOnvNvojrxozJSzHdPMpBuKxQOZ?=
 =?us-ascii?Q?L/6uaVJ23DYzru3jXibLVgq+cruj+JzpUGwIc7jNVvmgsP4hb+4b40F06bM7?=
 =?us-ascii?Q?egSqE8eTSQthD+Nrg1DP2WkH+XlpV8sCsuwAEvSXbEpqLi8sSp6C9mtUq2aP?=
 =?us-ascii?Q?IN+lIKe6ctayljs5eAgZQ8AXjYy5SnPtdnUmQ6UEFGLQsg7d/52ZLyTEpuMU?=
 =?us-ascii?Q?T9Tfa/Qc6z6EjJfctGoPkVRu3Ag3iW/vbfA1nFggQzQgaP4YW+RtwklnmRj6?=
 =?us-ascii?Q?ROBoY8A62X4PviFMl2PVFeFwvsNG8jxU6qFZIf/Q5ADEyj/93EXaZvW2BteL?=
 =?us-ascii?Q?NVSRczRKrg0e3ZmHD0B2xBFKFM2tgr0GUHy9HzNoM178D5EV1nlwWZA2HjCr?=
 =?us-ascii?Q?0qU+DWvfwWLMVYRUKBsM8T52NXZhqsgw0WA51iS0YvUs9Gi98bNVUbfTGXTW?=
 =?us-ascii?Q?VjxQty/polwQdXpmKm0WS3OA+PiEOdH79PtCEA30hm+4ws5MisKW7XLj7rZD?=
 =?us-ascii?Q?x8H0+ZNUy7CTWt4onc8+h0tBZ3sxIKRnxjfP8TsA3JNCIhj67c2YB443XcXm?=
 =?us-ascii?Q?SYW9OgB2oy1xENBOyckCWf9uuD2ChCYiom2dFWxYu9lFjS5+BdXQ0kIPdeWX?=
 =?us-ascii?Q?H1xghXnR6BklLDdct321yRJn9X1urcAHgCDGCsNWf5t38XMqH9Y8rkXrg8B7?=
 =?us-ascii?Q?YIgIxjQrom8N6lTMReIbeO3BZEfYJyfuKK6lUUm3LoOOXv4D5ucONczD9dri?=
 =?us-ascii?Q?XeD7s0lkIhXcFGKSl19ejWQEfaEvgtptid+H3qoI1LmMJTNpIshLD14uIeEs?=
 =?us-ascii?Q?/Q=3D=3D?=
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: =?us-ascii?Q?Li1exKrXQsIvElTmyn4QrPvpvxLBJ3jZS4eEcYjRh03RZCb4e9bcF0b9MRtx?=
 =?us-ascii?Q?jxQC5Wt1+KuXqbAuxFopSZurAJRirD2yN99N3TsQK/iE9K6oBb7sA5f36bZF?=
 =?us-ascii?Q?glTrUcCrhHDLtK18ESQO7iuYVKfm8vLtPo9UGqXrOG/tPqfCthrN3BqmTOvl?=
 =?us-ascii?Q?voiEjQ7U5AtTdXuO3cD0YMEkDomEsHqotv91DPdYq/WTHQ8JR+jBsyV8IHxA?=
 =?us-ascii?Q?DuZOFzl11A4fTwL7fMyK/JGbpG8FSUz+efNHyNlLUaqtPzSUDjl3fwchTJ8D?=
 =?us-ascii?Q?Ytf9O03BNV5OGI4HiLWwU/i6NXUJAR56oRJBX5kNLf5LChPet218rT/s4+/x?=
 =?us-ascii?Q?cu4W40c1qiXU2Aoo4Yi6CgBi+FlujID2eDV+BkxwQcak9lrOIVkOFqQ3Yc+q?=
 =?us-ascii?Q?enAKj0QIyq+8cRVV+yJRdDfFHK/ksNiAnfvb8cdJv4C4xqYT+6Qvd7WA8wJj?=
 =?us-ascii?Q?Yz9uiECDntesXD5oUN5M1fCBCiG/tZP6rPEw2+yEgoL+Pnp6pYHkKfjif4mw?=
 =?us-ascii?Q?k6q7eqir+Ro6aQLKqYRLXF7LLzf/ZzA2lU2zE+QQ3ydjVMQKxu3JwJQ5kodo?=
 =?us-ascii?Q?FKuq8qZiaVBf0cDLzPPA4EepbkyRrvr80J5uJzomqFYZKJkz6Ia9JKcdK+QG?=
 =?us-ascii?Q?C8g4fZ80HPvRMC0Org1iDg3v8gDbRbtz0Mkm/01UdjeHNvBG15ZYtGKHtiVG?=
 =?us-ascii?Q?Cv3i4KUGxWYHWuhQfkfNZFswc4oc+jef36g16cRI1JvYU3blbxff+QXcQj/C?=
 =?us-ascii?Q?2u1gnUnKNrFq2Mo9NHgMiLUNwkWmJfMf5tiSmtOAg6NBI23T+A8P6n6Y9YGU?=
 =?us-ascii?Q?LNVV915bJxVo6Hkr/waR9+kg5Uh5JQfoj23pSZJfszKlsqmmyZo+b0/KfYwF?=
 =?us-ascii?Q?rqBCaEx+98/VMr6ouC4tYv31wbmhNgztThdFXC1YqnGB8zYvpNCPEYvdmWcy?=
 =?us-ascii?Q?xCBXedslzKqNPsYRLwoMRg=3D=3D?=
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 0c13fb1f-5775-40ce-7587-08db1f656253
X-MS-Exchange-CrossTenant-AuthSource: PH0PR10MB4759.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Mar 2023 23:40:50.6570
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: zpr1y0uJyEVoXCuC2j7mqsC6XlFSdlJv5cL6yXQ/InPAAz7PF7RkekRkeNNminShm0g/UsLtPer9pttok7TYYZR0ULuZ+AsL4daYFPSmz1M=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: CYYPR10MB7566
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.219,Aquarius:18.0.942,Hydra:6.0.573,FMLib:17.11.170.22
 definitions=2023-03-07_16,2023-03-07_01,2023-02-09_01
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=875 bulkscore=0
 malwarescore=0 spamscore=0 mlxscore=0 suspectscore=0 adultscore=0
 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1
 engine=8.12.0-2212070000 definitions=main-2303070208
X-Proofpoint-GUID: z45Hshh_dqBTKdx4Qr_T1trx_QmjoROn
X-Proofpoint-ORIG-GUID: z45Hshh_dqBTKdx4Qr_T1trx_QmjoROn
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


Lee,

> My worry is that this won't always work. Looking at the code, the
> buffer sizes used for VPD pages include 8, 32, 64, and 252 bytes. I'm
> not sure how reading 255 bytes into an 8-byte buffer would work.

In the scsi_get_vpd_buf() case we will allocate a 255 byte buffer since
that's what scsi_get_vpd_size() returns for a VDASD.

And in the scsi_get_vpd_page() case, where a buffer already exists, we
clamp the INQUIRY size to the minimum of scsi_get_vpd_size() and the
buffer length provided by the caller.

-- 
Martin K. Petersen	Oracle Linux Engineering