Message-ID: <2fea4b28-e441-6c77-5bb6-97428c19179f@oracle.com>
Date:   Mon, 13 Feb 2023 10:22:37 -0600
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.7.2
Subject: Re: [PATCH] scsi: target: iscsi: set memalloc_noio with loopback
 network connections
To:     Maurizio Lombardi <mlombard@redhat.com>,
        David Jeffery <djeffery@redhat.com>
Cc:     target-devel@vger.kernel.org,
        "Martin K . Petersen" <martin.petersen@oracle.com>,
        Laurence Oberman <loberman@redhat.com>,
        linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20230208200957.14073-1-djeffery@redhat.com>
 <CAFL455kEoLQF+vc2MGmtLdrQ-=U+HJzqgknZmM54iCPJD1p_mA@mail.gmail.com>
Content-Language: en-US
From:   Mike Christie <michael.christie@oracle.com>
In-Reply-To: <CAFL455kEoLQF+vc2MGmtLdrQ-=U+HJzqgknZmM54iCPJD1p_mA@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?emZTaGc2MU9TOXJaUmpyL0Z3NENDc3RRbDJ5MFhmcVp0QlAwNm1GbHltWTZQ?=
 =?utf-8?B?UkFkL1NMbkpJd0p3dVgwajYvajBydldWUjYwVHkzV2VxbUlMSDVWMlhiSmJw?=
 =?utf-8?B?L29Ga245VWNyTEgyQ2lMSGY1dEpFRElkNU0yVVBmOWw4L3NqdHhYNERYMlJC?=
 =?utf-8?B?aGp4MEtqeVhSaW5vamkrSVRkVnFiRTdIUk1xLy82d3d4U1Q5QzJ5azc1Yzhl?=
 =?utf-8?B?WTZkRzFTQUVMN0k5MHF2YXl5d1I5OE5KT1U2N3FLTlJhVHpzK2t4OHdiTmho?=
 =?utf-8?B?OENrUmYzbS90QWlkZzNieXdMOE1oRC84eSszVE9sVnJaU0oxb3ZTUy8waWpw?=
 =?utf-8?B?Lys3bEh0Y283NjVGbkdNRHdPT3Y0Wk1QZ1JYRGFvNHEzOWE4TGIybW9jZkZL?=
 =?utf-8?B?UEdmdXYyZTJvRDJpVmtKb1JxNnZuL2J2cE5obzAwRTNwR2hzR0ltT1ZIQlph?=
 =?utf-8?B?VzJFUmdHSUFlVm9sN01tS1lIYWNWc3VoSTdrOTBwdlB5dzhOODZFbUxkWDNo?=
 =?utf-8?B?WEE0allRc3Z5MkV3QW5TbjQwanQwRnl5NlpaaVlZVGtZeW1BdnZCd2xnMGxF?=
 =?utf-8?B?TUZIVWRmUTFsL1hOdVFaZnNRRkUyOFdBUnFYcmhkdnluSWIwMjJiY3JGUWpO?=
 =?utf-8?B?WXVuMUVWV09BYkNvVXp3K0cxVG9UMXdXcEtERzVqMiswUnQ5UlRLWDI3YlBu?=
 =?utf-8?B?bEFtLy9PN3lncWYwaDY1c2JWMnk1RnBMbnhXb3JHNEVJMXdWeWsvT2FUUUl0?=
 =?utf-8?B?YmZLa3RLTGxDZFVhY3dxbzVuWllwcnpiUEVScnVnNG5KM1RocTd0MlB6QXVE?=
 =?utf-8?B?Y1h3bW5yTVNNMk4ydEFGcitGSFJ2K3k1ZzYybE14aDl1L0NtemQ5MHViMEF3?=
 =?utf-8?B?ZXVoMGtOcERvR3NZUGgzY2w0UWdqYUF4N3R1Q1NETlRWVnRUSUVNdmVrRmMr?=
 =?utf-8?B?WVhJWXlMWWw0eldPYW9SbTdaeDhHYXdacmloOXZxdnpGY3F0OGdaU3dHSnFw?=
 =?utf-8?B?dFFRN3RleHJlRFdxY2ZLMzZZelpkRG93UzIrbFduQjlacWxEQ0lNVUpXRXlH?=
 =?utf-8?B?VmtxajJjMDRHSyswZDJuRFV1Y3pBUmdjdUE4UVY3SE55U0NhY3FhYWFYbmpI?=
 =?utf-8?B?Ly94c2tRcGxBclVIVklNQzhMQ3pVWkRYSTlIU0labFlzdEhKcW1qTmpiMThw?=
 =?utf-8?B?b0JoS0VkejEyMURmK3I4OXJ2ZUdzQmpQS0hOQWw1Uk1TZS93TVl1UmN0bW5h?=
 =?utf-8?B?UVExbS9Yb0JYNm9rRVFoSXdLRHhOWEhlQnF6WGZjZDhEWXIxTDZCeUlyS3Y1?=
 =?utf-8?B?OG9FekFxT0c1czc4RWZWTlIzMk5vOE1aZ1RxYTBMWVFhYUp1MHR6clBuSG1v?=
 =?utf-8?B?eThZWkw1VU9scEtaTCtDS3B3RjBRYVdWQzJYbkptWlVhTWRJUEU1azdIT1pD?=
 =?utf-8?B?RVdBQzBsODN3eklBQ1BnUVJpc2UvU1NzVC9rTEsyYkRPbTNncWs4bWNjampQ?=
 =?utf-8?B?c0trY1JiU0VJNkJqTXllMzB6RjA2ZG1tUS8zL3dCdEZabnozZlhDQk5zc1Ar?=
 =?utf-8?B?OUdzL1k5dmo2ZG1IOWU4K2RRSnRNck1MMVlEdldjZWdtMC9nRzBVNHZ0TG8x?=
 =?utf-8?B?eDdKMzNRYkxhVUpUVkRXTVYvakNRSWJwcVUyV2RCcEdrSFRpNFluSlc1d0lB?=
 =?utf-8?B?TE5WcVd1a1RvTFpmM09qNDlhMjhQYityWUxWUTNKMFVWaW44NUpmSFRPVTFs?=
 =?utf-8?B?clFUMUlyTWQ4aHRRRWRRT0hSR3pxNnJXVDZHVWhwS3dxaXZ2dWRLaEVDejNv?=
 =?utf-8?B?cUZnNi9PRDF3K1BuNC8xYU9YN1pkc3IrMHl0TCtQUWZ5R3NETHlqQnluR1pQ?=
 =?utf-8?B?WE0vb1JmRytZbW95b2syMkNPQms2Zzc2Z0pDS2FtbXVSdVVsR0RWL2QvRFN6?=
 =?utf-8?B?S2tsODlsL0ZLSXhoaHdTTWJEMzZSYjNiTUgyU205azZNWXVneE12RVQzQkFK?=
 =?utf-8?B?anhMOCtwMjZVNHFIV0dUUUdWSk9iNHlCSG1PbEh4Ni9KV3ZLOHdnSEhZWVYz?=
 =?utf-8?B?anladW9hb08yTGRQNjN0SGR5T2JYcXVZM2pYb3cyZU93NjVRcHIyMm5IeWpT?=
 =?utf-8?B?M2cwZ3RlL1FTZklZL1VlajNuT1l6a244NjVFczY2U2hseFBlaGJ2QkxTRHZw?=
 =?utf-8?B?aVE9PQ==?=
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: 4qnaBjMzIEY5sPfE2jroZqnMkFx/3NyfNkJEYXci4OSmjt5ci4Yi2mYo2bzrILpGxvtxKgDHHPjE8RKVBQ8q130vK/oX7n0JRfZElW/s1XQp60Loi2xiCcVYx2yz4GhUoyeLvR8p6W/OkOx9PFHI7uilAzZ4M3XWGAtVRxQpaCeiTq2/CU6QzRTcghG5aYo9YsrTuitJju3y+L9BdFvqWTj6FgJZlho0lc0bQe+JxTNsWucqAiXeb/szBo9EBy/4gwKXArVmOJu3N0JGflueTWb3fR6rgTa5VKdDzRACG75Wys/kE/TLppMtw0uGp0VIU+92rMcdo0cCsn5Y4xtXGf5UChCPVqlRdecq51jw2KQFWXq1o/nZ01Dj8BIArkp8rLh+OflV4xQrocMo3Y3gON1ccHa0raFWEhki/zRZm7AuO3goeK25IjwalXZ+8sbURnV2nXvxaWQqEx7IWuQI4/i4AMJX78soCZFsQUPZi8nj9iX0hLrgNt38yuV4ENZbQ1RGjkkuemgEbMQXaMEm7VAKiLeajCRb9lP9Q3JK41xZwKSfrDN4DzM93zlMN0Ex/sBDEdcpy8nNu0wrJb8mV6tyqPHTdqCltof6zAcS8Fzv/2A5B62AlkWJDuJCw7P392x6So3yGMfOFQoygcLXw30zRUDG2iOzypN3x8bX3v1sbcUAfRNxbYvn2i4jcHz+uZGghsVHD4vWfigj6M80lDZvA/dG2p6VsG0SUtv4FTiHgJtZbo9BarGfwjNn3aJXHDkqpQFBAw/Umfg9qrbxcL+7sz1dF43M8wsL1eMU8Ik=
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: a44d79cb-0337-452e-3009-08db0dde8610
X-MS-Exchange-CrossTenant-AuthSource: DM5PR10MB1466.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Feb 2023 16:22:38.8040
 (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: vUolyhuxv1VchSkuhamsSakpLOPKAdiBEHeav+GBNopTw/BYe5ptGDc8Sur9crYHOHOq42KOX43SeUXEEHvzDA5rFWNfrscMbaNk41o7WTA=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR10MB7400
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.219,Aquarius:18.0.930,Hydra:6.0.562,FMLib:17.11.170.22
 definitions=2023-02-13_11,2023-02-13_01,2023-02-09_01
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 phishscore=0
 suspectscore=0 mlxscore=0 spamscore=0 mlxlogscore=999 adultscore=0
 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1
 engine=8.12.0-2212070000 definitions=main-2302130148
X-Proofpoint-ORIG-GUID: 7BZDSNG9MPvZyd1rEYFEDprrZgrGxeMA
X-Proofpoint-GUID: 7BZDSNG9MPvZyd1rEYFEDprrZgrGxeMA
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 2/13/23 5:59 AM, Maurizio Lombardi wrote:
> st 8. 2. 2023 v 21:10 odesílatel David Jeffery <djeffery@redhat.com> napsal:
>>
>>
>> +       /*
>> +        * If the iscsi connection is over a loopback device from using
>> +        * iscsi and iscsit on the same system, we need to set memalloc_noio to
>> +        * prevent memory allocation deadlocks between target and initiator.
>> +        */
>> +       rcu_read_lock();
>> +       dst = rcu_dereference(conn->sock->sk->sk_dst_cache);
>> +       if (dst && dst->dev && dst->dev->flags & IFF_LOOPBACK)
>> +               loopback = true;
>> +       rcu_read_unlock();
> 
> Hi Mike,
> I tested it, it works. The customer also confirmed that it fixes the
> deadlock on his setup.

You never responded about why/how it's used in production. Is it some sort
of clustering or container or what?

The login related code can still swing back on you if it's run for a relogin.
It would happen if we overqueue and a nop timesout because the iscsi recv thread
is waiting for backend resources like a request/queue slot, or if management tools
disable/enable the tpgt for reconfigs, etc.