Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Sat, 1 Apr 2023 16:03:35 +0800
From:   Chen Yu <yu.c.chen@intel.com>
To:     "Rafael J. Wysocki" <rafael@kernel.org>,
        Len Brown <len.brown@intel.com>
CC:     Ye Bin <yebin10@huawei.com>, <linux-pm@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, Yifan Li <yifan2.li@intel.com>
Subject: Re: [PATCH] PM: hibernate: Do not get block device exclusively in
 test_resume mode
Message-ID: <ZCflV98lGOSIeF88@chenyu5-mobl1>
References: <20230401154832.320999-1-yu.c.chen@intel.com>
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <20230401154832.320999-1-yu.c.chen@intel.com>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?gtKN+qqaLEGTEkIVUQScLHJAm1HvNLRtAEBJ+9aWaip40W6aGrLpHwJYWth3?=
 =?us-ascii?Q?cepbJUhv+GroNJ1FA1/8RIURPcQ335jRx5sQoo7Z72Gtniizw7XEUtEGSZGv?=
 =?us-ascii?Q?cSd9+CigqheBhh0zxOAUtY2TbicJKsghqpVQw4rVXKWUlMKxcFxflGghShwh?=
 =?us-ascii?Q?RBWU6K6m/ubWT4Kocx96Zbtjy2lbWnzRfaL2+Z5Sb1A7cENVH4+rjXuKui8r?=
 =?us-ascii?Q?xAj43G6Y79e1ipAL8ciWtbcMXdlmYRY1OgaWG6RAZRZIcMNQIHX5fN7j3l7x?=
 =?us-ascii?Q?YSW5YsgZuweSix3S9ULSwXH+D/fD0JlY9t3j3zCD5d+OOxFsLEKSvmsU6bCE?=
 =?us-ascii?Q?1Oc5GTYd5Pj2AS9Fu5T7+5p1gZAiCWs3dpIM+E/E9dNKpHIdrJE4dI8n4fMw?=
 =?us-ascii?Q?8j0pvcOhFaoSQlMK7XJ9/nyy9zojhQp09LbEmrFHM1OOw+U2RL3Ei6FmAide?=
 =?us-ascii?Q?Qco7vPNMhmHUTaHvs5MXG7URLDMKwQgYs5TzCsryGBCsq4zB+g6IED+SdLcd?=
 =?us-ascii?Q?Jc9cKiqjagqMpUQkuAKpAIzqxHCTHVgw1esHNiyCX+2tmLA4BiQhk3kV5452?=
 =?us-ascii?Q?iNRDJtx3lDOUSuP+UOOkPGniCOztD+b1LXb05Nhv8WpKddXIyo/hAG1zbNub?=
 =?us-ascii?Q?tVceGRoe5Ee8BkNiEtNOCCxsMpuBuWPoJkV+x+O6PFjvFRwitG5wlsKYHdZY?=
 =?us-ascii?Q?UrRIExEeBemD1uJuf5EL03sq+4nBSa6zQckpusTnjsr3Rd4ErVWoBcYPErDP?=
 =?us-ascii?Q?4vx+3kUXvQovbqw7VdXUzYPmoPi0K2TjYDFNxcMSkbDYZvaLYkxR+Zq77w4V?=
 =?us-ascii?Q?HnDLbygYrpiRSjjhPwEkWe8Y1JqHeumACzURXCH43O4CsG2tEgZLqFDwWrQO?=
 =?us-ascii?Q?+PYAjZgFeg+lV4157ffLCMeuXV2SFuu9W4IA0QF70j9cUlzRgfic7f8A8glG?=
 =?us-ascii?Q?Jxndd+oyUidrBDRQ5v+qYTn4C5bmDCeQ7rXNH2sawZAko/8TewikYkEQ/O8i?=
 =?us-ascii?Q?toLN9pULIgswx/yw91z+j2QG35V7TsKyF+Tpf3fNzsAaLTr/QNm1jWi2Ww9P?=
 =?us-ascii?Q?t6dWvpbL/vtCf1p7T82J4CW1X3X64loVCkriSn7VGIAcDDwaKFFMfXDUUPW9?=
 =?us-ascii?Q?prICDH5y/AWJfxN9n5PnEUD8vTbBvmoSon/c8NU6zOV3oxBFcChYsP3buRqB?=
 =?us-ascii?Q?qZfYrFWKc8cyG9i2j6r5vTS6gCchu2ANhe/mbzIOSRrZ32r9ZPp41lcHNnoy?=
 =?us-ascii?Q?OQqAQmpT6bfLLY263w55/BZA345VHhB9hr6p+kIpB+CUHdyYzROT/ck/yIDQ?=
 =?us-ascii?Q?9vLHvg0bMriUbXD21KeIAFqXT/unF8wMmajCVQM+ACwv4AH0U/RF2ElRDswS?=
 =?us-ascii?Q?O4V7EYs1C8sKr+jR9V3Cihf0K8nZ91sbXF1aFAc4Ct2soWz0mowFK9cgE0qp?=
 =?us-ascii?Q?g7q3dUIzDiJ35vnPItdddbUXjmRsZ174O951udZOcid7hAcPrIu1J9xxKoC5?=
 =?us-ascii?Q?A8IqnyjPxkZmaUTbADflQVxz0DDa43NKNgQErLMTaSif9fOHdMAIwxk58yI8?=
 =?us-ascii?Q?wJRMoVybURE2kCaZplYzJcmtEoZMBfdHOCn4BlTb?=
X-MS-Exchange-CrossTenant-Network-Message-Id: 70d4b4ab-de64-4923-d91e-08db32879f0c
X-MS-Exchange-CrossTenant-AuthSource: MN0PR11MB6206.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 Apr 2023 08:03:47.5667
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: KD9k/0ficgpkQKvCdQY85LW3T4g6IML/A8VARAf34Dmu2aIedOXQmMG78fGPdmLl5ElldtSMG8B8ZO0m0SaMvw==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR11MB4774
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-2.5 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,
        RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE
        autolearn=unavailable autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 2023-04-01 at 23:48:32 +0800, Chen Yu wrote:
> The system refused to do a test_resume because it found that the
> swap device has already been taken by someone else. Specificly,
> the swsusp_check()->blkdev_get_by_dev(FMODE_EXCL) is supposed to
> do this check.
> 
> Steps to reproduce:
>  dd if=/dev/zero of=/swapfile bs=$(cat /proc/meminfo |
>     awk '/MemTotal/ {print $2}') count=1024 conv=notrunc
>  mkswap /swapfile
>  swapon /swapfile
>  swap-offset /swapfile
>  echo 34816 > /sys/power/resume_offset
>  echo test_resume > /sys/power/disk
>  echo disk > /sys/power/state
> 
>  PM: Using 3 thread(s) for compression
>  PM: Compressing and saving image data (293150 pages)...
>  PM: Image saving progress:   0%
>  PM: Image saving progress:  10%
>  ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
>  ata1.00: configured for UDMA/100
>  ata2: SATA link down (SStatus 0 SControl 300)
>  ata5: SATA link down (SStatus 0 SControl 300)
>  ata6: SATA link down (SStatus 0 SControl 300)
>  ata3: SATA link down (SStatus 0 SControl 300)
>  ata4: SATA link down (SStatus 0 SControl 300)
>  PM: Image saving progress:  20%
>  PM: Image saving progress:  30%
>  PM: Image saving progress:  40%
>  PM: Image saving progress:  50%
>  pcieport 0000:00:02.5: pciehp: Slot(0-5): No device found
>  PM: Image saving progress:  60%
>  PM: Image saving progress:  70%
>  PM: Image saving progress:  80%
>  PM: Image saving progress:  90%
>  PM: Image saving done
>  PM: hibernation: Wrote 1172600 kbytes in 2.70 seconds (434.29 MB/s)
>  PM: S|
>  PM: hibernation: Basic memory bitmaps freed
>  PM: Image not found (code -16)
> 
> This is because when using the swapfile as the hibernation storage,
> the block device where the swapfile is located has already been mounted
> by the OS distribution(usually been mounted as the rootfs). This is not
> an issue for normal hibernation, because software_resume()->swsusp_check()
> happens before the block device(rootfs) mount. But it is a problem for the
> test_resume mode. Because when test_resume happens, the block device has
> been mounted already.
> 
> Thus remove the FMODE_EXCL for test_resume mode. This would not be a
> problem because in test_resume stage, the processes have already been
> frozen, and the race condition described in
> Commit 39fbef4b0f77 ("PM: hibernate: Get block device exclusively in swsusp_check()")
> is unlikely to happen.
> 
> Fixes: 39fbef4b0f77 ("PM: hibernate: Get block device exclusively in swsusp_check()")
> Reported-by: Yifan Li <yifan2.li@intel.com>
> Signed-off-by: Chen Yu <yu.c.chen@intel.com>
>
Please ignore this patch, will send a refined version later. Sorry for the noise.

thanks,
Chenyu