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([2601:647:4000:d7:30fe:750:6059:a44d]) by smtp.gmail.com with ESMTPSA id u2sm3299740pjn.20.2020.04.23.16.25.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 Apr 2020 16:25:14 -0700 (PDT) Subject: Re: [PATCH] scsi: storvsc: Fix a panic in the hibernation procedure To: Dexuan Cui , "jejb@linux.ibm.com" , "martin.petersen@oracle.com" , "linux-scsi@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "hch@lst.de" , "hare@suse.de" , Michael Kelley , Long Li , "ming.lei@redhat.com" , Balsundar P Cc: "linux-hyperv@vger.kernel.org" , "wei.liu@kernel.org" , Stephen Hemminger , Haiyang Zhang , KY Srinivasan References: <1587514644-47058-1-git-send-email-decui@microsoft.com> <1b6de3b0-4e0c-4b46-df1a-db531bd2c888@acm.org> From: Bart Van Assche Autocrypt: addr=bvanassche@acm.org; prefer-encrypt=mutual; keydata= mQENBFSOu4oBCADcRWxVUvkkvRmmwTwIjIJvZOu6wNm+dz5AF4z0FHW2KNZL3oheO3P8UZWr LQOrCfRcK8e/sIs2Y2D3Lg/SL7qqbMehGEYcJptu6mKkywBfoYbtBkVoJ/jQsi2H0vBiiCOy fmxMHIPcYxaJdXxrOG2UO4B60Y/BzE6OrPDT44w4cZA9DH5xialliWU447Bts8TJNa3lZKS1 AvW1ZklbvJfAJJAwzDih35LxU2fcWbmhPa7EO2DCv/LM1B10GBB/oQB5kvlq4aA2PSIWkqz4 3SI5kCPSsygD6wKnbRsvNn2mIACva6VHdm62A7xel5dJRfpQjXj2snd1F/YNoNc66UUTABEB AAG0JEJhcnQgVmFuIEFzc2NoZSA8YnZhbmFzc2NoZUBhY20ub3JnPokBOQQTAQIAIwUCVI67 igIbAwcLCQgHAwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJEHFcPTXFzhAJ8QkH/1AdXblKL65M Y1Zk1bYKnkAb4a98LxCPm/pJBilvci6boefwlBDZ2NZuuYWYgyrehMB5H+q+Kq4P0IBbTqTa jTPAANn62A6jwJ0FnCn6YaM9TZQjM1F7LoDX3v+oAkaoXuq0dQ4hnxQNu792bi6QyVdZUvKc macVFVgfK9n04mL7RzjO3f+X4midKt/s+G+IPr4DGlrq+WH27eDbpUR3aYRk8EgbgGKvQFdD CEBFJi+5ZKOArmJVBSk21RHDpqyz6Vit3rjep7c1SN8s7NhVi9cjkKmMDM7KYhXkWc10lKx2 RTkFI30rkDm4U+JpdAd2+tP3tjGf9AyGGinpzE2XY1K5AQ0EVI67igEIAKiSyd0nECrgz+H5 PcFDGYQpGDMTl8MOPCKw/F3diXPuj2eql4xSbAdbUCJzk2ETif5s3twT2ER8cUTEVOaCEUY3 eOiaFgQ+nGLx4BXqqGewikPJCe+UBjFnH1m2/IFn4T9jPZkV8xlkKmDUqMK5EV9n3eQLkn5g lco+FepTtmbkSCCjd91EfThVbNYpVQ5ZjdBCXN66CKyJDMJ85HVr5rmXG/nqriTh6cv1l1Js T7AFvvPjUPknS6d+BETMhTkbGzoyS+sywEsQAgA+BMCxBH4LvUmHYhpS+W6CiZ3ZMxjO8Hgc ++w1mLeRUvda3i4/U8wDT3SWuHcB3DWlcppECLkAEQEAAYkBHwQYAQIACQUCVI67igIbDAAK CRBxXD01xc4QCZ4dB/0QrnEasxjM0PGeXK5hcZMT9Eo998alUfn5XU0RQDYdwp6/kMEXMdmT oH0F0xB3SQ8WVSXA9rrc4EBvZruWQ+5/zjVrhhfUAx12CzL4oQ9Ro2k45daYaonKTANYG22y //x8dLe2Fv1By4SKGhmzwH87uXxbTJAUxiWIi1np0z3/RDnoVyfmfbbL1DY7zf2hYXLLzsJR mSsED/1nlJ9Oq5fALdNEPgDyPUerqHxcmIub+pF0AzJoYHK5punqpqfGmqPbjxrJLPJfHVKy goMj5DlBMoYqEgpbwdUYkH6QdizJJCur4icy8GUNbisFYABeoJ91pnD4IGei3MTdvINSZI5e Message-ID: Date: Thu, 23 Apr 2020 16:25:11 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On 2020-04-23 11:29, Dexuan Cui wrote: > So it looks the below patch also works for me: > > --- a/kernel/power/hibernate.c > +++ b/kernel/power/hibernate.c > @@ -898,6 +898,11 @@ static int software_resume(void) > error = freeze_processes(); > if (error) > goto Close_Finish; > + > + error = freeze_kernel_threads(); > + if (error) > + goto Close_Finish; > + > error = load_image_and_restore(); > thaw_processes(); > Finish: > > Just to be sure, I'll do more tests, but I believe the panic can be fixed > by this according to my tests I have done so far. If a freeze_kernel_threads() call is added in software_resume(), should a thaw_kernel_threads() call be added too? Anyway, please Cc me if a patch for software_resume() is submitted. > I'm still not sure what the comment before scsi_device_quiesce() means: > * ... Since special requests may also be requeued requests, > * a successful return doesn't guarantee the device will be > * totally quiescent. > > I don't know if there can be some other I/O submitted after > scsi_device_quiesce() returns in the case of hibernation, and I don't > know if aac_suspend() -> scsi_host_block() should be fixed/removed, > but as far as the panic is concerned, I'm very glad I have found a better > fix with your help. The function blk_set_pm_only() increments the q->pm_only counter while the blk_clear_pm_only() function decrements the q->pm_only counter. If q->pm_only > 0, blk_queue_enter() only succeeds if the flag BLK_MQ_REQ_PREEMPT is set in the second argument passed to that function. blk_get_request() calls blk_queue_enter(). The result is that while q->pm_only > 0 blk_get_request() only submits a request without waiting if the BLK_MQ_REQ_PREEMPT flag is set in its second argument. scsi_execute() sets the BLK_MQ_REQ_PREEMPT flag. In other words, scsi_device_quiesce() blocks requests submitted by filesystems but still allows SCSI commands submitted by the SCSI core to be executed. "special" refers to requests with the BLK_MQ_REQ_PREEMPT flag set. Bart.