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[97.64.23.41]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-70b43898de8sm6365451b3a.27.2024.07.11.19.20.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 Jul 2024 19:20:45 -0700 (PDT) Message-ID: Date: Fri, 12 Jul 2024 10:20:40 +0800 Precedence: bulk X-Mailing-List: linux-scsi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 1/3] scsi: core: Add new helper to iterate all devices of host Content-Language: en-US From: Wenchao Hao To: Hannes Reinecke , "James E . J . Bottomley" , "Martin K . Petersen" , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org References: <20240605091731.3111195-1-haowenchao22@gmail.com> <20240605091731.3111195-2-haowenchao22@gmail.com> <3b24ef4a-996b-4a8b-89f3-385872573039@suse.de> <698d4b22-719c-4e57-94ed-f507e425ee12@suse.de> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 2024/6/13 15:10, Wenchao Hao wrote: > On 2024/6/13 14:27, Hannes Reinecke wrote: >> On 6/12/24 17:06, Wenchao Hao wrote: >>> On 6/12/24 4:33 PM, Hannes Reinecke wrote: >>>> On 6/5/24 11:17, Wenchao Hao wrote: >>>>> shost_for_each_device() would skip devices which is in SDEV_CANCEL or >>>>> SDEV_DEL state, for some scenarios, we donot want to skip these devices, >>>>> so add a new macro shost_for_each_device_include_deleted() to handle it. >>>>> >>>>> Following changes are introduced: >>>>> >>>>> 1. Rework scsi_device_get(), add new helper __scsi_device_get() which >>>>>      determine if skip deleted scsi_device by parameter "skip_deleted". >>>>> 2. Add new parameter "skip_deleted" to __scsi_iterate_devices() which >>>>>      is used when calling __scsi_device_get() >>>>> 3. Update shost_for_each_device() to call __scsi_iterate_devices() with >>>>>      "skip_deleted" true >>>>> 4. Add new macro shost_for_each_device_include_deleted() which call >>>>>      __scsi_iterate_devices() with "skip_deleted" false >>>>> >>>>> Signed-off-by: Wenchao Hao >>>>> --- >>>>>    drivers/scsi/scsi.c        | 46 ++++++++++++++++++++++++++------------ >>>>>    include/scsi/scsi_device.h | 25 ++++++++++++++++++--- >>>>>    2 files changed, 54 insertions(+), 17 deletions(-) >>>>> >>>>> diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c >>>>> index 3e0c0381277a..5913de543d93 100644 >>>>> --- a/drivers/scsi/scsi.c >>>>> +++ b/drivers/scsi/scsi.c >>>>> @@ -735,20 +735,18 @@ int scsi_cdl_enable(struct scsi_device *sdev, bool enable) >>>>>        return 0; >>>>>    } >>>>>    -/** >>>>> - * scsi_device_get  -  get an additional reference to a scsi_device >>>>> +/* >>>>> + * __scsi_device_get  -  get an additional reference to a scsi_device >>>>>     * @sdev:    device to get a reference to >>>>> - * >>>>> - * Description: Gets a reference to the scsi_device and increments the use count >>>>> - * of the underlying LLDD module.  You must hold host_lock of the >>>>> - * parent Scsi_Host or already have a reference when calling this. >>>>> - * >>>>> - * This will fail if a device is deleted or cancelled, or when the LLD module >>>>> - * is in the process of being unloaded. >>>>> + * @skip_deleted: when true, would return failed if device is deleted >>>>>     */ >>>>> -int scsi_device_get(struct scsi_device *sdev) >>>>> +static int __scsi_device_get(struct scsi_device *sdev, bool skip_deleted) >>>>>    { >>>>> -    if (sdev->sdev_state == SDEV_DEL || sdev->sdev_state == SDEV_CANCEL) >>>>> +    /* >>>>> +     * if skip_deleted is true and device is in removing, return failed >>>>> +     */ >>>>> +    if (skip_deleted && >>>>> +        (sdev->sdev_state == SDEV_DEL || sdev->sdev_state == SDEV_CANCEL)) >>>>>            goto fail; >>>> >>>> Nack. >>>> SDEV_DEL means the device is about to be deleted, so we _must not_ access it at all. >>>> >>> >>> Sorry I added SDEV_DEL here at hand without understanding what it means. >>> Actually, just include scsi_device which is in SDEV_CANCEL would fix the >>> issues I described. >>> >>> The issues are because device removing concurrent with error handle. >>> Normally, error handle would not be triggered when scsi_device is in >>> SDEV_DEL. Below is my analysis, if it is wrong, please correct me. >>> >>> If there are scsi_cmnd remain unfinished when removing scsi_device, >>> the removing process would waiting for all commands to be finished. >>> If commands error happened and trigger error handle, the removing >>> process would be blocked until error handle finished, because >>> __scsi_remove_device called  del_gendisk() which would wait all >>> requests to be finished. So now scsi_device is in SDEV_CANCEL. >>> >>> If the scsi_device is already in SDEV_DEL, then no scsi_cmnd has been >>> dispatched to this scsi_device, then error handle would never triggered. >>> >>> I want to change the new function __scsi_device_get() as following, >>> please help to review. >>> >>> /* >>>   * __scsi_device_get  -  get an additional reference to a scsi_device >>>   * @sdev:    device to get a reference to >>>   * @skip_canceled: when true, would return failed if device is deleted >>>   */ >>> static int __scsi_device_get(struct scsi_device *sdev, bool skip_canceled) >>> { >>>     /* >>>      * if skip_canceled is true and device is in removing, return failed >>>      */ >>>     if (sdev->sdev_state == SDEV_DEL || >>>         (sdev->sdev_state == SDEV_CANCEL && skip_canceled)) >>>         goto fail; >>>     if (!try_module_get(sdev->host->hostt->module)) >>>         goto fail; >>>     if (!get_device(&sdev->sdev_gendev)) >>>         goto fail_put_module; >>>     return 0; >>> >>> fail_put_module: >>>     module_put(sdev->host->hostt->module); >>> fail: >>>     return -ENXIO; >>> } >>> >> I don't think that's required. >> With your above analysis, wouldn't the problem be solved with: >> >> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c >> index 775df00021e4..911fcfa80d69 100644 >> --- a/drivers/scsi/scsi_sysfs.c >> +++ b/drivers/scsi/scsi_sysfs.c >> @@ -1470,6 +1470,8 @@ void __scsi_remove_device(struct scsi_device *sdev) >>          if (sdev->sdev_state == SDEV_DEL) >>                  return; >> >> +       scsi_block_when_processing_errors(sdev); >> + >>          if (sdev->is_visible) { >>                  /* >>                   * If scsi_internal_target_block() is running concurrently, >> >> Hmm? >> > > We can not make sure no scsi_cmnd remain unfinished after scsi_block_when_processing_errors(). For example, there is a > command has been dispatched but it's not timeouted when removing > device, no error happened. After scsi_device is set to SDEV_CANCEL, > the removing process would be blocked by del_gendisk() because there > is still a request. > > Then the request timeout and abort failed, error handle would be triggered, now scsi_device is SDEV_CANCEL. > > The error handle would skip this scsi_device when doing device reset. > >> Cheers, >> >> Hannes > Hi Hannes, Would you review these patches? Or do how do you suggest to fix the issues? thanks.