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 <haowenchao22@xxxxxxxxx>
>> ---
>> 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;
}
> Cheers,
>
> Hannes
