| Message ID | 20230321084204.1860900-1-yebin@huaweicloud.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | scsi: fix hung_task when change host from recovery to running via sysfs | expand |
On Tue, Mar 21, 2023 at 04:42:04PM +0800, Ye Bin wrote: > From: Ye Bin <yebin10@huawei.com> > > When do follow test: > Step1: echo "recovery" > /sys/class/scsi_host/host0/state Hmm, that make me wonder, what potential use-case this is for? Just testing? For SDEVs we explicitly filter what states can be set from user-space. Only `SDEV_RUNNING` and `SDEV_OFFLINE` can be set in `store_state_field()`. There is probably quite a few other bad things you can do with this interface by using any of the other states used for device destruction or EH, and then trigger I/O or said destruction/EH otherwise. Not sure handling this one special case of `SHOST_RECOVERY` is quite enough. > diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c > index ee28f73af4d4..ae6b1476b869 100644 > --- a/drivers/scsi/scsi_sysfs.c > +++ b/drivers/scsi/scsi_sysfs.c > @@ -216,6 +216,9 @@ store_shost_state(struct device *dev, struct device_attribute *attr, > > if (scsi_host_set_state(shost, state)) > return -EINVAL; > + else > + wake_up(&shost->host_wait); > + > return count; > } > > -- > 2.31.1 >
On 2023/3/21 22:22, Benjamin Block wrote: > On Tue, Mar 21, 2023 at 04:42:04PM +0800, Ye Bin wrote: >> From: Ye Bin <yebin10@huawei.com> >> >> When do follow test: >> Step1: echo "recovery" > /sys/class/scsi_host/host0/state > Hmm, that make me wonder, what potential use-case this is for? Just > testing? Thank you for your reply. Actually, I'm looking for a way to temporarily stop sending IO to the driver. Setting the state of the host to recovery can do this, but I changed the state to running and found that the process could not be woken up. I don't know what the purpose of designing this sysfs interface was. But this modification can solve the effect I want to achieve. > For SDEVs we explicitly filter what states can be set from user-space. > Only `SDEV_RUNNING` and `SDEV_OFFLINE` can be set in > `store_state_field()`. > There is probably quite a few other bad things you can do with this > interface by using any of the other states used for device destruction > or EH, and then trigger I/O or said destruction/EH otherwise. > Not sure handling this one special case of `SHOST_RECOVERY` is quite > enough. > > >> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c >> index ee28f73af4d4..ae6b1476b869 100644 >> --- a/drivers/scsi/scsi_sysfs.c >> +++ b/drivers/scsi/scsi_sysfs.c >> @@ -216,6 +216,9 @@ store_shost_state(struct device *dev, struct device_attribute *attr, >> >> if (scsi_host_set_state(shost, state)) >> return -EINVAL; >> + else >> + wake_up(&shost->host_wait); >> + >> return count; >> } >> >> -- >> 2.31.1 >>
On Wed, Mar 22, 2023 at 09:24:32AM +0800, yebin (H) wrote: > On 2023/3/21 22:22, Benjamin Block wrote: > > On Tue, Mar 21, 2023 at 04:42:04PM +0800, Ye Bin wrote: > >> From: Ye Bin <yebin10@huawei.com> > >> > >> When do follow test: > >> Step1: echo "recovery" > /sys/class/scsi_host/host0/state > > > > Hmm, that make me wonder, what potential use-case this is for? Just > > testing? > > Thank you for your reply. > Actually, I'm looking for a way to temporarily stop sending IO to the > driver. > Setting the state of the host to recovery can do this, but I changed > the state to running and found that the process could not be woken up. > I don't know what the purpose of designing this sysfs interface was. > But this modification can solve the effect I want to achieve. My first thought when seeing this was that maybe we should also limit this interface to say `SHOST_RUNNING` and `SHOST_RECOVERY` (similar to what is done in `store_state_field()`). That would limit the amount of corner cases drastically. And in case of setting `SHOST_RUNNING` after the scsi host was set to `SHOST_RECOVERY`, we could also make use of the already existing function `scsi_restart_operations()` to handle the restart in the same way as EH does. But it's not up to me, to make that call. > > For SDEVs we explicitly filter what states can be set from user-space. > > Only `SDEV_RUNNING` and `SDEV_OFFLINE` can be set in > > `store_state_field()`. > > There is probably quite a few other bad things you can do with this > > interface by using any of the other states used for device destruction > > or EH, and then trigger I/O or said destruction/EH otherwise. > > Not sure handling this one special case of `SHOST_RECOVERY` is quite > > enough. > > > >> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c > >> index ee28f73af4d4..ae6b1476b869 100644 > >> --- a/drivers/scsi/scsi_sysfs.c > >> +++ b/drivers/scsi/scsi_sysfs.c > >> @@ -216,6 +216,9 @@ store_shost_state(struct device *dev, struct device_attribute *attr, > >> > >> if (scsi_host_set_state(shost, state)) > >> return -EINVAL; > >> + else > >> + wake_up(&shost->host_wait); In the very least, this should first check whether we really just made the transition from `SHOST_RECOVERY` to `SHOST_RUNNING` before calling this `wake_up()`. And for that - first get old state, then set the new state - we probably would also need to grab the `host_lock` to make that race free. Just calling `wake_up()` without knowing what state transition we just made doesn't sound right to me. > >> + > >> return count; > >> } > >> > >> -- > >> 2.31.1 > >> >
On 3/23/23 5:21 AM, Benjamin Block wrote: > On Wed, Mar 22, 2023 at 09:24:32AM +0800, yebin (H) wrote: >> On 2023/3/21 22:22, Benjamin Block wrote: >>> On Tue, Mar 21, 2023 at 04:42:04PM +0800, Ye Bin wrote: >>>> From: Ye Bin <yebin10@huawei.com> >>>> >>>> When do follow test: >>>> Step1: echo "recovery" > /sys/class/scsi_host/host0/state >>> >>> Hmm, that make me wonder, what potential use-case this is for? Just >>> testing? >> >> Thank you for your reply. >> Actually, I'm looking for a way to temporarily stop sending IO to the >> driver. >> Setting the state of the host to recovery can do this, but I changed >> the state to running and found that the process could not be woken up. >> I don't know what the purpose of designing this sysfs interface was. >> But this modification can solve the effect I want to achieve. > > My first thought when seeing this was that maybe we should also limit > this interface to say `SHOST_RUNNING` and `SHOST_RECOVERY` (similar to > what is done in `store_state_field()`). > That would limit the amount of corner cases drastically. > > And in case of setting `SHOST_RUNNING` after the scsi host was set to > `SHOST_RECOVERY`, we could also make use of the already existing > function `scsi_restart_operations()` to handle the restart in the same > way as EH does. > I agree we should limit the states we can set. It doesn't make sense for userspace to be able to set states like SHOST_CANCEL and I think it would later break functions like scsi_remove_host. Maybe instead of allowing SHOST_RECOVERY to be used by userspace we want a new state SHOST_BLOCKED which just does the specific operation we want. If we re-use SHOST_RECOVERY for userspace blocking IO there could be issues later on because that state also means we are going to be performing the eh callouts and not just stopping IO. Or maybe instead of a different state we just add another shost field similar to tmf_in_progress which forces scsi_queue_rq to not queue IO to the drivers.
On 3/21/23 8:24 PM, yebin (H) wrote: > > > On 2023/3/21 22:22, Benjamin Block wrote: >> On Tue, Mar 21, 2023 at 04:42:04PM +0800, Ye Bin wrote: >>> From: Ye Bin <yebin10@huawei.com> >>> >>> When do follow test: >>> Step1: echo "recovery" > /sys/class/scsi_host/host0/state >> Hmm, that make me wonder, what potential use-case this is for? Just >> testing? > Thank you for your reply. > Actually, I'm looking for a way to temporarily stop sending IO to the driver. Is this just for testing something or does a user/app need this functionality for something? We used to be able to block specific devices but we removed that. It was useful for people like us where we need to do some low kernel testing like testing for how upper layers handle IO hangs, but I think it was not useful for other users so it was removed.
On 2023/3/24 0:12, Mike Christie wrote: > On 3/21/23 8:24 PM, yebin (H) wrote: >> >> On 2023/3/21 22:22, Benjamin Block wrote: >>> On Tue, Mar 21, 2023 at 04:42:04PM +0800, Ye Bin wrote: >>>> From: Ye Bin <yebin10@huawei.com> >>>> >>>> When do follow test: >>>> Step1: echo "recovery" > /sys/class/scsi_host/host0/state >>> Hmm, that make me wonder, what potential use-case this is for? Just >>> testing? >> Thank you for your reply. >> Actually, I'm looking for a way to temporarily stop sending IO to the driver. > Is this just for testing something or does a user/app need this > functionality for something? This can be used to store IO in the block layer, enabling some fault recovery that is insensitive to the upper layer.Also want to use this state to test the block layer. > We used to be able to block specific devices but we removed that. > It was useful for people like us where we need to do some low kernel > testing like testing for how upper layers handle IO hangs, but I > think it was not useful for other users so it was removed. > > . >
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c index ee28f73af4d4..ae6b1476b869 100644 --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -216,6 +216,9 @@ store_shost_state(struct device *dev, struct device_attribute *attr, if (scsi_host_set_state(shost, state)) return -EINVAL; + else + wake_up(&shost->host_wait); + return count; }