Re: md/dm-mpath: check whether all pgpaths have same uuid in multipath_ctr()

[Zhiqiang Liu]

On 2021/3/24 1:11, Ewan D. Milne wrote:
> On Tue, 2021-03-23 at 15:47 +0800, lixiaokeng wrote:
>>
>> On 2021/3/22 22:22, Mike Snitzer wrote:
>>> On Mon, Mar 22 2021 at  4:11am -0400,
>>> Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
>>>
>>>> On Sat, Mar 20, 2021 at 03:19:23PM +0800, Zhiqiang Liu wrote:
>>>>> From: Zhiqiang Liu <liuzhiqiang26@xxxxxxxxxx>
>>>>>
>>>>> When we make IO stress test on multipath device, there will
>>>>> be a metadata err because of wrong path. In the test, we
>>>>> concurrent execute 'iscsi device login|logout' and
>>>>> 'multipath -r' command with IO stress on multipath device.
>>>>> In some case, systemd-udevd may have not time to process
>>>>> uevents of iscsi device logout|login, and then 'multipath -r'
>>>>> command triggers multipathd daemon calls ioctl to load table
>>>>> with incorrect old device info from systemd-udevd.
>>>>> Then, one iscsi path may be incorrectly attached to another
>>>>> multipath which has different uuid. Finally, the metadata err
>>>>> occurs when umounting filesystem to down write metadata on
>>>>> the iscsi device which is actually not owned by the multipath
>>>>> device.
>>>>>
>>>>> So we need to check whether all pgpaths of one multipath have
>>>>> the same uuid, if not, we should throw a error.
>>>>>
>>>>> Signed-off-by: Zhiqiang Liu <liuzhiqiang26@xxxxxxxxxx>
>>>>> Signed-off-by: lixiaokeng <lixiaokeng@xxxxxxxxxx>
>>>>> Signed-off-by: linfeilong <linfeilong@xxxxxxxxxx>
>>>>> Signed-off-by: Wubo <wubo40@xxxxxxxxxx>
>>>>> ---
>>>>>  drivers/md/dm-mpath.c   | 52
>>>>> +++++++++++++++++++++++++++++++++++++++++
>>>>>  drivers/scsi/scsi_lib.c |  1 +
>>>>>  2 files changed, 53 insertions(+)
>>>>>
>>>>> diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
>>>>> index bced42f082b0..f0b995784b53 100644
>>>>> --- a/drivers/md/dm-mpath.c
>>>>> +++ b/drivers/md/dm-mpath.c
>>>>> @@ -24,6 +24,7 @@
>>>>>  #include <linux/workqueue.h>
>>>>>  #include <linux/delay.h>
>>>>>  #include <scsi/scsi_dh.h>
>>>>> +#include <linux/dm-ioctl.h>
>>>>>  #include <linux/atomic.h>
>>>>>  #include <linux/blk-mq.h>
>>>>>
>>>>> @@ -1169,6 +1170,45 @@ static int parse_features(struct
>>>>> dm_arg_set *as, struct multipath *m)
>>>>>  	return r;
>>>>>  }
>>>>>
>>>>> +#define SCSI_VPD_LUN_ID_PREFIX_LEN 4
>>>>> +#define MPATH_UUID_PREFIX_LEN 7
>>>>> +static int check_pg_uuid(struct priority_group *pg, char
>>>>> *md_uuid)
>>>>> +{
>>>>> +	char pgpath_uuid[DM_UUID_LEN] = {0};
>>>>> +	struct request_queue *q;
>>>>> +	struct pgpath *pgpath;
>>>>> +	struct scsi_device *sdev;
>>>>> +	ssize_t count;
>>>>> +	int r = 0;
>>>>> +
>>>>> +	list_for_each_entry(pgpath, &pg->pgpaths, list) {
>>>>> +		q = bdev_get_queue(pgpath->path.dev->bdev);
>>>>> +		sdev = scsi_device_from_queue(q);
>>>>
>>>> Common dm-multipath code should never poke into scsi
>>>> internals.  This
>>>> is something for the device handler to check.  It probably also
>>>> won't
>>>> work for all older devices.
>>>
>>> Definitely.
>>>
>>> But that aside, userspace (multipathd) _should_ be able to do extra
>>> validation, _before_ pushing down a new table to the kernel, rather
>>> than
>>> forcing the kernel to do it.
>>>
>>
>> Martin (committer of multipath-tools) said that:
>> "Don't get me wrong, I don't argue against tough testing. But we
>> should
>> be aware that there are always time intervals during which
>> multipathd's
>> picture of the present devices is different from what the kernel
>> sees."
>>
>> It is difficult to solve this in multipathd.
>>
>> Regards,
>> Lixiaokeng
>>
> 
> I think the patch is no good.  There are plenty of devices that don't
> support VPD page 83h:
> 
> int scsi_vpd_lun_id(struct scsi_device *sdev, char *id, size_t id_len)
> {
>         u8 cur_id_type = 0xff;
>         u8 cur_id_size = 0;
>         unsigned char *d, *cur_id_str;
>         unsigned char __rcu *vpd_pg83;
>         int id_size = -EINVAL;
> 
>         rcu_read_lock();
>         vpd_pg83 = rcu_dereference(sdev->vpd_pg83);
>         if (!vpd_pg83) {
>                 rcu_read_unlock();
>                 return -ENXIO;
>         }
> 
> and the DM layer should not be looking at the properties of the
> underlying devices in this way anyway.  It should be pushed down
> to the table.
> 
Thanks for your suggestion.
I will have a try to modify the patch as your advice.


Regards
Zhiqiang Liu.
> -Ewan
> 
> 
> 
> 
> .
>