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

[Mike Snitzer <snitzer@redhat.com>]

On Mon, Mar 22 2021 at  4:11am -0400,
Christoph Hellwig <hch@infradead.org> wrote:

> On Sat, Mar 20, 2021 at 03:19:23PM +0800, Zhiqiang Liu wrote:
> > From: Zhiqiang Liu <liuzhiqiang26@huawei.com>
> > 
> > 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@huawei.com>
> > Signed-off-by: lixiaokeng <lixiaokeng@huawei.com>
> > Signed-off-by: linfeilong <linfeilong@huawei.com>
> > Signed-off-by: Wubo <wubo40@huawei.com>
> > ---
> >  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.