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

[Christoph Hellwig <hch@infradead.org>]

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.