Re: [dm-devel] [PATCH 1/2] libmultipath: support host adapter name lookup for s390x ccw bus

[Benjamin Marzinski <bmarzins@redhat.com>]

On Wed, Feb 09, 2022 at 08:47:12PM +0100, Steffen Maier wrote:
> There are also (FCP) HBAs that appear on a bus different from PCI.
> 
> Complements v0.6.0 commit
> 01ab2a468ea2 ("libmultipath: Add additional path wildcards").
> 
> With that we can easily get the full FCP addressing triplet
> (HBA, WWPN, LUN) from multipath tools without additional tools
> and correlation:
> 
> $ multipathd -k'show paths format "%w|%i|%a|%r"'
> uuid                             |hcil       |host adapter|target WWPN
> 36005076400820293e8000000000000a0|1:0:3:160  |0.0.5080    |0x500507680b25c449
> 36005076400820293e8000000000000a0|1:0:4:160  |0.0.5080    |0x500507680b25c448
> 36005076400820293e8000000000000a0|58:0:3:160 |0.0.50c0    |0x500507680b26c449
> 36005076400820293e8000000000000a0|58:0:4:160 |0.0.50c0    |0x500507680b26c448
> 
>                                               ^^^^^^^^
>                                    instead of [undef]
> 
> As a side effect this patch theoretically also enables group by
> host adapter for s390x based on v0.6.0 commit a28e61e5cc9a
> ("Crafted ordering of child paths for round robin path selector").

This looks good in general, but I have some minor issues.
 
> Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
> Signed-off-by: Steffen Maier <maier@linux.ibm.com>
> ---
>  libmultipath/discovery.c | 41 +++++++++++++++++++++++++++++++++++++++-
>  libmultipath/discovery.h |  1 +
>  2 files changed, 41 insertions(+), 1 deletion(-)
> 
> diff --git a/libmultipath/discovery.c b/libmultipath/discovery.c
> index 7d939ae08004..bb4913d9b75f 100644
> --- a/libmultipath/discovery.c
> +++ b/libmultipath/discovery.c
> @@ -497,8 +497,12 @@ int sysfs_get_host_adapter_name(const struct path *pp, char *adapter_name)
>  		return sysfs_get_iscsi_ip_address(pp, adapter_name);
>  
>  	/* fetch adapter pci name for other protocols
> +	 * or try to get s390x channel subsystem FCP device bus-ID [zfcp]
>  	 */
> -	return sysfs_get_host_pci_name(pp, adapter_name);
> +	if (sysfs_get_host_pci_name(pp, adapter_name))
> +		return sysfs_get_host_ccw_name(pp, adapter_name);
> +	else
> +		return 0;
>  }
>  
>  int sysfs_get_host_pci_name(const struct path *pp, char *pci_name)
> @@ -545,6 +549,41 @@ int sysfs_get_host_pci_name(const struct path *pp, char *pci_name)
>  	return 1;
>  }
>  

I realize that sysfs_get_host_pci_name() isn't a global function, but
there's no good reason for that, since nothing calls it outside of
discovery.c. sysfs_get_host_ccw_name() should be static.
> +int sysfs_get_host_ccw_name(const struct path *pp, char *ccw_name)
> +{

This looks very much like sysfs_get_host_pci_name(). The only difference
is in grabbing the correct sysfs parent.  It seems like they could be
combined into one function that first attempts to grab the pci device,
and failing that, grabs the ccw device.

Unless, or course, there is a good reason why we might want to call
these functions outside of sysfs_get_host_adapter_name() that I'm
missing. If so, you can ignore all this. 

Thanks
-Ben

> +	struct udev_device *hostdev, *parent;
> +	char host_name[HOST_NAME_LEN];
> +	const char *value;
> +
> +	if (!pp || !ccw_name)
> +		return 1;
> +
> +	sprintf(host_name, "host%d", pp->sg_id.host_no);
> +	hostdev = udev_device_new_from_subsystem_sysname(udev,
> +			"scsi_host", host_name);
> +	if (!hostdev)
> +		return 1;
> +
> +	parent = udev_device_get_parent_with_subsystem_devtype(hostdev, "ccw",
> +							       NULL);
> +	if (parent) {
> +		/* s390x ccw FCP device found
> +		 */
> +		value = udev_device_get_sysname(parent);
> +
> +		if (!value) {
> +			udev_device_unref(hostdev);
> +			return 1;
> +		}
> +
> +		strncpy(ccw_name, value, SLOT_NAME_SIZE);
> +		udev_device_unref(hostdev);
> +		return 0;
> +	}
> +	udev_device_unref(hostdev);
> +	return 1;
> +}
> +
>  int sysfs_get_iscsi_ip_address(const struct path *pp, char *ip_address)
>  {
>  	struct udev_device *hostdev;
> diff --git a/libmultipath/discovery.h b/libmultipath/discovery.h
> index 095657bb9de4..0a58c725d700 100644
> --- a/libmultipath/discovery.h
> +++ b/libmultipath/discovery.h
> @@ -44,6 +44,7 @@ int store_pathinfo (vector pathvec, struct config *conf,
>  		    struct path **pp_ptr);
>  int sysfs_set_scsi_tmo (struct multipath *mpp, unsigned int checkint);
>  int sysfs_get_timeout(const struct path *pp, unsigned int *timeout);
> +int sysfs_get_host_ccw_name(const struct path *pp, char *ccw_name);
>  int sysfs_get_host_pci_name(const struct path *pp, char *pci_name);
>  int sysfs_get_iscsi_ip_address(const struct path *pp, char *ip_address);
>  int sysfs_get_host_adapter_name(const struct path *pp,
> 
> base-commit: d9d7ae9e2125116b465b4ff4d98ce65fe0eac3cc
> -- 
> 2.27.0

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