[libvirt] [PATCH 3/4] storage_conf: Fix the scsi_host.name comparison

[John Ferlan]

On 10/03/2014 09:20 AM, Ján Tomko wrote:
> On 09/30/2014 11:35 PM, John Ferlan wrote:
>> Since the 'scsi_host#' concept was introduced in commit id '9f781da6' it
>> is possible to provide either "name='host#'" or "name='scsi_host#'" to
>> define/name the scsi_host adapter source address.  The concept being
>> that 'name#' is/was legacy and 'scsi_host#' is what's seen in the
>> 'virsh nodedev-list [--cap scsi_host]' output.  However, in doing the
>> comparison for a to be defined scsi_host, a latent bug allows the same
>> source to be defined twice, e.g. "name='host5'" is not distiguished
>> from "name='scsi_host5'", although in reality they eventually become
>> the same thing in commit id 'c1f63a9b' with the introduction of the
>> getHostNumber() API.
>>
>> So this change will ensure that no one can use 'host5' and 'scsi_host5'
>> (or whatever #) to resolve to the same source adapter when going through
>> the define the source adapter processing and checking for duplicates. Doing
>> so will now result in an error (assuming that an existing pool is using
>> 'host5' and the to be defined pool tries 'scsi_host5'):
>>
>> $ virsh pool-define scsi-pool-use-scsi_host.xml
>> error: Failed to define pool from scsi-pool-use-scsi_host.xml
>> error: operation failed: Storage source conflict with pool: 'scsi-pool-use-host
>> $
>>
>> Signed-off-by: John Ferlan <jferlan at redhat.com>
>> ---
>>  src/conf/storage_conf.c | 25 +++++++++++++++++++++++--
>>  1 file changed, 23 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/conf/storage_conf.c b/src/conf/storage_conf.c
>> index ac41307..74267bd 100644
>> --- a/src/conf/storage_conf.c
>> +++ b/src/conf/storage_conf.c
>> @@ -2063,6 +2063,27 @@ virStoragePoolObjIsDuplicate(virStoragePoolObjListPtr pools,
>>  }
>>  
>>  static bool
>> +matchSCSIAdapterName(const char *pool_name,
>> +                     const char *def_name)
>> +{
>> +    /* Names can be either "scsi_host#" or just "host#", where
>> +     * "host#" is the back-compat format, but both equate to
>> +     * the same source adapter.  First check if both pool and def
>> +     * are using same format (easier) - if so, then compare
>> +     */
>> +    if ((STRPREFIX(pool_name, "scsi_") && STRPREFIX(def_name, "scsi")) ||
>> +        (STRPREFIX(pool_name, "host") && STRPREFIX(def_name, "host")))
>> +        return STREQ(pool_name, def_name);
>> +
>> +    /* If pool uses "scsi_host#" and def uses "host#", deal with that here */
>> +    if (STRPREFIX(pool_name, "scsi_"))
>> +        return STREQ(&pool_name[5], def_name);
>> +
>> +    /* Otherwise we have pool with "host#" and def with "scsi_host#" */
>> +    return STREQ(pool_name, &def_name[5]);
>> +}
> 
> fc_host prefix is not handled here, but getHostNumber will allow it. Maybe the
> checks should be shared? (as long as we don't error out on unknown prefixes,
> since we didn't validate the adapter name in the past).
> 

Not clear what kind of sharing would be expected (perhaps it's my code
myopia)...  The previous (and current to this patch) code does validate
the name - at least to the degree that the incoming name isn't already
in use or the name that the incoming definition would resolve to in the
case of parentaddr. It is broken - which is what this set of patches
looks to resolve.

If you go back to patch 1/4 - you will see for a "type='scsi_host'" pool
we'd previously either simply match the incoming name against name of
the pool (assuming the the incoming def had a name instead of
parentaddr) or we'd match the parentaddr (assuming that if the current
pool def was using a parentaddr that the incoming def would be too).

All this patch does is ensure that someone cannot provide "name='host3'"
for one pool while providing "name='scsi_host3'" for another pool for
the Create/Define (or vice versa). There is no bug on this - I just
noted this while working on the code.

matchSCSIAdapter[Name|Parent] is called during the Create/Define pool
processing to ensure we don't allow user defined duplicate names of
existing pools for SCSI_HOST pools only (eg, type='scsi_host' instead of
type='fc_host'). A FC_HOST pool would disallow matches for the unique
wwnn/wwpn pairs.  Yes it does use "parent='scsi_host#'" as a name, but
that's only to find the scsi_host# defined - see
http://wiki.libvirt.org/page/NPIV_in_libvirt during the start or refresh
processing (in getHostNumber).

The getHostNumber is used by the scsi pool driver during the Check or
Refresh processing in order to fetch which user provided name that was
created/defined for use in finding the on disk
/sys/class/scsi_host/host# directory in order to find either the fc_host
or scsi_host data.  The fc_host processing has/uses a
"parent='scsi_host#'" in order to define the vHBA with the the vport
(wwnn/wwpn).  I'm not even sure at this point if fc_host could be a
proper prefix, but that's a different issue.

I can rename this set of functions to something like
matchSCSIHostAdapterType[Name|Parent] if it's clearer, but I guess I'm
missing the synergy.


John