Re: [dm-level] upstream-queue-libmultipath: fix memory leak when iscsi login/out and "multipath -r" executed

[lixiaokeng <lixiaokeng@huawei.com>]

Hi.
    Thanks very much! I will try these patches.
-Lixiaokeng

On 2020/7/28 0:45, Benjamin Marzinski wrote:
> On Sat, Jul 25, 2020 at 01:47:01PM +0800, lixiaokeng wrote:
>> When one iscsi device logs in and logs out with the "multipath -r"
>> executed at the same time, memory leak happens in multipathd
>> process.
>>
>> The reason is following. When "multipath -r" is executed, the path
>> will be free in configure function. Before path_discovery executed,
>> iscsi device logs out. Then path_discovery will not find any path and
>> there is no path in the gvecs->pathvec. When map_discovery function
>> is executed, disassemble_map function will be called. Because
>> gvecs->pathvec->slot is empty and is_deamon is 1, a path will be
>> allocated and is not stored in gvecs->pathvec but store in
>> mpp->pg. But when the mpp is removed and freed by remove_map
>> function, the path will not be free and can't be find anymore.
>>
>> The procedure details given as follows,
>> 1."multipath -r" is executed
>> main
>> 	->child
>> 		->reconfigure
>> 			->configure
>> 				->path_discovery //after iscsi logout
>> 				->map_discovery
>> 					->update_multipath_table
>> 						->disassemble_map
>> 							->alloc_path
>> 2.then "multipath -r" is executed again
>> main
>> main
>> 	->child
>> 		->reconfigure
>> 			->remove_maps_and_stop_waiters
>> 				->remove_maps
>>
>> Here, we delete checking is_deamon. Because whether the process is a
>> daemon process or not, we think the path should be add to gvecs->pathvec.
> 
> There is more work that needs to be done to besides removing the is_daemon
> check.  However, Martin already posted patches that deal with this as
> part of the his large patchset.
> 
> https://www.redhat.com/archives/dm-devel/2020-July/msg00245.html
> 
> You should take a look at those, and at my comments on them, because they
> should resolve your issue.
> 
> -Ben
> 
>>
>> Reported-by: Tianxiong Li <lutianxiong@huawei.com>
>> Signed-off-by: Lixiaokeng <lixiaokeng@huawei.com>
>> Signed-off-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
>>
>> ---
>>  libmultipath/dmparser.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/libmultipath/dmparser.c b/libmultipath/dmparser.c
>> index b856a07f..d556f642 100644
>> --- a/libmultipath/dmparser.c
>> +++ b/libmultipath/dmparser.c
>> @@ -315,7 +315,7 @@ int disassemble_map(vector pathvec, char *params, struct multipath *mpp,
>>  						WWID_SIZE);
>>  				}
>>  				/* Only call this in multipath client mode */
>> -				if (!is_daemon && store_path(pathvec, pp))
>> +				if (store_path(pathvec, pp))
>>  					goto out1;
>>  			} else {
>>  				if (!strlen(pp->wwid) &&
>> --
> 
> 
> .
>