On Mon, Sep 05 2016, Guoqing Jiang wrote:
> On 09/04/2016 07:24 PM, NeilBrown wrote:
>> On Sun, Sep 04 2016, Guoqing Jiang wrote:
>>
>>> The md-cluster is compiled as module by default,
>>> if it is compiled by built-in way, then we can't
>>> make md-cluster works.
>>>
>>> [64782.630008] md/raid1:md127: active with 2 out of 2 mirrors
>>> [64782.630528] md-cluster module not found.
>>> [64782.630530] md127: Could not setup cluster service (-2)
>>>
>>> Fixes: edb39c9 ("Introduce md_cluster_operations to handle cluster functions")
>>> Cc: stable@xxxxxxxxxxxxxxx # v4.1+
>> The above results in you sending email to
>> stable@xxxxxxxxxxxxxxx#v4.1+
>> which is not a valid address.
>>
>> The correct form for comments in email address is to use parentheses.
>> e.g.
>> Cc: stable@xxxxxxxxxxxxxxx (v4.1+)
>
> Thanks for correct it!
>
>>> Cc: NeilBrown <neilb@xxxxxxxx>
>>> Reported-by: Marc Smith <marc.smith@xxxxxxx>
>>> Signed-off-by: Guoqing Jiang <gqjiang@xxxxxxxx>
>>> ---
>>> Changes:
>>> 1. call try_module_get if md_cluster_ops is already set,
>>> otherwise try_module_get/module_put are unbalanced.
>>>
>>> drivers/md/md.c | 14 +++++---------
>>> 1 file changed, 5 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/drivers/md/md.c b/drivers/md/md.c
>>> index 67642ba..6ac5abe 100644
>>> --- a/drivers/md/md.c
>>> +++ b/drivers/md/md.c
>>> @@ -7610,16 +7610,12 @@ EXPORT_SYMBOL(unregister_md_cluster_operations);
>>>
>>> int md_setup_cluster(struct mddev *mddev, int nodes)
>>> {
>>> - int err;
>>> -
>>> - err = request_module("md-cluster");
>>> - if (err) {
>>> - pr_err("md-cluster module not found.\n");
>>> - return -ENOENT;
>>> - }
>>> -
>>> + if (!md_cluster_ops)
>>> + request_module("md-cluster");
>>> spin_lock(&pers_lock);
>>> - if (!md_cluster_ops || !try_module_get(md_cluster_mod)) {
>>> + /* ensure module won't be unloaded */
>>> + if (!try_module_get(md_cluster_mod)) {
>> Why did you drop the "!md_cluster_ops" test?
>>
>> What happens if the md-cluster module cannot be loaded?
>> md_cluster_ops will be NULL and md_cluster_mod will be NULL.
>> try_module_get(NULL) succeeds, so with this patch md_setup_cluster()
>> will succeed if the module is needed but fails to load.
>
> Yes, I just find try_module_get(NULL) could return true, it seems not
> correct for the return value, maybe it need to be changed to:
>
> return module ? ret : false;
If a module is built into the kernel, then the module pointer that code
will use with be NULL, but you still want try_module_get() and
module_put() to work. So I think returning 'true' for NULL is correct.
>
> Anyway, I will send v3 with add "!md_cluster_ops" test back.
Thanks,
NeilBrown
Attachment:
signature.asc
Description: PGP signature
