Re: [patch] ceph: checking for IS_ERR instead of NULL

[Ilya Dryomov]

On Tue, Jan 26, 2016 at 3:51 PM, Yan, Zheng <zyan@xxxxxxxxxx> wrote:
>
>> On Jan 26, 2016, at 22:02, Ilya Dryomov <idryomov@xxxxxxxxx> wrote:
>>
>> On Tue, Jan 26, 2016 at 12:54 PM, Yan, Zheng <zyan@xxxxxxxxxx> wrote:
>>>
>>>> On Jan 26, 2016, at 19:40, Ilya Dryomov <idryomov@xxxxxxxxx> wrote:
>>>>
>>>> On Tue, Jan 26, 2016 at 12:16 PM, Yan, Zheng <zyan@xxxxxxxxxx> wrote:
>>>>>
>>>>>> On Jan 26, 2016, at 18:30, Ilya Dryomov <idryomov@xxxxxxxxx> wrote:
>>>>>>
>>>>>> On Tue, Jan 26, 2016 at 10:24 AM, Dan Carpenter
>>>>>> <dan.carpenter@xxxxxxxxxx> wrote:
>>>>>>> ceph_osdc_alloc_request() returns NULL on error, it never returns error
>>>>>>> pointers.
>>>>>>>
>>>>>>> Fixes: 5be0389dac66 ('ceph: re-send AIO write request when getting -EOLDSNAP error')
>>>>>>> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
>>>>>>>
>>>>>>> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
>>>>>>> index d37efdd..a52cf9b 100644
>>>>>>> --- a/fs/ceph/file.c
>>>>>>> +++ b/fs/ceph/file.c
>>>>>>> @@ -698,8 +698,8 @@ static void ceph_aio_retry_work(struct work_struct *work)
>>>>>>>
>>>>>>>      req = ceph_osdc_alloc_request(orig_req->r_osdc, snapc, 2,
>>>>>>>                      false, GFP_NOFS);
>>>>>>> -       if (IS_ERR(req)) {
>>>>>>> -               ret = PTR_ERR(req);
>>>>>>> +       if (!req) {
>>>>>>> +               ret = -ENOMEM;
>>>>>>>              req = orig_req;
>>>>>>>              goto out;
>>>>>>>      }
>>>>>>
>>>>>> Applied, thanks Dan.
>>>>>>
>>>>>> Zheng, I have an related concern: where do you put snapc (refcount is
>>>>>> bumped a few lines above) if ceph_osdc_alloc_request() fails?  It looks
>>>>>> like it's leaked to me.
>>>>>>
>>>>>> The BUG_ON(ret == -EOLDSNAPC) also seems a bit bogus, given that ret is
>>>>>> either -ENOMEM or ceph_osdc_start_request() retval.
>>>>>
>>>>> ceph_aio_complete_req treats -EOLDSNAP distinguishingly.  Purpose of this BUG_ON is detect potential infinite loop.
>>>>
>>>> Did you miss the part about the snap context?
>>>>
>>>> I get the purpose of -EOLDSNAPC assert in ceph_direct_read_write(),
>>>> where you can actually get it from ceph_osdc_wait_request() - it's
>>>> a server-side error code.  Asserting it in ceph_aio_retry_work(), in
>>>> which only client helpers are called and the only two possible error
>>>> codes are -ENOMEM and -EIO doesn't make much sense to me.
>>>>
>>>
>>> Yeah, removing that BUG_ON is completely OK.
>>
>> I still want to know where snapc is put ;)
>>
>
> you are right. I missed that

Great, you can remove that BUG_ON in the same commit then.

Thanks,

                Ilya