linux-kernel - Re: [patch] ceph: checking for IS

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Message-ID: <CAOi1vP9UDdoTXPu_Cd3ZYzezj7E0TgVt38b-za_dnktsAOYMwA@mail.gmail.com>
Date:	Tue, 26 Jan 2016 15:02:05 +0100
From:	Ilya Dryomov <idryomov@...il.com>
To:	"Yan, Zheng" <zyan@...hat.com>
Cc:	Dan Carpenter <dan.carpenter@...cle.com>,
	Sage Weil <sage@...hat.com>,
	Ceph Development <ceph-devel@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	kernel-janitors@...r.kernel.org
Subject: Re: [patch] ceph: checking for IS_ERR instead of NULL

On Tue, Jan 26, 2016 at 12:54 PM, Yan, Zheng <zyan@...hat.com> wrote:
>
>> On Jan 26, 2016, at 19:40, Ilya Dryomov <idryomov@...il.com> wrote:
>>
>> On Tue, Jan 26, 2016 at 12:16 PM, Yan, Zheng <zyan@...hat.com> wrote:
>>>
>>>> On Jan 26, 2016, at 18:30, Ilya Dryomov <idryomov@...il.com> wrote:
>>>>
>>>> On Tue, Jan 26, 2016 at 10:24 AM, Dan Carpenter
>>>> <dan.carpenter@...cle.com> 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@...cle.com>
>>>>>
>>>>> 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 ;)

Thanks,

                Ilya