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

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Date:	Tue, 26 Jan 2016 19:16:06 +0800
From:	"Yan, Zheng" <zyan@...hat.com>
To:	Ilya Dryomov <idryomov@...il.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 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.

Regards
Yan, Zheng


> 
>                Ilya