[CRIU] [PATCH v7 01/15] sysctl: add CTL_FLAGS_HAS to mark successful sysctl_op request

[Pavel Emelyanov]

On 05/06/2016 03:10 PM, Pavel Tikhomirov wrote:
> On 05/06/2016 02:47 PM, Pavel Emelyanov wrote:
>> On 04/28/2016 07:38 PM, Pavel Tikhomirov wrote:
>>> v4: replace separate has pointer to CTL_FLAGS_HAS flag, second part in
>>> patch "net/ipv4: add net_conf_op to reuse for ipv6"
>>> v6: define CTL_FLAGS_HAS
>>> v7: also allow EIO on do_sysctl_op for optional sysctls like
>>> stable_secret and fix sysctl file to close in error path
>>
>> Wait a second. If we've managed to open a sysctl file, but failed to write into
>> it, why should we pretend as if there was not this sysctl at all?
> 
> Now we only set CTL_FLAGS_OPTIONAL for op == CTL_READ. So it meant to 
> be: if we opened sysctl but failed to read it, it is in 
> not-yet-initialized state and we can skip it safely.

I'm not sure that treating _any_ systl like this will work. Can you shed
more light on what's the issue with stable_secret sysctl is?

> Will adding an implicit op-check here be satisfactory?
> 
>>
>>>
>>> https://jira.sw.ru/browse/PSBM-30942
>>>
>>> Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
>>> ---
>>>  criu/include/sysctl.h |  1 +
>>>  criu/sysctl.c         | 21 +++++++++++++++++----
>>>  2 files changed, 18 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/criu/include/sysctl.h b/criu/include/sysctl.h
>>> index b949a40..3611ef1 100644
>>> --- a/criu/include/sysctl.h
>>> +++ b/criu/include/sysctl.h
>>> @@ -35,5 +35,6 @@ enum {
>>>   * Some entries might be missing mark them as optional.
>>>   */
>>>  #define CTL_FLAGS_OPTIONAL	1
>>> +#define CTL_FLAGS_HAS		2
>>>
>>>  #endif /* __CR_SYSCTL_H__ */
>>> diff --git a/criu/sysctl.c b/criu/sysctl.c
>>> index 21ae4ce..60e52db 100644
>>> --- a/criu/sysctl.c
>>> +++ b/criu/sysctl.c
>>> @@ -303,8 +303,13 @@ static int __userns_sysctl_op(void *arg, int proc_fd, pid_t pid)
>>>  		close(nsfd);
>>>
>>>  		for (i = 0; i < userns_req->nr_req; i++) {
>>> -			if (do_sysctl_op(fds[i], reqs[i], op) < 0)
>>> -				exit(1);
>>> +			if (do_sysctl_op(fds[i], reqs[i], op) < 0) {
>>> +				if (errno != EIO || !(req->flags & CTL_FLAGS_OPTIONAL))
>>> +					exit(1);
>>> +			} else {
>>> +				/* mark sysctl in question exists */
>>> +				req->flags |= CTL_FLAGS_HAS;
>>> +			}
>>>  		}
>>>
>>>  		exit(0);
>>> @@ -372,8 +377,16 @@ static int __nonuserns_sysctl_op(struct sysctl_req *req, size_t nr_req, int op)
>>>  		}
>>>
>>>  		ret = do_sysctl_op(fd, req, op);
>>> -		if (ret)
>>> -			goto out;
>>> +		if (ret) {
>>> +			if (errno != EIO || !(req->flags & CTL_FLAGS_OPTIONAL)) {
>>> +				close(fd);
>>> +				goto out;
>>> +			}
>>> +		} else {
>>> +			/* mark sysctl in question exists */
>>> +			req->flags |= CTL_FLAGS_HAS;
>>> +		}
>>> +
>>>  		close(fd);
>>>  		req++;
>>>  	}
>>>
>>
> .
>