osdmap consistency during incremental applying in kernel client

osdmap consistency during incremental applying in kernel client

[Chengguang Xu]

Hi All,

In ceph kernel client, osdmap_apply_incremental() can fail by failing of
allocation memory in many places, in this case, current osdmap can not
keep consistency after applying failure. 

I’m not sure how much impact will be caused by this kind of inconsistency
but for safety it’s better to keep osdmap consistency all the time even
failing from incremental applying. 

I’m trying to make some patches to fix this issue, but first of all please
let me know what do you think for this, I would be grateful if you could
share some ideas with me.



Thanks,
Chengguang.

Re: osdmap consistency during incremental applying in kernel client

[Ilya Dryomov]

On Mon, Feb 12, 2018 at 5:05 AM, Chengguang Xu <cgxu519@icloud.com> wrote:
> Hi All,
>
> In ceph kernel client, osdmap_apply_incremental() can fail by failing of
> allocation memory in many places, in this case, current osdmap can not
> keep consistency after applying failure.
>
> I’m not sure how much impact will be caused by this kind of inconsistency
> but for safety it’s better to keep osdmap consistency all the time even
> failing from incremental applying.

Hi Chengguang,

Well, in practice those are rather small allocations, so if you see any
of them failing, the system is likely in deep trouble.  In theory it is
a valid point though.

Thanks,

                Ilya

Re: osdmap consistency during incremental applying in kernel client

[Chengguang Xu]

Hi Ilya

Thanks for reply, please let me ask one more question, is there
no side-effect to ceph cluster side?

Thanks,
Chengguang.



> 在 2018年2月12日，下午5:37，Ilya Dryomov <idryomov@gmail.com> 写道：
> 
> On Mon, Feb 12, 2018 at 5:05 AM, Chengguang Xu <cgxu519@icloud.com> wrote:
>> Hi All,
>> 
>> In ceph kernel client, osdmap_apply_incremental() can fail by failing of
>> allocation memory in many places, in this case, current osdmap can not
>> keep consistency after applying failure.
>> 
>> I’m not sure how much impact will be caused by this kind of inconsistency
>> but for safety it’s better to keep osdmap consistency all the time even
>> failing from incremental applying.
> 
> Hi Chengguang,
> 
> Well, in practice those are rather small allocations, so if you see any
> of them failing, the system is likely in deep trouble.  In theory it is
> a valid point though.
> 
> Thanks,
> 
>                Ilya

Re: osdmap consistency during incremental applying in kernel client

[Ilya Dryomov]

On Mon, Feb 12, 2018 at 11:44 AM, Chengguang Xu <cgxu519@icloud.com> wrote:
> Hi Ilya
>
> Thanks for reply, please let me ask one more question, is there
> no side-effect to ceph cluster side?

No, there shouldn't be any.

Thanks,

                Ilya