what i know is that librbd use applied callback, here is the code: in
send_write() calls librados::Rados::aio_create_completion, parameter
rados_req_cb is cb_safe, and cb_complete is NULL, the cb_safe is just
applied callback.
void AbstractWrite::send_write() {
ldout(m_ictx->cct, 20) << "send_write " << this << " " << m_oid << " "
<< m_object_off << "~" << m_object_len << dendl;
m_state = LIBRBD_AIO_WRITE_FLAT;
guard_write();
add_write_ops(&m_write);
assert(m_write.size() != 0);
librados::AioCompletion *rados_completion =
librados::Rados::aio_create_completion(this, NULL, rados_req_cb);
int r = m_ictx->data_ctx.aio_operate(m_oid, rados_completion, &m_write,
m_snap_seq, m_snaps);
assert(r == 0);
rados_completion->release();
}
librados::AioCompletion *librados::Rados::aio_create_completion(void *cb_arg,
callback_t cb_complete,
callback_t cb_safe)
{
AioCompletionImpl *c;
int r = rados_aio_create_completion(cb_arg, cb_complete, cb_safe, (void**)&c);
assert(r == 0);
return new AioCompletion(c);
}
anything wrong?
Regards,
Dong Wu
2015-12-31 10:33 GMT+08:00 min fang <louisfang2013@xxxxxxxxx>:
> yes, the question here is, librbd use the committed callback, as my
> understanding, when this callback returned, librbd write will be looked as
> completed. So I can issue a read IO even if the data is not readable. In
> this case, i would like to know what data will be returned for the read IO?
>
> 2015-12-31 10:29 GMT+08:00 Dong Wu <archer.wudong@xxxxxxxxx>:
>>
>> there are two callbacks: committed and applied, committed means write
>> to all replica's journal, applied means write to all replica's file
>> system. so when applied callback return to client, it means data can
>> be read.
>>
>> 2015-12-31 10:15 GMT+08:00 min fang <louisfang2013@xxxxxxxxx>:
>> > Hi, as my understanding, write IO will committed data to journal
>> > firstly,
>> > then give a safe callback to ceph client. So it is possible that data
>> > still
>> > in journal when I send a read IO to the same area. So what data will be
>> > returned if the new data still in journal?
>> >
>> > Thanks.
>> >
>> > _______________________________________________
>> > ceph-users mailing list
>> > ceph-users@xxxxxxxxxxxxxx
>> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>> >
>
>
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