If the data has not been written to filestore, as you mentioned, it is
still in journal, your following read op will be blocked until the
data is written to filestore.
This is because when writing this data, the related object context
will hold ondisk_write_lock. This lock will be released in a callback
after data is in filestore. When ondisk_write_lock is held, read op to
this data will be blocked.
Regards,
Zhi Zhang (David)
Contact: zhang.david2011@xxxxxxxxx
zhangz.david@xxxxxxxxxxx
On Thu, Dec 31, 2015 at 10:33 AM, min fang <louisfang2013@xxxxxxxxx> wrote:
> 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
>> >
>
>
>
> _______________________________________________
> ceph-users mailing list
> ceph-users@xxxxxxxxxxxxxx
> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>
_______________________________________________
ceph-users mailing list
ceph-users@xxxxxxxxxxxxxx
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
