Keep in mind that this coordination is largely happening above the FileStore layer, so you are indeed not seeing any code within the FileStore to support it. :) But operations within the OSD are ordered on a per-PG basis, and while in-progress writes can overlap, a read will be blocked until the writes are applied (and subsequent writes will be blocked behind the read). -Greg Software Engineer #42 @ http://inktank.com | http://ceph.com
On Tue, Jul 22, 2014 at 8:58 PM, Haomai Wang <haomaiw...@gmail.com> wrote: > Read will get the newest content. If the read arrives during the write > interval, it will wait for the write applied. > > On Wed, Jul 23, 2014 at 10:22 AM, James Pan <dev...@yahoo.com> wrote: >> Hi everyone, >> >> I am reading the FileStore source code and confused with the read() and >> write() process. >> >> If journal is enable, write() will be acknowledged after the changes are >> committed to the journal device but before they are applied to the file >> system. However read() is always satisfied from the OSD file on the file >> system, so if a read arrives during this interval. Will the read get the >> stale data? Does this behavior break the read-after-write posix semantics? >> Shouldn't the read go to the journal for the latest data? >> >> Please point me out if my understanding is incorrect, thanks very much. >> >> Best regards, >> James Pan >> >> _______________________________________________ >> ceph-users mailing list >> ceph-users@lists.ceph.com >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > > > -- > Best Regards, > > Wheat > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
