On Tue, Aug 26, 2014 at 10:37 AM, Boaz Harrosh <boaz@xxxxxxxxxxxxx> wrote: > On 08/26/2014 05:26 PM, Trond Myklebust wrote: >> On Tue, Aug 26, 2014 at 10:10 AM, Boaz Harrosh <boaz@xxxxxxxxxxxxx> wrote: >>> + >>> + /* kick out any segs held by need to commit */ >>> + pnfs_layoutcommit_inode(ino, true); >> >> Making this call synchronous could deadlock the entire back channel. >> Is there any reason why it can't just be made asynchonous? >> > > We were just talking about that. > > So the logic here is that we want to save round trips and make this > as efficient as possible with no extra round trips for the server > recall. A single RECALL => LAYOUT_COMMIT => LAYOUT_COMMIT_REPLAY > REACLL_REPLAY_NO_MATCHING. > > Please explain the deadlock you foresee. The worst is that the > mal-behaving server will time-out and after a long time the > RECALL_REPLAY will return with ERR. But why do you say deadlock > how can this deadlock? > > Otherwise Christoph's version of this patch does the asynchonous > way which will always cause another poll of the RECALL and more delays > for every RECALL operation, which I was trying to avoid. > > Thanks > Boaz > The above can deadlock if there are no session slots available to send the layoutcommit, in which case the recall won't complete, and the layoutget won't get a reply (which would free up the slot). -- Trond Myklebust Linux NFS client maintainer, PrimaryData trond.myklebust@xxxxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
