Oren Laadan [orenl@xxxxxxxxxxxxxxx] wrote: | | | On 05/25/2010 09:07 PM, Sukadev Bhattiprolu wrote: | > If process P1 has a F_WRLCK lease on file F1 and process P2 opens the | > file, P2's open() blocks for lease_break_time (45 seconds) and P1 gets | > a SIGIO to cleanup it lease in preparation for P2's open. If the two | > processes are checkpointed/restarted in this window, we should address | > following two issues: | > | > - P1 should get a SIGIO only once for the lease (i.e if P1 got the | > SIGIO before checkpoint, it should not get the SIGIO after restart). | | The qualification "before" is vague in our case - a checkpoint is | potentially a length operation, so before *which part* of the | checkpoint you mean here ? I should have been more specific. I meant - if P1 got the SIGIO before freezing the container for checkpoint, it should not get the SIGIO after restart/unfreeze. So checkpoint can take minutes, but if P2 is in the same container and P2 is frozen too. | > | > - If R seconds remain in the lease, P2's open should be blocked for | > at least the R seconds, so P1 has the time to clean up its lease. | > The previous patch gives P1 the entire lease_break_time but that | > can leave P2 stalled for 2*lease_break_time. | > | > To address first, we add a field ->fl_break_notified to "remember" if we | > notified the lease-holder already. We save this field in the checkpoint | > image and when restarting, we notify the lease-holder only if this field | > is not set. | | I'm not sure I understand. | | Signals are saved last, in particular they are saved after files, and | file leases. What happens if we at checkpoint, we look at a file lease - | we save the least_break_time, now we proceed with the checkpoint, now | the lease expires before we are done, so we get a signal, and finally | we save the signals. In this case, we get both an expiry time and the | signal recorded. | | (Am I mis-reading the code ?) The signal is sent when P2 opens the file and lease-break is initiated. No signal is sent when the lease actually expires. So when P1 and P2 are *both frozen*, then only one of these are true right ? - P2 initiated the lease-break and sent the SIGIO or - the lease-break was not initiated at all As youmentioned in your other email, I will look into the ctx->ktime_begin. | | It seems to me that we need to mark the file lease at checkpoint to | prevent the signal from being sent until _after_ the checkpoint ends | (as opposed to remembering that the signal was sent). And then at the | end of the checkpoint, iterate through the leases for each marked | lease - remove the mark and fire the signal. | | Oren. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
