> Anyway, suspend unconditionally purges all I/Os from target drivers. All > that this "noflush" flag does is that it allows the I/O to be held and > requeued for new dm table incarnation, if the target requests it with > DM_MAPIO_REQUEUE (dm-raid1 and dm-multipath do it). If no target returns > DM_MAPIO_REQUEUE, then "flush" and "noflush" suspend is equivalent. Hmm, I think it makes snapshot-of-mirrors implementation impossible. If we create the first snapshot or delete the last snapshot, we must inevitably suspend the underlying origin device. If we do a "flush" suspend and mirror log or leg fails at the same time, the i/o would be incorrectly returned with -EIO. If we do a "noflush" suspend, we couldn't synchronize the filesystem on snapshot creation and we couldn't get the I/Os out of origin target (because they would be queued in the underlying -real device). Mirrors must to be self-sufficient (i.e. handle errors on their own without queuing i/os and needing immediate action of dmeventd) to enable snapshots-of-mirrors work. Jon, will your log duplication work meet this requirement? Mikulas -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
