Hello Tang, ＞ In the second case, we know all events in the sequence have the > same > ＞ WWID; in this case I think it would be safe to filter away "remove" > ＞ events by subsequent "add" events, ending up with "add path1| add > ＞ path2| remove path3". But I may be overlooking something here. > > ＞ The dangerous thing if you have simultaneous remove and add events > for > ＞ the same LUN is that processing the "add" events is likely to fail > in > ＞ domap(). If you get "add path1 | remove path2", once you process > "add > ＞ path1", "path2" may not exist in the kernel any more, and "domap" > will > ＞ fail if you try to set up both; you may end up removing the map > ＞ completely. IMHO the only safe way to process events in this > situation > ＞ is to merge the events into a single domap() call. > > "case 2: remove path1 |add path1 |remove path2 |add path2 |remove > path3" > Since the mergering is starting from the latest to the eariest > uevent, so the > uevent "remove path3" try to merger other uevents, if we do not stop > mergering, > uevent "remove path3" would merge uevent "remove path2" and uevent > "remove path1". Uevent "add path2" would merge "add path1". > The result is that we get two merged uevents: > 1) add path2, path1 > 2) remove path3, path2, path1 > Then we process the merged uevents from the earlier to later, We try > to ”add > path2 path1“, and we would create or reload a map device with path1 > and path2. > Next we process ” remove path3, path2, path1“, so path1, path2 and > path3 are > all removed from the map device, this is wrong, the correct result > is that the path1 > and path2 should be still in the map device. I don't understand that. This would mean that you'd re-order "remove path1 | add path1" into "add path1| remove path1", and the same for path2. That may obviously never happen. Your "stop merging" logic forbids it, and that's fine for me for now. Regards Martin -- Dr. Martin Wilck <mwilck@xxxxxxxx>, Tel. +49 (0)911 74053 2107 SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton HRB 21284 (AG Nürnberg) -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
