On Tue, 10 Apr 2012 15:44:42 +0400 Stanislav Kinsbursky <skinsbursky@xxxxxxxxxxxxx> wrote: > 03.04.2012 16:14, Jeff Layton пишет: > > The main reason for the grace period is to prevent the server from > > allowing an operation that might otherwise be denied once the client has > > reclaimed all of its stateful objects. > > > > Currently, the grace period handling in the nfsd/lockd server code is > > very simple. When the lock managers start, they stick an entry on a list > > and set a timer. When the timers pop, then they remove the entry from > > the list. The locks_in_grace check just looks to see if the list is > > empty. If it is, then the grace period is considered to be over. > > > > This is insufficient for a clustered filesystem that is being served > > from multiple nodes at the same time. In such a configuration, the grace > > period must be coordinated in some fashion, or else one node might hand > > out stateful objects that conflict with those that have not yet been > > reclaimed. > > > > This patch paves the way for fixing this by adding a new export > > operation called locks_in_grace that takes a superblock argument. The > > existing locks_in_grace function is renamed to generic_locks_in_grace, > > and a new locks_in_grace function that takes a superblock arg is added. > > If a filesystem does not have a locks_in_grace export operation then the > > generic version will be used. > > > > Care has also been taken to reorder calls such that locks_in_grace is > > called last in compound conditional statements. Handling this for > > clustered filesystems may involve upcalls, so we don't want to call it > > unnecessarily. > > > > For now, this patch is just an RFC as I do not yet have any code that > > overrides this function and am still specing out what that code should > > look like. > > > > Oops, I've noticed your patch after I replied in "Grace period" thread. > This patch looks good, but doesn't explain, how this per-filesystem logic will > work in case of sharing non-nested subdirectories with the same superblock. > This is a valid situation. But how to handle grace period in this case? It's a valid situation but one that's discouraged. > Also, don't we need to prevent of exporting the same file system parts but > different servers always, but not only for grace period? > -- Jeff Layton <jlayton@xxxxxxxxxx> -- 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
