| Message ID | 8760v1unlw.fsf@notabene.neil.brown.name (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 28/04/16 22:59, NeilBrown wrote: > > The dependencies on rpcbind have been changed a few times and I think > they are still wrong. So I'll go into some detail to justify this change. > > Firstly: rpcbind.target rpcbind.socket or rpcbind.service? > > The systemd documentation talks about targets as "synchronization > points" and likens them to SysV init run levels. Run levels are about > ordering but not dependencies. > > The systemd.special man page describes rpcbind.target as intended > explicitly for ordering sysvinit scripts, with "After=" dependencies. > > So while I think it is valid to use rpcbind.target for ordering > (before/after) it shouldn't be used for dependencies (Wants/Requires). > The rpcbind.target file included in systemd does not "Require" the > actual service, so requiring rpcbind.target itself is pointless. > > I think we shouldn't use rpcbind.target at all. Leave it for sysvinit > synchronization. > > So: .socket or .service? > > I think nfs only needs the socket to be active. On first connection > the service will be started. But nfs does not need to wait for the > service to start, only the socket. So I think we should exclusively > use rpcbind.socket. > > Next: Wants or Requires. > > rpc.statd definitely Requires rpcbind. It needs to register to be > useful, and without rpcbind it cannot register. > > nfs-server does not necesarily require rpcbind. Specifically if > configured for NFSv4 only, nfs-server will work quite happily without > rpcbind. > > Someone with an NFSv4 only setup who wants rpcbind to not run can use > systemctl mask rpcbind.socket > to ensure it never runs. > So nfs-server should only "Wants: rpcbind.socket". > I think > Commit: 4fabfcd08206 ("systemd: Decouple the starting and stopping of rpcbind/nfs-server") > should have changed "Requires" to "Wants" rather than "server" to "target" > to fix the dependency problem. > > Finally: After? > > It only makes sense to declare an ordering relation as "After:" > something that will actually be started. If "foo.service" is not part > of the systemd transaction, then "After: foo.service" has no effect. > So having: > Requires: rpcbind.target > After: rpcbind.socket > > doesn't make much sense unless there is some relationship between > rpcbind.target and rpcbind.socket, and there is no general guarantee > of that (though what individual distros do, I don't know). > So the "After" should match the "Wants" or "Requires". > > It might make sense to > Requires: rpcbind.socket > After: rpcbind.target > > as it is reasonable to assume that rpcbind.target will be ordered with > rpcbind.socket, but as we can use rpcbind.socket explictly, that is > clearer. > > So my conclusion is that nfs-server should: > Wants: rpcbind.socket > After: rpcbind.socket > > and rpc-statd should > Requires: rpcbind.socket > After: rpcbind.socket > > which is what this patch puts into effect. Thanks for making sense of this.... Committed... steved. > > Signed-off-by: NeilBrown <neilb@suse.com> > > diff --git a/systemd/nfs-server.service b/systemd/nfs-server.service > index 317e5d689767..2ccdc6344cd5 100644 > --- a/systemd/nfs-server.service > +++ b/systemd/nfs-server.service > @@ -1,13 +1,14 @@ > [Unit] > Description=NFS server and services > DefaultDependencies=no > -Requires= network.target proc-fs-nfsd.mount rpcbind.target > +Requires= network.target proc-fs-nfsd.mount > Requires= nfs-mountd.service > +Wants=rpcbind.socket > Wants=rpc-statd.service nfs-idmapd.service > Wants=rpc-statd-notify.service > > After= local-fs.target > -After= network.target proc-fs-nfsd.mount rpcbind.service nfs-mountd.service > +After= network.target proc-fs-nfsd.mount rpcbind.socket nfs-mountd.service > After= nfs-idmapd.service rpc-statd.service > Before= rpc-statd-notify.service > > diff --git a/systemd/rpc-statd.service b/systemd/rpc-statd.service > index f16ea425dc77..a02f5c41a424 100644 > --- a/systemd/rpc-statd.service > +++ b/systemd/rpc-statd.service > @@ -2,8 +2,8 @@ > Description=NFS status monitor for NFSv2/3 locking. > DefaultDependencies=no > Conflicts=umount.target > -Requires=nss-lookup.target rpcbind.target > -After=network.target nss-lookup.target rpcbind.service > +Requires=nss-lookup.target rpcbind.socket > +After=network.target nss-lookup.target rpcbind.socket > > PartOf=nfs-utils.service > > -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/systemd/nfs-server.service b/systemd/nfs-server.service index 317e5d689767..2ccdc6344cd5 100644 --- a/systemd/nfs-server.service +++ b/systemd/nfs-server.service @@ -1,13 +1,14 @@ [Unit] Description=NFS server and services DefaultDependencies=no -Requires= network.target proc-fs-nfsd.mount rpcbind.target +Requires= network.target proc-fs-nfsd.mount Requires= nfs-mountd.service +Wants=rpcbind.socket Wants=rpc-statd.service nfs-idmapd.service Wants=rpc-statd-notify.service After= local-fs.target -After= network.target proc-fs-nfsd.mount rpcbind.service nfs-mountd.service +After= network.target proc-fs-nfsd.mount rpcbind.socket nfs-mountd.service After= nfs-idmapd.service rpc-statd.service Before= rpc-statd-notify.service diff --git a/systemd/rpc-statd.service b/systemd/rpc-statd.service index f16ea425dc77..a02f5c41a424 100644 --- a/systemd/rpc-statd.service +++ b/systemd/rpc-statd.service @@ -2,8 +2,8 @@ Description=NFS status monitor for NFSv2/3 locking. DefaultDependencies=no Conflicts=umount.target -Requires=nss-lookup.target rpcbind.target -After=network.target nss-lookup.target rpcbind.service +Requires=nss-lookup.target rpcbind.socket +After=network.target nss-lookup.target rpcbind.socket PartOf=nfs-utils.service
The dependencies on rpcbind have been changed a few times and I think they are still wrong. So I'll go into some detail to justify this change. Firstly: rpcbind.target rpcbind.socket or rpcbind.service? The systemd documentation talks about targets as "synchronization points" and likens them to SysV init run levels. Run levels are about ordering but not dependencies. The systemd.special man page describes rpcbind.target as intended explicitly for ordering sysvinit scripts, with "After=" dependencies. So while I think it is valid to use rpcbind.target for ordering (before/after) it shouldn't be used for dependencies (Wants/Requires). The rpcbind.target file included in systemd does not "Require" the actual service, so requiring rpcbind.target itself is pointless. I think we shouldn't use rpcbind.target at all. Leave it for sysvinit synchronization. So: .socket or .service? I think nfs only needs the socket to be active. On first connection the service will be started. But nfs does not need to wait for the service to start, only the socket. So I think we should exclusively use rpcbind.socket. Next: Wants or Requires. rpc.statd definitely Requires rpcbind. It needs to register to be useful, and without rpcbind it cannot register. nfs-server does not necesarily require rpcbind. Specifically if configured for NFSv4 only, nfs-server will work quite happily without rpcbind. Someone with an NFSv4 only setup who wants rpcbind to not run can use systemctl mask rpcbind.socket to ensure it never runs. So nfs-server should only "Wants: rpcbind.socket". I think Commit: 4fabfcd08206 ("systemd: Decouple the starting and stopping of rpcbind/nfs-server") should have changed "Requires" to "Wants" rather than "server" to "target" to fix the dependency problem. Finally: After? It only makes sense to declare an ordering relation as "After:" something that will actually be started. If "foo.service" is not part of the systemd transaction, then "After: foo.service" has no effect. So having: Requires: rpcbind.target After: rpcbind.socket doesn't make much sense unless there is some relationship between rpcbind.target and rpcbind.socket, and there is no general guarantee of that (though what individual distros do, I don't know). So the "After" should match the "Wants" or "Requires". It might make sense to Requires: rpcbind.socket After: rpcbind.target as it is reasonable to assume that rpcbind.target will be ordered with rpcbind.socket, but as we can use rpcbind.socket explictly, that is clearer. So my conclusion is that nfs-server should: Wants: rpcbind.socket After: rpcbind.socket and rpc-statd should Requires: rpcbind.socket After: rpcbind.socket which is what this patch puts into effect. Signed-off-by: NeilBrown <neilb@suse.com>