On Mon, Jul 29, 2024 at 4:50 AM Christian Brauner <brauner@xxxxxxxxxx> wrote: On Mon, Jul 29, 2024 at 12:33 PM Steve French <smfrench@xxxxxxxxx> wrote: > > The first step should be to identify what exactly keeps your mount busy > > in generic/044 and generic/043. > > That is a little tricky to debug (AFAIK no easy way to tell exactly which > reference is preventing the VFS from proceeding with the umount and > calling kill_sb). My best guess is something related to deferred close > (cached network file handles) that had a brief refcount on > something being checked by umount, but when I experimented with > deferred close settings that did not seem to affect the problem so > looking for other possible causes. > > I just did a quick experiment by adding a 1 second wait inside umount > and confirmed that that does fix it for those two tests when mounted to Samba, > but not clear why the slight delay in umount helps as there is no pending > network traffic at that point. I did some more experimentation and it looks like the umount problem with those two xfstests to Samba is related to IOC_SHUTDOWN. If I return EOPNOTSUPP on IOC_SHUTDOWN then the 1 second delay in umount is not necessary - so something that happens after IOC_SHUTDOWN races with umount (thus the 1 second delay that I tried as a quick experiment fixes it indirectly) in this testcase (although apparently this race between IOC_SHUTDOWN and umount is not an issue to some other servers but is reproducible to Samba and ksmbd (at least in some easy to setup configurations) -- Thanks, Steve
