On Wed, Aug 02, 2023 at 08:26:15AM +1000, NeilBrown wrote: > On Tue, 01 Aug 2023, Jeff Layton wrote: > > I noticed that xfstests generic/001 was failing against linux-next nfsd. > > > > The client would request a OPEN4_SHARE_ACCESS_WRITE open, and the server > > would hand out a write delegation. The client would then try to use that > > write delegation as the source stateid in a COPY or CLONE operation, and > > the server would respond with NFS4ERR_STALE. > > > > The problem is that the struct file associated with the delegation does > > not necessarily have read permissions. It's handing out a write > > delegation on what is effectively an O_WRONLY open. RFC 8881 states: > > > > "An OPEN_DELEGATE_WRITE delegation allows the client to handle, on its > > own, all opens." > > > > Given that the client didn't request any read permissions, and that nfsd > > didn't check for any, it seems wrong to give out a write delegation. > > > > Only hand out a write delegation if we have a O_RDWR descriptor > > available. If it fails to find an appropriate write descriptor, go > > ahead and try for a read delegation if NFS4_SHARE_ACCESS_READ was > > requested. > > > > This fixes xfstest generic/001. > > > > Closes: https://bugzilla.linux-nfs.org/show_bug.cgi?id=412 > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> > > --- > > Changes in v2: > > - Rework the logic when finding struct file for the delegation. The > > earlier patch might still have attached a O_WRONLY file to the deleg > > in some cases, and could still have handed out a write delegation on > > an O_WRONLY OPEN request in some cases. > > --- > > fs/nfsd/nfs4state.c | 29 ++++++++++++++++++----------- > > 1 file changed, 18 insertions(+), 11 deletions(-) > > > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > > index ef7118ebee00..e79d82fd05e7 100644 > > --- a/fs/nfsd/nfs4state.c > > +++ b/fs/nfsd/nfs4state.c > > @@ -5449,7 +5449,7 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp, > > struct nfs4_file *fp = stp->st_stid.sc_file; > > struct nfs4_clnt_odstate *odstate = stp->st_clnt_odstate; > > struct nfs4_delegation *dp; > > - struct nfsd_file *nf; > > + struct nfsd_file *nf = NULL; > > struct file_lock *fl; > > u32 dl_type; > > > > @@ -5461,21 +5461,28 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp, > > if (fp->fi_had_conflict) > > return ERR_PTR(-EAGAIN); > > > > - if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE) { > > - nf = find_writeable_file(fp); > > + /* > > + * Try for a write delegation first. We need an O_RDWR file > > + * since a write delegation allows the client to perform any open > > + * from its cache. > > + */ > > + if ((open->op_share_access & NFS4_SHARE_ACCESS_BOTH) == NFS4_SHARE_ACCESS_BOTH) { > > + nf = nfsd_file_get(fp->fi_fds[O_RDWR]); > > This doesn't take fp->fi_lock before accessing ->fi_fds[], while the > find_readable_file() call below does. Note that the code it replaces (find_writeable_file) takes the fi_lock, so that seems like an important omission. I noticed this earlier, but I was anxious to test whether this fix is on the right path. So far, NFSv4.2 behavior seems much improved. And, I like the new comments. > This inconsistency suggests a bug? > > Maybe the provided API is awkward. Should we have > find_suitable_file() and find_suitable_file_locked() > that gets passed an nfs4_file and an O_MODE? > It tries the given mode, then O_RDWR > > NeilBrown > > > > dl_type = NFS4_OPEN_DELEGATE_WRITE; > > - } else { > > + } > > + > > + /* > > + * If the file is being opened O_RDONLY or we couldn't get a O_RDWR > > + * file for some reason, then try for a read deleg instead. > > + */ > > + if (!nf && (open->op_share_access & NFS4_SHARE_ACCESS_READ)) { > > nf = find_readable_file(fp); > > dl_type = NFS4_OPEN_DELEGATE_READ; > > } > > - if (!nf) { > > - /* > > - * We probably could attempt another open and get a read > > - * delegation, but for now, don't bother until the > > - * client actually sends us one. > > - */ > > + > > + if (!nf) > > return ERR_PTR(-EAGAIN); > > - } > > + > > spin_lock(&state_lock); > > spin_lock(&fp->fi_lock); > > if (nfs4_delegation_exists(clp, fp)) > > > > --- > > base-commit: a734662572708cf062e974f659ae50c24fc1ad17 > > change-id: 20230731-wdeleg-bbdb6b25a3c6 > > > > Best regards, > > -- > > Jeff Layton <jlayton@xxxxxxxxxx> > > > > > -- Chuck Lever
