On Wed, Aug 02, 2023 at 02:53:00PM -0400, 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 v3: > - add find_rw_file helper to ensure spinlock is taken appropriately > - refine comments over conditionals > - Link to v2: https://lore.kernel.org/r/20230801-wdeleg-v2-1-20c14252bab4@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 | 48 +++++++++++++++++++++++++++++++++++++----------- > 1 file changed, 37 insertions(+), 11 deletions(-) > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > index ef7118ebee00..c551784d108a 100644 > --- a/fs/nfsd/nfs4state.c > +++ b/fs/nfsd/nfs4state.c > @@ -649,6 +649,18 @@ find_readable_file(struct nfs4_file *f) > return ret; > } > > +static struct nfsd_file * > +find_rw_file(struct nfs4_file *f) > +{ > + struct nfsd_file *ret; > + > + spin_lock(&f->fi_lock); > + ret = nfsd_file_get(f->fi_fds[O_RDWR]); > + spin_unlock(&f->fi_lock); > + > + return ret; > +} > + > struct nfsd_file * > find_any_file(struct nfs4_file *f) > { > @@ -5449,7 +5461,7 @@ 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 +5473,35 @@ 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. RFC8881 section 10.4 says: > + * > + * "An OPEN_DELEGATE_WRITE delegation allows the client to handle, > + * on its own, all opens." > + * > + * Furthermore the client can use a write delegationf or most read > + * operations as well, so we require a O_RDWR file here. > + * > + * Only a write delegation in the case of a BOTH open, and ensure > + * we get the O_RDWR descriptor. > + */ > + if ((open->op_share_access & NFS4_SHARE_ACCESS_BOTH) == NFS4_SHARE_ACCESS_BOTH) { > + nf = find_rw_file(fp); > 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> > Tested and applied to nfsd-next as a separate patch. I intend to squash it into commit 68a593f24a35 ("NFSD: Enable write delegation support") in a few days. -- Chuck Lever
