Allow READ using write delegation stateid granted on OPENs with
OPEN4_SHARE_ACCESS_WRITE only, to accommodate clients whose WRITE
implementation may unavoidably do (e.g., due to buffer cache
constraints).
When the server offers a write delegation for an OPEN with
OPEN4_SHARE_ACCESS_WRITE, the file access mode, the nfs4_file
and nfs4_ol_stateid are upgraded as if the OPEN was sent with
OPEN4_SHARE_ACCESS_BOTH.
When this delegation is returned or revoked, the corresponding open
stateid is looked up and if it's found then the file access mode,
the nfs4_file and nfs4_ol_stateid are downgraded to remove the read
access.
Signed-off-by: Dai Ngo <dai.ngo@xxxxxxxxxx>
---
fs/nfsd/nfs4state.c | 62 +++++++++++++++++++++++++++++++++++++++++++++
fs/nfsd/state.h | 2 ++
2 files changed, 64 insertions(+)
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index b533225e57cf..0c14f902c54c 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -6126,6 +6126,51 @@ nfs4_delegation_stat(struct nfs4_delegation *dp, struct svc_fh *currentfh,
return rc == 0;
}
+/*
+ * Upgrade file access mode to include FMODE_READ. This is called only when
+ * a write delegation is granted for an OPEN with OPEN4_SHARE_ACCESS_WRITE.
+ */
+static void
+nfs4_upgrade_rdwr_file_access(struct nfs4_ol_stateid *stp)
+{
+ struct nfs4_file *fp = stp->st_stid.sc_file;
+ struct nfsd_file *nflp;
+ struct file *file;
+
+ spin_lock(&fp->fi_lock);
+ nflp = fp->fi_fds[O_WRONLY];
+ file = nflp->nf_file;
+ file->f_mode |= FMODE_READ;
+ swap(fp->fi_fds[O_RDWR], fp->fi_fds[O_WRONLY]);
+ clear_access(NFS4_SHARE_ACCESS_WRITE, stp);
+ set_access(NFS4_SHARE_ACCESS_BOTH, stp);
+ __nfs4_file_get_access(fp, NFS4_SHARE_ACCESS_READ); /* incr fi_access[O_RDONLY] */
+ spin_unlock(&fp->fi_lock);
+}
+
+/*
+ * Downgrade file access mode to remove FMODE_READ. This is called when
+ * a write delegation, granted for an OPEN with OPEN4_SHARE_ACCESS_WRITE,
+ * is returned.
+ */
+static void
+nfs4_downgrade_wronly_file_access(struct nfs4_ol_stateid *stp)
+{
+ struct nfs4_file *fp = stp->st_stid.sc_file;
+ struct nfsd_file *nflp;
+ struct file *file;
+
+ spin_lock(&fp->fi_lock);
+ nflp = fp->fi_fds[O_RDWR];
+ file = nflp->nf_file;
+ file->f_mode &= ~FMODE_READ;
+ swap(fp->fi_fds[O_WRONLY], fp->fi_fds[O_RDWR]);
+ clear_access(NFS4_SHARE_ACCESS_BOTH, stp);
+ set_access(NFS4_SHARE_ACCESS_WRITE, stp);
+ spin_unlock(&fp->fi_lock);
+ nfs4_file_put_access(fp, NFS4_SHARE_ACCESS_READ); /* decr. fi_access[O_RDONLY] */
+}
+
/*
* The Linux NFS server does not offer write delegations to NFSv4.0
* clients in order to avoid conflicts between write delegations and
@@ -6207,6 +6252,11 @@ nfs4_open_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
dp->dl_cb_fattr.ncf_cur_fsize = stat.size;
dp->dl_cb_fattr.ncf_initial_cinfo = nfsd4_change_attribute(&stat);
trace_nfsd_deleg_write(&dp->dl_stid.sc_stateid);
+
+ if ((open->op_share_access & NFS4_SHARE_ACCESS_BOTH) == NFS4_SHARE_ACCESS_WRITE) {
+ dp->dl_stateid = stp->st_stid.sc_stateid;
+ nfs4_upgrade_rdwr_file_access(stp);
+ }
} else {
open->op_delegate_type = deleg_ts ? OPEN_DELEGATE_READ_ATTRS_DELEG :
OPEN_DELEGATE_READ;
@@ -7710,6 +7760,8 @@ nfsd4_delegreturn(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
struct nfs4_stid *s;
__be32 status;
struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
+ struct nfs4_ol_stateid *stp;
+ struct nfs4_stid *stid;
if ((status = fh_verify(rqstp, &cstate->current_fh, S_IFREG, 0)))
return status;
@@ -7724,6 +7776,16 @@ nfsd4_delegreturn(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
trace_nfsd_deleg_return(stateid);
destroy_delegation(dp);
+
+ if (dp->dl_stateid.si_generation && dp->dl_stateid.si_opaque.so_id) {
+ if (!nfsd4_lookup_stateid(cstate, &dp->dl_stateid,
+ SC_TYPE_OPEN, 0, &stid, nn)) {
+ stp = openlockstateid(stid);
+ nfs4_downgrade_wronly_file_access(stp);
+ nfs4_put_stid(stid);
+ }
+ }
+
smp_mb__after_atomic();
wake_up_var(d_inode(cstate->current_fh.fh_dentry));
put_stateid:
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index 74d2d7b42676..3f2f1b92db66 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -207,6 +207,8 @@ struct nfs4_delegation {
/* for CB_GETATTR */
struct nfs4_cb_fattr dl_cb_fattr;
+
+ stateid_t dl_stateid; /* open stateid */
};
static inline bool deleg_is_read(u32 dl_type)
--
2.43.5
