nfsd4: disable zero-copy on non-final read ops

To ensure ordering of read data with any following operations, turn off
zero copy if the read is not the final operation in the compound.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

3 files changed, 19 insertions, 8 deletions

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index bd67f4d6dfc6..2a2d9b06a413 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -692,6 +692,17 @@ nfsd4_read(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
         if (read->rd_offset >= OFFSET_MAX)
                 return nfserr_inval;
 
+        /*
+         * If we do a zero copy read, then a client will see read data
+         * that reflects the state of the file *after* performing the
+         * following compound.
+         *
+         * To ensure proper ordering, we therefore turn off zero copy if
+         * the client wants us to do more in this compound:
+         */
+        if (!nfsd4_last_compound_op(rqstp))
+                rqstp->rq_splice_ok = false;
+
         nfs4_lock_state();
         /* check stateid */
         if ((status = nfs4_preprocess_stateid_op(SVC_NET(rqstp),
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 8e2555112966..8e127b39d323 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1855,14 +1855,6 @@ out_free_session:
         goto out;
 }
 
-static bool nfsd4_last_compound_op(struct svc_rqst *rqstp)
-{
-        struct nfsd4_compoundres *resp = rqstp->rq_resp;
-        struct nfsd4_compoundargs *argp = rqstp->rq_argp;
-
-        return argp->opcnt == resp->opcnt;
-}
-
 static __be32 nfsd4_map_bcts_dir(u32 *dir)
 {
         switch (*dir) {
diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index 331f8a3277ab..0889bfb43dc9 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -528,6 +528,14 @@ static inline bool nfsd4_not_cached(struct nfsd4_compoundres *resp)
                 || nfsd4_is_solo_sequence(resp);
 }
 
+static inline bool nfsd4_last_compound_op(struct svc_rqst *rqstp)
+{
+        struct nfsd4_compoundres *resp = rqstp->rq_resp;
+        struct nfsd4_compoundargs *argp = rqstp->rq_argp;
+
+        return argp->opcnt == resp->opcnt;
+}
+
 #define NFS4_SVC_XDRSIZE                sizeof(struct nfsd4_compoundargs)
 
 static inline void