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>

1 files changed, 11 insertions, 0 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),