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>
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index bd67f4d..2a2d9b0 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -692,6 +692,17 @@
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),