diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
index 94cc324b591f..7d45401ee5b1 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -639,9 +639,12 @@ ff_layout_alloc_lseg(struct pnfs_layout_hdr *lh,
 	if (!p)
 		goto out_sort_mirrors;
 	fls->flags = be32_to_cpup(p);
-	if (fls->flags & FF_FLAGS_NO_IO_THRU_MDS)
+	if (fls->flags & FF_FLAGS_NO_IO_THRU_MDS) {
 		set_bit(NFS4_FF_HDR_NO_IO_THRU_MDS,
 			&FF_LAYOUT_FROM_HDR(lh)->flags);
+		/* Outlives this layout hdr; see NFS_INO_NO_IO_THRU_MDS */
+		nfs_set_no_io_thru_mds(lh->plh_inode);
+	}
 
 	p = xdr_inline_decode(&stream, 4);
 	if (!p)
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 48f7c0e25da1..959edbc9add2 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -546,6 +546,35 @@ static inline bool nfs_file_io_is_buffered(struct nfs_inode *nfsi)
 	return test_bit(NFS_INO_ODIRECT, &nfsi->flags) == 0;
 }
 
+/*
+ * Module-private nfs_inode->flags bit (not in <linux/nfs_fs.h>, so no
+ * exported layout changes): set, and never cleared for the life of the
+ * in-core inode, once a layout driver has seen the server forbid I/O
+ * through the MDS for this file (flexfiles sets it from
+ * FF_FLAGS_NO_IO_THRU_MDS in ff_layout_alloc_lseg()).  The RFC 5661
+ * mdsthreshold hint must not be acted on for such a file, since the only
+ * thing pnfs_within_mdsthreshold() can ask for is the one thing the
+ * layout forbids.  Servers are assumed to be consistent in their
+ * no-fallback policy per file, the same assumption
+ * ff_layout_hdr_no_fallback_to_mds() already makes; if one were not, the
+ * only effect is that its mdsthreshold hint - a SHOULD - stops being
+ * honored for an inode that is already in core.
+ */
+#define NFS_INO_NO_IO_THRU_MDS	(30)
+
+static inline void nfs_set_no_io_thru_mds(struct inode *inode)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+
+	if (!test_bit(NFS_INO_NO_IO_THRU_MDS, &nfsi->flags))
+		set_bit(NFS_INO_NO_IO_THRU_MDS, &nfsi->flags);
+}
+
+static inline bool nfs_no_io_thru_mds(struct inode *inode)
+{
+	return test_bit(NFS_INO_NO_IO_THRU_MDS, &NFS_I(inode)->flags);
+}
+
 /* Must be called with exclusively locked inode->i_rwsem */
 static inline void nfs_file_block_o_direct(struct nfs_inode *nfsi)
 {
diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 93a0852e1e8a..a057a06318c7 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -2019,7 +2019,9 @@ pnfs_find_lseg(struct pnfs_layout_hdr *lo,
  * is set to IOMODE_READ for a READ request, and set to IOMODE_RW for a
  * WRITE request.
  *
- * A return of true means use MDS I/O.
+ * A return of true means use MDS I/O, so for a file whose layout forbids
+ * that (see NFS_INO_NO_IO_THRU_MDS) the hint is not evaluated at all:
+ * there is no answer it could give that this client may act on.
  *
  * From rfc 5661:
  * If a file's size is smaller than the file size threshold, data accesses
@@ -2040,6 +2042,14 @@ static bool pnfs_within_mdsthreshold(struct nfs_open_context *ctx,
 	if (t == NULL)
 		return ret;
 
+	/*
+	 * The server has told a layout driver that this file's I/O may not
+	 * go through the MDS (flexfiles FF_FLAGS_NO_IO_THRU_MDS).  Honor
+	 * that over its own mdsthreshold hint.
+	 */
+	if (nfs_no_io_thru_mds(ino))
+		return ret;
+
 	dprintk("%s bm=0x%x rd_sz=%llu wr_sz=%llu rd_io=%llu wr_io=%llu\n",
 		__func__, t->bm, t->rd_sz, t->wr_sz, t->rd_io_sz, t->wr_io_sz);