v4.19.13 snapshot.
diff --git a/fs/nfsd/flexfilelayout.c b/fs/nfsd/flexfilelayout.c
new file mode 100644
index 0000000..db7ef07
--- /dev/null
+++ b/fs/nfsd/flexfilelayout.c
@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2016 Tom Haynes <loghyr@primarydata.com>
+ *
+ * The following implements a super-simple flex-file server
+ * where the NFSv4.1 mds is also the ds. And the storage is
+ * the same. I.e., writing to the mds via a NFSv4.1 WRITE
+ * goes to the same location as the NFSv3 WRITE.
+ */
+#include <linux/slab.h>
+
+#include <linux/nfsd/debug.h>
+
+#include <linux/sunrpc/addr.h>
+
+#include "flexfilelayoutxdr.h"
+#include "pnfs.h"
+
+#define NFSDDBG_FACILITY NFSDDBG_PNFS
+
+static __be32
+nfsd4_ff_proc_layoutget(struct inode *inode, const struct svc_fh *fhp,
+ struct nfsd4_layoutget *args)
+{
+ struct nfsd4_layout_seg *seg = &args->lg_seg;
+ u32 device_generation = 0;
+ int error;
+ uid_t u;
+
+ struct pnfs_ff_layout *fl;
+
+ /*
+ * The super simple flex file server has 1 mirror, 1 data server,
+ * and 1 file handle. So instead of 4 allocs, do 1 for now.
+ * Zero it out for the stateid - don't want junk in there!
+ */
+ error = -ENOMEM;
+ fl = kzalloc(sizeof(*fl), GFP_KERNEL);
+ if (!fl)
+ goto out_error;
+ args->lg_content = fl;
+
+ /*
+ * Avoid layout commit, try to force the I/O to the DS,
+ * and for fun, cause all IOMODE_RW layout segments to
+ * effectively be WRITE only.
+ */
+ fl->flags = FF_FLAGS_NO_LAYOUTCOMMIT | FF_FLAGS_NO_IO_THRU_MDS |
+ FF_FLAGS_NO_READ_IO;
+
+ /* Do not allow a IOMODE_READ segment to have write pemissions */
+ if (seg->iomode == IOMODE_READ) {
+ u = from_kuid(&init_user_ns, inode->i_uid) + 1;
+ fl->uid = make_kuid(&init_user_ns, u);
+ } else
+ fl->uid = inode->i_uid;
+ fl->gid = inode->i_gid;
+
+ error = nfsd4_set_deviceid(&fl->deviceid, fhp, device_generation);
+ if (error)
+ goto out_error;
+
+ fl->fh.size = fhp->fh_handle.fh_size;
+ memcpy(fl->fh.data, &fhp->fh_handle.fh_base, fl->fh.size);
+
+ /* Give whole file layout segments */
+ seg->offset = 0;
+ seg->length = NFS4_MAX_UINT64;
+
+ dprintk("GET: 0x%llx:0x%llx %d\n", seg->offset, seg->length,
+ seg->iomode);
+ return 0;
+
+out_error:
+ seg->length = 0;
+ return nfserrno(error);
+}
+
+static __be32
+nfsd4_ff_proc_getdeviceinfo(struct super_block *sb, struct svc_rqst *rqstp,
+ struct nfs4_client *clp, struct nfsd4_getdeviceinfo *gdp)
+{
+ struct pnfs_ff_device_addr *da;
+
+ u16 port;
+ char addr[INET6_ADDRSTRLEN];
+
+ da = kzalloc(sizeof(struct pnfs_ff_device_addr), GFP_KERNEL);
+ if (!da)
+ return nfserrno(-ENOMEM);
+
+ gdp->gd_device = da;
+
+ da->version = 3;
+ da->minor_version = 0;
+
+ da->rsize = svc_max_payload(rqstp);
+ da->wsize = da->rsize;
+
+ rpc_ntop((struct sockaddr *)&rqstp->rq_daddr,
+ addr, INET6_ADDRSTRLEN);
+ if (rqstp->rq_daddr.ss_family == AF_INET) {
+ struct sockaddr_in *sin;
+
+ sin = (struct sockaddr_in *)&rqstp->rq_daddr;
+ port = ntohs(sin->sin_port);
+ snprintf(da->netaddr.netid, FF_NETID_LEN + 1, "tcp");
+ da->netaddr.netid_len = 3;
+ } else {
+ struct sockaddr_in6 *sin6;
+
+ sin6 = (struct sockaddr_in6 *)&rqstp->rq_daddr;
+ port = ntohs(sin6->sin6_port);
+ snprintf(da->netaddr.netid, FF_NETID_LEN + 1, "tcp6");
+ da->netaddr.netid_len = 4;
+ }
+
+ da->netaddr.addr_len =
+ snprintf(da->netaddr.addr, FF_ADDR_LEN + 1,
+ "%s.%hhu.%hhu", addr, port >> 8, port & 0xff);
+
+ da->tightly_coupled = false;
+
+ return 0;
+}
+
+const struct nfsd4_layout_ops ff_layout_ops = {
+ .notify_types =
+ NOTIFY_DEVICEID4_DELETE | NOTIFY_DEVICEID4_CHANGE,
+ .disable_recalls = true,
+ .proc_getdeviceinfo = nfsd4_ff_proc_getdeviceinfo,
+ .encode_getdeviceinfo = nfsd4_ff_encode_getdeviceinfo,
+ .proc_layoutget = nfsd4_ff_proc_layoutget,
+ .encode_layoutget = nfsd4_ff_encode_layoutget,
+};