diff --git a/fs/nfs/flexfilelayout/flexfilelayoutdev.c b/fs/nfs/flexfilelayout/flexfilelayoutdev.c
new file mode 100644
index 0000000..3bbb16b
--- /dev/null
+++ b/fs/nfs/flexfilelayout/flexfilelayoutdev.c
@@ -0,0 +1,552 @@
+/*
+ * Device operations for the pnfs nfs4 file layout driver.
+ *
+ * Copyright (c) 2014, Primary Data, Inc. All rights reserved.
+ *
+ * Tao Peng <bergwolf@primarydata.com>
+ */
+
+#include <linux/nfs_fs.h>
+#include <linux/vmalloc.h>
+#include <linux/module.h>
+#include <linux/sunrpc/addr.h>
+
+#include "../internal.h"
+#include "../nfs4session.h"
+#include "flexfilelayout.h"
+
+#define NFSDBG_FACILITY		NFSDBG_PNFS_LD
+
+static unsigned int dataserver_timeo = NFS4_DEF_DS_TIMEO;
+static unsigned int dataserver_retrans = NFS4_DEF_DS_RETRANS;
+
+void nfs4_ff_layout_put_deviceid(struct nfs4_ff_layout_ds *mirror_ds)
+{
+	if (mirror_ds)
+		nfs4_put_deviceid_node(&mirror_ds->id_node);
+}
+
+void nfs4_ff_layout_free_deviceid(struct nfs4_ff_layout_ds *mirror_ds)
+{
+	nfs4_print_deviceid(&mirror_ds->id_node.deviceid);
+	nfs4_pnfs_ds_put(mirror_ds->ds);
+	kfree(mirror_ds);
+}
+
+/* Decode opaque device data and construct new_ds using it */
+struct nfs4_ff_layout_ds *
+nfs4_ff_alloc_deviceid_node(struct nfs_server *server, struct pnfs_device *pdev,
+			    gfp_t gfp_flags)
+{
+	struct xdr_stream stream;
+	struct xdr_buf buf;
+	struct page *scratch;
+	struct list_head dsaddrs;
+	struct nfs4_pnfs_ds_addr *da;
+	struct nfs4_ff_layout_ds *new_ds = NULL;
+	struct nfs4_ff_ds_version *ds_versions = NULL;
+	u32 mp_count;
+	u32 version_count;
+	__be32 *p;
+	int i, ret = -ENOMEM;
+
+	/* set up xdr stream */
+	scratch = alloc_page(gfp_flags);
+	if (!scratch)
+		goto out_err;
+
+	new_ds = kzalloc(sizeof(struct nfs4_ff_layout_ds), gfp_flags);
+	if (!new_ds)
+		goto out_scratch;
+
+	nfs4_init_deviceid_node(&new_ds->id_node,
+				server,
+				&pdev->dev_id);
+	INIT_LIST_HEAD(&dsaddrs);
+
+	xdr_init_decode_pages(&stream, &buf, pdev->pages, pdev->pglen);
+	xdr_set_scratch_buffer(&stream, page_address(scratch), PAGE_SIZE);
+
+	/* multipath count */
+	p = xdr_inline_decode(&stream, 4);
+	if (unlikely(!p))
+		goto out_err_drain_dsaddrs;
+	mp_count = be32_to_cpup(p);
+	dprintk("%s: multipath ds count %d\n", __func__, mp_count);
+
+	for (i = 0; i < mp_count; i++) {
+		/* multipath ds */
+		da = nfs4_decode_mp_ds_addr(server->nfs_client->cl_net,
+					    &stream, gfp_flags);
+		if (da)
+			list_add_tail(&da->da_node, &dsaddrs);
+	}
+	if (list_empty(&dsaddrs)) {
+		dprintk("%s: no suitable DS addresses found\n",
+			__func__);
+		ret = -ENOMEDIUM;
+		goto out_err_drain_dsaddrs;
+	}
+
+	/* version count */
+	p = xdr_inline_decode(&stream, 4);
+	if (unlikely(!p))
+		goto out_err_drain_dsaddrs;
+	version_count = be32_to_cpup(p);
+	dprintk("%s: version count %d\n", __func__, version_count);
+
+	ds_versions = kzalloc(version_count * sizeof(struct nfs4_ff_ds_version),
+			      gfp_flags);
+	if (!ds_versions)
+		goto out_scratch;
+
+	for (i = 0; i < version_count; i++) {
+		/* 20 = version(4) + minor_version(4) + rsize(4) + wsize(4) +
+		 * tightly_coupled(4) */
+		p = xdr_inline_decode(&stream, 20);
+		if (unlikely(!p))
+			goto out_err_drain_dsaddrs;
+		ds_versions[i].version = be32_to_cpup(p++);
+		ds_versions[i].minor_version = be32_to_cpup(p++);
+		ds_versions[i].rsize = nfs_block_size(be32_to_cpup(p++), NULL);
+		ds_versions[i].wsize = nfs_block_size(be32_to_cpup(p++), NULL);
+		ds_versions[i].tightly_coupled = be32_to_cpup(p);
+
+		if (ds_versions[i].rsize > NFS_MAX_FILE_IO_SIZE)
+			ds_versions[i].rsize = NFS_MAX_FILE_IO_SIZE;
+		if (ds_versions[i].wsize > NFS_MAX_FILE_IO_SIZE)
+			ds_versions[i].wsize = NFS_MAX_FILE_IO_SIZE;
+
+		if (ds_versions[i].version != 3 || ds_versions[i].minor_version != 0) {
+			dprintk("%s: [%d] unsupported ds version %d-%d\n", __func__,
+				i, ds_versions[i].version,
+				ds_versions[i].minor_version);
+			ret = -EPROTONOSUPPORT;
+			goto out_err_drain_dsaddrs;
+		}
+
+		dprintk("%s: [%d] vers %u minor_ver %u rsize %u wsize %u coupled %d\n",
+			__func__, i, ds_versions[i].version,
+			ds_versions[i].minor_version,
+			ds_versions[i].rsize,
+			ds_versions[i].wsize,
+			ds_versions[i].tightly_coupled);
+	}
+
+	new_ds->ds_versions = ds_versions;
+	new_ds->ds_versions_cnt = version_count;
+
+	new_ds->ds = nfs4_pnfs_ds_add(&dsaddrs, gfp_flags);
+	if (!new_ds->ds)
+		goto out_err_drain_dsaddrs;
+
+	/* If DS was already in cache, free ds addrs */
+	while (!list_empty(&dsaddrs)) {
+		da = list_first_entry(&dsaddrs,
+				      struct nfs4_pnfs_ds_addr,
+				      da_node);
+		list_del_init(&da->da_node);
+		kfree(da->da_remotestr);
+		kfree(da);
+	}
+
+	__free_page(scratch);
+	return new_ds;
+
+out_err_drain_dsaddrs:
+	while (!list_empty(&dsaddrs)) {
+		da = list_first_entry(&dsaddrs, struct nfs4_pnfs_ds_addr,
+				      da_node);
+		list_del_init(&da->da_node);
+		kfree(da->da_remotestr);
+		kfree(da);
+	}
+
+	kfree(ds_versions);
+out_scratch:
+	__free_page(scratch);
+out_err:
+	kfree(new_ds);
+
+	dprintk("%s ERROR: returning %d\n", __func__, ret);
+	return NULL;
+}
+
+static u64
+end_offset(u64 start, u64 len)
+{
+	u64 end;
+
+	end = start + len;
+	return end >= start ? end : NFS4_MAX_UINT64;
+}
+
+static void extend_ds_error(struct nfs4_ff_layout_ds_err *err,
+			    u64 offset, u64 length)
+{
+	u64 end;
+
+	end = max_t(u64, end_offset(err->offset, err->length),
+		    end_offset(offset, length));
+	err->offset = min_t(u64, err->offset, offset);
+	err->length = end - err->offset;
+}
+
+static bool ds_error_can_merge(struct nfs4_ff_layout_ds_err *err,  u64 offset,
+			       u64 length, int status, enum nfs_opnum4 opnum,
+			       nfs4_stateid *stateid,
+			       struct nfs4_deviceid *deviceid)
+{
+	return err->status == status && err->opnum == opnum &&
+	       nfs4_stateid_match(&err->stateid, stateid) &&
+	       !memcmp(&err->deviceid, deviceid, sizeof(*deviceid)) &&
+	       end_offset(err->offset, err->length) >= offset &&
+	       err->offset <= end_offset(offset, length);
+}
+
+static bool merge_ds_error(struct nfs4_ff_layout_ds_err *old,
+			   struct nfs4_ff_layout_ds_err *new)
+{
+	if (!ds_error_can_merge(old, new->offset, new->length, new->status,
+				new->opnum, &new->stateid, &new->deviceid))
+		return false;
+
+	extend_ds_error(old, new->offset, new->length);
+	return true;
+}
+
+static bool
+ff_layout_add_ds_error_locked(struct nfs4_flexfile_layout *flo,
+			      struct nfs4_ff_layout_ds_err *dserr)
+{
+	struct nfs4_ff_layout_ds_err *err;
+
+	list_for_each_entry(err, &flo->error_list, list) {
+		if (merge_ds_error(err, dserr)) {
+			return true;
+		}
+	}
+
+	list_add(&dserr->list, &flo->error_list);
+	return false;
+}
+
+static bool
+ff_layout_update_ds_error(struct nfs4_flexfile_layout *flo, u64 offset,
+			  u64 length, int status, enum nfs_opnum4 opnum,
+			  nfs4_stateid *stateid, struct nfs4_deviceid *deviceid)
+{
+	bool found = false;
+	struct nfs4_ff_layout_ds_err *err;
+
+	list_for_each_entry(err, &flo->error_list, list) {
+		if (ds_error_can_merge(err, offset, length, status, opnum,
+				       stateid, deviceid)) {
+			found = true;
+			extend_ds_error(err, offset, length);
+			break;
+		}
+	}
+
+	return found;
+}
+
+int ff_layout_track_ds_error(struct nfs4_flexfile_layout *flo,
+			     struct nfs4_ff_layout_mirror *mirror, u64 offset,
+			     u64 length, int status, enum nfs_opnum4 opnum,
+			     gfp_t gfp_flags)
+{
+	struct nfs4_ff_layout_ds_err *dserr;
+	bool needfree;
+
+	if (status == 0)
+		return 0;
+
+	if (mirror->mirror_ds == NULL)
+		return -EINVAL;
+
+	spin_lock(&flo->generic_hdr.plh_inode->i_lock);
+	if (ff_layout_update_ds_error(flo, offset, length, status, opnum,
+				      &mirror->stateid,
+				      &mirror->mirror_ds->id_node.deviceid)) {
+		spin_unlock(&flo->generic_hdr.plh_inode->i_lock);
+		return 0;
+	}
+	spin_unlock(&flo->generic_hdr.plh_inode->i_lock);
+	dserr = kmalloc(sizeof(*dserr), gfp_flags);
+	if (!dserr)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&dserr->list);
+	dserr->offset = offset;
+	dserr->length = length;
+	dserr->status = status;
+	dserr->opnum = opnum;
+	nfs4_stateid_copy(&dserr->stateid, &mirror->stateid);
+	memcpy(&dserr->deviceid, &mirror->mirror_ds->id_node.deviceid,
+	       NFS4_DEVICEID4_SIZE);
+
+	spin_lock(&flo->generic_hdr.plh_inode->i_lock);
+	needfree = ff_layout_add_ds_error_locked(flo, dserr);
+	spin_unlock(&flo->generic_hdr.plh_inode->i_lock);
+	if (needfree)
+		kfree(dserr);
+
+	return 0;
+}
+
+/* currently we only support AUTH_NONE and AUTH_SYS */
+static rpc_authflavor_t
+nfs4_ff_layout_choose_authflavor(struct nfs4_ff_layout_mirror *mirror)
+{
+	if (mirror->uid == (u32)-1)
+		return RPC_AUTH_NULL;
+	return RPC_AUTH_UNIX;
+}
+
+/* fetch cred for NFSv3 DS */
+static int ff_layout_update_mirror_cred(struct nfs4_ff_layout_mirror *mirror,
+				      struct nfs4_pnfs_ds *ds)
+{
+	if (ds->ds_clp && !mirror->cred &&
+	    mirror->mirror_ds->ds_versions[0].version == 3) {
+		struct rpc_auth *auth = ds->ds_clp->cl_rpcclient->cl_auth;
+		struct rpc_cred *cred;
+		struct auth_cred acred = {
+			.uid = make_kuid(&init_user_ns, mirror->uid),
+			.gid = make_kgid(&init_user_ns, mirror->gid),
+		};
+
+		/* AUTH_NULL ignores acred */
+		cred = auth->au_ops->lookup_cred(auth, &acred, 0);
+		if (IS_ERR(cred)) {
+			dprintk("%s: lookup_cred failed with %ld\n",
+				__func__, PTR_ERR(cred));
+			return PTR_ERR(cred);
+		} else {
+			mirror->cred = cred;
+		}
+	}
+	return 0;
+}
+
+struct nfs_fh *
+nfs4_ff_layout_select_ds_fh(struct pnfs_layout_segment *lseg, u32 mirror_idx)
+{
+	struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, mirror_idx);
+	struct nfs_fh *fh = NULL;
+	struct nfs4_deviceid_node *devid;
+
+	if (mirror == NULL || mirror->mirror_ds == NULL ||
+	    mirror->mirror_ds->ds == NULL) {
+		printk(KERN_ERR "NFS: %s: No data server for mirror offset index %d\n",
+			__func__, mirror_idx);
+		if (mirror && mirror->mirror_ds) {
+			devid = &mirror->mirror_ds->id_node;
+			pnfs_generic_mark_devid_invalid(devid);
+		}
+		goto out;
+	}
+
+	/* FIXME: For now assume there is only 1 version available for the DS */
+	fh = &mirror->fh_versions[0];
+out:
+	return fh;
+}
+
+/* Upon return, either ds is connected, or ds is NULL */
+struct nfs4_pnfs_ds *
+nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg, u32 ds_idx,
+			  bool fail_return)
+{
+	struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, ds_idx);
+	struct nfs4_pnfs_ds *ds = NULL;
+	struct nfs4_deviceid_node *devid;
+	struct inode *ino = lseg->pls_layout->plh_inode;
+	struct nfs_server *s = NFS_SERVER(ino);
+	unsigned int max_payload;
+	rpc_authflavor_t flavor;
+
+	if (mirror == NULL || mirror->mirror_ds == NULL ||
+	    mirror->mirror_ds->ds == NULL) {
+		printk(KERN_ERR "NFS: %s: No data server for offset index %d\n",
+			__func__, ds_idx);
+		if (mirror && mirror->mirror_ds) {
+			devid = &mirror->mirror_ds->id_node;
+			pnfs_generic_mark_devid_invalid(devid);
+		}
+		goto out;
+	}
+
+	devid = &mirror->mirror_ds->id_node;
+	if (ff_layout_test_devid_unavailable(devid))
+		goto out;
+
+	ds = mirror->mirror_ds->ds;
+	/* matching smp_wmb() in _nfs4_pnfs_v3/4_ds_connect */
+	smp_rmb();
+	if (ds->ds_clp)
+		goto out;
+
+	flavor = nfs4_ff_layout_choose_authflavor(mirror);
+
+	/* FIXME: For now we assume the server sent only one version of NFS
+	 * to use for the DS.
+	 */
+	nfs4_pnfs_ds_connect(s, ds, devid, dataserver_timeo,
+			     dataserver_retrans,
+			     mirror->mirror_ds->ds_versions[0].version,
+			     mirror->mirror_ds->ds_versions[0].minor_version,
+			     flavor);
+
+	/* connect success, check rsize/wsize limit */
+	if (ds->ds_clp) {
+		max_payload =
+			nfs_block_size(rpc_max_payload(ds->ds_clp->cl_rpcclient),
+				       NULL);
+		if (mirror->mirror_ds->ds_versions[0].rsize > max_payload)
+			mirror->mirror_ds->ds_versions[0].rsize = max_payload;
+		if (mirror->mirror_ds->ds_versions[0].wsize > max_payload)
+			mirror->mirror_ds->ds_versions[0].wsize = max_payload;
+	} else {
+		ff_layout_track_ds_error(FF_LAYOUT_FROM_HDR(lseg->pls_layout),
+					 mirror, lseg->pls_range.offset,
+					 lseg->pls_range.length, NFS4ERR_NXIO,
+					 OP_ILLEGAL, GFP_NOIO);
+		if (fail_return) {
+			pnfs_error_mark_layout_for_return(ino, lseg);
+			if (ff_layout_has_available_ds(lseg))
+				pnfs_set_retry_layoutget(lseg->pls_layout);
+			else
+				pnfs_clear_retry_layoutget(lseg->pls_layout);
+
+		} else {
+			if (ff_layout_has_available_ds(lseg))
+				set_bit(NFS_LAYOUT_RETURN_BEFORE_CLOSE,
+					&lseg->pls_layout->plh_flags);
+			else {
+				pnfs_error_mark_layout_for_return(ino, lseg);
+				pnfs_clear_retry_layoutget(lseg->pls_layout);
+			}
+		}
+	}
+
+	if (ff_layout_update_mirror_cred(mirror, ds))
+		ds = NULL;
+out:
+	return ds;
+}
+
+struct rpc_cred *
+ff_layout_get_ds_cred(struct pnfs_layout_segment *lseg, u32 ds_idx,
+		      struct rpc_cred *mdscred)
+{
+	struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, ds_idx);
+	struct rpc_cred *cred = ERR_PTR(-EINVAL);
+
+	if (!nfs4_ff_layout_prepare_ds(lseg, ds_idx, true))
+		goto out;
+
+	if (mirror && mirror->cred)
+		cred = mirror->cred;
+	else
+		cred = mdscred;
+out:
+	return cred;
+}
+
+/**
+* Find or create a DS rpc client with th MDS server rpc client auth flavor
+* in the nfs_client cl_ds_clients list.
+*/
+struct rpc_clnt *
+nfs4_ff_find_or_create_ds_client(struct pnfs_layout_segment *lseg, u32 ds_idx,
+				 struct nfs_client *ds_clp, struct inode *inode)
+{
+	struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, ds_idx);
+
+	switch (mirror->mirror_ds->ds_versions[0].version) {
+	case 3:
+		/* For NFSv3 DS, flavor is set when creating DS connections */
+		return ds_clp->cl_rpcclient;
+	case 4:
+		return nfs4_find_or_create_ds_client(ds_clp, inode);
+	default:
+		BUG();
+	}
+}
+
+static bool is_range_intersecting(u64 offset1, u64 length1,
+				  u64 offset2, u64 length2)
+{
+	u64 end1 = end_offset(offset1, length1);
+	u64 end2 = end_offset(offset2, length2);
+
+	return (end1 == NFS4_MAX_UINT64 || end1 > offset2) &&
+	       (end2 == NFS4_MAX_UINT64 || end2 > offset1);
+}
+
+/* called with inode i_lock held */
+int ff_layout_encode_ds_ioerr(struct nfs4_flexfile_layout *flo,
+			      struct xdr_stream *xdr, int *count,
+			      const struct pnfs_layout_range *range)
+{
+	struct nfs4_ff_layout_ds_err *err, *n;
+	__be32 *p;
+
+	list_for_each_entry_safe(err, n, &flo->error_list, list) {
+		if (!is_range_intersecting(err->offset, err->length,
+					   range->offset, range->length))
+			continue;
+		/* offset(8) + length(8) + stateid(NFS4_STATEID_SIZE)
+		 * + deviceid(NFS4_DEVICEID4_SIZE) + status(4) + opnum(4)
+		 */
+		p = xdr_reserve_space(xdr,
+				24 + NFS4_STATEID_SIZE + NFS4_DEVICEID4_SIZE);
+		if (unlikely(!p))
+			return -ENOBUFS;
+		p = xdr_encode_hyper(p, err->offset);
+		p = xdr_encode_hyper(p, err->length);
+		p = xdr_encode_opaque_fixed(p, &err->stateid,
+					    NFS4_STATEID_SIZE);
+		p = xdr_encode_opaque_fixed(p, &err->deviceid,
+					    NFS4_DEVICEID4_SIZE);
+		*p++ = cpu_to_be32(err->status);
+		*p++ = cpu_to_be32(err->opnum);
+		*count += 1;
+		list_del(&err->list);
+		kfree(err);
+		dprintk("%s: offset %llu length %llu status %d op %d count %d\n",
+			__func__, err->offset, err->length, err->status,
+			err->opnum, *count);
+	}
+
+	return 0;
+}
+
+bool ff_layout_has_available_ds(struct pnfs_layout_segment *lseg)
+{
+	struct nfs4_ff_layout_mirror *mirror;
+	struct nfs4_deviceid_node *devid;
+	int idx;
+
+	for (idx = 0; idx < FF_LAYOUT_MIRROR_COUNT(lseg); idx++) {
+		mirror = FF_LAYOUT_COMP(lseg, idx);
+		if (mirror && mirror->mirror_ds) {
+			devid = &mirror->mirror_ds->id_node;
+			if (!ff_layout_test_devid_unavailable(devid))
+				return true;
+		}
+	}
+
+	return false;
+}
+
+module_param(dataserver_retrans, uint, 0644);
+MODULE_PARM_DESC(dataserver_retrans, "The  number of times the NFSv4.1 client "
+			"retries a request before it attempts further "
+			" recovery  action.");
+module_param(dataserver_timeo, uint, 0644);
+MODULE_PARM_DESC(dataserver_timeo, "The time (in tenths of a second) the "
+			"NFSv4.1  client  waits for a response from a "
+			" data server before it retries an NFS request.");