Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

4 files changed, 3476 insertions, 0 deletions

diff --git a/fs/nfs/flexfilelayout/Makefile b/fs/nfs/flexfilelayout/Makefile
new file mode 100644
index 0000000000..49f03422b6
--- /dev/null
+++ b/fs/nfs/flexfilelayout/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Makefile for the pNFS Flexfile Layout Driver kernel module
+#
+obj-$(CONFIG_PNFS_FLEXFILE_LAYOUT) += nfs_layout_flexfiles.o
+nfs_layout_flexfiles-y := flexfilelayout.o flexfilelayoutdev.o
diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
new file mode 100644
index 0000000000..ef817a0475
--- /dev/null
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -0,0 +1,2623 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Module for pnfs flexfile layout driver.
+ *
+ * Copyright (c) 2014, Primary Data, Inc. All rights reserved.
+ *
+ * Tao Peng <bergwolf@primarydata.com>
+ */
+
+#include <linux/nfs_fs.h>
+#include <linux/nfs_mount.h>
+#include <linux/nfs_page.h>
+#include <linux/module.h>
+#include <linux/sched/mm.h>
+
+#include <linux/sunrpc/metrics.h>
+
+#include "flexfilelayout.h"
+#include "../nfs4session.h"
+#include "../nfs4idmap.h"
+#include "../internal.h"
+#include "../delegation.h"
+#include "../nfs4trace.h"
+#include "../iostat.h"
+#include "../nfs.h"
+#include "../nfs42.h"
+
+#define NFSDBG_FACILITY         NFSDBG_PNFS_LD
+
+#define FF_LAYOUT_POLL_RETRY_MAX     (15*HZ)
+#define FF_LAYOUTRETURN_MAXERR 20
+
+enum nfs4_ff_op_type {
+	NFS4_FF_OP_LAYOUTSTATS,
+	NFS4_FF_OP_LAYOUTRETURN,
+};
+
+static unsigned short io_maxretrans;
+
+static const struct pnfs_commit_ops ff_layout_commit_ops;
+static void ff_layout_read_record_layoutstats_done(struct rpc_task *task,
+		struct nfs_pgio_header *hdr);
+static int
+ff_layout_mirror_prepare_stats(struct pnfs_layout_hdr *lo,
+			       struct nfs42_layoutstat_devinfo *devinfo,
+			       int dev_limit, enum nfs4_ff_op_type type);
+static void ff_layout_encode_ff_layoutupdate(struct xdr_stream *xdr,
+			      const struct nfs42_layoutstat_devinfo *devinfo,
+			      struct nfs4_ff_layout_mirror *mirror);
+
+static struct pnfs_layout_hdr *
+ff_layout_alloc_layout_hdr(struct inode *inode, gfp_t gfp_flags)
+{
+	struct nfs4_flexfile_layout *ffl;
+
+	ffl = kzalloc(sizeof(*ffl), gfp_flags);
+	if (ffl) {
+		pnfs_init_ds_commit_info(&ffl->commit_info);
+		INIT_LIST_HEAD(&ffl->error_list);
+		INIT_LIST_HEAD(&ffl->mirrors);
+		ffl->last_report_time = ktime_get();
+		ffl->commit_info.ops = &ff_layout_commit_ops;
+		return &ffl->generic_hdr;
+	} else
+		return NULL;
+}
+
+static void
+ff_layout_free_layout_hdr(struct pnfs_layout_hdr *lo)
+{
+	struct nfs4_flexfile_layout *ffl = FF_LAYOUT_FROM_HDR(lo);
+	struct nfs4_ff_layout_ds_err *err, *n;
+
+	list_for_each_entry_safe(err, n, &ffl->error_list, list) {
+		list_del(&err->list);
+		kfree(err);
+	}
+	kfree_rcu(ffl, generic_hdr.plh_rcu);
+}
+
+static int decode_pnfs_stateid(struct xdr_stream *xdr, nfs4_stateid *stateid)
+{
+	__be32 *p;
+
+	p = xdr_inline_decode(xdr, NFS4_STATEID_SIZE);
+	if (unlikely(p == NULL))
+		return -ENOBUFS;
+	stateid->type = NFS4_PNFS_DS_STATEID_TYPE;
+	memcpy(stateid->data, p, NFS4_STATEID_SIZE);
+	dprintk("%s: stateid id= [%x%x%x%x]\n", __func__,
+		p[0], p[1], p[2], p[3]);
+	return 0;
+}
+
+static int decode_deviceid(struct xdr_stream *xdr, struct nfs4_deviceid *devid)
+{
+	__be32 *p;
+
+	p = xdr_inline_decode(xdr, NFS4_DEVICEID4_SIZE);
+	if (unlikely(!p))
+		return -ENOBUFS;
+	memcpy(devid, p, NFS4_DEVICEID4_SIZE);
+	nfs4_print_deviceid(devid);
+	return 0;
+}
+
+static int decode_nfs_fh(struct xdr_stream *xdr, struct nfs_fh *fh)
+{
+	__be32 *p;
+
+	p = xdr_inline_decode(xdr, 4);
+	if (unlikely(!p))
+		return -ENOBUFS;
+	fh->size = be32_to_cpup(p++);
+	if (fh->size > NFS_MAXFHSIZE) {
+		printk(KERN_ERR "NFS flexfiles: Too big fh received %d\n",
+		       fh->size);
+		return -EOVERFLOW;
+	}
+	/* fh.data */
+	p = xdr_inline_decode(xdr, fh->size);
+	if (unlikely(!p))
+		return -ENOBUFS;
+	memcpy(&fh->data, p, fh->size);
+	dprintk("%s: fh len %d\n", __func__, fh->size);
+
+	return 0;
+}
+
+/*
+ * Currently only stringified uids and gids are accepted.
+ * I.e., kerberos is not supported to the DSes, so no pricipals.
+ *
+ * That means that one common function will suffice, but when
+ * principals are added, this should be split to accomodate
+ * calls to both nfs_map_name_to_uid() and nfs_map_group_to_gid().
+ */
+static int
+decode_name(struct xdr_stream *xdr, u32 *id)
+{
+	__be32 *p;
+	int len;
+
+	/* opaque_length(4)*/
+	p = xdr_inline_decode(xdr, 4);
+	if (unlikely(!p))
+		return -ENOBUFS;
+	len = be32_to_cpup(p++);
+	if (len < 0)
+		return -EINVAL;
+
+	dprintk("%s: len %u\n", __func__, len);
+
+	/* opaque body */
+	p = xdr_inline_decode(xdr, len);
+	if (unlikely(!p))
+		return -ENOBUFS;
+
+	if (!nfs_map_string_to_numeric((char *)p, len, id))
+		return -EINVAL;
+
+	return 0;
+}
+
+static bool ff_mirror_match_fh(const struct nfs4_ff_layout_mirror *m1,
+		const struct nfs4_ff_layout_mirror *m2)
+{
+	int i, j;
+
+	if (m1->fh_versions_cnt != m2->fh_versions_cnt)
+		return false;
+	for (i = 0; i < m1->fh_versions_cnt; i++) {
+		bool found_fh = false;
+		for (j = 0; j < m2->fh_versions_cnt; j++) {
+			if (nfs_compare_fh(&m1->fh_versions[i],
+					&m2->fh_versions[j]) == 0) {
+				found_fh = true;
+				break;
+			}
+		}
+		if (!found_fh)
+			return false;
+	}
+	return true;
+}
+
+static struct nfs4_ff_layout_mirror *
+ff_layout_add_mirror(struct pnfs_layout_hdr *lo,
+		struct nfs4_ff_layout_mirror *mirror)
+{
+	struct nfs4_flexfile_layout *ff_layout = FF_LAYOUT_FROM_HDR(lo);
+	struct nfs4_ff_layout_mirror *pos;
+	struct inode *inode = lo->plh_inode;
+
+	spin_lock(&inode->i_lock);
+	list_for_each_entry(pos, &ff_layout->mirrors, mirrors) {
+		if (memcmp(&mirror->devid, &pos->devid, sizeof(pos->devid)) != 0)
+			continue;
+		if (!ff_mirror_match_fh(mirror, pos))
+			continue;
+		if (refcount_inc_not_zero(&pos->ref)) {
+			spin_unlock(&inode->i_lock);
+			return pos;
+		}
+	}
+	list_add(&mirror->mirrors, &ff_layout->mirrors);
+	mirror->layout = lo;
+	spin_unlock(&inode->i_lock);
+	return mirror;
+}
+
+static void
+ff_layout_remove_mirror(struct nfs4_ff_layout_mirror *mirror)
+{
+	struct inode *inode;
+	if (mirror->layout == NULL)
+		return;
+	inode = mirror->layout->plh_inode;
+	spin_lock(&inode->i_lock);
+	list_del(&mirror->mirrors);
+	spin_unlock(&inode->i_lock);
+	mirror->layout = NULL;
+}
+
+static struct nfs4_ff_layout_mirror *ff_layout_alloc_mirror(gfp_t gfp_flags)
+{
+	struct nfs4_ff_layout_mirror *mirror;
+
+	mirror = kzalloc(sizeof(*mirror), gfp_flags);
+	if (mirror != NULL) {
+		spin_lock_init(&mirror->lock);
+		refcount_set(&mirror->ref, 1);
+		INIT_LIST_HEAD(&mirror->mirrors);
+	}
+	return mirror;
+}
+
+static void ff_layout_free_mirror(struct nfs4_ff_layout_mirror *mirror)
+{
+	const struct cred	*cred;
+
+	ff_layout_remove_mirror(mirror);
+	kfree(mirror->fh_versions);
+	cred = rcu_access_pointer(mirror->ro_cred);
+	put_cred(cred);
+	cred = rcu_access_pointer(mirror->rw_cred);
+	put_cred(cred);
+	nfs4_ff_layout_put_deviceid(mirror->mirror_ds);
+	kfree(mirror);
+}
+
+static void ff_layout_put_mirror(struct nfs4_ff_layout_mirror *mirror)
+{
+	if (mirror != NULL && refcount_dec_and_test(&mirror->ref))
+		ff_layout_free_mirror(mirror);
+}
+
+static void ff_layout_free_mirror_array(struct nfs4_ff_layout_segment *fls)
+{
+	u32 i;
+
+	for (i = 0; i < fls->mirror_array_cnt; i++)
+		ff_layout_put_mirror(fls->mirror_array[i]);
+}
+
+static void _ff_layout_free_lseg(struct nfs4_ff_layout_segment *fls)
+{
+	if (fls) {
+		ff_layout_free_mirror_array(fls);
+		kfree(fls);
+	}
+}
+
+static bool
+ff_lseg_match_mirrors(struct pnfs_layout_segment *l1,
+		struct pnfs_layout_segment *l2)
+{
+	const struct nfs4_ff_layout_segment *fl1 = FF_LAYOUT_LSEG(l1);
+	const struct nfs4_ff_layout_segment *fl2 = FF_LAYOUT_LSEG(l1);
+	u32 i;
+
+	if (fl1->mirror_array_cnt != fl2->mirror_array_cnt)
+		return false;
+	for (i = 0; i < fl1->mirror_array_cnt; i++) {
+		if (fl1->mirror_array[i] != fl2->mirror_array[i])
+			return false;
+	}
+	return true;
+}
+
+static bool
+ff_lseg_range_is_after(const struct pnfs_layout_range *l1,
+		const struct pnfs_layout_range *l2)
+{
+	u64 end1, end2;
+
+	if (l1->iomode != l2->iomode)
+		return l1->iomode != IOMODE_READ;
+	end1 = pnfs_calc_offset_end(l1->offset, l1->length);
+	end2 = pnfs_calc_offset_end(l2->offset, l2->length);
+	if (end1 < l2->offset)
+		return false;
+	if (end2 < l1->offset)
+		return true;
+	return l2->offset <= l1->offset;
+}
+
+static bool
+ff_lseg_merge(struct pnfs_layout_segment *new,
+		struct pnfs_layout_segment *old)
+{
+	u64 new_end, old_end;
+
+	if (test_bit(NFS_LSEG_LAYOUTRETURN, &old->pls_flags))
+		return false;
+	if (new->pls_range.iomode != old->pls_range.iomode)
+		return false;
+	old_end = pnfs_calc_offset_end(old->pls_range.offset,
+			old->pls_range.length);
+	if (old_end < new->pls_range.offset)
+		return false;
+	new_end = pnfs_calc_offset_end(new->pls_range.offset,
+			new->pls_range.length);
+	if (new_end < old->pls_range.offset)
+		return false;
+	if (!ff_lseg_match_mirrors(new, old))
+		return false;
+
+	/* Mergeable: copy info from 'old' to 'new' */
+	if (new_end < old_end)
+		new_end = old_end;
+	if (new->pls_range.offset < old->pls_range.offset)
+		new->pls_range.offset = old->pls_range.offset;
+	new->pls_range.length = pnfs_calc_offset_length(new->pls_range.offset,
+			new_end);
+	if (test_bit(NFS_LSEG_ROC, &old->pls_flags))
+		set_bit(NFS_LSEG_ROC, &new->pls_flags);
+	return true;
+}
+
+static void
+ff_layout_add_lseg(struct pnfs_layout_hdr *lo,
+		struct pnfs_layout_segment *lseg,
+		struct list_head *free_me)
+{
+	pnfs_generic_layout_insert_lseg(lo, lseg,
+			ff_lseg_range_is_after,
+			ff_lseg_merge,
+			free_me);
+}
+
+static void ff_layout_sort_mirrors(struct nfs4_ff_layout_segment *fls)
+{
+	int i, j;
+
+	for (i = 0; i < fls->mirror_array_cnt - 1; i++) {
+		for (j = i + 1; j < fls->mirror_array_cnt; j++)
+			if (fls->mirror_array[i]->efficiency <
+			    fls->mirror_array[j]->efficiency)
+				swap(fls->mirror_array[i],
+				     fls->mirror_array[j]);
+	}
+}
+
+static struct pnfs_layout_segment *
+ff_layout_alloc_lseg(struct pnfs_layout_hdr *lh,
+		     struct nfs4_layoutget_res *lgr,
+		     gfp_t gfp_flags)
+{
+	struct pnfs_layout_segment *ret;
+	struct nfs4_ff_layout_segment *fls = NULL;
+	struct xdr_stream stream;
+	struct xdr_buf buf;
+	struct page *scratch;
+	u64 stripe_unit;
+	u32 mirror_array_cnt;
+	__be32 *p;
+	int i, rc;
+
+	dprintk("--> %s\n", __func__);
+	scratch = alloc_page(gfp_flags);
+	if (!scratch)
+		return ERR_PTR(-ENOMEM);
+
+	xdr_init_decode_pages(&stream, &buf, lgr->layoutp->pages,
+			      lgr->layoutp->len);
+	xdr_set_scratch_page(&stream, scratch);
+
+	/* stripe unit and mirror_array_cnt */
+	rc = -EIO;
+	p = xdr_inline_decode(&stream, 8 + 4);
+	if (!p)
+		goto out_err_free;
+
+	p = xdr_decode_hyper(p, &stripe_unit);
+	mirror_array_cnt = be32_to_cpup(p++);
+	dprintk("%s: stripe_unit=%llu mirror_array_cnt=%u\n", __func__,
+		stripe_unit, mirror_array_cnt);
+
+	if (mirror_array_cnt > NFS4_FLEXFILE_LAYOUT_MAX_MIRROR_CNT ||
+	    mirror_array_cnt == 0)
+		goto out_err_free;
+
+	rc = -ENOMEM;
+	fls = kzalloc(struct_size(fls, mirror_array, mirror_array_cnt),
+			gfp_flags);
+	if (!fls)
+		goto out_err_free;
+
+	fls->mirror_array_cnt = mirror_array_cnt;
+	fls->stripe_unit = stripe_unit;
+
+	for (i = 0; i < fls->mirror_array_cnt; i++) {
+		struct nfs4_ff_layout_mirror *mirror;
+		struct cred *kcred;
+		const struct cred __rcu *cred;
+		kuid_t uid;
+		kgid_t gid;
+		u32 ds_count, fh_count, id;
+		int j;
+
+		rc = -EIO;
+		p = xdr_inline_decode(&stream, 4);
+		if (!p)
+			goto out_err_free;
+		ds_count = be32_to_cpup(p);
+
+		/* FIXME: allow for striping? */
+		if (ds_count != 1)
+			goto out_err_free;
+
+		fls->mirror_array[i] = ff_layout_alloc_mirror(gfp_flags);
+		if (fls->mirror_array[i] == NULL) {
+			rc = -ENOMEM;
+			goto out_err_free;
+		}
+
+		fls->mirror_array[i]->ds_count = ds_count;
+
+		/* deviceid */
+		rc = decode_deviceid(&stream, &fls->mirror_array[i]->devid);
+		if (rc)
+			goto out_err_free;
+
+		/* efficiency */
+		rc = -EIO;
+		p = xdr_inline_decode(&stream, 4);
+		if (!p)
+			goto out_err_free;
+		fls->mirror_array[i]->efficiency = be32_to_cpup(p);
+
+		/* stateid */
+		rc = decode_pnfs_stateid(&stream, &fls->mirror_array[i]->stateid);
+		if (rc)
+			goto out_err_free;
+
+		/* fh */
+		rc = -EIO;
+		p = xdr_inline_decode(&stream, 4);
+		if (!p)
+			goto out_err_free;
+		fh_count = be32_to_cpup(p);
+
+		fls->mirror_array[i]->fh_versions =
+			kcalloc(fh_count, sizeof(struct nfs_fh),
+				gfp_flags);
+		if (fls->mirror_array[i]->fh_versions == NULL) {
+			rc = -ENOMEM;
+			goto out_err_free;
+		}
+
+		for (j = 0; j < fh_count; j++) {
+			rc = decode_nfs_fh(&stream,
+					   &fls->mirror_array[i]->fh_versions[j]);
+			if (rc)
+				goto out_err_free;
+		}
+
+		fls->mirror_array[i]->fh_versions_cnt = fh_count;
+
+		/* user */
+		rc = decode_name(&stream, &id);
+		if (rc)
+			goto out_err_free;
+
+		uid = make_kuid(&init_user_ns, id);
+
+		/* group */
+		rc = decode_name(&stream, &id);
+		if (rc)
+			goto out_err_free;
+
+		gid = make_kgid(&init_user_ns, id);
+
+		if (gfp_flags & __GFP_FS)
+			kcred = prepare_kernel_cred(&init_task);
+		else {
+			unsigned int nofs_flags = memalloc_nofs_save();
+			kcred = prepare_kernel_cred(&init_task);
+			memalloc_nofs_restore(nofs_flags);
+		}
+		rc = -ENOMEM;
+		if (!kcred)
+			goto out_err_free;
+		kcred->fsuid = uid;
+		kcred->fsgid = gid;
+		cred = RCU_INITIALIZER(kcred);
+
+		if (lgr->range.iomode == IOMODE_READ)
+			rcu_assign_pointer(fls->mirror_array[i]->ro_cred, cred);
+		else
+			rcu_assign_pointer(fls->mirror_array[i]->rw_cred, cred);
+
+		mirror = ff_layout_add_mirror(lh, fls->mirror_array[i]);
+		if (mirror != fls->mirror_array[i]) {
+			/* swap cred ptrs so free_mirror will clean up old */
+			if (lgr->range.iomode == IOMODE_READ) {
+				cred = xchg(&mirror->ro_cred, cred);
+				rcu_assign_pointer(fls->mirror_array[i]->ro_cred, cred);
+			} else {
+				cred = xchg(&mirror->rw_cred, cred);
+				rcu_assign_pointer(fls->mirror_array[i]->rw_cred, cred);
+			}
+			ff_layout_free_mirror(fls->mirror_array[i]);
+			fls->mirror_array[i] = mirror;
+		}
+
+		dprintk("%s: iomode %s uid %u gid %u\n", __func__,
+			lgr->range.iomode == IOMODE_READ ? "READ" : "RW",
+			from_kuid(&init_user_ns, uid),
+			from_kgid(&init_user_ns, gid));
+	}
+
+	p = xdr_inline_decode(&stream, 4);
+	if (!p)
+		goto out_sort_mirrors;
+	fls->flags = be32_to_cpup(p);
+
+	p = xdr_inline_decode(&stream, 4);
+	if (!p)
+		goto out_sort_mirrors;
+	for (i=0; i < fls->mirror_array_cnt; i++)
+		fls->mirror_array[i]->report_interval = be32_to_cpup(p);
+
+out_sort_mirrors:
+	ff_layout_sort_mirrors(fls);
+	ret = &fls->generic_hdr;
+	dprintk("<-- %s (success)\n", __func__);
+out_free_page:
+	__free_page(scratch);
+	return ret;
+out_err_free:
+	_ff_layout_free_lseg(fls);
+	ret = ERR_PTR(rc);
+	dprintk("<-- %s (%d)\n", __func__, rc);
+	goto out_free_page;
+}
+
+static void
+ff_layout_free_lseg(struct pnfs_layout_segment *lseg)
+{
+	struct nfs4_ff_layout_segment *fls = FF_LAYOUT_LSEG(lseg);
+
+	dprintk("--> %s\n", __func__);
+
+	if (lseg->pls_range.iomode == IOMODE_RW) {
+		struct nfs4_flexfile_layout *ffl;
+		struct inode *inode;
+
+		ffl = FF_LAYOUT_FROM_HDR(lseg->pls_layout);
+		inode = ffl->generic_hdr.plh_inode;
+		spin_lock(&inode->i_lock);
+		pnfs_generic_ds_cinfo_release_lseg(&ffl->commit_info, lseg);
+		spin_unlock(&inode->i_lock);
+	}
+	_ff_layout_free_lseg(fls);
+}
+
+static void
+nfs4_ff_start_busy_timer(struct nfs4_ff_busy_timer *timer, ktime_t now)
+{
+	/* first IO request? */
+	if (atomic_inc_return(&timer->n_ops) == 1) {
+		timer->start_time = now;
+	}
+}
+
+static ktime_t
+nfs4_ff_end_busy_timer(struct nfs4_ff_busy_timer *timer, ktime_t now)
+{
+	ktime_t start;
+
+	if (atomic_dec_return(&timer->n_ops) < 0)
+		WARN_ON_ONCE(1);
+
+	start = timer->start_time;
+	timer->start_time = now;
+	return ktime_sub(now, start);
+}
+
+static bool
+nfs4_ff_layoutstat_start_io(struct nfs4_ff_layout_mirror *mirror,
+			    struct nfs4_ff_layoutstat *layoutstat,
+			    ktime_t now)
+{
+	s64 report_interval = FF_LAYOUTSTATS_REPORT_INTERVAL;
+	struct nfs4_flexfile_layout *ffl = FF_LAYOUT_FROM_HDR(mirror->layout);
+
+	nfs4_ff_start_busy_timer(&layoutstat->busy_timer, now);
+	if (!mirror->start_time)
+		mirror->start_time = now;
+	if (mirror->report_interval != 0)
+		report_interval = (s64)mirror->report_interval * 1000LL;
+	else if (layoutstats_timer != 0)
+		report_interval = (s64)layoutstats_timer * 1000LL;
+	if (ktime_to_ms(ktime_sub(now, ffl->last_report_time)) >=
+			report_interval) {
+		ffl->last_report_time = now;
+		return true;
+	}
+
+	return false;
+}
+
+static void
+nfs4_ff_layout_stat_io_update_requested(struct nfs4_ff_layoutstat *layoutstat,
+		__u64 requested)
+{
+	struct nfs4_ff_io_stat *iostat = &layoutstat->io_stat;
+
+	iostat->ops_requested++;
+	iostat->bytes_requested += requested;
+}
+
+static void
+nfs4_ff_layout_stat_io_update_completed(struct nfs4_ff_layoutstat *layoutstat,
+		__u64 requested,
+		__u64 completed,
+		ktime_t time_completed,
+		ktime_t time_started)
+{
+	struct nfs4_ff_io_stat *iostat = &layoutstat->io_stat;
+	ktime_t completion_time = ktime_sub(time_completed, time_started);
+	ktime_t timer;
+
+	iostat->ops_completed++;
+	iostat->bytes_completed += completed;
+	iostat->bytes_not_delivered += requested - completed;
+
+	timer = nfs4_ff_end_busy_timer(&layoutstat->busy_timer, time_completed);
+	iostat->total_busy_time =
+			ktime_add(iostat->total_busy_time, timer);
+	iostat->aggregate_completion_time =
+			ktime_add(iostat->aggregate_completion_time,
+					completion_time);
+}
+
+static void
+nfs4_ff_layout_stat_io_start_read(struct inode *inode,
+		struct nfs4_ff_layout_mirror *mirror,
+		__u64 requested, ktime_t now)
+{
+	bool report;
+
+	spin_lock(&mirror->lock);
+	report = nfs4_ff_layoutstat_start_io(mirror, &mirror->read_stat, now);
+	nfs4_ff_layout_stat_io_update_requested(&mirror->read_stat, requested);
+	set_bit(NFS4_FF_MIRROR_STAT_AVAIL, &mirror->flags);
+	spin_unlock(&mirror->lock);
+
+	if (report)
+		pnfs_report_layoutstat(inode, nfs_io_gfp_mask());
+}
+
+static void
+nfs4_ff_layout_stat_io_end_read(struct rpc_task *task,
+		struct nfs4_ff_layout_mirror *mirror,
+		__u64 requested,
+		__u64 completed)
+{
+	spin_lock(&mirror->lock);
+	nfs4_ff_layout_stat_io_update_completed(&mirror->read_stat,
+			requested, completed,
+			ktime_get(), task->tk_start);
+	set_bit(NFS4_FF_MIRROR_STAT_AVAIL, &mirror->flags);
+	spin_unlock(&mirror->lock);
+}
+
+static void
+nfs4_ff_layout_stat_io_start_write(struct inode *inode,
+		struct nfs4_ff_layout_mirror *mirror,
+		__u64 requested, ktime_t now)
+{
+	bool report;
+
+	spin_lock(&mirror->lock);
+	report = nfs4_ff_layoutstat_start_io(mirror , &mirror->write_stat, now);
+	nfs4_ff_layout_stat_io_update_requested(&mirror->write_stat, requested);
+	set_bit(NFS4_FF_MIRROR_STAT_AVAIL, &mirror->flags);
+	spin_unlock(&mirror->lock);
+
+	if (report)
+		pnfs_report_layoutstat(inode, nfs_io_gfp_mask());
+}
+
+static void
+nfs4_ff_layout_stat_io_end_write(struct rpc_task *task,
+		struct nfs4_ff_layout_mirror *mirror,
+		__u64 requested,
+		__u64 completed,
+		enum nfs3_stable_how committed)
+{
+	if (committed == NFS_UNSTABLE)
+		requested = completed = 0;
+
+	spin_lock(&mirror->lock);
+	nfs4_ff_layout_stat_io_update_completed(&mirror->write_stat,
+			requested, completed, ktime_get(), task->tk_start);
+	set_bit(NFS4_FF_MIRROR_STAT_AVAIL, &mirror->flags);
+	spin_unlock(&mirror->lock);
+}
+
+static void
+ff_layout_mark_ds_unreachable(struct pnfs_layout_segment *lseg, u32 idx)
+{
+	struct nfs4_deviceid_node *devid = FF_LAYOUT_DEVID_NODE(lseg, idx);
+
+	if (devid)
+		nfs4_mark_deviceid_unavailable(devid);
+}
+
+static void
+ff_layout_mark_ds_reachable(struct pnfs_layout_segment *lseg, u32 idx)
+{
+	struct nfs4_deviceid_node *devid = FF_LAYOUT_DEVID_NODE(lseg, idx);
+
+	if (devid)
+		nfs4_mark_deviceid_available(devid);
+}
+
+static struct nfs4_pnfs_ds *
+ff_layout_choose_ds_for_read(struct pnfs_layout_segment *lseg,
+			     u32 start_idx, u32 *best_idx,
+			     bool check_device)
+{
+	struct nfs4_ff_layout_segment *fls = FF_LAYOUT_LSEG(lseg);
+	struct nfs4_ff_layout_mirror *mirror;
+	struct nfs4_pnfs_ds *ds;
+	u32 idx;
+
+	/* mirrors are initially sorted by efficiency */
+	for (idx = start_idx; idx < fls->mirror_array_cnt; idx++) {
+		mirror = FF_LAYOUT_COMP(lseg, idx);
+		ds = nfs4_ff_layout_prepare_ds(lseg, mirror, false);
+		if (!ds)
+			continue;
+
+		if (check_device &&
+		    nfs4_test_deviceid_unavailable(&mirror->mirror_ds->id_node))
+			continue;
+
+		*best_idx = idx;
+		return ds;
+	}
+
+	return NULL;
+}
+
+static struct nfs4_pnfs_ds *
+ff_layout_choose_any_ds_for_read(struct pnfs_layout_segment *lseg,
+				 u32 start_idx, u32 *best_idx)
+{
+	return ff_layout_choose_ds_for_read(lseg, start_idx, best_idx, false);
+}
+
+static struct nfs4_pnfs_ds *
+ff_layout_choose_valid_ds_for_read(struct pnfs_layout_segment *lseg,
+				   u32 start_idx, u32 *best_idx)
+{
+	return ff_layout_choose_ds_for_read(lseg, start_idx, best_idx, true);
+}
+
+static struct nfs4_pnfs_ds *
+ff_layout_choose_best_ds_for_read(struct pnfs_layout_segment *lseg,
+				  u32 start_idx, u32 *best_idx)
+{
+	struct nfs4_pnfs_ds *ds;
+
+	ds = ff_layout_choose_valid_ds_for_read(lseg, start_idx, best_idx);
+	if (ds)
+		return ds;
+	return ff_layout_choose_any_ds_for_read(lseg, start_idx, best_idx);
+}
+
+static struct nfs4_pnfs_ds *
+ff_layout_get_ds_for_read(struct nfs_pageio_descriptor *pgio,
+			  u32 *best_idx)
+{
+	struct pnfs_layout_segment *lseg = pgio->pg_lseg;
+	struct nfs4_pnfs_ds *ds;
+
+	ds = ff_layout_choose_best_ds_for_read(lseg, pgio->pg_mirror_idx,
+					       best_idx);
+	if (ds || !pgio->pg_mirror_idx)
+		return ds;
+	return ff_layout_choose_best_ds_for_read(lseg, 0, best_idx);
+}
+
+static void
+ff_layout_pg_get_read(struct nfs_pageio_descriptor *pgio,
+		      struct nfs_page *req,
+		      bool strict_iomode)
+{
+	pnfs_put_lseg(pgio->pg_lseg);
+	pgio->pg_lseg =
+		pnfs_update_layout(pgio->pg_inode, nfs_req_openctx(req),
+				   req_offset(req), req->wb_bytes, IOMODE_READ,
+				   strict_iomode, nfs_io_gfp_mask());
+	if (IS_ERR(pgio->pg_lseg)) {
+		pgio->pg_error = PTR_ERR(pgio->pg_lseg);
+		pgio->pg_lseg = NULL;
+	}
+}
+
+static void
+ff_layout_pg_check_layout(struct nfs_pageio_descriptor *pgio,
+			  struct nfs_page *req)
+{
+	pnfs_generic_pg_check_layout(pgio);
+	pnfs_generic_pg_check_range(pgio, req);
+}
+
+static void
+ff_layout_pg_init_read(struct nfs_pageio_descriptor *pgio,
+			struct nfs_page *req)
+{
+	struct nfs_pgio_mirror *pgm;
+	struct nfs4_ff_layout_mirror *mirror;
+	struct nfs4_pnfs_ds *ds;
+	u32 ds_idx;
+
+retry:
+	ff_layout_pg_check_layout(pgio, req);
+	/* Use full layout for now */
+	if (!pgio->pg_lseg) {
+		ff_layout_pg_get_read(pgio, req, false);
+		if (!pgio->pg_lseg)
+			goto out_nolseg;
+	}
+	if (ff_layout_avoid_read_on_rw(pgio->pg_lseg)) {
+		ff_layout_pg_get_read(pgio, req, true);
+		if (!pgio->pg_lseg)
+			goto out_nolseg;
+	}
+
+	ds = ff_layout_get_ds_for_read(pgio, &ds_idx);
+	if (!ds) {
+		if (!ff_layout_no_fallback_to_mds(pgio->pg_lseg))
+			goto out_mds;
+		pnfs_generic_pg_cleanup(pgio);
+		/* Sleep for 1 second before retrying */
+		ssleep(1);
+		goto retry;
+	}
+
+	mirror = FF_LAYOUT_COMP(pgio->pg_lseg, ds_idx);
+	pgm = &pgio->pg_mirrors[0];
+	pgm->pg_bsize = mirror->mirror_ds->ds_versions[0].rsize;
+
+	pgio->pg_mirror_idx = ds_idx;
+
+	if (NFS_SERVER(pgio->pg_inode)->flags &
+			(NFS_MOUNT_SOFT|NFS_MOUNT_SOFTERR))
+		pgio->pg_maxretrans = io_maxretrans;
+	return;
+out_nolseg:
+	if (pgio->pg_error < 0)
+		return;
+out_mds:
+	trace_pnfs_mds_fallback_pg_init_read(pgio->pg_inode,
+			0, NFS4_MAX_UINT64, IOMODE_READ,
+			NFS_I(pgio->pg_inode)->layout,
+			pgio->pg_lseg);
+	pgio->pg_maxretrans = 0;
+	nfs_pageio_reset_read_mds(pgio);
+}
+
+static void
+ff_layout_pg_init_write(struct nfs_pageio_descriptor *pgio,
+			struct nfs_page *req)
+{
+	struct nfs4_ff_layout_mirror *mirror;
+	struct nfs_pgio_mirror *pgm;
+	struct nfs4_pnfs_ds *ds;
+	u32 i;
+
+retry:
+	ff_layout_pg_check_layout(pgio, req);
+	if (!pgio->pg_lseg) {
+		pgio->pg_lseg =
+			pnfs_update_layout(pgio->pg_inode, nfs_req_openctx(req),
+					   req_offset(req), req->wb_bytes,
+					   IOMODE_RW, false, nfs_io_gfp_mask());
+		if (IS_ERR(pgio->pg_lseg)) {
+			pgio->pg_error = PTR_ERR(pgio->pg_lseg);
+			pgio->pg_lseg = NULL;
+			return;
+		}
+	}
+	/* If no lseg, fall back to write through mds */
+	if (pgio->pg_lseg == NULL)
+		goto out_mds;
+
+	/* Use a direct mapping of ds_idx to pgio mirror_idx */
+	if (pgio->pg_mirror_count != FF_LAYOUT_MIRROR_COUNT(pgio->pg_lseg))
+		goto out_eagain;
+
+	for (i = 0; i < pgio->pg_mirror_count; i++) {
+		mirror = FF_LAYOUT_COMP(pgio->pg_lseg, i);
+		ds = nfs4_ff_layout_prepare_ds(pgio->pg_lseg, mirror, true);
+		if (!ds) {
+			if (!ff_layout_no_fallback_to_mds(pgio->pg_lseg))
+				goto out_mds;
+			pnfs_generic_pg_cleanup(pgio);
+			/* Sleep for 1 second before retrying */
+			ssleep(1);
+			goto retry;
+		}
+		pgm = &pgio->pg_mirrors[i];
+		pgm->pg_bsize = mirror->mirror_ds->ds_versions[0].wsize;
+	}
+
+	if (NFS_SERVER(pgio->pg_inode)->flags &
+			(NFS_MOUNT_SOFT|NFS_MOUNT_SOFTERR))
+		pgio->pg_maxretrans = io_maxretrans;
+	return;
+out_eagain:
+	pnfs_generic_pg_cleanup(pgio);
+	pgio->pg_error = -EAGAIN;
+	return;
+out_mds:
+	trace_pnfs_mds_fallback_pg_init_write(pgio->pg_inode,
+			0, NFS4_MAX_UINT64, IOMODE_RW,
+			NFS_I(pgio->pg_inode)->layout,
+			pgio->pg_lseg);
+	pgio->pg_maxretrans = 0;
+	nfs_pageio_reset_write_mds(pgio);
+	pgio->pg_error = -EAGAIN;
+}
+
+static unsigned int
+ff_layout_pg_get_mirror_count_write(struct nfs_pageio_descriptor *pgio,
+				    struct nfs_page *req)
+{
+	if (!pgio->pg_lseg) {
+		pgio->pg_lseg =
+			pnfs_update_layout(pgio->pg_inode, nfs_req_openctx(req),
+					   req_offset(req), req->wb_bytes,
+					   IOMODE_RW, false, nfs_io_gfp_mask());
+		if (IS_ERR(pgio->pg_lseg)) {
+			pgio->pg_error = PTR_ERR(pgio->pg_lseg);
+			pgio->pg_lseg = NULL;
+			goto out;
+		}
+	}
+	if (pgio->pg_lseg)
+		return FF_LAYOUT_MIRROR_COUNT(pgio->pg_lseg);
+
+	trace_pnfs_mds_fallback_pg_get_mirror_count(pgio->pg_inode,
+			0, NFS4_MAX_UINT64, IOMODE_RW,
+			NFS_I(pgio->pg_inode)->layout,
+			pgio->pg_lseg);
+	/* no lseg means that pnfs is not in use, so no mirroring here */
+	nfs_pageio_reset_write_mds(pgio);
+out:
+	return 1;
+}
+
+static u32
+ff_layout_pg_set_mirror_write(struct nfs_pageio_descriptor *desc, u32 idx)
+{
+	u32 old = desc->pg_mirror_idx;
+
+	desc->pg_mirror_idx = idx;
+	return old;
+}
+
+static struct nfs_pgio_mirror *
+ff_layout_pg_get_mirror_write(struct nfs_pageio_descriptor *desc, u32 idx)
+{
+	return &desc->pg_mirrors[idx];
+}
+
+static const struct nfs_pageio_ops ff_layout_pg_read_ops = {
+	.pg_init = ff_layout_pg_init_read,
+	.pg_test = pnfs_generic_pg_test,
+	.pg_doio = pnfs_generic_pg_readpages,
+	.pg_cleanup = pnfs_generic_pg_cleanup,
+};
+
+static const struct nfs_pageio_ops ff_layout_pg_write_ops = {
+	.pg_init = ff_layout_pg_init_write,
+	.pg_test = pnfs_generic_pg_test,
+	.pg_doio = pnfs_generic_pg_writepages,
+	.pg_get_mirror_count = ff_layout_pg_get_mirror_count_write,
+	.pg_cleanup = pnfs_generic_pg_cleanup,
+	.pg_get_mirror = ff_layout_pg_get_mirror_write,
+	.pg_set_mirror = ff_layout_pg_set_mirror_write,
+};
+
+static void ff_layout_reset_write(struct nfs_pgio_header *hdr, bool retry_pnfs)
+{
+	struct rpc_task *task = &hdr->task;
+
+	pnfs_layoutcommit_inode(hdr->inode, false);
+
+	if (retry_pnfs) {
+		dprintk("%s Reset task %5u for i/o through pNFS "
+			"(req %s/%llu, %u bytes @ offset %llu)\n", __func__,
+			hdr->task.tk_pid,
+			hdr->inode->i_sb->s_id,
+			(unsigned long long)NFS_FILEID(hdr->inode),
+			hdr->args.count,
+			(unsigned long long)hdr->args.offset);
+
+		hdr->completion_ops->reschedule_io(hdr);
+		return;
+	}
+
+	if (!test_and_set_bit(NFS_IOHDR_REDO, &hdr->flags)) {
+		dprintk("%s Reset task %5u for i/o through MDS "
+			"(req %s/%llu, %u bytes @ offset %llu)\n", __func__,
+			hdr->task.tk_pid,
+			hdr->inode->i_sb->s_id,
+			(unsigned long long)NFS_FILEID(hdr->inode),
+			hdr->args.count,
+			(unsigned long long)hdr->args.offset);
+
+		trace_pnfs_mds_fallback_write_done(hdr->inode,
+				hdr->args.offset, hdr->args.count,
+				IOMODE_RW, NFS_I(hdr->inode)->layout,
+				hdr->lseg);
+		task->tk_status = pnfs_write_done_resend_to_mds(hdr);
+	}
+}
+
+static void ff_layout_resend_pnfs_read(struct nfs_pgio_header *hdr)
+{
+	u32 idx = hdr->pgio_mirror_idx + 1;
+	u32 new_idx = 0;
+
+	if (ff_layout_choose_any_ds_for_read(hdr->lseg, idx, &new_idx))
+		ff_layout_send_layouterror(hdr->lseg);
+	else
+		pnfs_error_mark_layout_for_return(hdr->inode, hdr->lseg);
+	pnfs_read_resend_pnfs(hdr, new_idx);
+}
+
+static void ff_layout_reset_read(struct nfs_pgio_header *hdr)
+{
+	struct rpc_task *task = &hdr->task;
+
+	pnfs_layoutcommit_inode(hdr->inode, false);
+	pnfs_error_mark_layout_for_return(hdr->inode, hdr->lseg);
+
+	if (!test_and_set_bit(NFS_IOHDR_REDO, &hdr->flags)) {
+		dprintk("%s Reset task %5u for i/o through MDS "
+			"(req %s/%llu, %u bytes @ offset %llu)\n", __func__,
+			hdr->task.tk_pid,
+			hdr->inode->i_sb->s_id,
+			(unsigned long long)NFS_FILEID(hdr->inode),
+			hdr->args.count,
+			(unsigned long long)hdr->args.offset);
+
+		trace_pnfs_mds_fallback_read_done(hdr->inode,
+				hdr->args.offset, hdr->args.count,
+				IOMODE_READ, NFS_I(hdr->inode)->layout,
+				hdr->lseg);
+		task->tk_status = pnfs_read_done_resend_to_mds(hdr);
+	}
+}
+
+static int ff_layout_async_handle_error_v4(struct rpc_task *task,
+					   struct nfs4_state *state,
+					   struct nfs_client *clp,
+					   struct pnfs_layout_segment *lseg,
+					   u32 idx)
+{
+	struct pnfs_layout_hdr *lo = lseg->pls_layout;
+	struct inode *inode = lo->plh_inode;
+	struct nfs4_deviceid_node *devid = FF_LAYOUT_DEVID_NODE(lseg, idx);
+	struct nfs4_slot_table *tbl = &clp->cl_session->fc_slot_table;
+
+	switch (task->tk_status) {
+	case -NFS4ERR_BADSESSION:
+	case -NFS4ERR_BADSLOT:
+	case -NFS4ERR_BAD_HIGH_SLOT:
+	case -NFS4ERR_DEADSESSION:
+	case -NFS4ERR_CONN_NOT_BOUND_TO_SESSION:
+	case -NFS4ERR_SEQ_FALSE_RETRY:
+	case -NFS4ERR_SEQ_MISORDERED:
+		dprintk("%s ERROR %d, Reset session. Exchangeid "
+			"flags 0x%x\n", __func__, task->tk_status,
+			clp->cl_exchange_flags);
+		nfs4_schedule_session_recovery(clp->cl_session, task->tk_status);
+		break;
+	case -NFS4ERR_DELAY:
+	case -NFS4ERR_GRACE:
+		rpc_delay(task, FF_LAYOUT_POLL_RETRY_MAX);
+		break;
+	case -NFS4ERR_RETRY_UNCACHED_REP:
+		break;
+	/* Invalidate Layout errors */
+	case -NFS4ERR_PNFS_NO_LAYOUT:
+	case -ESTALE:           /* mapped NFS4ERR_STALE */
+	case -EBADHANDLE:       /* mapped NFS4ERR_BADHANDLE */
+	case -EISDIR:           /* mapped NFS4ERR_ISDIR */
+	case -NFS4ERR_FHEXPIRED:
+	case -NFS4ERR_WRONG_TYPE:
+		dprintk("%s Invalid layout error %d\n", __func__,
+			task->tk_status);
+		/*
+		 * Destroy layout so new i/o will get a new layout.
+		 * Layout will not be destroyed until all current lseg
+		 * references are put. Mark layout as invalid to resend failed
+		 * i/o and all i/o waiting on the slot table to the MDS until
+		 * layout is destroyed and a new valid layout is obtained.
+		 */
+		pnfs_destroy_layout(NFS_I(inode));
+		rpc_wake_up(&tbl->slot_tbl_waitq);
+		goto reset;
+	/* RPC connection errors */
+	case -ECONNREFUSED:
+	case -EHOSTDOWN:
+	case -EHOSTUNREACH:
+	case -ENETUNREACH:
+	case -EIO:
+	case -ETIMEDOUT:
+	case -EPIPE:
+	case -EPROTO:
+	case -ENODEV:
+		dprintk("%s DS connection error %d\n", __func__,
+			task->tk_status);
+		nfs4_delete_deviceid(devid->ld, devid->nfs_client,
+				&devid->deviceid);
+		rpc_wake_up(&tbl->slot_tbl_waitq);
+		fallthrough;
+	default:
+		if (ff_layout_avoid_mds_available_ds(lseg))
+			return -NFS4ERR_RESET_TO_PNFS;
+reset:
+		dprintk("%s Retry through MDS. Error %d\n", __func__,
+			task->tk_status);
+		return -NFS4ERR_RESET_TO_MDS;
+	}
+	task->tk_status = 0;
+	return -EAGAIN;
+}
+
+/* Retry all errors through either pNFS or MDS except for -EJUKEBOX */
+static int ff_layout_async_handle_error_v3(struct rpc_task *task,
+					   struct pnfs_layout_segment *lseg,
+					   u32 idx)
+{
+	struct nfs4_deviceid_node *devid = FF_LAYOUT_DEVID_NODE(lseg, idx);
+
+	switch (task->tk_status) {
+	/* File access problems. Don't mark the device as unavailable */
+	case -EACCES:
+	case -ESTALE:
+	case -EISDIR:
+	case -EBADHANDLE:
+	case -ELOOP:
+	case -ENOSPC:
+		break;
+	case -EJUKEBOX:
+		nfs_inc_stats(lseg->pls_layout->plh_inode, NFSIOS_DELAY);
+		goto out_retry;
+	default:
+		dprintk("%s DS connection error %d\n", __func__,
+			task->tk_status);
+		nfs4_delete_deviceid(devid->ld, devid->nfs_client,
+				&devid->deviceid);
+	}
+	/* FIXME: Need to prevent infinite looping here. */
+	return -NFS4ERR_RESET_TO_PNFS;
+out_retry:
+	task->tk_status = 0;
+	rpc_restart_call_prepare(task);
+	rpc_delay(task, NFS_JUKEBOX_RETRY_TIME);
+	return -EAGAIN;
+}
+
+static int ff_layout_async_handle_error(struct rpc_task *task,
+					struct nfs4_state *state,
+					struct nfs_client *clp,
+					struct pnfs_layout_segment *lseg,
+					u32 idx)
+{
+	int vers = clp->cl_nfs_mod->rpc_vers->number;
+
+	if (task->tk_status >= 0) {
+		ff_layout_mark_ds_reachable(lseg, idx);
+		return 0;
+	}
+
+	/* Handle the case of an invalid layout segment */
+	if (!pnfs_is_valid_lseg(lseg))
+		return -NFS4ERR_RESET_TO_PNFS;
+
+	switch (vers) {
+	case 3:
+		return ff_layout_async_handle_error_v3(task, lseg, idx);
+	case 4:
+		return ff_layout_async_handle_error_v4(task, state, clp,
+						       lseg, idx);
+	default:
+		/* should never happen */
+		WARN_ON_ONCE(1);
+		return 0;
+	}
+}
+
+static void ff_layout_io_track_ds_error(struct pnfs_layout_segment *lseg,
+					u32 idx, u64 offset, u64 length,
+					u32 *op_status, int opnum, int error)
+{
+	struct nfs4_ff_layout_mirror *mirror;
+	u32 status = *op_status;
+	int err;
+
+	if (status == 0) {
+		switch (error) {
+		case -ETIMEDOUT:
+		case -EPFNOSUPPORT:
+		case -EPROTONOSUPPORT:
+		case -EOPNOTSUPP:
+		case -EINVAL:
+		case -ECONNREFUSED:
+		case -ECONNRESET:
+		case -EHOSTDOWN:
+		case -EHOSTUNREACH:
+		case -ENETUNREACH:
+		case -EADDRINUSE:
+		case -ENOBUFS:
+		case -EPIPE:
+		case -EPERM:
+		case -EPROTO:
+		case -ENODEV:
+			*op_status = status = NFS4ERR_NXIO;
+			break;
+		case -EACCES:
+			*op_status = status = NFS4ERR_ACCESS;
+			break;
+		default:
+			return;
+		}
+	}
+
+	mirror = FF_LAYOUT_COMP(lseg, idx);
+	err = ff_layout_track_ds_error(FF_LAYOUT_FROM_HDR(lseg->pls_layout),
+				       mirror, offset, length, status, opnum,
+				       nfs_io_gfp_mask());
+
+	switch (status) {
+	case NFS4ERR_DELAY:
+	case NFS4ERR_GRACE:
+		break;
+	case NFS4ERR_NXIO:
+		ff_layout_mark_ds_unreachable(lseg, idx);
+		/*
+		 * Don't return the layout if this is a read and we still
+		 * have layouts to try
+		 */
+		if (opnum == OP_READ)
+			break;
+		fallthrough;
+	default:
+		pnfs_error_mark_layout_for_return(lseg->pls_layout->plh_inode,
+						  lseg);
+	}
+
+	dprintk("%s: err %d op %d status %u\n", __func__, err, opnum, status);
+}
+
+/* NFS_PROTO call done callback routines */
+static int ff_layout_read_done_cb(struct rpc_task *task,
+				struct nfs_pgio_header *hdr)
+{
+	int err;
+
+	if (task->tk_status < 0) {
+		ff_layout_io_track_ds_error(hdr->lseg, hdr->pgio_mirror_idx,
+					    hdr->args.offset, hdr->args.count,
+					    &hdr->res.op_status, OP_READ,
+					    task->tk_status);
+		trace_ff_layout_read_error(hdr);
+	}
+
+	err = ff_layout_async_handle_error(task, hdr->args.context->state,
+					   hdr->ds_clp, hdr->lseg,
+					   hdr->pgio_mirror_idx);
+
+	trace_nfs4_pnfs_read(hdr, err);
+	clear_bit(NFS_IOHDR_RESEND_PNFS, &hdr->flags);
+	clear_bit(NFS_IOHDR_RESEND_MDS, &hdr->flags);
+	switch (err) {
+	case -NFS4ERR_RESET_TO_PNFS:
+		set_bit(NFS_IOHDR_RESEND_PNFS, &hdr->flags);
+		return task->tk_status;
+	case -NFS4ERR_RESET_TO_MDS:
+		set_bit(NFS_IOHDR_RESEND_MDS, &hdr->flags);
+		return task->tk_status;
+	case -EAGAIN:
+		goto out_eagain;
+	}
+
+	return 0;
+out_eagain:
+	rpc_restart_call_prepare(task);
+	return -EAGAIN;
+}
+
+static bool
+ff_layout_need_layoutcommit(struct pnfs_layout_segment *lseg)
+{
+	return !(FF_LAYOUT_LSEG(lseg)->flags & FF_FLAGS_NO_LAYOUTCOMMIT);
+}
+
+/*
+ * We reference the rpc_cred of the first WRITE that triggers the need for
+ * a LAYOUTCOMMIT, and use it to send the layoutcommit compound.
+ * rfc5661 is not clear about which credential should be used.
+ *
+ * Flexlayout client should treat DS replied FILE_SYNC as DATA_SYNC, so
+ * to follow http://www.rfc-editor.org/errata_search.php?rfc=5661&eid=2751
+ * we always send layoutcommit after DS writes.
+ */
+static void
+ff_layout_set_layoutcommit(struct inode *inode,
+		struct pnfs_layout_segment *lseg,
+		loff_t end_offset)
+{
+	if (!ff_layout_need_layoutcommit(lseg))
+		return;
+
+	pnfs_set_layoutcommit(inode, lseg, end_offset);
+	dprintk("%s inode %lu pls_end_pos %llu\n", __func__, inode->i_ino,
+		(unsigned long long) NFS_I(inode)->layout->plh_lwb);
+}
+
+static void ff_layout_read_record_layoutstats_start(struct rpc_task *task,
+		struct nfs_pgio_header *hdr)
+{
+	if (test_and_set_bit(NFS_IOHDR_STAT, &hdr->flags))
+		return;
+	nfs4_ff_layout_stat_io_start_read(hdr->inode,
+			FF_LAYOUT_COMP(hdr->lseg, hdr->pgio_mirror_idx),
+			hdr->args.count,
+			task->tk_start);
+}
+
+static void ff_layout_read_record_layoutstats_done(struct rpc_task *task,
+		struct nfs_pgio_header *hdr)
+{
+	if (!test_and_clear_bit(NFS_IOHDR_STAT, &hdr->flags))
+		return;
+	nfs4_ff_layout_stat_io_end_read(task,
+			FF_LAYOUT_COMP(hdr->lseg, hdr->pgio_mirror_idx),
+			hdr->args.count,
+			hdr->res.count);
+	set_bit(NFS_LSEG_LAYOUTRETURN, &hdr->lseg->pls_flags);
+}
+
+static int ff_layout_read_prepare_common(struct rpc_task *task,
+					 struct nfs_pgio_header *hdr)
+{
+	if (unlikely(test_bit(NFS_CONTEXT_BAD, &hdr->args.context->flags))) {
+		rpc_exit(task, -EIO);
+		return -EIO;
+	}
+
+	if (!pnfs_is_valid_lseg(hdr->lseg)) {
+		rpc_exit(task, -EAGAIN);
+		return -EAGAIN;
+	}
+
+	ff_layout_read_record_layoutstats_start(task, hdr);
+	return 0;
+}
+
+/*
+ * Call ops for the async read/write cases
+ * In the case of dense layouts, the offset needs to be reset to its
+ * original value.
+ */
+static void ff_layout_read_prepare_v3(struct rpc_task *task, void *data)
+{
+	struct nfs_pgio_header *hdr = data;
+
+	if (ff_layout_read_prepare_common(task, hdr))
+		return;
+
+	rpc_call_start(task);
+}
+
+static void ff_layout_read_prepare_v4(struct rpc_task *task, void *data)
+{
+	struct nfs_pgio_header *hdr = data;
+
+	if (nfs4_setup_sequence(hdr->ds_clp,
+				&hdr->args.seq_args,
+				&hdr->res.seq_res,
+				task))
+		return;
+
+	ff_layout_read_prepare_common(task, hdr);
+}
+
+static void ff_layout_read_call_done(struct rpc_task *task, void *data)
+{
+	struct nfs_pgio_header *hdr = data;
+
+	if (test_bit(NFS_IOHDR_REDO, &hdr->flags) &&
+	    task->tk_status == 0) {
+		nfs4_sequence_done(task, &hdr->res.seq_res);
+		return;
+	}
+
+	/* Note this may cause RPC to be resent */
+	hdr->mds_ops->rpc_call_done(task, hdr);
+}
+
+static void ff_layout_read_count_stats(struct rpc_task *task, void *data)
+{
+	struct nfs_pgio_header *hdr = data;
+
+	ff_layout_read_record_layoutstats_done(task, hdr);
+	rpc_count_iostats_metrics(task,
+	    &NFS_CLIENT(hdr->inode)->cl_metrics[NFSPROC4_CLNT_READ]);
+}
+
+static void ff_layout_read_release(void *data)
+{
+	struct nfs_pgio_header *hdr = data;
+
+	ff_layout_read_record_layoutstats_done(&hdr->task, hdr);
+	if (test_bit(NFS_IOHDR_RESEND_PNFS, &hdr->flags))
+		ff_layout_resend_pnfs_read(hdr);
+	else if (test_bit(NFS_IOHDR_RESEND_MDS, &hdr->flags))
+		ff_layout_reset_read(hdr);
+	pnfs_generic_rw_release(data);
+}
+
+
+static int ff_layout_write_done_cb(struct rpc_task *task,
+				struct nfs_pgio_header *hdr)
+{
+	loff_t end_offs = 0;
+	int err;
+
+	if (task->tk_status < 0) {
+		ff_layout_io_track_ds_error(hdr->lseg, hdr->pgio_mirror_idx,
+					    hdr->args.offset, hdr->args.count,
+					    &hdr->res.op_status, OP_WRITE,
+					    task->tk_status);
+		trace_ff_layout_write_error(hdr);
+	}
+
+	err = ff_layout_async_handle_error(task, hdr->args.context->state,
+					   hdr->ds_clp, hdr->lseg,
+					   hdr->pgio_mirror_idx);
+
+	trace_nfs4_pnfs_write(hdr, err);
+	clear_bit(NFS_IOHDR_RESEND_PNFS, &hdr->flags);
+	clear_bit(NFS_IOHDR_RESEND_MDS, &hdr->flags);
+	switch (err) {
+	case -NFS4ERR_RESET_TO_PNFS:
+		set_bit(NFS_IOHDR_RESEND_PNFS, &hdr->flags);
+		return task->tk_status;
+	case -NFS4ERR_RESET_TO_MDS:
+		set_bit(NFS_IOHDR_RESEND_MDS, &hdr->flags);
+		return task->tk_status;
+	case -EAGAIN:
+		return -EAGAIN;
+	}
+
+	if (hdr->res.verf->committed == NFS_FILE_SYNC ||
+	    hdr->res.verf->committed == NFS_DATA_SYNC)
+		end_offs = hdr->mds_offset + (loff_t)hdr->res.count;
+
+	/* Note: if the write is unstable, don't set end_offs until commit */
+	ff_layout_set_layoutcommit(hdr->inode, hdr->lseg, end_offs);
+
+	/* zero out fattr since we don't care DS attr at all */
+	hdr->fattr.valid = 0;
+	if (task->tk_status >= 0)
+		nfs_writeback_update_inode(hdr);
+
+	return 0;
+}
+
+static int ff_layout_commit_done_cb(struct rpc_task *task,
+				     struct nfs_commit_data *data)
+{
+	int err;
+
+	if (task->tk_status < 0) {
+		ff_layout_io_track_ds_error(data->lseg, data->ds_commit_index,
+					    data->args.offset, data->args.count,
+					    &data->res.op_status, OP_COMMIT,
+					    task->tk_status);
+		trace_ff_layout_commit_error(data);
+	}
+
+	err = ff_layout_async_handle_error(task, NULL, data->ds_clp,
+					   data->lseg, data->ds_commit_index);
+
+	trace_nfs4_pnfs_commit_ds(data, err);
+	switch (err) {
+	case -NFS4ERR_RESET_TO_PNFS:
+		pnfs_generic_prepare_to_resend_writes(data);
+		return -EAGAIN;
+	case -NFS4ERR_RESET_TO_MDS:
+		pnfs_generic_prepare_to_resend_writes(data);
+		return -EAGAIN;
+	case -EAGAIN:
+		rpc_restart_call_prepare(task);
+		return -EAGAIN;
+	}
+
+	ff_layout_set_layoutcommit(data->inode, data->lseg, data->lwb);
+
+	return 0;
+}
+
+static void ff_layout_write_record_layoutstats_start(struct rpc_task *task,
+		struct nfs_pgio_header *hdr)
+{
+	if (test_and_set_bit(NFS_IOHDR_STAT, &hdr->flags))
+		return;
+	nfs4_ff_layout_stat_io_start_write(hdr->inode,
+			FF_LAYOUT_COMP(hdr->lseg, hdr->pgio_mirror_idx),
+			hdr->args.count,
+			task->tk_start);
+}
+
+static void ff_layout_write_record_layoutstats_done(struct rpc_task *task,
+		struct nfs_pgio_header *hdr)
+{
+	if (!test_and_clear_bit(NFS_IOHDR_STAT, &hdr->flags))
+		return;
+	nfs4_ff_layout_stat_io_end_write(task,
+			FF_LAYOUT_COMP(hdr->lseg, hdr->pgio_mirror_idx),
+			hdr->args.count, hdr->res.count,
+			hdr->res.verf->committed);
+	set_bit(NFS_LSEG_LAYOUTRETURN, &hdr->lseg->pls_flags);
+}
+
+static int ff_layout_write_prepare_common(struct rpc_task *task,
+					  struct nfs_pgio_header *hdr)
+{
+	if (unlikely(test_bit(NFS_CONTEXT_BAD, &hdr->args.context->flags))) {
+		rpc_exit(task, -EIO);
+		return -EIO;
+	}
+
+	if (!pnfs_is_valid_lseg(hdr->lseg)) {
+		rpc_exit(task, -EAGAIN);
+		return -EAGAIN;
+	}
+
+	ff_layout_write_record_layoutstats_start(task, hdr);
+	return 0;
+}
+
+static void ff_layout_write_prepare_v3(struct rpc_task *task, void *data)
+{
+	struct nfs_pgio_header *hdr = data;
+
+	if (ff_layout_write_prepare_common(task, hdr))
+		return;
+
+	rpc_call_start(task);
+}
+
+static void ff_layout_write_prepare_v4(struct rpc_task *task, void *data)
+{
+	struct nfs_pgio_header *hdr = data;
+
+	if (nfs4_setup_sequence(hdr->ds_clp,
+				&hdr->args.seq_args,
+				&hdr->res.seq_res,
+				task))
+		return;
+
+	ff_layout_write_prepare_common(task, hdr);
+}
+
+static void ff_layout_write_call_done(struct rpc_task *task, void *data)
+{
+	struct nfs_pgio_header *hdr = data;
+
+	if (test_bit(NFS_IOHDR_REDO, &hdr->flags) &&
+	    task->tk_status == 0) {
+		nfs4_sequence_done(task, &hdr->res.seq_res);
+		return;
+	}
+
+	/* Note this may cause RPC to be resent */
+	hdr->mds_ops->rpc_call_done(task, hdr);
+}
+
+static void ff_layout_write_count_stats(struct rpc_task *task, void *data)
+{
+	struct nfs_pgio_header *hdr = data;
+
+	ff_layout_write_record_layoutstats_done(task, hdr);
+	rpc_count_iostats_metrics(task,
+	    &NFS_CLIENT(hdr->inode)->cl_metrics[NFSPROC4_CLNT_WRITE]);
+}
+
+static void ff_layout_write_release(void *data)
+{
+	struct nfs_pgio_header *hdr = data;
+
+	ff_layout_write_record_layoutstats_done(&hdr->task, hdr);
+	if (test_bit(NFS_IOHDR_RESEND_PNFS, &hdr->flags)) {
+		ff_layout_send_layouterror(hdr->lseg);
+		ff_layout_reset_write(hdr, true);
+	} else if (test_bit(NFS_IOHDR_RESEND_MDS, &hdr->flags))
+		ff_layout_reset_write(hdr, false);
+	pnfs_generic_rw_release(data);
+}
+
+static void ff_layout_commit_record_layoutstats_start(struct rpc_task *task,
+		struct nfs_commit_data *cdata)
+{
+	if (test_and_set_bit(NFS_IOHDR_STAT, &cdata->flags))
+		return;
+	nfs4_ff_layout_stat_io_start_write(cdata->inode,
+			FF_LAYOUT_COMP(cdata->lseg, cdata->ds_commit_index),
+			0, task->tk_start);
+}
+
+static void ff_layout_commit_record_layoutstats_done(struct rpc_task *task,
+		struct nfs_commit_data *cdata)
+{
+	struct nfs_page *req;
+	__u64 count = 0;
+
+	if (!test_and_clear_bit(NFS_IOHDR_STAT, &cdata->flags))
+		return;
+
+	if (task->tk_status == 0) {
+		list_for_each_entry(req, &cdata->pages, wb_list)
+			count += req->wb_bytes;
+	}
+	nfs4_ff_layout_stat_io_end_write(task,
+			FF_LAYOUT_COMP(cdata->lseg, cdata->ds_commit_index),
+			count, count, NFS_FILE_SYNC);
+	set_bit(NFS_LSEG_LAYOUTRETURN, &cdata->lseg->pls_flags);
+}
+
+static int ff_layout_commit_prepare_common(struct rpc_task *task,
+					   struct nfs_commit_data *cdata)
+{
+	if (!pnfs_is_valid_lseg(cdata->lseg)) {
+		rpc_exit(task, -EAGAIN);
+		return -EAGAIN;
+	}
+
+	ff_layout_commit_record_layoutstats_start(task, cdata);
+	return 0;
+}
+
+static void ff_layout_commit_prepare_v3(struct rpc_task *task, void *data)
+{
+	if (ff_layout_commit_prepare_common(task, data))
+		return;
+
+	rpc_call_start(task);
+}
+
+static void ff_layout_commit_prepare_v4(struct rpc_task *task, void *data)
+{
+	struct nfs_commit_data *wdata = data;
+
+	if (nfs4_setup_sequence(wdata->ds_clp,
+				&wdata->args.seq_args,
+				&wdata->res.seq_res,
+				task))
+		return;
+	ff_layout_commit_prepare_common(task, data);
+}
+
+static void ff_layout_commit_done(struct rpc_task *task, void *data)
+{
+	pnfs_generic_write_commit_done(task, data);
+}
+
+static void ff_layout_commit_count_stats(struct rpc_task *task, void *data)
+{
+	struct nfs_commit_data *cdata = data;
+
+	ff_layout_commit_record_layoutstats_done(task, cdata);
+	rpc_count_iostats_metrics(task,
+	    &NFS_CLIENT(cdata->inode)->cl_metrics[NFSPROC4_CLNT_COMMIT]);
+}
+
+static void ff_layout_commit_release(void *data)
+{
+	struct nfs_commit_data *cdata = data;
+
+	ff_layout_commit_record_layoutstats_done(&cdata->task, cdata);
+	pnfs_generic_commit_release(data);
+}
+
+static const struct rpc_call_ops ff_layout_read_call_ops_v3 = {
+	.rpc_call_prepare = ff_layout_read_prepare_v3,
+	.rpc_call_done = ff_layout_read_call_done,
+	.rpc_count_stats = ff_layout_read_count_stats,
+	.rpc_release = ff_layout_read_release,
+};
+
+static const struct rpc_call_ops ff_layout_read_call_ops_v4 = {
+	.rpc_call_prepare = ff_layout_read_prepare_v4,
+	.rpc_call_done = ff_layout_read_call_done,
+	.rpc_count_stats = ff_layout_read_count_stats,
+	.rpc_release = ff_layout_read_release,
+};
+
+static const struct rpc_call_ops ff_layout_write_call_ops_v3 = {
+	.rpc_call_prepare = ff_layout_write_prepare_v3,
+	.rpc_call_done = ff_layout_write_call_done,
+	.rpc_count_stats = ff_layout_write_count_stats,
+	.rpc_release = ff_layout_write_release,
+};
+
+static const struct rpc_call_ops ff_layout_write_call_ops_v4 = {
+	.rpc_call_prepare = ff_layout_write_prepare_v4,
+	.rpc_call_done = ff_layout_write_call_done,
+	.rpc_count_stats = ff_layout_write_count_stats,
+	.rpc_release = ff_layout_write_release,
+};
+
+static const struct rpc_call_ops ff_layout_commit_call_ops_v3 = {
+	.rpc_call_prepare = ff_layout_commit_prepare_v3,
+	.rpc_call_done = ff_layout_commit_done,
+	.rpc_count_stats = ff_layout_commit_count_stats,
+	.rpc_release = ff_layout_commit_release,
+};
+
+static const struct rpc_call_ops ff_layout_commit_call_ops_v4 = {
+	.rpc_call_prepare = ff_layout_commit_prepare_v4,
+	.rpc_call_done = ff_layout_commit_done,
+	.rpc_count_stats = ff_layout_commit_count_stats,
+	.rpc_release = ff_layout_commit_release,
+};
+
+static enum pnfs_try_status
+ff_layout_read_pagelist(struct nfs_pgio_header *hdr)
+{
+	struct pnfs_layout_segment *lseg = hdr->lseg;
+	struct nfs4_pnfs_ds *ds;
+	struct rpc_clnt *ds_clnt;
+	struct nfs4_ff_layout_mirror *mirror;
+	const struct cred *ds_cred;
+	loff_t offset = hdr->args.offset;
+	u32 idx = hdr->pgio_mirror_idx;
+	int vers;
+	struct nfs_fh *fh;
+
+	dprintk("--> %s ino %lu pgbase %u req %zu@%llu\n",
+		__func__, hdr->inode->i_ino,
+		hdr->args.pgbase, (size_t)hdr->args.count, offset);
+
+	mirror = FF_LAYOUT_COMP(lseg, idx);
+	ds = nfs4_ff_layout_prepare_ds(lseg, mirror, false);
+	if (!ds)
+		goto out_failed;
+
+	ds_clnt = nfs4_ff_find_or_create_ds_client(mirror, ds->ds_clp,
+						   hdr->inode);
+	if (IS_ERR(ds_clnt))
+		goto out_failed;
+
+	ds_cred = ff_layout_get_ds_cred(mirror, &lseg->pls_range, hdr->cred);
+	if (!ds_cred)
+		goto out_failed;
+
+	vers = nfs4_ff_layout_ds_version(mirror);
+
+	dprintk("%s USE DS: %s cl_count %d vers %d\n", __func__,
+		ds->ds_remotestr, refcount_read(&ds->ds_clp->cl_count), vers);
+
+	hdr->pgio_done_cb = ff_layout_read_done_cb;
+	refcount_inc(&ds->ds_clp->cl_count);
+	hdr->ds_clp = ds->ds_clp;
+	fh = nfs4_ff_layout_select_ds_fh(mirror);
+	if (fh)
+		hdr->args.fh = fh;
+
+	nfs4_ff_layout_select_ds_stateid(mirror, &hdr->args.stateid);
+
+	/*
+	 * Note that if we ever decide to split across DSes,
+	 * then we may need to handle dense-like offsets.
+	 */
+	hdr->args.offset = offset;
+	hdr->mds_offset = offset;
+
+	/* Perform an asynchronous read to ds */
+	nfs_initiate_pgio(ds_clnt, hdr, ds_cred, ds->ds_clp->rpc_ops,
+			  vers == 3 ? &ff_layout_read_call_ops_v3 :
+				      &ff_layout_read_call_ops_v4,
+			  0, RPC_TASK_SOFTCONN);
+	put_cred(ds_cred);
+	return PNFS_ATTEMPTED;
+
+out_failed:
+	if (ff_layout_avoid_mds_available_ds(lseg))
+		return PNFS_TRY_AGAIN;
+	trace_pnfs_mds_fallback_read_pagelist(hdr->inode,
+			hdr->args.offset, hdr->args.count,
+			IOMODE_READ, NFS_I(hdr->inode)->layout, lseg);
+	return PNFS_NOT_ATTEMPTED;
+}
+
+/* Perform async writes. */
+static enum pnfs_try_status
+ff_layout_write_pagelist(struct nfs_pgio_header *hdr, int sync)
+{
+	struct pnfs_layout_segment *lseg = hdr->lseg;
+	struct nfs4_pnfs_ds *ds;
+	struct rpc_clnt *ds_clnt;
+	struct nfs4_ff_layout_mirror *mirror;
+	const struct cred *ds_cred;
+	loff_t offset = hdr->args.offset;
+	int vers;
+	struct nfs_fh *fh;
+	u32 idx = hdr->pgio_mirror_idx;
+
+	mirror = FF_LAYOUT_COMP(lseg, idx);
+	ds = nfs4_ff_layout_prepare_ds(lseg, mirror, true);
+	if (!ds)
+		goto out_failed;
+
+	ds_clnt = nfs4_ff_find_or_create_ds_client(mirror, ds->ds_clp,
+						   hdr->inode);
+	if (IS_ERR(ds_clnt))
+		goto out_failed;
+
+	ds_cred = ff_layout_get_ds_cred(mirror, &lseg->pls_range, hdr->cred);
+	if (!ds_cred)
+		goto out_failed;
+
+	vers = nfs4_ff_layout_ds_version(mirror);
+
+	dprintk("%s ino %lu sync %d req %zu@%llu DS: %s cl_count %d vers %d\n",
+		__func__, hdr->inode->i_ino, sync, (size_t) hdr->args.count,
+		offset, ds->ds_remotestr, refcount_read(&ds->ds_clp->cl_count),
+		vers);
+
+	hdr->pgio_done_cb = ff_layout_write_done_cb;
+	refcount_inc(&ds->ds_clp->cl_count);
+	hdr->ds_clp = ds->ds_clp;
+	hdr->ds_commit_idx = idx;
+	fh = nfs4_ff_layout_select_ds_fh(mirror);
+	if (fh)
+		hdr->args.fh = fh;
+
+	nfs4_ff_layout_select_ds_stateid(mirror, &hdr->args.stateid);
+
+	/*
+	 * Note that if we ever decide to split across DSes,
+	 * then we may need to handle dense-like offsets.
+	 */
+	hdr->args.offset = offset;
+
+	/* Perform an asynchronous write */
+	nfs_initiate_pgio(ds_clnt, hdr, ds_cred, ds->ds_clp->rpc_ops,
+			  vers == 3 ? &ff_layout_write_call_ops_v3 :
+				      &ff_layout_write_call_ops_v4,
+			  sync, RPC_TASK_SOFTCONN);
+	put_cred(ds_cred);
+	return PNFS_ATTEMPTED;
+
+out_failed:
+	if (ff_layout_avoid_mds_available_ds(lseg))
+		return PNFS_TRY_AGAIN;
+	trace_pnfs_mds_fallback_write_pagelist(hdr->inode,
+			hdr->args.offset, hdr->args.count,
+			IOMODE_RW, NFS_I(hdr->inode)->layout, lseg);
+	return PNFS_NOT_ATTEMPTED;
+}
+
+static u32 calc_ds_index_from_commit(struct pnfs_layout_segment *lseg, u32 i)
+{
+	return i;
+}
+
+static struct nfs_fh *
+select_ds_fh_from_commit(struct pnfs_layout_segment *lseg, u32 i)
+{
+	struct nfs4_ff_layout_segment *flseg = FF_LAYOUT_LSEG(lseg);
+
+	/* FIXME: Assume that there is only one NFS version available
+	 * for the DS.
+	 */
+	return &flseg->mirror_array[i]->fh_versions[0];
+}
+
+static int ff_layout_initiate_commit(struct nfs_commit_data *data, int how)
+{
+	struct pnfs_layout_segment *lseg = data->lseg;
+	struct nfs4_pnfs_ds *ds;
+	struct rpc_clnt *ds_clnt;
+	struct nfs4_ff_layout_mirror *mirror;
+	const struct cred *ds_cred;
+	u32 idx;
+	int vers, ret;
+	struct nfs_fh *fh;
+
+	if (!lseg || !(pnfs_is_valid_lseg(lseg) ||
+	    test_bit(NFS_LSEG_LAYOUTRETURN, &lseg->pls_flags)))
+		goto out_err;
+
+	idx = calc_ds_index_from_commit(lseg, data->ds_commit_index);
+	mirror = FF_LAYOUT_COMP(lseg, idx);
+	ds = nfs4_ff_layout_prepare_ds(lseg, mirror, true);
+	if (!ds)
+		goto out_err;
+
+	ds_clnt = nfs4_ff_find_or_create_ds_client(mirror, ds->ds_clp,
+						   data->inode);
+	if (IS_ERR(ds_clnt))
+		goto out_err;
+
+	ds_cred = ff_layout_get_ds_cred(mirror, &lseg->pls_range, data->cred);
+	if (!ds_cred)
+		goto out_err;
+
+	vers = nfs4_ff_layout_ds_version(mirror);
+
+	dprintk("%s ino %lu, how %d cl_count %d vers %d\n", __func__,
+		data->inode->i_ino, how, refcount_read(&ds->ds_clp->cl_count),
+		vers);
+	data->commit_done_cb = ff_layout_commit_done_cb;
+	data->cred = ds_cred;
+	refcount_inc(&ds->ds_clp->cl_count);
+	data->ds_clp = ds->ds_clp;
+	fh = select_ds_fh_from_commit(lseg, data->ds_commit_index);
+	if (fh)
+		data->args.fh = fh;
+
+	ret = nfs_initiate_commit(ds_clnt, data, ds->ds_clp->rpc_ops,
+				   vers == 3 ? &ff_layout_commit_call_ops_v3 :
+					       &ff_layout_commit_call_ops_v4,
+				   how, RPC_TASK_SOFTCONN);
+	put_cred(ds_cred);
+	return ret;
+out_err:
+	pnfs_generic_prepare_to_resend_writes(data);
+	pnfs_generic_commit_release(data);
+	return -EAGAIN;
+}
+
+static int
+ff_layout_commit_pagelist(struct inode *inode, struct list_head *mds_pages,
+			   int how, struct nfs_commit_info *cinfo)
+{
+	return pnfs_generic_commit_pagelist(inode, mds_pages, how, cinfo,
+					    ff_layout_initiate_commit);
+}
+
+static bool ff_layout_match_rw(const struct rpc_task *task,
+			       const struct nfs_pgio_header *hdr,
+			       const struct pnfs_layout_segment *lseg)
+{
+	return hdr->lseg == lseg;
+}
+
+static bool ff_layout_match_commit(const struct rpc_task *task,
+				   const struct nfs_commit_data *cdata,
+				   const struct pnfs_layout_segment *lseg)
+{
+	return cdata->lseg == lseg;
+}
+
+static bool ff_layout_match_io(const struct rpc_task *task, const void *data)
+{
+	const struct rpc_call_ops *ops = task->tk_ops;
+
+	if (ops == &ff_layout_read_call_ops_v3 ||
+	    ops == &ff_layout_read_call_ops_v4 ||
+	    ops == &ff_layout_write_call_ops_v3 ||
+	    ops == &ff_layout_write_call_ops_v4)
+		return ff_layout_match_rw(task, task->tk_calldata, data);
+	if (ops == &ff_layout_commit_call_ops_v3 ||
+	    ops == &ff_layout_commit_call_ops_v4)
+		return ff_layout_match_commit(task, task->tk_calldata, data);
+	return false;
+}
+
+static void ff_layout_cancel_io(struct pnfs_layout_segment *lseg)
+{
+	struct nfs4_ff_layout_segment *flseg = FF_LAYOUT_LSEG(lseg);
+	struct nfs4_ff_layout_mirror *mirror;
+	struct nfs4_ff_layout_ds *mirror_ds;
+	struct nfs4_pnfs_ds *ds;
+	struct nfs_client *ds_clp;
+	struct rpc_clnt *clnt;
+	u32 idx;
+
+	for (idx = 0; idx < flseg->mirror_array_cnt; idx++) {
+		mirror = flseg->mirror_array[idx];
+		mirror_ds = mirror->mirror_ds;
+		if (!mirror_ds)
+			continue;
+		ds = mirror->mirror_ds->ds;
+		if (!ds)
+			continue;
+		ds_clp = ds->ds_clp;
+		if (!ds_clp)
+			continue;
+		clnt = ds_clp->cl_rpcclient;
+		if (!clnt)
+			continue;
+		if (!rpc_cancel_tasks(clnt, -EAGAIN, ff_layout_match_io, lseg))
+			continue;
+		rpc_clnt_disconnect(clnt);
+	}
+}
+
+static struct pnfs_ds_commit_info *
+ff_layout_get_ds_info(struct inode *inode)
+{
+	struct pnfs_layout_hdr *layout = NFS_I(inode)->layout;
+
+	if (layout == NULL)
+		return NULL;
+
+	return &FF_LAYOUT_FROM_HDR(layout)->commit_info;
+}
+
+static void
+ff_layout_setup_ds_info(struct pnfs_ds_commit_info *fl_cinfo,
+		struct pnfs_layout_segment *lseg)
+{
+	struct nfs4_ff_layout_segment *flseg = FF_LAYOUT_LSEG(lseg);
+	struct inode *inode = lseg->pls_layout->plh_inode;
+	struct pnfs_commit_array *array, *new;
+
+	new = pnfs_alloc_commit_array(flseg->mirror_array_cnt,
+				      nfs_io_gfp_mask());
+	if (new) {
+		spin_lock(&inode->i_lock);
+		array = pnfs_add_commit_array(fl_cinfo, new, lseg);
+		spin_unlock(&inode->i_lock);
+		if (array != new)
+			pnfs_free_commit_array(new);
+	}
+}
+
+static void
+ff_layout_release_ds_info(struct pnfs_ds_commit_info *fl_cinfo,
+		struct inode *inode)
+{
+	spin_lock(&inode->i_lock);
+	pnfs_generic_ds_cinfo_destroy(fl_cinfo);
+	spin_unlock(&inode->i_lock);
+}
+
+static void
+ff_layout_free_deviceid_node(struct nfs4_deviceid_node *d)
+{
+	nfs4_ff_layout_free_deviceid(container_of(d, struct nfs4_ff_layout_ds,
+						  id_node));
+}
+
+static int ff_layout_encode_ioerr(struct xdr_stream *xdr,
+				  const struct nfs4_layoutreturn_args *args,
+				  const struct nfs4_flexfile_layoutreturn_args *ff_args)
+{
+	__be32 *start;
+
+	start = xdr_reserve_space(xdr, 4);
+	if (unlikely(!start))
+		return -E2BIG;
+
+	*start = cpu_to_be32(ff_args->num_errors);
+	/* This assume we always return _ALL_ layouts */
+	return ff_layout_encode_ds_ioerr(xdr, &ff_args->errors);
+}
+
+static void
+encode_opaque_fixed(struct xdr_stream *xdr, const void *buf, size_t len)
+{
+	WARN_ON_ONCE(xdr_stream_encode_opaque_fixed(xdr, buf, len) < 0);
+}
+
+static void
+ff_layout_encode_ff_iostat_head(struct xdr_stream *xdr,
+			    const nfs4_stateid *stateid,
+			    const struct nfs42_layoutstat_devinfo *devinfo)
+{
+	__be32 *p;
+
+	p = xdr_reserve_space(xdr, 8 + 8);
+	p = xdr_encode_hyper(p, devinfo->offset);
+	p = xdr_encode_hyper(p, devinfo->length);
+	encode_opaque_fixed(xdr, stateid->data, NFS4_STATEID_SIZE);
+	p = xdr_reserve_space(xdr, 4*8);
+	p = xdr_encode_hyper(p, devinfo->read_count);
+	p = xdr_encode_hyper(p, devinfo->read_bytes);
+	p = xdr_encode_hyper(p, devinfo->write_count);
+	p = xdr_encode_hyper(p, devinfo->write_bytes);
+	encode_opaque_fixed(xdr, devinfo->dev_id.data, NFS4_DEVICEID4_SIZE);
+}
+
+static void
+ff_layout_encode_ff_iostat(struct xdr_stream *xdr,
+			    const nfs4_stateid *stateid,
+			    const struct nfs42_layoutstat_devinfo *devinfo)
+{
+	ff_layout_encode_ff_iostat_head(xdr, stateid, devinfo);
+	ff_layout_encode_ff_layoutupdate(xdr, devinfo,
+			devinfo->ld_private.data);
+}
+
+/* report nothing for now */
+static void ff_layout_encode_iostats_array(struct xdr_stream *xdr,
+		const struct nfs4_layoutreturn_args *args,
+		struct nfs4_flexfile_layoutreturn_args *ff_args)
+{
+	__be32 *p;
+	int i;
+
+	p = xdr_reserve_space(xdr, 4);
+	*p = cpu_to_be32(ff_args->num_dev);
+	for (i = 0; i < ff_args->num_dev; i++)
+		ff_layout_encode_ff_iostat(xdr,
+				&args->layout->plh_stateid,
+				&ff_args->devinfo[i]);
+}
+
+static void
+ff_layout_free_iostats_array(struct nfs42_layoutstat_devinfo *devinfo,
+		unsigned int num_entries)
+{
+	unsigned int i;
+
+	for (i = 0; i < num_entries; i++) {
+		if (!devinfo[i].ld_private.ops)
+			continue;
+		if (!devinfo[i].ld_private.ops->free)
+			continue;
+		devinfo[i].ld_private.ops->free(&devinfo[i].ld_private);
+	}
+}
+
+static struct nfs4_deviceid_node *
+ff_layout_alloc_deviceid_node(struct nfs_server *server,
+			      struct pnfs_device *pdev, gfp_t gfp_flags)
+{
+	struct nfs4_ff_layout_ds *dsaddr;
+
+	dsaddr = nfs4_ff_alloc_deviceid_node(server, pdev, gfp_flags);
+	if (!dsaddr)
+		return NULL;
+	return &dsaddr->id_node;
+}
+
+static void
+ff_layout_encode_layoutreturn(struct xdr_stream *xdr,
+		const void *voidargs,
+		const struct nfs4_xdr_opaque_data *ff_opaque)
+{
+	const struct nfs4_layoutreturn_args *args = voidargs;
+	struct nfs4_flexfile_layoutreturn_args *ff_args = ff_opaque->data;
+	struct xdr_buf tmp_buf = {
+		.head = {
+			[0] = {
+				.iov_base = page_address(ff_args->pages[0]),
+			},
+		},
+		.buflen = PAGE_SIZE,
+	};
+	struct xdr_stream tmp_xdr;
+	__be32 *start;
+
+	dprintk("%s: Begin\n", __func__);
+
+	xdr_init_encode(&tmp_xdr, &tmp_buf, NULL, NULL);
+
+	ff_layout_encode_ioerr(&tmp_xdr, args, ff_args);
+	ff_layout_encode_iostats_array(&tmp_xdr, args, ff_args);
+
+	start = xdr_reserve_space(xdr, 4);
+	*start = cpu_to_be32(tmp_buf.len);
+	xdr_write_pages(xdr, ff_args->pages, 0, tmp_buf.len);
+
+	dprintk("%s: Return\n", __func__);
+}
+
+static void
+ff_layout_free_layoutreturn(struct nfs4_xdr_opaque_data *args)
+{
+	struct nfs4_flexfile_layoutreturn_args *ff_args;
+
+	if (!args->data)
+		return;
+	ff_args = args->data;
+	args->data = NULL;
+
+	ff_layout_free_ds_ioerr(&ff_args->errors);
+	ff_layout_free_iostats_array(ff_args->devinfo, ff_args->num_dev);
+
+	put_page(ff_args->pages[0]);
+	kfree(ff_args);
+}
+
+static const struct nfs4_xdr_opaque_ops layoutreturn_ops = {
+	.encode = ff_layout_encode_layoutreturn,
+	.free = ff_layout_free_layoutreturn,
+};
+
+static int
+ff_layout_prepare_layoutreturn(struct nfs4_layoutreturn_args *args)
+{
+	struct nfs4_flexfile_layoutreturn_args *ff_args;
+	struct nfs4_flexfile_layout *ff_layout = FF_LAYOUT_FROM_HDR(args->layout);
+
+	ff_args = kmalloc(sizeof(*ff_args), nfs_io_gfp_mask());
+	if (!ff_args)
+		goto out_nomem;
+	ff_args->pages[0] = alloc_page(nfs_io_gfp_mask());
+	if (!ff_args->pages[0])
+		goto out_nomem_free;
+
+	INIT_LIST_HEAD(&ff_args->errors);
+	ff_args->num_errors = ff_layout_fetch_ds_ioerr(args->layout,
+			&args->range, &ff_args->errors,
+			FF_LAYOUTRETURN_MAXERR);
+
+	spin_lock(&args->inode->i_lock);
+	ff_args->num_dev = ff_layout_mirror_prepare_stats(
+		&ff_layout->generic_hdr, &ff_args->devinfo[0],
+		ARRAY_SIZE(ff_args->devinfo), NFS4_FF_OP_LAYOUTRETURN);
+	spin_unlock(&args->inode->i_lock);
+
+	args->ld_private->ops = &layoutreturn_ops;
+	args->ld_private->data = ff_args;
+	return 0;
+out_nomem_free:
+	kfree(ff_args);
+out_nomem:
+	return -ENOMEM;
+}
+
+#ifdef CONFIG_NFS_V4_2
+void
+ff_layout_send_layouterror(struct pnfs_layout_segment *lseg)
+{
+	struct pnfs_layout_hdr *lo = lseg->pls_layout;
+	struct nfs42_layout_error *errors;
+	LIST_HEAD(head);
+
+	if (!nfs_server_capable(lo->plh_inode, NFS_CAP_LAYOUTERROR))
+		return;
+	ff_layout_fetch_ds_ioerr(lo, &lseg->pls_range, &head, -1);
+	if (list_empty(&head))
+		return;
+
+	errors = kmalloc_array(NFS42_LAYOUTERROR_MAX, sizeof(*errors),
+			       nfs_io_gfp_mask());
+	if (errors != NULL) {
+		const struct nfs4_ff_layout_ds_err *pos;
+		size_t n = 0;
+
+		list_for_each_entry(pos, &head, list) {
+			errors[n].offset = pos->offset;
+			errors[n].length = pos->length;
+			nfs4_stateid_copy(&errors[n].stateid, &pos->stateid);
+			errors[n].errors[0].dev_id = pos->deviceid;
+			errors[n].errors[0].status = pos->status;
+			errors[n].errors[0].opnum = pos->opnum;
+			n++;
+			if (!list_is_last(&pos->list, &head) &&
+			    n < NFS42_LAYOUTERROR_MAX)
+				continue;
+			if (nfs42_proc_layouterror(lseg, errors, n) < 0)
+				break;
+			n = 0;
+		}
+		kfree(errors);
+	}
+	ff_layout_free_ds_ioerr(&head);
+}
+#else
+void
+ff_layout_send_layouterror(struct pnfs_layout_segment *lseg)
+{
+}
+#endif
+
+static int
+ff_layout_ntop4(const struct sockaddr *sap, char *buf, const size_t buflen)
+{
+	const struct sockaddr_in *sin = (struct sockaddr_in *)sap;
+
+	return snprintf(buf, buflen, "%pI4", &sin->sin_addr);
+}
+
+static size_t
+ff_layout_ntop6_noscopeid(const struct sockaddr *sap, char *buf,
+			  const int buflen)
+{
+	const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sap;
+	const struct in6_addr *addr = &sin6->sin6_addr;
+
+	/*
+	 * RFC 4291, Section 2.2.2
+	 *
+	 * Shorthanded ANY address
+	 */
+	if (ipv6_addr_any(addr))
+		return snprintf(buf, buflen, "::");
+
+	/*
+	 * RFC 4291, Section 2.2.2
+	 *
+	 * Shorthanded loopback address
+	 */
+	if (ipv6_addr_loopback(addr))
+		return snprintf(buf, buflen, "::1");
+
+	/*
+	 * RFC 4291, Section 2.2.3
+	 *
+	 * Special presentation address format for mapped v4
+	 * addresses.
+	 */
+	if (ipv6_addr_v4mapped(addr))
+		return snprintf(buf, buflen, "::ffff:%pI4",
+					&addr->s6_addr32[3]);
+
+	/*
+	 * RFC 4291, Section 2.2.1
+	 */
+	return snprintf(buf, buflen, "%pI6c", addr);
+}
+
+/* Derived from rpc_sockaddr2uaddr */
+static void
+ff_layout_encode_netaddr(struct xdr_stream *xdr, struct nfs4_pnfs_ds_addr *da)
+{
+	struct sockaddr *sap = (struct sockaddr *)&da->da_addr;
+	char portbuf[RPCBIND_MAXUADDRPLEN];
+	char addrbuf[RPCBIND_MAXUADDRLEN];
+	unsigned short port;
+	int len, netid_len;
+	__be32 *p;
+
+	switch (sap->sa_family) {
+	case AF_INET:
+		if (ff_layout_ntop4(sap, addrbuf, sizeof(addrbuf)) == 0)
+			return;
+		port = ntohs(((struct sockaddr_in *)sap)->sin_port);
+		break;
+	case AF_INET6:
+		if (ff_layout_ntop6_noscopeid(sap, addrbuf, sizeof(addrbuf)) == 0)
+			return;
+		port = ntohs(((struct sockaddr_in6 *)sap)->sin6_port);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		return;
+	}
+
+	snprintf(portbuf, sizeof(portbuf), ".%u.%u", port >> 8, port & 0xff);
+	len = strlcat(addrbuf, portbuf, sizeof(addrbuf));
+
+	netid_len = strlen(da->da_netid);
+	p = xdr_reserve_space(xdr, 4 + netid_len);
+	xdr_encode_opaque(p, da->da_netid, netid_len);
+
+	p = xdr_reserve_space(xdr, 4 + len);
+	xdr_encode_opaque(p, addrbuf, len);
+}
+
+static void
+ff_layout_encode_nfstime(struct xdr_stream *xdr,
+			 ktime_t t)
+{
+	struct timespec64 ts;
+	__be32 *p;
+
+	p = xdr_reserve_space(xdr, 12);
+	ts = ktime_to_timespec64(t);
+	p = xdr_encode_hyper(p, ts.tv_sec);
+	*p++ = cpu_to_be32(ts.tv_nsec);
+}
+
+static void
+ff_layout_encode_io_latency(struct xdr_stream *xdr,
+			    struct nfs4_ff_io_stat *stat)
+{
+	__be32 *p;
+
+	p = xdr_reserve_space(xdr, 5 * 8);
+	p = xdr_encode_hyper(p, stat->ops_requested);
+	p = xdr_encode_hyper(p, stat->bytes_requested);
+	p = xdr_encode_hyper(p, stat->ops_completed);
+	p = xdr_encode_hyper(p, stat->bytes_completed);
+	p = xdr_encode_hyper(p, stat->bytes_not_delivered);
+	ff_layout_encode_nfstime(xdr, stat->total_busy_time);
+	ff_layout_encode_nfstime(xdr, stat->aggregate_completion_time);
+}
+
+static void
+ff_layout_encode_ff_layoutupdate(struct xdr_stream *xdr,
+			      const struct nfs42_layoutstat_devinfo *devinfo,
+			      struct nfs4_ff_layout_mirror *mirror)
+{
+	struct nfs4_pnfs_ds_addr *da;
+	struct nfs4_pnfs_ds *ds = mirror->mirror_ds->ds;
+	struct nfs_fh *fh = &mirror->fh_versions[0];
+	__be32 *p;
+
+	da = list_first_entry(&ds->ds_addrs, struct nfs4_pnfs_ds_addr, da_node);
+	dprintk("%s: DS %s: encoding address %s\n",
+		__func__, ds->ds_remotestr, da->da_remotestr);
+	/* netaddr4 */
+	ff_layout_encode_netaddr(xdr, da);
+	/* nfs_fh4 */
+	p = xdr_reserve_space(xdr, 4 + fh->size);
+	xdr_encode_opaque(p, fh->data, fh->size);
+	/* ff_io_latency4 read */
+	spin_lock(&mirror->lock);
+	ff_layout_encode_io_latency(xdr, &mirror->read_stat.io_stat);
+	/* ff_io_latency4 write */
+	ff_layout_encode_io_latency(xdr, &mirror->write_stat.io_stat);
+	spin_unlock(&mirror->lock);
+	/* nfstime4 */
+	ff_layout_encode_nfstime(xdr, ktime_sub(ktime_get(), mirror->start_time));
+	/* bool */
+	p = xdr_reserve_space(xdr, 4);
+	*p = cpu_to_be32(false);
+}
+
+static void
+ff_layout_encode_layoutstats(struct xdr_stream *xdr, const void *args,
+			     const struct nfs4_xdr_opaque_data *opaque)
+{
+	struct nfs42_layoutstat_devinfo *devinfo = container_of(opaque,
+			struct nfs42_layoutstat_devinfo, ld_private);
+	__be32 *start;
+
+	/* layoutupdate length */
+	start = xdr_reserve_space(xdr, 4);
+	ff_layout_encode_ff_layoutupdate(xdr, devinfo, opaque->data);
+
+	*start = cpu_to_be32((xdr->p - start - 1) * 4);
+}
+
+static void
+ff_layout_free_layoutstats(struct nfs4_xdr_opaque_data *opaque)
+{
+	struct nfs4_ff_layout_mirror *mirror = opaque->data;
+
+	ff_layout_put_mirror(mirror);
+}
+
+static const struct nfs4_xdr_opaque_ops layoutstat_ops = {
+	.encode = ff_layout_encode_layoutstats,
+	.free	= ff_layout_free_layoutstats,
+};
+
+static int
+ff_layout_mirror_prepare_stats(struct pnfs_layout_hdr *lo,
+			       struct nfs42_layoutstat_devinfo *devinfo,
+			       int dev_limit, enum nfs4_ff_op_type type)
+{
+	struct nfs4_flexfile_layout *ff_layout = FF_LAYOUT_FROM_HDR(lo);
+	struct nfs4_ff_layout_mirror *mirror;
+	struct nfs4_deviceid_node *dev;
+	int i = 0;
+
+	list_for_each_entry(mirror, &ff_layout->mirrors, mirrors) {
+		if (i >= dev_limit)
+			break;
+		if (IS_ERR_OR_NULL(mirror->mirror_ds))
+			continue;
+		if (!test_and_clear_bit(NFS4_FF_MIRROR_STAT_AVAIL,
+					&mirror->flags) &&
+		    type != NFS4_FF_OP_LAYOUTRETURN)
+			continue;
+		/* mirror refcount put in cleanup_layoutstats */
+		if (!refcount_inc_not_zero(&mirror->ref))
+			continue;
+		dev = &mirror->mirror_ds->id_node; 
+		memcpy(&devinfo->dev_id, &dev->deviceid, NFS4_DEVICEID4_SIZE);
+		devinfo->offset = 0;
+		devinfo->length = NFS4_MAX_UINT64;
+		spin_lock(&mirror->lock);
+		devinfo->read_count = mirror->read_stat.io_stat.ops_completed;
+		devinfo->read_bytes = mirror->read_stat.io_stat.bytes_completed;
+		devinfo->write_count = mirror->write_stat.io_stat.ops_completed;
+		devinfo->write_bytes = mirror->write_stat.io_stat.bytes_completed;
+		spin_unlock(&mirror->lock);
+		devinfo->layout_type = LAYOUT_FLEX_FILES;
+		devinfo->ld_private.ops = &layoutstat_ops;
+		devinfo->ld_private.data = mirror;
+
+		devinfo++;
+		i++;
+	}
+	return i;
+}
+
+static int ff_layout_prepare_layoutstats(struct nfs42_layoutstat_args *args)
+{
+	struct pnfs_layout_hdr *lo;
+	struct nfs4_flexfile_layout *ff_layout;
+	const int dev_count = PNFS_LAYOUTSTATS_MAXDEV;
+
+	/* For now, send at most PNFS_LAYOUTSTATS_MAXDEV statistics */
+	args->devinfo = kmalloc_array(dev_count, sizeof(*args->devinfo),
+				      nfs_io_gfp_mask());
+	if (!args->devinfo)
+		return -ENOMEM;
+
+	spin_lock(&args->inode->i_lock);
+	lo = NFS_I(args->inode)->layout;
+	if (lo && pnfs_layout_is_valid(lo)) {
+		ff_layout = FF_LAYOUT_FROM_HDR(lo);
+		args->num_dev = ff_layout_mirror_prepare_stats(
+			&ff_layout->generic_hdr, &args->devinfo[0], dev_count,
+			NFS4_FF_OP_LAYOUTSTATS);
+	} else
+		args->num_dev = 0;
+	spin_unlock(&args->inode->i_lock);
+	if (!args->num_dev) {
+		kfree(args->devinfo);
+		args->devinfo = NULL;
+		return -ENOENT;
+	}
+
+	return 0;
+}
+
+static int
+ff_layout_set_layoutdriver(struct nfs_server *server,
+		const struct nfs_fh *dummy)
+{
+#if IS_ENABLED(CONFIG_NFS_V4_2)
+	server->caps |= NFS_CAP_LAYOUTSTATS;
+#endif
+	return 0;
+}
+
+static const struct pnfs_commit_ops ff_layout_commit_ops = {
+	.setup_ds_info		= ff_layout_setup_ds_info,
+	.release_ds_info	= ff_layout_release_ds_info,
+	.mark_request_commit	= pnfs_layout_mark_request_commit,
+	.clear_request_commit	= pnfs_generic_clear_request_commit,
+	.scan_commit_lists	= pnfs_generic_scan_commit_lists,
+	.recover_commit_reqs	= pnfs_generic_recover_commit_reqs,
+	.commit_pagelist	= ff_layout_commit_pagelist,
+};
+
+static struct pnfs_layoutdriver_type flexfilelayout_type = {
+	.id			= LAYOUT_FLEX_FILES,
+	.name			= "LAYOUT_FLEX_FILES",
+	.owner			= THIS_MODULE,
+	.flags			= PNFS_LAYOUTGET_ON_OPEN,
+	.max_layoutget_response	= 4096, /* 1 page or so... */
+	.set_layoutdriver	= ff_layout_set_layoutdriver,
+	.alloc_layout_hdr	= ff_layout_alloc_layout_hdr,
+	.free_layout_hdr	= ff_layout_free_layout_hdr,
+	.alloc_lseg		= ff_layout_alloc_lseg,
+	.free_lseg		= ff_layout_free_lseg,
+	.add_lseg		= ff_layout_add_lseg,
+	.pg_read_ops		= &ff_layout_pg_read_ops,
+	.pg_write_ops		= &ff_layout_pg_write_ops,
+	.get_ds_info		= ff_layout_get_ds_info,
+	.free_deviceid_node	= ff_layout_free_deviceid_node,
+	.read_pagelist		= ff_layout_read_pagelist,
+	.write_pagelist		= ff_layout_write_pagelist,
+	.alloc_deviceid_node    = ff_layout_alloc_deviceid_node,
+	.prepare_layoutreturn   = ff_layout_prepare_layoutreturn,
+	.sync			= pnfs_nfs_generic_sync,
+	.prepare_layoutstats	= ff_layout_prepare_layoutstats,
+	.cancel_io		= ff_layout_cancel_io,
+};
+
+static int __init nfs4flexfilelayout_init(void)
+{
+	printk(KERN_INFO "%s: NFSv4 Flexfile Layout Driver Registering...\n",
+	       __func__);
+	return pnfs_register_layoutdriver(&flexfilelayout_type);
+}
+
+static void __exit nfs4flexfilelayout_exit(void)
+{
+	printk(KERN_INFO "%s: NFSv4 Flexfile Layout Driver Unregistering...\n",
+	       __func__);
+	pnfs_unregister_layoutdriver(&flexfilelayout_type);
+}
+
+MODULE_ALIAS("nfs-layouttype4-4");
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("The NFSv4 flexfile layout driver");
+
+module_init(nfs4flexfilelayout_init);
+module_exit(nfs4flexfilelayout_exit);
+
+module_param(io_maxretrans, ushort, 0644);
+MODULE_PARM_DESC(io_maxretrans, "The  number of times the NFSv4.1 client "
+			"retries an I/O request before returning an error. ");
diff --git a/fs/nfs/flexfilelayout/flexfilelayout.h b/fs/nfs/flexfilelayout/flexfilelayout.h
new file mode 100644
index 0000000000..354a031c69
--- /dev/null
+++ b/fs/nfs/flexfilelayout/flexfilelayout.h
@@ -0,0 +1,226 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * NFSv4 flexfile layout driver data structures.
+ *
+ * Copyright (c) 2014, Primary Data, Inc. All rights reserved.
+ *
+ * Tao Peng <bergwolf@primarydata.com>
+ */
+
+#ifndef FS_NFS_NFS4FLEXFILELAYOUT_H
+#define FS_NFS_NFS4FLEXFILELAYOUT_H
+
+#define FF_FLAGS_NO_LAYOUTCOMMIT 1
+#define FF_FLAGS_NO_IO_THRU_MDS  2
+#define FF_FLAGS_NO_READ_IO      4
+
+#include <linux/refcount.h>
+#include "../pnfs.h"
+
+/* XXX: Let's filter out insanely large mirror count for now to avoid oom
+ * due to network error etc. */
+#define NFS4_FLEXFILE_LAYOUT_MAX_MIRROR_CNT 4096
+
+/* LAYOUTSTATS report interval in ms */
+#define FF_LAYOUTSTATS_REPORT_INTERVAL (60000L)
+#define FF_LAYOUTSTATS_MAXDEV 4
+
+struct nfs4_ff_ds_version {
+	u32				version;
+	u32				minor_version;
+	u32				rsize;
+	u32				wsize;
+	bool				tightly_coupled;
+};
+
+/* chained in global deviceid hlist */
+struct nfs4_ff_layout_ds {
+	struct nfs4_deviceid_node	id_node;
+	u32				ds_versions_cnt;
+	struct nfs4_ff_ds_version	*ds_versions;
+	struct nfs4_pnfs_ds		*ds;
+};
+
+struct nfs4_ff_layout_ds_err {
+	struct list_head		list; /* linked in mirror error_list */
+	u64				offset;
+	u64				length;
+	int				status;
+	enum nfs_opnum4			opnum;
+	nfs4_stateid			stateid;
+	struct nfs4_deviceid		deviceid;
+};
+
+struct nfs4_ff_io_stat {
+	__u64				ops_requested;
+	__u64				bytes_requested;
+	__u64				ops_completed;
+	__u64				bytes_completed;
+	__u64				bytes_not_delivered;
+	ktime_t				total_busy_time;
+	ktime_t				aggregate_completion_time;
+};
+
+struct nfs4_ff_busy_timer {
+	ktime_t start_time;
+	atomic_t n_ops;
+};
+
+struct nfs4_ff_layoutstat {
+	struct nfs4_ff_io_stat io_stat;
+	struct nfs4_ff_busy_timer busy_timer;
+};
+
+struct nfs4_ff_layout_mirror {
+	struct pnfs_layout_hdr		*layout;
+	struct list_head		mirrors;
+	u32				ds_count;
+	u32				efficiency;
+	struct nfs4_deviceid		devid;
+	struct nfs4_ff_layout_ds	*mirror_ds;
+	u32				fh_versions_cnt;
+	struct nfs_fh			*fh_versions;
+	nfs4_stateid			stateid;
+	const struct cred __rcu		*ro_cred;
+	const struct cred __rcu		*rw_cred;
+	refcount_t			ref;
+	spinlock_t			lock;
+	unsigned long			flags;
+	struct nfs4_ff_layoutstat	read_stat;
+	struct nfs4_ff_layoutstat	write_stat;
+	ktime_t				start_time;
+	u32				report_interval;
+};
+
+#define NFS4_FF_MIRROR_STAT_AVAIL	(0)
+
+struct nfs4_ff_layout_segment {
+	struct pnfs_layout_segment	generic_hdr;
+	u64				stripe_unit;
+	u32				flags;
+	u32				mirror_array_cnt;
+	struct nfs4_ff_layout_mirror	*mirror_array[];
+};
+
+struct nfs4_flexfile_layout {
+	struct pnfs_layout_hdr generic_hdr;
+	struct pnfs_ds_commit_info commit_info;
+	struct list_head	mirrors;
+	struct list_head	error_list; /* nfs4_ff_layout_ds_err */
+	ktime_t			last_report_time; /* Layoutstat report times */
+};
+
+struct nfs4_flexfile_layoutreturn_args {
+	struct list_head errors;
+	struct nfs42_layoutstat_devinfo devinfo[FF_LAYOUTSTATS_MAXDEV];
+	unsigned int num_errors;
+	unsigned int num_dev;
+	struct page *pages[1];
+};
+
+static inline struct nfs4_flexfile_layout *
+FF_LAYOUT_FROM_HDR(struct pnfs_layout_hdr *lo)
+{
+	return container_of(lo, struct nfs4_flexfile_layout, generic_hdr);
+}
+
+static inline struct nfs4_ff_layout_segment *
+FF_LAYOUT_LSEG(struct pnfs_layout_segment *lseg)
+{
+	return container_of(lseg,
+			    struct nfs4_ff_layout_segment,
+			    generic_hdr);
+}
+
+static inline struct nfs4_ff_layout_ds *
+FF_LAYOUT_MIRROR_DS(struct nfs4_deviceid_node *node)
+{
+	return container_of(node, struct nfs4_ff_layout_ds, id_node);
+}
+
+static inline struct nfs4_ff_layout_mirror *
+FF_LAYOUT_COMP(struct pnfs_layout_segment *lseg, u32 idx)
+{
+	struct nfs4_ff_layout_segment *fls = FF_LAYOUT_LSEG(lseg);
+
+	if (idx < fls->mirror_array_cnt)
+		return fls->mirror_array[idx];
+	return NULL;
+}
+
+static inline struct nfs4_deviceid_node *
+FF_LAYOUT_DEVID_NODE(struct pnfs_layout_segment *lseg, u32 idx)
+{
+	struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, idx);
+
+	if (mirror != NULL) {
+		struct nfs4_ff_layout_ds *mirror_ds = mirror->mirror_ds;
+
+		if (!IS_ERR_OR_NULL(mirror_ds))
+			return &mirror_ds->id_node;
+	}
+	return NULL;
+}
+
+static inline u32
+FF_LAYOUT_MIRROR_COUNT(struct pnfs_layout_segment *lseg)
+{
+	return FF_LAYOUT_LSEG(lseg)->mirror_array_cnt;
+}
+
+static inline bool
+ff_layout_no_fallback_to_mds(struct pnfs_layout_segment *lseg)
+{
+	return FF_LAYOUT_LSEG(lseg)->flags & FF_FLAGS_NO_IO_THRU_MDS;
+}
+
+static inline bool
+ff_layout_no_read_on_rw(struct pnfs_layout_segment *lseg)
+{
+	return FF_LAYOUT_LSEG(lseg)->flags & FF_FLAGS_NO_READ_IO;
+}
+
+static inline int
+nfs4_ff_layout_ds_version(const struct nfs4_ff_layout_mirror *mirror)
+{
+	return mirror->mirror_ds->ds_versions[0].version;
+}
+
+struct nfs4_ff_layout_ds *
+nfs4_ff_alloc_deviceid_node(struct nfs_server *server, struct pnfs_device *pdev,
+			    gfp_t gfp_flags);
+void nfs4_ff_layout_put_deviceid(struct nfs4_ff_layout_ds *mirror_ds);
+void nfs4_ff_layout_free_deviceid(struct nfs4_ff_layout_ds *mirror_ds);
+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);
+void ff_layout_send_layouterror(struct pnfs_layout_segment *lseg);
+int ff_layout_encode_ds_ioerr(struct xdr_stream *xdr, const struct list_head *head);
+void ff_layout_free_ds_ioerr(struct list_head *head);
+unsigned int ff_layout_fetch_ds_ioerr(struct pnfs_layout_hdr *lo,
+		const struct pnfs_layout_range *range,
+		struct list_head *head,
+		unsigned int maxnum);
+struct nfs_fh *
+nfs4_ff_layout_select_ds_fh(struct nfs4_ff_layout_mirror *mirror);
+void
+nfs4_ff_layout_select_ds_stateid(const struct nfs4_ff_layout_mirror *mirror,
+		nfs4_stateid *stateid);
+
+struct nfs4_pnfs_ds *
+nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg,
+			  struct nfs4_ff_layout_mirror *mirror,
+			  bool fail_return);
+
+struct rpc_clnt *
+nfs4_ff_find_or_create_ds_client(struct nfs4_ff_layout_mirror *mirror,
+				 struct nfs_client *ds_clp,
+				 struct inode *inode);
+const struct cred *ff_layout_get_ds_cred(struct nfs4_ff_layout_mirror *mirror,
+					 const struct pnfs_layout_range *range,
+					 const struct cred *mdscred);
+bool ff_layout_avoid_mds_available_ds(struct pnfs_layout_segment *lseg);
+bool ff_layout_avoid_read_on_rw(struct pnfs_layout_segment *lseg);
+
+#endif /* FS_NFS_NFS4FLEXFILELAYOUT_H */
diff --git a/fs/nfs/flexfilelayout/flexfilelayoutdev.c b/fs/nfs/flexfilelayout/flexfilelayoutdev.c
new file mode 100644
index 0000000000..e028f5a0ef
--- /dev/null
+++ b/fs/nfs/flexfilelayout/flexfilelayoutdev.c
@@ -0,0 +1,621 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * 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 = NFS_DEF_TCP_TIMEO;
+static unsigned int dataserver_retrans;
+
+static bool ff_layout_has_available_ds(struct pnfs_layout_segment *lseg);
+
+void nfs4_ff_layout_put_deviceid(struct nfs4_ff_layout_ds *mirror_ds)
+{
+	if (!IS_ERR_OR_NULL(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->ds_versions);
+	kfree_rcu(mirror_ds, id_node.rcu);
+}
+
+/* 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_page(&stream, scratch);
+
+	/* 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 = kcalloc(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_io_size(be32_to_cpup(p++),
+						   server->nfs_client->cl_proto);
+		ds_versions[i].wsize = nfs_io_size(be32_to_cpup(p++),
+						   server->nfs_client->cl_proto);
+		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;
+
+		/*
+		 * check for valid major/minor combination.
+		 * currently we support dataserver which talk:
+		 *   v3, v4.0, v4.1, v4.2
+		 */
+		if (!((ds_versions[i].version == 3 && ds_versions[i].minor_version == 0) ||
+			(ds_versions[i].version == 4 && ds_versions[i].minor_version < 3))) {
+			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 void extend_ds_error(struct nfs4_ff_layout_ds_err *err,
+			    u64 offset, u64 length)
+{
+	u64 end;
+
+	end = max_t(u64, pnfs_end_offset(err->offset, err->length),
+		    pnfs_end_offset(offset, length));
+	err->offset = min_t(u64, err->offset, offset);
+	err->length = end - err->offset;
+}
+
+static int
+ff_ds_error_match(const struct nfs4_ff_layout_ds_err *e1,
+		const struct nfs4_ff_layout_ds_err *e2)
+{
+	int ret;
+
+	if (e1->opnum != e2->opnum)
+		return e1->opnum < e2->opnum ? -1 : 1;
+	if (e1->status != e2->status)
+		return e1->status < e2->status ? -1 : 1;
+	ret = memcmp(e1->stateid.data, e2->stateid.data,
+			sizeof(e1->stateid.data));
+	if (ret != 0)
+		return ret;
+	ret = memcmp(&e1->deviceid, &e2->deviceid, sizeof(e1->deviceid));
+	if (ret != 0)
+		return ret;
+	if (pnfs_end_offset(e1->offset, e1->length) < e2->offset)
+		return -1;
+	if (e1->offset > pnfs_end_offset(e2->offset, e2->length))
+		return 1;
+	/* If ranges overlap or are contiguous, they are the same */
+	return 0;
+}
+
+static void
+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, *tmp;
+	struct list_head *head = &flo->error_list;
+	int match;
+
+	/* Do insertion sort w/ merges */
+	list_for_each_entry_safe(err, tmp, &flo->error_list, list) {
+		match = ff_ds_error_match(err, dserr);
+		if (match < 0)
+			continue;
+		if (match > 0) {
+			/* Add entry "dserr" _before_ entry "err" */
+			head = &err->list;
+			break;
+		}
+		/* Entries match, so merge "err" into "dserr" */
+		extend_ds_error(dserr, err->offset, err->length);
+		list_replace(&err->list, &dserr->list);
+		kfree(err);
+		return;
+	}
+
+	list_add_tail(&dserr->list, head);
+}
+
+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;
+
+	if (status == 0)
+		return 0;
+
+	if (IS_ERR_OR_NULL(mirror->mirror_ds))
+		return -EINVAL;
+
+	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);
+	ff_layout_add_ds_error_locked(flo, dserr);
+	spin_unlock(&flo->generic_hdr.plh_inode->i_lock);
+	return 0;
+}
+
+static const struct cred *
+ff_layout_get_mirror_cred(struct nfs4_ff_layout_mirror *mirror, u32 iomode)
+{
+	const struct cred *cred, __rcu **pcred;
+
+	if (iomode == IOMODE_READ)
+		pcred = &mirror->ro_cred;
+	else
+		pcred = &mirror->rw_cred;
+
+	rcu_read_lock();
+	do {
+		cred = rcu_dereference(*pcred);
+		if (!cred)
+			break;
+
+		cred = get_cred_rcu(cred);
+	} while(!cred);
+	rcu_read_unlock();
+	return cred;
+}
+
+struct nfs_fh *
+nfs4_ff_layout_select_ds_fh(struct nfs4_ff_layout_mirror *mirror)
+{
+	/* FIXME: For now assume there is only 1 version available for the DS */
+	return &mirror->fh_versions[0];
+}
+
+void
+nfs4_ff_layout_select_ds_stateid(const struct nfs4_ff_layout_mirror *mirror,
+		nfs4_stateid *stateid)
+{
+	if (nfs4_ff_layout_ds_version(mirror) == 4)
+		nfs4_stateid_copy(stateid, &mirror->stateid);
+}
+
+static bool
+ff_layout_init_mirror_ds(struct pnfs_layout_hdr *lo,
+			 struct nfs4_ff_layout_mirror *mirror)
+{
+	if (mirror == NULL)
+		goto outerr;
+	if (mirror->mirror_ds == NULL) {
+		struct nfs4_deviceid_node *node;
+		struct nfs4_ff_layout_ds *mirror_ds = ERR_PTR(-ENODEV);
+
+		node = nfs4_find_get_deviceid(NFS_SERVER(lo->plh_inode),
+				&mirror->devid, lo->plh_lc_cred,
+				GFP_KERNEL);
+		if (node)
+			mirror_ds = FF_LAYOUT_MIRROR_DS(node);
+
+		/* check for race with another call to this function */
+		if (cmpxchg(&mirror->mirror_ds, NULL, mirror_ds) &&
+		    mirror_ds != ERR_PTR(-ENODEV))
+			nfs4_put_deviceid_node(node);
+	}
+
+	if (IS_ERR(mirror->mirror_ds))
+		goto outerr;
+
+	return true;
+outerr:
+	return false;
+}
+
+/**
+ * nfs4_ff_layout_prepare_ds - prepare a DS connection for an RPC call
+ * @lseg: the layout segment we're operating on
+ * @mirror: layout mirror describing the DS to use
+ * @fail_return: return layout on connect failure?
+ *
+ * Try to prepare a DS connection to accept an RPC call. This involves
+ * selecting a mirror to use and connecting the client to it if it's not
+ * already connected.
+ *
+ * Since we only need a single functioning mirror to satisfy a read, we don't
+ * want to return the layout if there is one. For writes though, any down
+ * mirror should result in a LAYOUTRETURN. @fail_return is how we distinguish
+ * between the two cases.
+ *
+ * Returns a pointer to a connected DS object on success or NULL on failure.
+ */
+struct nfs4_pnfs_ds *
+nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg,
+			  struct nfs4_ff_layout_mirror *mirror,
+			  bool fail_return)
+{
+	struct nfs4_pnfs_ds *ds = NULL;
+	struct inode *ino = lseg->pls_layout->plh_inode;
+	struct nfs_server *s = NFS_SERVER(ino);
+	unsigned int max_payload;
+	int status;
+
+	if (!ff_layout_init_mirror_ds(lseg->pls_layout, mirror))
+		goto noconnect;
+
+	ds = mirror->mirror_ds->ds;
+	if (READ_ONCE(ds->ds_clp))
+		goto out;
+	/* matching smp_wmb() in _nfs4_pnfs_v3/4_ds_connect */
+	smp_rmb();
+
+	/* FIXME: For now we assume the server sent only one version of NFS
+	 * to use for the DS.
+	 */
+	status = nfs4_pnfs_ds_connect(s, ds, &mirror->mirror_ds->id_node,
+			     dataserver_timeo, dataserver_retrans,
+			     mirror->mirror_ds->ds_versions[0].version,
+			     mirror->mirror_ds->ds_versions[0].minor_version);
+
+	/* connect success, check rsize/wsize limit */
+	if (!status) {
+		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;
+		goto out;
+	}
+noconnect:
+	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);
+	ff_layout_send_layouterror(lseg);
+	if (fail_return || !ff_layout_has_available_ds(lseg))
+		pnfs_error_mark_layout_for_return(ino, lseg);
+	ds = NULL;
+out:
+	return ds;
+}
+
+const struct cred *
+ff_layout_get_ds_cred(struct nfs4_ff_layout_mirror *mirror,
+		      const struct pnfs_layout_range *range,
+		      const struct cred *mdscred)
+{
+	const struct cred *cred;
+
+	if (mirror && !mirror->mirror_ds->ds_versions[0].tightly_coupled) {
+		cred = ff_layout_get_mirror_cred(mirror, range->iomode);
+		if (!cred)
+			cred = get_cred(mdscred);
+	} else {
+		cred = get_cred(mdscred);
+	}
+	return cred;
+}
+
+/**
+ * nfs4_ff_find_or_create_ds_client - Find or create a DS rpc client
+ * @mirror: pointer to the mirror
+ * @ds_clp: nfs_client for the DS
+ * @inode: pointer to inode
+ *
+ * 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 nfs4_ff_layout_mirror *mirror,
+				 struct nfs_client *ds_clp, struct inode *inode)
+{
+	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();
+	}
+}
+
+void ff_layout_free_ds_ioerr(struct list_head *head)
+{
+	struct nfs4_ff_layout_ds_err *err;
+
+	while (!list_empty(head)) {
+		err = list_first_entry(head,
+				struct nfs4_ff_layout_ds_err,
+				list);
+		list_del(&err->list);
+		kfree(err);
+	}
+}
+
+/* called with inode i_lock held */
+int ff_layout_encode_ds_ioerr(struct xdr_stream *xdr, const struct list_head *head)
+{
+	struct nfs4_ff_layout_ds_err *err;
+	__be32 *p;
+
+	list_for_each_entry(err, head, list) {
+		/* offset(8) + length(8) + stateid(NFS4_STATEID_SIZE)
+		 * + array length + deviceid(NFS4_DEVICEID4_SIZE)
+		 * + status(4) + opnum(4)
+		 */
+		p = xdr_reserve_space(xdr,
+				28 + 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);
+		/* Encode 1 error */
+		*p++ = cpu_to_be32(1);
+		p = xdr_encode_opaque_fixed(p, &err->deviceid,
+					    NFS4_DEVICEID4_SIZE);
+		*p++ = cpu_to_be32(err->status);
+		*p++ = cpu_to_be32(err->opnum);
+		dprintk("%s: offset %llu length %llu status %d op %d\n",
+			__func__, err->offset, err->length, err->status,
+			err->opnum);
+	}
+
+	return 0;
+}
+
+static
+unsigned int do_layout_fetch_ds_ioerr(struct pnfs_layout_hdr *lo,
+				      const struct pnfs_layout_range *range,
+				      struct list_head *head,
+				      unsigned int maxnum)
+{
+	struct nfs4_flexfile_layout *flo = FF_LAYOUT_FROM_HDR(lo);
+	struct inode *inode = lo->plh_inode;
+	struct nfs4_ff_layout_ds_err *err, *n;
+	unsigned int ret = 0;
+
+	spin_lock(&inode->i_lock);
+	list_for_each_entry_safe(err, n, &flo->error_list, list) {
+		if (!pnfs_is_range_intersecting(err->offset,
+				pnfs_end_offset(err->offset, err->length),
+				range->offset,
+				pnfs_end_offset(range->offset, range->length)))
+			continue;
+		if (!maxnum)
+			break;
+		list_move(&err->list, head);
+		maxnum--;
+		ret++;
+	}
+	spin_unlock(&inode->i_lock);
+	return ret;
+}
+
+unsigned int ff_layout_fetch_ds_ioerr(struct pnfs_layout_hdr *lo,
+				      const struct pnfs_layout_range *range,
+				      struct list_head *head,
+				      unsigned int maxnum)
+{
+	unsigned int ret;
+
+	ret = do_layout_fetch_ds_ioerr(lo, range, head, maxnum);
+	/* If we're over the max, discard all remaining entries */
+	if (ret == maxnum) {
+		LIST_HEAD(discard);
+		do_layout_fetch_ds_ioerr(lo, range, &discard, -1);
+		ff_layout_free_ds_ioerr(&discard);
+	}
+	return ret;
+}
+
+static bool ff_read_layout_has_available_ds(struct pnfs_layout_segment *lseg)
+{
+	struct nfs4_ff_layout_mirror *mirror;
+	struct nfs4_deviceid_node *devid;
+	u32 idx;
+
+	for (idx = 0; idx < FF_LAYOUT_MIRROR_COUNT(lseg); idx++) {
+		mirror = FF_LAYOUT_COMP(lseg, idx);
+		if (mirror) {
+			if (!mirror->mirror_ds)
+				return true;
+			if (IS_ERR(mirror->mirror_ds))
+				continue;
+			devid = &mirror->mirror_ds->id_node;
+			if (!nfs4_test_deviceid_unavailable(devid))
+				return true;
+		}
+	}
+
+	return false;
+}
+
+static bool ff_rw_layout_has_available_ds(struct pnfs_layout_segment *lseg)
+{
+	struct nfs4_ff_layout_mirror *mirror;
+	struct nfs4_deviceid_node *devid;
+	u32 idx;
+
+	for (idx = 0; idx < FF_LAYOUT_MIRROR_COUNT(lseg); idx++) {
+		mirror = FF_LAYOUT_COMP(lseg, idx);
+		if (!mirror || IS_ERR(mirror->mirror_ds))
+			return false;
+		if (!mirror->mirror_ds)
+			continue;
+		devid = &mirror->mirror_ds->id_node;
+		if (nfs4_test_deviceid_unavailable(devid))
+			return false;
+	}
+
+	return FF_LAYOUT_MIRROR_COUNT(lseg) != 0;
+}
+
+static bool ff_layout_has_available_ds(struct pnfs_layout_segment *lseg)
+{
+	if (lseg->pls_range.iomode == IOMODE_READ)
+		return  ff_read_layout_has_available_ds(lseg);
+	/* Note: RW layout needs all mirrors available */
+	return ff_rw_layout_has_available_ds(lseg);
+}
+
+bool ff_layout_avoid_mds_available_ds(struct pnfs_layout_segment *lseg)
+{
+	return ff_layout_no_fallback_to_mds(lseg) ||
+	       ff_layout_has_available_ds(lseg);
+}
+
+bool ff_layout_avoid_read_on_rw(struct pnfs_layout_segment *lseg)
+{
+	return lseg->pls_range.iomode == IOMODE_RW &&
+	       ff_layout_no_read_on_rw(lseg);
+}
+
+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.");