Adding upstream version 5.10.209.upstream/5.10.209upstream

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

1 files changed, 1455 insertions, 0 deletions

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
new file mode 100644
index 000000000..1eb6c7a14
--- /dev/null
+++ b/fs/nfs/delegation.c
@@ -0,0 +1,1455 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * linux/fs/nfs/delegation.c
+ *
+ * Copyright (C) 2004 Trond Myklebust
+ *
+ * NFS file delegation management
+ *
+ */
+#include <linux/completion.h>
+#include <linux/kthread.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/iversion.h>
+
+#include <linux/nfs4.h>
+#include <linux/nfs_fs.h>
+#include <linux/nfs_xdr.h>
+
+#include "nfs4_fs.h"
+#include "nfs4session.h"
+#include "delegation.h"
+#include "internal.h"
+#include "nfs4trace.h"
+
+#define NFS_DEFAULT_DELEGATION_WATERMARK (5000U)
+
+static atomic_long_t nfs_active_delegations;
+static unsigned nfs_delegation_watermark = NFS_DEFAULT_DELEGATION_WATERMARK;
+
+static void __nfs_free_delegation(struct nfs_delegation *delegation)
+{
+	put_cred(delegation->cred);
+	delegation->cred = NULL;
+	kfree_rcu(delegation, rcu);
+}
+
+static void nfs_mark_delegation_revoked(struct nfs_delegation *delegation)
+{
+	if (!test_and_set_bit(NFS_DELEGATION_REVOKED, &delegation->flags)) {
+		delegation->stateid.type = NFS4_INVALID_STATEID_TYPE;
+		atomic_long_dec(&nfs_active_delegations);
+		if (!test_bit(NFS_DELEGATION_RETURNING, &delegation->flags))
+			nfs_clear_verifier_delegated(delegation->inode);
+	}
+}
+
+static struct nfs_delegation *nfs_get_delegation(struct nfs_delegation *delegation)
+{
+	refcount_inc(&delegation->refcount);
+	return delegation;
+}
+
+static void nfs_put_delegation(struct nfs_delegation *delegation)
+{
+	if (refcount_dec_and_test(&delegation->refcount))
+		__nfs_free_delegation(delegation);
+}
+
+static void nfs_free_delegation(struct nfs_delegation *delegation)
+{
+	nfs_mark_delegation_revoked(delegation);
+	nfs_put_delegation(delegation);
+}
+
+/**
+ * nfs_mark_delegation_referenced - set delegation's REFERENCED flag
+ * @delegation: delegation to process
+ *
+ */
+void nfs_mark_delegation_referenced(struct nfs_delegation *delegation)
+{
+	set_bit(NFS_DELEGATION_REFERENCED, &delegation->flags);
+}
+
+static void nfs_mark_return_delegation(struct nfs_server *server,
+				       struct nfs_delegation *delegation)
+{
+	set_bit(NFS_DELEGATION_RETURN, &delegation->flags);
+	set_bit(NFS4CLNT_DELEGRETURN, &server->nfs_client->cl_state);
+}
+
+static bool
+nfs4_is_valid_delegation(const struct nfs_delegation *delegation,
+		fmode_t flags)
+{
+	if (delegation != NULL && (delegation->type & flags) == flags &&
+	    !test_bit(NFS_DELEGATION_REVOKED, &delegation->flags) &&
+	    !test_bit(NFS_DELEGATION_RETURNING, &delegation->flags))
+		return true;
+	return false;
+}
+
+struct nfs_delegation *nfs4_get_valid_delegation(const struct inode *inode)
+{
+	struct nfs_delegation *delegation;
+
+	delegation = rcu_dereference(NFS_I(inode)->delegation);
+	if (nfs4_is_valid_delegation(delegation, 0))
+		return delegation;
+	return NULL;
+}
+
+static int
+nfs4_do_check_delegation(struct inode *inode, fmode_t flags, bool mark)
+{
+	struct nfs_delegation *delegation;
+	int ret = 0;
+
+	flags &= FMODE_READ|FMODE_WRITE;
+	rcu_read_lock();
+	delegation = rcu_dereference(NFS_I(inode)->delegation);
+	if (nfs4_is_valid_delegation(delegation, flags)) {
+		if (mark)
+			nfs_mark_delegation_referenced(delegation);
+		ret = 1;
+	}
+	rcu_read_unlock();
+	return ret;
+}
+/**
+ * nfs_have_delegation - check if inode has a delegation, mark it
+ * NFS_DELEGATION_REFERENCED if there is one.
+ * @inode: inode to check
+ * @flags: delegation types to check for
+ *
+ * Returns one if inode has the indicated delegation, otherwise zero.
+ */
+int nfs4_have_delegation(struct inode *inode, fmode_t flags)
+{
+	return nfs4_do_check_delegation(inode, flags, true);
+}
+
+/*
+ * nfs4_check_delegation - check if inode has a delegation, do not mark
+ * NFS_DELEGATION_REFERENCED if it has one.
+ */
+int nfs4_check_delegation(struct inode *inode, fmode_t flags)
+{
+	return nfs4_do_check_delegation(inode, flags, false);
+}
+
+static int nfs_delegation_claim_locks(struct nfs4_state *state, const nfs4_stateid *stateid)
+{
+	struct inode *inode = state->inode;
+	struct file_lock *fl;
+	struct file_lock_context *flctx = inode->i_flctx;
+	struct list_head *list;
+	int status = 0;
+
+	if (flctx == NULL)
+		goto out;
+
+	list = &flctx->flc_posix;
+	spin_lock(&flctx->flc_lock);
+restart:
+	list_for_each_entry(fl, list, fl_list) {
+		if (nfs_file_open_context(fl->fl_file)->state != state)
+			continue;
+		spin_unlock(&flctx->flc_lock);
+		status = nfs4_lock_delegation_recall(fl, state, stateid);
+		if (status < 0)
+			goto out;
+		spin_lock(&flctx->flc_lock);
+	}
+	if (list == &flctx->flc_posix) {
+		list = &flctx->flc_flock;
+		goto restart;
+	}
+	spin_unlock(&flctx->flc_lock);
+out:
+	return status;
+}
+
+static int nfs_delegation_claim_opens(struct inode *inode,
+		const nfs4_stateid *stateid, fmode_t type)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+	struct nfs_open_context *ctx;
+	struct nfs4_state_owner *sp;
+	struct nfs4_state *state;
+	unsigned int seq;
+	int err;
+
+again:
+	rcu_read_lock();
+	list_for_each_entry_rcu(ctx, &nfsi->open_files, list) {
+		state = ctx->state;
+		if (state == NULL)
+			continue;
+		if (!test_bit(NFS_DELEGATED_STATE, &state->flags))
+			continue;
+		if (!nfs4_valid_open_stateid(state))
+			continue;
+		if (!nfs4_stateid_match(&state->stateid, stateid))
+			continue;
+		if (!get_nfs_open_context(ctx))
+			continue;
+		rcu_read_unlock();
+		sp = state->owner;
+		/* Block nfs4_proc_unlck */
+		mutex_lock(&sp->so_delegreturn_mutex);
+		seq = raw_seqcount_begin(&sp->so_reclaim_seqcount);
+		err = nfs4_open_delegation_recall(ctx, state, stateid);
+		if (!err)
+			err = nfs_delegation_claim_locks(state, stateid);
+		if (!err && read_seqcount_retry(&sp->so_reclaim_seqcount, seq))
+			err = -EAGAIN;
+		mutex_unlock(&sp->so_delegreturn_mutex);
+		put_nfs_open_context(ctx);
+		if (err != 0)
+			return err;
+		goto again;
+	}
+	rcu_read_unlock();
+	return 0;
+}
+
+/**
+ * nfs_inode_reclaim_delegation - process a delegation reclaim request
+ * @inode: inode to process
+ * @cred: credential to use for request
+ * @type: delegation type
+ * @stateid: delegation stateid
+ * @pagemod_limit: write delegation "space_limit"
+ *
+ */
+void nfs_inode_reclaim_delegation(struct inode *inode, const struct cred *cred,
+				  fmode_t type, const nfs4_stateid *stateid,
+				  unsigned long pagemod_limit)
+{
+	struct nfs_delegation *delegation;
+	const struct cred *oldcred = NULL;
+
+	rcu_read_lock();
+	delegation = rcu_dereference(NFS_I(inode)->delegation);
+	if (delegation != NULL) {
+		spin_lock(&delegation->lock);
+		nfs4_stateid_copy(&delegation->stateid, stateid);
+		delegation->type = type;
+		delegation->pagemod_limit = pagemod_limit;
+		oldcred = delegation->cred;
+		delegation->cred = get_cred(cred);
+		clear_bit(NFS_DELEGATION_NEED_RECLAIM, &delegation->flags);
+		if (test_and_clear_bit(NFS_DELEGATION_REVOKED,
+				       &delegation->flags))
+			atomic_long_inc(&nfs_active_delegations);
+		spin_unlock(&delegation->lock);
+		rcu_read_unlock();
+		put_cred(oldcred);
+		trace_nfs4_reclaim_delegation(inode, type);
+	} else {
+		rcu_read_unlock();
+		nfs_inode_set_delegation(inode, cred, type, stateid,
+					 pagemod_limit);
+	}
+}
+
+static int nfs_do_return_delegation(struct inode *inode, struct nfs_delegation *delegation, int issync)
+{
+	const struct cred *cred;
+	int res = 0;
+
+	if (!test_bit(NFS_DELEGATION_REVOKED, &delegation->flags)) {
+		spin_lock(&delegation->lock);
+		cred = get_cred(delegation->cred);
+		spin_unlock(&delegation->lock);
+		res = nfs4_proc_delegreturn(inode, cred,
+				&delegation->stateid,
+				issync);
+		put_cred(cred);
+	}
+	return res;
+}
+
+static struct inode *nfs_delegation_grab_inode(struct nfs_delegation *delegation)
+{
+	struct inode *inode = NULL;
+
+	spin_lock(&delegation->lock);
+	if (delegation->inode != NULL)
+		inode = igrab(delegation->inode);
+	if (!inode)
+		set_bit(NFS_DELEGATION_INODE_FREEING, &delegation->flags);
+	spin_unlock(&delegation->lock);
+	return inode;
+}
+
+static struct nfs_delegation *
+nfs_start_delegation_return_locked(struct nfs_inode *nfsi)
+{
+	struct nfs_delegation *ret = NULL;
+	struct nfs_delegation *delegation = rcu_dereference(nfsi->delegation);
+
+	if (delegation == NULL)
+		goto out;
+	spin_lock(&delegation->lock);
+	if (!test_and_set_bit(NFS_DELEGATION_RETURNING, &delegation->flags)) {
+		clear_bit(NFS_DELEGATION_RETURN_DELAYED, &delegation->flags);
+		/* Refcount matched in nfs_end_delegation_return() */
+		ret = nfs_get_delegation(delegation);
+	}
+	spin_unlock(&delegation->lock);
+	if (ret)
+		nfs_clear_verifier_delegated(&nfsi->vfs_inode);
+out:
+	return ret;
+}
+
+static struct nfs_delegation *
+nfs_start_delegation_return(struct nfs_inode *nfsi)
+{
+	struct nfs_delegation *delegation;
+
+	rcu_read_lock();
+	delegation = nfs_start_delegation_return_locked(nfsi);
+	rcu_read_unlock();
+	return delegation;
+}
+
+static void nfs_abort_delegation_return(struct nfs_delegation *delegation,
+					struct nfs_client *clp, int err)
+{
+
+	spin_lock(&delegation->lock);
+	clear_bit(NFS_DELEGATION_RETURNING, &delegation->flags);
+	if (err == -EAGAIN) {
+		set_bit(NFS_DELEGATION_RETURN_DELAYED, &delegation->flags);
+		set_bit(NFS4CLNT_DELEGRETURN_DELAYED, &clp->cl_state);
+	}
+	spin_unlock(&delegation->lock);
+}
+
+static struct nfs_delegation *
+nfs_detach_delegation_locked(struct nfs_inode *nfsi,
+		struct nfs_delegation *delegation,
+		struct nfs_client *clp)
+{
+	struct nfs_delegation *deleg_cur =
+		rcu_dereference_protected(nfsi->delegation,
+				lockdep_is_held(&clp->cl_lock));
+
+	if (deleg_cur == NULL || delegation != deleg_cur)
+		return NULL;
+
+	spin_lock(&delegation->lock);
+	if (!delegation->inode) {
+		spin_unlock(&delegation->lock);
+		return NULL;
+	}
+	list_del_rcu(&delegation->super_list);
+	delegation->inode = NULL;
+	rcu_assign_pointer(nfsi->delegation, NULL);
+	spin_unlock(&delegation->lock);
+	return delegation;
+}
+
+static struct nfs_delegation *nfs_detach_delegation(struct nfs_inode *nfsi,
+		struct nfs_delegation *delegation,
+		struct nfs_server *server)
+{
+	struct nfs_client *clp = server->nfs_client;
+
+	spin_lock(&clp->cl_lock);
+	delegation = nfs_detach_delegation_locked(nfsi, delegation, clp);
+	spin_unlock(&clp->cl_lock);
+	return delegation;
+}
+
+static struct nfs_delegation *
+nfs_inode_detach_delegation(struct inode *inode)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+	struct nfs_server *server = NFS_SERVER(inode);
+	struct nfs_delegation *delegation;
+
+	rcu_read_lock();
+	delegation = rcu_dereference(nfsi->delegation);
+	if (delegation != NULL)
+		delegation = nfs_detach_delegation(nfsi, delegation, server);
+	rcu_read_unlock();
+	return delegation;
+}
+
+static void
+nfs_update_delegation_cred(struct nfs_delegation *delegation,
+		const struct cred *cred)
+{
+	const struct cred *old;
+
+	if (cred_fscmp(delegation->cred, cred) != 0) {
+		old = xchg(&delegation->cred, get_cred(cred));
+		put_cred(old);
+	}
+}
+
+static void
+nfs_update_inplace_delegation(struct nfs_delegation *delegation,
+		const struct nfs_delegation *update)
+{
+	if (nfs4_stateid_is_newer(&update->stateid, &delegation->stateid)) {
+		delegation->stateid.seqid = update->stateid.seqid;
+		smp_wmb();
+		delegation->type = update->type;
+		delegation->pagemod_limit = update->pagemod_limit;
+		if (test_bit(NFS_DELEGATION_REVOKED, &delegation->flags)) {
+			delegation->change_attr = update->change_attr;
+			nfs_update_delegation_cred(delegation, update->cred);
+			/* smp_mb__before_atomic() is implicit due to xchg() */
+			clear_bit(NFS_DELEGATION_REVOKED, &delegation->flags);
+			atomic_long_inc(&nfs_active_delegations);
+		}
+	}
+}
+
+/**
+ * nfs_inode_set_delegation - set up a delegation on an inode
+ * @inode: inode to which delegation applies
+ * @cred: cred to use for subsequent delegation processing
+ * @type: delegation type
+ * @stateid: delegation stateid
+ * @pagemod_limit: write delegation "space_limit"
+ *
+ * Returns zero on success, or a negative errno value.
+ */
+int nfs_inode_set_delegation(struct inode *inode, const struct cred *cred,
+				  fmode_t type,
+				  const nfs4_stateid *stateid,
+				  unsigned long pagemod_limit)
+{
+	struct nfs_server *server = NFS_SERVER(inode);
+	struct nfs_client *clp = server->nfs_client;
+	struct nfs_inode *nfsi = NFS_I(inode);
+	struct nfs_delegation *delegation, *old_delegation;
+	struct nfs_delegation *freeme = NULL;
+	int status = 0;
+
+	delegation = kmalloc(sizeof(*delegation), GFP_NOFS);
+	if (delegation == NULL)
+		return -ENOMEM;
+	nfs4_stateid_copy(&delegation->stateid, stateid);
+	refcount_set(&delegation->refcount, 1);
+	delegation->type = type;
+	delegation->pagemod_limit = pagemod_limit;
+	delegation->change_attr = inode_peek_iversion_raw(inode);
+	delegation->cred = get_cred(cred);
+	delegation->inode = inode;
+	delegation->flags = 1<<NFS_DELEGATION_REFERENCED;
+	spin_lock_init(&delegation->lock);
+
+	spin_lock(&clp->cl_lock);
+	old_delegation = rcu_dereference_protected(nfsi->delegation,
+					lockdep_is_held(&clp->cl_lock));
+	if (old_delegation == NULL)
+		goto add_new;
+	/* Is this an update of the existing delegation? */
+	if (nfs4_stateid_match_other(&old_delegation->stateid,
+				&delegation->stateid)) {
+		spin_lock(&old_delegation->lock);
+		nfs_update_inplace_delegation(old_delegation,
+				delegation);
+		spin_unlock(&old_delegation->lock);
+		goto out;
+	}
+	if (!test_bit(NFS_DELEGATION_REVOKED, &old_delegation->flags)) {
+		/*
+		 * Deal with broken servers that hand out two
+		 * delegations for the same file.
+		 * Allow for upgrades to a WRITE delegation, but
+		 * nothing else.
+		 */
+		dfprintk(FILE, "%s: server %s handed out "
+				"a duplicate delegation!\n",
+				__func__, clp->cl_hostname);
+		if (delegation->type == old_delegation->type ||
+		    !(delegation->type & FMODE_WRITE)) {
+			freeme = delegation;
+			delegation = NULL;
+			goto out;
+		}
+		if (test_and_set_bit(NFS_DELEGATION_RETURNING,
+					&old_delegation->flags))
+			goto out;
+	}
+	freeme = nfs_detach_delegation_locked(nfsi, old_delegation, clp);
+	if (freeme == NULL)
+		goto out;
+add_new:
+	list_add_tail_rcu(&delegation->super_list, &server->delegations);
+	rcu_assign_pointer(nfsi->delegation, delegation);
+	delegation = NULL;
+
+	atomic_long_inc(&nfs_active_delegations);
+
+	trace_nfs4_set_delegation(inode, type);
+
+	spin_lock(&inode->i_lock);
+	if (NFS_I(inode)->cache_validity & (NFS_INO_INVALID_ATTR|NFS_INO_INVALID_ATIME))
+		NFS_I(inode)->cache_validity |= NFS_INO_REVAL_FORCED;
+	spin_unlock(&inode->i_lock);
+out:
+	spin_unlock(&clp->cl_lock);
+	if (delegation != NULL)
+		__nfs_free_delegation(delegation);
+	if (freeme != NULL) {
+		nfs_do_return_delegation(inode, freeme, 0);
+		nfs_free_delegation(freeme);
+	}
+	return status;
+}
+
+/*
+ * Basic procedure for returning a delegation to the server
+ */
+static int nfs_end_delegation_return(struct inode *inode, struct nfs_delegation *delegation, int issync)
+{
+	struct nfs_client *clp = NFS_SERVER(inode)->nfs_client;
+	int err = 0;
+
+	if (delegation == NULL)
+		return 0;
+	do {
+		if (test_bit(NFS_DELEGATION_REVOKED, &delegation->flags))
+			break;
+		err = nfs_delegation_claim_opens(inode, &delegation->stateid,
+				delegation->type);
+		if (!issync || err != -EAGAIN)
+			break;
+		/*
+		 * Guard against state recovery
+		 */
+		err = nfs4_wait_clnt_recover(clp);
+	} while (err == 0);
+
+	if (err) {
+		nfs_abort_delegation_return(delegation, clp, err);
+		goto out;
+	}
+
+	err = nfs_do_return_delegation(inode, delegation, issync);
+out:
+	/* Refcount matched in nfs_start_delegation_return_locked() */
+	nfs_put_delegation(delegation);
+	return err;
+}
+
+static bool nfs_delegation_need_return(struct nfs_delegation *delegation)
+{
+	bool ret = false;
+
+	if (test_and_clear_bit(NFS_DELEGATION_RETURN, &delegation->flags))
+		ret = true;
+	else if (test_bit(NFS_DELEGATION_RETURN_IF_CLOSED, &delegation->flags)) {
+		struct inode *inode;
+
+		spin_lock(&delegation->lock);
+		inode = delegation->inode;
+		if (inode && list_empty(&NFS_I(inode)->open_files))
+			ret = true;
+		spin_unlock(&delegation->lock);
+	}
+	if (ret)
+		clear_bit(NFS_DELEGATION_RETURN_IF_CLOSED, &delegation->flags);
+	if (test_bit(NFS_DELEGATION_RETURNING, &delegation->flags) ||
+	    test_bit(NFS_DELEGATION_RETURN_DELAYED, &delegation->flags) ||
+	    test_bit(NFS_DELEGATION_REVOKED, &delegation->flags))
+		ret = false;
+
+	return ret;
+}
+
+static int nfs_server_return_marked_delegations(struct nfs_server *server,
+		void __always_unused *data)
+{
+	struct nfs_delegation *delegation;
+	struct nfs_delegation *prev;
+	struct inode *inode;
+	struct inode *place_holder = NULL;
+	struct nfs_delegation *place_holder_deleg = NULL;
+	int err = 0;
+
+restart:
+	/*
+	 * To avoid quadratic looping we hold a reference
+	 * to an inode place_holder.  Each time we restart, we
+	 * list delegation in the server from the delegations
+	 * of that inode.
+	 * prev is an RCU-protected pointer to a delegation which
+	 * wasn't marked for return and might be a good choice for
+	 * the next place_holder.
+	 */
+	prev = NULL;
+	delegation = NULL;
+	rcu_read_lock();
+	if (place_holder)
+		delegation = rcu_dereference(NFS_I(place_holder)->delegation);
+	if (!delegation || delegation != place_holder_deleg)
+		delegation = list_entry_rcu(server->delegations.next,
+					    struct nfs_delegation, super_list);
+	list_for_each_entry_from_rcu(delegation, &server->delegations, super_list) {
+		struct inode *to_put = NULL;
+
+		if (test_bit(NFS_DELEGATION_INODE_FREEING, &delegation->flags))
+			continue;
+		if (!nfs_delegation_need_return(delegation)) {
+			if (nfs4_is_valid_delegation(delegation, 0))
+				prev = delegation;
+			continue;
+		}
+
+		if (prev) {
+			struct inode *tmp = nfs_delegation_grab_inode(prev);
+			if (tmp) {
+				to_put = place_holder;
+				place_holder = tmp;
+				place_holder_deleg = prev;
+			}
+		}
+
+		inode = nfs_delegation_grab_inode(delegation);
+		if (inode == NULL) {
+			rcu_read_unlock();
+			iput(to_put);
+			goto restart;
+		}
+		delegation = nfs_start_delegation_return_locked(NFS_I(inode));
+		rcu_read_unlock();
+
+		iput(to_put);
+
+		err = nfs_end_delegation_return(inode, delegation, 0);
+		iput(inode);
+		cond_resched();
+		if (!err)
+			goto restart;
+		set_bit(NFS4CLNT_DELEGRETURN, &server->nfs_client->cl_state);
+		goto out;
+	}
+	rcu_read_unlock();
+out:
+	iput(place_holder);
+	return err;
+}
+
+static bool nfs_server_clear_delayed_delegations(struct nfs_server *server)
+{
+	struct nfs_delegation *d;
+	bool ret = false;
+
+	list_for_each_entry_rcu (d, &server->delegations, super_list) {
+		if (!test_bit(NFS_DELEGATION_RETURN_DELAYED, &d->flags))
+			continue;
+		nfs_mark_return_delegation(server, d);
+		clear_bit(NFS_DELEGATION_RETURN_DELAYED, &d->flags);
+		ret = true;
+	}
+	return ret;
+}
+
+static bool nfs_client_clear_delayed_delegations(struct nfs_client *clp)
+{
+	struct nfs_server *server;
+	bool ret = false;
+
+	if (!test_and_clear_bit(NFS4CLNT_DELEGRETURN_DELAYED, &clp->cl_state))
+		goto out;
+	rcu_read_lock();
+	list_for_each_entry_rcu (server, &clp->cl_superblocks, client_link) {
+		if (nfs_server_clear_delayed_delegations(server))
+			ret = true;
+	}
+	rcu_read_unlock();
+out:
+	return ret;
+}
+
+/**
+ * nfs_client_return_marked_delegations - return previously marked delegations
+ * @clp: nfs_client to process
+ *
+ * Note that this function is designed to be called by the state
+ * manager thread. For this reason, it cannot flush the dirty data,
+ * since that could deadlock in case of a state recovery error.
+ *
+ * Returns zero on success, or a negative errno value.
+ */
+int nfs_client_return_marked_delegations(struct nfs_client *clp)
+{
+	int err = nfs_client_for_each_server(
+		clp, nfs_server_return_marked_delegations, NULL);
+	if (err)
+		return err;
+	/* If a return was delayed, sleep to prevent hard looping */
+	if (nfs_client_clear_delayed_delegations(clp))
+		ssleep(1);
+	return 0;
+}
+
+/**
+ * nfs_inode_evict_delegation - return delegation, don't reclaim opens
+ * @inode: inode to process
+ *
+ * Does not protect against delegation reclaims, therefore really only safe
+ * to be called from nfs4_clear_inode(). Guaranteed to always free
+ * the delegation structure.
+ */
+void nfs_inode_evict_delegation(struct inode *inode)
+{
+	struct nfs_delegation *delegation;
+
+	delegation = nfs_inode_detach_delegation(inode);
+	if (delegation != NULL) {
+		set_bit(NFS_DELEGATION_RETURNING, &delegation->flags);
+		set_bit(NFS_DELEGATION_INODE_FREEING, &delegation->flags);
+		nfs_do_return_delegation(inode, delegation, 1);
+		nfs_free_delegation(delegation);
+	}
+}
+
+/**
+ * nfs_inode_return_delegation - synchronously return a delegation
+ * @inode: inode to process
+ *
+ * This routine will always flush any dirty data to disk on the
+ * assumption that if we need to return the delegation, then
+ * we should stop caching.
+ *
+ * Returns zero on success, or a negative errno value.
+ */
+int nfs4_inode_return_delegation(struct inode *inode)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+	struct nfs_delegation *delegation;
+	int err = 0;
+
+	nfs_wb_all(inode);
+	delegation = nfs_start_delegation_return(nfsi);
+	if (delegation != NULL)
+		err = nfs_end_delegation_return(inode, delegation, 1);
+	return err;
+}
+
+/**
+ * nfs_inode_return_delegation_on_close - asynchronously return a delegation
+ * @inode: inode to process
+ *
+ * This routine is called on file close in order to determine if the
+ * inode delegation needs to be returned immediately.
+ */
+void nfs4_inode_return_delegation_on_close(struct inode *inode)
+{
+	struct nfs_delegation *delegation;
+	struct nfs_delegation *ret = NULL;
+
+	if (!inode)
+		return;
+	rcu_read_lock();
+	delegation = nfs4_get_valid_delegation(inode);
+	if (!delegation)
+		goto out;
+	if (test_bit(NFS_DELEGATION_RETURN_IF_CLOSED, &delegation->flags) ||
+	    atomic_long_read(&nfs_active_delegations) >= nfs_delegation_watermark) {
+		spin_lock(&delegation->lock);
+		if (delegation->inode &&
+		    list_empty(&NFS_I(inode)->open_files) &&
+		    !test_and_set_bit(NFS_DELEGATION_RETURNING, &delegation->flags)) {
+			clear_bit(NFS_DELEGATION_RETURN_IF_CLOSED, &delegation->flags);
+			/* Refcount matched in nfs_end_delegation_return() */
+			ret = nfs_get_delegation(delegation);
+		}
+		spin_unlock(&delegation->lock);
+		if (ret)
+			nfs_clear_verifier_delegated(inode);
+	}
+out:
+	rcu_read_unlock();
+	nfs_end_delegation_return(inode, ret, 0);
+}
+
+/**
+ * nfs4_inode_make_writeable
+ * @inode: pointer to inode
+ *
+ * Make the inode writeable by returning the delegation if necessary
+ *
+ * Returns zero on success, or a negative errno value.
+ */
+int nfs4_inode_make_writeable(struct inode *inode)
+{
+	struct nfs_delegation *delegation;
+
+	rcu_read_lock();
+	delegation = nfs4_get_valid_delegation(inode);
+	if (delegation == NULL ||
+	    (nfs4_has_session(NFS_SERVER(inode)->nfs_client) &&
+	     (delegation->type & FMODE_WRITE))) {
+		rcu_read_unlock();
+		return 0;
+	}
+	rcu_read_unlock();
+	return nfs4_inode_return_delegation(inode);
+}
+
+static void nfs_mark_return_if_closed_delegation(struct nfs_server *server,
+		struct nfs_delegation *delegation)
+{
+	set_bit(NFS_DELEGATION_RETURN_IF_CLOSED, &delegation->flags);
+	set_bit(NFS4CLNT_DELEGRETURN, &server->nfs_client->cl_state);
+}
+
+static bool nfs_server_mark_return_all_delegations(struct nfs_server *server)
+{
+	struct nfs_delegation *delegation;
+	bool ret = false;
+
+	list_for_each_entry_rcu(delegation, &server->delegations, super_list) {
+		nfs_mark_return_delegation(server, delegation);
+		ret = true;
+	}
+	return ret;
+}
+
+static void nfs_client_mark_return_all_delegations(struct nfs_client *clp)
+{
+	struct nfs_server *server;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
+		nfs_server_mark_return_all_delegations(server);
+	rcu_read_unlock();
+}
+
+static void nfs_delegation_run_state_manager(struct nfs_client *clp)
+{
+	if (test_bit(NFS4CLNT_DELEGRETURN, &clp->cl_state))
+		nfs4_schedule_state_manager(clp);
+}
+
+/**
+ * nfs_expire_all_delegations
+ * @clp: client to process
+ *
+ */
+void nfs_expire_all_delegations(struct nfs_client *clp)
+{
+	nfs_client_mark_return_all_delegations(clp);
+	nfs_delegation_run_state_manager(clp);
+}
+
+/**
+ * nfs_super_return_all_delegations - return delegations for one superblock
+ * @server: pointer to nfs_server to process
+ *
+ */
+void nfs_server_return_all_delegations(struct nfs_server *server)
+{
+	struct nfs_client *clp = server->nfs_client;
+	bool need_wait;
+
+	if (clp == NULL)
+		return;
+
+	rcu_read_lock();
+	need_wait = nfs_server_mark_return_all_delegations(server);
+	rcu_read_unlock();
+
+	if (need_wait) {
+		nfs4_schedule_state_manager(clp);
+		nfs4_wait_clnt_recover(clp);
+	}
+}
+
+static void nfs_mark_return_unused_delegation_types(struct nfs_server *server,
+						 fmode_t flags)
+{
+	struct nfs_delegation *delegation;
+
+	list_for_each_entry_rcu(delegation, &server->delegations, super_list) {
+		if ((delegation->type == (FMODE_READ|FMODE_WRITE)) && !(flags & FMODE_WRITE))
+			continue;
+		if (delegation->type & flags)
+			nfs_mark_return_if_closed_delegation(server, delegation);
+	}
+}
+
+static void nfs_client_mark_return_unused_delegation_types(struct nfs_client *clp,
+							fmode_t flags)
+{
+	struct nfs_server *server;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
+		nfs_mark_return_unused_delegation_types(server, flags);
+	rcu_read_unlock();
+}
+
+static void nfs_revoke_delegation(struct inode *inode,
+		const nfs4_stateid *stateid)
+{
+	struct nfs_delegation *delegation;
+	nfs4_stateid tmp;
+	bool ret = false;
+
+	rcu_read_lock();
+	delegation = rcu_dereference(NFS_I(inode)->delegation);
+	if (delegation == NULL)
+		goto out;
+	if (stateid == NULL) {
+		nfs4_stateid_copy(&tmp, &delegation->stateid);
+		stateid = &tmp;
+	} else {
+		if (!nfs4_stateid_match_other(stateid, &delegation->stateid))
+			goto out;
+		spin_lock(&delegation->lock);
+		if (stateid->seqid) {
+			if (nfs4_stateid_is_newer(&delegation->stateid, stateid)) {
+				spin_unlock(&delegation->lock);
+				goto out;
+			}
+			delegation->stateid.seqid = stateid->seqid;
+		}
+		spin_unlock(&delegation->lock);
+	}
+	nfs_mark_delegation_revoked(delegation);
+	ret = true;
+out:
+	rcu_read_unlock();
+	if (ret)
+		nfs_inode_find_state_and_recover(inode, stateid);
+}
+
+void nfs_remove_bad_delegation(struct inode *inode,
+		const nfs4_stateid *stateid)
+{
+	nfs_revoke_delegation(inode, stateid);
+}
+EXPORT_SYMBOL_GPL(nfs_remove_bad_delegation);
+
+void nfs_delegation_mark_returned(struct inode *inode,
+		const nfs4_stateid *stateid)
+{
+	struct nfs_delegation *delegation;
+
+	if (!inode)
+		return;
+
+	rcu_read_lock();
+	delegation = rcu_dereference(NFS_I(inode)->delegation);
+	if (!delegation)
+		goto out_rcu_unlock;
+
+	spin_lock(&delegation->lock);
+	if (!nfs4_stateid_match_other(stateid, &delegation->stateid))
+		goto out_spin_unlock;
+	if (stateid->seqid) {
+		/* If delegation->stateid is newer, dont mark as returned */
+		if (nfs4_stateid_is_newer(&delegation->stateid, stateid))
+			goto out_clear_returning;
+		if (delegation->stateid.seqid != stateid->seqid)
+			delegation->stateid.seqid = stateid->seqid;
+	}
+
+	nfs_mark_delegation_revoked(delegation);
+
+out_clear_returning:
+	clear_bit(NFS_DELEGATION_RETURNING, &delegation->flags);
+out_spin_unlock:
+	spin_unlock(&delegation->lock);
+out_rcu_unlock:
+	rcu_read_unlock();
+
+	nfs_inode_find_state_and_recover(inode, stateid);
+}
+
+/**
+ * nfs_expire_unused_delegation_types
+ * @clp: client to process
+ * @flags: delegation types to expire
+ *
+ */
+void nfs_expire_unused_delegation_types(struct nfs_client *clp, fmode_t flags)
+{
+	nfs_client_mark_return_unused_delegation_types(clp, flags);
+	nfs_delegation_run_state_manager(clp);
+}
+
+static void nfs_mark_return_unreferenced_delegations(struct nfs_server *server)
+{
+	struct nfs_delegation *delegation;
+
+	list_for_each_entry_rcu(delegation, &server->delegations, super_list) {
+		if (test_and_clear_bit(NFS_DELEGATION_REFERENCED, &delegation->flags))
+			continue;
+		nfs_mark_return_if_closed_delegation(server, delegation);
+	}
+}
+
+/**
+ * nfs_expire_unreferenced_delegations - Eliminate unused delegations
+ * @clp: nfs_client to process
+ *
+ */
+void nfs_expire_unreferenced_delegations(struct nfs_client *clp)
+{
+	struct nfs_server *server;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
+		nfs_mark_return_unreferenced_delegations(server);
+	rcu_read_unlock();
+
+	nfs_delegation_run_state_manager(clp);
+}
+
+/**
+ * nfs_async_inode_return_delegation - asynchronously return a delegation
+ * @inode: inode to process
+ * @stateid: state ID information
+ *
+ * Returns zero on success, or a negative errno value.
+ */
+int nfs_async_inode_return_delegation(struct inode *inode,
+				      const nfs4_stateid *stateid)
+{
+	struct nfs_server *server = NFS_SERVER(inode);
+	struct nfs_client *clp = server->nfs_client;
+	struct nfs_delegation *delegation;
+
+	rcu_read_lock();
+	delegation = nfs4_get_valid_delegation(inode);
+	if (delegation == NULL)
+		goto out_enoent;
+	if (stateid != NULL &&
+	    !clp->cl_mvops->match_stateid(&delegation->stateid, stateid))
+		goto out_enoent;
+	nfs_mark_return_delegation(server, delegation);
+	rcu_read_unlock();
+
+	nfs_delegation_run_state_manager(clp);
+	return 0;
+out_enoent:
+	rcu_read_unlock();
+	return -ENOENT;
+}
+
+static struct inode *
+nfs_delegation_find_inode_server(struct nfs_server *server,
+				 const struct nfs_fh *fhandle)
+{
+	struct nfs_delegation *delegation;
+	struct super_block *freeme = NULL;
+	struct inode *res = NULL;
+
+	list_for_each_entry_rcu(delegation, &server->delegations, super_list) {
+		spin_lock(&delegation->lock);
+		if (delegation->inode != NULL &&
+		    !test_bit(NFS_DELEGATION_REVOKED, &delegation->flags) &&
+		    nfs_compare_fh(fhandle, &NFS_I(delegation->inode)->fh) == 0) {
+			if (nfs_sb_active(server->super)) {
+				freeme = server->super;
+				res = igrab(delegation->inode);
+			}
+			spin_unlock(&delegation->lock);
+			if (res != NULL)
+				return res;
+			if (freeme) {
+				rcu_read_unlock();
+				nfs_sb_deactive(freeme);
+				rcu_read_lock();
+			}
+			return ERR_PTR(-EAGAIN);
+		}
+		spin_unlock(&delegation->lock);
+	}
+	return ERR_PTR(-ENOENT);
+}
+
+/**
+ * nfs_delegation_find_inode - retrieve the inode associated with a delegation
+ * @clp: client state handle
+ * @fhandle: filehandle from a delegation recall
+ *
+ * Returns pointer to inode matching "fhandle," or NULL if a matching inode
+ * cannot be found.
+ */
+struct inode *nfs_delegation_find_inode(struct nfs_client *clp,
+					const struct nfs_fh *fhandle)
+{
+	struct nfs_server *server;
+	struct inode *res;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
+		res = nfs_delegation_find_inode_server(server, fhandle);
+		if (res != ERR_PTR(-ENOENT)) {
+			rcu_read_unlock();
+			return res;
+		}
+	}
+	rcu_read_unlock();
+	return ERR_PTR(-ENOENT);
+}
+
+static void nfs_delegation_mark_reclaim_server(struct nfs_server *server)
+{
+	struct nfs_delegation *delegation;
+
+	list_for_each_entry_rcu(delegation, &server->delegations, super_list) {
+		/*
+		 * If the delegation may have been admin revoked, then we
+		 * cannot reclaim it.
+		 */
+		if (test_bit(NFS_DELEGATION_TEST_EXPIRED, &delegation->flags))
+			continue;
+		set_bit(NFS_DELEGATION_NEED_RECLAIM, &delegation->flags);
+	}
+}
+
+/**
+ * nfs_delegation_mark_reclaim - mark all delegations as needing to be reclaimed
+ * @clp: nfs_client to process
+ *
+ */
+void nfs_delegation_mark_reclaim(struct nfs_client *clp)
+{
+	struct nfs_server *server;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
+		nfs_delegation_mark_reclaim_server(server);
+	rcu_read_unlock();
+}
+
+static int nfs_server_reap_unclaimed_delegations(struct nfs_server *server,
+		void __always_unused *data)
+{
+	struct nfs_delegation *delegation;
+	struct inode *inode;
+restart:
+	rcu_read_lock();
+restart_locked:
+	list_for_each_entry_rcu(delegation, &server->delegations, super_list) {
+		if (test_bit(NFS_DELEGATION_INODE_FREEING,
+					&delegation->flags) ||
+		    test_bit(NFS_DELEGATION_RETURNING,
+					&delegation->flags) ||
+		    test_bit(NFS_DELEGATION_NEED_RECLAIM,
+					&delegation->flags) == 0)
+			continue;
+		inode = nfs_delegation_grab_inode(delegation);
+		if (inode == NULL)
+			goto restart_locked;
+		delegation = nfs_start_delegation_return_locked(NFS_I(inode));
+		rcu_read_unlock();
+		if (delegation != NULL) {
+			if (nfs_detach_delegation(NFS_I(inode), delegation,
+						server) != NULL)
+				nfs_free_delegation(delegation);
+			/* Match nfs_start_delegation_return_locked */
+			nfs_put_delegation(delegation);
+		}
+		iput(inode);
+		cond_resched();
+		goto restart;
+	}
+	rcu_read_unlock();
+	return 0;
+}
+
+/**
+ * nfs_delegation_reap_unclaimed - reap unclaimed delegations after reboot recovery is done
+ * @clp: nfs_client to process
+ *
+ */
+void nfs_delegation_reap_unclaimed(struct nfs_client *clp)
+{
+	nfs_client_for_each_server(clp, nfs_server_reap_unclaimed_delegations,
+			NULL);
+}
+
+static inline bool nfs4_server_rebooted(const struct nfs_client *clp)
+{
+	return (clp->cl_state & (BIT(NFS4CLNT_CHECK_LEASE) |
+				BIT(NFS4CLNT_LEASE_EXPIRED) |
+				BIT(NFS4CLNT_SESSION_RESET))) != 0;
+}
+
+static void nfs_mark_test_expired_delegation(struct nfs_server *server,
+	    struct nfs_delegation *delegation)
+{
+	if (delegation->stateid.type == NFS4_INVALID_STATEID_TYPE)
+		return;
+	clear_bit(NFS_DELEGATION_NEED_RECLAIM, &delegation->flags);
+	set_bit(NFS_DELEGATION_TEST_EXPIRED, &delegation->flags);
+	set_bit(NFS4CLNT_DELEGATION_EXPIRED, &server->nfs_client->cl_state);
+}
+
+static void nfs_inode_mark_test_expired_delegation(struct nfs_server *server,
+		struct inode *inode)
+{
+	struct nfs_delegation *delegation;
+
+	rcu_read_lock();
+	delegation = rcu_dereference(NFS_I(inode)->delegation);
+	if (delegation)
+		nfs_mark_test_expired_delegation(server, delegation);
+	rcu_read_unlock();
+
+}
+
+static void nfs_delegation_mark_test_expired_server(struct nfs_server *server)
+{
+	struct nfs_delegation *delegation;
+
+	list_for_each_entry_rcu(delegation, &server->delegations, super_list)
+		nfs_mark_test_expired_delegation(server, delegation);
+}
+
+/**
+ * nfs_mark_test_expired_all_delegations - mark all delegations for testing
+ * @clp: nfs_client to process
+ *
+ * Iterates through all the delegations associated with this server and
+ * marks them as needing to be checked for validity.
+ */
+void nfs_mark_test_expired_all_delegations(struct nfs_client *clp)
+{
+	struct nfs_server *server;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
+		nfs_delegation_mark_test_expired_server(server);
+	rcu_read_unlock();
+}
+
+/**
+ * nfs_test_expired_all_delegations - test all delegations for a client
+ * @clp: nfs_client to process
+ *
+ * Helper for handling "recallable state revoked" status from server.
+ */
+void nfs_test_expired_all_delegations(struct nfs_client *clp)
+{
+	nfs_mark_test_expired_all_delegations(clp);
+	nfs4_schedule_state_manager(clp);
+}
+
+static void
+nfs_delegation_test_free_expired(struct inode *inode,
+		nfs4_stateid *stateid,
+		const struct cred *cred)
+{
+	struct nfs_server *server = NFS_SERVER(inode);
+	const struct nfs4_minor_version_ops *ops = server->nfs_client->cl_mvops;
+	int status;
+
+	if (!cred)
+		return;
+	status = ops->test_and_free_expired(server, stateid, cred);
+	if (status == -NFS4ERR_EXPIRED || status == -NFS4ERR_BAD_STATEID)
+		nfs_remove_bad_delegation(inode, stateid);
+}
+
+static int nfs_server_reap_expired_delegations(struct nfs_server *server,
+		void __always_unused *data)
+{
+	struct nfs_delegation *delegation;
+	struct inode *inode;
+	const struct cred *cred;
+	nfs4_stateid stateid;
+restart:
+	rcu_read_lock();
+restart_locked:
+	list_for_each_entry_rcu(delegation, &server->delegations, super_list) {
+		if (test_bit(NFS_DELEGATION_INODE_FREEING,
+					&delegation->flags) ||
+		    test_bit(NFS_DELEGATION_RETURNING,
+					&delegation->flags) ||
+		    test_bit(NFS_DELEGATION_TEST_EXPIRED,
+					&delegation->flags) == 0)
+			continue;
+		inode = nfs_delegation_grab_inode(delegation);
+		if (inode == NULL)
+			goto restart_locked;
+		spin_lock(&delegation->lock);
+		cred = get_cred_rcu(delegation->cred);
+		nfs4_stateid_copy(&stateid, &delegation->stateid);
+		spin_unlock(&delegation->lock);
+		clear_bit(NFS_DELEGATION_TEST_EXPIRED, &delegation->flags);
+		rcu_read_unlock();
+		nfs_delegation_test_free_expired(inode, &stateid, cred);
+		put_cred(cred);
+		if (!nfs4_server_rebooted(server->nfs_client)) {
+			iput(inode);
+			cond_resched();
+			goto restart;
+		}
+		nfs_inode_mark_test_expired_delegation(server,inode);
+		iput(inode);
+		return -EAGAIN;
+	}
+	rcu_read_unlock();
+	return 0;
+}
+
+/**
+ * nfs_reap_expired_delegations - reap expired delegations
+ * @clp: nfs_client to process
+ *
+ * Iterates through all the delegations associated with this server and
+ * checks if they have may have been revoked. This function is usually
+ * expected to be called in cases where the server may have lost its
+ * lease.
+ */
+void nfs_reap_expired_delegations(struct nfs_client *clp)
+{
+	nfs_client_for_each_server(clp, nfs_server_reap_expired_delegations,
+			NULL);
+}
+
+void nfs_inode_find_delegation_state_and_recover(struct inode *inode,
+		const nfs4_stateid *stateid)
+{
+	struct nfs_client *clp = NFS_SERVER(inode)->nfs_client;
+	struct nfs_delegation *delegation;
+	bool found = false;
+
+	rcu_read_lock();
+	delegation = rcu_dereference(NFS_I(inode)->delegation);
+	if (delegation &&
+	    nfs4_stateid_match_or_older(&delegation->stateid, stateid) &&
+	    !test_bit(NFS_DELEGATION_REVOKED, &delegation->flags)) {
+		nfs_mark_test_expired_delegation(NFS_SERVER(inode), delegation);
+		found = true;
+	}
+	rcu_read_unlock();
+	if (found)
+		nfs4_schedule_state_manager(clp);
+}
+
+/**
+ * nfs_delegations_present - check for existence of delegations
+ * @clp: client state handle
+ *
+ * Returns one if there are any nfs_delegation structures attached
+ * to this nfs_client.
+ */
+int nfs_delegations_present(struct nfs_client *clp)
+{
+	struct nfs_server *server;
+	int ret = 0;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
+		if (!list_empty(&server->delegations)) {
+			ret = 1;
+			break;
+		}
+	rcu_read_unlock();
+	return ret;
+}
+
+/**
+ * nfs4_refresh_delegation_stateid - Update delegation stateid seqid
+ * @dst: stateid to refresh
+ * @inode: inode to check
+ *
+ * Returns "true" and updates "dst->seqid" * if inode had a delegation
+ * that matches our delegation stateid. Otherwise "false" is returned.
+ */
+bool nfs4_refresh_delegation_stateid(nfs4_stateid *dst, struct inode *inode)
+{
+	struct nfs_delegation *delegation;
+	bool ret = false;
+	if (!inode)
+		goto out;
+
+	rcu_read_lock();
+	delegation = rcu_dereference(NFS_I(inode)->delegation);
+	if (delegation != NULL &&
+	    nfs4_stateid_match_other(dst, &delegation->stateid) &&
+	    nfs4_stateid_is_newer(&delegation->stateid, dst) &&
+	    !test_bit(NFS_DELEGATION_REVOKED, &delegation->flags)) {
+		dst->seqid = delegation->stateid.seqid;
+		ret = true;
+	}
+	rcu_read_unlock();
+out:
+	return ret;
+}
+
+/**
+ * nfs4_copy_delegation_stateid - Copy inode's state ID information
+ * @inode: inode to check
+ * @flags: delegation type requirement
+ * @dst: stateid data structure to fill in
+ * @cred: optional argument to retrieve credential
+ *
+ * Returns "true" and fills in "dst->data" * if inode had a delegation,
+ * otherwise "false" is returned.
+ */
+bool nfs4_copy_delegation_stateid(struct inode *inode, fmode_t flags,
+		nfs4_stateid *dst, const struct cred **cred)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+	struct nfs_delegation *delegation;
+	bool ret = false;
+
+	flags &= FMODE_READ|FMODE_WRITE;
+	rcu_read_lock();
+	delegation = rcu_dereference(nfsi->delegation);
+	if (!delegation)
+		goto out;
+	spin_lock(&delegation->lock);
+	ret = nfs4_is_valid_delegation(delegation, flags);
+	if (ret) {
+		nfs4_stateid_copy(dst, &delegation->stateid);
+		nfs_mark_delegation_referenced(delegation);
+		if (cred)
+			*cred = get_cred(delegation->cred);
+	}
+	spin_unlock(&delegation->lock);
+out:
+	rcu_read_unlock();
+	return ret;
+}
+
+/**
+ * nfs4_delegation_flush_on_close - Check if we must flush file on close
+ * @inode: inode to check
+ *
+ * This function checks the number of outstanding writes to the file
+ * against the delegation 'space_limit' field to see if
+ * the spec requires us to flush the file on close.
+ */
+bool nfs4_delegation_flush_on_close(const struct inode *inode)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+	struct nfs_delegation *delegation;
+	bool ret = true;
+
+	rcu_read_lock();
+	delegation = rcu_dereference(nfsi->delegation);
+	if (delegation == NULL || !(delegation->type & FMODE_WRITE))
+		goto out;
+	if (atomic_long_read(&nfsi->nrequests) < delegation->pagemod_limit)
+		ret = false;
+out:
+	rcu_read_unlock();
+	return ret;
+}
+
+module_param_named(delegation_watermark, nfs_delegation_watermark, uint, 0644);