Adding upstream version 6.1.76.upstream/6.1.76upstream

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

1 files changed, 2206 insertions, 0 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
new file mode 100644
index 000000000..f41d24b54
--- /dev/null
+++ b/fs/nfs/write.c
@@ -0,0 +1,2206 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * linux/fs/nfs/write.c
+ *
+ * Write file data over NFS.
+ *
+ * Copyright (C) 1996, 1997, Olaf Kirch <okir@monad.swb.de>
+ */
+
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/file.h>
+#include <linux/writeback.h>
+#include <linux/swap.h>
+#include <linux/migrate.h>
+
+#include <linux/sunrpc/clnt.h>
+#include <linux/nfs_fs.h>
+#include <linux/nfs_mount.h>
+#include <linux/nfs_page.h>
+#include <linux/backing-dev.h>
+#include <linux/export.h>
+#include <linux/freezer.h>
+#include <linux/wait.h>
+#include <linux/iversion.h>
+
+#include <linux/uaccess.h>
+#include <linux/sched/mm.h>
+
+#include "delegation.h"
+#include "internal.h"
+#include "iostat.h"
+#include "nfs4_fs.h"
+#include "fscache.h"
+#include "pnfs.h"
+
+#include "nfstrace.h"
+
+#define NFSDBG_FACILITY		NFSDBG_PAGECACHE
+
+#define MIN_POOL_WRITE		(32)
+#define MIN_POOL_COMMIT		(4)
+
+struct nfs_io_completion {
+	void (*complete)(void *data);
+	void *data;
+	struct kref refcount;
+};
+
+/*
+ * Local function declarations
+ */
+static void nfs_redirty_request(struct nfs_page *req);
+static const struct rpc_call_ops nfs_commit_ops;
+static const struct nfs_pgio_completion_ops nfs_async_write_completion_ops;
+static const struct nfs_commit_completion_ops nfs_commit_completion_ops;
+static const struct nfs_rw_ops nfs_rw_write_ops;
+static void nfs_inode_remove_request(struct nfs_page *req);
+static void nfs_clear_request_commit(struct nfs_page *req);
+static void nfs_init_cinfo_from_inode(struct nfs_commit_info *cinfo,
+				      struct inode *inode);
+static struct nfs_page *
+nfs_page_search_commits_for_head_request_locked(struct nfs_inode *nfsi,
+						struct page *page);
+
+static struct kmem_cache *nfs_wdata_cachep;
+static mempool_t *nfs_wdata_mempool;
+static struct kmem_cache *nfs_cdata_cachep;
+static mempool_t *nfs_commit_mempool;
+
+struct nfs_commit_data *nfs_commitdata_alloc(void)
+{
+	struct nfs_commit_data *p;
+
+	p = kmem_cache_zalloc(nfs_cdata_cachep, nfs_io_gfp_mask());
+	if (!p) {
+		p = mempool_alloc(nfs_commit_mempool, GFP_NOWAIT);
+		if (!p)
+			return NULL;
+		memset(p, 0, sizeof(*p));
+	}
+	INIT_LIST_HEAD(&p->pages);
+	return p;
+}
+EXPORT_SYMBOL_GPL(nfs_commitdata_alloc);
+
+void nfs_commit_free(struct nfs_commit_data *p)
+{
+	mempool_free(p, nfs_commit_mempool);
+}
+EXPORT_SYMBOL_GPL(nfs_commit_free);
+
+static struct nfs_pgio_header *nfs_writehdr_alloc(void)
+{
+	struct nfs_pgio_header *p;
+
+	p = kmem_cache_zalloc(nfs_wdata_cachep, nfs_io_gfp_mask());
+	if (!p) {
+		p = mempool_alloc(nfs_wdata_mempool, GFP_NOWAIT);
+		if (!p)
+			return NULL;
+		memset(p, 0, sizeof(*p));
+	}
+	p->rw_mode = FMODE_WRITE;
+	return p;
+}
+
+static void nfs_writehdr_free(struct nfs_pgio_header *hdr)
+{
+	mempool_free(hdr, nfs_wdata_mempool);
+}
+
+static struct nfs_io_completion *nfs_io_completion_alloc(gfp_t gfp_flags)
+{
+	return kmalloc(sizeof(struct nfs_io_completion), gfp_flags);
+}
+
+static void nfs_io_completion_init(struct nfs_io_completion *ioc,
+		void (*complete)(void *), void *data)
+{
+	ioc->complete = complete;
+	ioc->data = data;
+	kref_init(&ioc->refcount);
+}
+
+static void nfs_io_completion_release(struct kref *kref)
+{
+	struct nfs_io_completion *ioc = container_of(kref,
+			struct nfs_io_completion, refcount);
+	ioc->complete(ioc->data);
+	kfree(ioc);
+}
+
+static void nfs_io_completion_get(struct nfs_io_completion *ioc)
+{
+	if (ioc != NULL)
+		kref_get(&ioc->refcount);
+}
+
+static void nfs_io_completion_put(struct nfs_io_completion *ioc)
+{
+	if (ioc != NULL)
+		kref_put(&ioc->refcount, nfs_io_completion_release);
+}
+
+static void
+nfs_page_set_inode_ref(struct nfs_page *req, struct inode *inode)
+{
+	if (!test_and_set_bit(PG_INODE_REF, &req->wb_flags)) {
+		kref_get(&req->wb_kref);
+		atomic_long_inc(&NFS_I(inode)->nrequests);
+	}
+}
+
+static int
+nfs_cancel_remove_inode(struct nfs_page *req, struct inode *inode)
+{
+	int ret;
+
+	if (!test_bit(PG_REMOVE, &req->wb_flags))
+		return 0;
+	ret = nfs_page_group_lock(req);
+	if (ret)
+		return ret;
+	if (test_and_clear_bit(PG_REMOVE, &req->wb_flags))
+		nfs_page_set_inode_ref(req, inode);
+	nfs_page_group_unlock(req);
+	return 0;
+}
+
+static struct nfs_page *
+nfs_page_private_request(struct page *page)
+{
+	if (!PagePrivate(page))
+		return NULL;
+	return (struct nfs_page *)page_private(page);
+}
+
+/*
+ * nfs_page_find_head_request_locked - find head request associated with @page
+ *
+ * must be called while holding the inode lock.
+ *
+ * returns matching head request with reference held, or NULL if not found.
+ */
+static struct nfs_page *
+nfs_page_find_private_request(struct page *page)
+{
+	struct address_space *mapping = page_file_mapping(page);
+	struct nfs_page *req;
+
+	if (!PagePrivate(page))
+		return NULL;
+	spin_lock(&mapping->private_lock);
+	req = nfs_page_private_request(page);
+	if (req) {
+		WARN_ON_ONCE(req->wb_head != req);
+		kref_get(&req->wb_kref);
+	}
+	spin_unlock(&mapping->private_lock);
+	return req;
+}
+
+static struct nfs_page *
+nfs_page_find_swap_request(struct page *page)
+{
+	struct inode *inode = page_file_mapping(page)->host;
+	struct nfs_inode *nfsi = NFS_I(inode);
+	struct nfs_page *req = NULL;
+	if (!PageSwapCache(page))
+		return NULL;
+	mutex_lock(&nfsi->commit_mutex);
+	if (PageSwapCache(page)) {
+		req = nfs_page_search_commits_for_head_request_locked(nfsi,
+			page);
+		if (req) {
+			WARN_ON_ONCE(req->wb_head != req);
+			kref_get(&req->wb_kref);
+		}
+	}
+	mutex_unlock(&nfsi->commit_mutex);
+	return req;
+}
+
+/*
+ * nfs_page_find_head_request - find head request associated with @page
+ *
+ * returns matching head request with reference held, or NULL if not found.
+ */
+static struct nfs_page *nfs_page_find_head_request(struct page *page)
+{
+	struct nfs_page *req;
+
+	req = nfs_page_find_private_request(page);
+	if (!req)
+		req = nfs_page_find_swap_request(page);
+	return req;
+}
+
+static struct nfs_page *nfs_find_and_lock_page_request(struct page *page)
+{
+	struct inode *inode = page_file_mapping(page)->host;
+	struct nfs_page *req, *head;
+	int ret;
+
+	for (;;) {
+		req = nfs_page_find_head_request(page);
+		if (!req)
+			return req;
+		head = nfs_page_group_lock_head(req);
+		if (head != req)
+			nfs_release_request(req);
+		if (IS_ERR(head))
+			return head;
+		ret = nfs_cancel_remove_inode(head, inode);
+		if (ret < 0) {
+			nfs_unlock_and_release_request(head);
+			return ERR_PTR(ret);
+		}
+		/* Ensure that nobody removed the request before we locked it */
+		if (head == nfs_page_private_request(page))
+			break;
+		if (PageSwapCache(page))
+			break;
+		nfs_unlock_and_release_request(head);
+	}
+	return head;
+}
+
+/* Adjust the file length if we're writing beyond the end */
+static void nfs_grow_file(struct page *page, unsigned int offset, unsigned int count)
+{
+	struct inode *inode = page_file_mapping(page)->host;
+	loff_t end, i_size;
+	pgoff_t end_index;
+
+	spin_lock(&inode->i_lock);
+	i_size = i_size_read(inode);
+	end_index = (i_size - 1) >> PAGE_SHIFT;
+	if (i_size > 0 && page_index(page) < end_index)
+		goto out;
+	end = page_file_offset(page) + ((loff_t)offset+count);
+	if (i_size >= end)
+		goto out;
+	trace_nfs_size_grow(inode, end);
+	i_size_write(inode, end);
+	NFS_I(inode)->cache_validity &= ~NFS_INO_INVALID_SIZE;
+	nfs_inc_stats(inode, NFSIOS_EXTENDWRITE);
+out:
+	spin_unlock(&inode->i_lock);
+	nfs_fscache_invalidate(inode, 0);
+}
+
+/* A writeback failed: mark the page as bad, and invalidate the page cache */
+static void nfs_set_pageerror(struct address_space *mapping)
+{
+	struct inode *inode = mapping->host;
+
+	nfs_zap_mapping(mapping->host, mapping);
+	/* Force file size revalidation */
+	spin_lock(&inode->i_lock);
+	nfs_set_cache_invalid(inode, NFS_INO_REVAL_FORCED |
+					     NFS_INO_INVALID_CHANGE |
+					     NFS_INO_INVALID_SIZE);
+	spin_unlock(&inode->i_lock);
+}
+
+static void nfs_mapping_set_error(struct page *page, int error)
+{
+	struct address_space *mapping = page_file_mapping(page);
+
+	SetPageError(page);
+	filemap_set_wb_err(mapping, error);
+	if (mapping->host)
+		errseq_set(&mapping->host->i_sb->s_wb_err,
+			   error == -ENOSPC ? -ENOSPC : -EIO);
+	nfs_set_pageerror(mapping);
+}
+
+/*
+ * nfs_page_group_search_locked
+ * @head - head request of page group
+ * @page_offset - offset into page
+ *
+ * Search page group with head @head to find a request that contains the
+ * page offset @page_offset.
+ *
+ * Returns a pointer to the first matching nfs request, or NULL if no
+ * match is found.
+ *
+ * Must be called with the page group lock held
+ */
+static struct nfs_page *
+nfs_page_group_search_locked(struct nfs_page *head, unsigned int page_offset)
+{
+	struct nfs_page *req;
+
+	req = head;
+	do {
+		if (page_offset >= req->wb_pgbase &&
+		    page_offset < (req->wb_pgbase + req->wb_bytes))
+			return req;
+
+		req = req->wb_this_page;
+	} while (req != head);
+
+	return NULL;
+}
+
+/*
+ * nfs_page_group_covers_page
+ * @head - head request of page group
+ *
+ * Return true if the page group with head @head covers the whole page,
+ * returns false otherwise
+ */
+static bool nfs_page_group_covers_page(struct nfs_page *req)
+{
+	struct nfs_page *tmp;
+	unsigned int pos = 0;
+	unsigned int len = nfs_page_length(req->wb_page);
+
+	nfs_page_group_lock(req);
+
+	for (;;) {
+		tmp = nfs_page_group_search_locked(req->wb_head, pos);
+		if (!tmp)
+			break;
+		pos = tmp->wb_pgbase + tmp->wb_bytes;
+	}
+
+	nfs_page_group_unlock(req);
+	return pos >= len;
+}
+
+/* We can set the PG_uptodate flag if we see that a write request
+ * covers the full page.
+ */
+static void nfs_mark_uptodate(struct nfs_page *req)
+{
+	if (PageUptodate(req->wb_page))
+		return;
+	if (!nfs_page_group_covers_page(req))
+		return;
+	SetPageUptodate(req->wb_page);
+}
+
+static int wb_priority(struct writeback_control *wbc)
+{
+	int ret = 0;
+
+	if (wbc->sync_mode == WB_SYNC_ALL)
+		ret = FLUSH_COND_STABLE;
+	return ret;
+}
+
+/*
+ * NFS congestion control
+ */
+
+int nfs_congestion_kb;
+
+#define NFS_CONGESTION_ON_THRESH 	(nfs_congestion_kb >> (PAGE_SHIFT-10))
+#define NFS_CONGESTION_OFF_THRESH	\
+	(NFS_CONGESTION_ON_THRESH - (NFS_CONGESTION_ON_THRESH >> 2))
+
+static void nfs_set_page_writeback(struct page *page)
+{
+	struct inode *inode = page_file_mapping(page)->host;
+	struct nfs_server *nfss = NFS_SERVER(inode);
+	int ret = test_set_page_writeback(page);
+
+	WARN_ON_ONCE(ret != 0);
+
+	if (atomic_long_inc_return(&nfss->writeback) >
+			NFS_CONGESTION_ON_THRESH)
+		nfss->write_congested = 1;
+}
+
+static void nfs_end_page_writeback(struct nfs_page *req)
+{
+	struct inode *inode = page_file_mapping(req->wb_page)->host;
+	struct nfs_server *nfss = NFS_SERVER(inode);
+	bool is_done;
+
+	is_done = nfs_page_group_sync_on_bit(req, PG_WB_END);
+	nfs_unlock_request(req);
+	if (!is_done)
+		return;
+
+	end_page_writeback(req->wb_page);
+	if (atomic_long_dec_return(&nfss->writeback) < NFS_CONGESTION_OFF_THRESH)
+		nfss->write_congested = 0;
+}
+
+/*
+ * nfs_destroy_unlinked_subrequests - destroy recently unlinked subrequests
+ *
+ * @destroy_list - request list (using wb_this_page) terminated by @old_head
+ * @old_head - the old head of the list
+ *
+ * All subrequests must be locked and removed from all lists, so at this point
+ * they are only "active" in this function, and possibly in nfs_wait_on_request
+ * with a reference held by some other context.
+ */
+static void
+nfs_destroy_unlinked_subrequests(struct nfs_page *destroy_list,
+				 struct nfs_page *old_head,
+				 struct inode *inode)
+{
+	while (destroy_list) {
+		struct nfs_page *subreq = destroy_list;
+
+		destroy_list = (subreq->wb_this_page == old_head) ?
+				   NULL : subreq->wb_this_page;
+
+		/* Note: lock subreq in order to change subreq->wb_head */
+		nfs_page_set_headlock(subreq);
+		WARN_ON_ONCE(old_head != subreq->wb_head);
+
+		/* make sure old group is not used */
+		subreq->wb_this_page = subreq;
+		subreq->wb_head = subreq;
+
+		clear_bit(PG_REMOVE, &subreq->wb_flags);
+
+		/* Note: races with nfs_page_group_destroy() */
+		if (!kref_read(&subreq->wb_kref)) {
+			/* Check if we raced with nfs_page_group_destroy() */
+			if (test_and_clear_bit(PG_TEARDOWN, &subreq->wb_flags)) {
+				nfs_page_clear_headlock(subreq);
+				nfs_free_request(subreq);
+			} else
+				nfs_page_clear_headlock(subreq);
+			continue;
+		}
+		nfs_page_clear_headlock(subreq);
+
+		nfs_release_request(old_head);
+
+		if (test_and_clear_bit(PG_INODE_REF, &subreq->wb_flags)) {
+			nfs_release_request(subreq);
+			atomic_long_dec(&NFS_I(inode)->nrequests);
+		}
+
+		/* subreq is now totally disconnected from page group or any
+		 * write / commit lists. last chance to wake any waiters */
+		nfs_unlock_and_release_request(subreq);
+	}
+}
+
+/*
+ * nfs_join_page_group - destroy subrequests of the head req
+ * @head: the page used to lookup the "page group" of nfs_page structures
+ * @inode: Inode to which the request belongs.
+ *
+ * This function joins all sub requests to the head request by first
+ * locking all requests in the group, cancelling any pending operations
+ * and finally updating the head request to cover the whole range covered by
+ * the (former) group.  All subrequests are removed from any write or commit
+ * lists, unlinked from the group and destroyed.
+ */
+void
+nfs_join_page_group(struct nfs_page *head, struct inode *inode)
+{
+	struct nfs_page *subreq;
+	struct nfs_page *destroy_list = NULL;
+	unsigned int pgbase, off, bytes;
+
+	pgbase = head->wb_pgbase;
+	bytes = head->wb_bytes;
+	off = head->wb_offset;
+	for (subreq = head->wb_this_page; subreq != head;
+			subreq = subreq->wb_this_page) {
+		/* Subrequests should always form a contiguous range */
+		if (pgbase > subreq->wb_pgbase) {
+			off -= pgbase - subreq->wb_pgbase;
+			bytes += pgbase - subreq->wb_pgbase;
+			pgbase = subreq->wb_pgbase;
+		}
+		bytes = max(subreq->wb_pgbase + subreq->wb_bytes
+				- pgbase, bytes);
+	}
+
+	/* Set the head request's range to cover the former page group */
+	head->wb_pgbase = pgbase;
+	head->wb_bytes = bytes;
+	head->wb_offset = off;
+
+	/* Now that all requests are locked, make sure they aren't on any list.
+	 * Commit list removal accounting is done after locks are dropped */
+	subreq = head;
+	do {
+		nfs_clear_request_commit(subreq);
+		subreq = subreq->wb_this_page;
+	} while (subreq != head);
+
+	/* unlink subrequests from head, destroy them later */
+	if (head->wb_this_page != head) {
+		/* destroy list will be terminated by head */
+		destroy_list = head->wb_this_page;
+		head->wb_this_page = head;
+	}
+
+	nfs_destroy_unlinked_subrequests(destroy_list, head, inode);
+}
+
+/*
+ * nfs_lock_and_join_requests - join all subreqs to the head req
+ * @page: the page used to lookup the "page group" of nfs_page structures
+ *
+ * This function joins all sub requests to the head request by first
+ * locking all requests in the group, cancelling any pending operations
+ * and finally updating the head request to cover the whole range covered by
+ * the (former) group.  All subrequests are removed from any write or commit
+ * lists, unlinked from the group and destroyed.
+ *
+ * Returns a locked, referenced pointer to the head request - which after
+ * this call is guaranteed to be the only request associated with the page.
+ * Returns NULL if no requests are found for @page, or a ERR_PTR if an
+ * error was encountered.
+ */
+static struct nfs_page *
+nfs_lock_and_join_requests(struct page *page)
+{
+	struct inode *inode = page_file_mapping(page)->host;
+	struct nfs_page *head;
+	int ret;
+
+	/*
+	 * A reference is taken only on the head request which acts as a
+	 * reference to the whole page group - the group will not be destroyed
+	 * until the head reference is released.
+	 */
+	head = nfs_find_and_lock_page_request(page);
+	if (IS_ERR_OR_NULL(head))
+		return head;
+
+	/* lock each request in the page group */
+	ret = nfs_page_group_lock_subrequests(head);
+	if (ret < 0) {
+		nfs_unlock_and_release_request(head);
+		return ERR_PTR(ret);
+	}
+
+	nfs_join_page_group(head, inode);
+
+	return head;
+}
+
+static void nfs_write_error(struct nfs_page *req, int error)
+{
+	trace_nfs_write_error(page_file_mapping(req->wb_page)->host, req,
+			      error);
+	nfs_mapping_set_error(req->wb_page, error);
+	nfs_inode_remove_request(req);
+	nfs_end_page_writeback(req);
+	nfs_release_request(req);
+}
+
+/*
+ * Find an associated nfs write request, and prepare to flush it out
+ * May return an error if the user signalled nfs_wait_on_request().
+ */
+static int nfs_page_async_flush(struct page *page,
+				struct writeback_control *wbc,
+				struct nfs_pageio_descriptor *pgio)
+{
+	struct nfs_page *req;
+	int ret = 0;
+
+	req = nfs_lock_and_join_requests(page);
+	if (!req)
+		goto out;
+	ret = PTR_ERR(req);
+	if (IS_ERR(req))
+		goto out;
+
+	nfs_set_page_writeback(page);
+	WARN_ON_ONCE(test_bit(PG_CLEAN, &req->wb_flags));
+
+	/* If there is a fatal error that covers this write, just exit */
+	ret = pgio->pg_error;
+	if (nfs_error_is_fatal_on_server(ret))
+		goto out_launder;
+
+	ret = 0;
+	if (!nfs_pageio_add_request(pgio, req)) {
+		ret = pgio->pg_error;
+		/*
+		 * Remove the problematic req upon fatal errors on the server
+		 */
+		if (nfs_error_is_fatal_on_server(ret))
+			goto out_launder;
+		if (wbc->sync_mode == WB_SYNC_NONE)
+			ret = AOP_WRITEPAGE_ACTIVATE;
+		redirty_page_for_writepage(wbc, page);
+		nfs_redirty_request(req);
+		pgio->pg_error = 0;
+	} else
+		nfs_add_stats(page_file_mapping(page)->host,
+				NFSIOS_WRITEPAGES, 1);
+out:
+	return ret;
+out_launder:
+	nfs_write_error(req, ret);
+	return 0;
+}
+
+static int nfs_do_writepage(struct page *page, struct writeback_control *wbc,
+			    struct nfs_pageio_descriptor *pgio)
+{
+	nfs_pageio_cond_complete(pgio, page_index(page));
+	return nfs_page_async_flush(page, wbc, pgio);
+}
+
+/*
+ * Write an mmapped page to the server.
+ */
+static int nfs_writepage_locked(struct page *page,
+				struct writeback_control *wbc)
+{
+	struct nfs_pageio_descriptor pgio;
+	struct inode *inode = page_file_mapping(page)->host;
+	int err;
+
+	if (wbc->sync_mode == WB_SYNC_NONE &&
+	    NFS_SERVER(inode)->write_congested)
+		return AOP_WRITEPAGE_ACTIVATE;
+
+	nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGE);
+	nfs_pageio_init_write(&pgio, inode, 0,
+				false, &nfs_async_write_completion_ops);
+	err = nfs_do_writepage(page, wbc, &pgio);
+	pgio.pg_error = 0;
+	nfs_pageio_complete(&pgio);
+	return err;
+}
+
+int nfs_writepage(struct page *page, struct writeback_control *wbc)
+{
+	int ret;
+
+	ret = nfs_writepage_locked(page, wbc);
+	if (ret != AOP_WRITEPAGE_ACTIVATE)
+		unlock_page(page);
+	return ret;
+}
+
+static int nfs_writepages_callback(struct page *page, struct writeback_control *wbc, void *data)
+{
+	int ret;
+
+	ret = nfs_do_writepage(page, wbc, data);
+	if (ret != AOP_WRITEPAGE_ACTIVATE)
+		unlock_page(page);
+	return ret;
+}
+
+static void nfs_io_completion_commit(void *inode)
+{
+	nfs_commit_inode(inode, 0);
+}
+
+int nfs_writepages(struct address_space *mapping, struct writeback_control *wbc)
+{
+	struct inode *inode = mapping->host;
+	struct nfs_pageio_descriptor pgio;
+	struct nfs_io_completion *ioc = NULL;
+	unsigned int mntflags = NFS_SERVER(inode)->flags;
+	int priority = 0;
+	int err;
+
+	if (wbc->sync_mode == WB_SYNC_NONE &&
+	    NFS_SERVER(inode)->write_congested)
+		return 0;
+
+	nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGES);
+
+	if (!(mntflags & NFS_MOUNT_WRITE_EAGER) || wbc->for_kupdate ||
+	    wbc->for_background || wbc->for_sync || wbc->for_reclaim) {
+		ioc = nfs_io_completion_alloc(GFP_KERNEL);
+		if (ioc)
+			nfs_io_completion_init(ioc, nfs_io_completion_commit,
+					       inode);
+		priority = wb_priority(wbc);
+	}
+
+	do {
+		nfs_pageio_init_write(&pgio, inode, priority, false,
+				      &nfs_async_write_completion_ops);
+		pgio.pg_io_completion = ioc;
+		err = write_cache_pages(mapping, wbc, nfs_writepages_callback,
+					&pgio);
+		pgio.pg_error = 0;
+		nfs_pageio_complete(&pgio);
+	} while (err < 0 && !nfs_error_is_fatal(err));
+	nfs_io_completion_put(ioc);
+
+	if (err < 0)
+		goto out_err;
+	return 0;
+out_err:
+	return err;
+}
+
+/*
+ * Insert a write request into an inode
+ */
+static void nfs_inode_add_request(struct inode *inode, struct nfs_page *req)
+{
+	struct address_space *mapping = page_file_mapping(req->wb_page);
+	struct nfs_inode *nfsi = NFS_I(inode);
+
+	WARN_ON_ONCE(req->wb_this_page != req);
+
+	/* Lock the request! */
+	nfs_lock_request(req);
+
+	/*
+	 * Swap-space should not get truncated. Hence no need to plug the race
+	 * with invalidate/truncate.
+	 */
+	spin_lock(&mapping->private_lock);
+	if (likely(!PageSwapCache(req->wb_page))) {
+		set_bit(PG_MAPPED, &req->wb_flags);
+		SetPagePrivate(req->wb_page);
+		set_page_private(req->wb_page, (unsigned long)req);
+	}
+	spin_unlock(&mapping->private_lock);
+	atomic_long_inc(&nfsi->nrequests);
+	/* this a head request for a page group - mark it as having an
+	 * extra reference so sub groups can follow suit.
+	 * This flag also informs pgio layer when to bump nrequests when
+	 * adding subrequests. */
+	WARN_ON(test_and_set_bit(PG_INODE_REF, &req->wb_flags));
+	kref_get(&req->wb_kref);
+}
+
+/*
+ * Remove a write request from an inode
+ */
+static void nfs_inode_remove_request(struct nfs_page *req)
+{
+	struct address_space *mapping = page_file_mapping(req->wb_page);
+	struct inode *inode = mapping->host;
+	struct nfs_inode *nfsi = NFS_I(inode);
+	struct nfs_page *head;
+
+	if (nfs_page_group_sync_on_bit(req, PG_REMOVE)) {
+		head = req->wb_head;
+
+		spin_lock(&mapping->private_lock);
+		if (likely(head->wb_page && !PageSwapCache(head->wb_page))) {
+			set_page_private(head->wb_page, 0);
+			ClearPagePrivate(head->wb_page);
+			clear_bit(PG_MAPPED, &head->wb_flags);
+		}
+		spin_unlock(&mapping->private_lock);
+	}
+
+	if (test_and_clear_bit(PG_INODE_REF, &req->wb_flags)) {
+		nfs_release_request(req);
+		atomic_long_dec(&nfsi->nrequests);
+	}
+}
+
+static void
+nfs_mark_request_dirty(struct nfs_page *req)
+{
+	if (req->wb_page)
+		__set_page_dirty_nobuffers(req->wb_page);
+}
+
+/*
+ * nfs_page_search_commits_for_head_request_locked
+ *
+ * Search through commit lists on @inode for the head request for @page.
+ * Must be called while holding the inode (which is cinfo) lock.
+ *
+ * Returns the head request if found, or NULL if not found.
+ */
+static struct nfs_page *
+nfs_page_search_commits_for_head_request_locked(struct nfs_inode *nfsi,
+						struct page *page)
+{
+	struct nfs_page *freq, *t;
+	struct nfs_commit_info cinfo;
+	struct inode *inode = &nfsi->vfs_inode;
+
+	nfs_init_cinfo_from_inode(&cinfo, inode);
+
+	/* search through pnfs commit lists */
+	freq = pnfs_search_commit_reqs(inode, &cinfo, page);
+	if (freq)
+		return freq->wb_head;
+
+	/* Linearly search the commit list for the correct request */
+	list_for_each_entry_safe(freq, t, &cinfo.mds->list, wb_list) {
+		if (freq->wb_page == page)
+			return freq->wb_head;
+	}
+
+	return NULL;
+}
+
+/**
+ * nfs_request_add_commit_list_locked - add request to a commit list
+ * @req: pointer to a struct nfs_page
+ * @dst: commit list head
+ * @cinfo: holds list lock and accounting info
+ *
+ * This sets the PG_CLEAN bit, updates the cinfo count of
+ * number of outstanding requests requiring a commit as well as
+ * the MM page stats.
+ *
+ * The caller must hold NFS_I(cinfo->inode)->commit_mutex, and the
+ * nfs_page lock.
+ */
+void
+nfs_request_add_commit_list_locked(struct nfs_page *req, struct list_head *dst,
+			    struct nfs_commit_info *cinfo)
+{
+	set_bit(PG_CLEAN, &req->wb_flags);
+	nfs_list_add_request(req, dst);
+	atomic_long_inc(&cinfo->mds->ncommit);
+}
+EXPORT_SYMBOL_GPL(nfs_request_add_commit_list_locked);
+
+/**
+ * nfs_request_add_commit_list - add request to a commit list
+ * @req: pointer to a struct nfs_page
+ * @cinfo: holds list lock and accounting info
+ *
+ * This sets the PG_CLEAN bit, updates the cinfo count of
+ * number of outstanding requests requiring a commit as well as
+ * the MM page stats.
+ *
+ * The caller must _not_ hold the cinfo->lock, but must be
+ * holding the nfs_page lock.
+ */
+void
+nfs_request_add_commit_list(struct nfs_page *req, struct nfs_commit_info *cinfo)
+{
+	mutex_lock(&NFS_I(cinfo->inode)->commit_mutex);
+	nfs_request_add_commit_list_locked(req, &cinfo->mds->list, cinfo);
+	mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
+	if (req->wb_page)
+		nfs_mark_page_unstable(req->wb_page, cinfo);
+}
+EXPORT_SYMBOL_GPL(nfs_request_add_commit_list);
+
+/**
+ * nfs_request_remove_commit_list - Remove request from a commit list
+ * @req: pointer to a nfs_page
+ * @cinfo: holds list lock and accounting info
+ *
+ * This clears the PG_CLEAN bit, and updates the cinfo's count of
+ * number of outstanding requests requiring a commit
+ * It does not update the MM page stats.
+ *
+ * The caller _must_ hold the cinfo->lock and the nfs_page lock.
+ */
+void
+nfs_request_remove_commit_list(struct nfs_page *req,
+			       struct nfs_commit_info *cinfo)
+{
+	if (!test_and_clear_bit(PG_CLEAN, &(req)->wb_flags))
+		return;
+	nfs_list_remove_request(req);
+	atomic_long_dec(&cinfo->mds->ncommit);
+}
+EXPORT_SYMBOL_GPL(nfs_request_remove_commit_list);
+
+static void nfs_init_cinfo_from_inode(struct nfs_commit_info *cinfo,
+				      struct inode *inode)
+{
+	cinfo->inode = inode;
+	cinfo->mds = &NFS_I(inode)->commit_info;
+	cinfo->ds = pnfs_get_ds_info(inode);
+	cinfo->dreq = NULL;
+	cinfo->completion_ops = &nfs_commit_completion_ops;
+}
+
+void nfs_init_cinfo(struct nfs_commit_info *cinfo,
+		    struct inode *inode,
+		    struct nfs_direct_req *dreq)
+{
+	if (dreq)
+		nfs_init_cinfo_from_dreq(cinfo, dreq);
+	else
+		nfs_init_cinfo_from_inode(cinfo, inode);
+}
+EXPORT_SYMBOL_GPL(nfs_init_cinfo);
+
+/*
+ * Add a request to the inode's commit list.
+ */
+void
+nfs_mark_request_commit(struct nfs_page *req, struct pnfs_layout_segment *lseg,
+			struct nfs_commit_info *cinfo, u32 ds_commit_idx)
+{
+	if (pnfs_mark_request_commit(req, lseg, cinfo, ds_commit_idx))
+		return;
+	nfs_request_add_commit_list(req, cinfo);
+}
+
+static void
+nfs_clear_page_commit(struct page *page)
+{
+	dec_node_page_state(page, NR_WRITEBACK);
+	dec_wb_stat(&inode_to_bdi(page_file_mapping(page)->host)->wb,
+		    WB_WRITEBACK);
+}
+
+/* Called holding the request lock on @req */
+static void
+nfs_clear_request_commit(struct nfs_page *req)
+{
+	if (test_bit(PG_CLEAN, &req->wb_flags)) {
+		struct nfs_open_context *ctx = nfs_req_openctx(req);
+		struct inode *inode = d_inode(ctx->dentry);
+		struct nfs_commit_info cinfo;
+
+		nfs_init_cinfo_from_inode(&cinfo, inode);
+		mutex_lock(&NFS_I(inode)->commit_mutex);
+		if (!pnfs_clear_request_commit(req, &cinfo)) {
+			nfs_request_remove_commit_list(req, &cinfo);
+		}
+		mutex_unlock(&NFS_I(inode)->commit_mutex);
+		nfs_clear_page_commit(req->wb_page);
+	}
+}
+
+int nfs_write_need_commit(struct nfs_pgio_header *hdr)
+{
+	if (hdr->verf.committed == NFS_DATA_SYNC)
+		return hdr->lseg == NULL;
+	return hdr->verf.committed != NFS_FILE_SYNC;
+}
+
+static void nfs_async_write_init(struct nfs_pgio_header *hdr)
+{
+	nfs_io_completion_get(hdr->io_completion);
+}
+
+static void nfs_write_completion(struct nfs_pgio_header *hdr)
+{
+	struct nfs_commit_info cinfo;
+	unsigned long bytes = 0;
+
+	if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
+		goto out;
+	nfs_init_cinfo_from_inode(&cinfo, hdr->inode);
+	while (!list_empty(&hdr->pages)) {
+		struct nfs_page *req = nfs_list_entry(hdr->pages.next);
+
+		bytes += req->wb_bytes;
+		nfs_list_remove_request(req);
+		if (test_bit(NFS_IOHDR_ERROR, &hdr->flags) &&
+		    (hdr->good_bytes < bytes)) {
+			trace_nfs_comp_error(hdr->inode, req, hdr->error);
+			nfs_mapping_set_error(req->wb_page, hdr->error);
+			goto remove_req;
+		}
+		if (nfs_write_need_commit(hdr)) {
+			/* Reset wb_nio, since the write was successful. */
+			req->wb_nio = 0;
+			memcpy(&req->wb_verf, &hdr->verf.verifier, sizeof(req->wb_verf));
+			nfs_mark_request_commit(req, hdr->lseg, &cinfo,
+				hdr->pgio_mirror_idx);
+			goto next;
+		}
+remove_req:
+		nfs_inode_remove_request(req);
+next:
+		nfs_end_page_writeback(req);
+		nfs_release_request(req);
+	}
+out:
+	nfs_io_completion_put(hdr->io_completion);
+	hdr->release(hdr);
+}
+
+unsigned long
+nfs_reqs_to_commit(struct nfs_commit_info *cinfo)
+{
+	return atomic_long_read(&cinfo->mds->ncommit);
+}
+
+/* NFS_I(cinfo->inode)->commit_mutex held by caller */
+int
+nfs_scan_commit_list(struct list_head *src, struct list_head *dst,
+		     struct nfs_commit_info *cinfo, int max)
+{
+	struct nfs_page *req, *tmp;
+	int ret = 0;
+
+	list_for_each_entry_safe(req, tmp, src, wb_list) {
+		kref_get(&req->wb_kref);
+		if (!nfs_lock_request(req)) {
+			nfs_release_request(req);
+			continue;
+		}
+		nfs_request_remove_commit_list(req, cinfo);
+		clear_bit(PG_COMMIT_TO_DS, &req->wb_flags);
+		nfs_list_add_request(req, dst);
+		ret++;
+		if ((ret == max) && !cinfo->dreq)
+			break;
+		cond_resched();
+	}
+	return ret;
+}
+EXPORT_SYMBOL_GPL(nfs_scan_commit_list);
+
+/*
+ * nfs_scan_commit - Scan an inode for commit requests
+ * @inode: NFS inode to scan
+ * @dst: mds destination list
+ * @cinfo: mds and ds lists of reqs ready to commit
+ *
+ * Moves requests from the inode's 'commit' request list.
+ * The requests are *not* checked to ensure that they form a contiguous set.
+ */
+int
+nfs_scan_commit(struct inode *inode, struct list_head *dst,
+		struct nfs_commit_info *cinfo)
+{
+	int ret = 0;
+
+	if (!atomic_long_read(&cinfo->mds->ncommit))
+		return 0;
+	mutex_lock(&NFS_I(cinfo->inode)->commit_mutex);
+	if (atomic_long_read(&cinfo->mds->ncommit) > 0) {
+		const int max = INT_MAX;
+
+		ret = nfs_scan_commit_list(&cinfo->mds->list, dst,
+					   cinfo, max);
+		ret += pnfs_scan_commit_lists(inode, cinfo, max - ret);
+	}
+	mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
+	return ret;
+}
+
+/*
+ * Search for an existing write request, and attempt to update
+ * it to reflect a new dirty region on a given page.
+ *
+ * If the attempt fails, then the existing request is flushed out
+ * to disk.
+ */
+static struct nfs_page *nfs_try_to_update_request(struct inode *inode,
+		struct page *page,
+		unsigned int offset,
+		unsigned int bytes)
+{
+	struct nfs_page *req;
+	unsigned int rqend;
+	unsigned int end;
+	int error;
+
+	end = offset + bytes;
+
+	req = nfs_lock_and_join_requests(page);
+	if (IS_ERR_OR_NULL(req))
+		return req;
+
+	rqend = req->wb_offset + req->wb_bytes;
+	/*
+	 * Tell the caller to flush out the request if
+	 * the offsets are non-contiguous.
+	 * Note: nfs_flush_incompatible() will already
+	 * have flushed out requests having wrong owners.
+	 */
+	if (offset > rqend || end < req->wb_offset)
+		goto out_flushme;
+
+	/* Okay, the request matches. Update the region */
+	if (offset < req->wb_offset) {
+		req->wb_offset = offset;
+		req->wb_pgbase = offset;
+	}
+	if (end > rqend)
+		req->wb_bytes = end - req->wb_offset;
+	else
+		req->wb_bytes = rqend - req->wb_offset;
+	req->wb_nio = 0;
+	return req;
+out_flushme:
+	/*
+	 * Note: we mark the request dirty here because
+	 * nfs_lock_and_join_requests() cannot preserve
+	 * commit flags, so we have to replay the write.
+	 */
+	nfs_mark_request_dirty(req);
+	nfs_unlock_and_release_request(req);
+	error = nfs_wb_page(inode, page);
+	return (error < 0) ? ERR_PTR(error) : NULL;
+}
+
+/*
+ * Try to update an existing write request, or create one if there is none.
+ *
+ * Note: Should always be called with the Page Lock held to prevent races
+ * if we have to add a new request. Also assumes that the caller has
+ * already called nfs_flush_incompatible() if necessary.
+ */
+static struct nfs_page * nfs_setup_write_request(struct nfs_open_context* ctx,
+		struct page *page, unsigned int offset, unsigned int bytes)
+{
+	struct inode *inode = page_file_mapping(page)->host;
+	struct nfs_page	*req;
+
+	req = nfs_try_to_update_request(inode, page, offset, bytes);
+	if (req != NULL)
+		goto out;
+	req = nfs_create_request(ctx, page, offset, bytes);
+	if (IS_ERR(req))
+		goto out;
+	nfs_inode_add_request(inode, req);
+out:
+	return req;
+}
+
+static int nfs_writepage_setup(struct nfs_open_context *ctx, struct page *page,
+		unsigned int offset, unsigned int count)
+{
+	struct nfs_page	*req;
+
+	req = nfs_setup_write_request(ctx, page, offset, count);
+	if (IS_ERR(req))
+		return PTR_ERR(req);
+	/* Update file length */
+	nfs_grow_file(page, offset, count);
+	nfs_mark_uptodate(req);
+	nfs_mark_request_dirty(req);
+	nfs_unlock_and_release_request(req);
+	return 0;
+}
+
+int nfs_flush_incompatible(struct file *file, struct page *page)
+{
+	struct nfs_open_context *ctx = nfs_file_open_context(file);
+	struct nfs_lock_context *l_ctx;
+	struct file_lock_context *flctx = file_inode(file)->i_flctx;
+	struct nfs_page	*req;
+	int do_flush, status;
+	/*
+	 * Look for a request corresponding to this page. If there
+	 * is one, and it belongs to another file, we flush it out
+	 * before we try to copy anything into the page. Do this
+	 * due to the lack of an ACCESS-type call in NFSv2.
+	 * Also do the same if we find a request from an existing
+	 * dropped page.
+	 */
+	do {
+		req = nfs_page_find_head_request(page);
+		if (req == NULL)
+			return 0;
+		l_ctx = req->wb_lock_context;
+		do_flush = req->wb_page != page ||
+			!nfs_match_open_context(nfs_req_openctx(req), ctx);
+		if (l_ctx && flctx &&
+		    !(list_empty_careful(&flctx->flc_posix) &&
+		      list_empty_careful(&flctx->flc_flock))) {
+			do_flush |= l_ctx->lockowner != current->files;
+		}
+		nfs_release_request(req);
+		if (!do_flush)
+			return 0;
+		status = nfs_wb_page(page_file_mapping(page)->host, page);
+	} while (status == 0);
+	return status;
+}
+
+/*
+ * Avoid buffered writes when a open context credential's key would
+ * expire soon.
+ *
+ * Returns -EACCES if the key will expire within RPC_KEY_EXPIRE_FAIL.
+ *
+ * Return 0 and set a credential flag which triggers the inode to flush
+ * and performs  NFS_FILE_SYNC writes if the key will expired within
+ * RPC_KEY_EXPIRE_TIMEO.
+ */
+int
+nfs_key_timeout_notify(struct file *filp, struct inode *inode)
+{
+	struct nfs_open_context *ctx = nfs_file_open_context(filp);
+
+	if (nfs_ctx_key_to_expire(ctx, inode) &&
+	    !rcu_access_pointer(ctx->ll_cred))
+		/* Already expired! */
+		return -EACCES;
+	return 0;
+}
+
+/*
+ * Test if the open context credential key is marked to expire soon.
+ */
+bool nfs_ctx_key_to_expire(struct nfs_open_context *ctx, struct inode *inode)
+{
+	struct rpc_auth *auth = NFS_SERVER(inode)->client->cl_auth;
+	struct rpc_cred *cred, *new, *old = NULL;
+	struct auth_cred acred = {
+		.cred = ctx->cred,
+	};
+	bool ret = false;
+
+	rcu_read_lock();
+	cred = rcu_dereference(ctx->ll_cred);
+	if (cred && !(cred->cr_ops->crkey_timeout &&
+		      cred->cr_ops->crkey_timeout(cred)))
+		goto out;
+	rcu_read_unlock();
+
+	new = auth->au_ops->lookup_cred(auth, &acred, 0);
+	if (new == cred) {
+		put_rpccred(new);
+		return true;
+	}
+	if (IS_ERR_OR_NULL(new)) {
+		new = NULL;
+		ret = true;
+	} else if (new->cr_ops->crkey_timeout &&
+		   new->cr_ops->crkey_timeout(new))
+		ret = true;
+
+	rcu_read_lock();
+	old = rcu_dereference_protected(xchg(&ctx->ll_cred,
+					     RCU_INITIALIZER(new)), 1);
+out:
+	rcu_read_unlock();
+	put_rpccred(old);
+	return ret;
+}
+
+/*
+ * If the page cache is marked as unsafe or invalid, then we can't rely on
+ * the PageUptodate() flag. In this case, we will need to turn off
+ * write optimisations that depend on the page contents being correct.
+ */
+static bool nfs_write_pageuptodate(struct page *page, struct inode *inode,
+				   unsigned int pagelen)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+
+	if (nfs_have_delegated_attributes(inode))
+		goto out;
+	if (nfsi->cache_validity &
+	    (NFS_INO_INVALID_CHANGE | NFS_INO_INVALID_SIZE))
+		return false;
+	smp_rmb();
+	if (test_bit(NFS_INO_INVALIDATING, &nfsi->flags) && pagelen != 0)
+		return false;
+out:
+	if (nfsi->cache_validity & NFS_INO_INVALID_DATA && pagelen != 0)
+		return false;
+	return PageUptodate(page) != 0;
+}
+
+static bool
+is_whole_file_wrlock(struct file_lock *fl)
+{
+	return fl->fl_start == 0 && fl->fl_end == OFFSET_MAX &&
+			fl->fl_type == F_WRLCK;
+}
+
+/* If we know the page is up to date, and we're not using byte range locks (or
+ * if we have the whole file locked for writing), it may be more efficient to
+ * extend the write to cover the entire page in order to avoid fragmentation
+ * inefficiencies.
+ *
+ * If the file is opened for synchronous writes then we can just skip the rest
+ * of the checks.
+ */
+static int nfs_can_extend_write(struct file *file, struct page *page,
+				struct inode *inode, unsigned int pagelen)
+{
+	int ret;
+	struct file_lock_context *flctx = inode->i_flctx;
+	struct file_lock *fl;
+
+	if (file->f_flags & O_DSYNC)
+		return 0;
+	if (!nfs_write_pageuptodate(page, inode, pagelen))
+		return 0;
+	if (NFS_PROTO(inode)->have_delegation(inode, FMODE_WRITE))
+		return 1;
+	if (!flctx || (list_empty_careful(&flctx->flc_flock) &&
+		       list_empty_careful(&flctx->flc_posix)))
+		return 1;
+
+	/* Check to see if there are whole file write locks */
+	ret = 0;
+	spin_lock(&flctx->flc_lock);
+	if (!list_empty(&flctx->flc_posix)) {
+		fl = list_first_entry(&flctx->flc_posix, struct file_lock,
+					fl_list);
+		if (is_whole_file_wrlock(fl))
+			ret = 1;
+	} else if (!list_empty(&flctx->flc_flock)) {
+		fl = list_first_entry(&flctx->flc_flock, struct file_lock,
+					fl_list);
+		if (fl->fl_type == F_WRLCK)
+			ret = 1;
+	}
+	spin_unlock(&flctx->flc_lock);
+	return ret;
+}
+
+/*
+ * Update and possibly write a cached page of an NFS file.
+ *
+ * XXX: Keep an eye on generic_file_read to make sure it doesn't do bad
+ * things with a page scheduled for an RPC call (e.g. invalidate it).
+ */
+int nfs_updatepage(struct file *file, struct page *page,
+		unsigned int offset, unsigned int count)
+{
+	struct nfs_open_context *ctx = nfs_file_open_context(file);
+	struct address_space *mapping = page_file_mapping(page);
+	struct inode	*inode = mapping->host;
+	unsigned int	pagelen = nfs_page_length(page);
+	int		status = 0;
+
+	nfs_inc_stats(inode, NFSIOS_VFSUPDATEPAGE);
+
+	dprintk("NFS:       nfs_updatepage(%pD2 %d@%lld)\n",
+		file, count, (long long)(page_file_offset(page) + offset));
+
+	if (!count)
+		goto out;
+
+	if (nfs_can_extend_write(file, page, inode, pagelen)) {
+		count = max(count + offset, pagelen);
+		offset = 0;
+	}
+
+	status = nfs_writepage_setup(ctx, page, offset, count);
+	if (status < 0)
+		nfs_set_pageerror(mapping);
+out:
+	dprintk("NFS:       nfs_updatepage returns %d (isize %lld)\n",
+			status, (long long)i_size_read(inode));
+	return status;
+}
+
+static int flush_task_priority(int how)
+{
+	switch (how & (FLUSH_HIGHPRI|FLUSH_LOWPRI)) {
+		case FLUSH_HIGHPRI:
+			return RPC_PRIORITY_HIGH;
+		case FLUSH_LOWPRI:
+			return RPC_PRIORITY_LOW;
+	}
+	return RPC_PRIORITY_NORMAL;
+}
+
+static void nfs_initiate_write(struct nfs_pgio_header *hdr,
+			       struct rpc_message *msg,
+			       const struct nfs_rpc_ops *rpc_ops,
+			       struct rpc_task_setup *task_setup_data, int how)
+{
+	int priority = flush_task_priority(how);
+
+	if (IS_SWAPFILE(hdr->inode))
+		task_setup_data->flags |= RPC_TASK_SWAPPER;
+	task_setup_data->priority = priority;
+	rpc_ops->write_setup(hdr, msg, &task_setup_data->rpc_client);
+	trace_nfs_initiate_write(hdr);
+}
+
+/* If a nfs_flush_* function fails, it should remove reqs from @head and
+ * call this on each, which will prepare them to be retried on next
+ * writeback using standard nfs.
+ */
+static void nfs_redirty_request(struct nfs_page *req)
+{
+	struct nfs_inode *nfsi = NFS_I(page_file_mapping(req->wb_page)->host);
+
+	/* Bump the transmission count */
+	req->wb_nio++;
+	nfs_mark_request_dirty(req);
+	atomic_long_inc(&nfsi->redirtied_pages);
+	nfs_end_page_writeback(req);
+	nfs_release_request(req);
+}
+
+static void nfs_async_write_error(struct list_head *head, int error)
+{
+	struct nfs_page	*req;
+
+	while (!list_empty(head)) {
+		req = nfs_list_entry(head->next);
+		nfs_list_remove_request(req);
+		if (nfs_error_is_fatal_on_server(error))
+			nfs_write_error(req, error);
+		else
+			nfs_redirty_request(req);
+	}
+}
+
+static void nfs_async_write_reschedule_io(struct nfs_pgio_header *hdr)
+{
+	nfs_async_write_error(&hdr->pages, 0);
+}
+
+static const struct nfs_pgio_completion_ops nfs_async_write_completion_ops = {
+	.init_hdr = nfs_async_write_init,
+	.error_cleanup = nfs_async_write_error,
+	.completion = nfs_write_completion,
+	.reschedule_io = nfs_async_write_reschedule_io,
+};
+
+void nfs_pageio_init_write(struct nfs_pageio_descriptor *pgio,
+			       struct inode *inode, int ioflags, bool force_mds,
+			       const struct nfs_pgio_completion_ops *compl_ops)
+{
+	struct nfs_server *server = NFS_SERVER(inode);
+	const struct nfs_pageio_ops *pg_ops = &nfs_pgio_rw_ops;
+
+#ifdef CONFIG_NFS_V4_1
+	if (server->pnfs_curr_ld && !force_mds)
+		pg_ops = server->pnfs_curr_ld->pg_write_ops;
+#endif
+	nfs_pageio_init(pgio, inode, pg_ops, compl_ops, &nfs_rw_write_ops,
+			server->wsize, ioflags);
+}
+EXPORT_SYMBOL_GPL(nfs_pageio_init_write);
+
+void nfs_pageio_reset_write_mds(struct nfs_pageio_descriptor *pgio)
+{
+	struct nfs_pgio_mirror *mirror;
+
+	if (pgio->pg_ops && pgio->pg_ops->pg_cleanup)
+		pgio->pg_ops->pg_cleanup(pgio);
+
+	pgio->pg_ops = &nfs_pgio_rw_ops;
+
+	nfs_pageio_stop_mirroring(pgio);
+
+	mirror = &pgio->pg_mirrors[0];
+	mirror->pg_bsize = NFS_SERVER(pgio->pg_inode)->wsize;
+}
+EXPORT_SYMBOL_GPL(nfs_pageio_reset_write_mds);
+
+
+void nfs_commit_prepare(struct rpc_task *task, void *calldata)
+{
+	struct nfs_commit_data *data = calldata;
+
+	NFS_PROTO(data->inode)->commit_rpc_prepare(task, data);
+}
+
+static void nfs_writeback_check_extend(struct nfs_pgio_header *hdr,
+		struct nfs_fattr *fattr)
+{
+	struct nfs_pgio_args *argp = &hdr->args;
+	struct nfs_pgio_res *resp = &hdr->res;
+	u64 size = argp->offset + resp->count;
+
+	if (!(fattr->valid & NFS_ATTR_FATTR_SIZE))
+		fattr->size = size;
+	if (nfs_size_to_loff_t(fattr->size) < i_size_read(hdr->inode)) {
+		fattr->valid &= ~NFS_ATTR_FATTR_SIZE;
+		return;
+	}
+	if (size != fattr->size)
+		return;
+	/* Set attribute barrier */
+	nfs_fattr_set_barrier(fattr);
+	/* ...and update size */
+	fattr->valid |= NFS_ATTR_FATTR_SIZE;
+}
+
+void nfs_writeback_update_inode(struct nfs_pgio_header *hdr)
+{
+	struct nfs_fattr *fattr = &hdr->fattr;
+	struct inode *inode = hdr->inode;
+
+	spin_lock(&inode->i_lock);
+	nfs_writeback_check_extend(hdr, fattr);
+	nfs_post_op_update_inode_force_wcc_locked(inode, fattr);
+	spin_unlock(&inode->i_lock);
+}
+EXPORT_SYMBOL_GPL(nfs_writeback_update_inode);
+
+/*
+ * This function is called when the WRITE call is complete.
+ */
+static int nfs_writeback_done(struct rpc_task *task,
+			      struct nfs_pgio_header *hdr,
+			      struct inode *inode)
+{
+	int status;
+
+	/*
+	 * ->write_done will attempt to use post-op attributes to detect
+	 * conflicting writes by other clients.  A strict interpretation
+	 * of close-to-open would allow us to continue caching even if
+	 * another writer had changed the file, but some applications
+	 * depend on tighter cache coherency when writing.
+	 */
+	status = NFS_PROTO(inode)->write_done(task, hdr);
+	if (status != 0)
+		return status;
+
+	nfs_add_stats(inode, NFSIOS_SERVERWRITTENBYTES, hdr->res.count);
+	trace_nfs_writeback_done(task, hdr);
+
+	if (task->tk_status >= 0) {
+		enum nfs3_stable_how committed = hdr->res.verf->committed;
+
+		if (committed == NFS_UNSTABLE) {
+			/*
+			 * We have some uncommitted data on the server at
+			 * this point, so ensure that we keep track of that
+			 * fact irrespective of what later writes do.
+			 */
+			set_bit(NFS_IOHDR_UNSTABLE_WRITES, &hdr->flags);
+		}
+
+		if (committed < hdr->args.stable) {
+			/* We tried a write call, but the server did not
+			 * commit data to stable storage even though we
+			 * requested it.
+			 * Note: There is a known bug in Tru64 < 5.0 in which
+			 *	 the server reports NFS_DATA_SYNC, but performs
+			 *	 NFS_FILE_SYNC. We therefore implement this checking
+			 *	 as a dprintk() in order to avoid filling syslog.
+			 */
+			static unsigned long    complain;
+
+			/* Note this will print the MDS for a DS write */
+			if (time_before(complain, jiffies)) {
+				dprintk("NFS:       faulty NFS server %s:"
+					" (committed = %d) != (stable = %d)\n",
+					NFS_SERVER(inode)->nfs_client->cl_hostname,
+					committed, hdr->args.stable);
+				complain = jiffies + 300 * HZ;
+			}
+		}
+	}
+
+	/* Deal with the suid/sgid bit corner case */
+	if (nfs_should_remove_suid(inode)) {
+		spin_lock(&inode->i_lock);
+		nfs_set_cache_invalid(inode, NFS_INO_INVALID_MODE);
+		spin_unlock(&inode->i_lock);
+	}
+	return 0;
+}
+
+/*
+ * This function is called when the WRITE call is complete.
+ */
+static void nfs_writeback_result(struct rpc_task *task,
+				 struct nfs_pgio_header *hdr)
+{
+	struct nfs_pgio_args	*argp = &hdr->args;
+	struct nfs_pgio_res	*resp = &hdr->res;
+
+	if (resp->count < argp->count) {
+		static unsigned long    complain;
+
+		/* This a short write! */
+		nfs_inc_stats(hdr->inode, NFSIOS_SHORTWRITE);
+
+		/* Has the server at least made some progress? */
+		if (resp->count == 0) {
+			if (time_before(complain, jiffies)) {
+				printk(KERN_WARNING
+				       "NFS: Server wrote zero bytes, expected %u.\n",
+				       argp->count);
+				complain = jiffies + 300 * HZ;
+			}
+			nfs_set_pgio_error(hdr, -EIO, argp->offset);
+			task->tk_status = -EIO;
+			return;
+		}
+
+		/* For non rpc-based layout drivers, retry-through-MDS */
+		if (!task->tk_ops) {
+			hdr->pnfs_error = -EAGAIN;
+			return;
+		}
+
+		/* Was this an NFSv2 write or an NFSv3 stable write? */
+		if (resp->verf->committed != NFS_UNSTABLE) {
+			/* Resend from where the server left off */
+			hdr->mds_offset += resp->count;
+			argp->offset += resp->count;
+			argp->pgbase += resp->count;
+			argp->count -= resp->count;
+		} else {
+			/* Resend as a stable write in order to avoid
+			 * headaches in the case of a server crash.
+			 */
+			argp->stable = NFS_FILE_SYNC;
+		}
+		resp->count = 0;
+		resp->verf->committed = 0;
+		rpc_restart_call_prepare(task);
+	}
+}
+
+static int wait_on_commit(struct nfs_mds_commit_info *cinfo)
+{
+	return wait_var_event_killable(&cinfo->rpcs_out,
+				       !atomic_read(&cinfo->rpcs_out));
+}
+
+static void nfs_commit_begin(struct nfs_mds_commit_info *cinfo)
+{
+	atomic_inc(&cinfo->rpcs_out);
+}
+
+bool nfs_commit_end(struct nfs_mds_commit_info *cinfo)
+{
+	if (atomic_dec_and_test(&cinfo->rpcs_out)) {
+		wake_up_var(&cinfo->rpcs_out);
+		return true;
+	}
+	return false;
+}
+
+void nfs_commitdata_release(struct nfs_commit_data *data)
+{
+	put_nfs_open_context(data->context);
+	nfs_commit_free(data);
+}
+EXPORT_SYMBOL_GPL(nfs_commitdata_release);
+
+int nfs_initiate_commit(struct rpc_clnt *clnt, struct nfs_commit_data *data,
+			const struct nfs_rpc_ops *nfs_ops,
+			const struct rpc_call_ops *call_ops,
+			int how, int flags)
+{
+	struct rpc_task *task;
+	int priority = flush_task_priority(how);
+	struct rpc_message msg = {
+		.rpc_argp = &data->args,
+		.rpc_resp = &data->res,
+		.rpc_cred = data->cred,
+	};
+	struct rpc_task_setup task_setup_data = {
+		.task = &data->task,
+		.rpc_client = clnt,
+		.rpc_message = &msg,
+		.callback_ops = call_ops,
+		.callback_data = data,
+		.workqueue = nfsiod_workqueue,
+		.flags = RPC_TASK_ASYNC | flags,
+		.priority = priority,
+	};
+
+	if (nfs_server_capable(data->inode, NFS_CAP_MOVEABLE))
+		task_setup_data.flags |= RPC_TASK_MOVEABLE;
+
+	/* Set up the initial task struct.  */
+	nfs_ops->commit_setup(data, &msg, &task_setup_data.rpc_client);
+	trace_nfs_initiate_commit(data);
+
+	dprintk("NFS: initiated commit call\n");
+
+	task = rpc_run_task(&task_setup_data);
+	if (IS_ERR(task))
+		return PTR_ERR(task);
+	if (how & FLUSH_SYNC)
+		rpc_wait_for_completion_task(task);
+	rpc_put_task(task);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nfs_initiate_commit);
+
+static loff_t nfs_get_lwb(struct list_head *head)
+{
+	loff_t lwb = 0;
+	struct nfs_page *req;
+
+	list_for_each_entry(req, head, wb_list)
+		if (lwb < (req_offset(req) + req->wb_bytes))
+			lwb = req_offset(req) + req->wb_bytes;
+
+	return lwb;
+}
+
+/*
+ * Set up the argument/result storage required for the RPC call.
+ */
+void nfs_init_commit(struct nfs_commit_data *data,
+		     struct list_head *head,
+		     struct pnfs_layout_segment *lseg,
+		     struct nfs_commit_info *cinfo)
+{
+	struct nfs_page *first;
+	struct nfs_open_context *ctx;
+	struct inode *inode;
+
+	/* Set up the RPC argument and reply structs
+	 * NB: take care not to mess about with data->commit et al. */
+
+	if (head)
+		list_splice_init(head, &data->pages);
+
+	first = nfs_list_entry(data->pages.next);
+	ctx = nfs_req_openctx(first);
+	inode = d_inode(ctx->dentry);
+
+	data->inode	  = inode;
+	data->cred	  = ctx->cred;
+	data->lseg	  = lseg; /* reference transferred */
+	/* only set lwb for pnfs commit */
+	if (lseg)
+		data->lwb = nfs_get_lwb(&data->pages);
+	data->mds_ops     = &nfs_commit_ops;
+	data->completion_ops = cinfo->completion_ops;
+	data->dreq	  = cinfo->dreq;
+
+	data->args.fh     = NFS_FH(data->inode);
+	/* Note: we always request a commit of the entire inode */
+	data->args.offset = 0;
+	data->args.count  = 0;
+	data->context     = get_nfs_open_context(ctx);
+	data->res.fattr   = &data->fattr;
+	data->res.verf    = &data->verf;
+	nfs_fattr_init(&data->fattr);
+	nfs_commit_begin(cinfo->mds);
+}
+EXPORT_SYMBOL_GPL(nfs_init_commit);
+
+void nfs_retry_commit(struct list_head *page_list,
+		      struct pnfs_layout_segment *lseg,
+		      struct nfs_commit_info *cinfo,
+		      u32 ds_commit_idx)
+{
+	struct nfs_page *req;
+
+	while (!list_empty(page_list)) {
+		req = nfs_list_entry(page_list->next);
+		nfs_list_remove_request(req);
+		nfs_mark_request_commit(req, lseg, cinfo, ds_commit_idx);
+		if (!cinfo->dreq)
+			nfs_clear_page_commit(req->wb_page);
+		nfs_unlock_and_release_request(req);
+	}
+}
+EXPORT_SYMBOL_GPL(nfs_retry_commit);
+
+static void
+nfs_commit_resched_write(struct nfs_commit_info *cinfo,
+		struct nfs_page *req)
+{
+	__set_page_dirty_nobuffers(req->wb_page);
+}
+
+/*
+ * Commit dirty pages
+ */
+static int
+nfs_commit_list(struct inode *inode, struct list_head *head, int how,
+		struct nfs_commit_info *cinfo)
+{
+	struct nfs_commit_data	*data;
+	unsigned short task_flags = 0;
+
+	/* another commit raced with us */
+	if (list_empty(head))
+		return 0;
+
+	data = nfs_commitdata_alloc();
+	if (!data) {
+		nfs_retry_commit(head, NULL, cinfo, -1);
+		return -ENOMEM;
+	}
+
+	/* Set up the argument struct */
+	nfs_init_commit(data, head, NULL, cinfo);
+	if (NFS_SERVER(inode)->nfs_client->cl_minorversion)
+		task_flags = RPC_TASK_MOVEABLE;
+	return nfs_initiate_commit(NFS_CLIENT(inode), data, NFS_PROTO(inode),
+				   data->mds_ops, how,
+				   RPC_TASK_CRED_NOREF | task_flags);
+}
+
+/*
+ * COMMIT call returned
+ */
+static void nfs_commit_done(struct rpc_task *task, void *calldata)
+{
+	struct nfs_commit_data	*data = calldata;
+
+	/* Call the NFS version-specific code */
+	NFS_PROTO(data->inode)->commit_done(task, data);
+	trace_nfs_commit_done(task, data);
+}
+
+static void nfs_commit_release_pages(struct nfs_commit_data *data)
+{
+	const struct nfs_writeverf *verf = data->res.verf;
+	struct nfs_page	*req;
+	int status = data->task.tk_status;
+	struct nfs_commit_info cinfo;
+	struct nfs_server *nfss;
+
+	while (!list_empty(&data->pages)) {
+		req = nfs_list_entry(data->pages.next);
+		nfs_list_remove_request(req);
+		if (req->wb_page)
+			nfs_clear_page_commit(req->wb_page);
+
+		dprintk("NFS:       commit (%s/%llu %d@%lld)",
+			nfs_req_openctx(req)->dentry->d_sb->s_id,
+			(unsigned long long)NFS_FILEID(d_inode(nfs_req_openctx(req)->dentry)),
+			req->wb_bytes,
+			(long long)req_offset(req));
+		if (status < 0) {
+			if (req->wb_page) {
+				trace_nfs_commit_error(data->inode, req,
+						       status);
+				nfs_mapping_set_error(req->wb_page, status);
+				nfs_inode_remove_request(req);
+			}
+			dprintk_cont(", error = %d\n", status);
+			goto next;
+		}
+
+		/* Okay, COMMIT succeeded, apparently. Check the verifier
+		 * returned by the server against all stored verfs. */
+		if (nfs_write_match_verf(verf, req)) {
+			/* We have a match */
+			if (req->wb_page)
+				nfs_inode_remove_request(req);
+			dprintk_cont(" OK\n");
+			goto next;
+		}
+		/* We have a mismatch. Write the page again */
+		dprintk_cont(" mismatch\n");
+		nfs_mark_request_dirty(req);
+		atomic_long_inc(&NFS_I(data->inode)->redirtied_pages);
+	next:
+		nfs_unlock_and_release_request(req);
+		/* Latency breaker */
+		cond_resched();
+	}
+	nfss = NFS_SERVER(data->inode);
+	if (atomic_long_read(&nfss->writeback) < NFS_CONGESTION_OFF_THRESH)
+		nfss->write_congested = 0;
+
+	nfs_init_cinfo(&cinfo, data->inode, data->dreq);
+	nfs_commit_end(cinfo.mds);
+}
+
+static void nfs_commit_release(void *calldata)
+{
+	struct nfs_commit_data *data = calldata;
+
+	data->completion_ops->completion(data);
+	nfs_commitdata_release(calldata);
+}
+
+static const struct rpc_call_ops nfs_commit_ops = {
+	.rpc_call_prepare = nfs_commit_prepare,
+	.rpc_call_done = nfs_commit_done,
+	.rpc_release = nfs_commit_release,
+};
+
+static const struct nfs_commit_completion_ops nfs_commit_completion_ops = {
+	.completion = nfs_commit_release_pages,
+	.resched_write = nfs_commit_resched_write,
+};
+
+int nfs_generic_commit_list(struct inode *inode, struct list_head *head,
+			    int how, struct nfs_commit_info *cinfo)
+{
+	int status;
+
+	status = pnfs_commit_list(inode, head, how, cinfo);
+	if (status == PNFS_NOT_ATTEMPTED)
+		status = nfs_commit_list(inode, head, how, cinfo);
+	return status;
+}
+
+static int __nfs_commit_inode(struct inode *inode, int how,
+		struct writeback_control *wbc)
+{
+	LIST_HEAD(head);
+	struct nfs_commit_info cinfo;
+	int may_wait = how & FLUSH_SYNC;
+	int ret, nscan;
+
+	how &= ~FLUSH_SYNC;
+	nfs_init_cinfo_from_inode(&cinfo, inode);
+	nfs_commit_begin(cinfo.mds);
+	for (;;) {
+		ret = nscan = nfs_scan_commit(inode, &head, &cinfo);
+		if (ret <= 0)
+			break;
+		ret = nfs_generic_commit_list(inode, &head, how, &cinfo);
+		if (ret < 0)
+			break;
+		ret = 0;
+		if (wbc && wbc->sync_mode == WB_SYNC_NONE) {
+			if (nscan < wbc->nr_to_write)
+				wbc->nr_to_write -= nscan;
+			else
+				wbc->nr_to_write = 0;
+		}
+		if (nscan < INT_MAX)
+			break;
+		cond_resched();
+	}
+	nfs_commit_end(cinfo.mds);
+	if (ret || !may_wait)
+		return ret;
+	return wait_on_commit(cinfo.mds);
+}
+
+int nfs_commit_inode(struct inode *inode, int how)
+{
+	return __nfs_commit_inode(inode, how, NULL);
+}
+EXPORT_SYMBOL_GPL(nfs_commit_inode);
+
+int nfs_write_inode(struct inode *inode, struct writeback_control *wbc)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+	int flags = FLUSH_SYNC;
+	int ret = 0;
+
+	if (wbc->sync_mode == WB_SYNC_NONE) {
+		/* no commits means nothing needs to be done */
+		if (!atomic_long_read(&nfsi->commit_info.ncommit))
+			goto check_requests_outstanding;
+
+		/* Don't commit yet if this is a non-blocking flush and there
+		 * are a lot of outstanding writes for this mapping.
+		 */
+		if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_WRITEBACK))
+			goto out_mark_dirty;
+
+		/* don't wait for the COMMIT response */
+		flags = 0;
+	}
+
+	ret = __nfs_commit_inode(inode, flags, wbc);
+	if (!ret) {
+		if (flags & FLUSH_SYNC)
+			return 0;
+	} else if (atomic_long_read(&nfsi->commit_info.ncommit))
+		goto out_mark_dirty;
+
+check_requests_outstanding:
+	if (!atomic_read(&nfsi->commit_info.rpcs_out))
+		return ret;
+out_mark_dirty:
+	__mark_inode_dirty(inode, I_DIRTY_DATASYNC);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(nfs_write_inode);
+
+/*
+ * Wrapper for filemap_write_and_wait_range()
+ *
+ * Needed for pNFS in order to ensure data becomes visible to the
+ * client.
+ */
+int nfs_filemap_write_and_wait_range(struct address_space *mapping,
+		loff_t lstart, loff_t lend)
+{
+	int ret;
+
+	ret = filemap_write_and_wait_range(mapping, lstart, lend);
+	if (ret == 0)
+		ret = pnfs_sync_inode(mapping->host, true);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(nfs_filemap_write_and_wait_range);
+
+/*
+ * flush the inode to disk.
+ */
+int nfs_wb_all(struct inode *inode)
+{
+	int ret;
+
+	trace_nfs_writeback_inode_enter(inode);
+
+	ret = filemap_write_and_wait(inode->i_mapping);
+	if (ret)
+		goto out;
+	ret = nfs_commit_inode(inode, FLUSH_SYNC);
+	if (ret < 0)
+		goto out;
+	pnfs_sync_inode(inode, true);
+	ret = 0;
+
+out:
+	trace_nfs_writeback_inode_exit(inode, ret);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(nfs_wb_all);
+
+int nfs_wb_folio_cancel(struct inode *inode, struct folio *folio)
+{
+	struct nfs_page *req;
+	int ret = 0;
+
+	folio_wait_writeback(folio);
+
+	/* blocking call to cancel all requests and join to a single (head)
+	 * request */
+	req = nfs_lock_and_join_requests(&folio->page);
+
+	if (IS_ERR(req)) {
+		ret = PTR_ERR(req);
+	} else if (req) {
+		/* all requests from this folio have been cancelled by
+		 * nfs_lock_and_join_requests, so just remove the head
+		 * request from the inode / page_private pointer and
+		 * release it */
+		nfs_inode_remove_request(req);
+		nfs_unlock_and_release_request(req);
+	}
+
+	return ret;
+}
+
+/*
+ * Write back all requests on one page - we do this before reading it.
+ */
+int nfs_wb_page(struct inode *inode, struct page *page)
+{
+	loff_t range_start = page_file_offset(page);
+	loff_t range_end = range_start + (loff_t)(PAGE_SIZE - 1);
+	struct writeback_control wbc = {
+		.sync_mode = WB_SYNC_ALL,
+		.nr_to_write = 0,
+		.range_start = range_start,
+		.range_end = range_end,
+	};
+	int ret;
+
+	trace_nfs_writeback_page_enter(inode);
+
+	for (;;) {
+		wait_on_page_writeback(page);
+		if (clear_page_dirty_for_io(page)) {
+			ret = nfs_writepage_locked(page, &wbc);
+			if (ret < 0)
+				goto out_error;
+			continue;
+		}
+		ret = 0;
+		if (!PagePrivate(page))
+			break;
+		ret = nfs_commit_inode(inode, FLUSH_SYNC);
+		if (ret < 0)
+			goto out_error;
+	}
+out_error:
+	trace_nfs_writeback_page_exit(inode, ret);
+	return ret;
+}
+
+#ifdef CONFIG_MIGRATION
+int nfs_migrate_folio(struct address_space *mapping, struct folio *dst,
+		struct folio *src, enum migrate_mode mode)
+{
+	/*
+	 * If the private flag is set, the folio is currently associated with
+	 * an in-progress read or write request. Don't try to migrate it.
+	 *
+	 * FIXME: we could do this in principle, but we'll need a way to ensure
+	 *        that we can safely release the inode reference while holding
+	 *        the folio lock.
+	 */
+	if (folio_test_private(src))
+		return -EBUSY;
+
+	if (folio_test_fscache(src)) {
+		if (mode == MIGRATE_ASYNC)
+			return -EBUSY;
+		folio_wait_fscache(src);
+	}
+
+	return migrate_folio(mapping, dst, src, mode);
+}
+#endif
+
+int __init nfs_init_writepagecache(void)
+{
+	nfs_wdata_cachep = kmem_cache_create("nfs_write_data",
+					     sizeof(struct nfs_pgio_header),
+					     0, SLAB_HWCACHE_ALIGN,
+					     NULL);
+	if (nfs_wdata_cachep == NULL)
+		return -ENOMEM;
+
+	nfs_wdata_mempool = mempool_create_slab_pool(MIN_POOL_WRITE,
+						     nfs_wdata_cachep);
+	if (nfs_wdata_mempool == NULL)
+		goto out_destroy_write_cache;
+
+	nfs_cdata_cachep = kmem_cache_create("nfs_commit_data",
+					     sizeof(struct nfs_commit_data),
+					     0, SLAB_HWCACHE_ALIGN,
+					     NULL);
+	if (nfs_cdata_cachep == NULL)
+		goto out_destroy_write_mempool;
+
+	nfs_commit_mempool = mempool_create_slab_pool(MIN_POOL_COMMIT,
+						      nfs_cdata_cachep);
+	if (nfs_commit_mempool == NULL)
+		goto out_destroy_commit_cache;
+
+	/*
+	 * NFS congestion size, scale with available memory.
+	 *
+	 *  64MB:    8192k
+	 * 128MB:   11585k
+	 * 256MB:   16384k
+	 * 512MB:   23170k
+	 *   1GB:   32768k
+	 *   2GB:   46340k
+	 *   4GB:   65536k
+	 *   8GB:   92681k
+	 *  16GB:  131072k
+	 *
+	 * This allows larger machines to have larger/more transfers.
+	 * Limit the default to 256M
+	 */
+	nfs_congestion_kb = (16*int_sqrt(totalram_pages())) << (PAGE_SHIFT-10);
+	if (nfs_congestion_kb > 256*1024)
+		nfs_congestion_kb = 256*1024;
+
+	return 0;
+
+out_destroy_commit_cache:
+	kmem_cache_destroy(nfs_cdata_cachep);
+out_destroy_write_mempool:
+	mempool_destroy(nfs_wdata_mempool);
+out_destroy_write_cache:
+	kmem_cache_destroy(nfs_wdata_cachep);
+	return -ENOMEM;
+}
+
+void nfs_destroy_writepagecache(void)
+{
+	mempool_destroy(nfs_commit_mempool);
+	kmem_cache_destroy(nfs_cdata_cachep);
+	mempool_destroy(nfs_wdata_mempool);
+	kmem_cache_destroy(nfs_wdata_cachep);
+}
+
+static const struct nfs_rw_ops nfs_rw_write_ops = {
+	.rw_alloc_header	= nfs_writehdr_alloc,
+	.rw_free_header		= nfs_writehdr_free,
+	.rw_done		= nfs_writeback_done,
+	.rw_result		= nfs_writeback_result,
+	.rw_initiate		= nfs_initiate_write,
+};