fs/nfs/fscache.c - linux - Git at Google

 /* NFS filesystem cache interface
  *
  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public Licence
  * as published by the Free Software Foundation; either version
  * 2 of the Licence, or (at your option) any later version.
  */

 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/sched.h>
 #include <linux/mm.h>
 #include <linux/nfs_fs.h>
 #include <linux/nfs_fs_sb.h>
 #include <linux/in6.h>
 #include <linux/seq_file.h>

 #include "internal.h"
 #include "iostat.h"
 #include "fscache.h"

 #define NFSDBG_FACILITY		NFSDBG_FSCACHE

 static struct rb_root nfs_fscache_keys = RB_ROOT;
 static DEFINE_SPINLOCK(nfs_fscache_keys_lock);

 /*
  * Get the per-client index cookie for an NFS client if the appropriate mount
  * flag was set
  * - We always try and get an index cookie for the client, but get filehandle
  *   cookies on a per-superblock basis, depending on the mount flags
  */
 void nfs_fscache_get_client_cookie(struct nfs_client *clp)
 {
 	/* create a cache index for looking up filehandles */
 	clp->fscache = fscache_acquire_cookie(nfs_fscache_netfs.primary_index,
 					      &nfs_fscache_server_index_def,
 					      clp);
 	dfprintk(FSCACHE, "NFS: get client cookie (0x%p/0x%p)\n",
 		 clp, clp->fscache);
 }

 /*
  * Dispose of a per-client cookie
  */
 void nfs_fscache_release_client_cookie(struct nfs_client *clp)
 {
 	dfprintk(FSCACHE, "NFS: releasing client cookie (0x%p/0x%p)\n",
 		 clp, clp->fscache);

 	fscache_relinquish_cookie(clp->fscache, 0);
 	clp->fscache = NULL;
 }

 /*
  * Get the cache cookie for an NFS superblock.  We have to handle
  * uniquification here because the cache doesn't do it for us.
  */
 void nfs_fscache_get_super_cookie(struct super_block *sb,
 				  struct nfs_parsed_mount_data *data)
 {
 	struct nfs_fscache_key *key, *xkey;
 	struct nfs_server *nfss = NFS_SB(sb);
 	struct rb_node **p, *parent;
 	const char *uniq = data->fscache_uniq ?: "";
 	int diff, ulen;

 	ulen = strlen(uniq);
 	key = kzalloc(sizeof(*key) + ulen, GFP_KERNEL);
 	if (!key)
 		return;

 	key->nfs_client = nfss->nfs_client;
 	key->key.super.s_flags = sb->s_flags & NFS_MS_MASK;
 	key->key.nfs_server.flags = nfss->flags;
 	key->key.nfs_server.rsize = nfss->rsize;
 	key->key.nfs_server.wsize = nfss->wsize;
 	key->key.nfs_server.acregmin = nfss->acregmin;
 	key->key.nfs_server.acregmax = nfss->acregmax;
 	key->key.nfs_server.acdirmin = nfss->acdirmin;
 	key->key.nfs_server.acdirmax = nfss->acdirmax;
 	key->key.nfs_server.fsid = nfss->fsid;
 	key->key.rpc_auth.au_flavor = nfss->client->cl_auth->au_flavor;

 	key->key.uniq_len = ulen;
 	memcpy(key->key.uniquifier, uniq, ulen);

 	spin_lock(&nfs_fscache_keys_lock);
 	p = &nfs_fscache_keys.rb_node;
 	parent = NULL;
 	while (*p) {
 		parent = *p;
 		xkey = rb_entry(parent, struct nfs_fscache_key, node);

 		if (key->nfs_client < xkey->nfs_client)
 			goto go_left;
 		if (key->nfs_client > xkey->nfs_client)
 			goto go_right;

 		diff = memcmp(&key->key, &xkey->key, sizeof(key->key));
 		if (diff < 0)
 			goto go_left;
 		if (diff > 0)
 			goto go_right;

 		if (key->key.uniq_len == 0)
 			goto non_unique;
 		diff = memcmp(key->key.uniquifier,
 			      xkey->key.uniquifier,
 			      key->key.uniq_len);
 		if (diff < 0)
 			goto go_left;
 		if (diff > 0)
 			goto go_right;
 		goto non_unique;

 	go_left:
 		p = &(*p)->rb_left;
 		continue;
 	go_right:
 		p = &(*p)->rb_right;
 	}

 	rb_link_node(&key->node, parent, p);
 	rb_insert_color(&key->node, &nfs_fscache_keys);
 	spin_unlock(&nfs_fscache_keys_lock);
 	nfss->fscache_key = key;

 	/* create a cache index for looking up filehandles */
 	nfss->fscache = fscache_acquire_cookie(nfss->nfs_client->fscache,
 					       &nfs_fscache_super_index_def,
 					       nfss);
 	dfprintk(FSCACHE, "NFS: get superblock cookie (0x%p/0x%p)\n",
 		 nfss, nfss->fscache);
 	return;

 non_unique:
 	spin_unlock(&nfs_fscache_keys_lock);
 	kfree(key);
 	nfss->fscache_key = NULL;
 	nfss->fscache = NULL;
 	printk(KERN_WARNING "NFS:"
 	       " Cache request denied due to non-unique superblock keys\n");
 }

 /*
  * release a per-superblock cookie
  */
 void nfs_fscache_release_super_cookie(struct super_block *sb)
 {
 	struct nfs_server *nfss = NFS_SB(sb);

 	dfprintk(FSCACHE, "NFS: releasing superblock cookie (0x%p/0x%p)\n",
 		 nfss, nfss->fscache);

 	fscache_relinquish_cookie(nfss->fscache, 0);
 	nfss->fscache = NULL;

 	if (nfss->fscache_key) {
 		spin_lock(&nfs_fscache_keys_lock);
 		rb_erase(&nfss->fscache_key->node, &nfs_fscache_keys);
 		spin_unlock(&nfs_fscache_keys_lock);
 		kfree(nfss->fscache_key);
 		nfss->fscache_key = NULL;
 	}
 }

 /*
  * Initialise the per-inode cache cookie pointer for an NFS inode.
  */
 void nfs_fscache_init_inode_cookie(struct inode *inode)
 {
 	NFS_I(inode)->fscache = NULL;
 	if (S_ISREG(inode->i_mode))
 		set_bit(NFS_INO_FSCACHE, &NFS_I(inode)->flags);
 }

 /*
  * Get the per-inode cache cookie for an NFS inode.
  */
 static void nfs_fscache_enable_inode_cookie(struct inode *inode)
 {
 	struct super_block *sb = inode->i_sb;
 	struct nfs_inode *nfsi = NFS_I(inode);

 	if (nfsi->fscache || !NFS_FSCACHE(inode))
 		return;

 	if ((NFS_SB(sb)->options & NFS_OPTION_FSCACHE)) {
 		nfsi->fscache = fscache_acquire_cookie(
 			NFS_SB(sb)->fscache,
 			&nfs_fscache_inode_object_def,
 			nfsi);

 		dfprintk(FSCACHE, "NFS: get FH cookie (0x%p/0x%p/0x%p)\n",
 			 sb, nfsi, nfsi->fscache);
 	}
 }

 /*
  * Release a per-inode cookie.
  */
 void nfs_fscache_release_inode_cookie(struct inode *inode)
 {
 	struct nfs_inode *nfsi = NFS_I(inode);

 	dfprintk(FSCACHE, "NFS: clear cookie (0x%p/0x%p)\n",
 		 nfsi, nfsi->fscache);

 	fscache_relinquish_cookie(nfsi->fscache, 0);
 	nfsi->fscache = NULL;
 }

 /*
  * Retire a per-inode cookie, destroying the data attached to it.
  */
 void nfs_fscache_zap_inode_cookie(struct inode *inode)
 {
 	struct nfs_inode *nfsi = NFS_I(inode);

 	dfprintk(FSCACHE, "NFS: zapping cookie (0x%p/0x%p)\n",
 		 nfsi, nfsi->fscache);

 	fscache_relinquish_cookie(nfsi->fscache, 1);
 	nfsi->fscache = NULL;
 }

 /*
  * Turn off the cache with regard to a per-inode cookie if opened for writing,
  * invalidating all the pages in the page cache relating to the associated
  * inode to clear the per-page caching.
  */
 static void nfs_fscache_disable_inode_cookie(struct inode *inode)
 {
 	clear_bit(NFS_INO_FSCACHE, &NFS_I(inode)->flags);

 	if (NFS_I(inode)->fscache) {
 		dfprintk(FSCACHE,
 			 "NFS: nfsi 0x%p turning cache off\n", NFS_I(inode));

 		/* Need to invalidate any mapped pages that were read in before
 		 * turning off the cache.
 		 */
 		if (inode->i_mapping && inode->i_mapping->nrpages)
 			invalidate_inode_pages2(inode->i_mapping);

 		nfs_fscache_zap_inode_cookie(inode);
 	}
 }

 /*
  * wait_on_bit() sleep function for uninterruptible waiting
  */
 static int nfs_fscache_wait_bit(void *flags)
 {
 	schedule();
 	return 0;
 }

 /*
  * Lock against someone else trying to also acquire or relinquish a cookie
  */
 static inline void nfs_fscache_inode_lock(struct inode *inode)
 {
 	struct nfs_inode *nfsi = NFS_I(inode);

 	while (test_and_set_bit(NFS_INO_FSCACHE_LOCK, &nfsi->flags))
 		wait_on_bit(&nfsi->flags, NFS_INO_FSCACHE_LOCK,
 			    nfs_fscache_wait_bit, TASK_UNINTERRUPTIBLE);
 }

 /*
  * Unlock cookie management lock
  */
 static inline void nfs_fscache_inode_unlock(struct inode *inode)
 {
 	struct nfs_inode *nfsi = NFS_I(inode);

 	smp_mb__before_clear_bit();
 	clear_bit(NFS_INO_FSCACHE_LOCK, &nfsi->flags);
 	smp_mb__after_clear_bit();
 	wake_up_bit(&nfsi->flags, NFS_INO_FSCACHE_LOCK);
 }

 /*
  * Decide if we should enable or disable local caching for this inode.
  * - For now, with NFS, only regular files that are open read-only will be able
  *   to use the cache.
  * - May be invoked multiple times in parallel by parallel nfs_open() functions.
  */
 void nfs_fscache_set_inode_cookie(struct inode *inode, struct file *filp)
 {
 	if (NFS_FSCACHE(inode)) {
 		nfs_fscache_inode_lock(inode);
 		if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
 			nfs_fscache_disable_inode_cookie(inode);
 		else
 			nfs_fscache_enable_inode_cookie(inode);
 		nfs_fscache_inode_unlock(inode);
 	}
 }

 /*
  * Replace a per-inode cookie due to revalidation detecting a file having
  * changed on the server.
  */
 void nfs_fscache_reset_inode_cookie(struct inode *inode)
 {
 	struct nfs_inode *nfsi = NFS_I(inode);
 	struct nfs_server *nfss = NFS_SERVER(inode);
 	struct fscache_cookie *old = nfsi->fscache;

 	nfs_fscache_inode_lock(inode);
 	if (nfsi->fscache) {
 		/* retire the current fscache cache and get a new one */
 		fscache_relinquish_cookie(nfsi->fscache, 1);

 		nfsi->fscache = fscache_acquire_cookie(
 			nfss->nfs_client->fscache,
 			&nfs_fscache_inode_object_def,
 			nfsi);

 		dfprintk(FSCACHE,
 			 "NFS: revalidation new cookie (0x%p/0x%p/0x%p/0x%p)\n",
 			 nfss, nfsi, old, nfsi->fscache);
 	}
 	nfs_fscache_inode_unlock(inode);
 }

 /*
  * Release the caching state associated with a page, if the page isn't busy
  * interacting with the cache.
  * - Returns true (can release page) or false (page busy).
  */
 int nfs_fscache_release_page(struct page *page, gfp_t gfp)
 {
 	struct nfs_inode *nfsi = NFS_I(page->mapping->host);
 	struct fscache_cookie *cookie = nfsi->fscache;

 	BUG_ON(!cookie);

 	if (fscache_check_page_write(cookie, page)) {
 		if (!(gfp & __GFP_WAIT))
 			return 0;
 		fscache_wait_on_page_write(cookie, page);
 	}

 	if (PageFsCache(page)) {
 		dfprintk(FSCACHE, "NFS: fscache releasepage (0x%p/0x%p/0x%p)\n",
 			 cookie, page, nfsi);

 		fscache_uncache_page(cookie, page);
 		nfs_add_fscache_stats(page->mapping->host,
 				      NFSIOS_FSCACHE_PAGES_UNCACHED, 1);
 	}

 	return 1;
 }

 /*
  * Release the caching state associated with a page if undergoing complete page
  * invalidation.
  */
 void __nfs_fscache_invalidate_page(struct page *page, struct inode *inode)
 {
 	struct nfs_inode *nfsi = NFS_I(inode);
 	struct fscache_cookie *cookie = nfsi->fscache;

 	BUG_ON(!cookie);

 	dfprintk(FSCACHE, "NFS: fscache invalidatepage (0x%p/0x%p/0x%p)\n",
 		 cookie, page, nfsi);

 	fscache_wait_on_page_write(cookie, page);

 	BUG_ON(!PageLocked(page));
 	fscache_uncache_page(cookie, page);
 	nfs_add_fscache_stats(page->mapping->host,
 			      NFSIOS_FSCACHE_PAGES_UNCACHED, 1);
 }

 /*
  * Handle completion of a page being read from the cache.
  * - Called in process (keventd) context.
  */
 static void nfs_readpage_from_fscache_complete(struct page *page,
 					       void *context,
 					       int error)
 {
 	dfprintk(FSCACHE,
 		 "NFS: readpage_from_fscache_complete (0x%p/0x%p/%d)\n",
 		 page, context, error);

 	/* if the read completes with an error, we just unlock the page and let
 	 * the VM reissue the readpage */
 	if (!error) {
 		SetPageUptodate(page);
 		unlock_page(page);
 	} else {
 		error = nfs_readpage_async(context, page->mapping->host, page);
 		if (error)
 			unlock_page(page);
 	}
 }

 /*
  * Retrieve a page from fscache
  */
 int __nfs_readpage_from_fscache(struct nfs_open_context *ctx,
 				struct inode *inode, struct page *page)
 {
 	int ret;

 	dfprintk(FSCACHE,
 		 "NFS: readpage_from_fscache(fsc:%p/p:%p(i:%lx f:%lx)/0x%p)\n",
 		 NFS_I(inode)->fscache, page, page->index, page->flags, inode);

 	ret = fscache_read_or_alloc_page(NFS_I(inode)->fscache,
 					 page,
 					 nfs_readpage_from_fscache_complete,
 					 ctx,
 					 GFP_KERNEL);

 	switch (ret) {
 	case 0: /* read BIO submitted (page in fscache) */
 		dfprintk(FSCACHE,
 			 "NFS:    readpage_from_fscache: BIO submitted\n");
 		nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_OK, 1);
 		return ret;

 	case -ENOBUFS: /* inode not in cache */
 	case -ENODATA: /* page not in cache */
 		nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL, 1);
 		dfprintk(FSCACHE,
 			 "NFS:    readpage_from_fscache %d\n", ret);
 		return 1;

 	default:
 		dfprintk(FSCACHE, "NFS:    readpage_from_fscache %d\n", ret);
 		nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL, 1);
 	}
 	return ret;
 }

 /*
  * Retrieve a set of pages from fscache
  */
 int __nfs_readpages_from_fscache(struct nfs_open_context *ctx,
 				 struct inode *inode,
 				 struct address_space *mapping,
 				 struct list_head *pages,
 				 unsigned *nr_pages)
 {
 	int ret, npages = *nr_pages;

 	dfprintk(FSCACHE, "NFS: nfs_getpages_from_fscache (0x%p/%u/0x%p)\n",
 		 NFS_I(inode)->fscache, npages, inode);

 	ret = fscache_read_or_alloc_pages(NFS_I(inode)->fscache,
 					  mapping, pages, nr_pages,
 					  nfs_readpage_from_fscache_complete,
 					  ctx,
 					  mapping_gfp_mask(mapping));
 	if (*nr_pages < npages)
 		nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_OK,
 				      npages);
 	if (*nr_pages > 0)
 		nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL,
 				      *nr_pages);

 	switch (ret) {
 	case 0: /* read submitted to the cache for all pages */
 		BUG_ON(!list_empty(pages));
 		BUG_ON(*nr_pages != 0);
 		dfprintk(FSCACHE,
 			 "NFS: nfs_getpages_from_fscache: submitted\n");

 		return ret;

 	case -ENOBUFS: /* some pages aren't cached and can't be */
 	case -ENODATA: /* some pages aren't cached */
 		dfprintk(FSCACHE,
 			 "NFS: nfs_getpages_from_fscache: no page: %d\n", ret);
 		return 1;

 	default:
 		dfprintk(FSCACHE,
 			 "NFS: nfs_getpages_from_fscache: ret  %d\n", ret);
 	}

 	return ret;
 }
	/* NFS filesystem cache interface
	*
	* Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
	* Written by David Howells (dhowells@redhat.com)
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public Licence
	* as published by the Free Software Foundation; either version
	* 2 of the Licence, or (at your option) any later version.
	*/

	#include <linux/init.h>
	#include <linux/kernel.h>
	#include <linux/sched.h>
	#include <linux/mm.h>
	#include <linux/nfs_fs.h>
	#include <linux/nfs_fs_sb.h>
	#include <linux/in6.h>
	#include <linux/seq_file.h>

	#include "internal.h"
	#include "iostat.h"
	#include "fscache.h"

	#define NFSDBG_FACILITY NFSDBG_FSCACHE

	static struct rb_root nfs_fscache_keys = RB_ROOT;
	static DEFINE_SPINLOCK(nfs_fscache_keys_lock);

	/*
	* Get the per-client index cookie for an NFS client if the appropriate mount
	* flag was set
	* - We always try and get an index cookie for the client, but get filehandle
	* cookies on a per-superblock basis, depending on the mount flags
	*/
	void nfs_fscache_get_client_cookie(struct nfs_client *clp)
	{
	/* create a cache index for looking up filehandles */
	clp->fscache = fscache_acquire_cookie(nfs_fscache_netfs.primary_index,
	&nfs_fscache_server_index_def,
	clp);
	dfprintk(FSCACHE, "NFS: get client cookie (0x%p/0x%p)\n",
	clp, clp->fscache);
	}

	/*
	* Dispose of a per-client cookie
	*/
	void nfs_fscache_release_client_cookie(struct nfs_client *clp)
	{
	dfprintk(FSCACHE, "NFS: releasing client cookie (0x%p/0x%p)\n",
	clp, clp->fscache);

	fscache_relinquish_cookie(clp->fscache, 0);
	clp->fscache = NULL;
	}

	/*
	* Get the cache cookie for an NFS superblock. We have to handle
	* uniquification here because the cache doesn't do it for us.
	*/
	void nfs_fscache_get_super_cookie(struct super_block *sb,
	struct nfs_parsed_mount_data *data)
	{
	struct nfs_fscache_key key, xkey;
	struct nfs_server *nfss = NFS_SB(sb);
	struct rb_node *p, parent;
	const char *uniq = data->fscache_uniq ?: "";
	int diff, ulen;

	ulen = strlen(uniq);
	key = kzalloc(sizeof(*key) + ulen, GFP_KERNEL);
	if (!key)
	return;

	key->nfs_client = nfss->nfs_client;
	key->key.super.s_flags = sb->s_flags & NFS_MS_MASK;
	key->key.nfs_server.flags = nfss->flags;
	key->key.nfs_server.rsize = nfss->rsize;
	key->key.nfs_server.wsize = nfss->wsize;
	key->key.nfs_server.acregmin = nfss->acregmin;
	key->key.nfs_server.acregmax = nfss->acregmax;
	key->key.nfs_server.acdirmin = nfss->acdirmin;
	key->key.nfs_server.acdirmax = nfss->acdirmax;
	key->key.nfs_server.fsid = nfss->fsid;
	key->key.rpc_auth.au_flavor = nfss->client->cl_auth->au_flavor;

	key->key.uniq_len = ulen;
	memcpy(key->key.uniquifier, uniq, ulen);

	spin_lock(&nfs_fscache_keys_lock);
	p = &nfs_fscache_keys.rb_node;
	parent = NULL;
	while (*p) {
	parent = *p;
	xkey = rb_entry(parent, struct nfs_fscache_key, node);

	if (key->nfs_client < xkey->nfs_client)
	goto go_left;
	if (key->nfs_client > xkey->nfs_client)
	goto go_right;

	diff = memcmp(&key->key, &xkey->key, sizeof(key->key));
	if (diff < 0)
	goto go_left;
	if (diff > 0)
	goto go_right;

	if (key->key.uniq_len == 0)
	goto non_unique;
	diff = memcmp(key->key.uniquifier,
	xkey->key.uniquifier,
	key->key.uniq_len);
	if (diff < 0)
	goto go_left;
	if (diff > 0)
	goto go_right;
	goto non_unique;

	go_left:
	p = &(*p)->rb_left;
	continue;
	go_right:
	p = &(*p)->rb_right;
	}

	rb_link_node(&key->node, parent, p);
	rb_insert_color(&key->node, &nfs_fscache_keys);
	spin_unlock(&nfs_fscache_keys_lock);
	nfss->fscache_key = key;

	/* create a cache index for looking up filehandles */
	nfss->fscache = fscache_acquire_cookie(nfss->nfs_client->fscache,
	&nfs_fscache_super_index_def,
	nfss);
	dfprintk(FSCACHE, "NFS: get superblock cookie (0x%p/0x%p)\n",
	nfss, nfss->fscache);
	return;

	non_unique:
	spin_unlock(&nfs_fscache_keys_lock);
	kfree(key);
	nfss->fscache_key = NULL;
	nfss->fscache = NULL;
	printk(KERN_WARNING "NFS:"
	" Cache request denied due to non-unique superblock keys\n");
	}

	/*
	* release a per-superblock cookie
	*/
	void nfs_fscache_release_super_cookie(struct super_block *sb)
	{
	struct nfs_server *nfss = NFS_SB(sb);

	dfprintk(FSCACHE, "NFS: releasing superblock cookie (0x%p/0x%p)\n",
	nfss, nfss->fscache);

	fscache_relinquish_cookie(nfss->fscache, 0);
	nfss->fscache = NULL;

	if (nfss->fscache_key) {
	spin_lock(&nfs_fscache_keys_lock);
	rb_erase(&nfss->fscache_key->node, &nfs_fscache_keys);
	spin_unlock(&nfs_fscache_keys_lock);
	kfree(nfss->fscache_key);
	nfss->fscache_key = NULL;
	}
	}

	/*
	* Initialise the per-inode cache cookie pointer for an NFS inode.
	*/
	void nfs_fscache_init_inode_cookie(struct inode *inode)
	{
	NFS_I(inode)->fscache = NULL;
	if (S_ISREG(inode->i_mode))
	set_bit(NFS_INO_FSCACHE, &NFS_I(inode)->flags);
	}

	/*
	* Get the per-inode cache cookie for an NFS inode.
	*/
	static void nfs_fscache_enable_inode_cookie(struct inode *inode)
	{
	struct super_block *sb = inode->i_sb;
	struct nfs_inode *nfsi = NFS_I(inode);

	if (nfsi->fscache \|\| !NFS_FSCACHE(inode))
	return;

	if ((NFS_SB(sb)->options & NFS_OPTION_FSCACHE)) {
	nfsi->fscache = fscache_acquire_cookie(
	NFS_SB(sb)->fscache,
	&nfs_fscache_inode_object_def,
	nfsi);

	dfprintk(FSCACHE, "NFS: get FH cookie (0x%p/0x%p/0x%p)\n",
	sb, nfsi, nfsi->fscache);
	}
	}

	/*
	* Release a per-inode cookie.
	*/
	void nfs_fscache_release_inode_cookie(struct inode *inode)
	{
	struct nfs_inode *nfsi = NFS_I(inode);

	dfprintk(FSCACHE, "NFS: clear cookie (0x%p/0x%p)\n",
	nfsi, nfsi->fscache);

	fscache_relinquish_cookie(nfsi->fscache, 0);
	nfsi->fscache = NULL;
	}

	/*
	* Retire a per-inode cookie, destroying the data attached to it.
	*/
	void nfs_fscache_zap_inode_cookie(struct inode *inode)
	{
	struct nfs_inode *nfsi = NFS_I(inode);

	dfprintk(FSCACHE, "NFS: zapping cookie (0x%p/0x%p)\n",
	nfsi, nfsi->fscache);

	fscache_relinquish_cookie(nfsi->fscache, 1);
	nfsi->fscache = NULL;
	}

	/*
	* Turn off the cache with regard to a per-inode cookie if opened for writing,
	* invalidating all the pages in the page cache relating to the associated
	* inode to clear the per-page caching.
	*/
	static void nfs_fscache_disable_inode_cookie(struct inode *inode)
	{
	clear_bit(NFS_INO_FSCACHE, &NFS_I(inode)->flags);

	if (NFS_I(inode)->fscache) {
	dfprintk(FSCACHE,
	"NFS: nfsi 0x%p turning cache off\n", NFS_I(inode));

	/* Need to invalidate any mapped pages that were read in before
	* turning off the cache.
	*/
	if (inode->i_mapping && inode->i_mapping->nrpages)
	invalidate_inode_pages2(inode->i_mapping);

	nfs_fscache_zap_inode_cookie(inode);
	}
	}

	/*
	* wait_on_bit() sleep function for uninterruptible waiting
	*/
	static int nfs_fscache_wait_bit(void *flags)
	{
	schedule();
	return 0;
	}

	/*
	* Lock against someone else trying to also acquire or relinquish a cookie
	*/
	static inline void nfs_fscache_inode_lock(struct inode *inode)
	{
	struct nfs_inode *nfsi = NFS_I(inode);

	while (test_and_set_bit(NFS_INO_FSCACHE_LOCK, &nfsi->flags))
	wait_on_bit(&nfsi->flags, NFS_INO_FSCACHE_LOCK,
	nfs_fscache_wait_bit, TASK_UNINTERRUPTIBLE);
	}

	/*
	* Unlock cookie management lock
	*/
	static inline void nfs_fscache_inode_unlock(struct inode *inode)
	{
	struct nfs_inode *nfsi = NFS_I(inode);

	smp_mb__before_clear_bit();
	clear_bit(NFS_INO_FSCACHE_LOCK, &nfsi->flags);
	smp_mb__after_clear_bit();
	wake_up_bit(&nfsi->flags, NFS_INO_FSCACHE_LOCK);
	}

	/*
	* Decide if we should enable or disable local caching for this inode.
	* - For now, with NFS, only regular files that are open read-only will be able
	* to use the cache.
	* - May be invoked multiple times in parallel by parallel nfs_open() functions.
	*/
	void nfs_fscache_set_inode_cookie(struct inode inode, struct file filp)
	{
	if (NFS_FSCACHE(inode)) {
	nfs_fscache_inode_lock(inode);
	if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
	nfs_fscache_disable_inode_cookie(inode);
	else
	nfs_fscache_enable_inode_cookie(inode);
	nfs_fscache_inode_unlock(inode);
	}
	}

	/*
	* Replace a per-inode cookie due to revalidation detecting a file having
	* changed on the server.
	*/
	void nfs_fscache_reset_inode_cookie(struct inode *inode)
	{
	struct nfs_inode *nfsi = NFS_I(inode);
	struct nfs_server *nfss = NFS_SERVER(inode);
	struct fscache_cookie *old = nfsi->fscache;

	nfs_fscache_inode_lock(inode);
	if (nfsi->fscache) {
	/* retire the current fscache cache and get a new one */
	fscache_relinquish_cookie(nfsi->fscache, 1);

	nfsi->fscache = fscache_acquire_cookie(
	nfss->nfs_client->fscache,
	&nfs_fscache_inode_object_def,
	nfsi);

	dfprintk(FSCACHE,
	"NFS: revalidation new cookie (0x%p/0x%p/0x%p/0x%p)\n",
	nfss, nfsi, old, nfsi->fscache);
	}
	nfs_fscache_inode_unlock(inode);
	}

	/*
	* Release the caching state associated with a page, if the page isn't busy
	* interacting with the cache.
	* - Returns true (can release page) or false (page busy).
	*/
	int nfs_fscache_release_page(struct page *page, gfp_t gfp)
	{
	struct nfs_inode *nfsi = NFS_I(page->mapping->host);
	struct fscache_cookie *cookie = nfsi->fscache;

	BUG_ON(!cookie);

	if (fscache_check_page_write(cookie, page)) {
	if (!(gfp & __GFP_WAIT))
	return 0;
	fscache_wait_on_page_write(cookie, page);
	}

	if (PageFsCache(page)) {
	dfprintk(FSCACHE, "NFS: fscache releasepage (0x%p/0x%p/0x%p)\n",
	cookie, page, nfsi);

	fscache_uncache_page(cookie, page);
	nfs_add_fscache_stats(page->mapping->host,
	NFSIOS_FSCACHE_PAGES_UNCACHED, 1);
	}

	return 1;
	}

	/*
	* Release the caching state associated with a page if undergoing complete page
	* invalidation.
	*/
	void __nfs_fscache_invalidate_page(struct page page, struct inode inode)
	{
	struct nfs_inode *nfsi = NFS_I(inode);
	struct fscache_cookie *cookie = nfsi->fscache;

	BUG_ON(!cookie);

	dfprintk(FSCACHE, "NFS: fscache invalidatepage (0x%p/0x%p/0x%p)\n",
	cookie, page, nfsi);

	fscache_wait_on_page_write(cookie, page);

	BUG_ON(!PageLocked(page));
	fscache_uncache_page(cookie, page);
	nfs_add_fscache_stats(page->mapping->host,
	NFSIOS_FSCACHE_PAGES_UNCACHED, 1);
	}

	/*
	* Handle completion of a page being read from the cache.
	* - Called in process (keventd) context.
	*/
	static void nfs_readpage_from_fscache_complete(struct page *page,
	void *context,
	int error)
	{
	dfprintk(FSCACHE,
	"NFS: readpage_from_fscache_complete (0x%p/0x%p/%d)\n",
	page, context, error);

	/* if the read completes with an error, we just unlock the page and let
	* the VM reissue the readpage */
	if (!error) {
	SetPageUptodate(page);
	unlock_page(page);
	} else {
	error = nfs_readpage_async(context, page->mapping->host, page);
	if (error)
	unlock_page(page);
	}
	}

	/*
	* Retrieve a page from fscache
	*/
	int __nfs_readpage_from_fscache(struct nfs_open_context *ctx,
	struct inode inode, struct page page)
	{
	int ret;

	dfprintk(FSCACHE,
	"NFS: readpage_from_fscache(fsc:%p/p:%p(i:%lx f:%lx)/0x%p)\n",
	NFS_I(inode)->fscache, page, page->index, page->flags, inode);

	ret = fscache_read_or_alloc_page(NFS_I(inode)->fscache,
	page,
	nfs_readpage_from_fscache_complete,
	ctx,
	GFP_KERNEL);

	switch (ret) {
	case 0: /* read BIO submitted (page in fscache) */
	dfprintk(FSCACHE,
	"NFS: readpage_from_fscache: BIO submitted\n");
	nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_OK, 1);
	return ret;

	case -ENOBUFS: /* inode not in cache */
	case -ENODATA: /* page not in cache */
	nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL, 1);
	dfprintk(FSCACHE,
	"NFS: readpage_from_fscache %d\n", ret);
	return 1;

	default:
	dfprintk(FSCACHE, "NFS: readpage_from_fscache %d\n", ret);
	nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL, 1);
	}
	return ret;
	}

	/*
	* Retrieve a set of pages from fscache
	*/
	int __nfs_readpages_from_fscache(struct nfs_open_context *ctx,
	struct inode *inode,
	struct address_space *mapping,
	struct list_head *pages,
	unsigned *nr_pages)
	{
	int ret, npages = *nr_pages;

	dfprintk(FSCACHE, "NFS: nfs_getpages_from_fscache (0x%p/%u/0x%p)\n",
	NFS_I(inode)->fscache, npages, inode);

	ret = fscache_read_or_alloc_pages(NFS_I(inode)->fscache,
	mapping, pages, nr_pages,
	nfs_readpage_from_fscache_complete,
	ctx,
	mapping_gfp_mask(mapping));
	if (*nr_pages < npages)
	nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_OK,
	npages);
	if (*nr_pages > 0)
	nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL,
	*nr_pages);

	switch (ret) {
	case 0: /* read submitted to the cache for all pages */
	BUG_ON(!list_empty(pages));
	BUG_ON(*nr_pages != 0);
	dfprintk(FSCACHE,
	"NFS: nfs_getpages_from_fscache: submitted\n");

	return ret;

	case -ENOBUFS: /* some pages aren't cached and can't be */
	case -ENODATA: /* some pages aren't cached */
	dfprintk(FSCACHE,
	"NFS: nfs_getpages_from_fscache: no page: %d\n", ret);
	return 1;

	default:
	dfprintk(FSCACHE,
	"NFS: nfs_getpages_from_fscache: ret %d\n", ret);
	}

	return ret;
	}