fs/nfs/fscache.c - third_party/kernel - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /* NFS filesystem cache interface
  *
  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  */

 #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 <linux/slab.h>
 #include <linux/iversion.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);

 /*
  * Layout of the key for an NFS server cache object.
  */
 struct nfs_server_key {
 	struct {
 		uint16_t	nfsversion;		/* NFS protocol version */
 		uint32_t	minorversion;		/* NFSv4 minor version */
 		uint16_t	family;			/* address family */
 		__be16		port;			/* IP port */
 	} hdr;
 	union {
 		struct in_addr	ipv4_addr;	/* IPv4 address */
 		struct in6_addr ipv6_addr;	/* IPv6 address */
 	};
 } __packed;

 /*
  * 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)
 {
 	const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) &clp->cl_addr;
 	const struct sockaddr_in *sin = (struct sockaddr_in *) &clp->cl_addr;
 	struct nfs_server_key key;
 	uint16_t len = sizeof(key.hdr);

 	memset(&key, 0, sizeof(key));
 	key.hdr.nfsversion = clp->rpc_ops->version;
 	key.hdr.minorversion = clp->cl_minorversion;
 	key.hdr.family = clp->cl_addr.ss_family;

 	switch (clp->cl_addr.ss_family) {
 	case AF_INET:
 		key.hdr.port = sin->sin_port;
 		key.ipv4_addr = sin->sin_addr;
 		len += sizeof(key.ipv4_addr);
 		break;

 	case AF_INET6:
 		key.hdr.port = sin6->sin6_port;
 		key.ipv6_addr = sin6->sin6_addr;
 		len += sizeof(key.ipv6_addr);
 		break;

 	default:
 		printk(KERN_WARNING "NFS: Unknown network family '%d'\n",
 		       clp->cl_addr.ss_family);
 		clp->fscache = NULL;
 		return;
 	}

 	/* create a cache index for looking up filehandles */
 	clp->fscache = fscache_acquire_cookie(nfs_fscache_netfs.primary_index,
 					      &nfs_fscache_server_index_def,
 					      &key, len,
 					      NULL, 0,
 					      clp, 0, true);
 	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, NULL, false);
 	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.
  *
  * The default uniquifier is just an empty string, but it may be overridden
  * either by the 'fsc=xxx' option to mount, or by inheriting it from the parent
  * superblock across an automount point of some nature.
  */
 void nfs_fscache_get_super_cookie(struct super_block *sb, const char *uniq, int ulen)
 {
 	struct nfs_fscache_key *key, *xkey;
 	struct nfs_server *nfss = NFS_SB(sb);
 	struct rb_node **p, *parent;
 	int diff;

 	nfss->fscache_key = NULL;
 	nfss->fscache = NULL;
 	if (!uniq) {
 		uniq = "";
 		ulen = 1;
 	}

 	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_SB_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,
 					       &key->key,
 					       sizeof(key->key) + ulen,
 					       NULL, 0,
 					       nfss, 0, true);
 	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, NULL, false);
 	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;
 	}
 }

 static void nfs_fscache_update_auxdata(struct nfs_fscache_inode_auxdata *auxdata,
 				  struct nfs_inode *nfsi)
 {
 	memset(auxdata, 0, sizeof(*auxdata));
 	auxdata->mtime_sec  = nfsi->vfs_inode.i_mtime.tv_sec;
 	auxdata->mtime_nsec = nfsi->vfs_inode.i_mtime.tv_nsec;
 	auxdata->ctime_sec  = nfsi->vfs_inode.i_ctime.tv_sec;
 	auxdata->ctime_nsec = nfsi->vfs_inode.i_ctime.tv_nsec;

 	if (NFS_SERVER(&nfsi->vfs_inode)->nfs_client->rpc_ops->version == 4)
 		auxdata->change_attr = inode_peek_iversion_raw(&nfsi->vfs_inode);
 }

 /*
  * Initialise the per-inode cache cookie pointer for an NFS inode.
  */
 void nfs_fscache_init_inode(struct inode *inode)
 {
 	struct nfs_fscache_inode_auxdata auxdata;
 	struct nfs_server *nfss = NFS_SERVER(inode);
 	struct nfs_inode *nfsi = NFS_I(inode);

 	nfsi->fscache = NULL;
 	if (!(nfss->fscache && S_ISREG(inode->i_mode)))
 		return;

 	nfs_fscache_update_auxdata(&auxdata, nfsi);

 	nfsi->fscache = fscache_acquire_cookie(NFS_SB(inode->i_sb)->fscache,
 					       &nfs_fscache_inode_object_def,
 					       nfsi->fh.data, nfsi->fh.size,
 					       &auxdata, sizeof(auxdata),
 					       nfsi, nfsi->vfs_inode.i_size, false);
 }

 /*
  * Release a per-inode cookie.
  */
 void nfs_fscache_clear_inode(struct inode *inode)
 {
 	struct nfs_fscache_inode_auxdata auxdata;
 	struct nfs_inode *nfsi = NFS_I(inode);
 	struct fscache_cookie *cookie = nfs_i_fscache(inode);

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

 	nfs_fscache_update_auxdata(&auxdata, nfsi);
 	fscache_relinquish_cookie(cookie, &auxdata, false);
 	nfsi->fscache = NULL;
 }

 static bool nfs_fscache_can_enable(void *data)
 {
 	struct inode *inode = data;

 	return !inode_is_open_for_write(inode);
 }

 /*
  * Enable or disable caching for a file that is being opened as appropriate.
  * The cookie is allocated when the inode is initialised, but is not enabled at
  * that time.  Enablement is deferred to file-open time to avoid stat() and
  * access() thrashing the cache.
  *
  * For now, with NFS, only regular files that are open read-only will be able
  * to use the cache.
  *
  * We enable the cache for an inode if we open it read-only and it isn't
  * currently open for writing.  We disable the cache if the inode is open
  * write-only.
  *
  * The caller uses the file struct to pin i_writecount on the inode before
  * calling us when a file is opened for writing, so we can make use of that.
  *
  * Note that this may be invoked multiple times in parallel by parallel
  * nfs_open() functions.
  */
 void nfs_fscache_open_file(struct inode *inode, struct file *filp)
 {
 	struct nfs_fscache_inode_auxdata auxdata;
 	struct nfs_inode *nfsi = NFS_I(inode);
 	struct fscache_cookie *cookie = nfs_i_fscache(inode);

 	if (!fscache_cookie_valid(cookie))
 		return;

 	nfs_fscache_update_auxdata(&auxdata, nfsi);

 	if (inode_is_open_for_write(inode)) {
 		dfprintk(FSCACHE, "NFS: nfsi 0x%p disabling cache\n", nfsi);
 		clear_bit(NFS_INO_FSCACHE, &nfsi->flags);
 		fscache_disable_cookie(cookie, &auxdata, true);
 		fscache_uncache_all_inode_pages(cookie, inode);
 	} else {
 		dfprintk(FSCACHE, "NFS: nfsi 0x%p enabling cache\n", nfsi);
 		fscache_enable_cookie(cookie, &auxdata, nfsi->vfs_inode.i_size,
 				      nfs_fscache_can_enable, inode);
 		if (fscache_cookie_enabled(cookie))
 			set_bit(NFS_INO_FSCACHE, &NFS_I(inode)->flags);
 	}
 }
 EXPORT_SYMBOL_GPL(nfs_fscache_open_file);

 /*
  * 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)
 {
 	if (PageFsCache(page)) {
 		struct fscache_cookie *cookie = nfs_i_fscache(page->mapping->host);

 		BUG_ON(!cookie);
 		dfprintk(FSCACHE, "NFS: fscache releasepage (0x%p/0x%p/0x%p)\n",
 			 cookie, page, NFS_I(page->mapping->host));

 		if (!fscache_maybe_release_page(cookie, page, gfp))
 			return 0;

 		nfs_inc_fscache_stats(page->mapping->host,
 				      NFSIOS_FSCACHE_PAGES_UNCACHED);
 	}

 	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 fscache_cookie *cookie = nfs_i_fscache(inode);

 	BUG_ON(!cookie);

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

 	fscache_wait_on_page_write(cookie, page);

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

 /*
  * 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, mark the page with PG_checked,
 	 * unlock the page, and let the VM reissue the readpage.
 	 */
 	if (!error)
 		SetPageUptodate(page);
 	else
 		SetPageChecked(page);
 	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_fscache(inode), page, page->index, page->flags, inode);

 	if (PageChecked(page)) {
 		ClearPageChecked(page);
 		return 1;
 	}

 	ret = fscache_read_or_alloc_page(nfs_i_fscache(inode),
 					 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_inc_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_OK);
 		return ret;

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

 	default:
 		dfprintk(FSCACHE, "NFS:    readpage_from_fscache %d\n", ret);
 		nfs_inc_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL);
 	}
 	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)
 {
 	unsigned npages = *nr_pages;
 	int ret;

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

 	ret = fscache_read_or_alloc_pages(nfs_i_fscache(inode),
 					  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;
 }

 /*
  * Store a newly fetched page in fscache
  * - PG_fscache must be set on the page
  */
 void __nfs_readpage_to_fscache(struct inode *inode, struct page *page, int sync)
 {
 	int ret;

 	dfprintk(FSCACHE,
 		 "NFS: readpage_to_fscache(fsc:%p/p:%p(i:%lx f:%lx)/%d)\n",
 		 nfs_i_fscache(inode), page, page->index, page->flags, sync);

 	ret = fscache_write_page(nfs_i_fscache(inode), page,
 				 inode->i_size, GFP_KERNEL);
 	dfprintk(FSCACHE,
 		 "NFS:     readpage_to_fscache: p:%p(i:%lu f:%lx) ret %d\n",
 		 page, page->index, page->flags, ret);

 	if (ret != 0) {
 		fscache_uncache_page(nfs_i_fscache(inode), page);
 		nfs_inc_fscache_stats(inode,
 				      NFSIOS_FSCACHE_PAGES_WRITTEN_FAIL);
 		nfs_inc_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_UNCACHED);
 	} else {
 		nfs_inc_fscache_stats(inode,
 				      NFSIOS_FSCACHE_PAGES_WRITTEN_OK);
 	}
 }
	// SPDX-License-Identifier: GPL-2.0-or-later
	/* NFS filesystem cache interface
	*
	* Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
	* Written by David Howells (dhowells@redhat.com)
	*/

	#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 <linux/slab.h>
	#include <linux/iversion.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);

	/*
	* Layout of the key for an NFS server cache object.
	*/
	struct nfs_server_key {
	struct {
	uint16_t nfsversion; /* NFS protocol version */
	uint32_t minorversion; /* NFSv4 minor version */
	uint16_t family; /* address family */
	__be16 port; /* IP port */
	} hdr;
	union {
	struct in_addr ipv4_addr; /* IPv4 address */
	struct in6_addr ipv6_addr; /* IPv6 address */
	};
	} __packed;

	/*
	* 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)
	{
	const struct sockaddr_in6 sin6 = (struct sockaddr_in6 ) &clp->cl_addr;
	const struct sockaddr_in sin = (struct sockaddr_in ) &clp->cl_addr;
	struct nfs_server_key key;
	uint16_t len = sizeof(key.hdr);

	memset(&key, 0, sizeof(key));
	key.hdr.nfsversion = clp->rpc_ops->version;
	key.hdr.minorversion = clp->cl_minorversion;
	key.hdr.family = clp->cl_addr.ss_family;

	switch (clp->cl_addr.ss_family) {
	case AF_INET:
	key.hdr.port = sin->sin_port;
	key.ipv4_addr = sin->sin_addr;
	len += sizeof(key.ipv4_addr);
	break;

	case AF_INET6:
	key.hdr.port = sin6->sin6_port;
	key.ipv6_addr = sin6->sin6_addr;
	len += sizeof(key.ipv6_addr);
	break;

	default:
	printk(KERN_WARNING "NFS: Unknown network family '%d'\n",
	clp->cl_addr.ss_family);
	clp->fscache = NULL;
	return;
	}

	/* create a cache index for looking up filehandles */
	clp->fscache = fscache_acquire_cookie(nfs_fscache_netfs.primary_index,
	&nfs_fscache_server_index_def,
	&key, len,
	NULL, 0,
	clp, 0, true);
	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, NULL, false);
	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.
	*
	* The default uniquifier is just an empty string, but it may be overridden
	* either by the 'fsc=xxx' option to mount, or by inheriting it from the parent
	* superblock across an automount point of some nature.
	*/
	void nfs_fscache_get_super_cookie(struct super_block sb, const char uniq, int ulen)
	{
	struct nfs_fscache_key key, xkey;
	struct nfs_server *nfss = NFS_SB(sb);
	struct rb_node *p, parent;
	int diff;

	nfss->fscache_key = NULL;
	nfss->fscache = NULL;
	if (!uniq) {
	uniq = "";
	ulen = 1;
	}

	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_SB_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,
	&key->key,
	sizeof(key->key) + ulen,
	NULL, 0,
	nfss, 0, true);
	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, NULL, false);
	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;
	}
	}

	static void nfs_fscache_update_auxdata(struct nfs_fscache_inode_auxdata *auxdata,
	struct nfs_inode *nfsi)
	{
	memset(auxdata, 0, sizeof(*auxdata));
	auxdata->mtime_sec = nfsi->vfs_inode.i_mtime.tv_sec;
	auxdata->mtime_nsec = nfsi->vfs_inode.i_mtime.tv_nsec;
	auxdata->ctime_sec = nfsi->vfs_inode.i_ctime.tv_sec;
	auxdata->ctime_nsec = nfsi->vfs_inode.i_ctime.tv_nsec;

	if (NFS_SERVER(&nfsi->vfs_inode)->nfs_client->rpc_ops->version == 4)
	auxdata->change_attr = inode_peek_iversion_raw(&nfsi->vfs_inode);
	}

	/*
	* Initialise the per-inode cache cookie pointer for an NFS inode.
	*/
	void nfs_fscache_init_inode(struct inode *inode)
	{
	struct nfs_fscache_inode_auxdata auxdata;
	struct nfs_server *nfss = NFS_SERVER(inode);
	struct nfs_inode *nfsi = NFS_I(inode);

	nfsi->fscache = NULL;
	if (!(nfss->fscache && S_ISREG(inode->i_mode)))
	return;

	nfs_fscache_update_auxdata(&auxdata, nfsi);

	nfsi->fscache = fscache_acquire_cookie(NFS_SB(inode->i_sb)->fscache,
	&nfs_fscache_inode_object_def,
	nfsi->fh.data, nfsi->fh.size,
	&auxdata, sizeof(auxdata),
	nfsi, nfsi->vfs_inode.i_size, false);
	}

	/*
	* Release a per-inode cookie.
	*/
	void nfs_fscache_clear_inode(struct inode *inode)
	{
	struct nfs_fscache_inode_auxdata auxdata;
	struct nfs_inode *nfsi = NFS_I(inode);
	struct fscache_cookie *cookie = nfs_i_fscache(inode);

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

	nfs_fscache_update_auxdata(&auxdata, nfsi);
	fscache_relinquish_cookie(cookie, &auxdata, false);
	nfsi->fscache = NULL;
	}

	static bool nfs_fscache_can_enable(void *data)
	{
	struct inode *inode = data;

	return !inode_is_open_for_write(inode);
	}

	/*
	* Enable or disable caching for a file that is being opened as appropriate.
	* The cookie is allocated when the inode is initialised, but is not enabled at
	* that time. Enablement is deferred to file-open time to avoid stat() and
	* access() thrashing the cache.
	*
	* For now, with NFS, only regular files that are open read-only will be able
	* to use the cache.
	*
	* We enable the cache for an inode if we open it read-only and it isn't
	* currently open for writing. We disable the cache if the inode is open
	* write-only.
	*
	* The caller uses the file struct to pin i_writecount on the inode before
	* calling us when a file is opened for writing, so we can make use of that.
	*
	* Note that this may be invoked multiple times in parallel by parallel
	* nfs_open() functions.
	*/
	void nfs_fscache_open_file(struct inode inode, struct file filp)
	{
	struct nfs_fscache_inode_auxdata auxdata;
	struct nfs_inode *nfsi = NFS_I(inode);
	struct fscache_cookie *cookie = nfs_i_fscache(inode);

	if (!fscache_cookie_valid(cookie))
	return;

	nfs_fscache_update_auxdata(&auxdata, nfsi);

	if (inode_is_open_for_write(inode)) {
	dfprintk(FSCACHE, "NFS: nfsi 0x%p disabling cache\n", nfsi);
	clear_bit(NFS_INO_FSCACHE, &nfsi->flags);
	fscache_disable_cookie(cookie, &auxdata, true);
	fscache_uncache_all_inode_pages(cookie, inode);
	} else {
	dfprintk(FSCACHE, "NFS: nfsi 0x%p enabling cache\n", nfsi);
	fscache_enable_cookie(cookie, &auxdata, nfsi->vfs_inode.i_size,
	nfs_fscache_can_enable, inode);
	if (fscache_cookie_enabled(cookie))
	set_bit(NFS_INO_FSCACHE, &NFS_I(inode)->flags);
	}
	}
	EXPORT_SYMBOL_GPL(nfs_fscache_open_file);

	/*
	* 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)
	{
	if (PageFsCache(page)) {
	struct fscache_cookie *cookie = nfs_i_fscache(page->mapping->host);

	BUG_ON(!cookie);
	dfprintk(FSCACHE, "NFS: fscache releasepage (0x%p/0x%p/0x%p)\n",
	cookie, page, NFS_I(page->mapping->host));

	if (!fscache_maybe_release_page(cookie, page, gfp))
	return 0;

	nfs_inc_fscache_stats(page->mapping->host,
	NFSIOS_FSCACHE_PAGES_UNCACHED);
	}

	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 fscache_cookie *cookie = nfs_i_fscache(inode);

	BUG_ON(!cookie);

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

	fscache_wait_on_page_write(cookie, page);

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

	/*
	* 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, mark the page with PG_checked,
	* unlock the page, and let the VM reissue the readpage.
	*/
	if (!error)
	SetPageUptodate(page);
	else
	SetPageChecked(page);
	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_fscache(inode), page, page->index, page->flags, inode);

	if (PageChecked(page)) {
	ClearPageChecked(page);
	return 1;
	}

	ret = fscache_read_or_alloc_page(nfs_i_fscache(inode),
	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_inc_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_OK);
	return ret;

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

	default:
	dfprintk(FSCACHE, "NFS: readpage_from_fscache %d\n", ret);
	nfs_inc_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL);
	}
	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)
	{
	unsigned npages = *nr_pages;
	int ret;

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

	ret = fscache_read_or_alloc_pages(nfs_i_fscache(inode),
	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;
	}

	/*
	* Store a newly fetched page in fscache
	* - PG_fscache must be set on the page
	*/
	void __nfs_readpage_to_fscache(struct inode inode, struct page page, int sync)
	{
	int ret;

	dfprintk(FSCACHE,
	"NFS: readpage_to_fscache(fsc:%p/p:%p(i:%lx f:%lx)/%d)\n",
	nfs_i_fscache(inode), page, page->index, page->flags, sync);

	ret = fscache_write_page(nfs_i_fscache(inode), page,
	inode->i_size, GFP_KERNEL);
	dfprintk(FSCACHE,
	"NFS: readpage_to_fscache: p:%p(i:%lu f:%lx) ret %d\n",
	page, page->index, page->flags, ret);

	if (ret != 0) {
	fscache_uncache_page(nfs_i_fscache(inode), page);
	nfs_inc_fscache_stats(inode,
	NFSIOS_FSCACHE_PAGES_WRITTEN_FAIL);
	nfs_inc_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_UNCACHED);
	} else {
	nfs_inc_fscache_stats(inode,
	NFSIOS_FSCACHE_PAGES_WRITTEN_OK);
	}
	}