[linux.git] / fs / nfs / pagelist.c

/*
 * linux/fs/nfs/pagelist.c
 *
 * A set of helper functions for managing NFS read and write requests.
 * The main purpose of these routines is to provide support for the
 * coalescing of several requests into a single RPC call.
 *
 * Copyright 2000, 2001 (c) Trond Myklebust <[email protected]>
 *
 */

#include <linux/config.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/sunrpc/clnt.h>
#include <linux/nfs3.h>
#include <linux/nfs4.h>
#include <linux/nfs_page.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_mount.h>

#define NFS_PARANOIA 1

static kmem_cache_t *nfs_page_cachep;

static inline struct nfs_page *
nfs_page_alloc(void)
{
	struct nfs_page	*p;
	p = kmem_cache_alloc(nfs_page_cachep, SLAB_KERNEL);
	if (p) {
		memset(p, 0, sizeof(*p));
		INIT_LIST_HEAD(&p->wb_list);
	}
	return p;
}

static inline void
nfs_page_free(struct nfs_page *p)
{
	kmem_cache_free(nfs_page_cachep, p);
}

/**
 * nfs_create_request - Create an NFS read/write request.
 * @file: file descriptor to use
 * @inode: inode to which the request is attached
 * @page: page to write
 * @offset: starting offset within the page for the write
 * @count: number of bytes to read/write
 *
 * The page must be locked by the caller. This makes sure we never
 * create two different requests for the same page, and avoids
 * a possible deadlock when we reach the hard limit on the number
 * of dirty pages.
 * User should ensure it is safe to sleep in this function.
 */
struct nfs_page *
nfs_create_request(struct nfs_open_context *ctx, struct inode *inode,
		   struct page *page,
		   unsigned int offset, unsigned int count)
{
	struct nfs_server *server = NFS_SERVER(inode);
	struct nfs_page		*req;

	/* Deal with hard limits.  */
	for (;;) {
		/* try to allocate the request struct */
		req = nfs_page_alloc();
		if (req != NULL)
			break;

		/* Try to free up at least one request in order to stay
		 * below the hard limit
		 */
		if (signalled() && (server->flags & NFS_MOUNT_INTR))
			return ERR_PTR(-ERESTARTSYS);
		yield();
	}

	/* Initialize the request struct. Initially, we assume a
	 * long write-back delay. This will be adjusted in
	 * update_nfs_request below if the region is not locked. */
	req->wb_page    = page;
	atomic_set(&req->wb_complete, 0);
	req->wb_index	= page->index;
	page_cache_get(page);
	BUG_ON(PagePrivate(page));
	BUG_ON(!PageLocked(page));
	BUG_ON(page->mapping->host != inode);
	req->wb_offset  = offset;
	req->wb_pgbase	= offset;
	req->wb_bytes   = count;
	atomic_set(&req->wb_count, 1);
	req->wb_context = get_nfs_open_context(ctx);

	return req;
}

/**
 * nfs_unlock_request - Unlock request and wake up sleepers.
 * @req:
 */
void nfs_unlock_request(struct nfs_page *req)
{
	if (!NFS_WBACK_BUSY(req)) {
		printk(KERN_ERR "NFS: Invalid unlock attempted\n");
		BUG();
	}
	smp_mb__before_clear_bit();
	clear_bit(PG_BUSY, &req->wb_flags);
	smp_mb__after_clear_bit();
	wake_up_bit(&req->wb_flags, PG_BUSY);
	nfs_release_request(req);
}

/**
 * nfs_set_page_writeback_locked - Lock a request for writeback
 * @req:
 */
int nfs_set_page_writeback_locked(struct nfs_page *req)
{
	struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);

	if (!nfs_lock_request(req))
		return 0;
	radix_tree_tag_set(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
	return 1;
}

/**
 * nfs_clear_page_writeback - Unlock request and wake up sleepers
 */
void nfs_clear_page_writeback(struct nfs_page *req)
{
	struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);

	if (req->wb_page != NULL) {
		spin_lock(&nfsi->req_lock);
		radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
		spin_unlock(&nfsi->req_lock);
	}
	nfs_unlock_request(req);
}

/**
 * nfs_clear_request - Free up all resources allocated to the request
 * @req:
 *
 * Release page resources associated with a write request after it
 * has completed.
 */
void nfs_clear_request(struct nfs_page *req)
{
	struct page *page = req->wb_page;
	if (page != NULL) {
		page_cache_release(page);
		req->wb_page = NULL;
	}
}


/**
 * nfs_release_request - Release the count on an NFS read/write request
 * @req: request to release
 *
 * Note: Should never be called with the spinlock held!
 */
void
nfs_release_request(struct nfs_page *req)
{
	if (!atomic_dec_and_test(&req->wb_count))
		return;

#ifdef NFS_PARANOIA
	BUG_ON (!list_empty(&req->wb_list));
	BUG_ON (NFS_WBACK_BUSY(req));
#endif

	/* Release struct file or cached credential */
	nfs_clear_request(req);
	put_nfs_open_context(req->wb_context);
	nfs_page_free(req);
}

static int nfs_wait_bit_interruptible(void *word)
{
	int ret = 0;

	if (signal_pending(current))
		ret = -ERESTARTSYS;
	else
		schedule();
	return ret;
}

/**
 * nfs_wait_on_request - Wait for a request to complete.
 * @req: request to wait upon.
 *
 * Interruptible by signals only if mounted with intr flag.
 * The user is responsible for holding a count on the request.
 */
int
nfs_wait_on_request(struct nfs_page *req)
{
        struct rpc_clnt	*clnt = NFS_CLIENT(req->wb_context->dentry->d_inode);
	sigset_t oldmask;
	int ret = 0;

	if (!test_bit(PG_BUSY, &req->wb_flags))
		goto out;
	/*
	 * Note: the call to rpc_clnt_sigmask() suffices to ensure that we
	 *	 are not interrupted if intr flag is not set
	 */
	rpc_clnt_sigmask(clnt, &oldmask);
	ret = out_of_line_wait_on_bit(&req->wb_flags, PG_BUSY,
			nfs_wait_bit_interruptible, TASK_INTERRUPTIBLE);
	rpc_clnt_sigunmask(clnt, &oldmask);
out:
	return ret;
}

/**
 * nfs_coalesce_requests - Split coalesced requests out from a list.
 * @head: source list
 * @dst: destination list
 * @nmax: maximum number of requests to coalesce
 *
 * Moves a maximum of 'nmax' elements from one list to another.
 * The elements are checked to ensure that they form a contiguous set
 * of pages, and that the RPC credentials are the same.
 */
int
nfs_coalesce_requests(struct list_head *head, struct list_head *dst,
		      unsigned int nmax)
{
	struct nfs_page		*req = NULL;
	unsigned int		npages = 0;

	while (!list_empty(head)) {
		struct nfs_page	*prev = req;

		req = nfs_list_entry(head->next);
		if (prev) {
			if (req->wb_context->cred != prev->wb_context->cred)
				break;
			if (req->wb_context->lockowner != prev->wb_context->lockowner)
				break;
			if (req->wb_context->state != prev->wb_context->state)
				break;
			if (req->wb_index != (prev->wb_index + 1))
				break;

			if (req->wb_pgbase != 0)
				break;
		}
		nfs_list_remove_request(req);
		nfs_list_add_request(req, dst);
		npages++;
		if (req->wb_pgbase + req->wb_bytes != PAGE_CACHE_SIZE)
			break;
		if (npages >= nmax)
			break;
	}
	return npages;
}

#define NFS_SCAN_MAXENTRIES 16
/**
 * nfs_scan_lock_dirty - Scan the radix tree for dirty requests
 * @nfsi: NFS inode
 * @dst: Destination list
 * @idx_start: lower bound of page->index to scan
 * @npages: idx_start + npages sets the upper bound to scan.
 *
 * Moves elements from one of the inode request lists.
 * If the number of requests is set to 0, the entire address_space
 * starting at index idx_start, is scanned.
 * The requests are *not* checked to ensure that they form a contiguous set.
 * You must be holding the inode's req_lock when calling this function
 */
int
nfs_scan_lock_dirty(struct nfs_inode *nfsi, struct list_head *dst,
	      unsigned long idx_start, unsigned int npages)
{
	struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
	struct nfs_page *req;
	unsigned long idx_end;
	int found, i;
	int res;

	res = 0;
	if (npages == 0)
		idx_end = ~0;
	else
		idx_end = idx_start + npages - 1;

	for (;;) {
		found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree,
				(void **)&pgvec[0], idx_start, NFS_SCAN_MAXENTRIES,
				NFS_PAGE_TAG_DIRTY);
		if (found <= 0)
			break;
		for (i = 0; i < found; i++) {
			req = pgvec[i];
			if (req->wb_index > idx_end)
				goto out;

			idx_start = req->wb_index + 1;

			if (nfs_set_page_writeback_locked(req)) {
				radix_tree_tag_clear(&nfsi->nfs_page_tree,
						req->wb_index, NFS_PAGE_TAG_DIRTY);
				nfs_list_remove_request(req);
				nfs_list_add_request(req, dst);
				res++;
			}
		}
	}
out:
	return res;
}

/**
 * nfs_scan_list - Scan a list for matching requests
 * @head: One of the NFS inode request lists
 * @dst: Destination list
 * @idx_start: lower bound of page->index to scan
 * @npages: idx_start + npages sets the upper bound to scan.
 *
 * Moves elements from one of the inode request lists.
 * If the number of requests is set to 0, the entire address_space
 * starting at index idx_start, is scanned.
 * The requests are *not* checked to ensure that they form a contiguous set.
 * You must be holding the inode's req_lock when calling this function
 */
int
nfs_scan_list(struct list_head *head, struct list_head *dst,
	      unsigned long idx_start, unsigned int npages)
{
	struct list_head	*pos, *tmp;
	struct nfs_page		*req;
	unsigned long		idx_end;
	int			res;

	res = 0;
	if (npages == 0)
		idx_end = ~0;
	else
		idx_end = idx_start + npages - 1;

	list_for_each_safe(pos, tmp, head) {

		req = nfs_list_entry(pos);

		if (req->wb_index < idx_start)
			continue;
		if (req->wb_index > idx_end)
			break;

		if (!nfs_set_page_writeback_locked(req))
			continue;
		nfs_list_remove_request(req);
		nfs_list_add_request(req, dst);
		res++;
	}
	return res;
}

int nfs_init_nfspagecache(void)
{
	nfs_page_cachep = kmem_cache_create("nfs_page",
					    sizeof(struct nfs_page),
					    0, SLAB_HWCACHE_ALIGN,
					    NULL, NULL);
	if (nfs_page_cachep == NULL)
		return -ENOMEM;

	return 0;
}

void nfs_destroy_nfspagecache(void)
{
	if (kmem_cache_destroy(nfs_page_cachep))
		printk(KERN_INFO "nfs_page: not all structures were freed\n");
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/fs/nfs/pagelist.c
	3	*
	4	* A set of helper functions for managing NFS read and write requests.
	5	* The main purpose of these routines is to provide support for the
	6	* coalescing of several requests into a single RPC call.
	7	*
	8	* Copyright 2000, 2001 (c) Trond Myklebust <[email protected]>
	9	*
	10	*/
	11
	12	#include <linux/config.h>
	13	#include <linux/slab.h>
	14	#include <linux/file.h>
	15	#include <linux/sunrpc/clnt.h>
	16	#include <linux/nfs3.h>
	17	#include <linux/nfs4.h>
	18	#include <linux/nfs_page.h>
	19	#include <linux/nfs_fs.h>
	20	#include <linux/nfs_mount.h>
	21
	22	#define NFS_PARANOIA 1
	23
	24	static kmem_cache_t *nfs_page_cachep;
	25
	26	static inline struct nfs_page *
	27	nfs_page_alloc(void)
	28	{
	29	struct nfs_page *p;
	30	p = kmem_cache_alloc(nfs_page_cachep, SLAB_KERNEL);
	31	if (p) {
	32	memset(p, 0, sizeof(*p));
	33	INIT_LIST_HEAD(&p->wb_list);
	34	}
	35	return p;
	36	}
	37
	38	static inline void
	39	nfs_page_free(struct nfs_page *p)
	40	{
	41	kmem_cache_free(nfs_page_cachep, p);
	42	}
	43
	44	/**
	45	* nfs_create_request - Create an NFS read/write request.
	46	* @file: file descriptor to use
	47	* @inode: inode to which the request is attached
	48	* @page: page to write
	49	* @offset: starting offset within the page for the write
	50	* @count: number of bytes to read/write
	51	*
	52	* The page must be locked by the caller. This makes sure we never
	53	* create two different requests for the same page, and avoids
	54	* a possible deadlock when we reach the hard limit on the number
	55	* of dirty pages.
	56	* User should ensure it is safe to sleep in this function.
	57	*/
	58	struct nfs_page *
	59	nfs_create_request(struct nfs_open_context ctx, struct inode inode,
	60	struct page *page,
	61	unsigned int offset, unsigned int count)
	62	{
	63	struct nfs_server *server = NFS_SERVER(inode);
	64	struct nfs_page *req;
65
66	/* Deal with hard limits. */
67	for (;;) {
68	/* try to allocate the request struct */
69	req = nfs_page_alloc();
70	if (req != NULL)
71	break;
72
73	/* Try to free up at least one request in order to stay
74	* below the hard limit
75	*/
76	if (signalled() && (server->flags & NFS_MOUNT_INTR))
77	return ERR_PTR(-ERESTARTSYS);
78	yield();
79	}
80
81	/* Initialize the request struct. Initially, we assume a
82	* long write-back delay. This will be adjusted in
83	* update_nfs_request below if the region is not locked. */
84	req->wb_page = page;
85	atomic_set(&req->wb_complete, 0);
86	req->wb_index = page->index;
87	page_cache_get(page);
cd52ed35 TM	88	BUG_ON(PagePrivate(page));
	89	BUG_ON(!PageLocked(page));
	90	BUG_ON(page->mapping->host != inode);
1da177e4 LT	91	req->wb_offset = offset;
	92	req->wb_pgbase = offset;
	93	req->wb_bytes = count;
	94	atomic_set(&req->wb_count, 1);
	95	req->wb_context = get_nfs_open_context(ctx);
	96
	97	return req;
	98	}
	99
	100	/**
	101	* nfs_unlock_request - Unlock request and wake up sleepers.
	102	* @req:
	103	*/
	104	void nfs_unlock_request(struct nfs_page *req)
	105	{
	106	if (!NFS_WBACK_BUSY(req)) {
	107	printk(KERN_ERR "NFS: Invalid unlock attempted\n");
	108	BUG();
	109	}
	110	smp_mb__before_clear_bit();
	111	clear_bit(PG_BUSY, &req->wb_flags);
	112	smp_mb__after_clear_bit();
464a98bd	113	wake_up_bit(&req->wb_flags, PG_BUSY);
1da177e4 LT	114	nfs_release_request(req);
	115	}
	116
c6a556b8 TM	117	/**
	118	* nfs_set_page_writeback_locked - Lock a request for writeback
	119	* @req:
	120	*/
	121	int nfs_set_page_writeback_locked(struct nfs_page *req)
	122	{
	123	struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);
	124
	125	if (!nfs_lock_request(req))
	126	return 0;
	127	radix_tree_tag_set(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
	128	return 1;
	129	}
	130
	131	/**
	132	* nfs_clear_page_writeback - Unlock request and wake up sleepers
	133	*/
	134	void nfs_clear_page_writeback(struct nfs_page *req)
	135	{
	136	struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);
	137
deb7d638 TM	138	if (req->wb_page != NULL) {
	139	spin_lock(&nfsi->req_lock);
	140	radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
	141	spin_unlock(&nfsi->req_lock);
	142	}
c6a556b8 TM	143	nfs_unlock_request(req);
	144	}
	145
1da177e4 LT	146	/**
	147	* nfs_clear_request - Free up all resources allocated to the request
	148	* @req:
	149	*
	150	* Release page resources associated with a write request after it
	151	* has completed.
	152	*/
	153	void nfs_clear_request(struct nfs_page *req)
	154	{
cd52ed35 TM	155	struct page *page = req->wb_page;
cd52ed35 TM	156	if (page != NULL) {
cd52ed35	157	page_cache_release(page);
1da177e4 LT	158	req->wb_page = NULL;
	159	}
	160	}
	161
	162
	163	/**
	164	* nfs_release_request - Release the count on an NFS read/write request
	165	* @req: request to release
	166	*
	167	* Note: Should never be called with the spinlock held!
	168	*/
	169	void
	170	nfs_release_request(struct nfs_page *req)
	171	{
	172	if (!atomic_dec_and_test(&req->wb_count))
	173	return;
	174
	175	#ifdef NFS_PARANOIA
	176	BUG_ON (!list_empty(&req->wb_list));
	177	BUG_ON (NFS_WBACK_BUSY(req));
	178	#endif
	179
	180	/* Release struct file or cached credential */
	181	nfs_clear_request(req);
	182	put_nfs_open_context(req->wb_context);
	183	nfs_page_free(req);
	184	}
	185
464a98bd TM	186	static int nfs_wait_bit_interruptible(void *word)
	187	{
	188	int ret = 0;
	189
	190	if (signal_pending(current))
	191	ret = -ERESTARTSYS;
	192	else
	193	schedule();
	194	return ret;
	195	}
	196
1da177e4 LT	197	/**
	198	* nfs_wait_on_request - Wait for a request to complete.
	199	* @req: request to wait upon.
	200	*
	201	* Interruptible by signals only if mounted with intr flag.
	202	* The user is responsible for holding a count on the request.
	203	*/
	204	int
	205	nfs_wait_on_request(struct nfs_page *req)
	206	{
464a98bd TM	207	struct rpc_clnt *clnt = NFS_CLIENT(req->wb_context->dentry->d_inode);
	208	sigset_t oldmask;
	209	int ret = 0;
	210
	211	if (!test_bit(PG_BUSY, &req->wb_flags))
	212	goto out;
	213	/*
	214	* Note: the call to rpc_clnt_sigmask() suffices to ensure that we
	215	* are not interrupted if intr flag is not set
	216	*/
	217	rpc_clnt_sigmask(clnt, &oldmask);
	218	ret = out_of_line_wait_on_bit(&req->wb_flags, PG_BUSY,
	219	nfs_wait_bit_interruptible, TASK_INTERRUPTIBLE);
	220	rpc_clnt_sigunmask(clnt, &oldmask);
	221	out:
	222	return ret;
1da177e4 LT	223	}
	224
	225	/**
	226	* nfs_coalesce_requests - Split coalesced requests out from a list.
	227	* @head: source list
	228	* @dst: destination list
	229	* @nmax: maximum number of requests to coalesce
	230	*
	231	* Moves a maximum of 'nmax' elements from one list to another.
	232	* The elements are checked to ensure that they form a contiguous set
	233	* of pages, and that the RPC credentials are the same.
	234	*/
	235	int
	236	nfs_coalesce_requests(struct list_head head, struct list_head dst,
	237	unsigned int nmax)
	238	{
	239	struct nfs_page *req = NULL;
	240	unsigned int npages = 0;
	241
	242	while (!list_empty(head)) {
	243	struct nfs_page *prev = req;
	244
	245	req = nfs_list_entry(head->next);
	246	if (prev) {
	247	if (req->wb_context->cred != prev->wb_context->cred)
	248	break;
	249	if (req->wb_context->lockowner != prev->wb_context->lockowner)
	250	break;
	251	if (req->wb_context->state != prev->wb_context->state)
	252	break;
	253	if (req->wb_index != (prev->wb_index + 1))
	254	break;
	255
	256	if (req->wb_pgbase != 0)
	257	break;
	258	}
	259	nfs_list_remove_request(req);
	260	nfs_list_add_request(req, dst);
	261	npages++;
	262	if (req->wb_pgbase + req->wb_bytes != PAGE_CACHE_SIZE)
	263	break;
	264	if (npages >= nmax)
	265	break;
	266	}
	267	return npages;
	268	}
	269
3da28eb1 TM	270	#define NFS_SCAN_MAXENTRIES 16
	271	/**
	272	* nfs_scan_lock_dirty - Scan the radix tree for dirty requests
	273	* @nfsi: NFS inode
	274	* @dst: Destination list
	275	* @idx_start: lower bound of page->index to scan
	276	* @npages: idx_start + npages sets the upper bound to scan.
	277	*
	278	* Moves elements from one of the inode request lists.
	279	* If the number of requests is set to 0, the entire address_space
	280	* starting at index idx_start, is scanned.
	281	* The requests are not checked to ensure that they form a contiguous set.
	282	* You must be holding the inode's req_lock when calling this function
	283	*/
	284	int
	285	nfs_scan_lock_dirty(struct nfs_inode nfsi, struct list_head dst,
	286	unsigned long idx_start, unsigned int npages)
	287	{
	288	struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
	289	struct nfs_page *req;
	290	unsigned long idx_end;
	291	int found, i;
	292	int res;
	293
	294	res = 0;
	295	if (npages == 0)
	296	idx_end = ~0;
	297	else
	298	idx_end = idx_start + npages - 1;
	299
	300	for (;;) {
	301	found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree,
	302	(void **)&pgvec[0], idx_start, NFS_SCAN_MAXENTRIES,
	303	NFS_PAGE_TAG_DIRTY);
	304	if (found <= 0)
	305	break;
	306	for (i = 0; i < found; i++) {
	307	req = pgvec[i];
	308	if (req->wb_index > idx_end)
	309	goto out;
	310
	311	idx_start = req->wb_index + 1;
	312
	313	if (nfs_set_page_writeback_locked(req)) {
	314	radix_tree_tag_clear(&nfsi->nfs_page_tree,
	315	req->wb_index, NFS_PAGE_TAG_DIRTY);
	316	nfs_list_remove_request(req);
	317	nfs_list_add_request(req, dst);
	318	res++;
	319	}
	320	}
	321	}
	322	out:
	323	return res;
	324	}
	325
1da177e4 LT	326	/**
	327	* nfs_scan_list - Scan a list for matching requests
	328	* @head: One of the NFS inode request lists
	329	* @dst: Destination list
	330	* @idx_start: lower bound of page->index to scan
	331	* @npages: idx_start + npages sets the upper bound to scan.
	332	*
	333	* Moves elements from one of the inode request lists.
	334	* If the number of requests is set to 0, the entire address_space
	335	* starting at index idx_start, is scanned.
	336	* The requests are not checked to ensure that they form a contiguous set.
	337	* You must be holding the inode's req_lock when calling this function
	338	*/
	339	int
	340	nfs_scan_list(struct list_head head, struct list_head dst,
	341	unsigned long idx_start, unsigned int npages)
	342	{
	343	struct list_head pos, tmp;
	344	struct nfs_page *req;
	345	unsigned long idx_end;
	346	int res;
	347
	348	res = 0;
	349	if (npages == 0)
	350	idx_end = ~0;
	351	else
	352	idx_end = idx_start + npages - 1;
	353
	354	list_for_each_safe(pos, tmp, head) {
	355
	356	req = nfs_list_entry(pos);
	357
	358	if (req->wb_index < idx_start)
	359	continue;
	360	if (req->wb_index > idx_end)
	361	break;
	362
c6a556b8	363	if (!nfs_set_page_writeback_locked(req))
1da177e4 LT	364	continue;
	365	nfs_list_remove_request(req);
	366	nfs_list_add_request(req, dst);
	367	res++;
	368	}
	369	return res;
	370	}
	371
	372	int nfs_init_nfspagecache(void)
	373	{
	374	nfs_page_cachep = kmem_cache_create("nfs_page",
	375	sizeof(struct nfs_page),
	376	0, SLAB_HWCACHE_ALIGN,
	377	NULL, NULL);
	378	if (nfs_page_cachep == NULL)
	379	return -ENOMEM;
	380
	381	return 0;
	382	}
	383
	384	void nfs_destroy_nfspagecache(void)
	385	{
	386	if (kmem_cache_destroy(nfs_page_cachep))
	387	printk(KERN_INFO "nfs_page: not all structures were freed\n");
	388	}
	389