[net-next-2.6.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 <trond.myklebust@fys.uio.no>
 *
 */

#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 struct kmem_cache *nfs_page_cachep;

static inline struct nfs_page *
nfs_page_alloc(void)
{
	struct nfs_page	*p;
	p = kmem_cache_alloc(nfs_page_cachep, GFP_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);
				dec_zone_page_state(req->wb_page, NR_FILE_DIRTY);
				res++;
			}
		}
	}
out:
	return res;
}

/**
 * nfs_scan_list - Scan a list for matching requests
 * @nfsi: NFS inode
 * @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 nfs_inode *nfsi, struct list_head *head,
		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(&nfsi->nfs_page_tree,
				(void **)&pgvec[0], idx_start,
				NFS_SCAN_MAXENTRIES);
		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 (req->wb_list_head != head)
				continue;
			if (nfs_set_page_writeback_locked(req)) {
				nfs_list_remove_request(req);
				nfs_list_add_request(req, dst);
				res++;
			}
		}

	}
out:
	return res;
}

int __init 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)
{
	kmem_cache_destroy(nfs_page_cachep);
}
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 <trond.myklebust@fys.uio.no>
	9	*
	10	*/
	11
1da177e4 LT	12	#include <linux/slab.h>
	13	#include <linux/file.h>
	14	#include <linux/sunrpc/clnt.h>
	15	#include <linux/nfs3.h>
	16	#include <linux/nfs4.h>
	17	#include <linux/nfs_page.h>
	18	#include <linux/nfs_fs.h>
	19	#include <linux/nfs_mount.h>
	20
	21	#define NFS_PARANOIA 1
	22
e18b890b	23	static struct kmem_cache *nfs_page_cachep;
1da177e4 LT	24
	25	static inline struct nfs_page *
	26	nfs_page_alloc(void)
	27	{
	28	struct nfs_page *p;
e94b1766	29	p = kmem_cache_alloc(nfs_page_cachep, GFP_KERNEL);
1da177e4 LT	30	if (p) {
	31	memset(p, 0, sizeof(*p));
	32	INIT_LIST_HEAD(&p->wb_list);
	33	}
	34	return p;
	35	}
	36
	37	static inline void
	38	nfs_page_free(struct nfs_page *p)
	39	{
	40	kmem_cache_free(nfs_page_cachep, p);
	41	}
	42
	43	/**
	44	* nfs_create_request - Create an NFS read/write request.
	45	* @file: file descriptor to use
	46	* @inode: inode to which the request is attached
	47	* @page: page to write
	48	* @offset: starting offset within the page for the write
	49	* @count: number of bytes to read/write
	50	*
	51	* The page must be locked by the caller. This makes sure we never
	52	* create two different requests for the same page, and avoids
	53	* a possible deadlock when we reach the hard limit on the number
	54	* of dirty pages.
	55	* User should ensure it is safe to sleep in this function.
	56	*/
	57	struct nfs_page *
	58	nfs_create_request(struct nfs_open_context ctx, struct inode inode,
	59	struct page *page,
	60	unsigned int offset, unsigned int count)
	61	{
	62	struct nfs_server *server = NFS_SERVER(inode);
	63	struct nfs_page *req;
	64
	65	/* Deal with hard limits. */
	66	for (;;) {
	67	/* try to allocate the request struct */
	68	req = nfs_page_alloc();
	69	if (req != NULL)
	70	break;
	71
	72	/* Try to free up at least one request in order to stay
	73	* below the hard limit
	74	*/
	75	if (signalled() && (server->flags & NFS_MOUNT_INTR))
	76	return ERR_PTR(-ERESTARTSYS);
	77	yield();
	78	}
	79
	80	/* Initialize the request struct. Initially, we assume a
	81	* long write-back delay. This will be adjusted in
	82	* update_nfs_request below if the region is not locked. */
	83	req->wb_page = page;
	84	atomic_set(&req->wb_complete, 0);
	85	req->wb_index = page->index;
	86	page_cache_get(page);
cd52ed35 TM	87	BUG_ON(PagePrivate(page));
	88	BUG_ON(!PageLocked(page));
	89	BUG_ON(page->mapping->host != inode);
1da177e4 LT	90	req->wb_offset = offset;
	91	req->wb_pgbase = offset;
	92	req->wb_bytes = count;
	93	atomic_set(&req->wb_count, 1);
	94	req->wb_context = get_nfs_open_context(ctx);
	95
	96	return req;
	97	}
	98
	99	/**
	100	* nfs_unlock_request - Unlock request and wake up sleepers.
	101	* @req:
	102	*/
	103	void nfs_unlock_request(struct nfs_page *req)
	104	{
	105	if (!NFS_WBACK_BUSY(req)) {
	106	printk(KERN_ERR "NFS: Invalid unlock attempted\n");
	107	BUG();
	108	}
	109	smp_mb__before_clear_bit();
	110	clear_bit(PG_BUSY, &req->wb_flags);
	111	smp_mb__after_clear_bit();
464a98bd	112	wake_up_bit(&req->wb_flags, PG_BUSY);
1da177e4 LT	113	nfs_release_request(req);
	114	}
	115
c6a556b8 TM	116	/**
	117	* nfs_set_page_writeback_locked - Lock a request for writeback
	118	* @req:
	119	*/
	120	int nfs_set_page_writeback_locked(struct nfs_page *req)
	121	{
	122	struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);
	123
	124	if (!nfs_lock_request(req))
	125	return 0;
	126	radix_tree_tag_set(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
	127	return 1;
	128	}
	129
	130	/**
	131	* nfs_clear_page_writeback - Unlock request and wake up sleepers
	132	*/
	133	void nfs_clear_page_writeback(struct nfs_page *req)
	134	{
	135	struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);
	136
deb7d638 TM	137	if (req->wb_page != NULL) {
	138	spin_lock(&nfsi->req_lock);
	139	radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
	140	spin_unlock(&nfsi->req_lock);
	141	}
c6a556b8 TM	142	nfs_unlock_request(req);
	143	}
	144
1da177e4 LT	145	/**
	146	* nfs_clear_request - Free up all resources allocated to the request
	147	* @req:
	148	*
	149	* Release page resources associated with a write request after it
	150	* has completed.
	151	*/
	152	void nfs_clear_request(struct nfs_page *req)
	153	{
cd52ed35 TM	154	struct page *page = req->wb_page;
cd52ed35 TM	155	if (page != NULL) {
cd52ed35	156	page_cache_release(page);
1da177e4 LT	157	req->wb_page = NULL;
	158	}
	159	}
	160
	161
	162	/**
	163	* nfs_release_request - Release the count on an NFS read/write request
	164	* @req: request to release
	165	*
	166	* Note: Should never be called with the spinlock held!
	167	*/
	168	void
	169	nfs_release_request(struct nfs_page *req)
	170	{
	171	if (!atomic_dec_and_test(&req->wb_count))
	172	return;
	173
	174	#ifdef NFS_PARANOIA
	175	BUG_ON (!list_empty(&req->wb_list));
	176	BUG_ON (NFS_WBACK_BUSY(req));
	177	#endif
	178
	179	/* Release struct file or cached credential */
	180	nfs_clear_request(req);
	181	put_nfs_open_context(req->wb_context);
	182	nfs_page_free(req);
	183	}
	184
464a98bd TM	185	static int nfs_wait_bit_interruptible(void *word)
	186	{
	187	int ret = 0;
	188
	189	if (signal_pending(current))
	190	ret = -ERESTARTSYS;
	191	else
	192	schedule();
	193	return ret;
	194	}
	195
1da177e4 LT	196	/**
	197	* nfs_wait_on_request - Wait for a request to complete.
	198	* @req: request to wait upon.
	199	*
	200	* Interruptible by signals only if mounted with intr flag.
	201	* The user is responsible for holding a count on the request.
	202	*/
	203	int
	204	nfs_wait_on_request(struct nfs_page *req)
	205	{
464a98bd TM	206	struct rpc_clnt *clnt = NFS_CLIENT(req->wb_context->dentry->d_inode);
	207	sigset_t oldmask;
	208	int ret = 0;
	209
	210	if (!test_bit(PG_BUSY, &req->wb_flags))
	211	goto out;
	212	/*
	213	* Note: the call to rpc_clnt_sigmask() suffices to ensure that we
	214	* are not interrupted if intr flag is not set
	215	*/
	216	rpc_clnt_sigmask(clnt, &oldmask);
	217	ret = out_of_line_wait_on_bit(&req->wb_flags, PG_BUSY,
	218	nfs_wait_bit_interruptible, TASK_INTERRUPTIBLE);
	219	rpc_clnt_sigunmask(clnt, &oldmask);
	220	out:
	221	return ret;
1da177e4 LT	222	}
	223
	224	/**
	225	* nfs_coalesce_requests - Split coalesced requests out from a list.
	226	* @head: source list
	227	* @dst: destination list
	228	* @nmax: maximum number of requests to coalesce
	229	*
	230	* Moves a maximum of 'nmax' elements from one list to another.
	231	* The elements are checked to ensure that they form a contiguous set
	232	* of pages, and that the RPC credentials are the same.
	233	*/
	234	int
	235	nfs_coalesce_requests(struct list_head head, struct list_head dst,
	236	unsigned int nmax)
	237	{
	238	struct nfs_page *req = NULL;
	239	unsigned int npages = 0;
	240
	241	while (!list_empty(head)) {
	242	struct nfs_page *prev = req;
	243
	244	req = nfs_list_entry(head->next);
	245	if (prev) {
	246	if (req->wb_context->cred != prev->wb_context->cred)
	247	break;
	248	if (req->wb_context->lockowner != prev->wb_context->lockowner)
	249	break;
	250	if (req->wb_context->state != prev->wb_context->state)
	251	break;
	252	if (req->wb_index != (prev->wb_index + 1))
	253	break;
	254
	255	if (req->wb_pgbase != 0)
	256	break;
	257	}
	258	nfs_list_remove_request(req);
	259	nfs_list_add_request(req, dst);
	260	npages++;
	261	if (req->wb_pgbase + req->wb_bytes != PAGE_CACHE_SIZE)
	262	break;
	263	if (npages >= nmax)
	264	break;
	265	}
	266	return npages;
	267	}
	268
3da28eb1 TM	269	#define NFS_SCAN_MAXENTRIES 16
	270	/**
	271	* nfs_scan_lock_dirty - Scan the radix tree for dirty requests
	272	* @nfsi: NFS inode
	273	* @dst: Destination list
	274	* @idx_start: lower bound of page->index to scan
	275	* @npages: idx_start + npages sets the upper bound to scan.
	276	*
	277	* Moves elements from one of the inode request lists.
	278	* If the number of requests is set to 0, the entire address_space
	279	* starting at index idx_start, is scanned.
	280	* The requests are not checked to ensure that they form a contiguous set.
	281	* You must be holding the inode's req_lock when calling this function
	282	*/
	283	int
	284	nfs_scan_lock_dirty(struct nfs_inode nfsi, struct list_head dst,
	285	unsigned long idx_start, unsigned int npages)
	286	{
	287	struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
	288	struct nfs_page *req;
	289	unsigned long idx_end;
	290	int found, i;
	291	int res;
	292
	293	res = 0;
	294	if (npages == 0)
	295	idx_end = ~0;
	296	else
	297	idx_end = idx_start + npages - 1;
	298
	299	for (;;) {
	300	found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree,
	301	(void **)&pgvec[0], idx_start, NFS_SCAN_MAXENTRIES,
	302	NFS_PAGE_TAG_DIRTY);
	303	if (found <= 0)
	304	break;
	305	for (i = 0; i < found; i++) {
	306	req = pgvec[i];
	307	if (req->wb_index > idx_end)
	308	goto out;
	309
	310	idx_start = req->wb_index + 1;
	311
	312	if (nfs_set_page_writeback_locked(req)) {
	313	radix_tree_tag_clear(&nfsi->nfs_page_tree,
	314	req->wb_index, NFS_PAGE_TAG_DIRTY);
	315	nfs_list_remove_request(req);
	316	nfs_list_add_request(req, dst);
b1e7a8fd	317	dec_zone_page_state(req->wb_page, NR_FILE_DIRTY);
3da28eb1 TM	318	res++;
	319	}
	320	}
	321	}
	322	out:
	323	return res;
	324	}
	325
1da177e4 LT	326	/**
1da177e4 LT	327	* nfs_scan_list - Scan a list for matching requests
d2ccddf0	328	* @nfsi: NFS inode
1da177e4 LT	329	* @head: One of the NFS inode request lists
	330	* @dst: Destination list
	331	* @idx_start: lower bound of page->index to scan
	332	* @npages: idx_start + npages sets the upper bound to scan.
	333	*
	334	* Moves elements from one of the inode request lists.
	335	* If the number of requests is set to 0, the entire address_space
	336	* starting at index idx_start, is scanned.
	337	* The requests are not checked to ensure that they form a contiguous set.
	338	* You must be holding the inode's req_lock when calling this function
	339	*/
d2ccddf0 TM	340	int nfs_scan_list(struct nfs_inode nfsi, struct list_head head,
	341	struct list_head *dst, unsigned long idx_start,
	342	unsigned int npages)
1da177e4	343	{
d2ccddf0 TM	344	struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
	345	struct nfs_page *req;
	346	unsigned long idx_end;
	347	int found, i;
	348	int res;
1da177e4 LT	349
	350	res = 0;
	351	if (npages == 0)
	352	idx_end = ~0;
	353	else
	354	idx_end = idx_start + npages - 1;
	355
d2ccddf0 TM	356	for (;;) {
	357	found = radix_tree_gang_lookup(&nfsi->nfs_page_tree,
	358	(void **)&pgvec[0], idx_start,
	359	NFS_SCAN_MAXENTRIES);
	360	if (found <= 0)
1da177e4	361	break;
d2ccddf0 TM	362	for (i = 0; i < found; i++) {
	363	req = pgvec[i];
	364	if (req->wb_index > idx_end)
	365	goto out;
	366	idx_start = req->wb_index + 1;
	367	if (req->wb_list_head != head)
	368	continue;
	369	if (nfs_set_page_writeback_locked(req)) {
	370	nfs_list_remove_request(req);
	371	nfs_list_add_request(req, dst);
	372	res++;
	373	}
	374	}
1da177e4	375
1da177e4	376	}
d2ccddf0	377	out:
1da177e4 LT	378	return res;
	379	}
	380
f7b422b1	381	int __init nfs_init_nfspagecache(void)
1da177e4 LT	382	{
	383	nfs_page_cachep = kmem_cache_create("nfs_page",
	384	sizeof(struct nfs_page),
	385	0, SLAB_HWCACHE_ALIGN,
	386	NULL, NULL);
	387	if (nfs_page_cachep == NULL)
	388	return -ENOMEM;
	389
	390	return 0;
	391	}
	392
266bee88	393	void nfs_destroy_nfspagecache(void)
1da177e4	394	{
1a1d92c1	395	kmem_cache_destroy(nfs_page_cachep);
1da177e4 LT	396	}
1da177e4 LT	397