[linux-2.6-block.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>
#include <linux/writeback.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_pageio_init - initialise a page io descriptor
 * @desc: pointer to descriptor
 * @iosize: io block size
 */
void nfs_pageio_init(struct nfs_pageio_descriptor *desc, unsigned int bsize)
{
	INIT_LIST_HEAD(&desc->pg_list);
	desc->pg_count = 0;
	desc->pg_bsize = bsize;
	desc->pg_base = 0;
}

/**
 * nfs_can_coalesce_requests - test two requests for compatibility
 * @prev: pointer to nfs_page
 * @req: pointer to nfs_page
 *
 * The nfs_page structures 'prev' and 'req' are compared to ensure that the
 * page data area they describe is contiguous, and that their RPC
 * credentials, NFSv4 open state, and lockowners are the same.
 *
 * Return 'true' if this is the case, else return 'false'.
 */
static int nfs_can_coalesce_requests(struct nfs_page *prev,
				     struct nfs_page *req)
{
	if (req->wb_context->cred != prev->wb_context->cred)
		return 0;
	if (req->wb_context->lockowner != prev->wb_context->lockowner)
		return 0;
	if (req->wb_context->state != prev->wb_context->state)
		return 0;
	if (req->wb_index != (prev->wb_index + 1))
		return 0;
	if (req->wb_pgbase != 0)
		return 0;
	if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
		return 0;
	return 1;
}

/**
 * nfs_pageio_add_request - Attempt to coalesce a request into a page list.
 * @desc: destination io descriptor
 * @req: request
 *
 * Returns true if the request 'req' was successfully coalesced into the
 * existing list of pages 'desc'.
 */
static int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
				  struct nfs_page *req)
{
	size_t newlen = req->wb_bytes;

	if (desc->pg_count != 0) {
		struct nfs_page *prev;

		/*
		 * FIXME: ideally we should be able to coalesce all requests
		 * that are not block boundary aligned, but currently this
		 * is problematic for the case of bsize < PAGE_CACHE_SIZE,
		 * since nfs_flush_multi and nfs_pagein_multi assume you
		 * can have only one struct nfs_page.
		 */
		newlen += desc->pg_count;
		if (desc->pg_base + newlen > desc->pg_bsize)
			return 0;
		prev = nfs_list_entry(desc->pg_list.prev);
		if (!nfs_can_coalesce_requests(prev, req))
			return 0;
	} else
		desc->pg_base = req->wb_pgbase;
	nfs_list_remove_request(req);
	nfs_list_add_request(req, &desc->pg_list);
	desc->pg_count = newlen;
	return 1;
}

/**
 * nfs_pageio_add_list - Split coalesced requests out from a list.
 * @desc: destination io descriptor
 * @head: source list
 *
 * 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.
 */
void nfs_pageio_add_list(struct nfs_pageio_descriptor *desc,
			 struct list_head *head)
{
	while (!list_empty(head)) {
		struct nfs_page *req = nfs_list_entry(head->next);
		if (!nfs_pageio_add_request(desc, req))
			break;
	}
}

#define NFS_SCAN_MAXENTRIES 16
/**
 * nfs_scan_dirty - Scan the radix tree for dirty requests
 * @mapping: pointer to address space
 * @wbc: writeback_control structure
 * @dst: Destination list
 *
 * 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
 */
long nfs_scan_dirty(struct address_space *mapping,
			struct writeback_control *wbc,
			struct list_head *dst)
{
	struct nfs_inode *nfsi = NFS_I(mapping->host);
	struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
	struct nfs_page *req;
	pgoff_t idx_start, idx_end;
	long res = 0;
	int found, i;

	if (nfsi->ndirty == 0)
		return 0;
	if (wbc->range_cyclic) {
		idx_start = 0;
		idx_end = ULONG_MAX;
	} else if (wbc->range_end == 0) {
		idx_start = wbc->range_start >> PAGE_CACHE_SHIFT;
		idx_end = ULONG_MAX;
	} else {
		idx_start = wbc->range_start >> PAGE_CACHE_SHIFT;
		idx_end = wbc->range_end >> PAGE_CACHE_SHIFT;
	}

	for (;;) {
		unsigned int toscan = NFS_SCAN_MAXENTRIES;

		found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree,
				(void **)&pgvec[0], idx_start, toscan,
				NFS_PAGE_TAG_DIRTY);

		/* Did we make progress? */
		if (found <= 0)
			break;

		for (i = 0; i < found; i++) {
			req = pgvec[i];
			if (!wbc->range_cyclic && req->wb_index > idx_end)
				goto out;

			/* Try to lock request and mark it for writeback */
			if (!nfs_set_page_writeback_locked(req))
				goto next;
			radix_tree_tag_clear(&nfsi->nfs_page_tree,
					req->wb_index, NFS_PAGE_TAG_DIRTY);
			nfsi->ndirty--;
			nfs_list_remove_request(req);
			nfs_list_add_request(req, dst);
			res++;
			if (res == LONG_MAX)
				goto out;
next:
			idx_start = req->wb_index + 1;
		}
	}
out:
	WARN_ON ((nfsi->ndirty == 0) != list_empty(&nfsi->dirty));
	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>
3f442547	20	#include <linux/writeback.h>
1da177e4 LT	21
	22	#define NFS_PARANOIA 1
	23
e18b890b	24	static struct kmem_cache *nfs_page_cachep;
1da177e4 LT	25
	26	static inline struct nfs_page *
	27	nfs_page_alloc(void)
	28	{
	29	struct nfs_page *p;
e94b1766	30	p = kmem_cache_alloc(nfs_page_cachep, GFP_KERNEL);
1da177e4 LT	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	/**
d8a5ad75 TM	226	* nfs_pageio_init - initialise a page io descriptor
	227	* @desc: pointer to descriptor
	228	* @iosize: io block size
	229	*/
	230	void nfs_pageio_init(struct nfs_pageio_descriptor *desc, unsigned int bsize)
	231	{
	232	INIT_LIST_HEAD(&desc->pg_list);
	233	desc->pg_count = 0;
	234	desc->pg_bsize = bsize;
	235	desc->pg_base = 0;
	236	}
	237
	238	/**
	239	* nfs_can_coalesce_requests - test two requests for compatibility
	240	* @prev: pointer to nfs_page
	241	* @req: pointer to nfs_page
	242	*
	243	* The nfs_page structures 'prev' and 'req' are compared to ensure that the
	244	* page data area they describe is contiguous, and that their RPC
	245	* credentials, NFSv4 open state, and lockowners are the same.
	246	*
	247	* Return 'true' if this is the case, else return 'false'.
	248	*/
	249	static int nfs_can_coalesce_requests(struct nfs_page *prev,
	250	struct nfs_page *req)
	251	{
	252	if (req->wb_context->cred != prev->wb_context->cred)
	253	return 0;
	254	if (req->wb_context->lockowner != prev->wb_context->lockowner)
	255	return 0;
	256	if (req->wb_context->state != prev->wb_context->state)
	257	return 0;
	258	if (req->wb_index != (prev->wb_index + 1))
	259	return 0;
	260	if (req->wb_pgbase != 0)
	261	return 0;
	262	if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
	263	return 0;
	264	return 1;
	265	}
	266
	267	/**
	268	* nfs_pageio_add_request - Attempt to coalesce a request into a page list.
	269	* @desc: destination io descriptor
	270	* @req: request
	271	*
	272	* Returns true if the request 'req' was successfully coalesced into the
	273	* existing list of pages 'desc'.
	274	*/
	275	static int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
	276	struct nfs_page *req)
	277	{
	278	size_t newlen = req->wb_bytes;
	279
	280	if (desc->pg_count != 0) {
	281	struct nfs_page *prev;
	282
	283	/*
	284	* FIXME: ideally we should be able to coalesce all requests
	285	* that are not block boundary aligned, but currently this
	286	* is problematic for the case of bsize < PAGE_CACHE_SIZE,
	287	* since nfs_flush_multi and nfs_pagein_multi assume you
	288	* can have only one struct nfs_page.
	289	*/
290	newlen += desc->pg_count;
291	if (desc->pg_base + newlen > desc->pg_bsize)
292	return 0;
293	prev = nfs_list_entry(desc->pg_list.prev);
294	if (!nfs_can_coalesce_requests(prev, req))
295	return 0;
296	} else
297	desc->pg_base = req->wb_pgbase;
298	nfs_list_remove_request(req);
299	nfs_list_add_request(req, &desc->pg_list);
300	desc->pg_count = newlen;
301	return 1;
302	}
303
304	/**
305	* nfs_pageio_add_list - Split coalesced requests out from a list.
306	* @desc: destination io descriptor
1da177e4	307	* @head: source list
1da177e4 LT	308	*
	309	* Moves a maximum of 'nmax' elements from one list to another.
	310	* The elements are checked to ensure that they form a contiguous set
	311	* of pages, and that the RPC credentials are the same.
	312	*/
d8a5ad75 TM	313	void nfs_pageio_add_list(struct nfs_pageio_descriptor *desc,
d8a5ad75 TM	314	struct list_head *head)
1da177e4	315	{
1da177e4	316	while (!list_empty(head)) {
d8a5ad75 TM	317	struct nfs_page *req = nfs_list_entry(head->next);
d8a5ad75 TM	318	if (!nfs_pageio_add_request(desc, req))
1da177e4 LT	319	break;
1da177e4 LT	320	}
1da177e4 LT	321	}
1da177e4 LT	322
3da28eb1 TM	323	#define NFS_SCAN_MAXENTRIES 16
3da28eb1 TM	324	/**
3f442547 TM	325	* nfs_scan_dirty - Scan the radix tree for dirty requests
	326	* @mapping: pointer to address space
	327	* @wbc: writeback_control structure
3da28eb1	328	* @dst: Destination list
3da28eb1 TM	329	*
	330	* Moves elements from one of the inode request lists.
	331	* If the number of requests is set to 0, the entire address_space
	332	* starting at index idx_start, is scanned.
	333	* The requests are not checked to ensure that they form a contiguous set.
	334	* You must be holding the inode's req_lock when calling this function
	335	*/
3f442547 TM	336	long nfs_scan_dirty(struct address_space *mapping,
	337	struct writeback_control *wbc,
	338	struct list_head *dst)
3da28eb1	339	{
3f442547	340	struct nfs_inode *nfsi = NFS_I(mapping->host);
3da28eb1 TM	341	struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
3da28eb1 TM	342	struct nfs_page *req;
3f442547	343	pgoff_t idx_start, idx_end;
3f442547	344	long res = 0;
3da28eb1	345	int found, i;
3da28eb1	346
9cf85e0a	347	if (nfsi->ndirty == 0)
3f442547 TM	348	return 0;
	349	if (wbc->range_cyclic) {
	350	idx_start = 0;
	351	idx_end = ULONG_MAX;
	352	} else if (wbc->range_end == 0) {
	353	idx_start = wbc->range_start >> PAGE_CACHE_SHIFT;
	354	idx_end = ULONG_MAX;
	355	} else {
	356	idx_start = wbc->range_start >> PAGE_CACHE_SHIFT;
	357	idx_end = wbc->range_end >> PAGE_CACHE_SHIFT;
	358	}
3da28eb1 TM	359
3da28eb1 TM	360	for (;;) {
3f442547 TM	361	unsigned int toscan = NFS_SCAN_MAXENTRIES;
3f442547 TM	362
3da28eb1	363	found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree,
3f442547	364	(void **)&pgvec[0], idx_start, toscan,
3da28eb1	365	NFS_PAGE_TAG_DIRTY);
3f442547 TM	366
3f442547 TM	367	/* Did we make progress? */
3da28eb1 TM	368	if (found <= 0)
3da28eb1 TM	369	break;
3f442547	370
3da28eb1 TM	371	for (i = 0; i < found; i++) {
3da28eb1 TM	372	req = pgvec[i];
3f442547	373	if (!wbc->range_cyclic && req->wb_index > idx_end)
3da28eb1 TM	374	goto out;
3da28eb1 TM	375
3f442547 TM	376	/* Try to lock request and mark it for writeback */
	377	if (!nfs_set_page_writeback_locked(req))
	378	goto next;
	379	radix_tree_tag_clear(&nfsi->nfs_page_tree,
	380	req->wb_index, NFS_PAGE_TAG_DIRTY);
	381	nfsi->ndirty--;
	382	nfs_list_remove_request(req);
	383	nfs_list_add_request(req, dst);
3f442547 TM	384	res++;
	385	if (res == LONG_MAX)
	386	goto out;
3f442547 TM	387	next:
3f442547 TM	388	idx_start = req->wb_index + 1;
3da28eb1 TM	389	}
	390	}
	391	out:
3f442547	392	WARN_ON ((nfsi->ndirty == 0) != list_empty(&nfsi->dirty));
3da28eb1 TM	393	return res;
	394	}
	395
1da177e4 LT	396	/**
1da177e4 LT	397	* nfs_scan_list - Scan a list for matching requests
d2ccddf0	398	* @nfsi: NFS inode
1da177e4 LT	399	* @head: One of the NFS inode request lists
	400	* @dst: Destination list
	401	* @idx_start: lower bound of page->index to scan
	402	* @npages: idx_start + npages sets the upper bound to scan.
	403	*
	404	* Moves elements from one of the inode request lists.
	405	* If the number of requests is set to 0, the entire address_space
	406	* starting at index idx_start, is scanned.
	407	* The requests are not checked to ensure that they form a contiguous set.
	408	* You must be holding the inode's req_lock when calling this function
	409	*/
d2ccddf0 TM	410	int nfs_scan_list(struct nfs_inode nfsi, struct list_head head,
	411	struct list_head *dst, unsigned long idx_start,
	412	unsigned int npages)
1da177e4	413	{
d2ccddf0 TM	414	struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
	415	struct nfs_page *req;
	416	unsigned long idx_end;
	417	int found, i;
	418	int res;
1da177e4 LT	419
	420	res = 0;
	421	if (npages == 0)
	422	idx_end = ~0;
	423	else
	424	idx_end = idx_start + npages - 1;
	425
d2ccddf0 TM	426	for (;;) {
	427	found = radix_tree_gang_lookup(&nfsi->nfs_page_tree,
	428	(void **)&pgvec[0], idx_start,
	429	NFS_SCAN_MAXENTRIES);
	430	if (found <= 0)
1da177e4	431	break;
d2ccddf0 TM	432	for (i = 0; i < found; i++) {
	433	req = pgvec[i];
	434	if (req->wb_index > idx_end)
	435	goto out;
	436	idx_start = req->wb_index + 1;
	437	if (req->wb_list_head != head)
	438	continue;
	439	if (nfs_set_page_writeback_locked(req)) {
	440	nfs_list_remove_request(req);
	441	nfs_list_add_request(req, dst);
	442	res++;
	443	}
	444	}
1da177e4	445
1da177e4	446	}
d2ccddf0	447	out:
1da177e4 LT	448	return res;
	449	}
	450
f7b422b1	451	int __init nfs_init_nfspagecache(void)
1da177e4 LT	452	{
	453	nfs_page_cachep = kmem_cache_create("nfs_page",
	454	sizeof(struct nfs_page),
	455	0, SLAB_HWCACHE_ALIGN,
	456	NULL, NULL);
	457	if (nfs_page_cachep == NULL)
	458	return -ENOMEM;
	459
	460	return 0;
	461	}
	462
266bee88	463	void nfs_destroy_nfspagecache(void)
1da177e4	464	{
1a1d92c1	465	kmem_cache_destroy(nfs_page_cachep);
1da177e4 LT	466	}
1da177e4 LT	467