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/fs/nfs/pagelist.c

https://bitbucket.org/cyanogenmod/android_kernel_asus_tf300t
C | 504 lines | 326 code | 44 blank | 134 comment | 64 complexity | 1a103c8226b6c03df12551c14412cb7d MD5 | raw file
Possible License(s): LGPL-2.0, AGPL-1.0, GPL-2.0
  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
 12#include <linux/slab.h>
 13#include <linux/file.h>
 14#include <linux/sched.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#include "internal.h"
 23#include "pnfs.h"
 24
 25static struct kmem_cache *nfs_page_cachep;
 26
 27static inline struct nfs_page *
 28nfs_page_alloc(void)
 29{
 30	struct nfs_page	*p = kmem_cache_zalloc(nfs_page_cachep, GFP_KERNEL);
 31	if (p)
 32		INIT_LIST_HEAD(&p->wb_list);
 33	return p;
 34}
 35
 36static inline void
 37nfs_page_free(struct nfs_page *p)
 38{
 39	kmem_cache_free(nfs_page_cachep, p);
 40}
 41
 42/**
 43 * nfs_create_request - Create an NFS read/write request.
 44 * @file: file descriptor to use
 45 * @inode: inode to which the request is attached
 46 * @page: page to write
 47 * @offset: starting offset within the page for the write
 48 * @count: number of bytes to read/write
 49 *
 50 * The page must be locked by the caller. This makes sure we never
 51 * create two different requests for the same page.
 52 * User should ensure it is safe to sleep in this function.
 53 */
 54struct nfs_page *
 55nfs_create_request(struct nfs_open_context *ctx, struct inode *inode,
 56		   struct page *page,
 57		   unsigned int offset, unsigned int count)
 58{
 59	struct nfs_page		*req;
 60
 61	/* try to allocate the request struct */
 62	req = nfs_page_alloc();
 63	if (req == NULL)
 64		return ERR_PTR(-ENOMEM);
 65
 66	/* get lock context early so we can deal with alloc failures */
 67	req->wb_lock_context = nfs_get_lock_context(ctx);
 68	if (req->wb_lock_context == NULL) {
 69		nfs_page_free(req);
 70		return ERR_PTR(-ENOMEM);
 71	}
 72
 73	/* Initialize the request struct. Initially, we assume a
 74	 * long write-back delay. This will be adjusted in
 75	 * update_nfs_request below if the region is not locked. */
 76	req->wb_page    = page;
 77	atomic_set(&req->wb_complete, 0);
 78	req->wb_index	= page->index;
 79	page_cache_get(page);
 80	BUG_ON(PagePrivate(page));
 81	BUG_ON(!PageLocked(page));
 82	BUG_ON(page->mapping->host != inode);
 83	req->wb_offset  = offset;
 84	req->wb_pgbase	= offset;
 85	req->wb_bytes   = count;
 86	req->wb_context = get_nfs_open_context(ctx);
 87	kref_init(&req->wb_kref);
 88	return req;
 89}
 90
 91/**
 92 * nfs_unlock_request - Unlock request and wake up sleepers.
 93 * @req:
 94 */
 95void nfs_unlock_request(struct nfs_page *req)
 96{
 97	if (!NFS_WBACK_BUSY(req)) {
 98		printk(KERN_ERR "NFS: Invalid unlock attempted\n");
 99		BUG();
100	}
101	smp_mb__before_clear_bit();
102	clear_bit(PG_BUSY, &req->wb_flags);
103	smp_mb__after_clear_bit();
104	wake_up_bit(&req->wb_flags, PG_BUSY);
105	nfs_release_request(req);
106}
107
108/**
109 * nfs_set_page_tag_locked - Tag a request as locked
110 * @req:
111 */
112int nfs_set_page_tag_locked(struct nfs_page *req)
113{
114	if (!nfs_lock_request_dontget(req))
115		return 0;
116	if (test_bit(PG_MAPPED, &req->wb_flags))
117		radix_tree_tag_set(&NFS_I(req->wb_context->dentry->d_inode)->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED);
118	return 1;
119}
120
121/**
122 * nfs_clear_page_tag_locked - Clear request tag and wake up sleepers
123 */
124void nfs_clear_page_tag_locked(struct nfs_page *req)
125{
126	if (test_bit(PG_MAPPED, &req->wb_flags)) {
127		struct inode *inode = req->wb_context->dentry->d_inode;
128		struct nfs_inode *nfsi = NFS_I(inode);
129
130		spin_lock(&inode->i_lock);
131		radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED);
132		nfs_unlock_request(req);
133		spin_unlock(&inode->i_lock);
134	} else
135		nfs_unlock_request(req);
136}
137
138/*
139 * nfs_clear_request - Free up all resources allocated to the request
140 * @req:
141 *
142 * Release page and open context resources associated with a read/write
143 * request after it has completed.
144 */
145static void nfs_clear_request(struct nfs_page *req)
146{
147	struct page *page = req->wb_page;
148	struct nfs_open_context *ctx = req->wb_context;
149	struct nfs_lock_context *l_ctx = req->wb_lock_context;
150
151	if (page != NULL) {
152		page_cache_release(page);
153		req->wb_page = NULL;
154	}
155	if (l_ctx != NULL) {
156		nfs_put_lock_context(l_ctx);
157		req->wb_lock_context = NULL;
158	}
159	if (ctx != NULL) {
160		put_nfs_open_context(ctx);
161		req->wb_context = NULL;
162	}
163}
164
165
166/**
167 * nfs_release_request - Release the count on an NFS read/write request
168 * @req: request to release
169 *
170 * Note: Should never be called with the spinlock held!
171 */
172static void nfs_free_request(struct kref *kref)
173{
174	struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref);
175
176	/* Release struct file and open context */
177	nfs_clear_request(req);
178	nfs_page_free(req);
179}
180
181void nfs_release_request(struct nfs_page *req)
182{
183	kref_put(&req->wb_kref, nfs_free_request);
184}
185
186static int nfs_wait_bit_uninterruptible(void *word)
187{
188	io_schedule();
189	return 0;
190}
191
192/**
193 * nfs_wait_on_request - Wait for a request to complete.
194 * @req: request to wait upon.
195 *
196 * Interruptible by fatal signals only.
197 * The user is responsible for holding a count on the request.
198 */
199int
200nfs_wait_on_request(struct nfs_page *req)
201{
202	return wait_on_bit(&req->wb_flags, PG_BUSY,
203			nfs_wait_bit_uninterruptible,
204			TASK_UNINTERRUPTIBLE);
205}
206
207bool nfs_generic_pg_test(struct nfs_pageio_descriptor *desc, struct nfs_page *prev, struct nfs_page *req)
208{
209	/*
210	 * FIXME: ideally we should be able to coalesce all requests
211	 * that are not block boundary aligned, but currently this
212	 * is problematic for the case of bsize < PAGE_CACHE_SIZE,
213	 * since nfs_flush_multi and nfs_pagein_multi assume you
214	 * can have only one struct nfs_page.
215	 */
216	if (desc->pg_bsize < PAGE_SIZE)
217		return 0;
218
219	return desc->pg_count + req->wb_bytes <= desc->pg_bsize;
220}
221EXPORT_SYMBOL_GPL(nfs_generic_pg_test);
222
223/**
224 * nfs_pageio_init - initialise a page io descriptor
225 * @desc: pointer to descriptor
226 * @inode: pointer to inode
227 * @doio: pointer to io function
228 * @bsize: io block size
229 * @io_flags: extra parameters for the io function
230 */
231void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
232		     struct inode *inode,
233		     const struct nfs_pageio_ops *pg_ops,
234		     size_t bsize,
235		     int io_flags)
236{
237	INIT_LIST_HEAD(&desc->pg_list);
238	desc->pg_bytes_written = 0;
239	desc->pg_count = 0;
240	desc->pg_bsize = bsize;
241	desc->pg_base = 0;
242	desc->pg_moreio = 0;
243	desc->pg_recoalesce = 0;
244	desc->pg_inode = inode;
245	desc->pg_ops = pg_ops;
246	desc->pg_ioflags = io_flags;
247	desc->pg_error = 0;
248	desc->pg_lseg = NULL;
249}
250
251/**
252 * nfs_can_coalesce_requests - test two requests for compatibility
253 * @prev: pointer to nfs_page
254 * @req: pointer to nfs_page
255 *
256 * The nfs_page structures 'prev' and 'req' are compared to ensure that the
257 * page data area they describe is contiguous, and that their RPC
258 * credentials, NFSv4 open state, and lockowners are the same.
259 *
260 * Return 'true' if this is the case, else return 'false'.
261 */
262static bool nfs_can_coalesce_requests(struct nfs_page *prev,
263				      struct nfs_page *req,
264				      struct nfs_pageio_descriptor *pgio)
265{
266	if (req->wb_context->cred != prev->wb_context->cred)
267		return false;
268	if (req->wb_lock_context->lockowner != prev->wb_lock_context->lockowner)
269		return false;
270	if (req->wb_context->state != prev->wb_context->state)
271		return false;
272	if (req->wb_index != (prev->wb_index + 1))
273		return false;
274	if (req->wb_pgbase != 0)
275		return false;
276	if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
277		return false;
278	return pgio->pg_ops->pg_test(pgio, prev, req);
279}
280
281/**
282 * nfs_pageio_do_add_request - Attempt to coalesce a request into a page list.
283 * @desc: destination io descriptor
284 * @req: request
285 *
286 * Returns true if the request 'req' was successfully coalesced into the
287 * existing list of pages 'desc'.
288 */
289static int nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc,
290				     struct nfs_page *req)
291{
292	if (desc->pg_count != 0) {
293		struct nfs_page *prev;
294
295		prev = nfs_list_entry(desc->pg_list.prev);
296		if (!nfs_can_coalesce_requests(prev, req, desc))
297			return 0;
298	} else {
299		if (desc->pg_ops->pg_init)
300			desc->pg_ops->pg_init(desc, req);
301		desc->pg_base = req->wb_pgbase;
302	}
303	nfs_list_remove_request(req);
304	nfs_list_add_request(req, &desc->pg_list);
305	desc->pg_count += req->wb_bytes;
306	return 1;
307}
308
309/*
310 * Helper for nfs_pageio_add_request and nfs_pageio_complete
311 */
312static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc)
313{
314	if (!list_empty(&desc->pg_list)) {
315		int error = desc->pg_ops->pg_doio(desc);
316		if (error < 0)
317			desc->pg_error = error;
318		else
319			desc->pg_bytes_written += desc->pg_count;
320	}
321	if (list_empty(&desc->pg_list)) {
322		desc->pg_count = 0;
323		desc->pg_base = 0;
324	}
325}
326
327/**
328 * nfs_pageio_add_request - Attempt to coalesce a request into a page list.
329 * @desc: destination io descriptor
330 * @req: request
331 *
332 * Returns true if the request 'req' was successfully coalesced into the
333 * existing list of pages 'desc'.
334 */
335static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
336			   struct nfs_page *req)
337{
338	while (!nfs_pageio_do_add_request(desc, req)) {
339		desc->pg_moreio = 1;
340		nfs_pageio_doio(desc);
341		if (desc->pg_error < 0)
342			return 0;
343		desc->pg_moreio = 0;
344		if (desc->pg_recoalesce)
345			return 0;
346	}
347	return 1;
348}
349
350static int nfs_do_recoalesce(struct nfs_pageio_descriptor *desc)
351{
352	LIST_HEAD(head);
353
354	do {
355		list_splice_init(&desc->pg_list, &head);
356		desc->pg_bytes_written -= desc->pg_count;
357		desc->pg_count = 0;
358		desc->pg_base = 0;
359		desc->pg_recoalesce = 0;
360
361		while (!list_empty(&head)) {
362			struct nfs_page *req;
363
364			req = list_first_entry(&head, struct nfs_page, wb_list);
365			nfs_list_remove_request(req);
366			if (__nfs_pageio_add_request(desc, req))
367				continue;
368			if (desc->pg_error < 0)
369				return 0;
370			break;
371		}
372	} while (desc->pg_recoalesce);
373	return 1;
374}
375
376int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
377		struct nfs_page *req)
378{
379	int ret;
380
381	do {
382		ret = __nfs_pageio_add_request(desc, req);
383		if (ret)
384			break;
385		if (desc->pg_error < 0)
386			break;
387		ret = nfs_do_recoalesce(desc);
388	} while (ret);
389	return ret;
390}
391
392/**
393 * nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor
394 * @desc: pointer to io descriptor
395 */
396void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
397{
398	for (;;) {
399		nfs_pageio_doio(desc);
400		if (!desc->pg_recoalesce)
401			break;
402		if (!nfs_do_recoalesce(desc))
403			break;
404	}
405}
406
407/**
408 * nfs_pageio_cond_complete - Conditional I/O completion
409 * @desc: pointer to io descriptor
410 * @index: page index
411 *
412 * It is important to ensure that processes don't try to take locks
413 * on non-contiguous ranges of pages as that might deadlock. This
414 * function should be called before attempting to wait on a locked
415 * nfs_page. It will complete the I/O if the page index 'index'
416 * is not contiguous with the existing list of pages in 'desc'.
417 */
418void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index)
419{
420	if (!list_empty(&desc->pg_list)) {
421		struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev);
422		if (index != prev->wb_index + 1)
423			nfs_pageio_complete(desc);
424	}
425}
426
427#define NFS_SCAN_MAXENTRIES 16
428/**
429 * nfs_scan_list - Scan a list for matching requests
430 * @nfsi: NFS inode
431 * @dst: Destination list
432 * @idx_start: lower bound of page->index to scan
433 * @npages: idx_start + npages sets the upper bound to scan.
434 * @tag: tag to scan for
435 *
436 * Moves elements from one of the inode request lists.
437 * If the number of requests is set to 0, the entire address_space
438 * starting at index idx_start, is scanned.
439 * The requests are *not* checked to ensure that they form a contiguous set.
440 * You must be holding the inode's i_lock when calling this function
441 */
442int nfs_scan_list(struct nfs_inode *nfsi,
443		struct list_head *dst, pgoff_t idx_start,
444		unsigned int npages, int tag)
445{
446	struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
447	struct nfs_page *req;
448	pgoff_t idx_end;
449	int found, i;
450	int res;
451	struct list_head *list;
452
453	res = 0;
454	if (npages == 0)
455		idx_end = ~0;
456	else
457		idx_end = idx_start + npages - 1;
458
459	for (;;) {
460		found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree,
461				(void **)&pgvec[0], idx_start,
462				NFS_SCAN_MAXENTRIES, tag);
463		if (found <= 0)
464			break;
465		for (i = 0; i < found; i++) {
466			req = pgvec[i];
467			if (req->wb_index > idx_end)
468				goto out;
469			idx_start = req->wb_index + 1;
470			if (nfs_set_page_tag_locked(req)) {
471				kref_get(&req->wb_kref);
472				radix_tree_tag_clear(&nfsi->nfs_page_tree,
473						req->wb_index, tag);
474				list = pnfs_choose_commit_list(req, dst);
475				nfs_list_add_request(req, list);
476				res++;
477				if (res == INT_MAX)
478					goto out;
479			}
480		}
481		/* for latency reduction */
482		cond_resched_lock(&nfsi->vfs_inode.i_lock);
483	}
484out:
485	return res;
486}
487
488int __init nfs_init_nfspagecache(void)
489{
490	nfs_page_cachep = kmem_cache_create("nfs_page",
491					    sizeof(struct nfs_page),
492					    0, SLAB_HWCACHE_ALIGN,
493					    NULL);
494	if (nfs_page_cachep == NULL)
495		return -ENOMEM;
496
497	return 0;
498}
499
500void nfs_destroy_nfspagecache(void)
501{
502	kmem_cache_destroy(nfs_page_cachep);
503}
504