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/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/nfs_page.h>
18 #include <linux/nfs_fs.h>
19 #include <linux/nfs_flushd.h>
20 #include <linux/nfs_mount.h>
21
22 #define NFS_PARANOIA 1
23
24 /*
25 * Spinlock
26 */
27 spinlock_t nfs_wreq_lock = SPIN_LOCK_UNLOCKED;
28
29 static kmem_cache_t *nfs_page_cachep;
30
31 static inline struct nfs_page *
nfs_page_alloc(void)32 nfs_page_alloc(void)
33 {
34 struct nfs_page *p;
35 p = kmem_cache_alloc(nfs_page_cachep, SLAB_NOFS);
36 if (p) {
37 memset(p, 0, sizeof(*p));
38 INIT_LIST_HEAD(&p->wb_hash);
39 INIT_LIST_HEAD(&p->wb_list);
40 INIT_LIST_HEAD(&p->wb_lru);
41 init_waitqueue_head(&p->wb_wait);
42 }
43 return p;
44 }
45
46 static inline void
nfs_page_free(struct nfs_page * p)47 nfs_page_free(struct nfs_page *p)
48 {
49 kmem_cache_free(nfs_page_cachep, p);
50 }
51
52 static int nfs_try_to_free_pages(struct nfs_server *);
53
54 /**
55 * nfs_create_request - Create an NFS read/write request.
56 * @cred: RPC credential to use
57 * @inode: inode to which the request is attached
58 * @page: page to write
59 * @offset: starting offset within the page for the write
60 * @count: number of bytes to read/write
61 *
62 * The page must be locked by the caller. This makes sure we never
63 * create two different requests for the same page, and avoids
64 * a possible deadlock when we reach the hard limit on the number
65 * of dirty pages.
66 * User should ensure it is safe to sleep in this function.
67 */
68 struct nfs_page *
nfs_create_request(struct rpc_cred * cred,struct inode * inode,struct page * page,unsigned int offset,unsigned int count)69 nfs_create_request(struct rpc_cred *cred, struct inode *inode,
70 struct page *page,
71 unsigned int offset, unsigned int count)
72 {
73 struct nfs_server *server = NFS_SERVER(inode);
74 struct nfs_reqlist *cache = NFS_REQUESTLIST(inode);
75 struct nfs_page *req;
76
77 /* Deal with hard limits. */
78 for (;;) {
79 /* Prevent races by incrementing *before* we test */
80 atomic_inc(&cache->nr_requests);
81
82 /* If we haven't reached the local hard limit yet,
83 * try to allocate the request struct */
84 if (atomic_read(&cache->nr_requests) <= MAX_REQUEST_HARD) {
85 req = nfs_page_alloc();
86 if (req != NULL)
87 break;
88 }
89
90 atomic_dec(&cache->nr_requests);
91
92 /* Try to free up at least one request in order to stay
93 * below the hard limit
94 */
95 if (nfs_try_to_free_pages(server))
96 continue;
97 if (signalled() && (server->flags & NFS_MOUNT_INTR))
98 return ERR_PTR(-ERESTARTSYS);
99 yield();
100 }
101
102 /* Initialize the request struct. Initially, we assume a
103 * long write-back delay. This will be adjusted in
104 * update_nfs_request below if the region is not locked. */
105 req->wb_page = page;
106 page_cache_get(page);
107 req->wb_offset = offset;
108 req->wb_bytes = count;
109
110 if (cred)
111 req->wb_cred = get_rpccred(cred);
112 req->wb_inode = inode;
113 req->wb_count = 1;
114
115 return req;
116 }
117
118 /**
119 * nfs_clear_request - Free up all resources allocated to the request
120 * @req:
121 *
122 * Release all resources associated with a write request after it
123 * has completed.
124 */
nfs_clear_request(struct nfs_page * req)125 void nfs_clear_request(struct nfs_page *req)
126 {
127 /* Release struct file or cached credential */
128 if (req->wb_file) {
129 fput(req->wb_file);
130 req->wb_file = NULL;
131 }
132 if (req->wb_cred) {
133 put_rpccred(req->wb_cred);
134 req->wb_cred = NULL;
135 }
136 if (req->wb_page) {
137 atomic_dec(&NFS_REQUESTLIST(req->wb_inode)->nr_requests);
138 #ifdef NFS_PARANOIA
139 BUG_ON(atomic_read(&NFS_REQUESTLIST(req->wb_inode)->nr_requests) < 0);
140 #endif
141 page_cache_release(req->wb_page);
142 req->wb_page = NULL;
143 }
144 }
145
146
147 /**
148 * nfs_release_request - Release the count on an NFS read/write request
149 * @req: request to release
150 *
151 * Note: Should never be called with the spinlock held!
152 */
153 void
nfs_release_request(struct nfs_page * req)154 nfs_release_request(struct nfs_page *req)
155 {
156 spin_lock(&nfs_wreq_lock);
157 if (--req->wb_count) {
158 spin_unlock(&nfs_wreq_lock);
159 return;
160 }
161 __nfs_del_lru(req);
162 spin_unlock(&nfs_wreq_lock);
163
164 #ifdef NFS_PARANOIA
165 BUG_ON(!list_empty(&req->wb_list));
166 BUG_ON(!list_empty(&req->wb_hash));
167 BUG_ON(NFS_WBACK_BUSY(req));
168 #endif
169
170 /* Release struct file or cached credential */
171 nfs_clear_request(req);
172 nfs_page_free(req);
173 }
174
175 /**
176 * nfs_list_add_request - Insert a request into a sorted list
177 * @req: request
178 * @head: head of list into which to insert the request.
179 *
180 * Note that the wb_list is sorted by page index in order to facilitate
181 * coalescing of requests.
182 * We use an insertion sort that is optimized for the case of appended
183 * writes.
184 */
185 void
nfs_list_add_request(struct nfs_page * req,struct list_head * head)186 nfs_list_add_request(struct nfs_page *req, struct list_head *head)
187 {
188 struct list_head *pos;
189 unsigned long pg_idx = page_index(req->wb_page);
190
191 #ifdef NFS_PARANOIA
192 if (!list_empty(&req->wb_list)) {
193 printk(KERN_ERR "NFS: Add to list failed!\n");
194 BUG();
195 }
196 #endif
197 list_for_each_prev(pos, head) {
198 struct nfs_page *p = nfs_list_entry(pos);
199 if (page_index(p->wb_page) < pg_idx)
200 break;
201 }
202 list_add(&req->wb_list, pos);
203 req->wb_list_head = head;
204 }
205
206 /**
207 * nfs_wait_on_request - Wait for a request to complete.
208 * @req: request to wait upon.
209 *
210 * Interruptible by signals only if mounted with intr flag.
211 * The user is responsible for holding a count on the request.
212 */
213 int
nfs_wait_on_request(struct nfs_page * req)214 nfs_wait_on_request(struct nfs_page *req)
215 {
216 struct inode *inode = req->wb_inode;
217 struct rpc_clnt *clnt = NFS_CLIENT(inode);
218
219 if (!NFS_WBACK_BUSY(req))
220 return 0;
221 return nfs_wait_event(clnt, req->wb_wait, !NFS_WBACK_BUSY(req));
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 they originated from the same file.
233 */
234 int
nfs_coalesce_requests(struct list_head * head,struct list_head * dst,unsigned int nmax)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_cred != prev->wb_cred)
247 break;
248 if (page_index(req->wb_page) != page_index(prev->wb_page)+1)
249 break;
250
251 if (req->wb_offset != 0)
252 break;
253 }
254 nfs_list_remove_request(req);
255 nfs_list_add_request(req, dst);
256 npages++;
257 if (req->wb_offset + req->wb_bytes != PAGE_CACHE_SIZE)
258 break;
259 if (npages >= nmax)
260 break;
261 }
262 return npages;
263 }
264
265 /*
266 * nfs_scan_forward - Coalesce more requests
267 * @req: First request to add
268 * @dst: destination list
269 * @nmax: maximum number of requests to coalesce
270 *
271 * Tries to coalesce more requests by traversing the request's wb_list.
272 * Moves the resulting list into dst. Requests are guaranteed to be
273 * contiguous, and to originate from the same file.
274 */
275 static int
nfs_scan_forward(struct nfs_page * req,struct list_head * dst,int nmax)276 nfs_scan_forward(struct nfs_page *req, struct list_head *dst, int nmax)
277 {
278 struct nfs_server *server = NFS_SERVER(req->wb_inode);
279 struct list_head *pos, *head = req->wb_list_head;
280 struct rpc_cred *cred = req->wb_cred;
281 unsigned long idx = page_index(req->wb_page) + 1;
282 int npages = 0;
283
284 for (pos = req->wb_list.next; nfs_lock_request(req); pos = pos->next) {
285 nfs_list_remove_request(req);
286 nfs_list_add_request(req, dst);
287 __nfs_del_lru(req);
288 __nfs_add_lru(&server->lru_busy, req);
289 npages++;
290 if (npages == nmax)
291 break;
292 if (pos == head)
293 break;
294 if (req->wb_offset + req->wb_bytes != PAGE_CACHE_SIZE)
295 break;
296 req = nfs_list_entry(pos);
297 if (page_index(req->wb_page) != idx++)
298 break;
299 if (req->wb_offset != 0)
300 break;
301 if (req->wb_cred != cred)
302 break;
303 }
304 return npages;
305 }
306
307 /**
308 * nfs_scan_lru - Scan one of the least recently used list
309 * @head: One of the NFS superblock lru lists
310 * @dst: Destination list
311 * @nmax: maximum number of requests to coalesce
312 *
313 * Scans one of the NFS superblock lru lists for upto nmax requests
314 * and returns them on a list. The requests are all guaranteed to be
315 * contiguous, originating from the same inode and the same file.
316 */
317 int
nfs_scan_lru(struct list_head * head,struct list_head * dst,int nmax)318 nfs_scan_lru(struct list_head *head, struct list_head *dst, int nmax)
319 {
320 struct list_head *pos;
321 struct nfs_page *req;
322 int npages = 0;
323
324 list_for_each(pos, head) {
325 req = nfs_lru_entry(pos);
326 npages = nfs_scan_forward(req, dst, nmax);
327 if (npages)
328 break;
329 }
330 return npages;
331 }
332
333 /**
334 * nfs_scan_lru_timeout - Scan one of the superblock lru lists for timed out requests
335 * @head: One of the NFS superblock lru lists
336 * @dst: Destination list
337 * @nmax: maximum number of requests to coalesce
338 *
339 * Scans one of the NFS superblock lru lists for upto nmax requests
340 * and returns them on a list. The requests are all guaranteed to be
341 * contiguous, originating from the same inode and the same file.
342 * The first request on the destination list will be timed out, the
343 * others are not guaranteed to be so.
344 */
345 int
nfs_scan_lru_timeout(struct list_head * head,struct list_head * dst,int nmax)346 nfs_scan_lru_timeout(struct list_head *head, struct list_head *dst, int nmax)
347 {
348 struct list_head *pos;
349 struct nfs_page *req;
350 int npages = 0;
351
352 list_for_each(pos, head) {
353 req = nfs_lru_entry(pos);
354 if (time_after(req->wb_timeout, jiffies))
355 break;
356 npages = nfs_scan_forward(req, dst, nmax);
357 if (npages)
358 break;
359 }
360 return npages;
361 }
362
363 /**
364 * nfs_scan_list - Scan a list for matching requests
365 * @head: One of the NFS inode request lists
366 * @dst: Destination list
367 * @idx_start: lower bound of page->index to scan
368 * @npages: idx_start + npages sets the upper bound to scan.
369 *
370 * Moves elements from one of the inode request lists.
371 * If the number of requests is set to 0, the entire address_space
372 * starting at index idx_start, is scanned.
373 * The requests are *not* checked to ensure that they form a contiguous set.
374 * You must be holding the nfs_wreq_lock when calling this function
375 */
376 int
nfs_scan_list(struct list_head * head,struct list_head * dst,unsigned long idx_start,unsigned int npages)377 nfs_scan_list(struct list_head *head, struct list_head *dst,
378 unsigned long idx_start, unsigned int npages)
379 {
380 struct list_head *pos, *tmp;
381 struct nfs_page *req;
382 unsigned long idx_end;
383 int res;
384
385 res = 0;
386 if (npages == 0)
387 idx_end = ~0;
388 else
389 idx_end = idx_start + npages - 1;
390
391 list_for_each_safe(pos, tmp, head) {
392 unsigned long pg_idx;
393
394 req = nfs_list_entry(pos);
395
396 pg_idx = page_index(req->wb_page);
397 if (pg_idx < idx_start)
398 continue;
399 if (pg_idx > idx_end)
400 break;
401
402 if (!nfs_lock_request(req))
403 continue;
404 nfs_list_remove_request(req);
405 nfs_list_add_request(req, dst);
406 __nfs_del_lru(req);
407 __nfs_add_lru(&NFS_SERVER(req->wb_inode)->lru_busy, req);
408 res++;
409 }
410 return res;
411 }
412
413 /*
414 * nfs_try_to_free_pages - Free up NFS read/write requests
415 * @server: The NFS superblock
416 *
417 * This function attempts to flush out NFS reads and writes in order
418 * to keep the hard limit on the total number of pending requests
419 * on a given NFS partition.
420 * Note: we first try to commit unstable writes, then flush out pending
421 * reads, then finally the dirty pages.
422 * The assumption is that this reflects the ordering from the fastest
423 * to the slowest method for reclaiming requests.
424 */
425 static int
nfs_try_to_free_pages(struct nfs_server * server)426 nfs_try_to_free_pages(struct nfs_server *server)
427 {
428 LIST_HEAD(head);
429 struct nfs_page *req = NULL;
430 int nreq;
431
432 for (;;) {
433 if (req) {
434 int status = nfs_wait_on_request(req);
435 nfs_release_request(req);
436 if (status)
437 break;
438 req = NULL;
439 }
440 nreq = atomic_read(&server->rw_requests->nr_requests);
441 if (nreq < MAX_REQUEST_HARD)
442 return 1;
443 spin_lock(&nfs_wreq_lock);
444 /* Are there any busy RPC calls that might free up requests? */
445 if (!list_empty(&server->lru_busy)) {
446 req = nfs_lru_entry(server->lru_busy.next);
447 req->wb_count++;
448 __nfs_del_lru(req);
449 spin_unlock(&nfs_wreq_lock);
450 continue;
451 }
452
453 #ifdef CONFIG_NFS_V3
454 /* Let's try to free up some completed NFSv3 unstable writes */
455 nfs_scan_lru_commit(server, &head);
456 if (!list_empty(&head)) {
457 spin_unlock(&nfs_wreq_lock);
458 nfs_commit_list(&head, 0);
459 continue;
460 }
461 #endif
462 /* OK, so we try to free up some pending readaheads */
463 nfs_scan_lru_read(server, &head);
464 if (!list_empty(&head)) {
465 spin_unlock(&nfs_wreq_lock);
466 nfs_pagein_list(&head, server->rpages);
467 continue;
468 }
469 /* Last resort: we try to flush out single requests */
470 nfs_scan_lru_dirty(server, &head);
471 if (!list_empty(&head)) {
472 spin_unlock(&nfs_wreq_lock);
473 nfs_flush_list(&head, server->wpages, FLUSH_STABLE);
474 continue;
475 }
476 spin_unlock(&nfs_wreq_lock);
477 break;
478 }
479 /* We failed to free up requests */
480 return 0;
481 }
482
nfs_init_nfspagecache(void)483 int nfs_init_nfspagecache(void)
484 {
485 nfs_page_cachep = kmem_cache_create("nfs_page",
486 sizeof(struct nfs_page),
487 0, SLAB_HWCACHE_ALIGN,
488 NULL, NULL);
489 if (nfs_page_cachep == NULL)
490 return -ENOMEM;
491
492 return 0;
493 }
494
nfs_destroy_nfspagecache(void)495 void nfs_destroy_nfspagecache(void)
496 {
497 if (kmem_cache_destroy(nfs_page_cachep))
498 printk(KERN_INFO "nfs_page: not all structures were freed\n");
499 }
500
501