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Linux/fs/nfs/pagelist.c

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  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/nfs.h>
 17 #include <linux/nfs3.h>
 18 #include <linux/nfs4.h>
 19 #include <linux/nfs_page.h>
 20 #include <linux/nfs_fs.h>
 21 #include <linux/nfs_mount.h>
 22 #include <linux/export.h>
 23 
 24 #include "internal.h"
 25 #include "pnfs.h"
 26 
 27 #define NFSDBG_FACILITY         NFSDBG_PAGECACHE
 28 
 29 static struct kmem_cache *nfs_page_cachep;
 30 static const struct rpc_call_ops nfs_pgio_common_ops;
 31 
 32 static bool nfs_pgarray_set(struct nfs_page_array *p, unsigned int pagecount)
 33 {
 34         p->npages = pagecount;
 35         if (pagecount <= ARRAY_SIZE(p->page_array))
 36                 p->pagevec = p->page_array;
 37         else {
 38                 p->pagevec = kcalloc(pagecount, sizeof(struct page *), GFP_KERNEL);
 39                 if (!p->pagevec)
 40                         p->npages = 0;
 41         }
 42         return p->pagevec != NULL;
 43 }
 44 
 45 void nfs_pgheader_init(struct nfs_pageio_descriptor *desc,
 46                        struct nfs_pgio_header *hdr,
 47                        void (*release)(struct nfs_pgio_header *hdr))
 48 {
 49         hdr->req = nfs_list_entry(desc->pg_list.next);
 50         hdr->inode = desc->pg_inode;
 51         hdr->cred = hdr->req->wb_context->cred;
 52         hdr->io_start = req_offset(hdr->req);
 53         hdr->good_bytes = desc->pg_count;
 54         hdr->dreq = desc->pg_dreq;
 55         hdr->layout_private = desc->pg_layout_private;
 56         hdr->release = release;
 57         hdr->completion_ops = desc->pg_completion_ops;
 58         if (hdr->completion_ops->init_hdr)
 59                 hdr->completion_ops->init_hdr(hdr);
 60 }
 61 EXPORT_SYMBOL_GPL(nfs_pgheader_init);
 62 
 63 void nfs_set_pgio_error(struct nfs_pgio_header *hdr, int error, loff_t pos)
 64 {
 65         spin_lock(&hdr->lock);
 66         if (!test_and_set_bit(NFS_IOHDR_ERROR, &hdr->flags)
 67             || pos < hdr->io_start + hdr->good_bytes) {
 68                 clear_bit(NFS_IOHDR_EOF, &hdr->flags);
 69                 hdr->good_bytes = pos - hdr->io_start;
 70                 hdr->error = error;
 71         }
 72         spin_unlock(&hdr->lock);
 73 }
 74 
 75 static inline struct nfs_page *
 76 nfs_page_alloc(void)
 77 {
 78         struct nfs_page *p = kmem_cache_zalloc(nfs_page_cachep, GFP_NOIO);
 79         if (p)
 80                 INIT_LIST_HEAD(&p->wb_list);
 81         return p;
 82 }
 83 
 84 static inline void
 85 nfs_page_free(struct nfs_page *p)
 86 {
 87         kmem_cache_free(nfs_page_cachep, p);
 88 }
 89 
 90 static void
 91 nfs_iocounter_inc(struct nfs_io_counter *c)
 92 {
 93         atomic_inc(&c->io_count);
 94 }
 95 
 96 static void
 97 nfs_iocounter_dec(struct nfs_io_counter *c)
 98 {
 99         if (atomic_dec_and_test(&c->io_count)) {
100                 clear_bit(NFS_IO_INPROGRESS, &c->flags);
101                 smp_mb__after_atomic();
102                 wake_up_bit(&c->flags, NFS_IO_INPROGRESS);
103         }
104 }
105 
106 static int
107 __nfs_iocounter_wait(struct nfs_io_counter *c)
108 {
109         wait_queue_head_t *wq = bit_waitqueue(&c->flags, NFS_IO_INPROGRESS);
110         DEFINE_WAIT_BIT(q, &c->flags, NFS_IO_INPROGRESS);
111         int ret = 0;
112 
113         do {
114                 prepare_to_wait(wq, &q.wait, TASK_KILLABLE);
115                 set_bit(NFS_IO_INPROGRESS, &c->flags);
116                 if (atomic_read(&c->io_count) == 0)
117                         break;
118                 ret = nfs_wait_bit_killable(&q.key);
119         } while (atomic_read(&c->io_count) != 0 && !ret);
120         finish_wait(wq, &q.wait);
121         return ret;
122 }
123 
124 /**
125  * nfs_iocounter_wait - wait for i/o to complete
126  * @c: nfs_io_counter to use
127  *
128  * returns -ERESTARTSYS if interrupted by a fatal signal.
129  * Otherwise returns 0 once the io_count hits 0.
130  */
131 int
132 nfs_iocounter_wait(struct nfs_io_counter *c)
133 {
134         if (atomic_read(&c->io_count) == 0)
135                 return 0;
136         return __nfs_iocounter_wait(c);
137 }
138 
139 /*
140  * nfs_page_group_lock - lock the head of the page group
141  * @req - request in group that is to be locked
142  * @nonblock - if true don't block waiting for lock
143  *
144  * this lock must be held if modifying the page group list
145  *
146  * return 0 on success, < 0 on error: -EDELAY if nonblocking or the
147  * result from wait_on_bit_lock
148  *
149  * NOTE: calling with nonblock=false should always have set the
150  *       lock bit (see fs/buffer.c and other uses of wait_on_bit_lock
151  *       with TASK_UNINTERRUPTIBLE), so there is no need to check the result.
152  */
153 int
154 nfs_page_group_lock(struct nfs_page *req, bool nonblock)
155 {
156         struct nfs_page *head = req->wb_head;
157 
158         WARN_ON_ONCE(head != head->wb_head);
159 
160         if (!test_and_set_bit(PG_HEADLOCK, &head->wb_flags))
161                 return 0;
162 
163         if (!nonblock)
164                 return wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK,
165                                 TASK_UNINTERRUPTIBLE);
166 
167         return -EAGAIN;
168 }
169 
170 /*
171  * nfs_page_group_lock_wait - wait for the lock to clear, but don't grab it
172  * @req - a request in the group
173  *
174  * This is a blocking call to wait for the group lock to be cleared.
175  */
176 void
177 nfs_page_group_lock_wait(struct nfs_page *req)
178 {
179         struct nfs_page *head = req->wb_head;
180 
181         WARN_ON_ONCE(head != head->wb_head);
182 
183         wait_on_bit(&head->wb_flags, PG_HEADLOCK,
184                 TASK_UNINTERRUPTIBLE);
185 }
186 
187 /*
188  * nfs_page_group_unlock - unlock the head of the page group
189  * @req - request in group that is to be unlocked
190  */
191 void
192 nfs_page_group_unlock(struct nfs_page *req)
193 {
194         struct nfs_page *head = req->wb_head;
195 
196         WARN_ON_ONCE(head != head->wb_head);
197 
198         smp_mb__before_atomic();
199         clear_bit(PG_HEADLOCK, &head->wb_flags);
200         smp_mb__after_atomic();
201         wake_up_bit(&head->wb_flags, PG_HEADLOCK);
202 }
203 
204 /*
205  * nfs_page_group_sync_on_bit_locked
206  *
207  * must be called with page group lock held
208  */
209 static bool
210 nfs_page_group_sync_on_bit_locked(struct nfs_page *req, unsigned int bit)
211 {
212         struct nfs_page *head = req->wb_head;
213         struct nfs_page *tmp;
214 
215         WARN_ON_ONCE(!test_bit(PG_HEADLOCK, &head->wb_flags));
216         WARN_ON_ONCE(test_and_set_bit(bit, &req->wb_flags));
217 
218         tmp = req->wb_this_page;
219         while (tmp != req) {
220                 if (!test_bit(bit, &tmp->wb_flags))
221                         return false;
222                 tmp = tmp->wb_this_page;
223         }
224 
225         /* true! reset all bits */
226         tmp = req;
227         do {
228                 clear_bit(bit, &tmp->wb_flags);
229                 tmp = tmp->wb_this_page;
230         } while (tmp != req);
231 
232         return true;
233 }
234 
235 /*
236  * nfs_page_group_sync_on_bit - set bit on current request, but only
237  *   return true if the bit is set for all requests in page group
238  * @req - request in page group
239  * @bit - PG_* bit that is used to sync page group
240  */
241 bool nfs_page_group_sync_on_bit(struct nfs_page *req, unsigned int bit)
242 {
243         bool ret;
244 
245         nfs_page_group_lock(req, false);
246         ret = nfs_page_group_sync_on_bit_locked(req, bit);
247         nfs_page_group_unlock(req);
248 
249         return ret;
250 }
251 
252 /*
253  * nfs_page_group_init - Initialize the page group linkage for @req
254  * @req - a new nfs request
255  * @prev - the previous request in page group, or NULL if @req is the first
256  *         or only request in the group (the head).
257  */
258 static inline void
259 nfs_page_group_init(struct nfs_page *req, struct nfs_page *prev)
260 {
261         WARN_ON_ONCE(prev == req);
262 
263         if (!prev) {
264                 /* a head request */
265                 req->wb_head = req;
266                 req->wb_this_page = req;
267         } else {
268                 /* a subrequest */
269                 WARN_ON_ONCE(prev->wb_this_page != prev->wb_head);
270                 WARN_ON_ONCE(!test_bit(PG_HEADLOCK, &prev->wb_head->wb_flags));
271                 req->wb_head = prev->wb_head;
272                 req->wb_this_page = prev->wb_this_page;
273                 prev->wb_this_page = req;
274 
275                 /* All subrequests take a ref on the head request until
276                  * nfs_page_group_destroy is called */
277                 kref_get(&req->wb_head->wb_kref);
278 
279                 /* grab extra ref if head request has extra ref from
280                  * the write/commit path to handle handoff between write
281                  * and commit lists */
282                 if (test_bit(PG_INODE_REF, &prev->wb_head->wb_flags)) {
283                         set_bit(PG_INODE_REF, &req->wb_flags);
284                         kref_get(&req->wb_kref);
285                 }
286         }
287 }
288 
289 /*
290  * nfs_page_group_destroy - sync the destruction of page groups
291  * @req - request that no longer needs the page group
292  *
293  * releases the page group reference from each member once all
294  * members have called this function.
295  */
296 static void
297 nfs_page_group_destroy(struct kref *kref)
298 {
299         struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref);
300         struct nfs_page *tmp, *next;
301 
302         /* subrequests must release the ref on the head request */
303         if (req->wb_head != req)
304                 nfs_release_request(req->wb_head);
305 
306         if (!nfs_page_group_sync_on_bit(req, PG_TEARDOWN))
307                 return;
308 
309         tmp = req;
310         do {
311                 next = tmp->wb_this_page;
312                 /* unlink and free */
313                 tmp->wb_this_page = tmp;
314                 tmp->wb_head = tmp;
315                 nfs_free_request(tmp);
316                 tmp = next;
317         } while (tmp != req);
318 }
319 
320 /**
321  * nfs_create_request - Create an NFS read/write request.
322  * @ctx: open context to use
323  * @page: page to write
324  * @last: last nfs request created for this page group or NULL if head
325  * @offset: starting offset within the page for the write
326  * @count: number of bytes to read/write
327  *
328  * The page must be locked by the caller. This makes sure we never
329  * create two different requests for the same page.
330  * User should ensure it is safe to sleep in this function.
331  */
332 struct nfs_page *
333 nfs_create_request(struct nfs_open_context *ctx, struct page *page,
334                    struct nfs_page *last, unsigned int offset,
335                    unsigned int count)
336 {
337         struct nfs_page         *req;
338         struct nfs_lock_context *l_ctx;
339 
340         if (test_bit(NFS_CONTEXT_BAD, &ctx->flags))
341                 return ERR_PTR(-EBADF);
342         /* try to allocate the request struct */
343         req = nfs_page_alloc();
344         if (req == NULL)
345                 return ERR_PTR(-ENOMEM);
346 
347         /* get lock context early so we can deal with alloc failures */
348         l_ctx = nfs_get_lock_context(ctx);
349         if (IS_ERR(l_ctx)) {
350                 nfs_page_free(req);
351                 return ERR_CAST(l_ctx);
352         }
353         req->wb_lock_context = l_ctx;
354         nfs_iocounter_inc(&l_ctx->io_count);
355 
356         /* Initialize the request struct. Initially, we assume a
357          * long write-back delay. This will be adjusted in
358          * update_nfs_request below if the region is not locked. */
359         req->wb_page    = page;
360         req->wb_index   = page_file_index(page);
361         page_cache_get(page);
362         req->wb_offset  = offset;
363         req->wb_pgbase  = offset;
364         req->wb_bytes   = count;
365         req->wb_context = get_nfs_open_context(ctx);
366         kref_init(&req->wb_kref);
367         nfs_page_group_init(req, last);
368         return req;
369 }
370 
371 /**
372  * nfs_unlock_request - Unlock request and wake up sleepers.
373  * @req:
374  */
375 void nfs_unlock_request(struct nfs_page *req)
376 {
377         if (!NFS_WBACK_BUSY(req)) {
378                 printk(KERN_ERR "NFS: Invalid unlock attempted\n");
379                 BUG();
380         }
381         smp_mb__before_atomic();
382         clear_bit(PG_BUSY, &req->wb_flags);
383         smp_mb__after_atomic();
384         wake_up_bit(&req->wb_flags, PG_BUSY);
385 }
386 
387 /**
388  * nfs_unlock_and_release_request - Unlock request and release the nfs_page
389  * @req:
390  */
391 void nfs_unlock_and_release_request(struct nfs_page *req)
392 {
393         nfs_unlock_request(req);
394         nfs_release_request(req);
395 }
396 
397 /*
398  * nfs_clear_request - Free up all resources allocated to the request
399  * @req:
400  *
401  * Release page and open context resources associated with a read/write
402  * request after it has completed.
403  */
404 static void nfs_clear_request(struct nfs_page *req)
405 {
406         struct page *page = req->wb_page;
407         struct nfs_open_context *ctx = req->wb_context;
408         struct nfs_lock_context *l_ctx = req->wb_lock_context;
409 
410         if (page != NULL) {
411                 page_cache_release(page);
412                 req->wb_page = NULL;
413         }
414         if (l_ctx != NULL) {
415                 nfs_iocounter_dec(&l_ctx->io_count);
416                 nfs_put_lock_context(l_ctx);
417                 req->wb_lock_context = NULL;
418         }
419         if (ctx != NULL) {
420                 put_nfs_open_context(ctx);
421                 req->wb_context = NULL;
422         }
423 }
424 
425 /**
426  * nfs_release_request - Release the count on an NFS read/write request
427  * @req: request to release
428  *
429  * Note: Should never be called with the spinlock held!
430  */
431 void nfs_free_request(struct nfs_page *req)
432 {
433         WARN_ON_ONCE(req->wb_this_page != req);
434 
435         /* extra debug: make sure no sync bits are still set */
436         WARN_ON_ONCE(test_bit(PG_TEARDOWN, &req->wb_flags));
437         WARN_ON_ONCE(test_bit(PG_UNLOCKPAGE, &req->wb_flags));
438         WARN_ON_ONCE(test_bit(PG_UPTODATE, &req->wb_flags));
439         WARN_ON_ONCE(test_bit(PG_WB_END, &req->wb_flags));
440         WARN_ON_ONCE(test_bit(PG_REMOVE, &req->wb_flags));
441 
442         /* Release struct file and open context */
443         nfs_clear_request(req);
444         nfs_page_free(req);
445 }
446 
447 void nfs_release_request(struct nfs_page *req)
448 {
449         kref_put(&req->wb_kref, nfs_page_group_destroy);
450 }
451 
452 /**
453  * nfs_wait_on_request - Wait for a request to complete.
454  * @req: request to wait upon.
455  *
456  * Interruptible by fatal signals only.
457  * The user is responsible for holding a count on the request.
458  */
459 int
460 nfs_wait_on_request(struct nfs_page *req)
461 {
462         return wait_on_bit_io(&req->wb_flags, PG_BUSY,
463                               TASK_UNINTERRUPTIBLE);
464 }
465 
466 /*
467  * nfs_generic_pg_test - determine if requests can be coalesced
468  * @desc: pointer to descriptor
469  * @prev: previous request in desc, or NULL
470  * @req: this request
471  *
472  * Returns zero if @req can be coalesced into @desc, otherwise it returns
473  * the size of the request.
474  */
475 size_t nfs_generic_pg_test(struct nfs_pageio_descriptor *desc,
476                            struct nfs_page *prev, struct nfs_page *req)
477 {
478         if (desc->pg_count > desc->pg_bsize) {
479                 /* should never happen */
480                 WARN_ON_ONCE(1);
481                 return 0;
482         }
483 
484         /*
485          * Limit the request size so that we can still allocate a page array
486          * for it without upsetting the slab allocator.
487          */
488         if (((desc->pg_count + req->wb_bytes) >> PAGE_SHIFT) *
489                         sizeof(struct page *) > PAGE_SIZE)
490                 return 0;
491 
492         return min(desc->pg_bsize - desc->pg_count, (size_t)req->wb_bytes);
493 }
494 EXPORT_SYMBOL_GPL(nfs_generic_pg_test);
495 
496 struct nfs_pgio_header *nfs_pgio_header_alloc(const struct nfs_rw_ops *ops)
497 {
498         struct nfs_pgio_header *hdr = ops->rw_alloc_header();
499 
500         if (hdr) {
501                 INIT_LIST_HEAD(&hdr->pages);
502                 spin_lock_init(&hdr->lock);
503                 hdr->rw_ops = ops;
504         }
505         return hdr;
506 }
507 EXPORT_SYMBOL_GPL(nfs_pgio_header_alloc);
508 
509 /*
510  * nfs_pgio_header_free - Free a read or write header
511  * @hdr: The header to free
512  */
513 void nfs_pgio_header_free(struct nfs_pgio_header *hdr)
514 {
515         hdr->rw_ops->rw_free_header(hdr);
516 }
517 EXPORT_SYMBOL_GPL(nfs_pgio_header_free);
518 
519 /**
520  * nfs_pgio_data_destroy - make @hdr suitable for reuse
521  *
522  * Frees memory and releases refs from nfs_generic_pgio, so that it may
523  * be called again.
524  *
525  * @hdr: A header that has had nfs_generic_pgio called
526  */
527 void nfs_pgio_data_destroy(struct nfs_pgio_header *hdr)
528 {
529         if (hdr->args.context)
530                 put_nfs_open_context(hdr->args.context);
531         if (hdr->page_array.pagevec != hdr->page_array.page_array)
532                 kfree(hdr->page_array.pagevec);
533 }
534 EXPORT_SYMBOL_GPL(nfs_pgio_data_destroy);
535 
536 /**
537  * nfs_pgio_rpcsetup - Set up arguments for a pageio call
538  * @hdr: The pageio hdr
539  * @count: Number of bytes to read
540  * @offset: Initial offset
541  * @how: How to commit data (writes only)
542  * @cinfo: Commit information for the call (writes only)
543  */
544 static void nfs_pgio_rpcsetup(struct nfs_pgio_header *hdr,
545                               unsigned int count, unsigned int offset,
546                               int how, struct nfs_commit_info *cinfo)
547 {
548         struct nfs_page *req = hdr->req;
549 
550         /* Set up the RPC argument and reply structs
551          * NB: take care not to mess about with hdr->commit et al. */
552 
553         hdr->args.fh     = NFS_FH(hdr->inode);
554         hdr->args.offset = req_offset(req) + offset;
555         /* pnfs_set_layoutcommit needs this */
556         hdr->mds_offset = hdr->args.offset;
557         hdr->args.pgbase = req->wb_pgbase + offset;
558         hdr->args.pages  = hdr->page_array.pagevec;
559         hdr->args.count  = count;
560         hdr->args.context = get_nfs_open_context(req->wb_context);
561         hdr->args.lock_context = req->wb_lock_context;
562         hdr->args.stable  = NFS_UNSTABLE;
563         switch (how & (FLUSH_STABLE | FLUSH_COND_STABLE)) {
564         case 0:
565                 break;
566         case FLUSH_COND_STABLE:
567                 if (nfs_reqs_to_commit(cinfo))
568                         break;
569         default:
570                 hdr->args.stable = NFS_FILE_SYNC;
571         }
572 
573         hdr->res.fattr   = &hdr->fattr;
574         hdr->res.count   = count;
575         hdr->res.eof     = 0;
576         hdr->res.verf    = &hdr->verf;
577         nfs_fattr_init(&hdr->fattr);
578 }
579 
580 /**
581  * nfs_pgio_prepare - Prepare pageio hdr to go over the wire
582  * @task: The current task
583  * @calldata: pageio header to prepare
584  */
585 static void nfs_pgio_prepare(struct rpc_task *task, void *calldata)
586 {
587         struct nfs_pgio_header *hdr = calldata;
588         int err;
589         err = NFS_PROTO(hdr->inode)->pgio_rpc_prepare(task, hdr);
590         if (err)
591                 rpc_exit(task, err);
592 }
593 
594 int nfs_initiate_pgio(struct rpc_clnt *clnt, struct nfs_pgio_header *hdr,
595                       const struct rpc_call_ops *call_ops, int how, int flags)
596 {
597         struct rpc_task *task;
598         struct rpc_message msg = {
599                 .rpc_argp = &hdr->args,
600                 .rpc_resp = &hdr->res,
601                 .rpc_cred = hdr->cred,
602         };
603         struct rpc_task_setup task_setup_data = {
604                 .rpc_client = clnt,
605                 .task = &hdr->task,
606                 .rpc_message = &msg,
607                 .callback_ops = call_ops,
608                 .callback_data = hdr,
609                 .workqueue = nfsiod_workqueue,
610                 .flags = RPC_TASK_ASYNC | flags,
611         };
612         int ret = 0;
613 
614         hdr->rw_ops->rw_initiate(hdr, &msg, &task_setup_data, how);
615 
616         dprintk("NFS: %5u initiated pgio call "
617                 "(req %s/%llu, %u bytes @ offset %llu)\n",
618                 hdr->task.tk_pid,
619                 hdr->inode->i_sb->s_id,
620                 (unsigned long long)NFS_FILEID(hdr->inode),
621                 hdr->args.count,
622                 (unsigned long long)hdr->args.offset);
623 
624         task = rpc_run_task(&task_setup_data);
625         if (IS_ERR(task)) {
626                 ret = PTR_ERR(task);
627                 goto out;
628         }
629         if (how & FLUSH_SYNC) {
630                 ret = rpc_wait_for_completion_task(task);
631                 if (ret == 0)
632                         ret = task->tk_status;
633         }
634         rpc_put_task(task);
635 out:
636         return ret;
637 }
638 EXPORT_SYMBOL_GPL(nfs_initiate_pgio);
639 
640 /**
641  * nfs_pgio_error - Clean up from a pageio error
642  * @desc: IO descriptor
643  * @hdr: pageio header
644  */
645 static int nfs_pgio_error(struct nfs_pageio_descriptor *desc,
646                           struct nfs_pgio_header *hdr)
647 {
648         set_bit(NFS_IOHDR_REDO, &hdr->flags);
649         nfs_pgio_data_destroy(hdr);
650         hdr->completion_ops->completion(hdr);
651         desc->pg_completion_ops->error_cleanup(&desc->pg_list);
652         return -ENOMEM;
653 }
654 
655 /**
656  * nfs_pgio_release - Release pageio data
657  * @calldata: The pageio header to release
658  */
659 static void nfs_pgio_release(void *calldata)
660 {
661         struct nfs_pgio_header *hdr = calldata;
662         if (hdr->rw_ops->rw_release)
663                 hdr->rw_ops->rw_release(hdr);
664         nfs_pgio_data_destroy(hdr);
665         hdr->completion_ops->completion(hdr);
666 }
667 
668 /**
669  * nfs_pageio_init - initialise a page io descriptor
670  * @desc: pointer to descriptor
671  * @inode: pointer to inode
672  * @doio: pointer to io function
673  * @bsize: io block size
674  * @io_flags: extra parameters for the io function
675  */
676 void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
677                      struct inode *inode,
678                      const struct nfs_pageio_ops *pg_ops,
679                      const struct nfs_pgio_completion_ops *compl_ops,
680                      const struct nfs_rw_ops *rw_ops,
681                      size_t bsize,
682                      int io_flags)
683 {
684         INIT_LIST_HEAD(&desc->pg_list);
685         desc->pg_bytes_written = 0;
686         desc->pg_count = 0;
687         desc->pg_bsize = bsize;
688         desc->pg_base = 0;
689         desc->pg_moreio = 0;
690         desc->pg_recoalesce = 0;
691         desc->pg_inode = inode;
692         desc->pg_ops = pg_ops;
693         desc->pg_completion_ops = compl_ops;
694         desc->pg_rw_ops = rw_ops;
695         desc->pg_ioflags = io_flags;
696         desc->pg_error = 0;
697         desc->pg_lseg = NULL;
698         desc->pg_dreq = NULL;
699         desc->pg_layout_private = NULL;
700 }
701 EXPORT_SYMBOL_GPL(nfs_pageio_init);
702 
703 /**
704  * nfs_pgio_result - Basic pageio error handling
705  * @task: The task that ran
706  * @calldata: Pageio header to check
707  */
708 static void nfs_pgio_result(struct rpc_task *task, void *calldata)
709 {
710         struct nfs_pgio_header *hdr = calldata;
711         struct inode *inode = hdr->inode;
712 
713         dprintk("NFS: %s: %5u, (status %d)\n", __func__,
714                 task->tk_pid, task->tk_status);
715 
716         if (hdr->rw_ops->rw_done(task, hdr, inode) != 0)
717                 return;
718         if (task->tk_status < 0)
719                 nfs_set_pgio_error(hdr, task->tk_status, hdr->args.offset);
720         else
721                 hdr->rw_ops->rw_result(task, hdr);
722 }
723 
724 /*
725  * Create an RPC task for the given read or write request and kick it.
726  * The page must have been locked by the caller.
727  *
728  * It may happen that the page we're passed is not marked dirty.
729  * This is the case if nfs_updatepage detects a conflicting request
730  * that has been written but not committed.
731  */
732 int nfs_generic_pgio(struct nfs_pageio_descriptor *desc,
733                      struct nfs_pgio_header *hdr)
734 {
735         struct nfs_page         *req;
736         struct page             **pages,
737                                 *last_page;
738         struct list_head *head = &desc->pg_list;
739         struct nfs_commit_info cinfo;
740         unsigned int pagecount, pageused;
741 
742         pagecount = nfs_page_array_len(desc->pg_base, desc->pg_count);
743         if (!nfs_pgarray_set(&hdr->page_array, pagecount))
744                 return nfs_pgio_error(desc, hdr);
745 
746         nfs_init_cinfo(&cinfo, desc->pg_inode, desc->pg_dreq);
747         pages = hdr->page_array.pagevec;
748         last_page = NULL;
749         pageused = 0;
750         while (!list_empty(head)) {
751                 req = nfs_list_entry(head->next);
752                 nfs_list_remove_request(req);
753                 nfs_list_add_request(req, &hdr->pages);
754 
755                 if (!last_page || last_page != req->wb_page) {
756                         pageused++;
757                         if (pageused > pagecount)
758                                 break;
759                         *pages++ = last_page = req->wb_page;
760                 }
761         }
762         if (WARN_ON_ONCE(pageused != pagecount))
763                 return nfs_pgio_error(desc, hdr);
764 
765         if ((desc->pg_ioflags & FLUSH_COND_STABLE) &&
766             (desc->pg_moreio || nfs_reqs_to_commit(&cinfo)))
767                 desc->pg_ioflags &= ~FLUSH_COND_STABLE;
768 
769         /* Set up the argument struct */
770         nfs_pgio_rpcsetup(hdr, desc->pg_count, 0, desc->pg_ioflags, &cinfo);
771         desc->pg_rpc_callops = &nfs_pgio_common_ops;
772         return 0;
773 }
774 EXPORT_SYMBOL_GPL(nfs_generic_pgio);
775 
776 static int nfs_generic_pg_pgios(struct nfs_pageio_descriptor *desc)
777 {
778         struct nfs_pgio_header *hdr;
779         int ret;
780 
781         hdr = nfs_pgio_header_alloc(desc->pg_rw_ops);
782         if (!hdr) {
783                 desc->pg_completion_ops->error_cleanup(&desc->pg_list);
784                 return -ENOMEM;
785         }
786         nfs_pgheader_init(desc, hdr, nfs_pgio_header_free);
787         ret = nfs_generic_pgio(desc, hdr);
788         if (ret == 0)
789                 ret = nfs_initiate_pgio(NFS_CLIENT(hdr->inode),
790                                         hdr, desc->pg_rpc_callops,
791                                         desc->pg_ioflags, 0);
792         return ret;
793 }
794 
795 static bool nfs_match_open_context(const struct nfs_open_context *ctx1,
796                 const struct nfs_open_context *ctx2)
797 {
798         return ctx1->cred == ctx2->cred && ctx1->state == ctx2->state;
799 }
800 
801 static bool nfs_match_lock_context(const struct nfs_lock_context *l1,
802                 const struct nfs_lock_context *l2)
803 {
804         return l1->lockowner.l_owner == l2->lockowner.l_owner
805                 && l1->lockowner.l_pid == l2->lockowner.l_pid;
806 }
807 
808 /**
809  * nfs_can_coalesce_requests - test two requests for compatibility
810  * @prev: pointer to nfs_page
811  * @req: pointer to nfs_page
812  *
813  * The nfs_page structures 'prev' and 'req' are compared to ensure that the
814  * page data area they describe is contiguous, and that their RPC
815  * credentials, NFSv4 open state, and lockowners are the same.
816  *
817  * Return 'true' if this is the case, else return 'false'.
818  */
819 static bool nfs_can_coalesce_requests(struct nfs_page *prev,
820                                       struct nfs_page *req,
821                                       struct nfs_pageio_descriptor *pgio)
822 {
823         size_t size;
824 
825         if (prev) {
826                 if (!nfs_match_open_context(req->wb_context, prev->wb_context))
827                         return false;
828                 if (req->wb_context->dentry->d_inode->i_flock != NULL &&
829                     !nfs_match_lock_context(req->wb_lock_context,
830                                             prev->wb_lock_context))
831                         return false;
832                 if (req_offset(req) != req_offset(prev) + prev->wb_bytes)
833                         return false;
834                 if (req->wb_page == prev->wb_page) {
835                         if (req->wb_pgbase != prev->wb_pgbase + prev->wb_bytes)
836                                 return false;
837                 } else {
838                         if (req->wb_pgbase != 0 ||
839                             prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
840                                 return false;
841                 }
842         }
843         size = pgio->pg_ops->pg_test(pgio, prev, req);
844         WARN_ON_ONCE(size > req->wb_bytes);
845         if (size && size < req->wb_bytes)
846                 req->wb_bytes = size;
847         return size > 0;
848 }
849 
850 /**
851  * nfs_pageio_do_add_request - Attempt to coalesce a request into a page list.
852  * @desc: destination io descriptor
853  * @req: request
854  *
855  * Returns true if the request 'req' was successfully coalesced into the
856  * existing list of pages 'desc'.
857  */
858 static int nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc,
859                                      struct nfs_page *req)
860 {
861         struct nfs_page *prev = NULL;
862         if (desc->pg_count != 0) {
863                 prev = nfs_list_entry(desc->pg_list.prev);
864         } else {
865                 if (desc->pg_ops->pg_init)
866                         desc->pg_ops->pg_init(desc, req);
867                 desc->pg_base = req->wb_pgbase;
868         }
869         if (!nfs_can_coalesce_requests(prev, req, desc))
870                 return 0;
871         nfs_list_remove_request(req);
872         nfs_list_add_request(req, &desc->pg_list);
873         desc->pg_count += req->wb_bytes;
874         return 1;
875 }
876 
877 /*
878  * Helper for nfs_pageio_add_request and nfs_pageio_complete
879  */
880 static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc)
881 {
882         if (!list_empty(&desc->pg_list)) {
883                 int error = desc->pg_ops->pg_doio(desc);
884                 if (error < 0)
885                         desc->pg_error = error;
886                 else
887                         desc->pg_bytes_written += desc->pg_count;
888         }
889         if (list_empty(&desc->pg_list)) {
890                 desc->pg_count = 0;
891                 desc->pg_base = 0;
892         }
893 }
894 
895 /**
896  * nfs_pageio_add_request - Attempt to coalesce a request into a page list.
897  * @desc: destination io descriptor
898  * @req: request
899  *
900  * This may split a request into subrequests which are all part of the
901  * same page group.
902  *
903  * Returns true if the request 'req' was successfully coalesced into the
904  * existing list of pages 'desc'.
905  */
906 static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
907                            struct nfs_page *req)
908 {
909         struct nfs_page *subreq;
910         unsigned int bytes_left = 0;
911         unsigned int offset, pgbase;
912 
913         nfs_page_group_lock(req, false);
914 
915         subreq = req;
916         bytes_left = subreq->wb_bytes;
917         offset = subreq->wb_offset;
918         pgbase = subreq->wb_pgbase;
919 
920         do {
921                 if (!nfs_pageio_do_add_request(desc, subreq)) {
922                         /* make sure pg_test call(s) did nothing */
923                         WARN_ON_ONCE(subreq->wb_bytes != bytes_left);
924                         WARN_ON_ONCE(subreq->wb_offset != offset);
925                         WARN_ON_ONCE(subreq->wb_pgbase != pgbase);
926 
927                         nfs_page_group_unlock(req);
928                         desc->pg_moreio = 1;
929                         nfs_pageio_doio(desc);
930                         if (desc->pg_error < 0)
931                                 return 0;
932                         if (desc->pg_recoalesce)
933                                 return 0;
934                         /* retry add_request for this subreq */
935                         nfs_page_group_lock(req, false);
936                         continue;
937                 }
938 
939                 /* check for buggy pg_test call(s) */
940                 WARN_ON_ONCE(subreq->wb_bytes + subreq->wb_pgbase > PAGE_SIZE);
941                 WARN_ON_ONCE(subreq->wb_bytes > bytes_left);
942                 WARN_ON_ONCE(subreq->wb_bytes == 0);
943 
944                 bytes_left -= subreq->wb_bytes;
945                 offset += subreq->wb_bytes;
946                 pgbase += subreq->wb_bytes;
947 
948                 if (bytes_left) {
949                         subreq = nfs_create_request(req->wb_context,
950                                         req->wb_page,
951                                         subreq, pgbase, bytes_left);
952                         if (IS_ERR(subreq))
953                                 goto err_ptr;
954                         nfs_lock_request(subreq);
955                         subreq->wb_offset  = offset;
956                         subreq->wb_index = req->wb_index;
957                 }
958         } while (bytes_left > 0);
959 
960         nfs_page_group_unlock(req);
961         return 1;
962 err_ptr:
963         desc->pg_error = PTR_ERR(subreq);
964         nfs_page_group_unlock(req);
965         return 0;
966 }
967 
968 static int nfs_do_recoalesce(struct nfs_pageio_descriptor *desc)
969 {
970         LIST_HEAD(head);
971 
972         do {
973                 list_splice_init(&desc->pg_list, &head);
974                 desc->pg_bytes_written -= desc->pg_count;
975                 desc->pg_count = 0;
976                 desc->pg_base = 0;
977                 desc->pg_recoalesce = 0;
978                 desc->pg_moreio = 0;
979 
980                 while (!list_empty(&head)) {
981                         struct nfs_page *req;
982 
983                         req = list_first_entry(&head, struct nfs_page, wb_list);
984                         nfs_list_remove_request(req);
985                         if (__nfs_pageio_add_request(desc, req))
986                                 continue;
987                         if (desc->pg_error < 0)
988                                 return 0;
989                         break;
990                 }
991         } while (desc->pg_recoalesce);
992         return 1;
993 }
994 
995 int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
996                 struct nfs_page *req)
997 {
998         int ret;
999 
1000         do {
1001                 ret = __nfs_pageio_add_request(desc, req);
1002                 if (ret)
1003                         break;
1004                 if (desc->pg_error < 0)
1005                         break;
1006                 ret = nfs_do_recoalesce(desc);
1007         } while (ret);
1008         return ret;
1009 }
1010 
1011 /*
1012  * nfs_pageio_resend - Transfer requests to new descriptor and resend
1013  * @hdr - the pgio header to move request from
1014  * @desc - the pageio descriptor to add requests to
1015  *
1016  * Try to move each request (nfs_page) from @hdr to @desc then attempt
1017  * to send them.
1018  *
1019  * Returns 0 on success and < 0 on error.
1020  */
1021 int nfs_pageio_resend(struct nfs_pageio_descriptor *desc,
1022                       struct nfs_pgio_header *hdr)
1023 {
1024         LIST_HEAD(failed);
1025 
1026         desc->pg_dreq = hdr->dreq;
1027         while (!list_empty(&hdr->pages)) {
1028                 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
1029 
1030                 nfs_list_remove_request(req);
1031                 if (!nfs_pageio_add_request(desc, req))
1032                         nfs_list_add_request(req, &failed);
1033         }
1034         nfs_pageio_complete(desc);
1035         if (!list_empty(&failed)) {
1036                 list_move(&failed, &hdr->pages);
1037                 return -EIO;
1038         }
1039         return 0;
1040 }
1041 EXPORT_SYMBOL_GPL(nfs_pageio_resend);
1042 
1043 /**
1044  * nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor
1045  * @desc: pointer to io descriptor
1046  */
1047 void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
1048 {
1049         for (;;) {
1050                 nfs_pageio_doio(desc);
1051                 if (!desc->pg_recoalesce)
1052                         break;
1053                 if (!nfs_do_recoalesce(desc))
1054                         break;
1055         }
1056 }
1057 
1058 /**
1059  * nfs_pageio_cond_complete - Conditional I/O completion
1060  * @desc: pointer to io descriptor
1061  * @index: page index
1062  *
1063  * It is important to ensure that processes don't try to take locks
1064  * on non-contiguous ranges of pages as that might deadlock. This
1065  * function should be called before attempting to wait on a locked
1066  * nfs_page. It will complete the I/O if the page index 'index'
1067  * is not contiguous with the existing list of pages in 'desc'.
1068  */
1069 void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index)
1070 {
1071         if (!list_empty(&desc->pg_list)) {
1072                 struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev);
1073                 if (index != prev->wb_index + 1)
1074                         nfs_pageio_complete(desc);
1075         }
1076 }
1077 
1078 int __init nfs_init_nfspagecache(void)
1079 {
1080         nfs_page_cachep = kmem_cache_create("nfs_page",
1081                                             sizeof(struct nfs_page),
1082                                             0, SLAB_HWCACHE_ALIGN,
1083                                             NULL);
1084         if (nfs_page_cachep == NULL)
1085                 return -ENOMEM;
1086 
1087         return 0;
1088 }
1089 
1090 void nfs_destroy_nfspagecache(void)
1091 {
1092         kmem_cache_destroy(nfs_page_cachep);
1093 }
1094 
1095 static const struct rpc_call_ops nfs_pgio_common_ops = {
1096         .rpc_call_prepare = nfs_pgio_prepare,
1097         .rpc_call_done = nfs_pgio_result,
1098         .rpc_release = nfs_pgio_release,
1099 };
1100 
1101 const struct nfs_pageio_ops nfs_pgio_rw_ops = {
1102         .pg_test = nfs_generic_pg_test,
1103         .pg_doio = nfs_generic_pg_pgios,
1104 };
1105 

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