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Linux/fs/nfs/pagelist.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  * linux/fs/nfs/pagelist.c
  4  *
  5  * A set of helper functions for managing NFS read and write requests.
  6  * The main purpose of these routines is to provide support for the
  7  * coalescing of several requests into a single RPC call.
  8  *
  9  * Copyright 2000, 2001 (c) Trond Myklebust <trond.myklebust@fys.uio.no>
 10  *
 11  */
 12 
 13 #include <linux/slab.h>
 14 #include <linux/file.h>
 15 #include <linux/sched.h>
 16 #include <linux/sunrpc/clnt.h>
 17 #include <linux/nfs.h>
 18 #include <linux/nfs3.h>
 19 #include <linux/nfs4.h>
 20 #include <linux/nfs_fs.h>
 21 #include <linux/nfs_page.h>
 22 #include <linux/nfs_mount.h>
 23 #include <linux/export.h>
 24 
 25 #include "internal.h"
 26 #include "pnfs.h"
 27 
 28 #define NFSDBG_FACILITY         NFSDBG_PAGECACHE
 29 
 30 static struct kmem_cache *nfs_page_cachep;
 31 static const struct rpc_call_ops nfs_pgio_common_ops;
 32 
 33 struct nfs_pgio_mirror *
 34 nfs_pgio_current_mirror(struct nfs_pageio_descriptor *desc)
 35 {
 36         return &desc->pg_mirrors[desc->pg_mirror_idx];
 37 }
 38 EXPORT_SYMBOL_GPL(nfs_pgio_current_mirror);
 39 
 40 void nfs_pgheader_init(struct nfs_pageio_descriptor *desc,
 41                        struct nfs_pgio_header *hdr,
 42                        void (*release)(struct nfs_pgio_header *hdr))
 43 {
 44         struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
 45 
 46 
 47         hdr->req = nfs_list_entry(mirror->pg_list.next);
 48         hdr->inode = desc->pg_inode;
 49         hdr->cred = nfs_req_openctx(hdr->req)->cred;
 50         hdr->io_start = req_offset(hdr->req);
 51         hdr->good_bytes = mirror->pg_count;
 52         hdr->io_completion = desc->pg_io_completion;
 53         hdr->dreq = desc->pg_dreq;
 54         hdr->release = release;
 55         hdr->completion_ops = desc->pg_completion_ops;
 56         if (hdr->completion_ops->init_hdr)
 57                 hdr->completion_ops->init_hdr(hdr);
 58 
 59         hdr->pgio_mirror_idx = desc->pg_mirror_idx;
 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         unsigned int new = pos - hdr->io_start;
 66 
 67         if (hdr->good_bytes > new) {
 68                 hdr->good_bytes = new;
 69                 clear_bit(NFS_IOHDR_EOF, &hdr->flags);
 70                 if (!test_and_set_bit(NFS_IOHDR_ERROR, &hdr->flags))
 71                         hdr->error = error;
 72         }
 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_KERNEL);
 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 /**
 91  * nfs_iocounter_wait - wait for i/o to complete
 92  * @l_ctx: nfs_lock_context with io_counter to use
 93  *
 94  * returns -ERESTARTSYS if interrupted by a fatal signal.
 95  * Otherwise returns 0 once the io_count hits 0.
 96  */
 97 int
 98 nfs_iocounter_wait(struct nfs_lock_context *l_ctx)
 99 {
100         return wait_var_event_killable(&l_ctx->io_count,
101                                        !atomic_read(&l_ctx->io_count));
102 }
103 
104 /**
105  * nfs_async_iocounter_wait - wait on a rpc_waitqueue for I/O
106  * to complete
107  * @task: the rpc_task that should wait
108  * @l_ctx: nfs_lock_context with io_counter to check
109  *
110  * Returns true if there is outstanding I/O to wait on and the
111  * task has been put to sleep.
112  */
113 bool
114 nfs_async_iocounter_wait(struct rpc_task *task, struct nfs_lock_context *l_ctx)
115 {
116         struct inode *inode = d_inode(l_ctx->open_context->dentry);
117         bool ret = false;
118 
119         if (atomic_read(&l_ctx->io_count) > 0) {
120                 rpc_sleep_on(&NFS_SERVER(inode)->uoc_rpcwaitq, task, NULL);
121                 ret = true;
122         }
123 
124         if (atomic_read(&l_ctx->io_count) == 0) {
125                 rpc_wake_up_queued_task(&NFS_SERVER(inode)->uoc_rpcwaitq, task);
126                 ret = false;
127         }
128 
129         return ret;
130 }
131 EXPORT_SYMBOL_GPL(nfs_async_iocounter_wait);
132 
133 /*
134  * nfs_page_lock_head_request - page lock the head of the page group
135  * @req: any member of the page group
136  */
137 struct nfs_page *
138 nfs_page_group_lock_head(struct nfs_page *req)
139 {
140         struct nfs_page *head = req->wb_head;
141 
142         while (!nfs_lock_request(head)) {
143                 int ret = nfs_wait_on_request(head);
144                 if (ret < 0)
145                         return ERR_PTR(ret);
146         }
147         if (head != req)
148                 kref_get(&head->wb_kref);
149         return head;
150 }
151 
152 /*
153  * nfs_unroll_locks -  unlock all newly locked reqs and wait on @req
154  * @head: head request of page group, must be holding head lock
155  * @req: request that couldn't lock and needs to wait on the req bit lock
156  *
157  * This is a helper function for nfs_lock_and_join_requests
158  * returns 0 on success, < 0 on error.
159  */
160 static void
161 nfs_unroll_locks(struct nfs_page *head, struct nfs_page *req)
162 {
163         struct nfs_page *tmp;
164 
165         /* relinquish all the locks successfully grabbed this run */
166         for (tmp = head->wb_this_page ; tmp != req; tmp = tmp->wb_this_page) {
167                 if (!kref_read(&tmp->wb_kref))
168                         continue;
169                 nfs_unlock_and_release_request(tmp);
170         }
171 }
172 
173 /*
174  * nfs_page_group_lock_subreq -  try to lock a subrequest
175  * @head: head request of page group
176  * @subreq: request to lock
177  *
178  * This is a helper function for nfs_lock_and_join_requests which
179  * must be called with the head request and page group both locked.
180  * On error, it returns with the page group unlocked.
181  */
182 static int
183 nfs_page_group_lock_subreq(struct nfs_page *head, struct nfs_page *subreq)
184 {
185         int ret;
186 
187         if (!kref_get_unless_zero(&subreq->wb_kref))
188                 return 0;
189         while (!nfs_lock_request(subreq)) {
190                 nfs_page_group_unlock(head);
191                 ret = nfs_wait_on_request(subreq);
192                 if (!ret)
193                         ret = nfs_page_group_lock(head);
194                 if (ret < 0) {
195                         nfs_unroll_locks(head, subreq);
196                         nfs_release_request(subreq);
197                         return ret;
198                 }
199         }
200         return 0;
201 }
202 
203 /*
204  * nfs_page_group_lock_subrequests -  try to lock the subrequests
205  * @head: head request of page group
206  *
207  * This is a helper function for nfs_lock_and_join_requests which
208  * must be called with the head request locked.
209  */
210 int nfs_page_group_lock_subrequests(struct nfs_page *head)
211 {
212         struct nfs_page *subreq;
213         int ret;
214 
215         ret = nfs_page_group_lock(head);
216         if (ret < 0)
217                 return ret;
218         /* lock each request in the page group */
219         for (subreq = head->wb_this_page; subreq != head;
220                         subreq = subreq->wb_this_page) {
221                 ret = nfs_page_group_lock_subreq(head, subreq);
222                 if (ret < 0)
223                         return ret;
224         }
225         nfs_page_group_unlock(head);
226         return 0;
227 }
228 
229 /*
230  * nfs_page_set_headlock - set the request PG_HEADLOCK
231  * @req: request that is to be locked
232  *
233  * this lock must be held when modifying req->wb_head
234  *
235  * return 0 on success, < 0 on error
236  */
237 int
238 nfs_page_set_headlock(struct nfs_page *req)
239 {
240         if (!test_and_set_bit(PG_HEADLOCK, &req->wb_flags))
241                 return 0;
242 
243         set_bit(PG_CONTENDED1, &req->wb_flags);
244         smp_mb__after_atomic();
245         return wait_on_bit_lock(&req->wb_flags, PG_HEADLOCK,
246                                 TASK_UNINTERRUPTIBLE);
247 }
248 
249 /*
250  * nfs_page_clear_headlock - clear the request PG_HEADLOCK
251  * @req: request that is to be locked
252  */
253 void
254 nfs_page_clear_headlock(struct nfs_page *req)
255 {
256         smp_mb__before_atomic();
257         clear_bit(PG_HEADLOCK, &req->wb_flags);
258         smp_mb__after_atomic();
259         if (!test_bit(PG_CONTENDED1, &req->wb_flags))
260                 return;
261         wake_up_bit(&req->wb_flags, PG_HEADLOCK);
262 }
263 
264 /*
265  * nfs_page_group_lock - lock the head of the page group
266  * @req: request in group that is to be locked
267  *
268  * this lock must be held when traversing or modifying the page
269  * group list
270  *
271  * return 0 on success, < 0 on error
272  */
273 int
274 nfs_page_group_lock(struct nfs_page *req)
275 {
276         int ret;
277 
278         ret = nfs_page_set_headlock(req);
279         if (ret || req->wb_head == req)
280                 return ret;
281         return nfs_page_set_headlock(req->wb_head);
282 }
283 
284 /*
285  * nfs_page_group_unlock - unlock the head of the page group
286  * @req: request in group that is to be unlocked
287  */
288 void
289 nfs_page_group_unlock(struct nfs_page *req)
290 {
291         if (req != req->wb_head)
292                 nfs_page_clear_headlock(req->wb_head);
293         nfs_page_clear_headlock(req);
294 }
295 
296 /*
297  * nfs_page_group_sync_on_bit_locked
298  *
299  * must be called with page group lock held
300  */
301 static bool
302 nfs_page_group_sync_on_bit_locked(struct nfs_page *req, unsigned int bit)
303 {
304         struct nfs_page *head = req->wb_head;
305         struct nfs_page *tmp;
306 
307         WARN_ON_ONCE(!test_bit(PG_HEADLOCK, &head->wb_flags));
308         WARN_ON_ONCE(test_and_set_bit(bit, &req->wb_flags));
309 
310         tmp = req->wb_this_page;
311         while (tmp != req) {
312                 if (!test_bit(bit, &tmp->wb_flags))
313                         return false;
314                 tmp = tmp->wb_this_page;
315         }
316 
317         /* true! reset all bits */
318         tmp = req;
319         do {
320                 clear_bit(bit, &tmp->wb_flags);
321                 tmp = tmp->wb_this_page;
322         } while (tmp != req);
323 
324         return true;
325 }
326 
327 /*
328  * nfs_page_group_sync_on_bit - set bit on current request, but only
329  *   return true if the bit is set for all requests in page group
330  * @req - request in page group
331  * @bit - PG_* bit that is used to sync page group
332  */
333 bool nfs_page_group_sync_on_bit(struct nfs_page *req, unsigned int bit)
334 {
335         bool ret;
336 
337         nfs_page_group_lock(req);
338         ret = nfs_page_group_sync_on_bit_locked(req, bit);
339         nfs_page_group_unlock(req);
340 
341         return ret;
342 }
343 
344 /*
345  * nfs_page_group_init - Initialize the page group linkage for @req
346  * @req - a new nfs request
347  * @prev - the previous request in page group, or NULL if @req is the first
348  *         or only request in the group (the head).
349  */
350 static inline void
351 nfs_page_group_init(struct nfs_page *req, struct nfs_page *prev)
352 {
353         struct inode *inode;
354         WARN_ON_ONCE(prev == req);
355 
356         if (!prev) {
357                 /* a head request */
358                 req->wb_head = req;
359                 req->wb_this_page = req;
360         } else {
361                 /* a subrequest */
362                 WARN_ON_ONCE(prev->wb_this_page != prev->wb_head);
363                 WARN_ON_ONCE(!test_bit(PG_HEADLOCK, &prev->wb_head->wb_flags));
364                 req->wb_head = prev->wb_head;
365                 req->wb_this_page = prev->wb_this_page;
366                 prev->wb_this_page = req;
367 
368                 /* All subrequests take a ref on the head request until
369                  * nfs_page_group_destroy is called */
370                 kref_get(&req->wb_head->wb_kref);
371 
372                 /* grab extra ref and bump the request count if head request
373                  * has extra ref from the write/commit path to handle handoff
374                  * between write and commit lists. */
375                 if (test_bit(PG_INODE_REF, &prev->wb_head->wb_flags)) {
376                         inode = page_file_mapping(req->wb_page)->host;
377                         set_bit(PG_INODE_REF, &req->wb_flags);
378                         kref_get(&req->wb_kref);
379                         atomic_long_inc(&NFS_I(inode)->nrequests);
380                 }
381         }
382 }
383 
384 /*
385  * nfs_page_group_destroy - sync the destruction of page groups
386  * @req - request that no longer needs the page group
387  *
388  * releases the page group reference from each member once all
389  * members have called this function.
390  */
391 static void
392 nfs_page_group_destroy(struct kref *kref)
393 {
394         struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref);
395         struct nfs_page *head = req->wb_head;
396         struct nfs_page *tmp, *next;
397 
398         if (!nfs_page_group_sync_on_bit(req, PG_TEARDOWN))
399                 goto out;
400 
401         tmp = req;
402         do {
403                 next = tmp->wb_this_page;
404                 /* unlink and free */
405                 tmp->wb_this_page = tmp;
406                 tmp->wb_head = tmp;
407                 nfs_free_request(tmp);
408                 tmp = next;
409         } while (tmp != req);
410 out:
411         /* subrequests must release the ref on the head request */
412         if (head != req)
413                 nfs_release_request(head);
414 }
415 
416 static struct nfs_page *
417 __nfs_create_request(struct nfs_lock_context *l_ctx, struct page *page,
418                    unsigned int pgbase, unsigned int offset,
419                    unsigned int count)
420 {
421         struct nfs_page         *req;
422         struct nfs_open_context *ctx = l_ctx->open_context;
423 
424         if (test_bit(NFS_CONTEXT_BAD, &ctx->flags))
425                 return ERR_PTR(-EBADF);
426         /* try to allocate the request struct */
427         req = nfs_page_alloc();
428         if (req == NULL)
429                 return ERR_PTR(-ENOMEM);
430 
431         req->wb_lock_context = l_ctx;
432         refcount_inc(&l_ctx->count);
433         atomic_inc(&l_ctx->io_count);
434 
435         /* Initialize the request struct. Initially, we assume a
436          * long write-back delay. This will be adjusted in
437          * update_nfs_request below if the region is not locked. */
438         req->wb_page    = page;
439         if (page) {
440                 req->wb_index = page_index(page);
441                 get_page(page);
442         }
443         req->wb_offset  = offset;
444         req->wb_pgbase  = pgbase;
445         req->wb_bytes   = count;
446         kref_init(&req->wb_kref);
447         req->wb_nio = 0;
448         return req;
449 }
450 
451 /**
452  * nfs_create_request - Create an NFS read/write request.
453  * @ctx: open context to use
454  * @page: page to write
455  * @offset: starting offset within the page for the write
456  * @count: number of bytes to read/write
457  *
458  * The page must be locked by the caller. This makes sure we never
459  * create two different requests for the same page.
460  * User should ensure it is safe to sleep in this function.
461  */
462 struct nfs_page *
463 nfs_create_request(struct nfs_open_context *ctx, struct page *page,
464                    unsigned int offset, unsigned int count)
465 {
466         struct nfs_lock_context *l_ctx = nfs_get_lock_context(ctx);
467         struct nfs_page *ret;
468 
469         if (IS_ERR(l_ctx))
470                 return ERR_CAST(l_ctx);
471         ret = __nfs_create_request(l_ctx, page, offset, offset, count);
472         if (!IS_ERR(ret))
473                 nfs_page_group_init(ret, NULL);
474         nfs_put_lock_context(l_ctx);
475         return ret;
476 }
477 
478 static struct nfs_page *
479 nfs_create_subreq(struct nfs_page *req,
480                   unsigned int pgbase,
481                   unsigned int offset,
482                   unsigned int count)
483 {
484         struct nfs_page *last;
485         struct nfs_page *ret;
486 
487         ret = __nfs_create_request(req->wb_lock_context, req->wb_page,
488                         pgbase, offset, count);
489         if (!IS_ERR(ret)) {
490                 /* find the last request */
491                 for (last = req->wb_head;
492                      last->wb_this_page != req->wb_head;
493                      last = last->wb_this_page)
494                         ;
495 
496                 nfs_lock_request(ret);
497                 ret->wb_index = req->wb_index;
498                 nfs_page_group_init(ret, last);
499                 ret->wb_nio = req->wb_nio;
500         }
501         return ret;
502 }
503 
504 /**
505  * nfs_unlock_request - Unlock request and wake up sleepers.
506  * @req: pointer to request
507  */
508 void nfs_unlock_request(struct nfs_page *req)
509 {
510         if (!NFS_WBACK_BUSY(req)) {
511                 printk(KERN_ERR "NFS: Invalid unlock attempted\n");
512                 BUG();
513         }
514         smp_mb__before_atomic();
515         clear_bit(PG_BUSY, &req->wb_flags);
516         smp_mb__after_atomic();
517         if (!test_bit(PG_CONTENDED2, &req->wb_flags))
518                 return;
519         wake_up_bit(&req->wb_flags, PG_BUSY);
520 }
521 
522 /**
523  * nfs_unlock_and_release_request - Unlock request and release the nfs_page
524  * @req: pointer to request
525  */
526 void nfs_unlock_and_release_request(struct nfs_page *req)
527 {
528         nfs_unlock_request(req);
529         nfs_release_request(req);
530 }
531 
532 /*
533  * nfs_clear_request - Free up all resources allocated to the request
534  * @req:
535  *
536  * Release page and open context resources associated with a read/write
537  * request after it has completed.
538  */
539 static void nfs_clear_request(struct nfs_page *req)
540 {
541         struct page *page = req->wb_page;
542         struct nfs_lock_context *l_ctx = req->wb_lock_context;
543         struct nfs_open_context *ctx;
544 
545         if (page != NULL) {
546                 put_page(page);
547                 req->wb_page = NULL;
548         }
549         if (l_ctx != NULL) {
550                 if (atomic_dec_and_test(&l_ctx->io_count)) {
551                         wake_up_var(&l_ctx->io_count);
552                         ctx = l_ctx->open_context;
553                         if (test_bit(NFS_CONTEXT_UNLOCK, &ctx->flags))
554                                 rpc_wake_up(&NFS_SERVER(d_inode(ctx->dentry))->uoc_rpcwaitq);
555                 }
556                 nfs_put_lock_context(l_ctx);
557                 req->wb_lock_context = NULL;
558         }
559 }
560 
561 /**
562  * nfs_release_request - Release the count on an NFS read/write request
563  * @req: request to release
564  *
565  * Note: Should never be called with the spinlock held!
566  */
567 void nfs_free_request(struct nfs_page *req)
568 {
569         WARN_ON_ONCE(req->wb_this_page != req);
570 
571         /* extra debug: make sure no sync bits are still set */
572         WARN_ON_ONCE(test_bit(PG_TEARDOWN, &req->wb_flags));
573         WARN_ON_ONCE(test_bit(PG_UNLOCKPAGE, &req->wb_flags));
574         WARN_ON_ONCE(test_bit(PG_UPTODATE, &req->wb_flags));
575         WARN_ON_ONCE(test_bit(PG_WB_END, &req->wb_flags));
576         WARN_ON_ONCE(test_bit(PG_REMOVE, &req->wb_flags));
577 
578         /* Release struct file and open context */
579         nfs_clear_request(req);
580         nfs_page_free(req);
581 }
582 
583 void nfs_release_request(struct nfs_page *req)
584 {
585         kref_put(&req->wb_kref, nfs_page_group_destroy);
586 }
587 EXPORT_SYMBOL_GPL(nfs_release_request);
588 
589 /**
590  * nfs_wait_on_request - Wait for a request to complete.
591  * @req: request to wait upon.
592  *
593  * Interruptible by fatal signals only.
594  * The user is responsible for holding a count on the request.
595  */
596 int
597 nfs_wait_on_request(struct nfs_page *req)
598 {
599         if (!test_bit(PG_BUSY, &req->wb_flags))
600                 return 0;
601         set_bit(PG_CONTENDED2, &req->wb_flags);
602         smp_mb__after_atomic();
603         return wait_on_bit_io(&req->wb_flags, PG_BUSY,
604                               TASK_UNINTERRUPTIBLE);
605 }
606 EXPORT_SYMBOL_GPL(nfs_wait_on_request);
607 
608 /*
609  * nfs_generic_pg_test - determine if requests can be coalesced
610  * @desc: pointer to descriptor
611  * @prev: previous request in desc, or NULL
612  * @req: this request
613  *
614  * Returns zero if @req cannot be coalesced into @desc, otherwise it returns
615  * the size of the request.
616  */
617 size_t nfs_generic_pg_test(struct nfs_pageio_descriptor *desc,
618                            struct nfs_page *prev, struct nfs_page *req)
619 {
620         struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
621 
622 
623         if (mirror->pg_count > mirror->pg_bsize) {
624                 /* should never happen */
625                 WARN_ON_ONCE(1);
626                 return 0;
627         }
628 
629         /*
630          * Limit the request size so that we can still allocate a page array
631          * for it without upsetting the slab allocator.
632          */
633         if (((mirror->pg_count + req->wb_bytes) >> PAGE_SHIFT) *
634                         sizeof(struct page *) > PAGE_SIZE)
635                 return 0;
636 
637         return min(mirror->pg_bsize - mirror->pg_count, (size_t)req->wb_bytes);
638 }
639 EXPORT_SYMBOL_GPL(nfs_generic_pg_test);
640 
641 struct nfs_pgio_header *nfs_pgio_header_alloc(const struct nfs_rw_ops *ops)
642 {
643         struct nfs_pgio_header *hdr = ops->rw_alloc_header();
644 
645         if (hdr) {
646                 INIT_LIST_HEAD(&hdr->pages);
647                 hdr->rw_ops = ops;
648         }
649         return hdr;
650 }
651 EXPORT_SYMBOL_GPL(nfs_pgio_header_alloc);
652 
653 /**
654  * nfs_pgio_data_destroy - make @hdr suitable for reuse
655  *
656  * Frees memory and releases refs from nfs_generic_pgio, so that it may
657  * be called again.
658  *
659  * @hdr: A header that has had nfs_generic_pgio called
660  */
661 static void nfs_pgio_data_destroy(struct nfs_pgio_header *hdr)
662 {
663         if (hdr->args.context)
664                 put_nfs_open_context(hdr->args.context);
665         if (hdr->page_array.pagevec != hdr->page_array.page_array)
666                 kfree(hdr->page_array.pagevec);
667 }
668 
669 /*
670  * nfs_pgio_header_free - Free a read or write header
671  * @hdr: The header to free
672  */
673 void nfs_pgio_header_free(struct nfs_pgio_header *hdr)
674 {
675         nfs_pgio_data_destroy(hdr);
676         hdr->rw_ops->rw_free_header(hdr);
677 }
678 EXPORT_SYMBOL_GPL(nfs_pgio_header_free);
679 
680 /**
681  * nfs_pgio_rpcsetup - Set up arguments for a pageio call
682  * @hdr: The pageio hdr
683  * @count: Number of bytes to read
684  * @how: How to commit data (writes only)
685  * @cinfo: Commit information for the call (writes only)
686  */
687 static void nfs_pgio_rpcsetup(struct nfs_pgio_header *hdr,
688                               unsigned int count,
689                               int how, struct nfs_commit_info *cinfo)
690 {
691         struct nfs_page *req = hdr->req;
692 
693         /* Set up the RPC argument and reply structs
694          * NB: take care not to mess about with hdr->commit et al. */
695 
696         hdr->args.fh     = NFS_FH(hdr->inode);
697         hdr->args.offset = req_offset(req);
698         /* pnfs_set_layoutcommit needs this */
699         hdr->mds_offset = hdr->args.offset;
700         hdr->args.pgbase = req->wb_pgbase;
701         hdr->args.pages  = hdr->page_array.pagevec;
702         hdr->args.count  = count;
703         hdr->args.context = get_nfs_open_context(nfs_req_openctx(req));
704         hdr->args.lock_context = req->wb_lock_context;
705         hdr->args.stable  = NFS_UNSTABLE;
706         switch (how & (FLUSH_STABLE | FLUSH_COND_STABLE)) {
707         case 0:
708                 break;
709         case FLUSH_COND_STABLE:
710                 if (nfs_reqs_to_commit(cinfo))
711                         break;
712                 /* fall through */
713         default:
714                 hdr->args.stable = NFS_FILE_SYNC;
715         }
716 
717         hdr->res.fattr   = &hdr->fattr;
718         hdr->res.count   = 0;
719         hdr->res.eof     = 0;
720         hdr->res.verf    = &hdr->verf;
721         nfs_fattr_init(&hdr->fattr);
722 }
723 
724 /**
725  * nfs_pgio_prepare - Prepare pageio hdr to go over the wire
726  * @task: The current task
727  * @calldata: pageio header to prepare
728  */
729 static void nfs_pgio_prepare(struct rpc_task *task, void *calldata)
730 {
731         struct nfs_pgio_header *hdr = calldata;
732         int err;
733         err = NFS_PROTO(hdr->inode)->pgio_rpc_prepare(task, hdr);
734         if (err)
735                 rpc_exit(task, err);
736 }
737 
738 int nfs_initiate_pgio(struct rpc_clnt *clnt, struct nfs_pgio_header *hdr,
739                       const struct cred *cred, const struct nfs_rpc_ops *rpc_ops,
740                       const struct rpc_call_ops *call_ops, int how, int flags)
741 {
742         struct rpc_task *task;
743         struct rpc_message msg = {
744                 .rpc_argp = &hdr->args,
745                 .rpc_resp = &hdr->res,
746                 .rpc_cred = cred,
747         };
748         struct rpc_task_setup task_setup_data = {
749                 .rpc_client = clnt,
750                 .task = &hdr->task,
751                 .rpc_message = &msg,
752                 .callback_ops = call_ops,
753                 .callback_data = hdr,
754                 .workqueue = nfsiod_workqueue,
755                 .flags = RPC_TASK_ASYNC | flags,
756         };
757 
758         hdr->rw_ops->rw_initiate(hdr, &msg, rpc_ops, &task_setup_data, how);
759 
760         dprintk("NFS: initiated pgio call "
761                 "(req %s/%llu, %u bytes @ offset %llu)\n",
762                 hdr->inode->i_sb->s_id,
763                 (unsigned long long)NFS_FILEID(hdr->inode),
764                 hdr->args.count,
765                 (unsigned long long)hdr->args.offset);
766 
767         task = rpc_run_task(&task_setup_data);
768         if (IS_ERR(task))
769                 return PTR_ERR(task);
770         rpc_put_task(task);
771         return 0;
772 }
773 EXPORT_SYMBOL_GPL(nfs_initiate_pgio);
774 
775 /**
776  * nfs_pgio_error - Clean up from a pageio error
777  * @hdr: pageio header
778  */
779 static void nfs_pgio_error(struct nfs_pgio_header *hdr)
780 {
781         set_bit(NFS_IOHDR_REDO, &hdr->flags);
782         hdr->completion_ops->completion(hdr);
783 }
784 
785 /**
786  * nfs_pgio_release - Release pageio data
787  * @calldata: The pageio header to release
788  */
789 static void nfs_pgio_release(void *calldata)
790 {
791         struct nfs_pgio_header *hdr = calldata;
792         hdr->completion_ops->completion(hdr);
793 }
794 
795 static void nfs_pageio_mirror_init(struct nfs_pgio_mirror *mirror,
796                                    unsigned int bsize)
797 {
798         INIT_LIST_HEAD(&mirror->pg_list);
799         mirror->pg_bytes_written = 0;
800         mirror->pg_count = 0;
801         mirror->pg_bsize = bsize;
802         mirror->pg_base = 0;
803         mirror->pg_recoalesce = 0;
804 }
805 
806 /**
807  * nfs_pageio_init - initialise a page io descriptor
808  * @desc: pointer to descriptor
809  * @inode: pointer to inode
810  * @pg_ops: pointer to pageio operations
811  * @compl_ops: pointer to pageio completion operations
812  * @rw_ops: pointer to nfs read/write operations
813  * @bsize: io block size
814  * @io_flags: extra parameters for the io function
815  */
816 void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
817                      struct inode *inode,
818                      const struct nfs_pageio_ops *pg_ops,
819                      const struct nfs_pgio_completion_ops *compl_ops,
820                      const struct nfs_rw_ops *rw_ops,
821                      size_t bsize,
822                      int io_flags)
823 {
824         desc->pg_moreio = 0;
825         desc->pg_inode = inode;
826         desc->pg_ops = pg_ops;
827         desc->pg_completion_ops = compl_ops;
828         desc->pg_rw_ops = rw_ops;
829         desc->pg_ioflags = io_flags;
830         desc->pg_error = 0;
831         desc->pg_lseg = NULL;
832         desc->pg_io_completion = NULL;
833         desc->pg_dreq = NULL;
834         desc->pg_bsize = bsize;
835 
836         desc->pg_mirror_count = 1;
837         desc->pg_mirror_idx = 0;
838 
839         desc->pg_mirrors_dynamic = NULL;
840         desc->pg_mirrors = desc->pg_mirrors_static;
841         nfs_pageio_mirror_init(&desc->pg_mirrors[0], bsize);
842         desc->pg_maxretrans = 0;
843 }
844 
845 /**
846  * nfs_pgio_result - Basic pageio error handling
847  * @task: The task that ran
848  * @calldata: Pageio header to check
849  */
850 static void nfs_pgio_result(struct rpc_task *task, void *calldata)
851 {
852         struct nfs_pgio_header *hdr = calldata;
853         struct inode *inode = hdr->inode;
854 
855         dprintk("NFS: %s: %5u, (status %d)\n", __func__,
856                 task->tk_pid, task->tk_status);
857 
858         if (hdr->rw_ops->rw_done(task, hdr, inode) != 0)
859                 return;
860         if (task->tk_status < 0)
861                 nfs_set_pgio_error(hdr, task->tk_status, hdr->args.offset);
862         else
863                 hdr->rw_ops->rw_result(task, hdr);
864 }
865 
866 /*
867  * Create an RPC task for the given read or write request and kick it.
868  * The page must have been locked by the caller.
869  *
870  * It may happen that the page we're passed is not marked dirty.
871  * This is the case if nfs_updatepage detects a conflicting request
872  * that has been written but not committed.
873  */
874 int nfs_generic_pgio(struct nfs_pageio_descriptor *desc,
875                      struct nfs_pgio_header *hdr)
876 {
877         struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
878 
879         struct nfs_page         *req;
880         struct page             **pages,
881                                 *last_page;
882         struct list_head *head = &mirror->pg_list;
883         struct nfs_commit_info cinfo;
884         struct nfs_page_array *pg_array = &hdr->page_array;
885         unsigned int pagecount, pageused;
886         gfp_t gfp_flags = GFP_KERNEL;
887 
888         pagecount = nfs_page_array_len(mirror->pg_base, mirror->pg_count);
889         pg_array->npages = pagecount;
890 
891         if (pagecount <= ARRAY_SIZE(pg_array->page_array))
892                 pg_array->pagevec = pg_array->page_array;
893         else {
894                 pg_array->pagevec = kcalloc(pagecount, sizeof(struct page *), gfp_flags);
895                 if (!pg_array->pagevec) {
896                         pg_array->npages = 0;
897                         nfs_pgio_error(hdr);
898                         desc->pg_error = -ENOMEM;
899                         return desc->pg_error;
900                 }
901         }
902 
903         nfs_init_cinfo(&cinfo, desc->pg_inode, desc->pg_dreq);
904         pages = hdr->page_array.pagevec;
905         last_page = NULL;
906         pageused = 0;
907         while (!list_empty(head)) {
908                 req = nfs_list_entry(head->next);
909                 nfs_list_move_request(req, &hdr->pages);
910 
911                 if (!last_page || last_page != req->wb_page) {
912                         pageused++;
913                         if (pageused > pagecount)
914                                 break;
915                         *pages++ = last_page = req->wb_page;
916                 }
917         }
918         if (WARN_ON_ONCE(pageused != pagecount)) {
919                 nfs_pgio_error(hdr);
920                 desc->pg_error = -EINVAL;
921                 return desc->pg_error;
922         }
923 
924         if ((desc->pg_ioflags & FLUSH_COND_STABLE) &&
925             (desc->pg_moreio || nfs_reqs_to_commit(&cinfo)))
926                 desc->pg_ioflags &= ~FLUSH_COND_STABLE;
927 
928         /* Set up the argument struct */
929         nfs_pgio_rpcsetup(hdr, mirror->pg_count, desc->pg_ioflags, &cinfo);
930         desc->pg_rpc_callops = &nfs_pgio_common_ops;
931         return 0;
932 }
933 EXPORT_SYMBOL_GPL(nfs_generic_pgio);
934 
935 static int nfs_generic_pg_pgios(struct nfs_pageio_descriptor *desc)
936 {
937         struct nfs_pgio_header *hdr;
938         int ret;
939 
940         hdr = nfs_pgio_header_alloc(desc->pg_rw_ops);
941         if (!hdr) {
942                 desc->pg_error = -ENOMEM;
943                 return desc->pg_error;
944         }
945         nfs_pgheader_init(desc, hdr, nfs_pgio_header_free);
946         ret = nfs_generic_pgio(desc, hdr);
947         if (ret == 0)
948                 ret = nfs_initiate_pgio(NFS_CLIENT(hdr->inode),
949                                         hdr,
950                                         hdr->cred,
951                                         NFS_PROTO(hdr->inode),
952                                         desc->pg_rpc_callops,
953                                         desc->pg_ioflags,
954                                         RPC_TASK_CRED_NOREF);
955         return ret;
956 }
957 
958 static struct nfs_pgio_mirror *
959 nfs_pageio_alloc_mirrors(struct nfs_pageio_descriptor *desc,
960                 unsigned int mirror_count)
961 {
962         struct nfs_pgio_mirror *ret;
963         unsigned int i;
964 
965         kfree(desc->pg_mirrors_dynamic);
966         desc->pg_mirrors_dynamic = NULL;
967         if (mirror_count == 1)
968                 return desc->pg_mirrors_static;
969         ret = kmalloc_array(mirror_count, sizeof(*ret), GFP_KERNEL);
970         if (ret != NULL) {
971                 for (i = 0; i < mirror_count; i++)
972                         nfs_pageio_mirror_init(&ret[i], desc->pg_bsize);
973                 desc->pg_mirrors_dynamic = ret;
974         }
975         return ret;
976 }
977 
978 /*
979  * nfs_pageio_setup_mirroring - determine if mirroring is to be used
980  *                              by calling the pg_get_mirror_count op
981  */
982 static void nfs_pageio_setup_mirroring(struct nfs_pageio_descriptor *pgio,
983                                        struct nfs_page *req)
984 {
985         unsigned int mirror_count = 1;
986 
987         if (pgio->pg_ops->pg_get_mirror_count)
988                 mirror_count = pgio->pg_ops->pg_get_mirror_count(pgio, req);
989         if (mirror_count == pgio->pg_mirror_count || pgio->pg_error < 0)
990                 return;
991 
992         if (!mirror_count || mirror_count > NFS_PAGEIO_DESCRIPTOR_MIRROR_MAX) {
993                 pgio->pg_error = -EINVAL;
994                 return;
995         }
996 
997         pgio->pg_mirrors = nfs_pageio_alloc_mirrors(pgio, mirror_count);
998         if (pgio->pg_mirrors == NULL) {
999                 pgio->pg_error = -ENOMEM;
1000                 pgio->pg_mirrors = pgio->pg_mirrors_static;
1001                 mirror_count = 1;
1002         }
1003         pgio->pg_mirror_count = mirror_count;
1004 }
1005 
1006 static void nfs_pageio_cleanup_mirroring(struct nfs_pageio_descriptor *pgio)
1007 {
1008         pgio->pg_mirror_count = 1;
1009         pgio->pg_mirror_idx = 0;
1010         pgio->pg_mirrors = pgio->pg_mirrors_static;
1011         kfree(pgio->pg_mirrors_dynamic);
1012         pgio->pg_mirrors_dynamic = NULL;
1013 }
1014 
1015 static bool nfs_match_lock_context(const struct nfs_lock_context *l1,
1016                 const struct nfs_lock_context *l2)
1017 {
1018         return l1->lockowner == l2->lockowner;
1019 }
1020 
1021 /**
1022  * nfs_coalesce_size - test two requests for compatibility
1023  * @prev: pointer to nfs_page
1024  * @req: pointer to nfs_page
1025  * @pgio: pointer to nfs_pagio_descriptor
1026  *
1027  * The nfs_page structures 'prev' and 'req' are compared to ensure that the
1028  * page data area they describe is contiguous, and that their RPC
1029  * credentials, NFSv4 open state, and lockowners are the same.
1030  *
1031  * Returns size of the request that can be coalesced
1032  */
1033 static unsigned int nfs_coalesce_size(struct nfs_page *prev,
1034                                       struct nfs_page *req,
1035                                       struct nfs_pageio_descriptor *pgio)
1036 {
1037         struct file_lock_context *flctx;
1038 
1039         if (prev) {
1040                 if (!nfs_match_open_context(nfs_req_openctx(req), nfs_req_openctx(prev)))
1041                         return 0;
1042                 flctx = d_inode(nfs_req_openctx(req)->dentry)->i_flctx;
1043                 if (flctx != NULL &&
1044                     !(list_empty_careful(&flctx->flc_posix) &&
1045                       list_empty_careful(&flctx->flc_flock)) &&
1046                     !nfs_match_lock_context(req->wb_lock_context,
1047                                             prev->wb_lock_context))
1048                         return 0;
1049                 if (req_offset(req) != req_offset(prev) + prev->wb_bytes)
1050                         return 0;
1051                 if (req->wb_page == prev->wb_page) {
1052                         if (req->wb_pgbase != prev->wb_pgbase + prev->wb_bytes)
1053                                 return 0;
1054                 } else {
1055                         if (req->wb_pgbase != 0 ||
1056                             prev->wb_pgbase + prev->wb_bytes != PAGE_SIZE)
1057                                 return 0;
1058                 }
1059         }
1060         return pgio->pg_ops->pg_test(pgio, prev, req);
1061 }
1062 
1063 /**
1064  * nfs_pageio_do_add_request - Attempt to coalesce a request into a page list.
1065  * @desc: destination io descriptor
1066  * @req: request
1067  *
1068  * If the request 'req' was successfully coalesced into the existing list
1069  * of pages 'desc', it returns the size of req.
1070  */
1071 static unsigned int
1072 nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc,
1073                 struct nfs_page *req)
1074 {
1075         struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
1076         struct nfs_page *prev = NULL;
1077         unsigned int size;
1078 
1079         if (mirror->pg_count != 0) {
1080                 prev = nfs_list_entry(mirror->pg_list.prev);
1081         } else {
1082                 if (desc->pg_ops->pg_init)
1083                         desc->pg_ops->pg_init(desc, req);
1084                 if (desc->pg_error < 0)
1085                         return 0;
1086                 mirror->pg_base = req->wb_pgbase;
1087         }
1088 
1089         if (desc->pg_maxretrans && req->wb_nio > desc->pg_maxretrans) {
1090                 if (NFS_SERVER(desc->pg_inode)->flags & NFS_MOUNT_SOFTERR)
1091                         desc->pg_error = -ETIMEDOUT;
1092                 else
1093                         desc->pg_error = -EIO;
1094                 return 0;
1095         }
1096 
1097         size = nfs_coalesce_size(prev, req, desc);
1098         if (size < req->wb_bytes)
1099                 return size;
1100         nfs_list_move_request(req, &mirror->pg_list);
1101         mirror->pg_count += req->wb_bytes;
1102         return req->wb_bytes;
1103 }
1104 
1105 /*
1106  * Helper for nfs_pageio_add_request and nfs_pageio_complete
1107  */
1108 static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc)
1109 {
1110         struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
1111 
1112 
1113         if (!list_empty(&mirror->pg_list)) {
1114                 int error = desc->pg_ops->pg_doio(desc);
1115                 if (error < 0)
1116                         desc->pg_error = error;
1117                 else
1118                         mirror->pg_bytes_written += mirror->pg_count;
1119         }
1120         if (list_empty(&mirror->pg_list)) {
1121                 mirror->pg_count = 0;
1122                 mirror->pg_base = 0;
1123         }
1124 }
1125 
1126 static void
1127 nfs_pageio_cleanup_request(struct nfs_pageio_descriptor *desc,
1128                 struct nfs_page *req)
1129 {
1130         LIST_HEAD(head);
1131 
1132         nfs_list_move_request(req, &head);
1133         desc->pg_completion_ops->error_cleanup(&head, desc->pg_error);
1134 }
1135 
1136 /**
1137  * nfs_pageio_add_request - Attempt to coalesce a request into a page list.
1138  * @desc: destination io descriptor
1139  * @req: request
1140  *
1141  * This may split a request into subrequests which are all part of the
1142  * same page group. If so, it will submit @req as the last one, to ensure
1143  * the pointer to @req is still valid in case of failure.
1144  *
1145  * Returns true if the request 'req' was successfully coalesced into the
1146  * existing list of pages 'desc'.
1147  */
1148 static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
1149                            struct nfs_page *req)
1150 {
1151         struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
1152         struct nfs_page *subreq;
1153         unsigned int size, subreq_size;
1154 
1155         nfs_page_group_lock(req);
1156 
1157         subreq = req;
1158         subreq_size = subreq->wb_bytes;
1159         for(;;) {
1160                 size = nfs_pageio_do_add_request(desc, subreq);
1161                 if (size == subreq_size) {
1162                         /* We successfully submitted a request */
1163                         if (subreq == req)
1164                                 break;
1165                         req->wb_pgbase += size;
1166                         req->wb_bytes -= size;
1167                         req->wb_offset += size;
1168                         subreq_size = req->wb_bytes;
1169                         subreq = req;
1170                         continue;
1171                 }
1172                 if (WARN_ON_ONCE(subreq != req)) {
1173                         nfs_page_group_unlock(req);
1174                         nfs_pageio_cleanup_request(desc, subreq);
1175                         subreq = req;
1176                         subreq_size = req->wb_bytes;
1177                         nfs_page_group_lock(req);
1178                 }
1179                 if (!size) {
1180                         /* Can't coalesce any more, so do I/O */
1181                         nfs_page_group_unlock(req);
1182                         desc->pg_moreio = 1;
1183                         nfs_pageio_doio(desc);
1184                         if (desc->pg_error < 0 || mirror->pg_recoalesce)
1185                                 return 0;
1186                         /* retry add_request for this subreq */
1187                         nfs_page_group_lock(req);
1188                         continue;
1189                 }
1190                 subreq = nfs_create_subreq(req, req->wb_pgbase,
1191                                 req->wb_offset, size);
1192                 if (IS_ERR(subreq))
1193                         goto err_ptr;
1194                 subreq_size = size;
1195         }
1196 
1197         nfs_page_group_unlock(req);
1198         return 1;
1199 err_ptr:
1200         desc->pg_error = PTR_ERR(subreq);
1201         nfs_page_group_unlock(req);
1202         return 0;
1203 }
1204 
1205 static int nfs_do_recoalesce(struct nfs_pageio_descriptor *desc)
1206 {
1207         struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
1208         LIST_HEAD(head);
1209 
1210         do {
1211                 list_splice_init(&mirror->pg_list, &head);
1212                 mirror->pg_bytes_written -= mirror->pg_count;
1213                 mirror->pg_count = 0;
1214                 mirror->pg_base = 0;
1215                 mirror->pg_recoalesce = 0;
1216 
1217                 while (!list_empty(&head)) {
1218                         struct nfs_page *req;
1219 
1220                         req = list_first_entry(&head, struct nfs_page, wb_list);
1221                         if (__nfs_pageio_add_request(desc, req))
1222                                 continue;
1223                         if (desc->pg_error < 0) {
1224                                 list_splice_tail(&head, &mirror->pg_list);
1225                                 mirror->pg_recoalesce = 1;
1226                                 return 0;
1227                         }
1228                         break;
1229                 }
1230         } while (mirror->pg_recoalesce);
1231         return 1;
1232 }
1233 
1234 static int nfs_pageio_add_request_mirror(struct nfs_pageio_descriptor *desc,
1235                 struct nfs_page *req)
1236 {
1237         int ret;
1238 
1239         do {
1240                 ret = __nfs_pageio_add_request(desc, req);
1241                 if (ret)
1242                         break;
1243                 if (desc->pg_error < 0)
1244                         break;
1245                 ret = nfs_do_recoalesce(desc);
1246         } while (ret);
1247 
1248         return ret;
1249 }
1250 
1251 static void nfs_pageio_error_cleanup(struct nfs_pageio_descriptor *desc)
1252 {
1253         u32 midx;
1254         struct nfs_pgio_mirror *mirror;
1255 
1256         if (!desc->pg_error)
1257                 return;
1258 
1259         for (midx = 0; midx < desc->pg_mirror_count; midx++) {
1260                 mirror = &desc->pg_mirrors[midx];
1261                 desc->pg_completion_ops->error_cleanup(&mirror->pg_list,
1262                                 desc->pg_error);
1263         }
1264 }
1265 
1266 int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
1267                            struct nfs_page *req)
1268 {
1269         u32 midx;
1270         unsigned int pgbase, offset, bytes;
1271         struct nfs_page *dupreq;
1272 
1273         pgbase = req->wb_pgbase;
1274         offset = req->wb_offset;
1275         bytes = req->wb_bytes;
1276 
1277         nfs_pageio_setup_mirroring(desc, req);
1278         if (desc->pg_error < 0)
1279                 goto out_failed;
1280 
1281         /* Create the mirror instances first, and fire them off */
1282         for (midx = 1; midx < desc->pg_mirror_count; midx++) {
1283                 nfs_page_group_lock(req);
1284 
1285                 dupreq = nfs_create_subreq(req,
1286                                 pgbase, offset, bytes);
1287 
1288                 nfs_page_group_unlock(req);
1289                 if (IS_ERR(dupreq)) {
1290                         desc->pg_error = PTR_ERR(dupreq);
1291                         goto out_failed;
1292                 }
1293 
1294                 desc->pg_mirror_idx = midx;
1295                 if (!nfs_pageio_add_request_mirror(desc, dupreq))
1296                         goto out_cleanup_subreq;
1297         }
1298 
1299         desc->pg_mirror_idx = 0;
1300         if (!nfs_pageio_add_request_mirror(desc, req))
1301                 goto out_failed;
1302 
1303         return 1;
1304 
1305 out_cleanup_subreq:
1306         nfs_pageio_cleanup_request(desc, dupreq);
1307 out_failed:
1308         nfs_pageio_error_cleanup(desc);
1309         return 0;
1310 }
1311 
1312 /*
1313  * nfs_pageio_complete_mirror - Complete I/O on the current mirror of an
1314  *                              nfs_pageio_descriptor
1315  * @desc: pointer to io descriptor
1316  * @mirror_idx: pointer to mirror index
1317  */
1318 static void nfs_pageio_complete_mirror(struct nfs_pageio_descriptor *desc,
1319                                        u32 mirror_idx)
1320 {
1321         struct nfs_pgio_mirror *mirror = &desc->pg_mirrors[mirror_idx];
1322         u32 restore_idx = desc->pg_mirror_idx;
1323 
1324         desc->pg_mirror_idx = mirror_idx;
1325         for (;;) {
1326                 nfs_pageio_doio(desc);
1327                 if (desc->pg_error < 0 || !mirror->pg_recoalesce)
1328                         break;
1329                 if (!nfs_do_recoalesce(desc))
1330                         break;
1331         }
1332         desc->pg_mirror_idx = restore_idx;
1333 }
1334 
1335 /*
1336  * nfs_pageio_resend - Transfer requests to new descriptor and resend
1337  * @hdr - the pgio header to move request from
1338  * @desc - the pageio descriptor to add requests to
1339  *
1340  * Try to move each request (nfs_page) from @hdr to @desc then attempt
1341  * to send them.
1342  *
1343  * Returns 0 on success and < 0 on error.
1344  */
1345 int nfs_pageio_resend(struct nfs_pageio_descriptor *desc,
1346                       struct nfs_pgio_header *hdr)
1347 {
1348         LIST_HEAD(pages);
1349 
1350         desc->pg_io_completion = hdr->io_completion;
1351         desc->pg_dreq = hdr->dreq;
1352         list_splice_init(&hdr->pages, &pages);
1353         while (!list_empty(&pages)) {
1354                 struct nfs_page *req = nfs_list_entry(pages.next);
1355 
1356                 if (!nfs_pageio_add_request(desc, req))
1357                         break;
1358         }
1359         nfs_pageio_complete(desc);
1360         if (!list_empty(&pages)) {
1361                 int err = desc->pg_error < 0 ? desc->pg_error : -EIO;
1362                 hdr->completion_ops->error_cleanup(&pages, err);
1363                 nfs_set_pgio_error(hdr, err, hdr->io_start);
1364                 return err;
1365         }
1366         return 0;
1367 }
1368 EXPORT_SYMBOL_GPL(nfs_pageio_resend);
1369 
1370 /**
1371  * nfs_pageio_complete - Complete I/O then cleanup an nfs_pageio_descriptor
1372  * @desc: pointer to io descriptor
1373  */
1374 void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
1375 {
1376         u32 midx;
1377 
1378         for (midx = 0; midx < desc->pg_mirror_count; midx++)
1379                 nfs_pageio_complete_mirror(desc, midx);
1380 
1381         if (desc->pg_error < 0)
1382                 nfs_pageio_error_cleanup(desc);
1383         if (desc->pg_ops->pg_cleanup)
1384                 desc->pg_ops->pg_cleanup(desc);
1385         nfs_pageio_cleanup_mirroring(desc);
1386 }
1387 
1388 /**
1389  * nfs_pageio_cond_complete - Conditional I/O completion
1390  * @desc: pointer to io descriptor
1391  * @index: page index
1392  *
1393  * It is important to ensure that processes don't try to take locks
1394  * on non-contiguous ranges of pages as that might deadlock. This
1395  * function should be called before attempting to wait on a locked
1396  * nfs_page. It will complete the I/O if the page index 'index'
1397  * is not contiguous with the existing list of pages in 'desc'.
1398  */
1399 void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index)
1400 {
1401         struct nfs_pgio_mirror *mirror;
1402         struct nfs_page *prev;
1403         u32 midx;
1404 
1405         for (midx = 0; midx < desc->pg_mirror_count; midx++) {
1406                 mirror = &desc->pg_mirrors[midx];
1407                 if (!list_empty(&mirror->pg_list)) {
1408                         prev = nfs_list_entry(mirror->pg_list.prev);
1409                         if (index != prev->wb_index + 1) {
1410                                 nfs_pageio_complete(desc);
1411                                 break;
1412                         }
1413                 }
1414         }
1415 }
1416 
1417 /*
1418  * nfs_pageio_stop_mirroring - stop using mirroring (set mirror count to 1)
1419  */
1420 void nfs_pageio_stop_mirroring(struct nfs_pageio_descriptor *pgio)
1421 {
1422         nfs_pageio_complete(pgio);
1423 }
1424 
1425 int __init nfs_init_nfspagecache(void)
1426 {
1427         nfs_page_cachep = kmem_cache_create("nfs_page",
1428                                             sizeof(struct nfs_page),
1429                                             0, SLAB_HWCACHE_ALIGN,
1430                                             NULL);
1431         if (nfs_page_cachep == NULL)
1432                 return -ENOMEM;
1433 
1434         return 0;
1435 }
1436 
1437 void nfs_destroy_nfspagecache(void)
1438 {
1439         kmem_cache_destroy(nfs_page_cachep);
1440 }
1441 
1442 static const struct rpc_call_ops nfs_pgio_common_ops = {
1443         .rpc_call_prepare = nfs_pgio_prepare,
1444         .rpc_call_done = nfs_pgio_result,
1445         .rpc_release = nfs_pgio_release,
1446 };
1447 
1448 const struct nfs_pageio_ops nfs_pgio_rw_ops = {
1449         .pg_test = nfs_generic_pg_test,
1450         .pg_doio = nfs_generic_pg_pgios,
1451 };
1452 

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