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TOMOYO Linux Cross Reference
Linux/fs/nfs/write.c

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  1 /*
  2  * linux/fs/nfs/write.c
  3  *
  4  * Write file data over NFS.
  5  *
  6  * Copyright (C) 1996, 1997, Olaf Kirch <okir@monad.swb.de>
  7  */
  8 
  9 #include <linux/types.h>
 10 #include <linux/slab.h>
 11 #include <linux/mm.h>
 12 #include <linux/pagemap.h>
 13 #include <linux/file.h>
 14 #include <linux/writeback.h>
 15 #include <linux/swap.h>
 16 #include <linux/migrate.h>
 17 
 18 #include <linux/sunrpc/clnt.h>
 19 #include <linux/nfs_fs.h>
 20 #include <linux/nfs_mount.h>
 21 #include <linux/nfs_page.h>
 22 #include <linux/backing-dev.h>
 23 
 24 #include <asm/uaccess.h>
 25 
 26 #include "delegation.h"
 27 #include "internal.h"
 28 #include "iostat.h"
 29 #include "nfs4_fs.h"
 30 #include "fscache.h"
 31 
 32 #define NFSDBG_FACILITY         NFSDBG_PAGECACHE
 33 
 34 #define MIN_POOL_WRITE          (32)
 35 #define MIN_POOL_COMMIT         (4)
 36 
 37 /*
 38  * Local function declarations
 39  */
 40 static void nfs_pageio_init_write(struct nfs_pageio_descriptor *desc,
 41                                   struct inode *inode, int ioflags);
 42 static void nfs_redirty_request(struct nfs_page *req);
 43 static const struct rpc_call_ops nfs_write_partial_ops;
 44 static const struct rpc_call_ops nfs_write_full_ops;
 45 static const struct rpc_call_ops nfs_commit_ops;
 46 
 47 static struct kmem_cache *nfs_wdata_cachep;
 48 static mempool_t *nfs_wdata_mempool;
 49 static mempool_t *nfs_commit_mempool;
 50 
 51 struct nfs_write_data *nfs_commitdata_alloc(void)
 52 {
 53         struct nfs_write_data *p = mempool_alloc(nfs_commit_mempool, GFP_NOFS);
 54 
 55         if (p) {
 56                 memset(p, 0, sizeof(*p));
 57                 INIT_LIST_HEAD(&p->pages);
 58                 p->res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 59         }
 60         return p;
 61 }
 62 
 63 void nfs_commit_free(struct nfs_write_data *p)
 64 {
 65         if (p && (p->pagevec != &p->page_array[0]))
 66                 kfree(p->pagevec);
 67         mempool_free(p, nfs_commit_mempool);
 68 }
 69 
 70 struct nfs_write_data *nfs_writedata_alloc(unsigned int pagecount)
 71 {
 72         struct nfs_write_data *p = mempool_alloc(nfs_wdata_mempool, GFP_NOFS);
 73 
 74         if (p) {
 75                 memset(p, 0, sizeof(*p));
 76                 INIT_LIST_HEAD(&p->pages);
 77                 p->npages = pagecount;
 78                 p->res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 79                 if (pagecount <= ARRAY_SIZE(p->page_array))
 80                         p->pagevec = p->page_array;
 81                 else {
 82                         p->pagevec = kcalloc(pagecount, sizeof(struct page *), GFP_NOFS);
 83                         if (!p->pagevec) {
 84                                 mempool_free(p, nfs_wdata_mempool);
 85                                 p = NULL;
 86                         }
 87                 }
 88         }
 89         return p;
 90 }
 91 
 92 void nfs_writedata_free(struct nfs_write_data *p)
 93 {
 94         if (p && (p->pagevec != &p->page_array[0]))
 95                 kfree(p->pagevec);
 96         mempool_free(p, nfs_wdata_mempool);
 97 }
 98 
 99 static void nfs_writedata_release(struct nfs_write_data *wdata)
100 {
101         put_nfs_open_context(wdata->args.context);
102         nfs_writedata_free(wdata);
103 }
104 
105 static void nfs_context_set_write_error(struct nfs_open_context *ctx, int error)
106 {
107         ctx->error = error;
108         smp_wmb();
109         set_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags);
110 }
111 
112 static struct nfs_page *nfs_page_find_request_locked(struct page *page)
113 {
114         struct nfs_page *req = NULL;
115 
116         if (PagePrivate(page)) {
117                 req = (struct nfs_page *)page_private(page);
118                 if (req != NULL)
119                         kref_get(&req->wb_kref);
120         }
121         return req;
122 }
123 
124 static struct nfs_page *nfs_page_find_request(struct page *page)
125 {
126         struct inode *inode = page->mapping->host;
127         struct nfs_page *req = NULL;
128 
129         spin_lock(&inode->i_lock);
130         req = nfs_page_find_request_locked(page);
131         spin_unlock(&inode->i_lock);
132         return req;
133 }
134 
135 /* Adjust the file length if we're writing beyond the end */
136 static void nfs_grow_file(struct page *page, unsigned int offset, unsigned int count)
137 {
138         struct inode *inode = page->mapping->host;
139         loff_t end, i_size;
140         pgoff_t end_index;
141 
142         spin_lock(&inode->i_lock);
143         i_size = i_size_read(inode);
144         end_index = (i_size - 1) >> PAGE_CACHE_SHIFT;
145         if (i_size > 0 && page->index < end_index)
146                 goto out;
147         end = ((loff_t)page->index << PAGE_CACHE_SHIFT) + ((loff_t)offset+count);
148         if (i_size >= end)
149                 goto out;
150         i_size_write(inode, end);
151         nfs_inc_stats(inode, NFSIOS_EXTENDWRITE);
152 out:
153         spin_unlock(&inode->i_lock);
154 }
155 
156 /* A writeback failed: mark the page as bad, and invalidate the page cache */
157 static void nfs_set_pageerror(struct page *page)
158 {
159         SetPageError(page);
160         nfs_zap_mapping(page->mapping->host, page->mapping);
161 }
162 
163 /* We can set the PG_uptodate flag if we see that a write request
164  * covers the full page.
165  */
166 static void nfs_mark_uptodate(struct page *page, unsigned int base, unsigned int count)
167 {
168         if (PageUptodate(page))
169                 return;
170         if (base != 0)
171                 return;
172         if (count != nfs_page_length(page))
173                 return;
174         SetPageUptodate(page);
175 }
176 
177 static int wb_priority(struct writeback_control *wbc)
178 {
179         if (wbc->for_reclaim)
180                 return FLUSH_HIGHPRI | FLUSH_STABLE;
181         if (wbc->for_kupdate)
182                 return FLUSH_LOWPRI;
183         return 0;
184 }
185 
186 /*
187  * NFS congestion control
188  */
189 
190 int nfs_congestion_kb;
191 
192 #define NFS_CONGESTION_ON_THRESH        (nfs_congestion_kb >> (PAGE_SHIFT-10))
193 #define NFS_CONGESTION_OFF_THRESH       \
194         (NFS_CONGESTION_ON_THRESH - (NFS_CONGESTION_ON_THRESH >> 2))
195 
196 static int nfs_set_page_writeback(struct page *page)
197 {
198         int ret = test_set_page_writeback(page);
199 
200         if (!ret) {
201                 struct inode *inode = page->mapping->host;
202                 struct nfs_server *nfss = NFS_SERVER(inode);
203 
204                 if (atomic_long_inc_return(&nfss->writeback) >
205                                 NFS_CONGESTION_ON_THRESH) {
206                         set_bdi_congested(&nfss->backing_dev_info,
207                                                 BLK_RW_ASYNC);
208                 }
209         }
210         return ret;
211 }
212 
213 static void nfs_end_page_writeback(struct page *page)
214 {
215         struct inode *inode = page->mapping->host;
216         struct nfs_server *nfss = NFS_SERVER(inode);
217 
218         end_page_writeback(page);
219         if (atomic_long_dec_return(&nfss->writeback) < NFS_CONGESTION_OFF_THRESH)
220                 clear_bdi_congested(&nfss->backing_dev_info, BLK_RW_ASYNC);
221 }
222 
223 static struct nfs_page *nfs_find_and_lock_request(struct page *page)
224 {
225         struct inode *inode = page->mapping->host;
226         struct nfs_page *req;
227         int ret;
228 
229         spin_lock(&inode->i_lock);
230         for (;;) {
231                 req = nfs_page_find_request_locked(page);
232                 if (req == NULL)
233                         break;
234                 if (nfs_set_page_tag_locked(req))
235                         break;
236                 /* Note: If we hold the page lock, as is the case in nfs_writepage,
237                  *       then the call to nfs_set_page_tag_locked() will always
238                  *       succeed provided that someone hasn't already marked the
239                  *       request as dirty (in which case we don't care).
240                  */
241                 spin_unlock(&inode->i_lock);
242                 ret = nfs_wait_on_request(req);
243                 nfs_release_request(req);
244                 if (ret != 0)
245                         return ERR_PTR(ret);
246                 spin_lock(&inode->i_lock);
247         }
248         spin_unlock(&inode->i_lock);
249         return req;
250 }
251 
252 /*
253  * Find an associated nfs write request, and prepare to flush it out
254  * May return an error if the user signalled nfs_wait_on_request().
255  */
256 static int nfs_page_async_flush(struct nfs_pageio_descriptor *pgio,
257                                 struct page *page)
258 {
259         struct nfs_page *req;
260         int ret = 0;
261 
262         req = nfs_find_and_lock_request(page);
263         if (!req)
264                 goto out;
265         ret = PTR_ERR(req);
266         if (IS_ERR(req))
267                 goto out;
268 
269         ret = nfs_set_page_writeback(page);
270         BUG_ON(ret != 0);
271         BUG_ON(test_bit(PG_CLEAN, &req->wb_flags));
272 
273         if (!nfs_pageio_add_request(pgio, req)) {
274                 nfs_redirty_request(req);
275                 ret = pgio->pg_error;
276         }
277 out:
278         return ret;
279 }
280 
281 static int nfs_do_writepage(struct page *page, struct writeback_control *wbc, struct nfs_pageio_descriptor *pgio)
282 {
283         struct inode *inode = page->mapping->host;
284 
285         nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGE);
286         nfs_add_stats(inode, NFSIOS_WRITEPAGES, 1);
287 
288         nfs_pageio_cond_complete(pgio, page->index);
289         return nfs_page_async_flush(pgio, page);
290 }
291 
292 /*
293  * Write an mmapped page to the server.
294  */
295 static int nfs_writepage_locked(struct page *page, struct writeback_control *wbc)
296 {
297         struct nfs_pageio_descriptor pgio;
298         int err;
299 
300         nfs_pageio_init_write(&pgio, page->mapping->host, wb_priority(wbc));
301         err = nfs_do_writepage(page, wbc, &pgio);
302         nfs_pageio_complete(&pgio);
303         if (err < 0)
304                 return err;
305         if (pgio.pg_error < 0)
306                 return pgio.pg_error;
307         return 0;
308 }
309 
310 int nfs_writepage(struct page *page, struct writeback_control *wbc)
311 {
312         int ret;
313 
314         ret = nfs_writepage_locked(page, wbc);
315         unlock_page(page);
316         return ret;
317 }
318 
319 static int nfs_writepages_callback(struct page *page, struct writeback_control *wbc, void *data)
320 {
321         int ret;
322 
323         ret = nfs_do_writepage(page, wbc, data);
324         unlock_page(page);
325         return ret;
326 }
327 
328 int nfs_writepages(struct address_space *mapping, struct writeback_control *wbc)
329 {
330         struct inode *inode = mapping->host;
331         unsigned long *bitlock = &NFS_I(inode)->flags;
332         struct nfs_pageio_descriptor pgio;
333         int err;
334 
335         /* Stop dirtying of new pages while we sync */
336         err = wait_on_bit_lock(bitlock, NFS_INO_FLUSHING,
337                         nfs_wait_bit_killable, TASK_KILLABLE);
338         if (err)
339                 goto out_err;
340 
341         nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGES);
342 
343         nfs_pageio_init_write(&pgio, inode, wb_priority(wbc));
344         err = write_cache_pages(mapping, wbc, nfs_writepages_callback, &pgio);
345         nfs_pageio_complete(&pgio);
346 
347         clear_bit_unlock(NFS_INO_FLUSHING, bitlock);
348         smp_mb__after_clear_bit();
349         wake_up_bit(bitlock, NFS_INO_FLUSHING);
350 
351         if (err < 0)
352                 goto out_err;
353         err = pgio.pg_error;
354         if (err < 0)
355                 goto out_err;
356         return 0;
357 out_err:
358         return err;
359 }
360 
361 /*
362  * Insert a write request into an inode
363  */
364 static int nfs_inode_add_request(struct inode *inode, struct nfs_page *req)
365 {
366         struct nfs_inode *nfsi = NFS_I(inode);
367         int error;
368 
369         error = radix_tree_preload(GFP_NOFS);
370         if (error != 0)
371                 goto out;
372 
373         /* Lock the request! */
374         nfs_lock_request_dontget(req);
375 
376         spin_lock(&inode->i_lock);
377         error = radix_tree_insert(&nfsi->nfs_page_tree, req->wb_index, req);
378         BUG_ON(error);
379         if (!nfsi->npages) {
380                 igrab(inode);
381                 if (nfs_have_delegation(inode, FMODE_WRITE))
382                         nfsi->change_attr++;
383         }
384         SetPagePrivate(req->wb_page);
385         set_page_private(req->wb_page, (unsigned long)req);
386         nfsi->npages++;
387         kref_get(&req->wb_kref);
388         radix_tree_tag_set(&nfsi->nfs_page_tree, req->wb_index,
389                                 NFS_PAGE_TAG_LOCKED);
390         spin_unlock(&inode->i_lock);
391         radix_tree_preload_end();
392 out:
393         return error;
394 }
395 
396 /*
397  * Remove a write request from an inode
398  */
399 static void nfs_inode_remove_request(struct nfs_page *req)
400 {
401         struct inode *inode = req->wb_context->path.dentry->d_inode;
402         struct nfs_inode *nfsi = NFS_I(inode);
403 
404         BUG_ON (!NFS_WBACK_BUSY(req));
405 
406         spin_lock(&inode->i_lock);
407         set_page_private(req->wb_page, 0);
408         ClearPagePrivate(req->wb_page);
409         radix_tree_delete(&nfsi->nfs_page_tree, req->wb_index);
410         nfsi->npages--;
411         if (!nfsi->npages) {
412                 spin_unlock(&inode->i_lock);
413                 iput(inode);
414         } else
415                 spin_unlock(&inode->i_lock);
416         nfs_clear_request(req);
417         nfs_release_request(req);
418 }
419 
420 static void
421 nfs_mark_request_dirty(struct nfs_page *req)
422 {
423         __set_page_dirty_nobuffers(req->wb_page);
424 }
425 
426 #if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
427 /*
428  * Add a request to the inode's commit list.
429  */
430 static void
431 nfs_mark_request_commit(struct nfs_page *req)
432 {
433         struct inode *inode = req->wb_context->path.dentry->d_inode;
434         struct nfs_inode *nfsi = NFS_I(inode);
435 
436         spin_lock(&inode->i_lock);
437         set_bit(PG_CLEAN, &(req)->wb_flags);
438         radix_tree_tag_set(&nfsi->nfs_page_tree,
439                         req->wb_index,
440                         NFS_PAGE_TAG_COMMIT);
441         spin_unlock(&inode->i_lock);
442         inc_zone_page_state(req->wb_page, NR_UNSTABLE_NFS);
443         inc_bdi_stat(req->wb_page->mapping->backing_dev_info, BDI_RECLAIMABLE);
444         __mark_inode_dirty(inode, I_DIRTY_DATASYNC);
445 }
446 
447 static int
448 nfs_clear_request_commit(struct nfs_page *req)
449 {
450         struct page *page = req->wb_page;
451 
452         if (test_and_clear_bit(PG_CLEAN, &(req)->wb_flags)) {
453                 dec_zone_page_state(page, NR_UNSTABLE_NFS);
454                 dec_bdi_stat(page->mapping->backing_dev_info, BDI_RECLAIMABLE);
455                 return 1;
456         }
457         return 0;
458 }
459 
460 static inline
461 int nfs_write_need_commit(struct nfs_write_data *data)
462 {
463         return data->verf.committed != NFS_FILE_SYNC;
464 }
465 
466 static inline
467 int nfs_reschedule_unstable_write(struct nfs_page *req)
468 {
469         if (test_and_clear_bit(PG_NEED_COMMIT, &req->wb_flags)) {
470                 nfs_mark_request_commit(req);
471                 return 1;
472         }
473         if (test_and_clear_bit(PG_NEED_RESCHED, &req->wb_flags)) {
474                 nfs_mark_request_dirty(req);
475                 return 1;
476         }
477         return 0;
478 }
479 #else
480 static inline void
481 nfs_mark_request_commit(struct nfs_page *req)
482 {
483 }
484 
485 static inline int
486 nfs_clear_request_commit(struct nfs_page *req)
487 {
488         return 0;
489 }
490 
491 static inline
492 int nfs_write_need_commit(struct nfs_write_data *data)
493 {
494         return 0;
495 }
496 
497 static inline
498 int nfs_reschedule_unstable_write(struct nfs_page *req)
499 {
500         return 0;
501 }
502 #endif
503 
504 /*
505  * Wait for a request to complete.
506  *
507  * Interruptible by fatal signals only.
508  */
509 static int nfs_wait_on_requests_locked(struct inode *inode, pgoff_t idx_start, unsigned int npages)
510 {
511         struct nfs_inode *nfsi = NFS_I(inode);
512         struct nfs_page *req;
513         pgoff_t idx_end, next;
514         unsigned int            res = 0;
515         int                     error;
516 
517         if (npages == 0)
518                 idx_end = ~0;
519         else
520                 idx_end = idx_start + npages - 1;
521 
522         next = idx_start;
523         while (radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree, (void **)&req, next, 1, NFS_PAGE_TAG_LOCKED)) {
524                 if (req->wb_index > idx_end)
525                         break;
526 
527                 next = req->wb_index + 1;
528                 BUG_ON(!NFS_WBACK_BUSY(req));
529 
530                 kref_get(&req->wb_kref);
531                 spin_unlock(&inode->i_lock);
532                 error = nfs_wait_on_request(req);
533                 nfs_release_request(req);
534                 spin_lock(&inode->i_lock);
535                 if (error < 0)
536                         return error;
537                 res++;
538         }
539         return res;
540 }
541 
542 static void nfs_cancel_commit_list(struct list_head *head)
543 {
544         struct nfs_page *req;
545 
546         while(!list_empty(head)) {
547                 req = nfs_list_entry(head->next);
548                 nfs_list_remove_request(req);
549                 nfs_clear_request_commit(req);
550                 nfs_inode_remove_request(req);
551                 nfs_unlock_request(req);
552         }
553 }
554 
555 #if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
556 static int
557 nfs_need_commit(struct nfs_inode *nfsi)
558 {
559         return radix_tree_tagged(&nfsi->nfs_page_tree, NFS_PAGE_TAG_COMMIT);
560 }
561 
562 /*
563  * nfs_scan_commit - Scan an inode for commit requests
564  * @inode: NFS inode to scan
565  * @dst: destination list
566  * @idx_start: lower bound of page->index to scan.
567  * @npages: idx_start + npages sets the upper bound to scan.
568  *
569  * Moves requests from the inode's 'commit' request list.
570  * The requests are *not* checked to ensure that they form a contiguous set.
571  */
572 static int
573 nfs_scan_commit(struct inode *inode, struct list_head *dst, pgoff_t idx_start, unsigned int npages)
574 {
575         struct nfs_inode *nfsi = NFS_I(inode);
576 
577         if (!nfs_need_commit(nfsi))
578                 return 0;
579 
580         return nfs_scan_list(nfsi, dst, idx_start, npages, NFS_PAGE_TAG_COMMIT);
581 }
582 #else
583 static inline int nfs_need_commit(struct nfs_inode *nfsi)
584 {
585         return 0;
586 }
587 
588 static inline int nfs_scan_commit(struct inode *inode, struct list_head *dst, pgoff_t idx_start, unsigned int npages)
589 {
590         return 0;
591 }
592 #endif
593 
594 /*
595  * Search for an existing write request, and attempt to update
596  * it to reflect a new dirty region on a given page.
597  *
598  * If the attempt fails, then the existing request is flushed out
599  * to disk.
600  */
601 static struct nfs_page *nfs_try_to_update_request(struct inode *inode,
602                 struct page *page,
603                 unsigned int offset,
604                 unsigned int bytes)
605 {
606         struct nfs_page *req;
607         unsigned int rqend;
608         unsigned int end;
609         int error;
610 
611         if (!PagePrivate(page))
612                 return NULL;
613 
614         end = offset + bytes;
615         spin_lock(&inode->i_lock);
616 
617         for (;;) {
618                 req = nfs_page_find_request_locked(page);
619                 if (req == NULL)
620                         goto out_unlock;
621 
622                 rqend = req->wb_offset + req->wb_bytes;
623                 /*
624                  * Tell the caller to flush out the request if
625                  * the offsets are non-contiguous.
626                  * Note: nfs_flush_incompatible() will already
627                  * have flushed out requests having wrong owners.
628                  */
629                 if (offset > rqend
630                     || end < req->wb_offset)
631                         goto out_flushme;
632 
633                 if (nfs_set_page_tag_locked(req))
634                         break;
635 
636                 /* The request is locked, so wait and then retry */
637                 spin_unlock(&inode->i_lock);
638                 error = nfs_wait_on_request(req);
639                 nfs_release_request(req);
640                 if (error != 0)
641                         goto out_err;
642                 spin_lock(&inode->i_lock);
643         }
644 
645         if (nfs_clear_request_commit(req))
646                 radix_tree_tag_clear(&NFS_I(inode)->nfs_page_tree,
647                                 req->wb_index, NFS_PAGE_TAG_COMMIT);
648 
649         /* Okay, the request matches. Update the region */
650         if (offset < req->wb_offset) {
651                 req->wb_offset = offset;
652                 req->wb_pgbase = offset;
653         }
654         if (end > rqend)
655                 req->wb_bytes = end - req->wb_offset;
656         else
657                 req->wb_bytes = rqend - req->wb_offset;
658 out_unlock:
659         spin_unlock(&inode->i_lock);
660         return req;
661 out_flushme:
662         spin_unlock(&inode->i_lock);
663         nfs_release_request(req);
664         error = nfs_wb_page(inode, page);
665 out_err:
666         return ERR_PTR(error);
667 }
668 
669 /*
670  * Try to update an existing write request, or create one if there is none.
671  *
672  * Note: Should always be called with the Page Lock held to prevent races
673  * if we have to add a new request. Also assumes that the caller has
674  * already called nfs_flush_incompatible() if necessary.
675  */
676 static struct nfs_page * nfs_setup_write_request(struct nfs_open_context* ctx,
677                 struct page *page, unsigned int offset, unsigned int bytes)
678 {
679         struct inode *inode = page->mapping->host;
680         struct nfs_page *req;
681         int error;
682 
683         req = nfs_try_to_update_request(inode, page, offset, bytes);
684         if (req != NULL)
685                 goto out;
686         req = nfs_create_request(ctx, inode, page, offset, bytes);
687         if (IS_ERR(req))
688                 goto out;
689         error = nfs_inode_add_request(inode, req);
690         if (error != 0) {
691                 nfs_release_request(req);
692                 req = ERR_PTR(error);
693         }
694 out:
695         return req;
696 }
697 
698 static int nfs_writepage_setup(struct nfs_open_context *ctx, struct page *page,
699                 unsigned int offset, unsigned int count)
700 {
701         struct nfs_page *req;
702 
703         req = nfs_setup_write_request(ctx, page, offset, count);
704         if (IS_ERR(req))
705                 return PTR_ERR(req);
706         /* Update file length */
707         nfs_grow_file(page, offset, count);
708         nfs_mark_uptodate(page, req->wb_pgbase, req->wb_bytes);
709         nfs_clear_page_tag_locked(req);
710         return 0;
711 }
712 
713 int nfs_flush_incompatible(struct file *file, struct page *page)
714 {
715         struct nfs_open_context *ctx = nfs_file_open_context(file);
716         struct nfs_page *req;
717         int do_flush, status;
718         /*
719          * Look for a request corresponding to this page. If there
720          * is one, and it belongs to another file, we flush it out
721          * before we try to copy anything into the page. Do this
722          * due to the lack of an ACCESS-type call in NFSv2.
723          * Also do the same if we find a request from an existing
724          * dropped page.
725          */
726         do {
727                 req = nfs_page_find_request(page);
728                 if (req == NULL)
729                         return 0;
730                 do_flush = req->wb_page != page || req->wb_context != ctx;
731                 nfs_release_request(req);
732                 if (!do_flush)
733                         return 0;
734                 status = nfs_wb_page(page->mapping->host, page);
735         } while (status == 0);
736         return status;
737 }
738 
739 /*
740  * If the page cache is marked as unsafe or invalid, then we can't rely on
741  * the PageUptodate() flag. In this case, we will need to turn off
742  * write optimisations that depend on the page contents being correct.
743  */
744 static int nfs_write_pageuptodate(struct page *page, struct inode *inode)
745 {
746         return PageUptodate(page) &&
747                 !(NFS_I(inode)->cache_validity & (NFS_INO_REVAL_PAGECACHE|NFS_INO_INVALID_DATA));
748 }
749 
750 /*
751  * Update and possibly write a cached page of an NFS file.
752  *
753  * XXX: Keep an eye on generic_file_read to make sure it doesn't do bad
754  * things with a page scheduled for an RPC call (e.g. invalidate it).
755  */
756 int nfs_updatepage(struct file *file, struct page *page,
757                 unsigned int offset, unsigned int count)
758 {
759         struct nfs_open_context *ctx = nfs_file_open_context(file);
760         struct inode    *inode = page->mapping->host;
761         int             status = 0;
762 
763         nfs_inc_stats(inode, NFSIOS_VFSUPDATEPAGE);
764 
765         dprintk("NFS:       nfs_updatepage(%s/%s %d@%lld)\n",
766                 file->f_path.dentry->d_parent->d_name.name,
767                 file->f_path.dentry->d_name.name, count,
768                 (long long)(page_offset(page) + offset));
769 
770         /* If we're not using byte range locks, and we know the page
771          * is up to date, it may be more efficient to extend the write
772          * to cover the entire page in order to avoid fragmentation
773          * inefficiencies.
774          */
775         if (nfs_write_pageuptodate(page, inode) &&
776                         inode->i_flock == NULL &&
777                         !(file->f_flags & O_SYNC)) {
778                 count = max(count + offset, nfs_page_length(page));
779                 offset = 0;
780         }
781 
782         status = nfs_writepage_setup(ctx, page, offset, count);
783         if (status < 0)
784                 nfs_set_pageerror(page);
785         else
786                 __set_page_dirty_nobuffers(page);
787 
788         dprintk("NFS:       nfs_updatepage returns %d (isize %lld)\n",
789                         status, (long long)i_size_read(inode));
790         return status;
791 }
792 
793 static void nfs_writepage_release(struct nfs_page *req)
794 {
795 
796         if (PageError(req->wb_page) || !nfs_reschedule_unstable_write(req)) {
797                 nfs_end_page_writeback(req->wb_page);
798                 nfs_inode_remove_request(req);
799         } else
800                 nfs_end_page_writeback(req->wb_page);
801         nfs_clear_page_tag_locked(req);
802 }
803 
804 static int flush_task_priority(int how)
805 {
806         switch (how & (FLUSH_HIGHPRI|FLUSH_LOWPRI)) {
807                 case FLUSH_HIGHPRI:
808                         return RPC_PRIORITY_HIGH;
809                 case FLUSH_LOWPRI:
810                         return RPC_PRIORITY_LOW;
811         }
812         return RPC_PRIORITY_NORMAL;
813 }
814 
815 /*
816  * Set up the argument/result storage required for the RPC call.
817  */
818 static int nfs_write_rpcsetup(struct nfs_page *req,
819                 struct nfs_write_data *data,
820                 const struct rpc_call_ops *call_ops,
821                 unsigned int count, unsigned int offset,
822                 int how)
823 {
824         struct inode *inode = req->wb_context->path.dentry->d_inode;
825         int flags = (how & FLUSH_SYNC) ? 0 : RPC_TASK_ASYNC;
826         int priority = flush_task_priority(how);
827         struct rpc_task *task;
828         struct rpc_message msg = {
829                 .rpc_argp = &data->args,
830                 .rpc_resp = &data->res,
831                 .rpc_cred = req->wb_context->cred,
832         };
833         struct rpc_task_setup task_setup_data = {
834                 .rpc_client = NFS_CLIENT(inode),
835                 .task = &data->task,
836                 .rpc_message = &msg,
837                 .callback_ops = call_ops,
838                 .callback_data = data,
839                 .workqueue = nfsiod_workqueue,
840                 .flags = flags,
841                 .priority = priority,
842         };
843 
844         /* Set up the RPC argument and reply structs
845          * NB: take care not to mess about with data->commit et al. */
846 
847         data->req = req;
848         data->inode = inode = req->wb_context->path.dentry->d_inode;
849         data->cred = msg.rpc_cred;
850 
851         data->args.fh     = NFS_FH(inode);
852         data->args.offset = req_offset(req) + offset;
853         data->args.pgbase = req->wb_pgbase + offset;
854         data->args.pages  = data->pagevec;
855         data->args.count  = count;
856         data->args.context = get_nfs_open_context(req->wb_context);
857         data->args.stable  = NFS_UNSTABLE;
858         if (how & FLUSH_STABLE) {
859                 data->args.stable = NFS_DATA_SYNC;
860                 if (!nfs_need_commit(NFS_I(inode)))
861                         data->args.stable = NFS_FILE_SYNC;
862         }
863 
864         data->res.fattr   = &data->fattr;
865         data->res.count   = count;
866         data->res.verf    = &data->verf;
867         nfs_fattr_init(&data->fattr);
868 
869         /* Set up the initial task struct.  */
870         NFS_PROTO(inode)->write_setup(data, &msg);
871 
872         dprintk("NFS: %5u initiated write call "
873                 "(req %s/%lld, %u bytes @ offset %llu)\n",
874                 data->task.tk_pid,
875                 inode->i_sb->s_id,
876                 (long long)NFS_FILEID(inode),
877                 count,
878                 (unsigned long long)data->args.offset);
879 
880         task = rpc_run_task(&task_setup_data);
881         if (IS_ERR(task))
882                 return PTR_ERR(task);
883         rpc_put_task(task);
884         return 0;
885 }
886 
887 /* If a nfs_flush_* function fails, it should remove reqs from @head and
888  * call this on each, which will prepare them to be retried on next
889  * writeback using standard nfs.
890  */
891 static void nfs_redirty_request(struct nfs_page *req)
892 {
893         nfs_mark_request_dirty(req);
894         nfs_end_page_writeback(req->wb_page);
895         nfs_clear_page_tag_locked(req);
896 }
897 
898 /*
899  * Generate multiple small requests to write out a single
900  * contiguous dirty area on one page.
901  */
902 static int nfs_flush_multi(struct inode *inode, struct list_head *head, unsigned int npages, size_t count, int how)
903 {
904         struct nfs_page *req = nfs_list_entry(head->next);
905         struct page *page = req->wb_page;
906         struct nfs_write_data *data;
907         size_t wsize = NFS_SERVER(inode)->wsize, nbytes;
908         unsigned int offset;
909         int requests = 0;
910         int ret = 0;
911         LIST_HEAD(list);
912 
913         nfs_list_remove_request(req);
914 
915         nbytes = count;
916         do {
917                 size_t len = min(nbytes, wsize);
918 
919                 data = nfs_writedata_alloc(1);
920                 if (!data)
921                         goto out_bad;
922                 list_add(&data->pages, &list);
923                 requests++;
924                 nbytes -= len;
925         } while (nbytes != 0);
926         atomic_set(&req->wb_complete, requests);
927 
928         ClearPageError(page);
929         offset = 0;
930         nbytes = count;
931         do {
932                 int ret2;
933 
934                 data = list_entry(list.next, struct nfs_write_data, pages);
935                 list_del_init(&data->pages);
936 
937                 data->pagevec[0] = page;
938 
939                 if (nbytes < wsize)
940                         wsize = nbytes;
941                 ret2 = nfs_write_rpcsetup(req, data, &nfs_write_partial_ops,
942                                    wsize, offset, how);
943                 if (ret == 0)
944                         ret = ret2;
945                 offset += wsize;
946                 nbytes -= wsize;
947         } while (nbytes != 0);
948 
949         return ret;
950 
951 out_bad:
952         while (!list_empty(&list)) {
953                 data = list_entry(list.next, struct nfs_write_data, pages);
954                 list_del(&data->pages);
955                 nfs_writedata_release(data);
956         }
957         nfs_redirty_request(req);
958         return -ENOMEM;
959 }
960 
961 /*
962  * Create an RPC task for the given write request and kick it.
963  * The page must have been locked by the caller.
964  *
965  * It may happen that the page we're passed is not marked dirty.
966  * This is the case if nfs_updatepage detects a conflicting request
967  * that has been written but not committed.
968  */
969 static int nfs_flush_one(struct inode *inode, struct list_head *head, unsigned int npages, size_t count, int how)
970 {
971         struct nfs_page         *req;
972         struct page             **pages;
973         struct nfs_write_data   *data;
974 
975         data = nfs_writedata_alloc(npages);
976         if (!data)
977                 goto out_bad;
978 
979         pages = data->pagevec;
980         while (!list_empty(head)) {
981                 req = nfs_list_entry(head->next);
982                 nfs_list_remove_request(req);
983                 nfs_list_add_request(req, &data->pages);
984                 ClearPageError(req->wb_page);
985                 *pages++ = req->wb_page;
986         }
987         req = nfs_list_entry(data->pages.next);
988 
989         /* Set up the argument struct */
990         return nfs_write_rpcsetup(req, data, &nfs_write_full_ops, count, 0, how);
991  out_bad:
992         while (!list_empty(head)) {
993                 req = nfs_list_entry(head->next);
994                 nfs_list_remove_request(req);
995                 nfs_redirty_request(req);
996         }
997         return -ENOMEM;
998 }
999 
1000 static void nfs_pageio_init_write(struct nfs_pageio_descriptor *pgio,
1001                                   struct inode *inode, int ioflags)
1002 {
1003         size_t wsize = NFS_SERVER(inode)->wsize;
1004 
1005         if (wsize < PAGE_CACHE_SIZE)
1006                 nfs_pageio_init(pgio, inode, nfs_flush_multi, wsize, ioflags);
1007         else
1008                 nfs_pageio_init(pgio, inode, nfs_flush_one, wsize, ioflags);
1009 }
1010 
1011 /*
1012  * Handle a write reply that flushed part of a page.
1013  */
1014 static void nfs_writeback_done_partial(struct rpc_task *task, void *calldata)
1015 {
1016         struct nfs_write_data   *data = calldata;
1017 
1018         dprintk("NFS: %5u write(%s/%lld %d@%lld)",
1019                 task->tk_pid,
1020                 data->req->wb_context->path.dentry->d_inode->i_sb->s_id,
1021                 (long long)
1022                   NFS_FILEID(data->req->wb_context->path.dentry->d_inode),
1023                 data->req->wb_bytes, (long long)req_offset(data->req));
1024 
1025         nfs_writeback_done(task, data);
1026 }
1027 
1028 static void nfs_writeback_release_partial(void *calldata)
1029 {
1030         struct nfs_write_data   *data = calldata;
1031         struct nfs_page         *req = data->req;
1032         struct page             *page = req->wb_page;
1033         int status = data->task.tk_status;
1034 
1035         if (status < 0) {
1036                 nfs_set_pageerror(page);
1037                 nfs_context_set_write_error(req->wb_context, status);
1038                 dprintk(", error = %d\n", status);
1039                 goto out;
1040         }
1041 
1042         if (nfs_write_need_commit(data)) {
1043                 struct inode *inode = page->mapping->host;
1044 
1045                 spin_lock(&inode->i_lock);
1046                 if (test_bit(PG_NEED_RESCHED, &req->wb_flags)) {
1047                         /* Do nothing we need to resend the writes */
1048                 } else if (!test_and_set_bit(PG_NEED_COMMIT, &req->wb_flags)) {
1049                         memcpy(&req->wb_verf, &data->verf, sizeof(req->wb_verf));
1050                         dprintk(" defer commit\n");
1051                 } else if (memcmp(&req->wb_verf, &data->verf, sizeof(req->wb_verf))) {
1052                         set_bit(PG_NEED_RESCHED, &req->wb_flags);
1053                         clear_bit(PG_NEED_COMMIT, &req->wb_flags);
1054                         dprintk(" server reboot detected\n");
1055                 }
1056                 spin_unlock(&inode->i_lock);
1057         } else
1058                 dprintk(" OK\n");
1059 
1060 out:
1061         if (atomic_dec_and_test(&req->wb_complete))
1062                 nfs_writepage_release(req);
1063         nfs_writedata_release(calldata);
1064 }
1065 
1066 #if defined(CONFIG_NFS_V4_1)
1067 void nfs_write_prepare(struct rpc_task *task, void *calldata)
1068 {
1069         struct nfs_write_data *data = calldata;
1070         struct nfs_client *clp = (NFS_SERVER(data->inode))->nfs_client;
1071 
1072         if (nfs4_setup_sequence(clp, &data->args.seq_args,
1073                                 &data->res.seq_res, 1, task))
1074                 return;
1075         rpc_call_start(task);
1076 }
1077 #endif /* CONFIG_NFS_V4_1 */
1078 
1079 static const struct rpc_call_ops nfs_write_partial_ops = {
1080 #if defined(CONFIG_NFS_V4_1)
1081         .rpc_call_prepare = nfs_write_prepare,
1082 #endif /* CONFIG_NFS_V4_1 */
1083         .rpc_call_done = nfs_writeback_done_partial,
1084         .rpc_release = nfs_writeback_release_partial,
1085 };
1086 
1087 /*
1088  * Handle a write reply that flushes a whole page.
1089  *
1090  * FIXME: There is an inherent race with invalidate_inode_pages and
1091  *        writebacks since the page->count is kept > 1 for as long
1092  *        as the page has a write request pending.
1093  */
1094 static void nfs_writeback_done_full(struct rpc_task *task, void *calldata)
1095 {
1096         struct nfs_write_data   *data = calldata;
1097 
1098         nfs_writeback_done(task, data);
1099 }
1100 
1101 static void nfs_writeback_release_full(void *calldata)
1102 {
1103         struct nfs_write_data   *data = calldata;
1104         int status = data->task.tk_status;
1105 
1106         /* Update attributes as result of writeback. */
1107         while (!list_empty(&data->pages)) {
1108                 struct nfs_page *req = nfs_list_entry(data->pages.next);
1109                 struct page *page = req->wb_page;
1110 
1111                 nfs_list_remove_request(req);
1112 
1113                 dprintk("NFS: %5u write (%s/%lld %d@%lld)",
1114                         data->task.tk_pid,
1115                         req->wb_context->path.dentry->d_inode->i_sb->s_id,
1116                         (long long)NFS_FILEID(req->wb_context->path.dentry->d_inode),
1117                         req->wb_bytes,
1118                         (long long)req_offset(req));
1119 
1120                 if (status < 0) {
1121                         nfs_set_pageerror(page);
1122                         nfs_context_set_write_error(req->wb_context, status);
1123                         dprintk(", error = %d\n", status);
1124                         goto remove_request;
1125                 }
1126 
1127                 if (nfs_write_need_commit(data)) {
1128                         memcpy(&req->wb_verf, &data->verf, sizeof(req->wb_verf));
1129                         nfs_mark_request_commit(req);
1130                         nfs_end_page_writeback(page);
1131                         dprintk(" marked for commit\n");
1132                         goto next;
1133                 }
1134                 dprintk(" OK\n");
1135 remove_request:
1136                 nfs_end_page_writeback(page);
1137                 nfs_inode_remove_request(req);
1138         next:
1139                 nfs_clear_page_tag_locked(req);
1140         }
1141         nfs_writedata_release(calldata);
1142 }
1143 
1144 static const struct rpc_call_ops nfs_write_full_ops = {
1145 #if defined(CONFIG_NFS_V4_1)
1146         .rpc_call_prepare = nfs_write_prepare,
1147 #endif /* CONFIG_NFS_V4_1 */
1148         .rpc_call_done = nfs_writeback_done_full,
1149         .rpc_release = nfs_writeback_release_full,
1150 };
1151 
1152 
1153 /*
1154  * This function is called when the WRITE call is complete.
1155  */
1156 int nfs_writeback_done(struct rpc_task *task, struct nfs_write_data *data)
1157 {
1158         struct nfs_writeargs    *argp = &data->args;
1159         struct nfs_writeres     *resp = &data->res;
1160         struct nfs_server       *server = NFS_SERVER(data->inode);
1161         int status;
1162 
1163         dprintk("NFS: %5u nfs_writeback_done (status %d)\n",
1164                 task->tk_pid, task->tk_status);
1165 
1166         /*
1167          * ->write_done will attempt to use post-op attributes to detect
1168          * conflicting writes by other clients.  A strict interpretation
1169          * of close-to-open would allow us to continue caching even if
1170          * another writer had changed the file, but some applications
1171          * depend on tighter cache coherency when writing.
1172          */
1173         status = NFS_PROTO(data->inode)->write_done(task, data);
1174         if (status != 0)
1175                 return status;
1176         nfs_add_stats(data->inode, NFSIOS_SERVERWRITTENBYTES, resp->count);
1177 
1178 #if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
1179         if (resp->verf->committed < argp->stable && task->tk_status >= 0) {
1180                 /* We tried a write call, but the server did not
1181                  * commit data to stable storage even though we
1182                  * requested it.
1183                  * Note: There is a known bug in Tru64 < 5.0 in which
1184                  *       the server reports NFS_DATA_SYNC, but performs
1185                  *       NFS_FILE_SYNC. We therefore implement this checking
1186                  *       as a dprintk() in order to avoid filling syslog.
1187                  */
1188                 static unsigned long    complain;
1189 
1190                 if (time_before(complain, jiffies)) {
1191                         dprintk("NFS:       faulty NFS server %s:"
1192                                 " (committed = %d) != (stable = %d)\n",
1193                                 server->nfs_client->cl_hostname,
1194                                 resp->verf->committed, argp->stable);
1195                         complain = jiffies + 300 * HZ;
1196                 }
1197         }
1198 #endif
1199         /* Is this a short write? */
1200         if (task->tk_status >= 0 && resp->count < argp->count) {
1201                 static unsigned long    complain;
1202 
1203                 nfs_inc_stats(data->inode, NFSIOS_SHORTWRITE);
1204 
1205                 /* Has the server at least made some progress? */
1206                 if (resp->count != 0) {
1207                         /* Was this an NFSv2 write or an NFSv3 stable write? */
1208                         if (resp->verf->committed != NFS_UNSTABLE) {
1209                                 /* Resend from where the server left off */
1210                                 argp->offset += resp->count;
1211                                 argp->pgbase += resp->count;
1212                                 argp->count -= resp->count;
1213                         } else {
1214                                 /* Resend as a stable write in order to avoid
1215                                  * headaches in the case of a server crash.
1216                                  */
1217                                 argp->stable = NFS_FILE_SYNC;
1218                         }
1219                         nfs4_restart_rpc(task, server->nfs_client);
1220                         return -EAGAIN;
1221                 }
1222                 if (time_before(complain, jiffies)) {
1223                         printk(KERN_WARNING
1224                                "NFS: Server wrote zero bytes, expected %u.\n",
1225                                         argp->count);
1226                         complain = jiffies + 300 * HZ;
1227                 }
1228                 /* Can't do anything about it except throw an error. */
1229                 task->tk_status = -EIO;
1230         }
1231         nfs4_sequence_free_slot(server->nfs_client, &data->res.seq_res);
1232         return 0;
1233 }
1234 
1235 
1236 #if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
1237 void nfs_commitdata_release(void *data)
1238 {
1239         struct nfs_write_data *wdata = data;
1240 
1241         put_nfs_open_context(wdata->args.context);
1242         nfs_commit_free(wdata);
1243 }
1244 
1245 /*
1246  * Set up the argument/result storage required for the RPC call.
1247  */
1248 static int nfs_commit_rpcsetup(struct list_head *head,
1249                 struct nfs_write_data *data,
1250                 int how)
1251 {
1252         struct nfs_page *first = nfs_list_entry(head->next);
1253         struct inode *inode = first->wb_context->path.dentry->d_inode;
1254         int flags = (how & FLUSH_SYNC) ? 0 : RPC_TASK_ASYNC;
1255         int priority = flush_task_priority(how);
1256         struct rpc_task *task;
1257         struct rpc_message msg = {
1258                 .rpc_argp = &data->args,
1259                 .rpc_resp = &data->res,
1260                 .rpc_cred = first->wb_context->cred,
1261         };
1262         struct rpc_task_setup task_setup_data = {
1263                 .task = &data->task,
1264                 .rpc_client = NFS_CLIENT(inode),
1265                 .rpc_message = &msg,
1266                 .callback_ops = &nfs_commit_ops,
1267                 .callback_data = data,
1268                 .workqueue = nfsiod_workqueue,
1269                 .flags = flags,
1270                 .priority = priority,
1271         };
1272 
1273         /* Set up the RPC argument and reply structs
1274          * NB: take care not to mess about with data->commit et al. */
1275 
1276         list_splice_init(head, &data->pages);
1277 
1278         data->inode       = inode;
1279         data->cred        = msg.rpc_cred;
1280 
1281         data->args.fh     = NFS_FH(data->inode);
1282         /* Note: we always request a commit of the entire inode */
1283         data->args.offset = 0;
1284         data->args.count  = 0;
1285         data->args.context = get_nfs_open_context(first->wb_context);
1286         data->res.count   = 0;
1287         data->res.fattr   = &data->fattr;
1288         data->res.verf    = &data->verf;
1289         nfs_fattr_init(&data->fattr);
1290 
1291         /* Set up the initial task struct.  */
1292         NFS_PROTO(inode)->commit_setup(data, &msg);
1293 
1294         dprintk("NFS: %5u initiated commit call\n", data->task.tk_pid);
1295 
1296         task = rpc_run_task(&task_setup_data);
1297         if (IS_ERR(task))
1298                 return PTR_ERR(task);
1299         rpc_put_task(task);
1300         return 0;
1301 }
1302 
1303 /*
1304  * Commit dirty pages
1305  */
1306 static int
1307 nfs_commit_list(struct inode *inode, struct list_head *head, int how)
1308 {
1309         struct nfs_write_data   *data;
1310         struct nfs_page         *req;
1311 
1312         data = nfs_commitdata_alloc();
1313 
1314         if (!data)
1315                 goto out_bad;
1316 
1317         /* Set up the argument struct */
1318         return nfs_commit_rpcsetup(head, data, how);
1319  out_bad:
1320         while (!list_empty(head)) {
1321                 req = nfs_list_entry(head->next);
1322                 nfs_list_remove_request(req);
1323                 nfs_mark_request_commit(req);
1324                 dec_zone_page_state(req->wb_page, NR_UNSTABLE_NFS);
1325                 dec_bdi_stat(req->wb_page->mapping->backing_dev_info,
1326                                 BDI_RECLAIMABLE);
1327                 nfs_clear_page_tag_locked(req);
1328         }
1329         return -ENOMEM;
1330 }
1331 
1332 /*
1333  * COMMIT call returned
1334  */
1335 static void nfs_commit_done(struct rpc_task *task, void *calldata)
1336 {
1337         struct nfs_write_data   *data = calldata;
1338 
1339         dprintk("NFS: %5u nfs_commit_done (status %d)\n",
1340                                 task->tk_pid, task->tk_status);
1341 
1342         /* Call the NFS version-specific code */
1343         if (NFS_PROTO(data->inode)->commit_done(task, data) != 0)
1344                 return;
1345 }
1346 
1347 static void nfs_commit_release(void *calldata)
1348 {
1349         struct nfs_write_data   *data = calldata;
1350         struct nfs_page         *req;
1351         int status = data->task.tk_status;
1352 
1353         while (!list_empty(&data->pages)) {
1354                 req = nfs_list_entry(data->pages.next);
1355                 nfs_list_remove_request(req);
1356                 nfs_clear_request_commit(req);
1357 
1358                 dprintk("NFS:       commit (%s/%lld %d@%lld)",
1359                         req->wb_context->path.dentry->d_inode->i_sb->s_id,
1360                         (long long)NFS_FILEID(req->wb_context->path.dentry->d_inode),
1361                         req->wb_bytes,
1362                         (long long)req_offset(req));
1363                 if (status < 0) {
1364                         nfs_context_set_write_error(req->wb_context, status);
1365                         nfs_inode_remove_request(req);
1366                         dprintk(", error = %d\n", status);
1367                         goto next;
1368                 }
1369 
1370                 /* Okay, COMMIT succeeded, apparently. Check the verifier
1371                  * returned by the server against all stored verfs. */
1372                 if (!memcmp(req->wb_verf.verifier, data->verf.verifier, sizeof(data->verf.verifier))) {
1373                         /* We have a match */
1374                         nfs_inode_remove_request(req);
1375                         dprintk(" OK\n");
1376                         goto next;
1377                 }
1378                 /* We have a mismatch. Write the page again */
1379                 dprintk(" mismatch\n");
1380                 nfs_mark_request_dirty(req);
1381         next:
1382                 nfs_clear_page_tag_locked(req);
1383         }
1384         nfs_commitdata_release(calldata);
1385 }
1386 
1387 static const struct rpc_call_ops nfs_commit_ops = {
1388 #if defined(CONFIG_NFS_V4_1)
1389         .rpc_call_prepare = nfs_write_prepare,
1390 #endif /* CONFIG_NFS_V4_1 */
1391         .rpc_call_done = nfs_commit_done,
1392         .rpc_release = nfs_commit_release,
1393 };
1394 
1395 int nfs_commit_inode(struct inode *inode, int how)
1396 {
1397         LIST_HEAD(head);
1398         int res;
1399 
1400         spin_lock(&inode->i_lock);
1401         res = nfs_scan_commit(inode, &head, 0, 0);
1402         spin_unlock(&inode->i_lock);
1403         if (res) {
1404                 int error = nfs_commit_list(inode, &head, how);
1405                 if (error < 0)
1406                         return error;
1407         }
1408         return res;
1409 }
1410 #else
1411 static inline int nfs_commit_list(struct inode *inode, struct list_head *head, int how)
1412 {
1413         return 0;
1414 }
1415 #endif
1416 
1417 long nfs_sync_mapping_wait(struct address_space *mapping, struct writeback_control *wbc, int how)
1418 {
1419         struct inode *inode = mapping->host;
1420         pgoff_t idx_start, idx_end;
1421         unsigned int npages = 0;
1422         LIST_HEAD(head);
1423         int nocommit = how & FLUSH_NOCOMMIT;
1424         long pages, ret;
1425 
1426         /* FIXME */
1427         if (wbc->range_cyclic)
1428                 idx_start = 0;
1429         else {
1430                 idx_start = wbc->range_start >> PAGE_CACHE_SHIFT;
1431                 idx_end = wbc->range_end >> PAGE_CACHE_SHIFT;
1432                 if (idx_end > idx_start) {
1433                         pgoff_t l_npages = 1 + idx_end - idx_start;
1434                         npages = l_npages;
1435                         if (sizeof(npages) != sizeof(l_npages) &&
1436                                         (pgoff_t)npages != l_npages)
1437                                 npages = 0;
1438                 }
1439         }
1440         how &= ~FLUSH_NOCOMMIT;
1441         spin_lock(&inode->i_lock);
1442         do {
1443                 ret = nfs_wait_on_requests_locked(inode, idx_start, npages);
1444                 if (ret != 0)
1445                         continue;
1446                 if (nocommit)
1447                         break;
1448                 pages = nfs_scan_commit(inode, &head, idx_start, npages);
1449                 if (pages == 0)
1450                         break;
1451                 if (how & FLUSH_INVALIDATE) {
1452                         spin_unlock(&inode->i_lock);
1453                         nfs_cancel_commit_list(&head);
1454                         ret = pages;
1455                         spin_lock(&inode->i_lock);
1456                         continue;
1457                 }
1458                 pages += nfs_scan_commit(inode, &head, 0, 0);
1459                 spin_unlock(&inode->i_lock);
1460                 ret = nfs_commit_list(inode, &head, how);
1461                 spin_lock(&inode->i_lock);
1462 
1463         } while (ret >= 0);
1464         spin_unlock(&inode->i_lock);
1465         return ret;
1466 }
1467 
1468 static int __nfs_write_mapping(struct address_space *mapping, struct writeback_control *wbc, int how)
1469 {
1470         int ret;
1471 
1472         ret = nfs_writepages(mapping, wbc);
1473         if (ret < 0)
1474                 goto out;
1475         ret = nfs_sync_mapping_wait(mapping, wbc, how);
1476         if (ret < 0)
1477                 goto out;
1478         return 0;
1479 out:
1480         __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1481         return ret;
1482 }
1483 
1484 /* Two pass sync: first using WB_SYNC_NONE, then WB_SYNC_ALL */
1485 static int nfs_write_mapping(struct address_space *mapping, int how)
1486 {
1487         struct writeback_control wbc = {
1488                 .bdi = mapping->backing_dev_info,
1489                 .sync_mode = WB_SYNC_ALL,
1490                 .nr_to_write = LONG_MAX,
1491                 .range_start = 0,
1492                 .range_end = LLONG_MAX,
1493         };
1494 
1495         return __nfs_write_mapping(mapping, &wbc, how);
1496 }
1497 
1498 /*
1499  * flush the inode to disk.
1500  */
1501 int nfs_wb_all(struct inode *inode)
1502 {
1503         return nfs_write_mapping(inode->i_mapping, 0);
1504 }
1505 
1506 int nfs_wb_nocommit(struct inode *inode)
1507 {
1508         return nfs_write_mapping(inode->i_mapping, FLUSH_NOCOMMIT);
1509 }
1510 
1511 int nfs_wb_page_cancel(struct inode *inode, struct page *page)
1512 {
1513         struct nfs_page *req;
1514         loff_t range_start = page_offset(page);
1515         loff_t range_end = range_start + (loff_t)(PAGE_CACHE_SIZE - 1);
1516         struct writeback_control wbc = {
1517                 .bdi = page->mapping->backing_dev_info,
1518                 .sync_mode = WB_SYNC_ALL,
1519                 .nr_to_write = LONG_MAX,
1520                 .range_start = range_start,
1521                 .range_end = range_end,
1522         };
1523         int ret = 0;
1524 
1525         BUG_ON(!PageLocked(page));
1526         for (;;) {
1527                 req = nfs_page_find_request(page);
1528                 if (req == NULL)
1529                         goto out;
1530                 if (test_bit(PG_CLEAN, &req->wb_flags)) {
1531                         nfs_release_request(req);
1532                         break;
1533                 }
1534                 if (nfs_lock_request_dontget(req)) {
1535                         nfs_inode_remove_request(req);
1536                         /*
1537                          * In case nfs_inode_remove_request has marked the
1538                          * page as being dirty
1539                          */
1540                         cancel_dirty_page(page, PAGE_CACHE_SIZE);
1541                         nfs_unlock_request(req);
1542                         break;
1543                 }
1544                 ret = nfs_wait_on_request(req);
1545                 nfs_release_request(req);
1546                 if (ret < 0)
1547                         goto out;
1548         }
1549         if (!PagePrivate(page))
1550                 return 0;
1551         ret = nfs_sync_mapping_wait(page->mapping, &wbc, FLUSH_INVALIDATE);
1552 out:
1553         return ret;
1554 }
1555 
1556 static int nfs_wb_page_priority(struct inode *inode, struct page *page,
1557                                 int how)
1558 {
1559         loff_t range_start = page_offset(page);
1560         loff_t range_end = range_start + (loff_t)(PAGE_CACHE_SIZE - 1);
1561         struct writeback_control wbc = {
1562                 .bdi = page->mapping->backing_dev_info,
1563                 .sync_mode = WB_SYNC_ALL,
1564                 .nr_to_write = LONG_MAX,
1565                 .range_start = range_start,
1566                 .range_end = range_end,
1567         };
1568         int ret;
1569 
1570         do {
1571                 if (clear_page_dirty_for_io(page)) {
1572                         ret = nfs_writepage_locked(page, &wbc);
1573                         if (ret < 0)
1574                                 goto out_error;
1575                 } else if (!PagePrivate(page))
1576                         break;
1577                 ret = nfs_sync_mapping_wait(page->mapping, &wbc, how);
1578                 if (ret < 0)
1579                         goto out_error;
1580         } while (PagePrivate(page));
1581         return 0;
1582 out_error:
1583         __mark_inode_dirty(inode, I_DIRTY_PAGES);
1584         return ret;
1585 }
1586 
1587 /*
1588  * Write back all requests on one page - we do this before reading it.
1589  */
1590 int nfs_wb_page(struct inode *inode, struct page* page)
1591 {
1592         return nfs_wb_page_priority(inode, page, FLUSH_STABLE);
1593 }
1594 
1595 #ifdef CONFIG_MIGRATION
1596 int nfs_migrate_page(struct address_space *mapping, struct page *newpage,
1597                 struct page *page)
1598 {
1599         struct nfs_page *req;
1600         int ret;
1601 
1602         if (PageFsCache(page))
1603                 nfs_fscache_release_page(page, GFP_KERNEL);
1604 
1605         req = nfs_find_and_lock_request(page);
1606         ret = PTR_ERR(req);
1607         if (IS_ERR(req))
1608                 goto out;
1609 
1610         ret = migrate_page(mapping, newpage, page);
1611         if (!req)
1612                 goto out;
1613         if (ret)
1614                 goto out_unlock;
1615         page_cache_get(newpage);
1616         spin_lock(&mapping->host->i_lock);
1617         req->wb_page = newpage;
1618         SetPagePrivate(newpage);
1619         set_page_private(newpage, (unsigned long)req);
1620         ClearPagePrivate(page);
1621         set_page_private(page, 0);
1622         spin_unlock(&mapping->host->i_lock);
1623         page_cache_release(page);
1624 out_unlock:
1625         nfs_clear_page_tag_locked(req);
1626 out:
1627         return ret;
1628 }
1629 #endif
1630 
1631 int __init nfs_init_writepagecache(void)
1632 {
1633         nfs_wdata_cachep = kmem_cache_create("nfs_write_data",
1634                                              sizeof(struct nfs_write_data),
1635                                              0, SLAB_HWCACHE_ALIGN,
1636                                              NULL);
1637         if (nfs_wdata_cachep == NULL)
1638                 return -ENOMEM;
1639 
1640         nfs_wdata_mempool = mempool_create_slab_pool(MIN_POOL_WRITE,
1641                                                      nfs_wdata_cachep);
1642         if (nfs_wdata_mempool == NULL)
1643                 return -ENOMEM;
1644 
1645         nfs_commit_mempool = mempool_create_slab_pool(MIN_POOL_COMMIT,
1646                                                       nfs_wdata_cachep);
1647         if (nfs_commit_mempool == NULL)
1648                 return -ENOMEM;
1649 
1650         /*
1651          * NFS congestion size, scale with available memory.
1652          *
1653          *  64MB:    8192k
1654          * 128MB:   11585k
1655          * 256MB:   16384k
1656          * 512MB:   23170k
1657          *   1GB:   32768k
1658          *   2GB:   46340k
1659          *   4GB:   65536k
1660          *   8GB:   92681k
1661          *  16GB:  131072k
1662          *
1663          * This allows larger machines to have larger/more transfers.
1664          * Limit the default to 256M
1665          */
1666         nfs_congestion_kb = (16*int_sqrt(totalram_pages)) << (PAGE_SHIFT-10);
1667         if (nfs_congestion_kb > 256*1024)
1668                 nfs_congestion_kb = 256*1024;
1669 
1670         return 0;
1671 }
1672 
1673 void nfs_destroy_writepagecache(void)
1674 {
1675         mempool_destroy(nfs_commit_mempool);
1676         mempool_destroy(nfs_wdata_mempool);
1677         kmem_cache_destroy(nfs_wdata_cachep);
1678 }
1679 
1680 

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