fs/afs/write.c

   1 /* handling of writes to regular files and writing back to the server
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11 #include <linux/backing-dev.h>
  12 #include <linux/slab.h>
  13 #include <linux/fs.h>
  14 #include <linux/pagemap.h>
  15 #include <linux/writeback.h>
  16 #include <linux/pagevec.h>
  17 #include "internal.h"
  18
  19 static int afs_write_back_from_locked_page(struct afs_writeback *wb,
  20                                            struct page *page);
  21
  22 /*
  23  * mark a page as having been made dirty and thus needing writeback
  24  */
  25 int afs_set_page_dirty(struct page *page)
  26 {
  27         _enter("");
  28         return __set_page_dirty_nobuffers(page);
  29 }
  30
  31 /*
  32  * unlink a writeback record because its usage has reached zero
  33  * - must be called with the wb->vnode->writeback_lock held
  34  */
  35 static void afs_unlink_writeback(struct afs_writeback *wb)
  36 {
  37         struct afs_writeback *front;
  38         struct afs_vnode *vnode = wb->vnode;
  39
  40         list_del_init(&wb->link);
  41         if (!list_empty(&vnode->writebacks)) {
  42                 /* if an fsync rises to the front of the queue then wake it
  43                  * up */
  44                 front = list_entry(vnode->writebacks.next,
  45                                    struct afs_writeback, link);
  46                 if (front->state == AFS_WBACK_SYNCING) {
  47                         _debug("wake up sync");
  48                         front->state = AFS_WBACK_COMPLETE;
  49                         wake_up(&front->waitq);
  50                 }
  51         }
  52 }
  53
  54 /*
  55  * free a writeback record
  56  */
  57 static void afs_free_writeback(struct afs_writeback *wb)
  58 {
  59         _enter("");
  60         key_put(wb->key);
  61         kfree(wb);
  62 }
  63
  64 /*
  65  * dispose of a reference to a writeback record
  66  */
  67 void afs_put_writeback(struct afs_writeback *wb)
  68 {
  69         struct afs_vnode *vnode = wb->vnode;
  70
  71         _enter("{%d}", wb->usage);
  72
  73         spin_lock(&vnode->writeback_lock);
  74         if (--wb->usage == 0)
  75                 afs_unlink_writeback(wb);
  76         else
  77                 wb = NULL;
  78         spin_unlock(&vnode->writeback_lock);
  79         if (wb)
  80                 afs_free_writeback(wb);
  81 }
  82
  83 /*
  84  * partly or wholly fill a page that's under preparation for writing
  85  */
  86 static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
  87                          loff_t pos, unsigned int len, struct page *page)
  88 {
  89         struct afs_read *req;
  90         int ret;
  91
  92         _enter(",,%llu", (unsigned long long)pos);
  93
  94         req = kzalloc(sizeof(struct afs_read) + sizeof(struct page *),
  95                       GFP_KERNEL);
  96         if (!req)
  97                 return -ENOMEM;
  98
  99         atomic_set(&req->usage, 1);
 100         req->pos = pos;
 101         req->len = len;
 102         req->nr_pages = 1;
 103         req->pages[0] = page;
 104         get_page(page);
 105
 106         ret = afs_vnode_fetch_data(vnode, key, req);
 107         afs_put_read(req);
 108         if (ret < 0) {
 109                 if (ret == -ENOENT) {
 110                         _debug("got NOENT from server"
 111                                " - marking file deleted and stale");
 112                         set_bit(AFS_VNODE_DELETED, &vnode->flags);
 113                         ret = -ESTALE;
 114                 }
 115         }
 116
 117         _leave(" = %d", ret);
 118         return ret;
 119 }
 120
 121 /*
 122  * prepare to perform part of a write to a page
 123  */
 124 int afs_write_begin(struct file *file, struct address_space *mapping,
 125                     loff_t pos, unsigned len, unsigned flags,
 126                     struct page **pagep, void **fsdata)
 127 {
 128         struct afs_writeback *candidate, *wb;
 129         struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
 130         struct page *page;
 131         struct key *key = file->private_data;
 132         unsigned from = pos & (PAGE_SIZE - 1);
 133         unsigned to = from + len;
 134         pgoff_t index = pos >> PAGE_SHIFT;
 135         int ret;
 136
 137         _enter("{%x:%u},{%lx},%u,%u",
 138                vnode->fid.vid, vnode->fid.vnode, index, from, to);
 139
 140         candidate = kzalloc(sizeof(*candidate), GFP_KERNEL);
 141         if (!candidate)
 142                 return -ENOMEM;
 143         candidate->vnode = vnode;
 144         candidate->first = candidate->last = index;
 145         candidate->offset_first = from;
 146         candidate->to_last = to;
 147         INIT_LIST_HEAD(&candidate->link);
 148         candidate->usage = 1;
 149         candidate->state = AFS_WBACK_PENDING;
 150         init_waitqueue_head(&candidate->waitq);
 151
 152         page = grab_cache_page_write_begin(mapping, index, flags);
 153         if (!page) {
 154                 kfree(candidate);
 155                 return -ENOMEM;
 156         }
 157
 158         if (!PageUptodate(page) && len != PAGE_SIZE) {
 159                 ret = afs_fill_page(vnode, key, pos & PAGE_MASK, PAGE_SIZE, page);
 160                 if (ret < 0) {
 161                         unlock_page(page);
 162                         put_page(page);
 163                         kfree(candidate);
 164                         _leave(" = %d [prep]", ret);
 165                         return ret;
 166                 }
 167                 SetPageUptodate(page);
 168         }
 169
 170         /* page won't leak in error case: it eventually gets cleaned off LRU */
 171         *pagep = page;
 172
 173 try_again:
 174         spin_lock(&vnode->writeback_lock);
 175
 176         /* see if this page is already pending a writeback under a suitable key
 177          * - if so we can just join onto that one */
 178         wb = (struct afs_writeback *) page_private(page);
 179         if (wb) {
 180                 if (wb->key == key && wb->state == AFS_WBACK_PENDING)
 181                         goto subsume_in_current_wb;
 182                 goto flush_conflicting_wb;
 183         }
 184
 185         if (index > 0) {
 186                 /* see if we can find an already pending writeback that we can
 187                  * append this page to */
 188                 list_for_each_entry(wb, &vnode->writebacks, link) {
 189                         if (wb->last == index - 1 && wb->key == key &&
 190                             wb->state == AFS_WBACK_PENDING)
 191                                 goto append_to_previous_wb;
 192                 }
 193         }
 194
 195         list_add_tail(&candidate->link, &vnode->writebacks);
 196         candidate->key = key_get(key);
 197         spin_unlock(&vnode->writeback_lock);
 198         SetPagePrivate(page);
 199         set_page_private(page, (unsigned long) candidate);
 200         _leave(" = 0 [new]");
 201         return 0;
 202
 203 subsume_in_current_wb:
 204         _debug("subsume");
 205         ASSERTRANGE(wb->first, <=, index, <=, wb->last);
 206         if (index == wb->first && from < wb->offset_first)
 207                 wb->offset_first = from;
 208         if (index == wb->last && to > wb->to_last)
 209                 wb->to_last = to;
 210         spin_unlock(&vnode->writeback_lock);
 211         kfree(candidate);
 212         _leave(" = 0 [sub]");
 213         return 0;
 214
 215 append_to_previous_wb:
 216         _debug("append into %lx-%lx", wb->first, wb->last);
 217         wb->usage++;
 218         wb->last++;
 219         wb->to_last = to;
 220         spin_unlock(&vnode->writeback_lock);
 221         SetPagePrivate(page);
 222         set_page_private(page, (unsigned long) wb);
 223         kfree(candidate);
 224         _leave(" = 0 [app]");
 225         return 0;
 226
 227         /* the page is currently bound to another context, so if it's dirty we
 228          * need to flush it before we can use the new context */
 229 flush_conflicting_wb:
 230         _debug("flush conflict");
 231         if (wb->state == AFS_WBACK_PENDING)
 232                 wb->state = AFS_WBACK_CONFLICTING;
 233         spin_unlock(&vnode->writeback_lock);
 234         if (clear_page_dirty_for_io(page)) {
 235                 ret = afs_write_back_from_locked_page(wb, page);
 236                 if (ret < 0) {
 237                         afs_put_writeback(candidate);
 238                         _leave(" = %d", ret);
 239                         return ret;
 240                 }
 241         }
 242
 243         /* the page holds a ref on the writeback record */
 244         afs_put_writeback(wb);
 245         set_page_private(page, 0);
 246         ClearPagePrivate(page);
 247         goto try_again;
 248 }
 249
 250 /*
 251  * finalise part of a write to a page
 252  */
 253 int afs_write_end(struct file *file, struct address_space *mapping,
 254                   loff_t pos, unsigned len, unsigned copied,
 255                   struct page *page, void *fsdata)
 256 {
 257         struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
 258         struct key *key = file->private_data;
 259         loff_t i_size, maybe_i_size;
 260         int ret;
 261
 262         _enter("{%x:%u},{%lx}",
 263                vnode->fid.vid, vnode->fid.vnode, page->index);
 264
 265         maybe_i_size = pos + copied;
 266
 267         i_size = i_size_read(&vnode->vfs_inode);
 268         if (maybe_i_size > i_size) {
 269                 spin_lock(&vnode->writeback_lock);
 270                 i_size = i_size_read(&vnode->vfs_inode);
 271                 if (maybe_i_size > i_size)
 272                         i_size_write(&vnode->vfs_inode, maybe_i_size);
 273                 spin_unlock(&vnode->writeback_lock);
 274         }
 275
 276         if (!PageUptodate(page)) {
 277                 if (copied < len) {
 278                         /* Try and load any missing data from the server.  The
 279                          * unmarshalling routine will take care of clearing any
 280                          * bits that are beyond the EOF.
 281                          */
 282                         ret = afs_fill_page(vnode, key, pos + copied,
 283                                             len - copied, page);
 284                         if (ret < 0)
 285                                 return ret;
 286                 }
 287                 SetPageUptodate(page);
 288         }
 289
 290         set_page_dirty(page);
 291         if (PageDirty(page))
 292                 _debug("dirtied");
 293         unlock_page(page);
 294         put_page(page);
 295
 296         return copied;
 297 }
 298
 299 /*
 300  * kill all the pages in the given range
 301  */
 302 static void afs_kill_pages(struct afs_vnode *vnode, bool error,
 303                            pgoff_t first, pgoff_t last)
 304 {
 305         struct pagevec pv;
 306         unsigned count, loop;
 307
 308         _enter("{%x:%u},%lx-%lx",
 309                vnode->fid.vid, vnode->fid.vnode, first, last);
 310
 311         pagevec_init(&pv);
 312
 313         do {
 314                 _debug("kill %lx-%lx", first, last);
 315
 316                 count = last - first + 1;
 317                 if (count > PAGEVEC_SIZE)
 318                         count = PAGEVEC_SIZE;
 319                 pv.nr = find_get_pages_contig(vnode->vfs_inode.i_mapping,
 320                                               first, count, pv.pages);
 321                 ASSERTCMP(pv.nr, ==, count);
 322
 323                 for (loop = 0; loop < count; loop++) {
 324                         struct page *page = pv.pages[loop];
 325                         ClearPageUptodate(page);
 326                         if (error)
 327                                 SetPageError(page);
 328                         if (PageWriteback(page))
 329                                 end_page_writeback(page);
 330                         if (page->index >= first)
 331                                 first = page->index + 1;
 332                 }
 333
 334                 __pagevec_release(&pv);
 335         } while (first < last);
 336
 337         _leave("");
 338 }
 339
 340 /*
 341  * synchronously write back the locked page and any subsequent non-locked dirty
 342  * pages also covered by the same writeback record
 343  */
 344 static int afs_write_back_from_locked_page(struct afs_writeback *wb,
 345                                            struct page *primary_page)
 346 {
 347         struct page *pages[8], *page;
 348         unsigned long count;
 349         unsigned n, offset, to;
 350         pgoff_t start, first, last;
 351         int loop, ret;
 352
 353         _enter(",%lx", primary_page->index);
 354
 355         count = 1;
 356         if (test_set_page_writeback(primary_page))
 357                 BUG();
 358
 359         /* find all consecutive lockable dirty pages, stopping when we find a
 360          * page that is not immediately lockable, is not dirty or is missing,
 361          * or we reach the end of the range */
 362         start = primary_page->index;
 363         if (start >= wb->last)
 364                 goto no_more;
 365         start++;
 366         do {
 367                 _debug("more %lx [%lx]", start, count);
 368                 n = wb->last - start + 1;
 369                 if (n > ARRAY_SIZE(pages))
 370                         n = ARRAY_SIZE(pages);
 371                 n = find_get_pages_contig(wb->vnode->vfs_inode.i_mapping,
 372                                           start, n, pages);
 373                 _debug("fgpc %u", n);
 374                 if (n == 0)
 375                         goto no_more;
 376                 if (pages[0]->index != start) {
 377                         do {
 378                                 put_page(pages[--n]);
 379                         } while (n > 0);
 380                         goto no_more;
 381                 }
 382
 383                 for (loop = 0; loop < n; loop++) {
 384                         page = pages[loop];
 385                         if (page->index > wb->last)
 386                                 break;
 387                         if (!trylock_page(page))
 388                                 break;
 389                         if (!PageDirty(page) ||
 390                             page_private(page) != (unsigned long) wb) {
 391                                 unlock_page(page);
 392                                 break;
 393                         }
 394                         if (!clear_page_dirty_for_io(page))
 395                                 BUG();
 396                         if (test_set_page_writeback(page))
 397                                 BUG();
 398                         unlock_page(page);
 399                         put_page(page);
 400                 }
 401                 count += loop;
 402                 if (loop < n) {
 403                         for (; loop < n; loop++)
 404                                 put_page(pages[loop]);
 405                         goto no_more;
 406                 }
 407
 408                 start += loop;
 409         } while (start <= wb->last && count < 65536);
 410
 411 no_more:
 412         /* we now have a contiguous set of dirty pages, each with writeback set
 413          * and the dirty mark cleared; the first page is locked and must remain
 414          * so, all the rest are unlocked */
 415         first = primary_page->index;
 416         last = first + count - 1;
 417
 418         offset = (first == wb->first) ? wb->offset_first : 0;
 419         to = (last == wb->last) ? wb->to_last : PAGE_SIZE;
 420
 421         _debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to);
 422
 423         ret = afs_vnode_store_data(wb, first, last, offset, to);
 424         if (ret < 0) {
 425                 switch (ret) {
 426                 case -EDQUOT:
 427                 case -ENOSPC:
 428                         mapping_set_error(wb->vnode->vfs_inode.i_mapping, -ENOSPC);
 429                         break;
 430                 case -EROFS:
 431                 case -EIO:
 432                 case -EREMOTEIO:
 433                 case -EFBIG:
 434                 case -ENOENT:
 435                 case -ENOMEDIUM:
 436                 case -ENXIO:
 437                         afs_kill_pages(wb->vnode, true, first, last);
 438                         mapping_set_error(wb->vnode->vfs_inode.i_mapping, -EIO);
 439                         break;
 440                 case -EACCES:
 441                 case -EPERM:
 442                 case -ENOKEY:
 443                 case -EKEYEXPIRED:
 444                 case -EKEYREJECTED:
 445                 case -EKEYREVOKED:
 446                         afs_kill_pages(wb->vnode, false, first, last);
 447                         break;
 448                 default:
 449                         break;
 450                 }
 451         } else {
 452                 ret = count;
 453         }
 454
 455         _leave(" = %d", ret);
 456         return ret;
 457 }
 458
 459 /*
 460  * write a page back to the server
 461  * - the caller locked the page for us
 462  */
 463 int afs_writepage(struct page *page, struct writeback_control *wbc)
 464 {
 465         struct afs_writeback *wb;
 466         int ret;
 467
 468         _enter("{%lx},", page->index);
 469
 470         wb = (struct afs_writeback *) page_private(page);
 471         ASSERT(wb != NULL);
 472
 473         ret = afs_write_back_from_locked_page(wb, page);
 474         unlock_page(page);
 475         if (ret < 0) {
 476                 _leave(" = %d", ret);
 477                 return 0;
 478         }
 479
 480         wbc->nr_to_write -= ret;
 481
 482         _leave(" = 0");
 483         return 0;
 484 }
 485
 486 /*
 487  * write a region of pages back to the server
 488  */
 489 static int afs_writepages_region(struct address_space *mapping,
 490                                  struct writeback_control *wbc,
 491                                  pgoff_t index, pgoff_t end, pgoff_t *_next)
 492 {
 493         struct afs_writeback *wb;
 494         struct page *page;
 495         int ret, n;
 496
 497         _enter(",,%lx,%lx,", index, end);
 498
 499         do {
 500                 n = find_get_pages_range_tag(mapping, &index, end,
 501                                         PAGECACHE_TAG_DIRTY, 1, &page);
 502                 if (!n)
 503                         break;
 504
 505                 _debug("wback %lx", page->index);
 506
 507                 /* at this point we hold neither mapping->tree_lock nor lock on
 508                  * the page itself: the page may be truncated or invalidated
 509                  * (changing page->mapping to NULL), or even swizzled back from
 510                  * swapper_space to tmpfs file mapping
 511                  */
 512                 lock_page(page);
 513
 514                 if (page->mapping != mapping || !PageDirty(page)) {
 515                         unlock_page(page);
 516                         put_page(page);
 517                         continue;
 518                 }
 519
 520                 if (PageWriteback(page)) {
 521                         unlock_page(page);
 522                         if (wbc->sync_mode != WB_SYNC_NONE)
 523                                 wait_on_page_writeback(page);
 524                         put_page(page);
 525                         continue;
 526                 }
 527
 528                 wb = (struct afs_writeback *) page_private(page);
 529                 ASSERT(wb != NULL);
 530
 531                 spin_lock(&wb->vnode->writeback_lock);
 532                 wb->state = AFS_WBACK_WRITING;
 533                 spin_unlock(&wb->vnode->writeback_lock);
 534
 535                 if (!clear_page_dirty_for_io(page))
 536                         BUG();
 537                 ret = afs_write_back_from_locked_page(wb, page);
 538                 unlock_page(page);
 539                 put_page(page);
 540                 if (ret < 0) {
 541                         _leave(" = %d", ret);
 542                         return ret;
 543                 }
 544
 545                 wbc->nr_to_write -= ret;
 546
 547                 cond_resched();
 548         } while (index < end && wbc->nr_to_write > 0);
 549
 550         *_next = index;
 551         _leave(" = 0 [%lx]", *_next);
 552         return 0;
 553 }
 554
 555 /*
 556  * write some of the pending data back to the server
 557  */
 558 int afs_writepages(struct address_space *mapping,
 559                    struct writeback_control *wbc)
 560 {
 561         pgoff_t start, end, next;
 562         int ret;
 563
 564         _enter("");
 565
 566         if (wbc->range_cyclic) {
 567                 start = mapping->writeback_index;
 568                 end = -1;
 569                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
 570                 if (start > 0 && wbc->nr_to_write > 0 && ret == 0)
 571                         ret = afs_writepages_region(mapping, wbc, 0, start,
 572                                                     &next);
 573                 mapping->writeback_index = next;
 574         } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
 575                 end = (pgoff_t)(LLONG_MAX >> PAGE_SHIFT);
 576                 ret = afs_writepages_region(mapping, wbc, 0, end, &next);
 577                 if (wbc->nr_to_write > 0)
 578                         mapping->writeback_index = next;
 579         } else {
 580                 start = wbc->range_start >> PAGE_SHIFT;
 581                 end = wbc->range_end >> PAGE_SHIFT;
 582                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
 583         }
 584
 585         _leave(" = %d", ret);
 586         return ret;
 587 }
 588
 589 /*
 590  * completion of write to server
 591  */
 592 void afs_pages_written_back(struct afs_vnode *vnode, struct afs_call *call)
 593 {
 594         struct afs_writeback *wb = call->wb;
 595         struct pagevec pv;
 596         unsigned count, loop;
 597         pgoff_t first = call->first, last = call->last;
 598         bool free_wb;
 599
 600         _enter("{%x:%u},{%lx-%lx}",
 601                vnode->fid.vid, vnode->fid.vnode, first, last);
 602
 603         ASSERT(wb != NULL);
 604
 605         pagevec_init(&pv);
 606
 607         do {
 608                 _debug("done %lx-%lx", first, last);
 609
 610                 count = last - first + 1;
 611                 if (count > PAGEVEC_SIZE)
 612                         count = PAGEVEC_SIZE;
 613                 pv.nr = find_get_pages_contig(call->mapping, first, count,
 614                                               pv.pages);
 615                 ASSERTCMP(pv.nr, ==, count);
 616
 617                 spin_lock(&vnode->writeback_lock);
 618                 for (loop = 0; loop < count; loop++) {
 619                         struct page *page = pv.pages[loop];
 620                         end_page_writeback(page);
 621                         if (page_private(page) == (unsigned long) wb) {
 622                                 set_page_private(page, 0);
 623                                 ClearPagePrivate(page);
 624                                 wb->usage--;
 625                         }
 626                 }
 627                 free_wb = false;
 628                 if (wb->usage == 0) {
 629                         afs_unlink_writeback(wb);
 630                         free_wb = true;
 631                 }
 632                 spin_unlock(&vnode->writeback_lock);
 633                 first += count;
 634                 if (free_wb) {
 635                         afs_free_writeback(wb);
 636                         wb = NULL;
 637                 }
 638
 639                 __pagevec_release(&pv);
 640         } while (first <= last);
 641
 642         _leave("");
 643 }
 644
 645 /*
 646  * write to an AFS file
 647  */
 648 ssize_t afs_file_write(struct kiocb *iocb, struct iov_iter *from)
 649 {
 650         struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp));
 651         ssize_t result;
 652         size_t count = iov_iter_count(from);
 653
 654         _enter("{%x.%u},{%zu},",
 655                vnode->fid.vid, vnode->fid.vnode, count);
 656
 657         if (IS_SWAPFILE(&vnode->vfs_inode)) {
 658                 printk(KERN_INFO
 659                        "AFS: Attempt to write to active swap file!\n");
 660                 return -EBUSY;
 661         }
 662
 663         if (!count)
 664                 return 0;
 665
 666         result = generic_file_write_iter(iocb, from);
 667
 668         _leave(" = %zd", result);
 669         return result;
 670 }
 671
 672 /*
 673  * flush the vnode to the fileserver
 674  */
 675 int afs_writeback_all(struct afs_vnode *vnode)
 676 {
 677         struct address_space *mapping = vnode->vfs_inode.i_mapping;
 678         struct writeback_control wbc = {
 679                 .sync_mode      = WB_SYNC_ALL,
 680                 .nr_to_write    = LONG_MAX,
 681                 .range_cyclic   = 1,
 682         };
 683         int ret;
 684
 685         _enter("");
 686
 687         ret = mapping->a_ops->writepages(mapping, &wbc);
 688         __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
 689
 690         _leave(" = %d", ret);
 691         return ret;
 692 }
 693
 694 /*
 695  * flush any dirty pages for this process, and check for write errors.
 696  * - the return status from this call provides a reliable indication of
 697  *   whether any write errors occurred for this process.
 698  */
 699 int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 700 {
 701         struct inode *inode = file_inode(file);
 702         struct afs_writeback *wb, *xwb;
 703         struct afs_vnode *vnode = AFS_FS_I(inode);
 704         int ret;
 705
 706         _enter("{%x:%u},{n=%pD},%d",
 707                vnode->fid.vid, vnode->fid.vnode, file,
 708                datasync);
 709
 710         ret = file_write_and_wait_range(file, start, end);
 711         if (ret)
 712                 return ret;
 713         inode_lock(inode);
 714
 715         /* use a writeback record as a marker in the queue - when this reaches
 716          * the front of the queue, all the outstanding writes are either
 717          * completed or rejected */
 718         wb = kzalloc(sizeof(*wb), GFP_KERNEL);
 719         if (!wb) {
 720                 ret = -ENOMEM;
 721                 goto out;
 722         }
 723         wb->vnode = vnode;
 724         wb->first = 0;
 725         wb->last = -1;
 726         wb->offset_first = 0;
 727         wb->to_last = PAGE_SIZE;
 728         wb->usage = 1;
 729         wb->state = AFS_WBACK_SYNCING;
 730         init_waitqueue_head(&wb->waitq);
 731
 732         spin_lock(&vnode->writeback_lock);
 733         list_for_each_entry(xwb, &vnode->writebacks, link) {
 734                 if (xwb->state == AFS_WBACK_PENDING)
 735                         xwb->state = AFS_WBACK_CONFLICTING;
 736         }
 737         list_add_tail(&wb->link, &vnode->writebacks);
 738         spin_unlock(&vnode->writeback_lock);
 739
 740         /* push all the outstanding writebacks to the server */
 741         ret = afs_writeback_all(vnode);
 742         if (ret < 0) {
 743                 afs_put_writeback(wb);
 744                 _leave(" = %d [wb]", ret);
 745                 goto out;
 746         }
 747
 748         /* wait for the preceding writes to actually complete */
 749         ret = wait_event_interruptible(wb->waitq,
 750                                        wb->state == AFS_WBACK_COMPLETE ||
 751                                        vnode->writebacks.next == &wb->link);
 752         afs_put_writeback(wb);
 753         _leave(" = %d", ret);
 754 out:
 755         inode_unlock(inode);
 756         return ret;
 757 }
 758
 759 /*
 760  * Flush out all outstanding writes on a file opened for writing when it is
 761  * closed.
 762  */
 763 int afs_flush(struct file *file, fl_owner_t id)
 764 {
 765         _enter("");
 766
 767         if ((file->f_mode & FMODE_WRITE) == 0)
 768                 return 0;
 769
 770         return vfs_fsync(file, 0);
 771 }
 772
 773 /*
 774  * notification that a previously read-only page is about to become writable
 775  * - if it returns an error, the caller will deliver a bus error signal
 776  */
 777 int afs_page_mkwrite(struct vm_area_struct *vma, struct page *page)
 778 {
 779         struct afs_vnode *vnode = AFS_FS_I(vma->vm_file->f_mapping->host);
 780
 781         _enter("{{%x:%u}},{%lx}",
 782                vnode->fid.vid, vnode->fid.vnode, page->index);
 783
 784         /* wait for the page to be written to the cache before we allow it to
 785          * be modified */
 786 #ifdef CONFIG_AFS_FSCACHE
 787         fscache_wait_on_page_write(vnode->cache, page);
 788 #endif
 789
 790         _leave(" = 0");
 791         return 0;
 792 }