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