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 len, struct page *page)
  88 {
  89         loff_t i_size;
  90         unsigned eof;
  91         int ret;
  92
  93         _enter(",,%llu,%u", (unsigned long long)pos, len);
  94
  95         ASSERTCMP(len, <=, PAGE_CACHE_SIZE);
  96
  97         i_size = i_size_read(&vnode->vfs_inode);
  98         if (pos + len > i_size)
  99                 eof = i_size;
 100         else
 101                 eof = PAGE_CACHE_SIZE;
 102
 103         ret = afs_vnode_fetch_data(vnode, key, 0, eof, page);
 104         if (ret < 0) {
 105                 if (ret == -ENOENT) {
 106                         _debug("got NOENT from server"
 107                                " - marking file deleted and stale");
 108                         set_bit(AFS_VNODE_DELETED, &vnode->flags);
 109                         ret = -ESTALE;
 110                 }
 111         }
 112
 113         _leave(" = %d", ret);
 114         return ret;
 115 }
 116
 117 /*
 118  * prepare to perform part of a write to a page
 119  */
 120 int afs_write_begin(struct file *file, struct address_space *mapping,
 121                     loff_t pos, unsigned len, unsigned flags,
 122                     struct page **pagep, void **fsdata)
 123 {
 124         struct afs_writeback *candidate, *wb;
 125         struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode);
 126         struct page *page;
 127         struct key *key = file->private_data;
 128         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 129         unsigned to = from + len;
 130         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 131         int ret;
 132
 133         _enter("{%x:%u},{%lx},%u,%u",
 134                vnode->fid.vid, vnode->fid.vnode, index, from, to);
 135
 136         candidate = kzalloc(sizeof(*candidate), GFP_KERNEL);
 137         if (!candidate)
 138                 return -ENOMEM;
 139         candidate->vnode = vnode;
 140         candidate->first = candidate->last = index;
 141         candidate->offset_first = from;
 142         candidate->to_last = to;
 143         INIT_LIST_HEAD(&candidate->link);
 144         candidate->usage = 1;
 145         candidate->state = AFS_WBACK_PENDING;
 146         init_waitqueue_head(&candidate->waitq);
 147
 148         page = grab_cache_page_write_begin(mapping, index, flags);
 149         if (!page) {
 150                 kfree(candidate);
 151                 return -ENOMEM;
 152         }
 153         *pagep = page;
 154         /* page won't leak in error case: it eventually gets cleaned off LRU */
 155
 156         if (!PageUptodate(page)) {
 157                 _debug("not up to date");
 158                 ret = afs_fill_page(vnode, key, pos, len, page);
 159                 if (ret < 0) {
 160                         kfree(candidate);
 161                         _leave(" = %d [prep]", ret);
 162                         return ret;
 163                 }
 164                 SetPageUptodate(page);
 165         }
 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->f_dentry->d_inode);
 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         page_cache_release(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                         ClearPageUptodate(pv.pages[loop]);
 303                         if (error)
 304                                 SetPageError(pv.pages[loop]);
 305                         end_page_writeback(pv.pages[loop]);
 306                 }
 307
 308                 __pagevec_release(&pv);
 309         } while (first < last);
 310
 311         _leave("");
 312 }
 313
 314 /*
 315  * synchronously write back the locked page and any subsequent non-locked dirty
 316  * pages also covered by the same writeback record
 317  */
 318 static int afs_write_back_from_locked_page(struct afs_writeback *wb,
 319                                            struct page *primary_page)
 320 {
 321         struct page *pages[8], *page;
 322         unsigned long count;
 323         unsigned n, offset, to;
 324         pgoff_t start, first, last;
 325         int loop, ret;
 326
 327         _enter(",%lx", primary_page->index);
 328
 329         count = 1;
 330         if (!clear_page_dirty_for_io(primary_page))
 331                 BUG();
 332         if (test_set_page_writeback(primary_page))
 333                 BUG();
 334
 335         /* find all consecutive lockable dirty pages, stopping when we find a
 336          * page that is not immediately lockable, is not dirty or is missing,
 337          * or we reach the end of the range */
 338         start = primary_page->index;
 339         if (start >= wb->last)
 340                 goto no_more;
 341         start++;
 342         do {
 343                 _debug("more %lx [%lx]", start, count);
 344                 n = wb->last - start + 1;
 345                 if (n > ARRAY_SIZE(pages))
 346                         n = ARRAY_SIZE(pages);
 347                 n = find_get_pages_contig(wb->vnode->vfs_inode.i_mapping,
 348                                           start, n, pages);
 349                 _debug("fgpc %u", n);
 350                 if (n == 0)
 351                         goto no_more;
 352                 if (pages[0]->index != start) {
 353                         do {
 354                                 put_page(pages[--n]);
 355                         } while (n > 0);
 356                         goto no_more;
 357                 }
 358
 359                 for (loop = 0; loop < n; loop++) {
 360                         page = pages[loop];
 361                         if (page->index > wb->last)
 362                                 break;
 363                         if (!trylock_page(page))
 364                                 break;
 365                         if (!PageDirty(page) ||
 366                             page_private(page) != (unsigned long) wb) {
 367                                 unlock_page(page);
 368                                 break;
 369                         }
 370                         if (!clear_page_dirty_for_io(page))
 371                                 BUG();
 372                         if (test_set_page_writeback(page))
 373                                 BUG();
 374                         unlock_page(page);
 375                         put_page(page);
 376                 }
 377                 count += loop;
 378                 if (loop < n) {
 379                         for (; loop < n; loop++)
 380                                 put_page(pages[loop]);
 381                         goto no_more;
 382                 }
 383
 384                 start += loop;
 385         } while (start <= wb->last && count < 65536);
 386
 387 no_more:
 388         /* we now have a contiguous set of dirty pages, each with writeback set
 389          * and the dirty mark cleared; the first page is locked and must remain
 390          * so, all the rest are unlocked */
 391         first = primary_page->index;
 392         last = first + count - 1;
 393
 394         offset = (first == wb->first) ? wb->offset_first : 0;
 395         to = (last == wb->last) ? wb->to_last : PAGE_SIZE;
 396
 397         _debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to);
 398
 399         ret = afs_vnode_store_data(wb, first, last, offset, to);
 400         if (ret < 0) {
 401                 switch (ret) {
 402                 case -EDQUOT:
 403                 case -ENOSPC:
 404                         set_bit(AS_ENOSPC,
 405                                 &wb->vnode->vfs_inode.i_mapping->flags);
 406                         break;
 407                 case -EROFS:
 408                 case -EIO:
 409                 case -EREMOTEIO:
 410                 case -EFBIG:
 411                 case -ENOENT:
 412                 case -ENOMEDIUM:
 413                 case -ENXIO:
 414                         afs_kill_pages(wb->vnode, true, first, last);
 415                         set_bit(AS_EIO, &wb->vnode->vfs_inode.i_mapping->flags);
 416                         break;
 417                 case -EACCES:
 418                 case -EPERM:
 419                 case -ENOKEY:
 420                 case -EKEYEXPIRED:
 421                 case -EKEYREJECTED:
 422                 case -EKEYREVOKED:
 423                         afs_kill_pages(wb->vnode, false, first, last);
 424                         break;
 425                 default:
 426                         break;
 427                 }
 428         } else {
 429                 ret = count;
 430         }
 431
 432         _leave(" = %d", ret);
 433         return ret;
 434 }
 435
 436 /*
 437  * write a page back to the server
 438  * - the caller locked the page for us
 439  */
 440 int afs_writepage(struct page *page, struct writeback_control *wbc)
 441 {
 442         struct afs_writeback *wb;
 443         int ret;
 444
 445         _enter("{%lx},", page->index);
 446
 447         wb = (struct afs_writeback *) page_private(page);
 448         ASSERT(wb != NULL);
 449
 450         ret = afs_write_back_from_locked_page(wb, page);
 451         unlock_page(page);
 452         if (ret < 0) {
 453                 _leave(" = %d", ret);
 454                 return 0;
 455         }
 456
 457         wbc->nr_to_write -= ret;
 458
 459         _leave(" = 0");
 460         return 0;
 461 }
 462
 463 /*
 464  * write a region of pages back to the server
 465  */
 466 static int afs_writepages_region(struct address_space *mapping,
 467                                  struct writeback_control *wbc,
 468                                  pgoff_t index, pgoff_t end, pgoff_t *_next)
 469 {
 470         struct afs_writeback *wb;
 471         struct page *page;
 472         int ret, n;
 473
 474         _enter(",,%lx,%lx,", index, end);
 475
 476         do {
 477                 n = find_get_pages_tag(mapping, &index, PAGECACHE_TAG_DIRTY,
 478                                        1, &page);
 479                 if (!n)
 480                         break;
 481
 482                 _debug("wback %lx", page->index);
 483
 484                 if (page->index > end) {
 485                         *_next = index;
 486                         page_cache_release(page);
 487                         _leave(" = 0 [%lx]", *_next);
 488                         return 0;
 489                 }
 490
 491                 /* at this point we hold neither mapping->tree_lock nor lock on
 492                  * the page itself: the page may be truncated or invalidated
 493                  * (changing page->mapping to NULL), or even swizzled back from
 494                  * swapper_space to tmpfs file mapping
 495                  */
 496                 lock_page(page);
 497
 498                 if (page->mapping != mapping) {
 499                         unlock_page(page);
 500                         page_cache_release(page);
 501                         continue;
 502                 }
 503
 504                 if (wbc->sync_mode != WB_SYNC_NONE)
 505                         wait_on_page_writeback(page);
 506
 507                 if (PageWriteback(page) || !PageDirty(page)) {
 508                         unlock_page(page);
 509                         continue;
 510                 }
 511
 512                 wb = (struct afs_writeback *) page_private(page);
 513                 ASSERT(wb != NULL);
 514
 515                 spin_lock(&wb->vnode->writeback_lock);
 516                 wb->state = AFS_WBACK_WRITING;
 517                 spin_unlock(&wb->vnode->writeback_lock);
 518
 519                 ret = afs_write_back_from_locked_page(wb, page);
 520                 unlock_page(page);
 521                 page_cache_release(page);
 522                 if (ret < 0) {
 523                         _leave(" = %d", ret);
 524                         return ret;
 525                 }
 526
 527                 wbc->nr_to_write -= ret;
 528
 529                 cond_resched();
 530         } while (index < end && wbc->nr_to_write > 0);
 531
 532         *_next = index;
 533         _leave(" = 0 [%lx]", *_next);
 534         return 0;
 535 }
 536
 537 /*
 538  * write some of the pending data back to the server
 539  */
 540 int afs_writepages(struct address_space *mapping,
 541                    struct writeback_control *wbc)
 542 {
 543         pgoff_t start, end, next;
 544         int ret;
 545
 546         _enter("");
 547
 548         if (wbc->range_cyclic) {
 549                 start = mapping->writeback_index;
 550                 end = -1;
 551                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
 552                 if (start > 0 && wbc->nr_to_write > 0 && ret == 0)
 553                         ret = afs_writepages_region(mapping, wbc, 0, start,
 554                                                     &next);
 555                 mapping->writeback_index = next;
 556         } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
 557                 end = (pgoff_t)(LLONG_MAX >> PAGE_CACHE_SHIFT);
 558                 ret = afs_writepages_region(mapping, wbc, 0, end, &next);
 559                 if (wbc->nr_to_write > 0)
 560                         mapping->writeback_index = next;
 561         } else {
 562                 start = wbc->range_start >> PAGE_CACHE_SHIFT;
 563                 end = wbc->range_end >> PAGE_CACHE_SHIFT;
 564                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
 565         }
 566
 567         _leave(" = %d", ret);
 568         return ret;
 569 }
 570
 571 /*
 572  * completion of write to server
 573  */
 574 void afs_pages_written_back(struct afs_vnode *vnode, struct afs_call *call)
 575 {
 576         struct afs_writeback *wb = call->wb;
 577         struct pagevec pv;
 578         unsigned count, loop;
 579         pgoff_t first = call->first, last = call->last;
 580         bool free_wb;
 581
 582         _enter("{%x:%u},{%lx-%lx}",
 583                vnode->fid.vid, vnode->fid.vnode, first, last);
 584
 585         ASSERT(wb != NULL);
 586
 587         pagevec_init(&pv, 0);
 588
 589         do {
 590                 _debug("done %lx-%lx", first, last);
 591
 592                 count = last - first + 1;
 593                 if (count > PAGEVEC_SIZE)
 594                         count = PAGEVEC_SIZE;
 595                 pv.nr = find_get_pages_contig(call->mapping, first, count,
 596                                               pv.pages);
 597                 ASSERTCMP(pv.nr, ==, count);
 598
 599                 spin_lock(&vnode->writeback_lock);
 600                 for (loop = 0; loop < count; loop++) {
 601                         struct page *page = pv.pages[loop];
 602                         end_page_writeback(page);
 603                         if (page_private(page) == (unsigned long) wb) {
 604                                 set_page_private(page, 0);
 605                                 ClearPagePrivate(page);
 606                                 wb->usage--;
 607                         }
 608                 }
 609                 free_wb = false;
 610                 if (wb->usage == 0) {
 611                         afs_unlink_writeback(wb);
 612                         free_wb = true;
 613                 }
 614                 spin_unlock(&vnode->writeback_lock);
 615                 first += count;
 616                 if (free_wb) {
 617                         afs_free_writeback(wb);
 618                         wb = NULL;
 619                 }
 620
 621                 __pagevec_release(&pv);
 622         } while (first <= last);
 623
 624         _leave("");
 625 }
 626
 627 /*
 628  * write to an AFS file
 629  */
 630 ssize_t afs_file_write(struct kiocb *iocb, const struct iovec *iov,
 631                        unsigned long nr_segs, loff_t pos)
 632 {
 633         struct dentry *dentry = iocb->ki_filp->f_path.dentry;
 634         struct afs_vnode *vnode = AFS_FS_I(dentry->d_inode);
 635         ssize_t result;
 636         size_t count = iov_length(iov, nr_segs);
 637
 638         _enter("{%x.%u},{%zu},%lu,",
 639                vnode->fid.vid, vnode->fid.vnode, count, nr_segs);
 640
 641         if (IS_SWAPFILE(&vnode->vfs_inode)) {
 642                 printk(KERN_INFO
 643                        "AFS: Attempt to write to active swap file!\n");
 644                 return -EBUSY;
 645         }
 646
 647         if (!count)
 648                 return 0;
 649
 650         result = generic_file_aio_write(iocb, iov, nr_segs, pos);
 651         if (IS_ERR_VALUE(result)) {
 652                 _leave(" = %zd", result);
 653                 return result;
 654         }
 655
 656         _leave(" = %zd", result);
 657         return result;
 658 }
 659
 660 /*
 661  * flush the vnode to the fileserver
 662  */
 663 int afs_writeback_all(struct afs_vnode *vnode)
 664 {
 665         struct address_space *mapping = vnode->vfs_inode.i_mapping;
 666         struct writeback_control wbc = {
 667                 .sync_mode      = WB_SYNC_ALL,
 668                 .nr_to_write    = LONG_MAX,
 669                 .range_cyclic   = 1,
 670         };
 671         int ret;
 672
 673         _enter("");
 674
 675         ret = mapping->a_ops->writepages(mapping, &wbc);
 676         __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
 677
 678         _leave(" = %d", ret);
 679         return ret;
 680 }
 681
 682 /*
 683  * flush any dirty pages for this process, and check for write errors.
 684  * - the return status from this call provides a reliable indication of
 685  *   whether any write errors occurred for this process.
 686  */
 687 int afs_fsync(struct file *file, int datasync)
 688 {
 689         struct dentry *dentry = file->f_path.dentry;
 690         struct afs_writeback *wb, *xwb;
 691         struct afs_vnode *vnode = AFS_FS_I(dentry->d_inode);
 692         int ret;
 693
 694         _enter("{%x:%u},{n=%s},%d",
 695                vnode->fid.vid, vnode->fid.vnode, dentry->d_name.name,
 696                datasync);
 697
 698         /* use a writeback record as a marker in the queue - when this reaches
 699          * the front of the queue, all the outstanding writes are either
 700          * completed or rejected */
 701         wb = kzalloc(sizeof(*wb), GFP_KERNEL);
 702         if (!wb)
 703                 return -ENOMEM;
 704         wb->vnode = vnode;
 705         wb->first = 0;
 706         wb->last = -1;
 707         wb->offset_first = 0;
 708         wb->to_last = PAGE_SIZE;
 709         wb->usage = 1;
 710         wb->state = AFS_WBACK_SYNCING;
 711         init_waitqueue_head(&wb->waitq);
 712
 713         spin_lock(&vnode->writeback_lock);
 714         list_for_each_entry(xwb, &vnode->writebacks, link) {
 715                 if (xwb->state == AFS_WBACK_PENDING)
 716                         xwb->state = AFS_WBACK_CONFLICTING;
 717         }
 718         list_add_tail(&wb->link, &vnode->writebacks);
 719         spin_unlock(&vnode->writeback_lock);
 720
 721         /* push all the outstanding writebacks to the server */
 722         ret = afs_writeback_all(vnode);
 723         if (ret < 0) {
 724                 afs_put_writeback(wb);
 725                 _leave(" = %d [wb]", ret);
 726                 return ret;
 727         }
 728
 729         /* wait for the preceding writes to actually complete */
 730         ret = wait_event_interruptible(wb->waitq,
 731                                        wb->state == AFS_WBACK_COMPLETE ||
 732                                        vnode->writebacks.next == &wb->link);
 733         afs_put_writeback(wb);
 734         _leave(" = %d", ret);
 735         return ret;
 736 }
 737
 738 /*
 739  * notification that a previously read-only page is about to become writable
 740  * - if it returns an error, the caller will deliver a bus error signal
 741  */
 742 int afs_page_mkwrite(struct vm_area_struct *vma, struct page *page)
 743 {
 744         struct afs_vnode *vnode = AFS_FS_I(vma->vm_file->f_mapping->host);
 745
 746         _enter("{{%x:%u}},{%lx}",
 747                vnode->fid.vid, vnode->fid.vnode, page->index);
 748
 749         /* wait for the page to be written to the cache before we allow it to
 750          * be modified */
 751 #ifdef CONFIG_AFS_FSCACHE
 752         fscache_wait_on_page_write(vnode->cache, page);
 753 #endif
 754
 755         _leave(" = 0");
 756         return 0;
 757 }