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
  12 #include <linux/backing-dev.h>
  13 #include <linux/slab.h>
  14 #include <linux/fs.h>
  15 #include <linux/pagemap.h>
  16 #include <linux/writeback.h>
  17 #include <linux/pagevec.h>
  18 #include "internal.h"
  19
  20 /*
  21  * mark a page as having been made dirty and thus needing writeback
  22  */
  23 int afs_set_page_dirty(struct page *page)
  24 {
  25         _enter("");
  26         return __set_page_dirty_nobuffers(page);
  27 }
  28
  29 /*
  30  * partly or wholly fill a page that's under preparation for writing
  31  */
  32 static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
  33                          loff_t pos, unsigned int len, struct page *page)
  34 {
  35         struct afs_read *req;
  36         int ret;
  37
  38         _enter(",,%llu", (unsigned long long)pos);
  39
  40         req = kzalloc(sizeof(struct afs_read) + sizeof(struct page *),
  41                       GFP_KERNEL);
  42         if (!req)
  43                 return -ENOMEM;
  44
  45         refcount_set(&req->usage, 1);
  46         req->pos = pos;
  47         req->len = len;
  48         req->nr_pages = 1;
  49         req->pages = req->array;
  50         req->pages[0] = page;
  51         get_page(page);
  52
  53         ret = afs_fetch_data(vnode, key, req);
  54         afs_put_read(req);
  55         if (ret < 0) {
  56                 if (ret == -ENOENT) {
  57                         _debug("got NOENT from server"
  58                                " - marking file deleted and stale");
  59                         set_bit(AFS_VNODE_DELETED, &vnode->flags);
  60                         ret = -ESTALE;
  61                 }
  62         }
  63
  64         _leave(" = %d", ret);
  65         return ret;
  66 }
  67
  68 /*
  69  * prepare to perform part of a write to a page
  70  */
  71 int afs_write_begin(struct file *file, struct address_space *mapping,
  72                     loff_t pos, unsigned len, unsigned flags,
  73                     struct page **pagep, void **fsdata)
  74 {
  75         struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
  76         struct page *page;
  77         struct key *key = afs_file_key(file);
  78         unsigned long priv;
  79         unsigned f, from = pos & (PAGE_SIZE - 1);
  80         unsigned t, to = from + len;
  81         pgoff_t index = pos >> PAGE_SHIFT;
  82         int ret;
  83
  84         _enter("{%x:%u},{%lx},%u,%u",
  85                vnode->fid.vid, vnode->fid.vnode, index, from, to);
  86
  87         /* We want to store information about how much of a page is altered in
  88          * page->private.
  89          */
  90         BUILD_BUG_ON(PAGE_SIZE > 32768 && sizeof(page->private) < 8);
  91
  92         page = grab_cache_page_write_begin(mapping, index, flags);
  93         if (!page)
  94                 return -ENOMEM;
  95
  96         if (!PageUptodate(page) && len != PAGE_SIZE) {
  97                 ret = afs_fill_page(vnode, key, pos & PAGE_MASK, PAGE_SIZE, page);
  98                 if (ret < 0) {
  99                         unlock_page(page);
 100                         put_page(page);
 101                         _leave(" = %d [prep]", ret);
 102                         return ret;
 103                 }
 104                 SetPageUptodate(page);
 105         }
 106
 107         /* page won't leak in error case: it eventually gets cleaned off LRU */
 108         *pagep = page;
 109
 110 try_again:
 111         /* See if this page is already partially written in a way that we can
 112          * merge the new write with.
 113          */
 114         t = f = 0;
 115         if (PagePrivate(page)) {
 116                 priv = page_private(page);
 117                 f = priv & AFS_PRIV_MAX;
 118                 t = priv >> AFS_PRIV_SHIFT;
 119                 ASSERTCMP(f, <=, t);
 120         }
 121
 122         if (f != t) {
 123                 if (PageWriteback(page)) {
 124                         trace_afs_page_dirty(vnode, tracepoint_string("alrdy"),
 125                                              page->index, priv);
 126                         goto flush_conflicting_write;
 127                 }
 128                 /* If the file is being filled locally, allow inter-write
 129                  * spaces to be merged into writes.  If it's not, only write
 130                  * back what the user gives us.
 131                  */
 132                 if (!test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags) &&
 133                     (to < f || from > t))
 134                         goto flush_conflicting_write;
 135                 if (from < f)
 136                         f = from;
 137                 if (to > t)
 138                         t = to;
 139         } else {
 140                 f = from;
 141                 t = to;
 142         }
 143
 144         priv = (unsigned long)t << AFS_PRIV_SHIFT;
 145         priv |= f;
 146         trace_afs_page_dirty(vnode, tracepoint_string("begin"),
 147                              page->index, priv);
 148         SetPagePrivate(page);
 149         set_page_private(page, priv);
 150         _leave(" = 0");
 151         return 0;
 152
 153         /* The previous write and this write aren't adjacent or overlapping, so
 154          * flush the page out.
 155          */
 156 flush_conflicting_write:
 157         _debug("flush conflict");
 158         ret = write_one_page(page);
 159         if (ret < 0) {
 160                 _leave(" = %d", ret);
 161                 return ret;
 162         }
 163
 164         ret = lock_page_killable(page);
 165         if (ret < 0) {
 166                 _leave(" = %d", ret);
 167                 return ret;
 168         }
 169         goto try_again;
 170 }
 171
 172 /*
 173  * finalise part of a write to a page
 174  */
 175 int afs_write_end(struct file *file, struct address_space *mapping,
 176                   loff_t pos, unsigned len, unsigned copied,
 177                   struct page *page, void *fsdata)
 178 {
 179         struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
 180         struct key *key = afs_file_key(file);
 181         loff_t i_size, maybe_i_size;
 182         int ret;
 183
 184         _enter("{%x:%u},{%lx}",
 185                vnode->fid.vid, vnode->fid.vnode, page->index);
 186
 187         maybe_i_size = pos + copied;
 188
 189         i_size = i_size_read(&vnode->vfs_inode);
 190         if (maybe_i_size > i_size) {
 191                 spin_lock(&vnode->wb_lock);
 192                 i_size = i_size_read(&vnode->vfs_inode);
 193                 if (maybe_i_size > i_size)
 194                         i_size_write(&vnode->vfs_inode, maybe_i_size);
 195                 spin_unlock(&vnode->wb_lock);
 196         }
 197
 198         if (!PageUptodate(page)) {
 199                 if (copied < len) {
 200                         /* Try and load any missing data from the server.  The
 201                          * unmarshalling routine will take care of clearing any
 202                          * bits that are beyond the EOF.
 203                          */
 204                         ret = afs_fill_page(vnode, key, pos + copied,
 205                                             len - copied, page);
 206                         if (ret < 0)
 207                                 goto out;
 208                 }
 209                 SetPageUptodate(page);
 210         }
 211
 212         set_page_dirty(page);
 213         if (PageDirty(page))
 214                 _debug("dirtied");
 215         ret = copied;
 216
 217 out:
 218         unlock_page(page);
 219         put_page(page);
 220         return ret;
 221 }
 222
 223 /*
 224  * kill all the pages in the given range
 225  */
 226 static void afs_kill_pages(struct address_space *mapping,
 227                            pgoff_t first, pgoff_t last)
 228 {
 229         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 230         struct pagevec pv;
 231         unsigned count, loop;
 232
 233         _enter("{%x:%u},%lx-%lx",
 234                vnode->fid.vid, vnode->fid.vnode, first, last);
 235
 236         pagevec_init(&pv);
 237
 238         do {
 239                 _debug("kill %lx-%lx", first, last);
 240
 241                 count = last - first + 1;
 242                 if (count > PAGEVEC_SIZE)
 243                         count = PAGEVEC_SIZE;
 244                 pv.nr = find_get_pages_contig(mapping, first, count, pv.pages);
 245                 ASSERTCMP(pv.nr, ==, count);
 246
 247                 for (loop = 0; loop < count; loop++) {
 248                         struct page *page = pv.pages[loop];
 249                         ClearPageUptodate(page);
 250                         SetPageError(page);
 251                         end_page_writeback(page);
 252                         if (page->index >= first)
 253                                 first = page->index + 1;
 254                         lock_page(page);
 255                         generic_error_remove_page(mapping, page);
 256                         unlock_page(page);
 257                 }
 258
 259                 __pagevec_release(&pv);
 260         } while (first <= last);
 261
 262         _leave("");
 263 }
 264
 265 /*
 266  * Redirty all the pages in a given range.
 267  */
 268 static void afs_redirty_pages(struct writeback_control *wbc,
 269                               struct address_space *mapping,
 270                               pgoff_t first, pgoff_t last)
 271 {
 272         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 273         struct pagevec pv;
 274         unsigned count, loop;
 275
 276         _enter("{%x:%u},%lx-%lx",
 277                vnode->fid.vid, vnode->fid.vnode, first, last);
 278
 279         pagevec_init(&pv);
 280
 281         do {
 282                 _debug("redirty %lx-%lx", first, last);
 283
 284                 count = last - first + 1;
 285                 if (count > PAGEVEC_SIZE)
 286                         count = PAGEVEC_SIZE;
 287                 pv.nr = find_get_pages_contig(mapping, first, count, pv.pages);
 288                 ASSERTCMP(pv.nr, ==, count);
 289
 290                 for (loop = 0; loop < count; loop++) {
 291                         struct page *page = pv.pages[loop];
 292
 293                         redirty_page_for_writepage(wbc, page);
 294                         end_page_writeback(page);
 295                         if (page->index >= first)
 296                                 first = page->index + 1;
 297                 }
 298
 299                 __pagevec_release(&pv);
 300         } while (first <= last);
 301
 302         _leave("");
 303 }
 304
 305 /*
 306  * write to a file
 307  */
 308 static int afs_store_data(struct address_space *mapping,
 309                           pgoff_t first, pgoff_t last,
 310                           unsigned offset, unsigned to)
 311 {
 312         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 313         struct afs_fs_cursor fc;
 314         struct afs_wb_key *wbk = NULL;
 315         struct list_head *p;
 316         int ret = -ENOKEY, ret2;
 317
 318         _enter("%s{%x:%u.%u},%lx,%lx,%x,%x",
 319                vnode->volume->name,
 320                vnode->fid.vid,
 321                vnode->fid.vnode,
 322                vnode->fid.unique,
 323                first, last, offset, to);
 324
 325         spin_lock(&vnode->wb_lock);
 326         p = vnode->wb_keys.next;
 327
 328         /* Iterate through the list looking for a valid key to use. */
 329 try_next_key:
 330         while (p != &vnode->wb_keys) {
 331                 wbk = list_entry(p, struct afs_wb_key, vnode_link);
 332                 _debug("wbk %u", key_serial(wbk->key));
 333                 ret2 = key_validate(wbk->key);
 334                 if (ret2 == 0)
 335                         goto found_key;
 336                 if (ret == -ENOKEY)
 337                         ret = ret2;
 338                 p = p->next;
 339         }
 340
 341         spin_unlock(&vnode->wb_lock);
 342         afs_put_wb_key(wbk);
 343         _leave(" = %d [no keys]", ret);
 344         return ret;
 345
 346 found_key:
 347         refcount_inc(&wbk->usage);
 348         spin_unlock(&vnode->wb_lock);
 349
 350         _debug("USE WB KEY %u", key_serial(wbk->key));
 351
 352         ret = -ERESTARTSYS;
 353         if (afs_begin_vnode_operation(&fc, vnode, wbk->key)) {
 354                 while (afs_select_fileserver(&fc)) {
 355                         fc.cb_break = afs_calc_vnode_cb_break(vnode);
 356                         afs_fs_store_data(&fc, mapping, first, last, offset, to);
 357                 }
 358
 359                 afs_check_for_remote_deletion(&fc, fc.vnode);
 360                 afs_vnode_commit_status(&fc, vnode, fc.cb_break);
 361                 ret = afs_end_vnode_operation(&fc);
 362         }
 363
 364         switch (ret) {
 365         case 0:
 366                 afs_stat_v(vnode, n_stores);
 367                 atomic_long_add((last * PAGE_SIZE + to) -
 368                                 (first * PAGE_SIZE + offset),
 369                                 &afs_v2net(vnode)->n_store_bytes);
 370                 break;
 371         case -EACCES:
 372         case -EPERM:
 373         case -ENOKEY:
 374         case -EKEYEXPIRED:
 375         case -EKEYREJECTED:
 376         case -EKEYREVOKED:
 377                 _debug("next");
 378                 spin_lock(&vnode->wb_lock);
 379                 p = wbk->vnode_link.next;
 380                 afs_put_wb_key(wbk);
 381                 goto try_next_key;
 382         }
 383
 384         afs_put_wb_key(wbk);
 385         _leave(" = %d", ret);
 386         return ret;
 387 }
 388
 389 /*
 390  * Synchronously write back the locked page and any subsequent non-locked dirty
 391  * pages.
 392  */
 393 static int afs_write_back_from_locked_page(struct address_space *mapping,
 394                                            struct writeback_control *wbc,
 395                                            struct page *primary_page,
 396                                            pgoff_t final_page)
 397 {
 398         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 399         struct page *pages[8], *page;
 400         unsigned long count, priv;
 401         unsigned n, offset, to, f, t;
 402         pgoff_t start, first, last;
 403         int loop, ret;
 404
 405         _enter(",%lx", primary_page->index);
 406
 407         count = 1;
 408         if (test_set_page_writeback(primary_page))
 409                 BUG();
 410
 411         /* Find all consecutive lockable dirty pages that have contiguous
 412          * written regions, stopping when we find a page that is not
 413          * immediately lockable, is not dirty or is missing, or we reach the
 414          * end of the range.
 415          */
 416         start = primary_page->index;
 417         priv = page_private(primary_page);
 418         offset = priv & AFS_PRIV_MAX;
 419         to = priv >> AFS_PRIV_SHIFT;
 420         trace_afs_page_dirty(vnode, tracepoint_string("store"),
 421                              primary_page->index, priv);
 422
 423         WARN_ON(offset == to);
 424         if (offset == to)
 425                 trace_afs_page_dirty(vnode, tracepoint_string("WARN"),
 426                                      primary_page->index, priv);
 427
 428         if (start >= final_page ||
 429             (to < PAGE_SIZE && !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)))
 430                 goto no_more;
 431
 432         start++;
 433         do {
 434                 _debug("more %lx [%lx]", start, count);
 435                 n = final_page - start + 1;
 436                 if (n > ARRAY_SIZE(pages))
 437                         n = ARRAY_SIZE(pages);
 438                 n = find_get_pages_contig(mapping, start, ARRAY_SIZE(pages), pages);
 439                 _debug("fgpc %u", n);
 440                 if (n == 0)
 441                         goto no_more;
 442                 if (pages[0]->index != start) {
 443                         do {
 444                                 put_page(pages[--n]);
 445                         } while (n > 0);
 446                         goto no_more;
 447                 }
 448
 449                 for (loop = 0; loop < n; loop++) {
 450                         page = pages[loop];
 451                         if (to != PAGE_SIZE &&
 452                             !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags))
 453                                 break;
 454                         if (page->index > final_page)
 455                                 break;
 456                         if (!trylock_page(page))
 457                                 break;
 458                         if (!PageDirty(page) || PageWriteback(page)) {
 459                                 unlock_page(page);
 460                                 break;
 461                         }
 462
 463                         priv = page_private(page);
 464                         f = priv & AFS_PRIV_MAX;
 465                         t = priv >> AFS_PRIV_SHIFT;
 466                         if (f != 0 &&
 467                             !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)) {
 468                                 unlock_page(page);
 469                                 break;
 470                         }
 471                         to = t;
 472
 473                         trace_afs_page_dirty(vnode, tracepoint_string("store+"),
 474                                              page->index, priv);
 475
 476                         if (!clear_page_dirty_for_io(page))
 477                                 BUG();
 478                         if (test_set_page_writeback(page))
 479                                 BUG();
 480                         unlock_page(page);
 481                         put_page(page);
 482                 }
 483                 count += loop;
 484                 if (loop < n) {
 485                         for (; loop < n; loop++)
 486                                 put_page(pages[loop]);
 487                         goto no_more;
 488                 }
 489
 490                 start += loop;
 491         } while (start <= final_page && count < 65536);
 492
 493 no_more:
 494         /* We now have a contiguous set of dirty pages, each with writeback
 495          * set; the first page is still locked at this point, but all the rest
 496          * have been unlocked.
 497          */
 498         unlock_page(primary_page);
 499
 500         first = primary_page->index;
 501         last = first + count - 1;
 502
 503         _debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to);
 504
 505         ret = afs_store_data(mapping, first, last, offset, to);
 506         switch (ret) {
 507         case 0:
 508                 ret = count;
 509                 break;
 510
 511         default:
 512                 pr_notice("kAFS: Unexpected error from FS.StoreData %d\n", ret);
 513                 /* Fall through */
 514         case -EACCES:
 515         case -EPERM:
 516         case -ENOKEY:
 517         case -EKEYEXPIRED:
 518         case -EKEYREJECTED:
 519         case -EKEYREVOKED:
 520                 afs_redirty_pages(wbc, mapping, first, last);
 521                 mapping_set_error(mapping, ret);
 522                 break;
 523
 524         case -EDQUOT:
 525         case -ENOSPC:
 526                 afs_redirty_pages(wbc, mapping, first, last);
 527                 mapping_set_error(mapping, -ENOSPC);
 528                 break;
 529
 530         case -EROFS:
 531         case -EIO:
 532         case -EREMOTEIO:
 533         case -EFBIG:
 534         case -ENOENT:
 535         case -ENOMEDIUM:
 536         case -ENXIO:
 537                 afs_kill_pages(mapping, first, last);
 538                 mapping_set_error(mapping, ret);
 539                 break;
 540         }
 541
 542         _leave(" = %d", ret);
 543         return ret;
 544 }
 545
 546 /*
 547  * write a page back to the server
 548  * - the caller locked the page for us
 549  */
 550 int afs_writepage(struct page *page, struct writeback_control *wbc)
 551 {
 552         int ret;
 553
 554         _enter("{%lx},", page->index);
 555
 556         ret = afs_write_back_from_locked_page(page->mapping, wbc, page,
 557                                               wbc->range_end >> PAGE_SHIFT);
 558         if (ret < 0) {
 559                 _leave(" = %d", ret);
 560                 return 0;
 561         }
 562
 563         wbc->nr_to_write -= ret;
 564
 565         _leave(" = 0");
 566         return 0;
 567 }
 568
 569 /*
 570  * write a region of pages back to the server
 571  */
 572 static int afs_writepages_region(struct address_space *mapping,
 573                                  struct writeback_control *wbc,
 574                                  pgoff_t index, pgoff_t end, pgoff_t *_next)
 575 {
 576         struct page *page;
 577         int ret, n;
 578
 579         _enter(",,%lx,%lx,", index, end);
 580
 581         do {
 582                 n = find_get_pages_range_tag(mapping, &index, end,
 583                                         PAGECACHE_TAG_DIRTY, 1, &page);
 584                 if (!n)
 585                         break;
 586
 587                 _debug("wback %lx", page->index);
 588
 589                 /*
 590                  * at this point we hold neither the i_pages lock nor the
 591                  * page lock: the page may be truncated or invalidated
 592                  * (changing page->mapping to NULL), or even swizzled
 593                  * back from swapper_space to tmpfs file mapping
 594                  */
 595                 ret = lock_page_killable(page);
 596                 if (ret < 0) {
 597                         put_page(page);
 598                         _leave(" = %d", ret);
 599                         return ret;
 600                 }
 601
 602                 if (page->mapping != mapping || !PageDirty(page)) {
 603                         unlock_page(page);
 604                         put_page(page);
 605                         continue;
 606                 }
 607
 608                 if (PageWriteback(page)) {
 609                         unlock_page(page);
 610                         if (wbc->sync_mode != WB_SYNC_NONE)
 611                                 wait_on_page_writeback(page);
 612                         put_page(page);
 613                         continue;
 614                 }
 615
 616                 if (!clear_page_dirty_for_io(page))
 617                         BUG();
 618                 ret = afs_write_back_from_locked_page(mapping, wbc, page, end);
 619                 put_page(page);
 620                 if (ret < 0) {
 621                         _leave(" = %d", ret);
 622                         return ret;
 623                 }
 624
 625                 wbc->nr_to_write -= ret;
 626
 627                 cond_resched();
 628         } while (index < end && wbc->nr_to_write > 0);
 629
 630         *_next = index;
 631         _leave(" = 0 [%lx]", *_next);
 632         return 0;
 633 }
 634
 635 /*
 636  * write some of the pending data back to the server
 637  */
 638 int afs_writepages(struct address_space *mapping,
 639                    struct writeback_control *wbc)
 640 {
 641         pgoff_t start, end, next;
 642         int ret;
 643
 644         _enter("");
 645
 646         if (wbc->range_cyclic) {
 647                 start = mapping->writeback_index;
 648                 end = -1;
 649                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
 650                 if (start > 0 && wbc->nr_to_write > 0 && ret == 0)
 651                         ret = afs_writepages_region(mapping, wbc, 0, start,
 652                                                     &next);
 653                 mapping->writeback_index = next;
 654         } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
 655                 end = (pgoff_t)(LLONG_MAX >> PAGE_SHIFT);
 656                 ret = afs_writepages_region(mapping, wbc, 0, end, &next);
 657                 if (wbc->nr_to_write > 0)
 658                         mapping->writeback_index = next;
 659         } else {
 660                 start = wbc->range_start >> PAGE_SHIFT;
 661                 end = wbc->range_end >> PAGE_SHIFT;
 662                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
 663         }
 664
 665         _leave(" = %d", ret);
 666         return ret;
 667 }
 668
 669 /*
 670  * completion of write to server
 671  */
 672 void afs_pages_written_back(struct afs_vnode *vnode, struct afs_call *call)
 673 {
 674         struct pagevec pv;
 675         unsigned long priv;
 676         unsigned count, loop;
 677         pgoff_t first = call->first, last = call->last;
 678
 679         _enter("{%x:%u},{%lx-%lx}",
 680                vnode->fid.vid, vnode->fid.vnode, first, last);
 681
 682         pagevec_init(&pv);
 683
 684         do {
 685                 _debug("done %lx-%lx", first, last);
 686
 687                 count = last - first + 1;
 688                 if (count > PAGEVEC_SIZE)
 689                         count = PAGEVEC_SIZE;
 690                 pv.nr = find_get_pages_contig(vnode->vfs_inode.i_mapping,
 691                                               first, count, pv.pages);
 692                 ASSERTCMP(pv.nr, ==, count);
 693
 694                 for (loop = 0; loop < count; loop++) {
 695                         priv = page_private(pv.pages[loop]);
 696                         trace_afs_page_dirty(vnode, tracepoint_string("clear"),
 697                                              pv.pages[loop]->index, priv);
 698                         set_page_private(pv.pages[loop], 0);
 699                         end_page_writeback(pv.pages[loop]);
 700                 }
 701                 first += count;
 702                 __pagevec_release(&pv);
 703         } while (first <= last);
 704
 705         afs_prune_wb_keys(vnode);
 706         _leave("");
 707 }
 708
 709 /*
 710  * write to an AFS file
 711  */
 712 ssize_t afs_file_write(struct kiocb *iocb, struct iov_iter *from)
 713 {
 714         struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp));
 715         ssize_t result;
 716         size_t count = iov_iter_count(from);
 717
 718         _enter("{%x.%u},{%zu},",
 719                vnode->fid.vid, vnode->fid.vnode, count);
 720
 721         if (IS_SWAPFILE(&vnode->vfs_inode)) {
 722                 printk(KERN_INFO
 723                        "AFS: Attempt to write to active swap file!\n");
 724                 return -EBUSY;
 725         }
 726
 727         if (!count)
 728                 return 0;
 729
 730         result = generic_file_write_iter(iocb, from);
 731
 732         _leave(" = %zd", result);
 733         return result;
 734 }
 735
 736 /*
 737  * flush any dirty pages for this process, and check for write errors.
 738  * - the return status from this call provides a reliable indication of
 739  *   whether any write errors occurred for this process.
 740  */
 741 int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 742 {
 743         struct inode *inode = file_inode(file);
 744         struct afs_vnode *vnode = AFS_FS_I(inode);
 745
 746         _enter("{%x:%u},{n=%pD},%d",
 747                vnode->fid.vid, vnode->fid.vnode, file,
 748                datasync);
 749
 750         return file_write_and_wait_range(file, start, end);
 751 }
 752
 753 /*
 754  * notification that a previously read-only page is about to become writable
 755  * - if it returns an error, the caller will deliver a bus error signal
 756  */
 757 vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
 758 {
 759         struct file *file = vmf->vma->vm_file;
 760         struct inode *inode = file_inode(file);
 761         struct afs_vnode *vnode = AFS_FS_I(inode);
 762         unsigned long priv;
 763
 764         _enter("{{%x:%u}},{%lx}",
 765                vnode->fid.vid, vnode->fid.vnode, vmf->page->index);
 766
 767         sb_start_pagefault(inode->i_sb);
 768
 769         /* Wait for the page to be written to the cache before we allow it to
 770          * be modified.  We then assume the entire page will need writing back.
 771          */
 772 #ifdef CONFIG_AFS_FSCACHE
 773         fscache_wait_on_page_write(vnode->cache, vmf->page);
 774 #endif
 775
 776         if (PageWriteback(vmf->page) &&
 777             wait_on_page_bit_killable(vmf->page, PG_writeback) < 0)
 778                 return VM_FAULT_RETRY;
 779
 780         if (lock_page_killable(vmf->page) < 0)
 781                 return VM_FAULT_RETRY;
 782
 783         /* We mustn't change page->private until writeback is complete as that
 784          * details the portion of the page we need to write back and we might
 785          * need to redirty the page if there's a problem.
 786          */
 787         wait_on_page_writeback(vmf->page);
 788
 789         priv = (unsigned long)PAGE_SIZE << AFS_PRIV_SHIFT; /* To */
 790         priv |= 0; /* From */
 791         trace_afs_page_dirty(vnode, tracepoint_string("mkwrite"),
 792                              vmf->page->index, priv);
 793         SetPagePrivate(vmf->page);
 794         set_page_private(vmf->page, priv);
 795
 796         sb_end_pagefault(inode->i_sb);
 797         return VM_FAULT_LOCKED;
 798 }
 799
 800 /*
 801  * Prune the keys cached for writeback.  The caller must hold vnode->wb_lock.
 802  */
 803 void afs_prune_wb_keys(struct afs_vnode *vnode)
 804 {
 805         LIST_HEAD(graveyard);
 806         struct afs_wb_key *wbk, *tmp;
 807
 808         /* Discard unused keys */
 809         spin_lock(&vnode->wb_lock);
 810
 811         if (!mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_WRITEBACK) &&
 812             !mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_DIRTY)) {
 813                 list_for_each_entry_safe(wbk, tmp, &vnode->wb_keys, vnode_link) {
 814                         if (refcount_read(&wbk->usage) == 1)
 815                                 list_move(&wbk->vnode_link, &graveyard);
 816                 }
 817         }
 818
 819         spin_unlock(&vnode->wb_lock);
 820
 821         while (!list_empty(&graveyard)) {
 822                 wbk = list_entry(graveyard.next, struct afs_wb_key, vnode_link);
 823                 list_del(&wbk->vnode_link);
 824                 afs_put_wb_key(wbk);
 825         }
 826 }
 827
 828 /*
 829  * Clean up a page during invalidation.
 830  */
 831 int afs_launder_page(struct page *page)
 832 {
 833         struct address_space *mapping = page->mapping;
 834         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 835         unsigned long priv;
 836         unsigned int f, t;
 837         int ret = 0;
 838
 839         _enter("{%lx}", page->index);
 840
 841         priv = page_private(page);
 842         if (clear_page_dirty_for_io(page)) {
 843                 f = 0;
 844                 t = PAGE_SIZE;
 845                 if (PagePrivate(page)) {
 846                         f = priv & AFS_PRIV_MAX;
 847                         t = priv >> AFS_PRIV_SHIFT;
 848                 }
 849
 850                 trace_afs_page_dirty(vnode, tracepoint_string("launder"),
 851                                      page->index, priv);
 852                 ret = afs_store_data(mapping, page->index, page->index, t, f);
 853         }
 854
 855         trace_afs_page_dirty(vnode, tracepoint_string("laundered"),
 856                              page->index, priv);
 857         set_page_private(page, 0);
 858         ClearPagePrivate(page);
 859
 860 #ifdef CONFIG_AFS_FSCACHE
 861         if (PageFsCache(page)) {
 862                 fscache_wait_on_page_write(vnode->cache, page);
 863                 fscache_uncache_page(vnode->cache, page);
 864         }
 865 #endif
 866         return ret;
 867 }