fs/afs/write.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* handling of writes to regular files and writing back to the server
   3  *
   4  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/backing-dev.h>
   9 #include <linux/slab.h>
  10 #include <linux/fs.h>
  11 #include <linux/pagemap.h>
  12 #include <linux/writeback.h>
  13 #include <linux/pagevec.h>
  14 #include "internal.h"
  15
  16 /*
  17  * mark a page as having been made dirty and thus needing writeback
  18  */
  19 int afs_set_page_dirty(struct page *page)
  20 {
  21         _enter("");
  22         return __set_page_dirty_nobuffers(page);
  23 }
  24
  25 /*
  26  * partly or wholly fill a page that's under preparation for writing
  27  */
  28 static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
  29                          loff_t pos, unsigned int len, struct page *page)
  30 {
  31         struct afs_read *req;
  32         size_t p;
  33         void *data;
  34         int ret;
  35
  36         _enter(",,%llu", (unsigned long long)pos);
  37
  38         if (pos >= vnode->vfs_inode.i_size) {
  39                 p = pos & ~PAGE_MASK;
  40                 ASSERTCMP(p + len, <=, PAGE_SIZE);
  41                 data = kmap(page);
  42                 memset(data + p, 0, len);
  43                 kunmap(page);
  44                 return 0;
  45         }
  46
  47         req = kzalloc(struct_size(req, array, 1), GFP_KERNEL);
  48         if (!req)
  49                 return -ENOMEM;
  50
  51         refcount_set(&req->usage, 1);
  52         req->pos = pos;
  53         req->len = len;
  54         req->nr_pages = 1;
  55         req->pages = req->array;
  56         req->pages[0] = page;
  57         get_page(page);
  58
  59         ret = afs_fetch_data(vnode, key, req);
  60         afs_put_read(req);
  61         if (ret < 0) {
  62                 if (ret == -ENOENT) {
  63                         _debug("got NOENT from server"
  64                                " - marking file deleted and stale");
  65                         set_bit(AFS_VNODE_DELETED, &vnode->flags);
  66                         ret = -ESTALE;
  67                 }
  68         }
  69
  70         _leave(" = %d", ret);
  71         return ret;
  72 }
  73
  74 /*
  75  * prepare to perform part of a write to a page
  76  */
  77 int afs_write_begin(struct file *file, struct address_space *mapping,
  78                     loff_t pos, unsigned len, unsigned flags,
  79                     struct page **_page, void **fsdata)
  80 {
  81         struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
  82         struct page *page;
  83         struct key *key = afs_file_key(file);
  84         unsigned long priv;
  85         unsigned f, from = pos & (PAGE_SIZE - 1);
  86         unsigned t, to = from + len;
  87         pgoff_t index = pos >> PAGE_SHIFT;
  88         int ret;
  89
  90         _enter("{%llx:%llu},{%lx},%u,%u",
  91                vnode->fid.vid, vnode->fid.vnode, index, from, to);
  92
  93         page = grab_cache_page_write_begin(mapping, index, flags);
  94         if (!page)
  95                 return -ENOMEM;
  96
  97         if (!PageUptodate(page) && len != PAGE_SIZE) {
  98                 ret = afs_fill_page(vnode, key, pos & PAGE_MASK, PAGE_SIZE, page);
  99                 if (ret < 0) {
 100                         unlock_page(page);
 101                         put_page(page);
 102                         _leave(" = %d [prep]", ret);
 103                         return ret;
 104                 }
 105                 SetPageUptodate(page);
 106         }
 107
 108 try_again:
 109         /* See if this page is already partially written in a way that we can
 110          * merge the new write with.
 111          */
 112         t = f = 0;
 113         if (PagePrivate(page)) {
 114                 priv = page_private(page);
 115                 f = afs_page_dirty_from(priv);
 116                 t = afs_page_dirty_to(priv);
 117                 ASSERTCMP(f, <=, t);
 118         }
 119
 120         if (f != t) {
 121                 if (PageWriteback(page)) {
 122                         trace_afs_page_dirty(vnode, tracepoint_string("alrdy"),
 123                                              page->index, priv);
 124                         goto flush_conflicting_write;
 125                 }
 126                 /* If the file is being filled locally, allow inter-write
 127                  * spaces to be merged into writes.  If it's not, only write
 128                  * back what the user gives us.
 129                  */
 130                 if (!test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags) &&
 131                     (to < f || from > t))
 132                         goto flush_conflicting_write;
 133         }
 134
 135         *_page = page;
 136         _leave(" = 0");
 137         return 0;
 138
 139         /* The previous write and this write aren't adjacent or overlapping, so
 140          * flush the page out.
 141          */
 142 flush_conflicting_write:
 143         _debug("flush conflict");
 144         ret = write_one_page(page);
 145         if (ret < 0)
 146                 goto error;
 147
 148         ret = lock_page_killable(page);
 149         if (ret < 0)
 150                 goto error;
 151         goto try_again;
 152
 153 error:
 154         put_page(page);
 155         _leave(" = %d", ret);
 156         return ret;
 157 }
 158
 159 /*
 160  * finalise part of a write to a page
 161  */
 162 int afs_write_end(struct file *file, struct address_space *mapping,
 163                   loff_t pos, unsigned len, unsigned copied,
 164                   struct page *page, void *fsdata)
 165 {
 166         struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
 167         struct key *key = afs_file_key(file);
 168         unsigned long priv;
 169         unsigned int f, from = pos & (PAGE_SIZE - 1);
 170         unsigned int t, to = from + copied;
 171         loff_t i_size, maybe_i_size;
 172         int ret = 0;
 173
 174         _enter("{%llx:%llu},{%lx}",
 175                vnode->fid.vid, vnode->fid.vnode, page->index);
 176
 177         if (copied == 0)
 178                 goto out;
 179
 180         maybe_i_size = pos + copied;
 181
 182         i_size = i_size_read(&vnode->vfs_inode);
 183         if (maybe_i_size > i_size) {
 184                 write_seqlock(&vnode->cb_lock);
 185                 i_size = i_size_read(&vnode->vfs_inode);
 186                 if (maybe_i_size > i_size)
 187                         afs_set_i_size(vnode, maybe_i_size);
 188                 write_sequnlock(&vnode->cb_lock);
 189         }
 190
 191         if (!PageUptodate(page)) {
 192                 if (copied < len) {
 193                         /* Try and load any missing data from the server.  The
 194                          * unmarshalling routine will take care of clearing any
 195                          * bits that are beyond the EOF.
 196                          */
 197                         ret = afs_fill_page(vnode, key, pos + copied,
 198                                             len - copied, page);
 199                         if (ret < 0)
 200                                 goto out;
 201                 }
 202                 SetPageUptodate(page);
 203         }
 204
 205         if (PagePrivate(page)) {
 206                 priv = page_private(page);
 207                 f = afs_page_dirty_from(priv);
 208                 t = afs_page_dirty_to(priv);
 209                 if (from < f)
 210                         f = from;
 211                 if (to > t)
 212                         t = to;
 213                 priv = afs_page_dirty(f, t);
 214                 set_page_private(page, priv);
 215                 trace_afs_page_dirty(vnode, tracepoint_string("dirty+"),
 216                                      page->index, priv);
 217         } else {
 218                 priv = afs_page_dirty(from, to);
 219                 attach_page_private(page, (void *)priv);
 220                 trace_afs_page_dirty(vnode, tracepoint_string("dirty"),
 221                                      page->index, priv);
 222         }
 223
 224         set_page_dirty(page);
 225         if (PageDirty(page))
 226                 _debug("dirtied");
 227         ret = copied;
 228
 229 out:
 230         unlock_page(page);
 231         put_page(page);
 232         return ret;
 233 }
 234
 235 /*
 236  * kill all the pages in the given range
 237  */
 238 static void afs_kill_pages(struct address_space *mapping,
 239                            pgoff_t first, pgoff_t last)
 240 {
 241         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 242         struct pagevec pv;
 243         unsigned count, loop;
 244
 245         _enter("{%llx:%llu},%lx-%lx",
 246                vnode->fid.vid, vnode->fid.vnode, first, last);
 247
 248         pagevec_init(&pv);
 249
 250         do {
 251                 _debug("kill %lx-%lx", first, last);
 252
 253                 count = last - first + 1;
 254                 if (count > PAGEVEC_SIZE)
 255                         count = PAGEVEC_SIZE;
 256                 pv.nr = find_get_pages_contig(mapping, first, count, pv.pages);
 257                 ASSERTCMP(pv.nr, ==, count);
 258
 259                 for (loop = 0; loop < count; loop++) {
 260                         struct page *page = pv.pages[loop];
 261                         ClearPageUptodate(page);
 262                         SetPageError(page);
 263                         end_page_writeback(page);
 264                         if (page->index >= first)
 265                                 first = page->index + 1;
 266                         lock_page(page);
 267                         generic_error_remove_page(mapping, page);
 268                         unlock_page(page);
 269                 }
 270
 271                 __pagevec_release(&pv);
 272         } while (first <= last);
 273
 274         _leave("");
 275 }
 276
 277 /*
 278  * Redirty all the pages in a given range.
 279  */
 280 static void afs_redirty_pages(struct writeback_control *wbc,
 281                               struct address_space *mapping,
 282                               pgoff_t first, pgoff_t last)
 283 {
 284         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 285         struct pagevec pv;
 286         unsigned count, loop;
 287
 288         _enter("{%llx:%llu},%lx-%lx",
 289                vnode->fid.vid, vnode->fid.vnode, first, last);
 290
 291         pagevec_init(&pv);
 292
 293         do {
 294                 _debug("redirty %lx-%lx", first, last);
 295
 296                 count = last - first + 1;
 297                 if (count > PAGEVEC_SIZE)
 298                         count = PAGEVEC_SIZE;
 299                 pv.nr = find_get_pages_contig(mapping, first, count, pv.pages);
 300                 ASSERTCMP(pv.nr, ==, count);
 301
 302                 for (loop = 0; loop < count; loop++) {
 303                         struct page *page = pv.pages[loop];
 304
 305                         redirty_page_for_writepage(wbc, page);
 306                         end_page_writeback(page);
 307                         if (page->index >= first)
 308                                 first = page->index + 1;
 309                 }
 310
 311                 __pagevec_release(&pv);
 312         } while (first <= last);
 313
 314         _leave("");
 315 }
 316
 317 /*
 318  * completion of write to server
 319  */
 320 static void afs_pages_written_back(struct afs_vnode *vnode,
 321                                    pgoff_t first, pgoff_t last)
 322 {
 323         struct pagevec pv;
 324         unsigned long priv;
 325         unsigned count, loop;
 326
 327         _enter("{%llx:%llu},{%lx-%lx}",
 328                vnode->fid.vid, vnode->fid.vnode, first, last);
 329
 330         pagevec_init(&pv);
 331
 332         do {
 333                 _debug("done %lx-%lx", first, last);
 334
 335                 count = last - first + 1;
 336                 if (count > PAGEVEC_SIZE)
 337                         count = PAGEVEC_SIZE;
 338                 pv.nr = find_get_pages_contig(vnode->vfs_inode.i_mapping,
 339                                               first, count, pv.pages);
 340                 ASSERTCMP(pv.nr, ==, count);
 341
 342                 for (loop = 0; loop < count; loop++) {
 343                         priv = (unsigned long)detach_page_private(pv.pages[loop]);
 344                         trace_afs_page_dirty(vnode, tracepoint_string("clear"),
 345                                              pv.pages[loop]->index, priv);
 346                         end_page_writeback(pv.pages[loop]);
 347                 }
 348                 first += count;
 349                 __pagevec_release(&pv);
 350         } while (first <= last);
 351
 352         afs_prune_wb_keys(vnode);
 353         _leave("");
 354 }
 355
 356 /*
 357  * Find a key to use for the writeback.  We cached the keys used to author the
 358  * writes on the vnode.  *_wbk will contain the last writeback key used or NULL
 359  * and we need to start from there if it's set.
 360  */
 361 static int afs_get_writeback_key(struct afs_vnode *vnode,
 362                                  struct afs_wb_key **_wbk)
 363 {
 364         struct afs_wb_key *wbk = NULL;
 365         struct list_head *p;
 366         int ret = -ENOKEY, ret2;
 367
 368         spin_lock(&vnode->wb_lock);
 369         if (*_wbk)
 370                 p = (*_wbk)->vnode_link.next;
 371         else
 372                 p = vnode->wb_keys.next;
 373
 374         while (p != &vnode->wb_keys) {
 375                 wbk = list_entry(p, struct afs_wb_key, vnode_link);
 376                 _debug("wbk %u", key_serial(wbk->key));
 377                 ret2 = key_validate(wbk->key);
 378                 if (ret2 == 0) {
 379                         refcount_inc(&wbk->usage);
 380                         _debug("USE WB KEY %u", key_serial(wbk->key));
 381                         break;
 382                 }
 383
 384                 wbk = NULL;
 385                 if (ret == -ENOKEY)
 386                         ret = ret2;
 387                 p = p->next;
 388         }
 389
 390         spin_unlock(&vnode->wb_lock);
 391         if (*_wbk)
 392                 afs_put_wb_key(*_wbk);
 393         *_wbk = wbk;
 394         return 0;
 395 }
 396
 397 static void afs_store_data_success(struct afs_operation *op)
 398 {
 399         struct afs_vnode *vnode = op->file[0].vnode;
 400
 401         op->ctime = op->file[0].scb.status.mtime_client;
 402         afs_vnode_commit_status(op, &op->file[0]);
 403         if (op->error == 0) {
 404                 if (!op->store.laundering)
 405                         afs_pages_written_back(vnode, op->store.first, op->store.last);
 406                 afs_stat_v(vnode, n_stores);
 407                 atomic_long_add((op->store.last * PAGE_SIZE + op->store.last_to) -
 408                                 (op->store.first * PAGE_SIZE + op->store.first_offset),
 409                                 &afs_v2net(vnode)->n_store_bytes);
 410         }
 411 }
 412
 413 static const struct afs_operation_ops afs_store_data_operation = {
 414         .issue_afs_rpc  = afs_fs_store_data,
 415         .issue_yfs_rpc  = yfs_fs_store_data,
 416         .success        = afs_store_data_success,
 417 };
 418
 419 /*
 420  * write to a file
 421  */
 422 static int afs_store_data(struct address_space *mapping,
 423                           pgoff_t first, pgoff_t last,
 424                           unsigned offset, unsigned to, bool laundering)
 425 {
 426         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 427         struct afs_operation *op;
 428         struct afs_wb_key *wbk = NULL;
 429         int ret;
 430
 431         _enter("%s{%llx:%llu.%u},%lx,%lx,%x,%x",
 432                vnode->volume->name,
 433                vnode->fid.vid,
 434                vnode->fid.vnode,
 435                vnode->fid.unique,
 436                first, last, offset, to);
 437
 438         ret = afs_get_writeback_key(vnode, &wbk);
 439         if (ret) {
 440                 _leave(" = %d [no keys]", ret);
 441                 return ret;
 442         }
 443
 444         op = afs_alloc_operation(wbk->key, vnode->volume);
 445         if (IS_ERR(op)) {
 446                 afs_put_wb_key(wbk);
 447                 return -ENOMEM;
 448         }
 449
 450         afs_op_set_vnode(op, 0, vnode);
 451         op->file[0].dv_delta = 1;
 452         op->store.mapping = mapping;
 453         op->file[0].modification = true;
 454         op->store.first = first;
 455         op->store.last = last;
 456         op->store.first_offset = offset;
 457         op->store.last_to = to;
 458         op->store.laundering = laundering;
 459         op->mtime = vnode->vfs_inode.i_mtime;
 460         op->flags |= AFS_OPERATION_UNINTR;
 461         op->ops = &afs_store_data_operation;
 462
 463 try_next_key:
 464         afs_begin_vnode_operation(op);
 465         afs_wait_for_operation(op);
 466
 467         switch (op->error) {
 468         case -EACCES:
 469         case -EPERM:
 470         case -ENOKEY:
 471         case -EKEYEXPIRED:
 472         case -EKEYREJECTED:
 473         case -EKEYREVOKED:
 474                 _debug("next");
 475
 476                 ret = afs_get_writeback_key(vnode, &wbk);
 477                 if (ret == 0) {
 478                         key_put(op->key);
 479                         op->key = key_get(wbk->key);
 480                         goto try_next_key;
 481                 }
 482                 break;
 483         }
 484
 485         afs_put_wb_key(wbk);
 486         _leave(" = %d", op->error);
 487         return afs_put_operation(op);
 488 }
 489
 490 /*
 491  * Synchronously write back the locked page and any subsequent non-locked dirty
 492  * pages.
 493  */
 494 static int afs_write_back_from_locked_page(struct address_space *mapping,
 495                                            struct writeback_control *wbc,
 496                                            struct page *primary_page,
 497                                            pgoff_t final_page)
 498 {
 499         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 500         struct page *pages[8], *page;
 501         unsigned long count, priv;
 502         unsigned n, offset, to, f, t;
 503         pgoff_t start, first, last;
 504         loff_t i_size, end;
 505         int loop, ret;
 506
 507         _enter(",%lx", primary_page->index);
 508
 509         count = 1;
 510         if (test_set_page_writeback(primary_page))
 511                 BUG();
 512
 513         /* Find all consecutive lockable dirty pages that have contiguous
 514          * written regions, stopping when we find a page that is not
 515          * immediately lockable, is not dirty or is missing, or we reach the
 516          * end of the range.
 517          */
 518         start = primary_page->index;
 519         priv = page_private(primary_page);
 520         offset = afs_page_dirty_from(priv);
 521         to = afs_page_dirty_to(priv);
 522         trace_afs_page_dirty(vnode, tracepoint_string("store"),
 523                              primary_page->index, priv);
 524
 525         WARN_ON(offset == to);
 526         if (offset == to)
 527                 trace_afs_page_dirty(vnode, tracepoint_string("WARN"),
 528                                      primary_page->index, priv);
 529
 530         if (start >= final_page ||
 531             (to < PAGE_SIZE && !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)))
 532                 goto no_more;
 533
 534         start++;
 535         do {
 536                 _debug("more %lx [%lx]", start, count);
 537                 n = final_page - start + 1;
 538                 if (n > ARRAY_SIZE(pages))
 539                         n = ARRAY_SIZE(pages);
 540                 n = find_get_pages_contig(mapping, start, ARRAY_SIZE(pages), pages);
 541                 _debug("fgpc %u", n);
 542                 if (n == 0)
 543                         goto no_more;
 544                 if (pages[0]->index != start) {
 545                         do {
 546                                 put_page(pages[--n]);
 547                         } while (n > 0);
 548                         goto no_more;
 549                 }
 550
 551                 for (loop = 0; loop < n; loop++) {
 552                         page = pages[loop];
 553                         if (to != PAGE_SIZE &&
 554                             !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags))
 555                                 break;
 556                         if (page->index > final_page)
 557                                 break;
 558                         if (!trylock_page(page))
 559                                 break;
 560                         if (!PageDirty(page) || PageWriteback(page)) {
 561                                 unlock_page(page);
 562                                 break;
 563                         }
 564
 565                         priv = page_private(page);
 566                         f = afs_page_dirty_from(priv);
 567                         t = afs_page_dirty_to(priv);
 568                         if (f != 0 &&
 569                             !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)) {
 570                                 unlock_page(page);
 571                                 break;
 572                         }
 573                         to = t;
 574
 575                         trace_afs_page_dirty(vnode, tracepoint_string("store+"),
 576                                              page->index, priv);
 577
 578                         if (!clear_page_dirty_for_io(page))
 579                                 BUG();
 580                         if (test_set_page_writeback(page))
 581                                 BUG();
 582                         unlock_page(page);
 583                         put_page(page);
 584                 }
 585                 count += loop;
 586                 if (loop < n) {
 587                         for (; loop < n; loop++)
 588                                 put_page(pages[loop]);
 589                         goto no_more;
 590                 }
 591
 592                 start += loop;
 593         } while (start <= final_page && count < 65536);
 594
 595 no_more:
 596         /* We now have a contiguous set of dirty pages, each with writeback
 597          * set; the first page is still locked at this point, but all the rest
 598          * have been unlocked.
 599          */
 600         unlock_page(primary_page);
 601
 602         first = primary_page->index;
 603         last = first + count - 1;
 604
 605         end = (loff_t)last * PAGE_SIZE + to;
 606         i_size = i_size_read(&vnode->vfs_inode);
 607
 608         _debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to);
 609         if (end > i_size)
 610                 to = i_size & ~PAGE_MASK;
 611
 612         ret = afs_store_data(mapping, first, last, offset, to, false);
 613         switch (ret) {
 614         case 0:
 615                 ret = count;
 616                 break;
 617
 618         default:
 619                 pr_notice("kAFS: Unexpected error from FS.StoreData %d\n", ret);
 620                 fallthrough;
 621         case -EACCES:
 622         case -EPERM:
 623         case -ENOKEY:
 624         case -EKEYEXPIRED:
 625         case -EKEYREJECTED:
 626         case -EKEYREVOKED:
 627                 afs_redirty_pages(wbc, mapping, first, last);
 628                 mapping_set_error(mapping, ret);
 629                 break;
 630
 631         case -EDQUOT:
 632         case -ENOSPC:
 633                 afs_redirty_pages(wbc, mapping, first, last);
 634                 mapping_set_error(mapping, -ENOSPC);
 635                 break;
 636
 637         case -EROFS:
 638         case -EIO:
 639         case -EREMOTEIO:
 640         case -EFBIG:
 641         case -ENOENT:
 642         case -ENOMEDIUM:
 643         case -ENXIO:
 644                 trace_afs_file_error(vnode, ret, afs_file_error_writeback_fail);
 645                 afs_kill_pages(mapping, first, last);
 646                 mapping_set_error(mapping, ret);
 647                 break;
 648         }
 649
 650         _leave(" = %d", ret);
 651         return ret;
 652 }
 653
 654 /*
 655  * write a page back to the server
 656  * - the caller locked the page for us
 657  */
 658 int afs_writepage(struct page *page, struct writeback_control *wbc)
 659 {
 660         int ret;
 661
 662         _enter("{%lx},", page->index);
 663
 664         ret = afs_write_back_from_locked_page(page->mapping, wbc, page,
 665                                               wbc->range_end >> PAGE_SHIFT);
 666         if (ret < 0) {
 667                 _leave(" = %d", ret);
 668                 return 0;
 669         }
 670
 671         wbc->nr_to_write -= ret;
 672
 673         _leave(" = 0");
 674         return 0;
 675 }
 676
 677 /*
 678  * write a region of pages back to the server
 679  */
 680 static int afs_writepages_region(struct address_space *mapping,
 681                                  struct writeback_control *wbc,
 682                                  pgoff_t index, pgoff_t end, pgoff_t *_next)
 683 {
 684         struct page *page;
 685         int ret, n;
 686
 687         _enter(",,%lx,%lx,", index, end);
 688
 689         do {
 690                 n = find_get_pages_range_tag(mapping, &index, end,
 691                                         PAGECACHE_TAG_DIRTY, 1, &page);
 692                 if (!n)
 693                         break;
 694
 695                 _debug("wback %lx", page->index);
 696
 697                 /*
 698                  * at this point we hold neither the i_pages lock nor the
 699                  * page lock: the page may be truncated or invalidated
 700                  * (changing page->mapping to NULL), or even swizzled
 701                  * back from swapper_space to tmpfs file mapping
 702                  */
 703                 ret = lock_page_killable(page);
 704                 if (ret < 0) {
 705                         put_page(page);
 706                         _leave(" = %d", ret);
 707                         return ret;
 708                 }
 709
 710                 if (page->mapping != mapping || !PageDirty(page)) {
 711                         unlock_page(page);
 712                         put_page(page);
 713                         continue;
 714                 }
 715
 716                 if (PageWriteback(page)) {
 717                         unlock_page(page);
 718                         if (wbc->sync_mode != WB_SYNC_NONE)
 719                                 wait_on_page_writeback(page);
 720                         put_page(page);
 721                         continue;
 722                 }
 723
 724                 if (!clear_page_dirty_for_io(page))
 725                         BUG();
 726                 ret = afs_write_back_from_locked_page(mapping, wbc, page, end);
 727                 put_page(page);
 728                 if (ret < 0) {
 729                         _leave(" = %d", ret);
 730                         return ret;
 731                 }
 732
 733                 wbc->nr_to_write -= ret;
 734
 735                 cond_resched();
 736         } while (index < end && wbc->nr_to_write > 0);
 737
 738         *_next = index;
 739         _leave(" = 0 [%lx]", *_next);
 740         return 0;
 741 }
 742
 743 /*
 744  * write some of the pending data back to the server
 745  */
 746 int afs_writepages(struct address_space *mapping,
 747                    struct writeback_control *wbc)
 748 {
 749         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 750         pgoff_t start, end, next;
 751         int ret;
 752
 753         _enter("");
 754
 755         /* We have to be careful as we can end up racing with setattr()
 756          * truncating the pagecache since the caller doesn't take a lock here
 757          * to prevent it.
 758          */
 759         if (wbc->sync_mode == WB_SYNC_ALL)
 760                 down_read(&vnode->validate_lock);
 761         else if (!down_read_trylock(&vnode->validate_lock))
 762                 return 0;
 763
 764         if (wbc->range_cyclic) {
 765                 start = mapping->writeback_index;
 766                 end = -1;
 767                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
 768                 if (start > 0 && wbc->nr_to_write > 0 && ret == 0)
 769                         ret = afs_writepages_region(mapping, wbc, 0, start,
 770                                                     &next);
 771                 mapping->writeback_index = next;
 772         } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
 773                 end = (pgoff_t)(LLONG_MAX >> PAGE_SHIFT);
 774                 ret = afs_writepages_region(mapping, wbc, 0, end, &next);
 775                 if (wbc->nr_to_write > 0)
 776                         mapping->writeback_index = next;
 777         } else {
 778                 start = wbc->range_start >> PAGE_SHIFT;
 779                 end = wbc->range_end >> PAGE_SHIFT;
 780                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
 781         }
 782
 783         up_read(&vnode->validate_lock);
 784         _leave(" = %d", ret);
 785         return ret;
 786 }
 787
 788 /*
 789  * write to an AFS file
 790  */
 791 ssize_t afs_file_write(struct kiocb *iocb, struct iov_iter *from)
 792 {
 793         struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp));
 794         ssize_t result;
 795         size_t count = iov_iter_count(from);
 796
 797         _enter("{%llx:%llu},{%zu},",
 798                vnode->fid.vid, vnode->fid.vnode, count);
 799
 800         if (IS_SWAPFILE(&vnode->vfs_inode)) {
 801                 printk(KERN_INFO
 802                        "AFS: Attempt to write to active swap file!\n");
 803                 return -EBUSY;
 804         }
 805
 806         if (!count)
 807                 return 0;
 808
 809         result = generic_file_write_iter(iocb, from);
 810
 811         _leave(" = %zd", result);
 812         return result;
 813 }
 814
 815 /*
 816  * flush any dirty pages for this process, and check for write errors.
 817  * - the return status from this call provides a reliable indication of
 818  *   whether any write errors occurred for this process.
 819  */
 820 int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 821 {
 822         struct inode *inode = file_inode(file);
 823         struct afs_vnode *vnode = AFS_FS_I(inode);
 824
 825         _enter("{%llx:%llu},{n=%pD},%d",
 826                vnode->fid.vid, vnode->fid.vnode, file,
 827                datasync);
 828
 829         return file_write_and_wait_range(file, start, end);
 830 }
 831
 832 /*
 833  * notification that a previously read-only page is about to become writable
 834  * - if it returns an error, the caller will deliver a bus error signal
 835  */
 836 vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
 837 {
 838         struct file *file = vmf->vma->vm_file;
 839         struct inode *inode = file_inode(file);
 840         struct afs_vnode *vnode = AFS_FS_I(inode);
 841         unsigned long priv;
 842
 843         _enter("{{%llx:%llu}},{%lx}",
 844                vnode->fid.vid, vnode->fid.vnode, vmf->page->index);
 845
 846         sb_start_pagefault(inode->i_sb);
 847
 848         /* Wait for the page to be written to the cache before we allow it to
 849          * be modified.  We then assume the entire page will need writing back.
 850          */
 851 #ifdef CONFIG_AFS_FSCACHE
 852         fscache_wait_on_page_write(vnode->cache, vmf->page);
 853 #endif
 854
 855         if (PageWriteback(vmf->page) &&
 856             wait_on_page_bit_killable(vmf->page, PG_writeback) < 0)
 857                 return VM_FAULT_RETRY;
 858
 859         if (lock_page_killable(vmf->page) < 0)
 860                 return VM_FAULT_RETRY;
 861
 862         /* We mustn't change page->private until writeback is complete as that
 863          * details the portion of the page we need to write back and we might
 864          * need to redirty the page if there's a problem.
 865          */
 866         wait_on_page_writeback(vmf->page);
 867
 868         priv = afs_page_dirty(0, PAGE_SIZE);
 869         priv = afs_page_dirty_mmapped(priv);
 870         trace_afs_page_dirty(vnode, tracepoint_string("mkwrite"),
 871                              vmf->page->index, priv);
 872         if (PagePrivate(vmf->page))
 873                 set_page_private(vmf->page, priv);
 874         else
 875                 attach_page_private(vmf->page, (void *)priv);
 876         file_update_time(file);
 877
 878         sb_end_pagefault(inode->i_sb);
 879         return VM_FAULT_LOCKED;
 880 }
 881
 882 /*
 883  * Prune the keys cached for writeback.  The caller must hold vnode->wb_lock.
 884  */
 885 void afs_prune_wb_keys(struct afs_vnode *vnode)
 886 {
 887         LIST_HEAD(graveyard);
 888         struct afs_wb_key *wbk, *tmp;
 889
 890         /* Discard unused keys */
 891         spin_lock(&vnode->wb_lock);
 892
 893         if (!mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_WRITEBACK) &&
 894             !mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_DIRTY)) {
 895                 list_for_each_entry_safe(wbk, tmp, &vnode->wb_keys, vnode_link) {
 896                         if (refcount_read(&wbk->usage) == 1)
 897                                 list_move(&wbk->vnode_link, &graveyard);
 898                 }
 899         }
 900
 901         spin_unlock(&vnode->wb_lock);
 902
 903         while (!list_empty(&graveyard)) {
 904                 wbk = list_entry(graveyard.next, struct afs_wb_key, vnode_link);
 905                 list_del(&wbk->vnode_link);
 906                 afs_put_wb_key(wbk);
 907         }
 908 }
 909
 910 /*
 911  * Clean up a page during invalidation.
 912  */
 913 int afs_launder_page(struct page *page)
 914 {
 915         struct address_space *mapping = page->mapping;
 916         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 917         unsigned long priv;
 918         unsigned int f, t;
 919         int ret = 0;
 920
 921         _enter("{%lx}", page->index);
 922
 923         priv = page_private(page);
 924         if (clear_page_dirty_for_io(page)) {
 925                 f = 0;
 926                 t = PAGE_SIZE;
 927                 if (PagePrivate(page)) {
 928                         f = afs_page_dirty_from(priv);
 929                         t = afs_page_dirty_to(priv);
 930                 }
 931
 932                 trace_afs_page_dirty(vnode, tracepoint_string("launder"),
 933                                      page->index, priv);
 934                 ret = afs_store_data(mapping, page->index, page->index, t, f, true);
 935         }
 936
 937         priv = (unsigned long)detach_page_private(page);
 938         trace_afs_page_dirty(vnode, tracepoint_string("laundered"),
 939                              page->index, priv);
 940
 941 #ifdef CONFIG_AFS_FSCACHE
 942         if (PageFsCache(page)) {
 943                 fscache_wait_on_page_write(vnode->cache, page);
 944                 fscache_uncache_page(vnode->cache, page);
 945         }
 946 #endif
 947         return ret;
 948 }