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         /* We want to store information about how much of a page is altered in
  94          * page->private.
  95          */
  96         BUILD_BUG_ON(PAGE_SIZE - 1 > __AFS_PAGE_PRIV_MASK && sizeof(page->private) < 8);
  97
  98         page = grab_cache_page_write_begin(mapping, index, flags);
  99         if (!page)
 100                 return -ENOMEM;
 101
 102         if (!PageUptodate(page) && len != PAGE_SIZE) {
 103                 ret = afs_fill_page(vnode, key, pos & PAGE_MASK, PAGE_SIZE, page);
 104                 if (ret < 0) {
 105                         unlock_page(page);
 106                         put_page(page);
 107                         _leave(" = %d [prep]", ret);
 108                         return ret;
 109                 }
 110                 SetPageUptodate(page);
 111         }
 112
 113 try_again:
 114         /* See if this page is already partially written in a way that we can
 115          * merge the new write with.
 116          */
 117         t = f = 0;
 118         if (PagePrivate(page)) {
 119                 priv = page_private(page);
 120                 f = afs_page_dirty_from(priv);
 121                 t = afs_page_dirty_to(priv);
 122                 ASSERTCMP(f, <=, t);
 123         }
 124
 125         if (f != t) {
 126                 if (PageWriteback(page)) {
 127                         trace_afs_page_dirty(vnode, tracepoint_string("alrdy"),
 128                                              page->index, priv);
 129                         goto flush_conflicting_write;
 130                 }
 131                 /* If the file is being filled locally, allow inter-write
 132                  * spaces to be merged into writes.  If it's not, only write
 133                  * back what the user gives us.
 134                  */
 135                 if (!test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags) &&
 136                     (to < f || from > t))
 137                         goto flush_conflicting_write;
 138         }
 139
 140         *_page = page;
 141         _leave(" = 0");
 142         return 0;
 143
 144         /* The previous write and this write aren't adjacent or overlapping, so
 145          * flush the page out.
 146          */
 147 flush_conflicting_write:
 148         _debug("flush conflict");
 149         ret = write_one_page(page);
 150         if (ret < 0)
 151                 goto error;
 152
 153         ret = lock_page_killable(page);
 154         if (ret < 0)
 155                 goto error;
 156         goto try_again;
 157
 158 error:
 159         put_page(page);
 160         _leave(" = %d", ret);
 161         return ret;
 162 }
 163
 164 /*
 165  * finalise part of a write to a page
 166  */
 167 int afs_write_end(struct file *file, struct address_space *mapping,
 168                   loff_t pos, unsigned len, unsigned copied,
 169                   struct page *page, void *fsdata)
 170 {
 171         struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
 172         struct key *key = afs_file_key(file);
 173         unsigned long priv;
 174         unsigned int f, from = pos & (PAGE_SIZE - 1);
 175         unsigned int t, to = from + copied;
 176         loff_t i_size, maybe_i_size;
 177         int ret;
 178
 179         _enter("{%llx:%llu},{%lx}",
 180                vnode->fid.vid, vnode->fid.vnode, page->index);
 181
 182         maybe_i_size = pos + copied;
 183
 184         i_size = i_size_read(&vnode->vfs_inode);
 185         if (maybe_i_size > i_size) {
 186                 write_seqlock(&vnode->cb_lock);
 187                 i_size = i_size_read(&vnode->vfs_inode);
 188                 if (maybe_i_size > i_size)
 189                         i_size_write(&vnode->vfs_inode, maybe_i_size);
 190                 write_sequnlock(&vnode->cb_lock);
 191         }
 192
 193         if (!PageUptodate(page)) {
 194                 if (copied < len) {
 195                         /* Try and load any missing data from the server.  The
 196                          * unmarshalling routine will take care of clearing any
 197                          * bits that are beyond the EOF.
 198                          */
 199                         ret = afs_fill_page(vnode, key, pos + copied,
 200                                             len - copied, page);
 201                         if (ret < 0)
 202                                 goto out;
 203                 }
 204                 SetPageUptodate(page);
 205         }
 206
 207         if (PagePrivate(page)) {
 208                 priv = page_private(page);
 209                 f = afs_page_dirty_from(priv);
 210                 t = afs_page_dirty_to(priv);
 211                 if (from < f)
 212                         f = from;
 213                 if (to > t)
 214                         t = to;
 215                 priv = afs_page_dirty(f, t);
 216                 set_page_private(page, priv);
 217                 trace_afs_page_dirty(vnode, tracepoint_string("dirty+"),
 218                                      page->index, priv);
 219         } else {
 220                 priv = afs_page_dirty(from, to);
 221                 attach_page_private(page, (void *)priv);
 222                 trace_afs_page_dirty(vnode, tracepoint_string("dirty"),
 223                                      page->index, priv);
 224         }
 225
 226         set_page_dirty(page);
 227         if (PageDirty(page))
 228                 _debug("dirtied");
 229         ret = copied;
 230
 231 out:
 232         unlock_page(page);
 233         put_page(page);
 234         return ret;
 235 }
 236
 237 /*
 238  * kill all the pages in the given range
 239  */
 240 static void afs_kill_pages(struct address_space *mapping,
 241                            pgoff_t first, pgoff_t last)
 242 {
 243         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 244         struct pagevec pv;
 245         unsigned count, loop;
 246
 247         _enter("{%llx:%llu},%lx-%lx",
 248                vnode->fid.vid, vnode->fid.vnode, first, last);
 249
 250         pagevec_init(&pv);
 251
 252         do {
 253                 _debug("kill %lx-%lx", first, last);
 254
 255                 count = last - first + 1;
 256                 if (count > PAGEVEC_SIZE)
 257                         count = PAGEVEC_SIZE;
 258                 pv.nr = find_get_pages_contig(mapping, first, count, pv.pages);
 259                 ASSERTCMP(pv.nr, ==, count);
 260
 261                 for (loop = 0; loop < count; loop++) {
 262                         struct page *page = pv.pages[loop];
 263                         ClearPageUptodate(page);
 264                         SetPageError(page);
 265                         end_page_writeback(page);
 266                         if (page->index >= first)
 267                                 first = page->index + 1;
 268                         lock_page(page);
 269                         generic_error_remove_page(mapping, page);
 270                         unlock_page(page);
 271                 }
 272
 273                 __pagevec_release(&pv);
 274         } while (first <= last);
 275
 276         _leave("");
 277 }
 278
 279 /*
 280  * Redirty all the pages in a given range.
 281  */
 282 static void afs_redirty_pages(struct writeback_control *wbc,
 283                               struct address_space *mapping,
 284                               pgoff_t first, pgoff_t last)
 285 {
 286         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 287         struct pagevec pv;
 288         unsigned count, loop;
 289
 290         _enter("{%llx:%llu},%lx-%lx",
 291                vnode->fid.vid, vnode->fid.vnode, first, last);
 292
 293         pagevec_init(&pv);
 294
 295         do {
 296                 _debug("redirty %lx-%lx", first, last);
 297
 298                 count = last - first + 1;
 299                 if (count > PAGEVEC_SIZE)
 300                         count = PAGEVEC_SIZE;
 301                 pv.nr = find_get_pages_contig(mapping, first, count, pv.pages);
 302                 ASSERTCMP(pv.nr, ==, count);
 303
 304                 for (loop = 0; loop < count; loop++) {
 305                         struct page *page = pv.pages[loop];
 306
 307                         redirty_page_for_writepage(wbc, page);
 308                         end_page_writeback(page);
 309                         if (page->index >= first)
 310                                 first = page->index + 1;
 311                 }
 312
 313                 __pagevec_release(&pv);
 314         } while (first <= last);
 315
 316         _leave("");
 317 }
 318
 319 /*
 320  * completion of write to server
 321  */
 322 static void afs_pages_written_back(struct afs_vnode *vnode,
 323                                    pgoff_t first, pgoff_t last)
 324 {
 325         struct pagevec pv;
 326         unsigned long priv;
 327         unsigned count, loop;
 328
 329         _enter("{%llx:%llu},{%lx-%lx}",
 330                vnode->fid.vid, vnode->fid.vnode, first, last);
 331
 332         pagevec_init(&pv);
 333
 334         do {
 335                 _debug("done %lx-%lx", first, last);
 336
 337                 count = last - first + 1;
 338                 if (count > PAGEVEC_SIZE)
 339                         count = PAGEVEC_SIZE;
 340                 pv.nr = find_get_pages_contig(vnode->vfs_inode.i_mapping,
 341                                               first, count, pv.pages);
 342                 ASSERTCMP(pv.nr, ==, count);
 343
 344                 for (loop = 0; loop < count; loop++) {
 345                         priv = (unsigned long)detach_page_private(pv.pages[loop]);
 346                         trace_afs_page_dirty(vnode, tracepoint_string("clear"),
 347                                              pv.pages[loop]->index, priv);
 348                         end_page_writeback(pv.pages[loop]);
 349                 }
 350                 first += count;
 351                 __pagevec_release(&pv);
 352         } while (first <= last);
 353
 354         afs_prune_wb_keys(vnode);
 355         _leave("");
 356 }
 357
 358 /*
 359  * Find a key to use for the writeback.  We cached the keys used to author the
 360  * writes on the vnode.  *_wbk will contain the last writeback key used or NULL
 361  * and we need to start from there if it's set.
 362  */
 363 static int afs_get_writeback_key(struct afs_vnode *vnode,
 364                                  struct afs_wb_key **_wbk)
 365 {
 366         struct afs_wb_key *wbk = NULL;
 367         struct list_head *p;
 368         int ret = -ENOKEY, ret2;
 369
 370         spin_lock(&vnode->wb_lock);
 371         if (*_wbk)
 372                 p = (*_wbk)->vnode_link.next;
 373         else
 374                 p = vnode->wb_keys.next;
 375
 376         while (p != &vnode->wb_keys) {
 377                 wbk = list_entry(p, struct afs_wb_key, vnode_link);
 378                 _debug("wbk %u", key_serial(wbk->key));
 379                 ret2 = key_validate(wbk->key);
 380                 if (ret2 == 0) {
 381                         refcount_inc(&wbk->usage);
 382                         _debug("USE WB KEY %u", key_serial(wbk->key));
 383                         break;
 384                 }
 385
 386                 wbk = NULL;
 387                 if (ret == -ENOKEY)
 388                         ret = ret2;
 389                 p = p->next;
 390         }
 391
 392         spin_unlock(&vnode->wb_lock);
 393         if (*_wbk)
 394                 afs_put_wb_key(*_wbk);
 395         *_wbk = wbk;
 396         return 0;
 397 }
 398
 399 static void afs_store_data_success(struct afs_operation *op)
 400 {
 401         struct afs_vnode *vnode = op->file[0].vnode;
 402
 403         op->ctime = op->file[0].scb.status.mtime_client;
 404         afs_vnode_commit_status(op, &op->file[0]);
 405         if (op->error == 0) {
 406                 if (!op->store.laundering)
 407                         afs_pages_written_back(vnode, op->store.first, op->store.last);
 408                 afs_stat_v(vnode, n_stores);
 409                 atomic_long_add((op->store.last * PAGE_SIZE + op->store.last_to) -
 410                                 (op->store.first * PAGE_SIZE + op->store.first_offset),
 411                                 &afs_v2net(vnode)->n_store_bytes);
 412         }
 413 }
 414
 415 static const struct afs_operation_ops afs_store_data_operation = {
 416         .issue_afs_rpc  = afs_fs_store_data,
 417         .issue_yfs_rpc  = yfs_fs_store_data,
 418         .success        = afs_store_data_success,
 419 };
 420
 421 /*
 422  * write to a file
 423  */
 424 static int afs_store_data(struct address_space *mapping,
 425                           pgoff_t first, pgoff_t last,
 426                           unsigned offset, unsigned to, bool laundering)
 427 {
 428         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 429         struct afs_operation *op;
 430         struct afs_wb_key *wbk = NULL;
 431         int ret;
 432
 433         _enter("%s{%llx:%llu.%u},%lx,%lx,%x,%x",
 434                vnode->volume->name,
 435                vnode->fid.vid,
 436                vnode->fid.vnode,
 437                vnode->fid.unique,
 438                first, last, offset, to);
 439
 440         ret = afs_get_writeback_key(vnode, &wbk);
 441         if (ret) {
 442                 _leave(" = %d [no keys]", ret);
 443                 return ret;
 444         }
 445
 446         op = afs_alloc_operation(wbk->key, vnode->volume);
 447         if (IS_ERR(op)) {
 448                 afs_put_wb_key(wbk);
 449                 return -ENOMEM;
 450         }
 451
 452         afs_op_set_vnode(op, 0, vnode);
 453         op->file[0].dv_delta = 1;
 454         op->store.mapping = mapping;
 455         op->store.first = first;
 456         op->store.last = last;
 457         op->store.first_offset = offset;
 458         op->store.last_to = to;
 459         op->store.laundering = laundering;
 460         op->mtime = vnode->vfs_inode.i_mtime;
 461         op->flags |= AFS_OPERATION_UNINTR;
 462         op->ops = &afs_store_data_operation;
 463
 464 try_next_key:
 465         afs_begin_vnode_operation(op);
 466         afs_wait_for_operation(op);
 467
 468         switch (op->error) {
 469         case -EACCES:
 470         case -EPERM:
 471         case -ENOKEY:
 472         case -EKEYEXPIRED:
 473         case -EKEYREJECTED:
 474         case -EKEYREVOKED:
 475                 _debug("next");
 476
 477                 ret = afs_get_writeback_key(vnode, &wbk);
 478                 if (ret == 0) {
 479                         key_put(op->key);
 480                         op->key = key_get(wbk->key);
 481                         goto try_next_key;
 482                 }
 483                 break;
 484         }
 485
 486         afs_put_wb_key(wbk);
 487         _leave(" = %d", op->error);
 488         return afs_put_operation(op);
 489 }
 490
 491 /*
 492  * Synchronously write back the locked page and any subsequent non-locked dirty
 493  * pages.
 494  */
 495 static int afs_write_back_from_locked_page(struct address_space *mapping,
 496                                            struct writeback_control *wbc,
 497                                            struct page *primary_page,
 498                                            pgoff_t final_page)
 499 {
 500         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 501         struct page *pages[8], *page;
 502         unsigned long count, priv;
 503         unsigned n, offset, to, f, t;
 504         pgoff_t start, first, last;
 505         loff_t i_size, end;
 506         int loop, ret;
 507
 508         _enter(",%lx", primary_page->index);
 509
 510         count = 1;
 511         if (test_set_page_writeback(primary_page))
 512                 BUG();
 513
 514         /* Find all consecutive lockable dirty pages that have contiguous
 515          * written regions, stopping when we find a page that is not
 516          * immediately lockable, is not dirty or is missing, or we reach the
 517          * end of the range.
 518          */
 519         start = primary_page->index;
 520         priv = page_private(primary_page);
 521         offset = afs_page_dirty_from(priv);
 522         to = afs_page_dirty_to(priv);
 523         trace_afs_page_dirty(vnode, tracepoint_string("store"),
 524                              primary_page->index, priv);
 525
 526         WARN_ON(offset == to);
 527         if (offset == to)
 528                 trace_afs_page_dirty(vnode, tracepoint_string("WARN"),
 529                                      primary_page->index, priv);
 530
 531         if (start >= final_page ||
 532             (to < PAGE_SIZE && !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)))
 533                 goto no_more;
 534
 535         start++;
 536         do {
 537                 _debug("more %lx [%lx]", start, count);
 538                 n = final_page - start + 1;
 539                 if (n > ARRAY_SIZE(pages))
 540                         n = ARRAY_SIZE(pages);
 541                 n = find_get_pages_contig(mapping, start, ARRAY_SIZE(pages), pages);
 542                 _debug("fgpc %u", n);
 543                 if (n == 0)
 544                         goto no_more;
 545                 if (pages[0]->index != start) {
 546                         do {
 547                                 put_page(pages[--n]);
 548                         } while (n > 0);
 549                         goto no_more;
 550                 }
 551
 552                 for (loop = 0; loop < n; loop++) {
 553                         page = pages[loop];
 554                         if (to != PAGE_SIZE &&
 555                             !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags))
 556                                 break;
 557                         if (page->index > final_page)
 558                                 break;
 559                         if (!trylock_page(page))
 560                                 break;
 561                         if (!PageDirty(page) || PageWriteback(page)) {
 562                                 unlock_page(page);
 563                                 break;
 564                         }
 565
 566                         priv = page_private(page);
 567                         f = afs_page_dirty_from(priv);
 568                         t = afs_page_dirty_to(priv);
 569                         if (f != 0 &&
 570                             !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)) {
 571                                 unlock_page(page);
 572                                 break;
 573                         }
 574                         to = t;
 575
 576                         trace_afs_page_dirty(vnode, tracepoint_string("store+"),
 577                                              page->index, priv);
 578
 579                         if (!clear_page_dirty_for_io(page))
 580                                 BUG();
 581                         if (test_set_page_writeback(page))
 582                                 BUG();
 583                         unlock_page(page);
 584                         put_page(page);
 585                 }
 586                 count += loop;
 587                 if (loop < n) {
 588                         for (; loop < n; loop++)
 589                                 put_page(pages[loop]);
 590                         goto no_more;
 591                 }
 592
 593                 start += loop;
 594         } while (start <= final_page && count < 65536);
 595
 596 no_more:
 597         /* We now have a contiguous set of dirty pages, each with writeback
 598          * set; the first page is still locked at this point, but all the rest
 599          * have been unlocked.
 600          */
 601         unlock_page(primary_page);
 602
 603         first = primary_page->index;
 604         last = first + count - 1;
 605
 606         end = (loff_t)last * PAGE_SIZE + to;
 607         i_size = i_size_read(&vnode->vfs_inode);
 608
 609         _debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to);
 610         if (end > i_size)
 611                 to = i_size & ~PAGE_MASK;
 612
 613         ret = afs_store_data(mapping, first, last, offset, to, false);
 614         switch (ret) {
 615         case 0:
 616                 ret = count;
 617                 break;
 618
 619         default:
 620                 pr_notice("kAFS: Unexpected error from FS.StoreData %d\n", ret);
 621                 fallthrough;
 622         case -EACCES:
 623         case -EPERM:
 624         case -ENOKEY:
 625         case -EKEYEXPIRED:
 626         case -EKEYREJECTED:
 627         case -EKEYREVOKED:
 628                 afs_redirty_pages(wbc, mapping, first, last);
 629                 mapping_set_error(mapping, ret);
 630                 break;
 631
 632         case -EDQUOT:
 633         case -ENOSPC:
 634                 afs_redirty_pages(wbc, mapping, first, last);
 635                 mapping_set_error(mapping, -ENOSPC);
 636                 break;
 637
 638         case -EROFS:
 639         case -EIO:
 640         case -EREMOTEIO:
 641         case -EFBIG:
 642         case -ENOENT:
 643         case -ENOMEDIUM:
 644         case -ENXIO:
 645                 trace_afs_file_error(vnode, ret, afs_file_error_writeback_fail);
 646                 afs_kill_pages(mapping, first, last);
 647                 mapping_set_error(mapping, ret);
 648                 break;
 649         }
 650
 651         _leave(" = %d", ret);
 652         return ret;
 653 }
 654
 655 /*
 656  * write a page back to the server
 657  * - the caller locked the page for us
 658  */
 659 int afs_writepage(struct page *page, struct writeback_control *wbc)
 660 {
 661         int ret;
 662
 663         _enter("{%lx},", page->index);
 664
 665         ret = afs_write_back_from_locked_page(page->mapping, wbc, page,
 666                                               wbc->range_end >> PAGE_SHIFT);
 667         if (ret < 0) {
 668                 _leave(" = %d", ret);
 669                 return 0;
 670         }
 671
 672         wbc->nr_to_write -= ret;
 673
 674         _leave(" = 0");
 675         return 0;
 676 }
 677
 678 /*
 679  * write a region of pages back to the server
 680  */
 681 static int afs_writepages_region(struct address_space *mapping,
 682                                  struct writeback_control *wbc,
 683                                  pgoff_t index, pgoff_t end, pgoff_t *_next)
 684 {
 685         struct page *page;
 686         int ret, n;
 687
 688         _enter(",,%lx,%lx,", index, end);
 689
 690         do {
 691                 n = find_get_pages_range_tag(mapping, &index, end,
 692                                         PAGECACHE_TAG_DIRTY, 1, &page);
 693                 if (!n)
 694                         break;
 695
 696                 _debug("wback %lx", page->index);
 697
 698                 /*
 699                  * at this point we hold neither the i_pages lock nor the
 700                  * page lock: the page may be truncated or invalidated
 701                  * (changing page->mapping to NULL), or even swizzled
 702                  * back from swapper_space to tmpfs file mapping
 703                  */
 704                 ret = lock_page_killable(page);
 705                 if (ret < 0) {
 706                         put_page(page);
 707                         _leave(" = %d", ret);
 708                         return ret;
 709                 }
 710
 711                 if (page->mapping != mapping || !PageDirty(page)) {
 712                         unlock_page(page);
 713                         put_page(page);
 714                         continue;
 715                 }
 716
 717                 if (PageWriteback(page)) {
 718                         unlock_page(page);
 719                         if (wbc->sync_mode != WB_SYNC_NONE)
 720                                 wait_on_page_writeback(page);
 721                         put_page(page);
 722                         continue;
 723                 }
 724
 725                 if (!clear_page_dirty_for_io(page))
 726                         BUG();
 727                 ret = afs_write_back_from_locked_page(mapping, wbc, page, end);
 728                 put_page(page);
 729                 if (ret < 0) {
 730                         _leave(" = %d", ret);
 731                         return ret;
 732                 }
 733
 734                 wbc->nr_to_write -= ret;
 735
 736                 cond_resched();
 737         } while (index < end && wbc->nr_to_write > 0);
 738
 739         *_next = index;
 740         _leave(" = 0 [%lx]", *_next);
 741         return 0;
 742 }
 743
 744 /*
 745  * write some of the pending data back to the server
 746  */
 747 int afs_writepages(struct address_space *mapping,
 748                    struct writeback_control *wbc)
 749 {
 750         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 751         pgoff_t start, end, next;
 752         int ret;
 753
 754         _enter("");
 755
 756         /* We have to be careful as we can end up racing with setattr()
 757          * truncating the pagecache since the caller doesn't take a lock here
 758          * to prevent it.
 759          */
 760         if (wbc->sync_mode == WB_SYNC_ALL)
 761                 down_read(&vnode->validate_lock);
 762         else if (!down_read_trylock(&vnode->validate_lock))
 763                 return 0;
 764
 765         if (wbc->range_cyclic) {
 766                 start = mapping->writeback_index;
 767                 end = -1;
 768                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
 769                 if (start > 0 && wbc->nr_to_write > 0 && ret == 0)
 770                         ret = afs_writepages_region(mapping, wbc, 0, start,
 771                                                     &next);
 772                 mapping->writeback_index = next;
 773         } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
 774                 end = (pgoff_t)(LLONG_MAX >> PAGE_SHIFT);
 775                 ret = afs_writepages_region(mapping, wbc, 0, end, &next);
 776                 if (wbc->nr_to_write > 0)
 777                         mapping->writeback_index = next;
 778         } else {
 779                 start = wbc->range_start >> PAGE_SHIFT;
 780                 end = wbc->range_end >> PAGE_SHIFT;
 781                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
 782         }
 783
 784         up_read(&vnode->validate_lock);
 785         _leave(" = %d", ret);
 786         return ret;
 787 }
 788
 789 /*
 790  * write to an AFS file
 791  */
 792 ssize_t afs_file_write(struct kiocb *iocb, struct iov_iter *from)
 793 {
 794         struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp));
 795         ssize_t result;
 796         size_t count = iov_iter_count(from);
 797
 798         _enter("{%llx:%llu},{%zu},",
 799                vnode->fid.vid, vnode->fid.vnode, count);
 800
 801         if (IS_SWAPFILE(&vnode->vfs_inode)) {
 802                 printk(KERN_INFO
 803                        "AFS: Attempt to write to active swap file!\n");
 804                 return -EBUSY;
 805         }
 806
 807         if (!count)
 808                 return 0;
 809
 810         result = generic_file_write_iter(iocb, from);
 811
 812         _leave(" = %zd", result);
 813         return result;
 814 }
 815
 816 /*
 817  * flush any dirty pages for this process, and check for write errors.
 818  * - the return status from this call provides a reliable indication of
 819  *   whether any write errors occurred for this process.
 820  */
 821 int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 822 {
 823         struct inode *inode = file_inode(file);
 824         struct afs_vnode *vnode = AFS_FS_I(inode);
 825
 826         _enter("{%llx:%llu},{n=%pD},%d",
 827                vnode->fid.vid, vnode->fid.vnode, file,
 828                datasync);
 829
 830         return file_write_and_wait_range(file, start, end);
 831 }
 832
 833 /*
 834  * notification that a previously read-only page is about to become writable
 835  * - if it returns an error, the caller will deliver a bus error signal
 836  */
 837 vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
 838 {
 839         struct file *file = vmf->vma->vm_file;
 840         struct inode *inode = file_inode(file);
 841         struct afs_vnode *vnode = AFS_FS_I(inode);
 842         unsigned long priv;
 843
 844         _enter("{{%llx:%llu}},{%lx}",
 845                vnode->fid.vid, vnode->fid.vnode, vmf->page->index);
 846
 847         sb_start_pagefault(inode->i_sb);
 848
 849         /* Wait for the page to be written to the cache before we allow it to
 850          * be modified.  We then assume the entire page will need writing back.
 851          */
 852 #ifdef CONFIG_AFS_FSCACHE
 853         fscache_wait_on_page_write(vnode->cache, vmf->page);
 854 #endif
 855
 856         if (PageWriteback(vmf->page) &&
 857             wait_on_page_bit_killable(vmf->page, PG_writeback) < 0)
 858                 return VM_FAULT_RETRY;
 859
 860         if (lock_page_killable(vmf->page) < 0)
 861                 return VM_FAULT_RETRY;
 862
 863         /* We mustn't change page->private until writeback is complete as that
 864          * details the portion of the page we need to write back and we might
 865          * need to redirty the page if there's a problem.
 866          */
 867         wait_on_page_writeback(vmf->page);
 868
 869         priv = afs_page_dirty(0, PAGE_SIZE);
 870         priv = afs_page_dirty_mmapped(priv);
 871         trace_afs_page_dirty(vnode, tracepoint_string("mkwrite"),
 872                              vmf->page->index, priv);
 873         if (PagePrivate(vmf->page))
 874                 set_page_private(vmf->page, priv);
 875         else
 876                 attach_page_private(vmf->page, (void *)priv);
 877         file_update_time(file);
 878
 879         sb_end_pagefault(inode->i_sb);
 880         return VM_FAULT_LOCKED;
 881 }
 882
 883 /*
 884  * Prune the keys cached for writeback.  The caller must hold vnode->wb_lock.
 885  */
 886 void afs_prune_wb_keys(struct afs_vnode *vnode)
 887 {
 888         LIST_HEAD(graveyard);
 889         struct afs_wb_key *wbk, *tmp;
 890
 891         /* Discard unused keys */
 892         spin_lock(&vnode->wb_lock);
 893
 894         if (!mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_WRITEBACK) &&
 895             !mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_DIRTY)) {
 896                 list_for_each_entry_safe(wbk, tmp, &vnode->wb_keys, vnode_link) {
 897                         if (refcount_read(&wbk->usage) == 1)
 898                                 list_move(&wbk->vnode_link, &graveyard);
 899                 }
 900         }
 901
 902         spin_unlock(&vnode->wb_lock);
 903
 904         while (!list_empty(&graveyard)) {
 905                 wbk = list_entry(graveyard.next, struct afs_wb_key, vnode_link);
 906                 list_del(&wbk->vnode_link);
 907                 afs_put_wb_key(wbk);
 908         }
 909 }
 910
 911 /*
 912  * Clean up a page during invalidation.
 913  */
 914 int afs_launder_page(struct page *page)
 915 {
 916         struct address_space *mapping = page->mapping;
 917         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 918         unsigned long priv;
 919         unsigned int f, t;
 920         int ret = 0;
 921
 922         _enter("{%lx}", page->index);
 923
 924         priv = page_private(page);
 925         if (clear_page_dirty_for_io(page)) {
 926                 f = 0;
 927                 t = PAGE_SIZE;
 928                 if (PagePrivate(page)) {
 929                         f = afs_page_dirty_from(priv);
 930                         t = afs_page_dirty_to(priv);
 931                 }
 932
 933                 trace_afs_page_dirty(vnode, tracepoint_string("launder"),
 934                                      page->index, priv);
 935                 ret = afs_store_data(mapping, page->index, page->index, t, f, true);
 936         }
 937
 938         priv = (unsigned long)detach_page_private(page);
 939         trace_afs_page_dirty(vnode, tracepoint_string("laundered"),
 940                              page->index, priv);
 941
 942 #ifdef CONFIG_AFS_FSCACHE
 943         if (PageFsCache(page)) {
 944                 fscache_wait_on_page_write(vnode->cache, page);
 945                 fscache_uncache_page(vnode->cache, page);
 946         }
 947 #endif
 948         return ret;
 949 }