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 ([email protected])
   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 **pagep, 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 > 32768 && 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         /* page won't leak in error case: it eventually gets cleaned off LRU */
 114         *pagep = page;
 115
 116 try_again:
 117         /* See if this page is already partially written in a way that we can
 118          * merge the new write with.
 119          */
 120         t = f = 0;
 121         if (PagePrivate(page)) {
 122                 priv = page_private(page);
 123                 f = priv & AFS_PRIV_MAX;
 124                 t = priv >> AFS_PRIV_SHIFT;
 125                 ASSERTCMP(f, <=, t);
 126         }
 127
 128         if (f != t) {
 129                 if (PageWriteback(page)) {
 130                         trace_afs_page_dirty(vnode, tracepoint_string("alrdy"),
 131                                              page->index, priv);
 132                         goto flush_conflicting_write;
 133                 }
 134                 /* If the file is being filled locally, allow inter-write
 135                  * spaces to be merged into writes.  If it's not, only write
 136                  * back what the user gives us.
 137                  */
 138                 if (!test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags) &&
 139                     (to < f || from > t))
 140                         goto flush_conflicting_write;
 141                 if (from < f)
 142                         f = from;
 143                 if (to > t)
 144                         t = to;
 145         } else {
 146                 f = from;
 147                 t = to;
 148         }
 149
 150         priv = (unsigned long)t << AFS_PRIV_SHIFT;
 151         priv |= f;
 152         trace_afs_page_dirty(vnode, tracepoint_string("begin"),
 153                              page->index, priv);
 154         SetPagePrivate(page);
 155         set_page_private(page, priv);
 156         _leave(" = 0");
 157         return 0;
 158
 159         /* The previous write and this write aren't adjacent or overlapping, so
 160          * flush the page out.
 161          */
 162 flush_conflicting_write:
 163         _debug("flush conflict");
 164         ret = write_one_page(page);
 165         if (ret < 0) {
 166                 _leave(" = %d", ret);
 167                 return ret;
 168         }
 169
 170         ret = lock_page_killable(page);
 171         if (ret < 0) {
 172                 _leave(" = %d", ret);
 173                 return ret;
 174         }
 175         goto try_again;
 176 }
 177
 178 /*
 179  * finalise part of a write to a page
 180  */
 181 int afs_write_end(struct file *file, struct address_space *mapping,
 182                   loff_t pos, unsigned len, unsigned copied,
 183                   struct page *page, void *fsdata)
 184 {
 185         struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
 186         struct key *key = afs_file_key(file);
 187         loff_t i_size, maybe_i_size;
 188         int ret;
 189
 190         _enter("{%llx:%llu},{%lx}",
 191                vnode->fid.vid, vnode->fid.vnode, page->index);
 192
 193         maybe_i_size = pos + copied;
 194
 195         i_size = i_size_read(&vnode->vfs_inode);
 196         if (maybe_i_size > i_size) {
 197                 write_seqlock(&vnode->cb_lock);
 198                 i_size = i_size_read(&vnode->vfs_inode);
 199                 if (maybe_i_size > i_size)
 200                         i_size_write(&vnode->vfs_inode, maybe_i_size);
 201                 write_sequnlock(&vnode->cb_lock);
 202         }
 203
 204         if (!PageUptodate(page)) {
 205                 if (copied < len) {
 206                         /* Try and load any missing data from the server.  The
 207                          * unmarshalling routine will take care of clearing any
 208                          * bits that are beyond the EOF.
 209                          */
 210                         ret = afs_fill_page(vnode, key, pos + copied,
 211                                             len - copied, page);
 212                         if (ret < 0)
 213                                 goto out;
 214                 }
 215                 SetPageUptodate(page);
 216         }
 217
 218         set_page_dirty(page);
 219         if (PageDirty(page))
 220                 _debug("dirtied");
 221         ret = copied;
 222
 223 out:
 224         unlock_page(page);
 225         put_page(page);
 226         return ret;
 227 }
 228
 229 /*
 230  * kill all the pages in the given range
 231  */
 232 static void afs_kill_pages(struct address_space *mapping,
 233                            pgoff_t first, pgoff_t last)
 234 {
 235         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 236         struct pagevec pv;
 237         unsigned count, loop;
 238
 239         _enter("{%llx:%llu},%lx-%lx",
 240                vnode->fid.vid, vnode->fid.vnode, first, last);
 241
 242         pagevec_init(&pv);
 243
 244         do {
 245                 _debug("kill %lx-%lx", first, last);
 246
 247                 count = last - first + 1;
 248                 if (count > PAGEVEC_SIZE)
 249                         count = PAGEVEC_SIZE;
 250                 pv.nr = find_get_pages_contig(mapping, first, count, pv.pages);
 251                 ASSERTCMP(pv.nr, ==, count);
 252
 253                 for (loop = 0; loop < count; loop++) {
 254                         struct page *page = pv.pages[loop];
 255                         ClearPageUptodate(page);
 256                         SetPageError(page);
 257                         end_page_writeback(page);
 258                         if (page->index >= first)
 259                                 first = page->index + 1;
 260                         lock_page(page);
 261                         generic_error_remove_page(mapping, page);
 262                         unlock_page(page);
 263                 }
 264
 265                 __pagevec_release(&pv);
 266         } while (first <= last);
 267
 268         _leave("");
 269 }
 270
 271 /*
 272  * Redirty all the pages in a given range.
 273  */
 274 static void afs_redirty_pages(struct writeback_control *wbc,
 275                               struct address_space *mapping,
 276                               pgoff_t first, pgoff_t last)
 277 {
 278         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 279         struct pagevec pv;
 280         unsigned count, loop;
 281
 282         _enter("{%llx:%llu},%lx-%lx",
 283                vnode->fid.vid, vnode->fid.vnode, first, last);
 284
 285         pagevec_init(&pv);
 286
 287         do {
 288                 _debug("redirty %lx-%lx", first, last);
 289
 290                 count = last - first + 1;
 291                 if (count > PAGEVEC_SIZE)
 292                         count = PAGEVEC_SIZE;
 293                 pv.nr = find_get_pages_contig(mapping, first, count, pv.pages);
 294                 ASSERTCMP(pv.nr, ==, count);
 295
 296                 for (loop = 0; loop < count; loop++) {
 297                         struct page *page = pv.pages[loop];
 298
 299                         redirty_page_for_writepage(wbc, page);
 300                         end_page_writeback(page);
 301                         if (page->index >= first)
 302                                 first = page->index + 1;
 303                 }
 304
 305                 __pagevec_release(&pv);
 306         } while (first <= last);
 307
 308         _leave("");
 309 }
 310
 311 /*
 312  * completion of write to server
 313  */
 314 static void afs_pages_written_back(struct afs_vnode *vnode,
 315                                    pgoff_t first, pgoff_t last)
 316 {
 317         struct pagevec pv;
 318         unsigned long priv;
 319         unsigned count, loop;
 320
 321         _enter("{%llx:%llu},{%lx-%lx}",
 322                vnode->fid.vid, vnode->fid.vnode, first, last);
 323
 324         pagevec_init(&pv);
 325
 326         do {
 327                 _debug("done %lx-%lx", first, last);
 328
 329                 count = last - first + 1;
 330                 if (count > PAGEVEC_SIZE)
 331                         count = PAGEVEC_SIZE;
 332                 pv.nr = find_get_pages_contig(vnode->vfs_inode.i_mapping,
 333                                               first, count, pv.pages);
 334                 ASSERTCMP(pv.nr, ==, count);
 335
 336                 for (loop = 0; loop < count; loop++) {
 337                         priv = page_private(pv.pages[loop]);
 338                         trace_afs_page_dirty(vnode, tracepoint_string("clear"),
 339                                              pv.pages[loop]->index, priv);
 340                         set_page_private(pv.pages[loop], 0);
 341                         end_page_writeback(pv.pages[loop]);
 342                 }
 343                 first += count;
 344                 __pagevec_release(&pv);
 345         } while (first <= last);
 346
 347         afs_prune_wb_keys(vnode);
 348         _leave("");
 349 }
 350
 351 /*
 352  * Find a key to use for the writeback.  We cached the keys used to author the
 353  * writes on the vnode.  *_wbk will contain the last writeback key used or NULL
 354  * and we need to start from there if it's set.
 355  */
 356 static int afs_get_writeback_key(struct afs_vnode *vnode,
 357                                  struct afs_wb_key **_wbk)
 358 {
 359         struct afs_wb_key *wbk = NULL;
 360         struct list_head *p;
 361         int ret = -ENOKEY, ret2;
 362
 363         spin_lock(&vnode->wb_lock);
 364         if (*_wbk)
 365                 p = (*_wbk)->vnode_link.next;
 366         else
 367                 p = vnode->wb_keys.next;
 368
 369         while (p != &vnode->wb_keys) {
 370                 wbk = list_entry(p, struct afs_wb_key, vnode_link);
 371                 _debug("wbk %u", key_serial(wbk->key));
 372                 ret2 = key_validate(wbk->key);
 373                 if (ret2 == 0) {
 374                         refcount_inc(&wbk->usage);
 375                         _debug("USE WB KEY %u", key_serial(wbk->key));
 376                         break;
 377                 }
 378
 379                 wbk = NULL;
 380                 if (ret == -ENOKEY)
 381                         ret = ret2;
 382                 p = p->next;
 383         }
 384
 385         spin_unlock(&vnode->wb_lock);
 386         if (*_wbk)
 387                 afs_put_wb_key(*_wbk);
 388         *_wbk = wbk;
 389         return 0;
 390 }
 391
 392 static void afs_store_data_success(struct afs_operation *op)
 393 {
 394         struct afs_vnode *vnode = op->file[0].vnode;
 395
 396         op->ctime = op->file[0].scb.status.mtime_client;
 397         afs_vnode_commit_status(op, &op->file[0]);
 398         if (op->error == 0) {
 399                 afs_pages_written_back(vnode, op->store.first, op->store.last);
 400                 afs_stat_v(vnode, n_stores);
 401                 atomic_long_add((op->store.last * PAGE_SIZE + op->store.last_to) -
 402                                 (op->store.first * PAGE_SIZE + op->store.first_offset),
 403                                 &afs_v2net(vnode)->n_store_bytes);
 404         }
 405 }
 406
 407 static const struct afs_operation_ops afs_store_data_operation = {
 408         .issue_afs_rpc  = afs_fs_store_data,
 409         .issue_yfs_rpc  = yfs_fs_store_data,
 410         .success        = afs_store_data_success,
 411 };
 412
 413 /*
 414  * write to a file
 415  */
 416 static int afs_store_data(struct address_space *mapping,
 417                           pgoff_t first, pgoff_t last,
 418                           unsigned offset, unsigned to)
 419 {
 420         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 421         struct afs_operation *op;
 422         struct afs_wb_key *wbk = NULL;
 423         int ret;
 424
 425         _enter("%s{%llx:%llu.%u},%lx,%lx,%x,%x",
 426                vnode->volume->name,
 427                vnode->fid.vid,
 428                vnode->fid.vnode,
 429                vnode->fid.unique,
 430                first, last, offset, to);
 431
 432         ret = afs_get_writeback_key(vnode, &wbk);
 433         if (ret) {
 434                 _leave(" = %d [no keys]", ret);
 435                 return ret;
 436         }
 437
 438         op = afs_alloc_operation(wbk->key, vnode->volume);
 439         if (IS_ERR(op)) {
 440                 afs_put_wb_key(wbk);
 441                 return -ENOMEM;
 442         }
 443
 444         afs_op_set_vnode(op, 0, vnode);
 445         op->file[0].dv_delta = 1;
 446         op->store.mapping = mapping;
 447         op->store.first = first;
 448         op->store.last = last;
 449         op->store.first_offset = offset;
 450         op->store.last_to = to;
 451         op->mtime = vnode->vfs_inode.i_mtime;
 452         op->ops = &afs_store_data_operation;
 453
 454 try_next_key:
 455         afs_begin_vnode_operation(op);
 456         afs_wait_for_operation(op);
 457
 458         switch (op->error) {
 459         case -EACCES:
 460         case -EPERM:
 461         case -ENOKEY:
 462         case -EKEYEXPIRED:
 463         case -EKEYREJECTED:
 464         case -EKEYREVOKED:
 465                 _debug("next");
 466
 467                 ret = afs_get_writeback_key(vnode, &wbk);
 468                 if (ret == 0) {
 469                         key_put(op->key);
 470                         op->key = key_get(wbk->key);
 471                         goto try_next_key;
 472                 }
 473                 break;
 474         }
 475
 476         afs_put_wb_key(wbk);
 477         _leave(" = %d", op->error);
 478         return afs_put_operation(op);
 479 }
 480
 481 /*
 482  * Synchronously write back the locked page and any subsequent non-locked dirty
 483  * pages.
 484  */
 485 static int afs_write_back_from_locked_page(struct address_space *mapping,
 486                                            struct writeback_control *wbc,
 487                                            struct page *primary_page,
 488                                            pgoff_t final_page)
 489 {
 490         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 491         struct page *pages[8], *page;
 492         unsigned long count, priv;
 493         unsigned n, offset, to, f, t;
 494         pgoff_t start, first, last;
 495         loff_t i_size, end;
 496         int loop, ret;
 497
 498         _enter(",%lx", primary_page->index);
 499
 500         count = 1;
 501         if (test_set_page_writeback(primary_page))
 502                 BUG();
 503
 504         /* Find all consecutive lockable dirty pages that have contiguous
 505          * written regions, stopping when we find a page that is not
 506          * immediately lockable, is not dirty or is missing, or we reach the
 507          * end of the range.
 508          */
 509         start = primary_page->index;
 510         priv = page_private(primary_page);
 511         offset = priv & AFS_PRIV_MAX;
 512         to = priv >> AFS_PRIV_SHIFT;
 513         trace_afs_page_dirty(vnode, tracepoint_string("store"),
 514                              primary_page->index, priv);
 515
 516         WARN_ON(offset == to);
 517         if (offset == to)
 518                 trace_afs_page_dirty(vnode, tracepoint_string("WARN"),
 519                                      primary_page->index, priv);
 520
 521         if (start >= final_page ||
 522             (to < PAGE_SIZE && !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)))
 523                 goto no_more;
 524
 525         start++;
 526         do {
 527                 _debug("more %lx [%lx]", start, count);
 528                 n = final_page - start + 1;
 529                 if (n > ARRAY_SIZE(pages))
 530                         n = ARRAY_SIZE(pages);
 531                 n = find_get_pages_contig(mapping, start, ARRAY_SIZE(pages), pages);
 532                 _debug("fgpc %u", n);
 533                 if (n == 0)
 534                         goto no_more;
 535                 if (pages[0]->index != start) {
 536                         do {
 537                                 put_page(pages[--n]);
 538                         } while (n > 0);
 539                         goto no_more;
 540                 }
 541
 542                 for (loop = 0; loop < n; loop++) {
 543                         page = pages[loop];
 544                         if (to != PAGE_SIZE &&
 545                             !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags))
 546                                 break;
 547                         if (page->index > final_page)
 548                                 break;
 549                         if (!trylock_page(page))
 550                                 break;
 551                         if (!PageDirty(page) || PageWriteback(page)) {
 552                                 unlock_page(page);
 553                                 break;
 554                         }
 555
 556                         priv = page_private(page);
 557                         f = priv & AFS_PRIV_MAX;
 558                         t = priv >> AFS_PRIV_SHIFT;
 559                         if (f != 0 &&
 560                             !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)) {
 561                                 unlock_page(page);
 562                                 break;
 563                         }
 564                         to = t;
 565
 566                         trace_afs_page_dirty(vnode, tracepoint_string("store+"),
 567                                              page->index, priv);
 568
 569                         if (!clear_page_dirty_for_io(page))
 570                                 BUG();
 571                         if (test_set_page_writeback(page))
 572                                 BUG();
 573                         unlock_page(page);
 574                         put_page(page);
 575                 }
 576                 count += loop;
 577                 if (loop < n) {
 578                         for (; loop < n; loop++)
 579                                 put_page(pages[loop]);
 580                         goto no_more;
 581                 }
 582
 583                 start += loop;
 584         } while (start <= final_page && count < 65536);
 585
 586 no_more:
 587         /* We now have a contiguous set of dirty pages, each with writeback
 588          * set; the first page is still locked at this point, but all the rest
 589          * have been unlocked.
 590          */
 591         unlock_page(primary_page);
 592
 593         first = primary_page->index;
 594         last = first + count - 1;
 595
 596         end = (loff_t)last * PAGE_SIZE + to;
 597         i_size = i_size_read(&vnode->vfs_inode);
 598
 599         _debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to);
 600         if (end > i_size)
 601                 to = i_size & ~PAGE_MASK;
 602
 603         ret = afs_store_data(mapping, first, last, offset, to);
 604         switch (ret) {
 605         case 0:
 606                 ret = count;
 607                 break;
 608
 609         default:
 610                 pr_notice("kAFS: Unexpected error from FS.StoreData %d\n", ret);
 611                 /* Fall through */
 612         case -EACCES:
 613         case -EPERM:
 614         case -ENOKEY:
 615         case -EKEYEXPIRED:
 616         case -EKEYREJECTED:
 617         case -EKEYREVOKED:
 618                 afs_redirty_pages(wbc, mapping, first, last);
 619                 mapping_set_error(mapping, ret);
 620                 break;
 621
 622         case -EDQUOT:
 623         case -ENOSPC:
 624                 afs_redirty_pages(wbc, mapping, first, last);
 625                 mapping_set_error(mapping, -ENOSPC);
 626                 break;
 627
 628         case -EROFS:
 629         case -EIO:
 630         case -EREMOTEIO:
 631         case -EFBIG:
 632         case -ENOENT:
 633         case -ENOMEDIUM:
 634         case -ENXIO:
 635                 trace_afs_file_error(vnode, ret, afs_file_error_writeback_fail);
 636                 afs_kill_pages(mapping, first, last);
 637                 mapping_set_error(mapping, ret);
 638                 break;
 639         }
 640
 641         _leave(" = %d", ret);
 642         return ret;
 643 }
 644
 645 /*
 646  * write a page back to the server
 647  * - the caller locked the page for us
 648  */
 649 int afs_writepage(struct page *page, struct writeback_control *wbc)
 650 {
 651         int ret;
 652
 653         _enter("{%lx},", page->index);
 654
 655         ret = afs_write_back_from_locked_page(page->mapping, wbc, page,
 656                                               wbc->range_end >> PAGE_SHIFT);
 657         if (ret < 0) {
 658                 _leave(" = %d", ret);
 659                 return 0;
 660         }
 661
 662         wbc->nr_to_write -= ret;
 663
 664         _leave(" = 0");
 665         return 0;
 666 }
 667
 668 /*
 669  * write a region of pages back to the server
 670  */
 671 static int afs_writepages_region(struct address_space *mapping,
 672                                  struct writeback_control *wbc,
 673                                  pgoff_t index, pgoff_t end, pgoff_t *_next)
 674 {
 675         struct page *page;
 676         int ret, n;
 677
 678         _enter(",,%lx,%lx,", index, end);
 679
 680         do {
 681                 n = find_get_pages_range_tag(mapping, &index, end,
 682                                         PAGECACHE_TAG_DIRTY, 1, &page);
 683                 if (!n)
 684                         break;
 685
 686                 _debug("wback %lx", page->index);
 687
 688                 /*
 689                  * at this point we hold neither the i_pages lock nor the
 690                  * page lock: the page may be truncated or invalidated
 691                  * (changing page->mapping to NULL), or even swizzled
 692                  * back from swapper_space to tmpfs file mapping
 693                  */
 694                 ret = lock_page_killable(page);
 695                 if (ret < 0) {
 696                         put_page(page);
 697                         _leave(" = %d", ret);
 698                         return ret;
 699                 }
 700
 701                 if (page->mapping != mapping || !PageDirty(page)) {
 702                         unlock_page(page);
 703                         put_page(page);
 704                         continue;
 705                 }
 706
 707                 if (PageWriteback(page)) {
 708                         unlock_page(page);
 709                         if (wbc->sync_mode != WB_SYNC_NONE)
 710                                 wait_on_page_writeback(page);
 711                         put_page(page);
 712                         continue;
 713                 }
 714
 715                 if (!clear_page_dirty_for_io(page))
 716                         BUG();
 717                 ret = afs_write_back_from_locked_page(mapping, wbc, page, end);
 718                 put_page(page);
 719                 if (ret < 0) {
 720                         _leave(" = %d", ret);
 721                         return ret;
 722                 }
 723
 724                 wbc->nr_to_write -= ret;
 725
 726                 cond_resched();
 727         } while (index < end && wbc->nr_to_write > 0);
 728
 729         *_next = index;
 730         _leave(" = 0 [%lx]", *_next);
 731         return 0;
 732 }
 733
 734 /*
 735  * write some of the pending data back to the server
 736  */
 737 int afs_writepages(struct address_space *mapping,
 738                    struct writeback_control *wbc)
 739 {
 740         pgoff_t start, end, next;
 741         int ret;
 742
 743         _enter("");
 744
 745         if (wbc->range_cyclic) {
 746                 start = mapping->writeback_index;
 747                 end = -1;
 748                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
 749                 if (start > 0 && wbc->nr_to_write > 0 && ret == 0)
 750                         ret = afs_writepages_region(mapping, wbc, 0, start,
 751                                                     &next);
 752                 mapping->writeback_index = next;
 753         } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
 754                 end = (pgoff_t)(LLONG_MAX >> PAGE_SHIFT);
 755                 ret = afs_writepages_region(mapping, wbc, 0, end, &next);
 756                 if (wbc->nr_to_write > 0)
 757                         mapping->writeback_index = next;
 758         } else {
 759                 start = wbc->range_start >> PAGE_SHIFT;
 760                 end = wbc->range_end >> PAGE_SHIFT;
 761                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
 762         }
 763
 764         _leave(" = %d", ret);
 765         return ret;
 766 }
 767
 768 /*
 769  * write to an AFS file
 770  */
 771 ssize_t afs_file_write(struct kiocb *iocb, struct iov_iter *from)
 772 {
 773         struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp));
 774         ssize_t result;
 775         size_t count = iov_iter_count(from);
 776
 777         _enter("{%llx:%llu},{%zu},",
 778                vnode->fid.vid, vnode->fid.vnode, count);
 779
 780         if (IS_SWAPFILE(&vnode->vfs_inode)) {
 781                 printk(KERN_INFO
 782                        "AFS: Attempt to write to active swap file!\n");
 783                 return -EBUSY;
 784         }
 785
 786         if (!count)
 787                 return 0;
 788
 789         result = generic_file_write_iter(iocb, from);
 790
 791         _leave(" = %zd", result);
 792         return result;
 793 }
 794
 795 /*
 796  * flush any dirty pages for this process, and check for write errors.
 797  * - the return status from this call provides a reliable indication of
 798  *   whether any write errors occurred for this process.
 799  */
 800 int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 801 {
 802         struct inode *inode = file_inode(file);
 803         struct afs_vnode *vnode = AFS_FS_I(inode);
 804
 805         _enter("{%llx:%llu},{n=%pD},%d",
 806                vnode->fid.vid, vnode->fid.vnode, file,
 807                datasync);
 808
 809         return file_write_and_wait_range(file, start, end);
 810 }
 811
 812 /*
 813  * notification that a previously read-only page is about to become writable
 814  * - if it returns an error, the caller will deliver a bus error signal
 815  */
 816 vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
 817 {
 818         struct file *file = vmf->vma->vm_file;
 819         struct inode *inode = file_inode(file);
 820         struct afs_vnode *vnode = AFS_FS_I(inode);
 821         unsigned long priv;
 822
 823         _enter("{{%llx:%llu}},{%lx}",
 824                vnode->fid.vid, vnode->fid.vnode, vmf->page->index);
 825
 826         sb_start_pagefault(inode->i_sb);
 827
 828         /* Wait for the page to be written to the cache before we allow it to
 829          * be modified.  We then assume the entire page will need writing back.
 830          */
 831 #ifdef CONFIG_AFS_FSCACHE
 832         fscache_wait_on_page_write(vnode->cache, vmf->page);
 833 #endif
 834
 835         if (PageWriteback(vmf->page) &&
 836             wait_on_page_bit_killable(vmf->page, PG_writeback) < 0)
 837                 return VM_FAULT_RETRY;
 838
 839         if (lock_page_killable(vmf->page) < 0)
 840                 return VM_FAULT_RETRY;
 841
 842         /* We mustn't change page->private until writeback is complete as that
 843          * details the portion of the page we need to write back and we might
 844          * need to redirty the page if there's a problem.
 845          */
 846         wait_on_page_writeback(vmf->page);
 847
 848         priv = (unsigned long)PAGE_SIZE << AFS_PRIV_SHIFT; /* To */
 849         priv |= 0; /* From */
 850         trace_afs_page_dirty(vnode, tracepoint_string("mkwrite"),
 851                              vmf->page->index, priv);
 852         SetPagePrivate(vmf->page);
 853         set_page_private(vmf->page, priv);
 854         file_update_time(file);
 855
 856         sb_end_pagefault(inode->i_sb);
 857         return VM_FAULT_LOCKED;
 858 }
 859
 860 /*
 861  * Prune the keys cached for writeback.  The caller must hold vnode->wb_lock.
 862  */
 863 void afs_prune_wb_keys(struct afs_vnode *vnode)
 864 {
 865         LIST_HEAD(graveyard);
 866         struct afs_wb_key *wbk, *tmp;
 867
 868         /* Discard unused keys */
 869         spin_lock(&vnode->wb_lock);
 870
 871         if (!mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_WRITEBACK) &&
 872             !mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_DIRTY)) {
 873                 list_for_each_entry_safe(wbk, tmp, &vnode->wb_keys, vnode_link) {
 874                         if (refcount_read(&wbk->usage) == 1)
 875                                 list_move(&wbk->vnode_link, &graveyard);
 876                 }
 877         }
 878
 879         spin_unlock(&vnode->wb_lock);
 880
 881         while (!list_empty(&graveyard)) {
 882                 wbk = list_entry(graveyard.next, struct afs_wb_key, vnode_link);
 883                 list_del(&wbk->vnode_link);
 884                 afs_put_wb_key(wbk);
 885         }
 886 }
 887
 888 /*
 889  * Clean up a page during invalidation.
 890  */
 891 int afs_launder_page(struct page *page)
 892 {
 893         struct address_space *mapping = page->mapping;
 894         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 895         unsigned long priv;
 896         unsigned int f, t;
 897         int ret = 0;
 898
 899         _enter("{%lx}", page->index);
 900
 901         priv = page_private(page);
 902         if (clear_page_dirty_for_io(page)) {
 903                 f = 0;
 904                 t = PAGE_SIZE;
 905                 if (PagePrivate(page)) {
 906                         f = priv & AFS_PRIV_MAX;
 907                         t = priv >> AFS_PRIV_SHIFT;
 908                 }
 909
 910                 trace_afs_page_dirty(vnode, tracepoint_string("launder"),
 911                                      page->index, priv);
 912                 ret = afs_store_data(mapping, page->index, page->index, t, f);
 913         }
 914
 915         trace_afs_page_dirty(vnode, tracepoint_string("laundered"),
 916                              page->index, priv);
 917         set_page_private(page, 0);
 918         ClearPagePrivate(page);
 919
 920 #ifdef CONFIG_AFS_FSCACHE
 921         if (PageFsCache(page)) {
 922                 fscache_wait_on_page_write(vnode->cache, page);
 923                 fscache_uncache_page(vnode->cache, page);
 924         }
 925 #endif
 926         return ret;
 927 }