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 **_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                         i_size_write(&vnode->vfs_inode, 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->store.first = first;
 454         op->store.last = last;
 455         op->store.first_offset = offset;
 456         op->store.last_to = to;
 457         op->store.laundering = laundering;
 458         op->mtime = vnode->vfs_inode.i_mtime;
 459         op->flags |= AFS_OPERATION_UNINTR;
 460         op->ops = &afs_store_data_operation;
 461
 462 try_next_key:
 463         afs_begin_vnode_operation(op);
 464         afs_wait_for_operation(op);
 465
 466         switch (op->error) {
 467         case -EACCES:
 468         case -EPERM:
 469         case -ENOKEY:
 470         case -EKEYEXPIRED:
 471         case -EKEYREJECTED:
 472         case -EKEYREVOKED:
 473                 _debug("next");
 474
 475                 ret = afs_get_writeback_key(vnode, &wbk);
 476                 if (ret == 0) {
 477                         key_put(op->key);
 478                         op->key = key_get(wbk->key);
 479                         goto try_next_key;
 480                 }
 481                 break;
 482         }
 483
 484         afs_put_wb_key(wbk);
 485         _leave(" = %d", op->error);
 486         return afs_put_operation(op);
 487 }
 488
 489 /*
 490  * Synchronously write back the locked page and any subsequent non-locked dirty
 491  * pages.
 492  */
 493 static int afs_write_back_from_locked_page(struct address_space *mapping,
 494                                            struct writeback_control *wbc,
 495                                            struct page *primary_page,
 496                                            pgoff_t final_page)
 497 {
 498         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 499         struct page *pages[8], *page;
 500         unsigned long count, priv;
 501         unsigned n, offset, to, f, t;
 502         pgoff_t start, first, last;
 503         loff_t i_size, end;
 504         int loop, ret;
 505
 506         _enter(",%lx", primary_page->index);
 507
 508         count = 1;
 509         if (test_set_page_writeback(primary_page))
 510                 BUG();
 511
 512         /* Find all consecutive lockable dirty pages that have contiguous
 513          * written regions, stopping when we find a page that is not
 514          * immediately lockable, is not dirty or is missing, or we reach the
 515          * end of the range.
 516          */
 517         start = primary_page->index;
 518         priv = page_private(primary_page);
 519         offset = afs_page_dirty_from(priv);
 520         to = afs_page_dirty_to(priv);
 521         trace_afs_page_dirty(vnode, tracepoint_string("store"),
 522                              primary_page->index, priv);
 523
 524         WARN_ON(offset == to);
 525         if (offset == to)
 526                 trace_afs_page_dirty(vnode, tracepoint_string("WARN"),
 527                                      primary_page->index, priv);
 528
 529         if (start >= final_page ||
 530             (to < PAGE_SIZE && !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)))
 531                 goto no_more;
 532
 533         start++;
 534         do {
 535                 _debug("more %lx [%lx]", start, count);
 536                 n = final_page - start + 1;
 537                 if (n > ARRAY_SIZE(pages))
 538                         n = ARRAY_SIZE(pages);
 539                 n = find_get_pages_contig(mapping, start, ARRAY_SIZE(pages), pages);
 540                 _debug("fgpc %u", n);
 541                 if (n == 0)
 542                         goto no_more;
 543                 if (pages[0]->index != start) {
 544                         do {
 545                                 put_page(pages[--n]);
 546                         } while (n > 0);
 547                         goto no_more;
 548                 }
 549
 550                 for (loop = 0; loop < n; loop++) {
 551                         page = pages[loop];
 552                         if (to != PAGE_SIZE &&
 553                             !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags))
 554                                 break;
 555                         if (page->index > final_page)
 556                                 break;
 557                         if (!trylock_page(page))
 558                                 break;
 559                         if (!PageDirty(page) || PageWriteback(page)) {
 560                                 unlock_page(page);
 561                                 break;
 562                         }
 563
 564                         priv = page_private(page);
 565                         f = afs_page_dirty_from(priv);
 566                         t = afs_page_dirty_to(priv);
 567                         if (f != 0 &&
 568                             !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)) {
 569                                 unlock_page(page);
 570                                 break;
 571                         }
 572                         to = t;
 573
 574                         trace_afs_page_dirty(vnode, tracepoint_string("store+"),
 575                                              page->index, priv);
 576
 577                         if (!clear_page_dirty_for_io(page))
 578                                 BUG();
 579                         if (test_set_page_writeback(page))
 580                                 BUG();
 581                         unlock_page(page);
 582                         put_page(page);
 583                 }
 584                 count += loop;
 585                 if (loop < n) {
 586                         for (; loop < n; loop++)
 587                                 put_page(pages[loop]);
 588                         goto no_more;
 589                 }
 590
 591                 start += loop;
 592         } while (start <= final_page && count < 65536);
 593
 594 no_more:
 595         /* We now have a contiguous set of dirty pages, each with writeback
 596          * set; the first page is still locked at this point, but all the rest
 597          * have been unlocked.
 598          */
 599         unlock_page(primary_page);
 600
 601         first = primary_page->index;
 602         last = first + count - 1;
 603
 604         end = (loff_t)last * PAGE_SIZE + to;
 605         i_size = i_size_read(&vnode->vfs_inode);
 606
 607         _debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to);
 608         if (end > i_size)
 609                 to = i_size & ~PAGE_MASK;
 610
 611         ret = afs_store_data(mapping, first, last, offset, to, false);
 612         switch (ret) {
 613         case 0:
 614                 ret = count;
 615                 break;
 616
 617         default:
 618                 pr_notice("kAFS: Unexpected error from FS.StoreData %d\n", ret);
 619                 fallthrough;
 620         case -EACCES:
 621         case -EPERM:
 622         case -ENOKEY:
 623         case -EKEYEXPIRED:
 624         case -EKEYREJECTED:
 625         case -EKEYREVOKED:
 626                 afs_redirty_pages(wbc, mapping, first, last);
 627                 mapping_set_error(mapping, ret);
 628                 break;
 629
 630         case -EDQUOT:
 631         case -ENOSPC:
 632                 afs_redirty_pages(wbc, mapping, first, last);
 633                 mapping_set_error(mapping, -ENOSPC);
 634                 break;
 635
 636         case -EROFS:
 637         case -EIO:
 638         case -EREMOTEIO:
 639         case -EFBIG:
 640         case -ENOENT:
 641         case -ENOMEDIUM:
 642         case -ENXIO:
 643                 trace_afs_file_error(vnode, ret, afs_file_error_writeback_fail);
 644                 afs_kill_pages(mapping, first, last);
 645                 mapping_set_error(mapping, ret);
 646                 break;
 647         }
 648
 649         _leave(" = %d", ret);
 650         return ret;
 651 }
 652
 653 /*
 654  * write a page back to the server
 655  * - the caller locked the page for us
 656  */
 657 int afs_writepage(struct page *page, struct writeback_control *wbc)
 658 {
 659         int ret;
 660
 661         _enter("{%lx},", page->index);
 662
 663         ret = afs_write_back_from_locked_page(page->mapping, wbc, page,
 664                                               wbc->range_end >> PAGE_SHIFT);
 665         if (ret < 0) {
 666                 _leave(" = %d", ret);
 667                 return 0;
 668         }
 669
 670         wbc->nr_to_write -= ret;
 671
 672         _leave(" = 0");
 673         return 0;
 674 }
 675
 676 /*
 677  * write a region of pages back to the server
 678  */
 679 static int afs_writepages_region(struct address_space *mapping,
 680                                  struct writeback_control *wbc,
 681                                  pgoff_t index, pgoff_t end, pgoff_t *_next)
 682 {
 683         struct page *page;
 684         int ret, n;
 685
 686         _enter(",,%lx,%lx,", index, end);
 687
 688         do {
 689                 n = find_get_pages_range_tag(mapping, &index, end,
 690                                         PAGECACHE_TAG_DIRTY, 1, &page);
 691                 if (!n)
 692                         break;
 693
 694                 _debug("wback %lx", page->index);
 695
 696                 /*
 697                  * at this point we hold neither the i_pages lock nor the
 698                  * page lock: the page may be truncated or invalidated
 699                  * (changing page->mapping to NULL), or even swizzled
 700                  * back from swapper_space to tmpfs file mapping
 701                  */
 702                 ret = lock_page_killable(page);
 703                 if (ret < 0) {
 704                         put_page(page);
 705                         _leave(" = %d", ret);
 706                         return ret;
 707                 }
 708
 709                 if (page->mapping != mapping || !PageDirty(page)) {
 710                         unlock_page(page);
 711                         put_page(page);
 712                         continue;
 713                 }
 714
 715                 if (PageWriteback(page)) {
 716                         unlock_page(page);
 717                         if (wbc->sync_mode != WB_SYNC_NONE)
 718                                 wait_on_page_writeback(page);
 719                         put_page(page);
 720                         continue;
 721                 }
 722
 723                 if (!clear_page_dirty_for_io(page))
 724                         BUG();
 725                 ret = afs_write_back_from_locked_page(mapping, wbc, page, end);
 726                 put_page(page);
 727                 if (ret < 0) {
 728                         _leave(" = %d", ret);
 729                         return ret;
 730                 }
 731
 732                 wbc->nr_to_write -= ret;
 733
 734                 cond_resched();
 735         } while (index < end && wbc->nr_to_write > 0);
 736
 737         *_next = index;
 738         _leave(" = 0 [%lx]", *_next);
 739         return 0;
 740 }
 741
 742 /*
 743  * write some of the pending data back to the server
 744  */
 745 int afs_writepages(struct address_space *mapping,
 746                    struct writeback_control *wbc)
 747 {
 748         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 749         pgoff_t start, end, next;
 750         int ret;
 751
 752         _enter("");
 753
 754         /* We have to be careful as we can end up racing with setattr()
 755          * truncating the pagecache since the caller doesn't take a lock here
 756          * to prevent it.
 757          */
 758         if (wbc->sync_mode == WB_SYNC_ALL)
 759                 down_read(&vnode->validate_lock);
 760         else if (!down_read_trylock(&vnode->validate_lock))
 761                 return 0;
 762
 763         if (wbc->range_cyclic) {
 764                 start = mapping->writeback_index;
 765                 end = -1;
 766                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
 767                 if (start > 0 && wbc->nr_to_write > 0 && ret == 0)
 768                         ret = afs_writepages_region(mapping, wbc, 0, start,
 769                                                     &next);
 770                 mapping->writeback_index = next;
 771         } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
 772                 end = (pgoff_t)(LLONG_MAX >> PAGE_SHIFT);
 773                 ret = afs_writepages_region(mapping, wbc, 0, end, &next);
 774                 if (wbc->nr_to_write > 0)
 775                         mapping->writeback_index = next;
 776         } else {
 777                 start = wbc->range_start >> PAGE_SHIFT;
 778                 end = wbc->range_end >> PAGE_SHIFT;
 779                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
 780         }
 781
 782         up_read(&vnode->validate_lock);
 783         _leave(" = %d", ret);
 784         return ret;
 785 }
 786
 787 /*
 788  * write to an AFS file
 789  */
 790 ssize_t afs_file_write(struct kiocb *iocb, struct iov_iter *from)
 791 {
 792         struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp));
 793         ssize_t result;
 794         size_t count = iov_iter_count(from);
 795
 796         _enter("{%llx:%llu},{%zu},",
 797                vnode->fid.vid, vnode->fid.vnode, count);
 798
 799         if (IS_SWAPFILE(&vnode->vfs_inode)) {
 800                 printk(KERN_INFO
 801                        "AFS: Attempt to write to active swap file!\n");
 802                 return -EBUSY;
 803         }
 804
 805         if (!count)
 806                 return 0;
 807
 808         result = generic_file_write_iter(iocb, from);
 809
 810         _leave(" = %zd", result);
 811         return result;
 812 }
 813
 814 /*
 815  * flush any dirty pages for this process, and check for write errors.
 816  * - the return status from this call provides a reliable indication of
 817  *   whether any write errors occurred for this process.
 818  */
 819 int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 820 {
 821         struct inode *inode = file_inode(file);
 822         struct afs_vnode *vnode = AFS_FS_I(inode);
 823
 824         _enter("{%llx:%llu},{n=%pD},%d",
 825                vnode->fid.vid, vnode->fid.vnode, file,
 826                datasync);
 827
 828         return file_write_and_wait_range(file, start, end);
 829 }
 830
 831 /*
 832  * notification that a previously read-only page is about to become writable
 833  * - if it returns an error, the caller will deliver a bus error signal
 834  */
 835 vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
 836 {
 837         struct file *file = vmf->vma->vm_file;
 838         struct inode *inode = file_inode(file);
 839         struct afs_vnode *vnode = AFS_FS_I(inode);
 840         unsigned long priv;
 841
 842         _enter("{{%llx:%llu}},{%lx}",
 843                vnode->fid.vid, vnode->fid.vnode, vmf->page->index);
 844
 845         sb_start_pagefault(inode->i_sb);
 846
 847         /* Wait for the page to be written to the cache before we allow it to
 848          * be modified.  We then assume the entire page will need writing back.
 849          */
 850 #ifdef CONFIG_AFS_FSCACHE
 851         fscache_wait_on_page_write(vnode->cache, vmf->page);
 852 #endif
 853
 854         if (PageWriteback(vmf->page) &&
 855             wait_on_page_bit_killable(vmf->page, PG_writeback) < 0)
 856                 return VM_FAULT_RETRY;
 857
 858         if (lock_page_killable(vmf->page) < 0)
 859                 return VM_FAULT_RETRY;
 860
 861         /* We mustn't change page->private until writeback is complete as that
 862          * details the portion of the page we need to write back and we might
 863          * need to redirty the page if there's a problem.
 864          */
 865         wait_on_page_writeback(vmf->page);
 866
 867         priv = afs_page_dirty(0, PAGE_SIZE);
 868         priv = afs_page_dirty_mmapped(priv);
 869         trace_afs_page_dirty(vnode, tracepoint_string("mkwrite"),
 870                              vmf->page->index, priv);
 871         if (PagePrivate(vmf->page))
 872                 set_page_private(vmf->page, priv);
 873         else
 874                 attach_page_private(vmf->page, (void *)priv);
 875         file_update_time(file);
 876
 877         sb_end_pagefault(inode->i_sb);
 878         return VM_FAULT_LOCKED;
 879 }
 880
 881 /*
 882  * Prune the keys cached for writeback.  The caller must hold vnode->wb_lock.
 883  */
 884 void afs_prune_wb_keys(struct afs_vnode *vnode)
 885 {
 886         LIST_HEAD(graveyard);
 887         struct afs_wb_key *wbk, *tmp;
 888
 889         /* Discard unused keys */
 890         spin_lock(&vnode->wb_lock);
 891
 892         if (!mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_WRITEBACK) &&
 893             !mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_DIRTY)) {
 894                 list_for_each_entry_safe(wbk, tmp, &vnode->wb_keys, vnode_link) {
 895                         if (refcount_read(&wbk->usage) == 1)
 896                                 list_move(&wbk->vnode_link, &graveyard);
 897                 }
 898         }
 899
 900         spin_unlock(&vnode->wb_lock);
 901
 902         while (!list_empty(&graveyard)) {
 903                 wbk = list_entry(graveyard.next, struct afs_wb_key, vnode_link);
 904                 list_del(&wbk->vnode_link);
 905                 afs_put_wb_key(wbk);
 906         }
 907 }
 908
 909 /*
 910  * Clean up a page during invalidation.
 911  */
 912 int afs_launder_page(struct page *page)
 913 {
 914         struct address_space *mapping = page->mapping;
 915         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 916         unsigned long priv;
 917         unsigned int f, t;
 918         int ret = 0;
 919
 920         _enter("{%lx}", page->index);
 921
 922         priv = page_private(page);
 923         if (clear_page_dirty_for_io(page)) {
 924                 f = 0;
 925                 t = PAGE_SIZE;
 926                 if (PagePrivate(page)) {
 927                         f = afs_page_dirty_from(priv);
 928                         t = afs_page_dirty_to(priv);
 929                 }
 930
 931                 trace_afs_page_dirty(vnode, tracepoint_string("launder"),
 932                                      page->index, priv);
 933                 ret = afs_store_data(mapping, page->index, page->index, t, f, true);
 934         }
 935
 936         priv = (unsigned long)detach_page_private(page);
 937         trace_afs_page_dirty(vnode, tracepoint_string("laundered"),
 938                              page->index, priv);
 939
 940 #ifdef CONFIG_AFS_FSCACHE
 941         if (PageFsCache(page)) {
 942                 fscache_wait_on_page_write(vnode->cache, page);
 943                 fscache_uncache_page(vnode->cache, page);
 944         }
 945 #endif
 946         return ret;
 947 }