fs/afs/write.c

   1 /* handling of writes to regular files and writing back to the server
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #include <linux/backing-dev.h>
  13 #include <linux/slab.h>
  14 #include <linux/fs.h>
  15 #include <linux/pagemap.h>
  16 #include <linux/writeback.h>
  17 #include <linux/pagevec.h>
  18 #include "internal.h"
  19
  20 /*
  21  * mark a page as having been made dirty and thus needing writeback
  22  */
  23 int afs_set_page_dirty(struct page *page)
  24 {
  25         _enter("");
  26         return __set_page_dirty_nobuffers(page);
  27 }
  28
  29 /*
  30  * partly or wholly fill a page that's under preparation for writing
  31  */
  32 static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
  33                          loff_t pos, unsigned int len, struct page *page)
  34 {
  35         struct afs_read *req;
  36         int ret;
  37
  38         _enter(",,%llu", (unsigned long long)pos);
  39
  40         req = kzalloc(sizeof(struct afs_read) + sizeof(struct page *),
  41                       GFP_KERNEL);
  42         if (!req)
  43                 return -ENOMEM;
  44
  45         refcount_set(&req->usage, 1);
  46         req->pos = pos;
  47         req->len = len;
  48         req->nr_pages = 1;
  49         req->pages = req->array;
  50         req->pages[0] = page;
  51         get_page(page);
  52
  53         ret = afs_fetch_data(vnode, key, req);
  54         afs_put_read(req);
  55         if (ret < 0) {
  56                 if (ret == -ENOENT) {
  57                         _debug("got NOENT from server"
  58                                " - marking file deleted and stale");
  59                         set_bit(AFS_VNODE_DELETED, &vnode->flags);
  60                         ret = -ESTALE;
  61                 }
  62         }
  63
  64         _leave(" = %d", ret);
  65         return ret;
  66 }
  67
  68 /*
  69  * prepare to perform part of a write to a page
  70  */
  71 int afs_write_begin(struct file *file, struct address_space *mapping,
  72                     loff_t pos, unsigned len, unsigned flags,
  73                     struct page **pagep, void **fsdata)
  74 {
  75         struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
  76         struct page *page;
  77         struct key *key = afs_file_key(file);
  78         unsigned long priv;
  79         unsigned f, from = pos & (PAGE_SIZE - 1);
  80         unsigned t, to = from + len;
  81         pgoff_t index = pos >> PAGE_SHIFT;
  82         int ret;
  83
  84         _enter("{%x:%u},{%lx},%u,%u",
  85                vnode->fid.vid, vnode->fid.vnode, index, from, to);
  86
  87         /* We want to store information about how much of a page is altered in
  88          * page->private.
  89          */
  90         BUILD_BUG_ON(PAGE_SIZE > 32768 && sizeof(page->private) < 8);
  91
  92         page = grab_cache_page_write_begin(mapping, index, flags);
  93         if (!page)
  94                 return -ENOMEM;
  95
  96         if (!PageUptodate(page) && len != PAGE_SIZE) {
  97                 ret = afs_fill_page(vnode, key, pos & PAGE_MASK, PAGE_SIZE, page);
  98                 if (ret < 0) {
  99                         unlock_page(page);
 100                         put_page(page);
 101                         _leave(" = %d [prep]", ret);
 102                         return ret;
 103                 }
 104                 SetPageUptodate(page);
 105         }
 106
 107         /* page won't leak in error case: it eventually gets cleaned off LRU */
 108         *pagep = page;
 109
 110 try_again:
 111         /* See if this page is already partially written in a way that we can
 112          * merge the new write with.
 113          */
 114         t = f = 0;
 115         if (PagePrivate(page)) {
 116                 priv = page_private(page);
 117                 f = priv & AFS_PRIV_MAX;
 118                 t = priv >> AFS_PRIV_SHIFT;
 119                 ASSERTCMP(f, <=, t);
 120         }
 121
 122         if (f != t) {
 123                 if (PageWriteback(page)) {
 124                         trace_afs_page_dirty(vnode, tracepoint_string("alrdy"),
 125                                              page->index, priv);
 126                         goto flush_conflicting_write;
 127                 }
 128                 /* If the file is being filled locally, allow inter-write
 129                  * spaces to be merged into writes.  If it's not, only write
 130                  * back what the user gives us.
 131                  */
 132                 if (!test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags) &&
 133                     (to < f || from > t))
 134                         goto flush_conflicting_write;
 135                 if (from < f)
 136                         f = from;
 137                 if (to > t)
 138                         t = to;
 139         } else {
 140                 f = from;
 141                 t = to;
 142         }
 143
 144         priv = (unsigned long)t << AFS_PRIV_SHIFT;
 145         priv |= f;
 146         trace_afs_page_dirty(vnode, tracepoint_string("begin"),
 147                              page->index, priv);
 148         SetPagePrivate(page);
 149         set_page_private(page, priv);
 150         _leave(" = 0");
 151         return 0;
 152
 153         /* The previous write and this write aren't adjacent or overlapping, so
 154          * flush the page out.
 155          */
 156 flush_conflicting_write:
 157         _debug("flush conflict");
 158         ret = write_one_page(page);
 159         if (ret < 0) {
 160                 _leave(" = %d", ret);
 161                 return ret;
 162         }
 163
 164         ret = lock_page_killable(page);
 165         if (ret < 0) {
 166                 _leave(" = %d", ret);
 167                 return ret;
 168         }
 169         goto try_again;
 170 }
 171
 172 /*
 173  * finalise part of a write to a page
 174  */
 175 int afs_write_end(struct file *file, struct address_space *mapping,
 176                   loff_t pos, unsigned len, unsigned copied,
 177                   struct page *page, void *fsdata)
 178 {
 179         struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
 180         struct key *key = afs_file_key(file);
 181         loff_t i_size, maybe_i_size;
 182         int ret;
 183
 184         _enter("{%x:%u},{%lx}",
 185                vnode->fid.vid, vnode->fid.vnode, page->index);
 186
 187         maybe_i_size = pos + copied;
 188
 189         i_size = i_size_read(&vnode->vfs_inode);
 190         if (maybe_i_size > i_size) {
 191                 spin_lock(&vnode->wb_lock);
 192                 i_size = i_size_read(&vnode->vfs_inode);
 193                 if (maybe_i_size > i_size)
 194                         i_size_write(&vnode->vfs_inode, maybe_i_size);
 195                 spin_unlock(&vnode->wb_lock);
 196         }
 197
 198         if (!PageUptodate(page)) {
 199                 if (copied < len) {
 200                         /* Try and load any missing data from the server.  The
 201                          * unmarshalling routine will take care of clearing any
 202                          * bits that are beyond the EOF.
 203                          */
 204                         ret = afs_fill_page(vnode, key, pos + copied,
 205                                             len - copied, page);
 206                         if (ret < 0)
 207                                 goto out;
 208                 }
 209                 SetPageUptodate(page);
 210         }
 211
 212         set_page_dirty(page);
 213         if (PageDirty(page))
 214                 _debug("dirtied");
 215         ret = copied;
 216
 217 out:
 218         unlock_page(page);
 219         put_page(page);
 220         return ret;
 221 }
 222
 223 /*
 224  * kill all the pages in the given range
 225  */
 226 static void afs_kill_pages(struct address_space *mapping,
 227                            pgoff_t first, pgoff_t last)
 228 {
 229         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 230         struct pagevec pv;
 231         unsigned count, loop;
 232
 233         _enter("{%x:%u},%lx-%lx",
 234                vnode->fid.vid, vnode->fid.vnode, first, last);
 235
 236         pagevec_init(&pv);
 237
 238         do {
 239                 _debug("kill %lx-%lx", first, last);
 240
 241                 count = last - first + 1;
 242                 if (count > PAGEVEC_SIZE)
 243                         count = PAGEVEC_SIZE;
 244                 pv.nr = find_get_pages_contig(mapping, first, count, pv.pages);
 245                 ASSERTCMP(pv.nr, ==, count);
 246
 247                 for (loop = 0; loop < count; loop++) {
 248                         struct page *page = pv.pages[loop];
 249                         ClearPageUptodate(page);
 250                         SetPageError(page);
 251                         end_page_writeback(page);
 252                         if (page->index >= first)
 253                                 first = page->index + 1;
 254                         lock_page(page);
 255                         generic_error_remove_page(mapping, page);
 256                 }
 257
 258                 __pagevec_release(&pv);
 259         } while (first <= last);
 260
 261         _leave("");
 262 }
 263
 264 /*
 265  * Redirty all the pages in a given range.
 266  */
 267 static void afs_redirty_pages(struct writeback_control *wbc,
 268                               struct address_space *mapping,
 269                               pgoff_t first, pgoff_t last)
 270 {
 271         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 272         struct pagevec pv;
 273         unsigned count, loop;
 274
 275         _enter("{%x:%u},%lx-%lx",
 276                vnode->fid.vid, vnode->fid.vnode, first, last);
 277
 278         pagevec_init(&pv);
 279
 280         do {
 281                 _debug("redirty %lx-%lx", first, last);
 282
 283                 count = last - first + 1;
 284                 if (count > PAGEVEC_SIZE)
 285                         count = PAGEVEC_SIZE;
 286                 pv.nr = find_get_pages_contig(mapping, first, count, pv.pages);
 287                 ASSERTCMP(pv.nr, ==, count);
 288
 289                 for (loop = 0; loop < count; loop++) {
 290                         struct page *page = pv.pages[loop];
 291
 292                         redirty_page_for_writepage(wbc, page);
 293                         end_page_writeback(page);
 294                         if (page->index >= first)
 295                                 first = page->index + 1;
 296                 }
 297
 298                 __pagevec_release(&pv);
 299         } while (first <= last);
 300
 301         _leave("");
 302 }
 303
 304 /*
 305  * write to a file
 306  */
 307 static int afs_store_data(struct address_space *mapping,
 308                           pgoff_t first, pgoff_t last,
 309                           unsigned offset, unsigned to)
 310 {
 311         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 312         struct afs_fs_cursor fc;
 313         struct afs_wb_key *wbk = NULL;
 314         struct list_head *p;
 315         int ret = -ENOKEY, ret2;
 316
 317         _enter("%s{%x:%u.%u},%lx,%lx,%x,%x",
 318                vnode->volume->name,
 319                vnode->fid.vid,
 320                vnode->fid.vnode,
 321                vnode->fid.unique,
 322                first, last, offset, to);
 323
 324         spin_lock(&vnode->wb_lock);
 325         p = vnode->wb_keys.next;
 326
 327         /* Iterate through the list looking for a valid key to use. */
 328 try_next_key:
 329         while (p != &vnode->wb_keys) {
 330                 wbk = list_entry(p, struct afs_wb_key, vnode_link);
 331                 _debug("wbk %u", key_serial(wbk->key));
 332                 ret2 = key_validate(wbk->key);
 333                 if (ret2 == 0)
 334                         goto found_key;
 335                 if (ret == -ENOKEY)
 336                         ret = ret2;
 337                 p = p->next;
 338         }
 339
 340         spin_unlock(&vnode->wb_lock);
 341         afs_put_wb_key(wbk);
 342         _leave(" = %d [no keys]", ret);
 343         return ret;
 344
 345 found_key:
 346         refcount_inc(&wbk->usage);
 347         spin_unlock(&vnode->wb_lock);
 348
 349         _debug("USE WB KEY %u", key_serial(wbk->key));
 350
 351         ret = -ERESTARTSYS;
 352         if (afs_begin_vnode_operation(&fc, vnode, wbk->key)) {
 353                 while (afs_select_fileserver(&fc)) {
 354                         fc.cb_break = vnode->cb_break + vnode->cb_s_break;
 355                         afs_fs_store_data(&fc, mapping, first, last, offset, to);
 356                 }
 357
 358                 afs_check_for_remote_deletion(&fc, fc.vnode);
 359                 afs_vnode_commit_status(&fc, vnode, fc.cb_break);
 360                 ret = afs_end_vnode_operation(&fc);
 361         }
 362
 363         switch (ret) {
 364         case 0:
 365                 afs_stat_v(vnode, n_stores);
 366                 atomic_long_add((last * PAGE_SIZE + to) -
 367                                 (first * PAGE_SIZE + offset),
 368                                 &afs_v2net(vnode)->n_store_bytes);
 369                 break;
 370         case -EACCES:
 371         case -EPERM:
 372         case -ENOKEY:
 373         case -EKEYEXPIRED:
 374         case -EKEYREJECTED:
 375         case -EKEYREVOKED:
 376                 _debug("next");
 377                 spin_lock(&vnode->wb_lock);
 378                 p = wbk->vnode_link.next;
 379                 afs_put_wb_key(wbk);
 380                 goto try_next_key;
 381         }
 382
 383         afs_put_wb_key(wbk);
 384         _leave(" = %d", ret);
 385         return ret;
 386 }
 387
 388 /*
 389  * Synchronously write back the locked page and any subsequent non-locked dirty
 390  * pages.
 391  */
 392 static int afs_write_back_from_locked_page(struct address_space *mapping,
 393                                            struct writeback_control *wbc,
 394                                            struct page *primary_page,
 395                                            pgoff_t final_page)
 396 {
 397         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 398         struct page *pages[8], *page;
 399         unsigned long count, priv;
 400         unsigned n, offset, to, f, t;
 401         pgoff_t start, first, last;
 402         int loop, ret;
 403
 404         _enter(",%lx", primary_page->index);
 405
 406         count = 1;
 407         if (test_set_page_writeback(primary_page))
 408                 BUG();
 409
 410         /* Find all consecutive lockable dirty pages that have contiguous
 411          * written regions, stopping when we find a page that is not
 412          * immediately lockable, is not dirty or is missing, or we reach the
 413          * end of the range.
 414          */
 415         start = primary_page->index;
 416         priv = page_private(primary_page);
 417         offset = priv & AFS_PRIV_MAX;
 418         to = priv >> AFS_PRIV_SHIFT;
 419         trace_afs_page_dirty(vnode, tracepoint_string("store"),
 420                              primary_page->index, priv);
 421
 422         WARN_ON(offset == to);
 423         if (offset == to)
 424                 trace_afs_page_dirty(vnode, tracepoint_string("WARN"),
 425                                      primary_page->index, priv);
 426
 427         if (start >= final_page ||
 428             (to < PAGE_SIZE && !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)))
 429                 goto no_more;
 430
 431         start++;
 432         do {
 433                 _debug("more %lx [%lx]", start, count);
 434                 n = final_page - start + 1;
 435                 if (n > ARRAY_SIZE(pages))
 436                         n = ARRAY_SIZE(pages);
 437                 n = find_get_pages_contig(mapping, start, ARRAY_SIZE(pages), pages);
 438                 _debug("fgpc %u", n);
 439                 if (n == 0)
 440                         goto no_more;
 441                 if (pages[0]->index != start) {
 442                         do {
 443                                 put_page(pages[--n]);
 444                         } while (n > 0);
 445                         goto no_more;
 446                 }
 447
 448                 for (loop = 0; loop < n; loop++) {
 449                         page = pages[loop];
 450                         if (to != PAGE_SIZE &&
 451                             !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags))
 452                                 break;
 453                         if (page->index > final_page)
 454                                 break;
 455                         if (!trylock_page(page))
 456                                 break;
 457                         if (!PageDirty(page) || PageWriteback(page)) {
 458                                 unlock_page(page);
 459                                 break;
 460                         }
 461
 462                         priv = page_private(page);
 463                         f = priv & AFS_PRIV_MAX;
 464                         t = priv >> AFS_PRIV_SHIFT;
 465                         if (f != 0 &&
 466                             !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)) {
 467                                 unlock_page(page);
 468                                 break;
 469                         }
 470                         to = t;
 471
 472                         trace_afs_page_dirty(vnode, tracepoint_string("store+"),
 473                                              page->index, priv);
 474
 475                         if (!clear_page_dirty_for_io(page))
 476                                 BUG();
 477                         if (test_set_page_writeback(page))
 478                                 BUG();
 479                         unlock_page(page);
 480                         put_page(page);
 481                 }
 482                 count += loop;
 483                 if (loop < n) {
 484                         for (; loop < n; loop++)
 485                                 put_page(pages[loop]);
 486                         goto no_more;
 487                 }
 488
 489                 start += loop;
 490         } while (start <= final_page && count < 65536);
 491
 492 no_more:
 493         /* We now have a contiguous set of dirty pages, each with writeback
 494          * set; the first page is still locked at this point, but all the rest
 495          * have been unlocked.
 496          */
 497         unlock_page(primary_page);
 498
 499         first = primary_page->index;
 500         last = first + count - 1;
 501
 502         _debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to);
 503
 504         ret = afs_store_data(mapping, first, last, offset, to);
 505         switch (ret) {
 506         case 0:
 507                 ret = count;
 508                 break;
 509
 510         default:
 511                 pr_notice("kAFS: Unexpected error from FS.StoreData %d\n", ret);
 512                 /* Fall through */
 513         case -EACCES:
 514         case -EPERM:
 515         case -ENOKEY:
 516         case -EKEYEXPIRED:
 517         case -EKEYREJECTED:
 518         case -EKEYREVOKED:
 519                 afs_redirty_pages(wbc, mapping, first, last);
 520                 mapping_set_error(mapping, ret);
 521                 break;
 522
 523         case -EDQUOT:
 524         case -ENOSPC:
 525                 afs_redirty_pages(wbc, mapping, first, last);
 526                 mapping_set_error(mapping, -ENOSPC);
 527                 break;
 528
 529         case -EROFS:
 530         case -EIO:
 531         case -EREMOTEIO:
 532         case -EFBIG:
 533         case -ENOENT:
 534         case -ENOMEDIUM:
 535         case -ENXIO:
 536                 afs_kill_pages(mapping, first, last);
 537                 mapping_set_error(mapping, ret);
 538                 break;
 539         }
 540
 541         _leave(" = %d", ret);
 542         return ret;
 543 }
 544
 545 /*
 546  * write a page back to the server
 547  * - the caller locked the page for us
 548  */
 549 int afs_writepage(struct page *page, struct writeback_control *wbc)
 550 {
 551         int ret;
 552
 553         _enter("{%lx},", page->index);
 554
 555         ret = afs_write_back_from_locked_page(page->mapping, wbc, page,
 556                                               wbc->range_end >> PAGE_SHIFT);
 557         if (ret < 0) {
 558                 _leave(" = %d", ret);
 559                 return 0;
 560         }
 561
 562         wbc->nr_to_write -= ret;
 563
 564         _leave(" = 0");
 565         return 0;
 566 }
 567
 568 /*
 569  * write a region of pages back to the server
 570  */
 571 static int afs_writepages_region(struct address_space *mapping,
 572                                  struct writeback_control *wbc,
 573                                  pgoff_t index, pgoff_t end, pgoff_t *_next)
 574 {
 575         struct page *page;
 576         int ret, n;
 577
 578         _enter(",,%lx,%lx,", index, end);
 579
 580         do {
 581                 n = find_get_pages_range_tag(mapping, &index, end,
 582                                         PAGECACHE_TAG_DIRTY, 1, &page);
 583                 if (!n)
 584                         break;
 585
 586                 _debug("wback %lx", page->index);
 587
 588                 /*
 589                  * at this point we hold neither the i_pages lock nor the
 590                  * page lock: the page may be truncated or invalidated
 591                  * (changing page->mapping to NULL), or even swizzled
 592                  * back from swapper_space to tmpfs file mapping
 593                  */
 594                 ret = lock_page_killable(page);
 595                 if (ret < 0) {
 596                         put_page(page);
 597                         _leave(" = %d", ret);
 598                         return ret;
 599                 }
 600
 601                 if (page->mapping != mapping || !PageDirty(page)) {
 602                         unlock_page(page);
 603                         put_page(page);
 604                         continue;
 605                 }
 606
 607                 if (PageWriteback(page)) {
 608                         unlock_page(page);
 609                         if (wbc->sync_mode != WB_SYNC_NONE)
 610                                 wait_on_page_writeback(page);
 611                         put_page(page);
 612                         continue;
 613                 }
 614
 615                 if (!clear_page_dirty_for_io(page))
 616                         BUG();
 617                 ret = afs_write_back_from_locked_page(mapping, wbc, page, end);
 618                 put_page(page);
 619                 if (ret < 0) {
 620                         _leave(" = %d", ret);
 621                         return ret;
 622                 }
 623
 624                 wbc->nr_to_write -= ret;
 625
 626                 cond_resched();
 627         } while (index < end && wbc->nr_to_write > 0);
 628
 629         *_next = index;
 630         _leave(" = 0 [%lx]", *_next);
 631         return 0;
 632 }
 633
 634 /*
 635  * write some of the pending data back to the server
 636  */
 637 int afs_writepages(struct address_space *mapping,
 638                    struct writeback_control *wbc)
 639 {
 640         pgoff_t start, end, next;
 641         int ret;
 642
 643         _enter("");
 644
 645         if (wbc->range_cyclic) {
 646                 start = mapping->writeback_index;
 647                 end = -1;
 648                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
 649                 if (start > 0 && wbc->nr_to_write > 0 && ret == 0)
 650                         ret = afs_writepages_region(mapping, wbc, 0, start,
 651                                                     &next);
 652                 mapping->writeback_index = next;
 653         } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
 654                 end = (pgoff_t)(LLONG_MAX >> PAGE_SHIFT);
 655                 ret = afs_writepages_region(mapping, wbc, 0, end, &next);
 656                 if (wbc->nr_to_write > 0)
 657                         mapping->writeback_index = next;
 658         } else {
 659                 start = wbc->range_start >> PAGE_SHIFT;
 660                 end = wbc->range_end >> PAGE_SHIFT;
 661                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
 662         }
 663
 664         _leave(" = %d", ret);
 665         return ret;
 666 }
 667
 668 /*
 669  * completion of write to server
 670  */
 671 void afs_pages_written_back(struct afs_vnode *vnode, struct afs_call *call)
 672 {
 673         struct pagevec pv;
 674         unsigned long priv;
 675         unsigned count, loop;
 676         pgoff_t first = call->first, last = call->last;
 677
 678         _enter("{%x:%u},{%lx-%lx}",
 679                vnode->fid.vid, vnode->fid.vnode, first, last);
 680
 681         pagevec_init(&pv);
 682
 683         do {
 684                 _debug("done %lx-%lx", first, last);
 685
 686                 count = last - first + 1;
 687                 if (count > PAGEVEC_SIZE)
 688                         count = PAGEVEC_SIZE;
 689                 pv.nr = find_get_pages_contig(vnode->vfs_inode.i_mapping,
 690                                               first, count, pv.pages);
 691                 ASSERTCMP(pv.nr, ==, count);
 692
 693                 for (loop = 0; loop < count; loop++) {
 694                         priv = page_private(pv.pages[loop]);
 695                         trace_afs_page_dirty(vnode, tracepoint_string("clear"),
 696                                              pv.pages[loop]->index, priv);
 697                         set_page_private(pv.pages[loop], 0);
 698                         end_page_writeback(pv.pages[loop]);
 699                 }
 700                 first += count;
 701                 __pagevec_release(&pv);
 702         } while (first <= last);
 703
 704         afs_prune_wb_keys(vnode);
 705         _leave("");
 706 }
 707
 708 /*
 709  * write to an AFS file
 710  */
 711 ssize_t afs_file_write(struct kiocb *iocb, struct iov_iter *from)
 712 {
 713         struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp));
 714         ssize_t result;
 715         size_t count = iov_iter_count(from);
 716
 717         _enter("{%x.%u},{%zu},",
 718                vnode->fid.vid, vnode->fid.vnode, count);
 719
 720         if (IS_SWAPFILE(&vnode->vfs_inode)) {
 721                 printk(KERN_INFO
 722                        "AFS: Attempt to write to active swap file!\n");
 723                 return -EBUSY;
 724         }
 725
 726         if (!count)
 727                 return 0;
 728
 729         result = generic_file_write_iter(iocb, from);
 730
 731         _leave(" = %zd", result);
 732         return result;
 733 }
 734
 735 /*
 736  * flush any dirty pages for this process, and check for write errors.
 737  * - the return status from this call provides a reliable indication of
 738  *   whether any write errors occurred for this process.
 739  */
 740 int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 741 {
 742         struct inode *inode = file_inode(file);
 743         struct afs_vnode *vnode = AFS_FS_I(inode);
 744
 745         _enter("{%x:%u},{n=%pD},%d",
 746                vnode->fid.vid, vnode->fid.vnode, file,
 747                datasync);
 748
 749         return file_write_and_wait_range(file, start, end);
 750 }
 751
 752 /*
 753  * notification that a previously read-only page is about to become writable
 754  * - if it returns an error, the caller will deliver a bus error signal
 755  */
 756 int afs_page_mkwrite(struct vm_fault *vmf)
 757 {
 758         struct file *file = vmf->vma->vm_file;
 759         struct inode *inode = file_inode(file);
 760         struct afs_vnode *vnode = AFS_FS_I(inode);
 761         unsigned long priv;
 762
 763         _enter("{{%x:%u}},{%lx}",
 764                vnode->fid.vid, vnode->fid.vnode, vmf->page->index);
 765
 766         sb_start_pagefault(inode->i_sb);
 767
 768         /* Wait for the page to be written to the cache before we allow it to
 769          * be modified.  We then assume the entire page will need writing back.
 770          */
 771 #ifdef CONFIG_AFS_FSCACHE
 772         fscache_wait_on_page_write(vnode->cache, vmf->page);
 773 #endif
 774
 775         if (PageWriteback(vmf->page) &&
 776             wait_on_page_bit_killable(vmf->page, PG_writeback) < 0)
 777                 return VM_FAULT_RETRY;
 778
 779         if (lock_page_killable(vmf->page) < 0)
 780                 return VM_FAULT_RETRY;
 781
 782         /* We mustn't change page->private until writeback is complete as that
 783          * details the portion of the page we need to write back and we might
 784          * need to redirty the page if there's a problem.
 785          */
 786         wait_on_page_writeback(vmf->page);
 787
 788         priv = (unsigned long)PAGE_SIZE << AFS_PRIV_SHIFT; /* To */
 789         priv |= 0; /* From */
 790         trace_afs_page_dirty(vnode, tracepoint_string("mkwrite"),
 791                              vmf->page->index, priv);
 792         SetPagePrivate(vmf->page);
 793         set_page_private(vmf->page, priv);
 794
 795         sb_end_pagefault(inode->i_sb);
 796         return VM_FAULT_LOCKED;
 797 }
 798
 799 /*
 800  * Prune the keys cached for writeback.  The caller must hold vnode->wb_lock.
 801  */
 802 void afs_prune_wb_keys(struct afs_vnode *vnode)
 803 {
 804         LIST_HEAD(graveyard);
 805         struct afs_wb_key *wbk, *tmp;
 806
 807         /* Discard unused keys */
 808         spin_lock(&vnode->wb_lock);
 809
 810         if (!mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_WRITEBACK) &&
 811             !mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_DIRTY)) {
 812                 list_for_each_entry_safe(wbk, tmp, &vnode->wb_keys, vnode_link) {
 813                         if (refcount_read(&wbk->usage) == 1)
 814                                 list_move(&wbk->vnode_link, &graveyard);
 815                 }
 816         }
 817
 818         spin_unlock(&vnode->wb_lock);
 819
 820         while (!list_empty(&graveyard)) {
 821                 wbk = list_entry(graveyard.next, struct afs_wb_key, vnode_link);
 822                 list_del(&wbk->vnode_link);
 823                 afs_put_wb_key(wbk);
 824         }
 825 }
 826
 827 /*
 828  * Clean up a page during invalidation.
 829  */
 830 int afs_launder_page(struct page *page)
 831 {
 832         struct address_space *mapping = page->mapping;
 833         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 834         unsigned long priv;
 835         unsigned int f, t;
 836         int ret = 0;
 837
 838         _enter("{%lx}", page->index);
 839
 840         priv = page_private(page);
 841         if (clear_page_dirty_for_io(page)) {
 842                 f = 0;
 843                 t = PAGE_SIZE;
 844                 if (PagePrivate(page)) {
 845                         f = priv & AFS_PRIV_MAX;
 846                         t = priv >> AFS_PRIV_SHIFT;
 847                 }
 848
 849                 trace_afs_page_dirty(vnode, tracepoint_string("launder"),
 850                                      page->index, priv);
 851                 ret = afs_store_data(mapping, page->index, page->index, t, f);
 852         }
 853
 854         trace_afs_page_dirty(vnode, tracepoint_string("laundered"),
 855                              page->index, priv);
 856         set_page_private(page, 0);
 857         ClearPagePrivate(page);
 858
 859 #ifdef CONFIG_AFS_FSCACHE
 860         if (PageFsCache(page)) {
 861                 fscache_wait_on_page_write(vnode->cache, page);
 862                 fscache_uncache_page(vnode->cache, page);
 863         }
 864 #endif
 865         return ret;
 866 }