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