fs/afs/write.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* handling of writes to regular files and writing back to the server
   3  *
   4  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/backing-dev.h>
   9 #include <linux/slab.h>
  10 #include <linux/fs.h>
  11 #include <linux/pagemap.h>
  12 #include <linux/writeback.h>
  13 #include <linux/pagevec.h>
  14 #include <linux/netfs.h>
  15 #include <linux/fscache.h>
  16 #include "internal.h"
  17
  18 /*
  19  * mark a page as having been made dirty and thus needing writeback
  20  */
  21 int afs_set_page_dirty(struct page *page)
  22 {
  23         _enter("");
  24         return __set_page_dirty_nobuffers(page);
  25 }
  26
  27 /*
  28  * prepare to perform part of a write to a page
  29  */
  30 int afs_write_begin(struct file *file, struct address_space *mapping,
  31                     loff_t pos, unsigned len, unsigned flags,
  32                     struct page **_page, void **fsdata)
  33 {
  34         struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
  35         struct page *page;
  36         unsigned long priv;
  37         unsigned f, from;
  38         unsigned t, to;
  39         pgoff_t index;
  40         int ret;
  41
  42         _enter("{%llx:%llu},%llx,%x",
  43                vnode->fid.vid, vnode->fid.vnode, pos, len);
  44
  45         /* Prefetch area to be written into the cache if we're caching this
  46          * file.  We need to do this before we get a lock on the page in case
  47          * there's more than one writer competing for the same cache block.
  48          */
  49         ret = netfs_write_begin(file, mapping, pos, len, flags, &page, fsdata,
  50                                 &afs_req_ops, NULL);
  51         if (ret < 0)
  52                 return ret;
  53
  54         index = page->index;
  55         from = pos - index * PAGE_SIZE;
  56         to = from + len;
  57
  58 try_again:
  59         /* See if this page is already partially written in a way that we can
  60          * merge the new write with.
  61          */
  62         if (PagePrivate(page)) {
  63                 priv = page_private(page);
  64                 f = afs_page_dirty_from(page, priv);
  65                 t = afs_page_dirty_to(page, priv);
  66                 ASSERTCMP(f, <=, t);
  67
  68                 if (PageWriteback(page)) {
  69                         trace_afs_page_dirty(vnode, tracepoint_string("alrdy"), page);
  70                         goto flush_conflicting_write;
  71                 }
  72                 /* If the file is being filled locally, allow inter-write
  73                  * spaces to be merged into writes.  If it's not, only write
  74                  * back what the user gives us.
  75                  */
  76                 if (!test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags) &&
  77                     (to < f || from > t))
  78                         goto flush_conflicting_write;
  79         }
  80
  81         *_page = page;
  82         _leave(" = 0");
  83         return 0;
  84
  85         /* The previous write and this write aren't adjacent or overlapping, so
  86          * flush the page out.
  87          */
  88 flush_conflicting_write:
  89         _debug("flush conflict");
  90         ret = write_one_page(page);
  91         if (ret < 0)
  92                 goto error;
  93
  94         ret = lock_page_killable(page);
  95         if (ret < 0)
  96                 goto error;
  97         goto try_again;
  98
  99 error:
 100         put_page(page);
 101         _leave(" = %d", ret);
 102         return ret;
 103 }
 104
 105 /*
 106  * finalise part of a write to a page
 107  */
 108 int afs_write_end(struct file *file, struct address_space *mapping,
 109                   loff_t pos, unsigned len, unsigned copied,
 110                   struct page *page, void *fsdata)
 111 {
 112         struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
 113         unsigned long priv;
 114         unsigned int f, from = pos & (thp_size(page) - 1);
 115         unsigned int t, to = from + copied;
 116         loff_t i_size, maybe_i_size;
 117
 118         _enter("{%llx:%llu},{%lx}",
 119                vnode->fid.vid, vnode->fid.vnode, page->index);
 120
 121         if (!PageUptodate(page)) {
 122                 if (copied < len) {
 123                         copied = 0;
 124                         goto out;
 125                 }
 126
 127                 SetPageUptodate(page);
 128         }
 129
 130         if (copied == 0)
 131                 goto out;
 132
 133         maybe_i_size = pos + copied;
 134
 135         i_size = i_size_read(&vnode->vfs_inode);
 136         if (maybe_i_size > i_size) {
 137                 write_seqlock(&vnode->cb_lock);
 138                 i_size = i_size_read(&vnode->vfs_inode);
 139                 if (maybe_i_size > i_size)
 140                         i_size_write(&vnode->vfs_inode, maybe_i_size);
 141                 write_sequnlock(&vnode->cb_lock);
 142         }
 143
 144         if (PagePrivate(page)) {
 145                 priv = page_private(page);
 146                 f = afs_page_dirty_from(page, priv);
 147                 t = afs_page_dirty_to(page, priv);
 148                 if (from < f)
 149                         f = from;
 150                 if (to > t)
 151                         t = to;
 152                 priv = afs_page_dirty(page, f, t);
 153                 set_page_private(page, priv);
 154                 trace_afs_page_dirty(vnode, tracepoint_string("dirty+"), page);
 155         } else {
 156                 priv = afs_page_dirty(page, from, to);
 157                 attach_page_private(page, (void *)priv);
 158                 trace_afs_page_dirty(vnode, tracepoint_string("dirty"), page);
 159         }
 160
 161         if (set_page_dirty(page))
 162                 _debug("dirtied %lx", page->index);
 163
 164 out:
 165         unlock_page(page);
 166         put_page(page);
 167         return copied;
 168 }
 169
 170 /*
 171  * kill all the pages in the given range
 172  */
 173 static void afs_kill_pages(struct address_space *mapping,
 174                            loff_t start, loff_t len)
 175 {
 176         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 177         struct pagevec pv;
 178         unsigned int loop, psize;
 179
 180         _enter("{%llx:%llu},%llx @%llx",
 181                vnode->fid.vid, vnode->fid.vnode, len, start);
 182
 183         pagevec_init(&pv);
 184
 185         do {
 186                 _debug("kill %llx @%llx", len, start);
 187
 188                 pv.nr = find_get_pages_contig(mapping, start / PAGE_SIZE,
 189                                               PAGEVEC_SIZE, pv.pages);
 190                 if (pv.nr == 0)
 191                         break;
 192
 193                 for (loop = 0; loop < pv.nr; loop++) {
 194                         struct page *page = pv.pages[loop];
 195
 196                         if (page->index * PAGE_SIZE >= start + len)
 197                                 break;
 198
 199                         psize = thp_size(page);
 200                         start += psize;
 201                         len -= psize;
 202                         ClearPageUptodate(page);
 203                         end_page_writeback(page);
 204                         lock_page(page);
 205                         generic_error_remove_page(mapping, page);
 206                         unlock_page(page);
 207                 }
 208
 209                 __pagevec_release(&pv);
 210         } while (len > 0);
 211
 212         _leave("");
 213 }
 214
 215 /*
 216  * Redirty all the pages in a given range.
 217  */
 218 static void afs_redirty_pages(struct writeback_control *wbc,
 219                               struct address_space *mapping,
 220                               loff_t start, loff_t len)
 221 {
 222         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 223         struct pagevec pv;
 224         unsigned int loop, psize;
 225
 226         _enter("{%llx:%llu},%llx @%llx",
 227                vnode->fid.vid, vnode->fid.vnode, len, start);
 228
 229         pagevec_init(&pv);
 230
 231         do {
 232                 _debug("redirty %llx @%llx", len, start);
 233
 234                 pv.nr = find_get_pages_contig(mapping, start / PAGE_SIZE,
 235                                               PAGEVEC_SIZE, pv.pages);
 236                 if (pv.nr == 0)
 237                         break;
 238
 239                 for (loop = 0; loop < pv.nr; loop++) {
 240                         struct page *page = pv.pages[loop];
 241
 242                         if (page->index * PAGE_SIZE >= start + len)
 243                                 break;
 244
 245                         psize = thp_size(page);
 246                         start += psize;
 247                         len -= psize;
 248                         redirty_page_for_writepage(wbc, page);
 249                         end_page_writeback(page);
 250                 }
 251
 252                 __pagevec_release(&pv);
 253         } while (len > 0);
 254
 255         _leave("");
 256 }
 257
 258 /*
 259  * completion of write to server
 260  */
 261 static void afs_pages_written_back(struct afs_vnode *vnode, loff_t start, unsigned int len)
 262 {
 263         struct address_space *mapping = vnode->vfs_inode.i_mapping;
 264         struct page *page;
 265         pgoff_t end;
 266
 267         XA_STATE(xas, &mapping->i_pages, start / PAGE_SIZE);
 268
 269         _enter("{%llx:%llu},{%x @%llx}",
 270                vnode->fid.vid, vnode->fid.vnode, len, start);
 271
 272         rcu_read_lock();
 273
 274         end = (start + len - 1) / PAGE_SIZE;
 275         xas_for_each(&xas, page, end) {
 276                 if (!PageWriteback(page)) {
 277                         kdebug("bad %x @%llx page %lx %lx", len, start, page->index, end);
 278                         ASSERT(PageWriteback(page));
 279                 }
 280
 281                 trace_afs_page_dirty(vnode, tracepoint_string("clear"), page);
 282                 detach_page_private(page);
 283                 page_endio(page, true, 0);
 284         }
 285
 286         rcu_read_unlock();
 287
 288         afs_prune_wb_keys(vnode);
 289         _leave("");
 290 }
 291
 292 /*
 293  * Find a key to use for the writeback.  We cached the keys used to author the
 294  * writes on the vnode.  *_wbk will contain the last writeback key used or NULL
 295  * and we need to start from there if it's set.
 296  */
 297 static int afs_get_writeback_key(struct afs_vnode *vnode,
 298                                  struct afs_wb_key **_wbk)
 299 {
 300         struct afs_wb_key *wbk = NULL;
 301         struct list_head *p;
 302         int ret = -ENOKEY, ret2;
 303
 304         spin_lock(&vnode->wb_lock);
 305         if (*_wbk)
 306                 p = (*_wbk)->vnode_link.next;
 307         else
 308                 p = vnode->wb_keys.next;
 309
 310         while (p != &vnode->wb_keys) {
 311                 wbk = list_entry(p, struct afs_wb_key, vnode_link);
 312                 _debug("wbk %u", key_serial(wbk->key));
 313                 ret2 = key_validate(wbk->key);
 314                 if (ret2 == 0) {
 315                         refcount_inc(&wbk->usage);
 316                         _debug("USE WB KEY %u", key_serial(wbk->key));
 317                         break;
 318                 }
 319
 320                 wbk = NULL;
 321                 if (ret == -ENOKEY)
 322                         ret = ret2;
 323                 p = p->next;
 324         }
 325
 326         spin_unlock(&vnode->wb_lock);
 327         if (*_wbk)
 328                 afs_put_wb_key(*_wbk);
 329         *_wbk = wbk;
 330         return 0;
 331 }
 332
 333 static void afs_store_data_success(struct afs_operation *op)
 334 {
 335         struct afs_vnode *vnode = op->file[0].vnode;
 336
 337         op->ctime = op->file[0].scb.status.mtime_client;
 338         afs_vnode_commit_status(op, &op->file[0]);
 339         if (op->error == 0) {
 340                 if (!op->store.laundering)
 341                         afs_pages_written_back(vnode, op->store.pos, op->store.size);
 342                 afs_stat_v(vnode, n_stores);
 343                 atomic_long_add(op->store.size, &afs_v2net(vnode)->n_store_bytes);
 344         }
 345 }
 346
 347 static const struct afs_operation_ops afs_store_data_operation = {
 348         .issue_afs_rpc  = afs_fs_store_data,
 349         .issue_yfs_rpc  = yfs_fs_store_data,
 350         .success        = afs_store_data_success,
 351 };
 352
 353 /*
 354  * write to a file
 355  */
 356 static int afs_store_data(struct afs_vnode *vnode, struct iov_iter *iter, loff_t pos,
 357                           bool laundering)
 358 {
 359         struct afs_operation *op;
 360         struct afs_wb_key *wbk = NULL;
 361         loff_t size = iov_iter_count(iter), i_size;
 362         int ret = -ENOKEY;
 363
 364         _enter("%s{%llx:%llu.%u},%llx,%llx",
 365                vnode->volume->name,
 366                vnode->fid.vid,
 367                vnode->fid.vnode,
 368                vnode->fid.unique,
 369                size, pos);
 370
 371         ret = afs_get_writeback_key(vnode, &wbk);
 372         if (ret) {
 373                 _leave(" = %d [no keys]", ret);
 374                 return ret;
 375         }
 376
 377         op = afs_alloc_operation(wbk->key, vnode->volume);
 378         if (IS_ERR(op)) {
 379                 afs_put_wb_key(wbk);
 380                 return -ENOMEM;
 381         }
 382
 383         i_size = i_size_read(&vnode->vfs_inode);
 384
 385         afs_op_set_vnode(op, 0, vnode);
 386         op->file[0].dv_delta = 1;
 387         op->file[0].modification = true;
 388         op->store.write_iter = iter;
 389         op->store.pos = pos;
 390         op->store.size = size;
 391         op->store.i_size = max(pos + size, i_size);
 392         op->store.laundering = laundering;
 393         op->mtime = vnode->vfs_inode.i_mtime;
 394         op->flags |= AFS_OPERATION_UNINTR;
 395         op->ops = &afs_store_data_operation;
 396
 397 try_next_key:
 398         afs_begin_vnode_operation(op);
 399         afs_wait_for_operation(op);
 400
 401         switch (op->error) {
 402         case -EACCES:
 403         case -EPERM:
 404         case -ENOKEY:
 405         case -EKEYEXPIRED:
 406         case -EKEYREJECTED:
 407         case -EKEYREVOKED:
 408                 _debug("next");
 409
 410                 ret = afs_get_writeback_key(vnode, &wbk);
 411                 if (ret == 0) {
 412                         key_put(op->key);
 413                         op->key = key_get(wbk->key);
 414                         goto try_next_key;
 415                 }
 416                 break;
 417         }
 418
 419         afs_put_wb_key(wbk);
 420         _leave(" = %d", op->error);
 421         return afs_put_operation(op);
 422 }
 423
 424 /*
 425  * Extend the region to be written back to include subsequent contiguously
 426  * dirty pages if possible, but don't sleep while doing so.
 427  *
 428  * If this page holds new content, then we can include filler zeros in the
 429  * writeback.
 430  */
 431 static void afs_extend_writeback(struct address_space *mapping,
 432                                  struct afs_vnode *vnode,
 433                                  long *_count,
 434                                  loff_t start,
 435                                  loff_t max_len,
 436                                  bool new_content,
 437                                  unsigned int *_len)
 438 {
 439         struct pagevec pvec;
 440         struct page *page;
 441         unsigned long priv;
 442         unsigned int psize, filler = 0;
 443         unsigned int f, t;
 444         loff_t len = *_len;
 445         pgoff_t index = (start + len) / PAGE_SIZE;
 446         bool stop = true;
 447         unsigned int i;
 448
 449         XA_STATE(xas, &mapping->i_pages, index);
 450         pagevec_init(&pvec);
 451
 452         do {
 453                 /* Firstly, we gather up a batch of contiguous dirty pages
 454                  * under the RCU read lock - but we can't clear the dirty flags
 455                  * there if any of those pages are mapped.
 456                  */
 457                 rcu_read_lock();
 458
 459                 xas_for_each(&xas, page, ULONG_MAX) {
 460                         stop = true;
 461                         if (xas_retry(&xas, page))
 462                                 continue;
 463                         if (xa_is_value(page))
 464                                 break;
 465                         if (page->index != index)
 466                                 break;
 467
 468                         if (!page_cache_get_speculative(page)) {
 469                                 xas_reset(&xas);
 470                                 continue;
 471                         }
 472
 473                         /* Has the page moved or been split? */
 474                         if (unlikely(page != xas_reload(&xas)))
 475                                 break;
 476
 477                         if (!trylock_page(page))
 478                                 break;
 479                         if (!PageDirty(page) || PageWriteback(page)) {
 480                                 unlock_page(page);
 481                                 break;
 482                         }
 483
 484                         psize = thp_size(page);
 485                         priv = page_private(page);
 486                         f = afs_page_dirty_from(page, priv);
 487                         t = afs_page_dirty_to(page, priv);
 488                         if (f != 0 && !new_content) {
 489                                 unlock_page(page);
 490                                 break;
 491                         }
 492
 493                         len += filler + t;
 494                         filler = psize - t;
 495                         if (len >= max_len || *_count <= 0)
 496                                 stop = true;
 497                         else if (t == psize || new_content)
 498                                 stop = false;
 499
 500                         index += thp_nr_pages(page);
 501                         if (!pagevec_add(&pvec, page))
 502                                 break;
 503                         if (stop)
 504                                 break;
 505                 }
 506
 507                 if (!stop)
 508                         xas_pause(&xas);
 509                 rcu_read_unlock();
 510
 511                 /* Now, if we obtained any pages, we can shift them to being
 512                  * writable and mark them for caching.
 513                  */
 514                 if (!pagevec_count(&pvec))
 515                         break;
 516
 517                 for (i = 0; i < pagevec_count(&pvec); i++) {
 518                         page = pvec.pages[i];
 519                         trace_afs_page_dirty(vnode, tracepoint_string("store+"), page);
 520
 521                         if (!clear_page_dirty_for_io(page))
 522                                 BUG();
 523                         if (test_set_page_writeback(page))
 524                                 BUG();
 525
 526                         *_count -= thp_nr_pages(page);
 527                         unlock_page(page);
 528                 }
 529
 530                 pagevec_release(&pvec);
 531                 cond_resched();
 532         } while (!stop);
 533
 534         *_len = len;
 535 }
 536
 537 /*
 538  * Synchronously write back the locked page and any subsequent non-locked dirty
 539  * pages.
 540  */
 541 static ssize_t afs_write_back_from_locked_page(struct address_space *mapping,
 542                                                struct writeback_control *wbc,
 543                                                struct page *page,
 544                                                loff_t start, loff_t end)
 545 {
 546         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 547         struct iov_iter iter;
 548         unsigned long priv;
 549         unsigned int offset, to, len, max_len;
 550         loff_t i_size = i_size_read(&vnode->vfs_inode);
 551         bool new_content = test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags);
 552         long count = wbc->nr_to_write;
 553         int ret;
 554
 555         _enter(",%lx,%llx-%llx", page->index, start, end);
 556
 557         if (test_set_page_writeback(page))
 558                 BUG();
 559
 560         count -= thp_nr_pages(page);
 561
 562         /* Find all consecutive lockable dirty pages that have contiguous
 563          * written regions, stopping when we find a page that is not
 564          * immediately lockable, is not dirty or is missing, or we reach the
 565          * end of the range.
 566          */
 567         priv = page_private(page);
 568         offset = afs_page_dirty_from(page, priv);
 569         to = afs_page_dirty_to(page, priv);
 570         trace_afs_page_dirty(vnode, tracepoint_string("store"), page);
 571
 572         len = to - offset;
 573         start += offset;
 574         if (start < i_size) {
 575                 /* Trim the write to the EOF; the extra data is ignored.  Also
 576                  * put an upper limit on the size of a single storedata op.
 577                  */
 578                 max_len = 65536 * 4096;
 579                 max_len = min_t(unsigned long long, max_len, end - start + 1);
 580                 max_len = min_t(unsigned long long, max_len, i_size - start);
 581
 582                 if (len < max_len &&
 583                     (to == thp_size(page) || new_content))
 584                         afs_extend_writeback(mapping, vnode, &count,
 585                                              start, max_len, new_content, &len);
 586                 len = min_t(loff_t, len, max_len);
 587         }
 588
 589         /* We now have a contiguous set of dirty pages, each with writeback
 590          * set; the first page is still locked at this point, but all the rest
 591          * have been unlocked.
 592          */
 593         unlock_page(page);
 594
 595         if (start < i_size) {
 596                 _debug("write back %x @%llx [%llx]", len, start, i_size);
 597
 598                 iov_iter_xarray(&iter, WRITE, &mapping->i_pages, start, len);
 599                 ret = afs_store_data(vnode, &iter, start, false);
 600         } else {
 601                 _debug("write discard %x @%llx [%llx]", len, start, i_size);
 602
 603                 /* The dirty region was entirely beyond the EOF. */
 604                 afs_pages_written_back(vnode, start, len);
 605                 ret = 0;
 606         }
 607
 608         switch (ret) {
 609         case 0:
 610                 wbc->nr_to_write = count;
 611                 ret = len;
 612                 break;
 613
 614         default:
 615                 pr_notice("kAFS: Unexpected error from FS.StoreData %d\n", ret);
 616                 fallthrough;
 617         case -EACCES:
 618         case -EPERM:
 619         case -ENOKEY:
 620         case -EKEYEXPIRED:
 621         case -EKEYREJECTED:
 622         case -EKEYREVOKED:
 623                 afs_redirty_pages(wbc, mapping, start, len);
 624                 mapping_set_error(mapping, ret);
 625                 break;
 626
 627         case -EDQUOT:
 628         case -ENOSPC:
 629                 afs_redirty_pages(wbc, mapping, start, len);
 630                 mapping_set_error(mapping, -ENOSPC);
 631                 break;
 632
 633         case -EROFS:
 634         case -EIO:
 635         case -EREMOTEIO:
 636         case -EFBIG:
 637         case -ENOENT:
 638         case -ENOMEDIUM:
 639         case -ENXIO:
 640                 trace_afs_file_error(vnode, ret, afs_file_error_writeback_fail);
 641                 afs_kill_pages(mapping, start, len);
 642                 mapping_set_error(mapping, ret);
 643                 break;
 644         }
 645
 646         _leave(" = %d", ret);
 647         return ret;
 648 }
 649
 650 /*
 651  * write a page back to the server
 652  * - the caller locked the page for us
 653  */
 654 int afs_writepage(struct page *page, struct writeback_control *wbc)
 655 {
 656         ssize_t ret;
 657         loff_t start;
 658
 659         _enter("{%lx},", page->index);
 660
 661         start = page->index * PAGE_SIZE;
 662         ret = afs_write_back_from_locked_page(page->mapping, wbc, page,
 663                                               start, LLONG_MAX - start);
 664         if (ret < 0) {
 665                 _leave(" = %zd", ret);
 666                 return ret;
 667         }
 668
 669         _leave(" = 0");
 670         return 0;
 671 }
 672
 673 /*
 674  * write a region of pages back to the server
 675  */
 676 static int afs_writepages_region(struct address_space *mapping,
 677                                  struct writeback_control *wbc,
 678                                  loff_t start, loff_t end, loff_t *_next)
 679 {
 680         struct page *page;
 681         ssize_t ret;
 682         int n;
 683
 684         _enter("%llx,%llx,", start, end);
 685
 686         do {
 687                 pgoff_t index = start / PAGE_SIZE;
 688
 689                 n = find_get_pages_range_tag(mapping, &index, end / PAGE_SIZE,
 690                                              PAGECACHE_TAG_DIRTY, 1, &page);
 691                 if (!n)
 692                         break;
 693
 694                 start = (loff_t)page->index * PAGE_SIZE; /* May regress with THPs */
 695
 696                 _debug("wback %lx", page->index);
 697
 698                 /* At this point we hold neither the i_pages lock nor the
 699                  * page lock: the page may be truncated or invalidated
 700                  * (changing page->mapping to NULL), or even swizzled
 701                  * back from swapper_space to tmpfs file mapping
 702                  */
 703                 if (wbc->sync_mode != WB_SYNC_NONE) {
 704                         ret = lock_page_killable(page);
 705                         if (ret < 0) {
 706                                 put_page(page);
 707                                 return ret;
 708                         }
 709                 } else {
 710                         if (!trylock_page(page)) {
 711                                 put_page(page);
 712                                 return 0;
 713                         }
 714                 }
 715
 716                 if (page->mapping != mapping || !PageDirty(page)) {
 717                         start += thp_size(page);
 718                         unlock_page(page);
 719                         put_page(page);
 720                         continue;
 721                 }
 722
 723                 if (PageWriteback(page)) {
 724                         unlock_page(page);
 725                         if (wbc->sync_mode != WB_SYNC_NONE)
 726                                 wait_on_page_writeback(page);
 727                         put_page(page);
 728                         continue;
 729                 }
 730
 731                 if (!clear_page_dirty_for_io(page))
 732                         BUG();
 733                 ret = afs_write_back_from_locked_page(mapping, wbc, page, start, end);
 734                 put_page(page);
 735                 if (ret < 0) {
 736                         _leave(" = %zd", ret);
 737                         return ret;
 738                 }
 739
 740                 start += ret;
 741
 742                 cond_resched();
 743         } while (wbc->nr_to_write > 0);
 744
 745         *_next = start;
 746         _leave(" = 0 [%llx]", *_next);
 747         return 0;
 748 }
 749
 750 /*
 751  * write some of the pending data back to the server
 752  */
 753 int afs_writepages(struct address_space *mapping,
 754                    struct writeback_control *wbc)
 755 {
 756         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 757         loff_t start, next;
 758         int ret;
 759
 760         _enter("");
 761
 762         /* We have to be careful as we can end up racing with setattr()
 763          * truncating the pagecache since the caller doesn't take a lock here
 764          * to prevent it.
 765          */
 766         if (wbc->sync_mode == WB_SYNC_ALL)
 767                 down_read(&vnode->validate_lock);
 768         else if (!down_read_trylock(&vnode->validate_lock))
 769                 return 0;
 770
 771         if (wbc->range_cyclic) {
 772                 start = mapping->writeback_index * PAGE_SIZE;
 773                 ret = afs_writepages_region(mapping, wbc, start, LLONG_MAX, &next);
 774                 if (start > 0 && wbc->nr_to_write > 0 && ret == 0)
 775                         ret = afs_writepages_region(mapping, wbc, 0, start,
 776                                                     &next);
 777                 mapping->writeback_index = next / PAGE_SIZE;
 778         } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
 779                 ret = afs_writepages_region(mapping, wbc, 0, LLONG_MAX, &next);
 780                 if (wbc->nr_to_write > 0)
 781                         mapping->writeback_index = next;
 782         } else {
 783                 ret = afs_writepages_region(mapping, wbc,
 784                                             wbc->range_start, wbc->range_end, &next);
 785         }
 786
 787         up_read(&vnode->validate_lock);
 788         _leave(" = %d", ret);
 789         return ret;
 790 }
 791
 792 /*
 793  * write to an AFS file
 794  */
 795 ssize_t afs_file_write(struct kiocb *iocb, struct iov_iter *from)
 796 {
 797         struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp));
 798         ssize_t result;
 799         size_t count = iov_iter_count(from);
 800
 801         _enter("{%llx:%llu},{%zu},",
 802                vnode->fid.vid, vnode->fid.vnode, count);
 803
 804         if (IS_SWAPFILE(&vnode->vfs_inode)) {
 805                 printk(KERN_INFO
 806                        "AFS: Attempt to write to active swap file!\n");
 807                 return -EBUSY;
 808         }
 809
 810         if (!count)
 811                 return 0;
 812
 813         result = generic_file_write_iter(iocb, from);
 814
 815         _leave(" = %zd", result);
 816         return result;
 817 }
 818
 819 /*
 820  * flush any dirty pages for this process, and check for write errors.
 821  * - the return status from this call provides a reliable indication of
 822  *   whether any write errors occurred for this process.
 823  */
 824 int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 825 {
 826         struct inode *inode = file_inode(file);
 827         struct afs_vnode *vnode = AFS_FS_I(inode);
 828
 829         _enter("{%llx:%llu},{n=%pD},%d",
 830                vnode->fid.vid, vnode->fid.vnode, file,
 831                datasync);
 832
 833         return file_write_and_wait_range(file, start, end);
 834 }
 835
 836 /*
 837  * notification that a previously read-only page is about to become writable
 838  * - if it returns an error, the caller will deliver a bus error signal
 839  */
 840 vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
 841 {
 842         struct page *page = thp_head(vmf->page);
 843         struct file *file = vmf->vma->vm_file;
 844         struct inode *inode = file_inode(file);
 845         struct afs_vnode *vnode = AFS_FS_I(inode);
 846         unsigned long priv;
 847         vm_fault_t ret = VM_FAULT_RETRY;
 848
 849         _enter("{{%llx:%llu}},{%lx}", vnode->fid.vid, vnode->fid.vnode, page->index);
 850
 851         sb_start_pagefault(inode->i_sb);
 852
 853         /* Wait for the page to be written to the cache before we allow it to
 854          * be modified.  We then assume the entire page will need writing back.
 855          */
 856 #ifdef CONFIG_AFS_FSCACHE
 857         if (PageFsCache(page) &&
 858             wait_on_page_fscache_killable(page) < 0)
 859                 goto out;
 860 #endif
 861
 862         if (wait_on_page_writeback_killable(page))
 863                 goto out;
 864
 865         if (lock_page_killable(page) < 0)
 866                 goto out;
 867
 868         /* We mustn't change page->private until writeback is complete as that
 869          * details the portion of the page we need to write back and we might
 870          * need to redirty the page if there's a problem.
 871          */
 872         if (wait_on_page_writeback_killable(page) < 0) {
 873                 unlock_page(page);
 874                 goto out;
 875         }
 876
 877         priv = afs_page_dirty(page, 0, thp_size(page));
 878         priv = afs_page_dirty_mmapped(priv);
 879         if (PagePrivate(page)) {
 880                 set_page_private(page, priv);
 881                 trace_afs_page_dirty(vnode, tracepoint_string("mkwrite+"), page);
 882         } else {
 883                 attach_page_private(page, (void *)priv);
 884                 trace_afs_page_dirty(vnode, tracepoint_string("mkwrite"), page);
 885         }
 886         file_update_time(file);
 887
 888         ret = VM_FAULT_LOCKED;
 889 out:
 890         sb_end_pagefault(inode->i_sb);
 891         return ret;
 892 }
 893
 894 /*
 895  * Prune the keys cached for writeback.  The caller must hold vnode->wb_lock.
 896  */
 897 void afs_prune_wb_keys(struct afs_vnode *vnode)
 898 {
 899         LIST_HEAD(graveyard);
 900         struct afs_wb_key *wbk, *tmp;
 901
 902         /* Discard unused keys */
 903         spin_lock(&vnode->wb_lock);
 904
 905         if (!mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_WRITEBACK) &&
 906             !mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_DIRTY)) {
 907                 list_for_each_entry_safe(wbk, tmp, &vnode->wb_keys, vnode_link) {
 908                         if (refcount_read(&wbk->usage) == 1)
 909                                 list_move(&wbk->vnode_link, &graveyard);
 910                 }
 911         }
 912
 913         spin_unlock(&vnode->wb_lock);
 914
 915         while (!list_empty(&graveyard)) {
 916                 wbk = list_entry(graveyard.next, struct afs_wb_key, vnode_link);
 917                 list_del(&wbk->vnode_link);
 918                 afs_put_wb_key(wbk);
 919         }
 920 }
 921
 922 /*
 923  * Clean up a page during invalidation.
 924  */
 925 int afs_launder_page(struct page *page)
 926 {
 927         struct address_space *mapping = page->mapping;
 928         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 929         struct iov_iter iter;
 930         struct bio_vec bv[1];
 931         unsigned long priv;
 932         unsigned int f, t;
 933         int ret = 0;
 934
 935         _enter("{%lx}", page->index);
 936
 937         priv = page_private(page);
 938         if (clear_page_dirty_for_io(page)) {
 939                 f = 0;
 940                 t = thp_size(page);
 941                 if (PagePrivate(page)) {
 942                         f = afs_page_dirty_from(page, priv);
 943                         t = afs_page_dirty_to(page, priv);
 944                 }
 945
 946                 bv[0].bv_page = page;
 947                 bv[0].bv_offset = f;
 948                 bv[0].bv_len = t - f;
 949                 iov_iter_bvec(&iter, WRITE, bv, 1, bv[0].bv_len);
 950
 951                 trace_afs_page_dirty(vnode, tracepoint_string("launder"), page);
 952                 ret = afs_store_data(vnode, &iter, (loff_t)page->index * PAGE_SIZE,
 953                                      true);
 954         }
 955
 956         trace_afs_page_dirty(vnode, tracepoint_string("laundered"), page);
 957         detach_page_private(page);
 958         wait_on_page_fscache(page);
 959         return ret;
 960 }