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                         afs_set_i_size(vnode, 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                                 put_page(page);
 476                                 break;
 477                         }
 478
 479                         if (!trylock_page(page)) {
 480                                 put_page(page);
 481                                 break;
 482                         }
 483                         if (!PageDirty(page) || PageWriteback(page)) {
 484                                 unlock_page(page);
 485                                 put_page(page);
 486                                 break;
 487                         }
 488
 489                         psize = thp_size(page);
 490                         priv = page_private(page);
 491                         f = afs_page_dirty_from(page, priv);
 492                         t = afs_page_dirty_to(page, priv);
 493                         if (f != 0 && !new_content) {
 494                                 unlock_page(page);
 495                                 put_page(page);
 496                                 break;
 497                         }
 498
 499                         len += filler + t;
 500                         filler = psize - t;
 501                         if (len >= max_len || *_count <= 0)
 502                                 stop = true;
 503                         else if (t == psize || new_content)
 504                                 stop = false;
 505
 506                         index += thp_nr_pages(page);
 507                         if (!pagevec_add(&pvec, page))
 508                                 break;
 509                         if (stop)
 510                                 break;
 511                 }
 512
 513                 if (!stop)
 514                         xas_pause(&xas);
 515                 rcu_read_unlock();
 516
 517                 /* Now, if we obtained any pages, we can shift them to being
 518                  * writable and mark them for caching.
 519                  */
 520                 if (!pagevec_count(&pvec))
 521                         break;
 522
 523                 for (i = 0; i < pagevec_count(&pvec); i++) {
 524                         page = pvec.pages[i];
 525                         trace_afs_page_dirty(vnode, tracepoint_string("store+"), page);
 526
 527                         if (!clear_page_dirty_for_io(page))
 528                                 BUG();
 529                         if (test_set_page_writeback(page))
 530                                 BUG();
 531
 532                         *_count -= thp_nr_pages(page);
 533                         unlock_page(page);
 534                 }
 535
 536                 pagevec_release(&pvec);
 537                 cond_resched();
 538         } while (!stop);
 539
 540         *_len = len;
 541 }
 542
 543 /*
 544  * Synchronously write back the locked page and any subsequent non-locked dirty
 545  * pages.
 546  */
 547 static ssize_t afs_write_back_from_locked_page(struct address_space *mapping,
 548                                                struct writeback_control *wbc,
 549                                                struct page *page,
 550                                                loff_t start, loff_t end)
 551 {
 552         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 553         struct iov_iter iter;
 554         unsigned long priv;
 555         unsigned int offset, to, len, max_len;
 556         loff_t i_size = i_size_read(&vnode->vfs_inode);
 557         bool new_content = test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags);
 558         long count = wbc->nr_to_write;
 559         int ret;
 560
 561         _enter(",%lx,%llx-%llx", page->index, start, end);
 562
 563         if (test_set_page_writeback(page))
 564                 BUG();
 565
 566         count -= thp_nr_pages(page);
 567
 568         /* Find all consecutive lockable dirty pages that have contiguous
 569          * written regions, stopping when we find a page that is not
 570          * immediately lockable, is not dirty or is missing, or we reach the
 571          * end of the range.
 572          */
 573         priv = page_private(page);
 574         offset = afs_page_dirty_from(page, priv);
 575         to = afs_page_dirty_to(page, priv);
 576         trace_afs_page_dirty(vnode, tracepoint_string("store"), page);
 577
 578         len = to - offset;
 579         start += offset;
 580         if (start < i_size) {
 581                 /* Trim the write to the EOF; the extra data is ignored.  Also
 582                  * put an upper limit on the size of a single storedata op.
 583                  */
 584                 max_len = 65536 * 4096;
 585                 max_len = min_t(unsigned long long, max_len, end - start + 1);
 586                 max_len = min_t(unsigned long long, max_len, i_size - start);
 587
 588                 if (len < max_len &&
 589                     (to == thp_size(page) || new_content))
 590                         afs_extend_writeback(mapping, vnode, &count,
 591                                              start, max_len, new_content, &len);
 592                 len = min_t(loff_t, len, max_len);
 593         }
 594
 595         /* We now have a contiguous set of dirty pages, each with writeback
 596          * set; the first page is still locked at this point, but all the rest
 597          * have been unlocked.
 598          */
 599         unlock_page(page);
 600
 601         if (start < i_size) {
 602                 _debug("write back %x @%llx [%llx]", len, start, i_size);
 603
 604                 iov_iter_xarray(&iter, WRITE, &mapping->i_pages, start, len);
 605                 ret = afs_store_data(vnode, &iter, start, false);
 606         } else {
 607                 _debug("write discard %x @%llx [%llx]", len, start, i_size);
 608
 609                 /* The dirty region was entirely beyond the EOF. */
 610                 afs_pages_written_back(vnode, start, len);
 611                 ret = 0;
 612         }
 613
 614         switch (ret) {
 615         case 0:
 616                 wbc->nr_to_write = count;
 617                 ret = len;
 618                 break;
 619
 620         default:
 621                 pr_notice("kAFS: Unexpected error from FS.StoreData %d\n", ret);
 622                 fallthrough;
 623         case -EACCES:
 624         case -EPERM:
 625         case -ENOKEY:
 626         case -EKEYEXPIRED:
 627         case -EKEYREJECTED:
 628         case -EKEYREVOKED:
 629                 afs_redirty_pages(wbc, mapping, start, len);
 630                 mapping_set_error(mapping, ret);
 631                 break;
 632
 633         case -EDQUOT:
 634         case -ENOSPC:
 635                 afs_redirty_pages(wbc, mapping, start, len);
 636                 mapping_set_error(mapping, -ENOSPC);
 637                 break;
 638
 639         case -EROFS:
 640         case -EIO:
 641         case -EREMOTEIO:
 642         case -EFBIG:
 643         case -ENOENT:
 644         case -ENOMEDIUM:
 645         case -ENXIO:
 646                 trace_afs_file_error(vnode, ret, afs_file_error_writeback_fail);
 647                 afs_kill_pages(mapping, start, len);
 648                 mapping_set_error(mapping, ret);
 649                 break;
 650         }
 651
 652         _leave(" = %d", ret);
 653         return ret;
 654 }
 655
 656 /*
 657  * write a page back to the server
 658  * - the caller locked the page for us
 659  */
 660 int afs_writepage(struct page *page, struct writeback_control *wbc)
 661 {
 662         ssize_t ret;
 663         loff_t start;
 664
 665         _enter("{%lx},", page->index);
 666
 667         start = page->index * PAGE_SIZE;
 668         ret = afs_write_back_from_locked_page(page->mapping, wbc, page,
 669                                               start, LLONG_MAX - start);
 670         if (ret < 0) {
 671                 _leave(" = %zd", ret);
 672                 return ret;
 673         }
 674
 675         _leave(" = 0");
 676         return 0;
 677 }
 678
 679 /*
 680  * write a region of pages back to the server
 681  */
 682 static int afs_writepages_region(struct address_space *mapping,
 683                                  struct writeback_control *wbc,
 684                                  loff_t start, loff_t end, loff_t *_next)
 685 {
 686         struct page *page;
 687         ssize_t ret;
 688         int n;
 689
 690         _enter("%llx,%llx,", start, end);
 691
 692         do {
 693                 pgoff_t index = start / PAGE_SIZE;
 694
 695                 n = find_get_pages_range_tag(mapping, &index, end / PAGE_SIZE,
 696                                              PAGECACHE_TAG_DIRTY, 1, &page);
 697                 if (!n)
 698                         break;
 699
 700                 start = (loff_t)page->index * PAGE_SIZE; /* May regress with THPs */
 701
 702                 _debug("wback %lx", page->index);
 703
 704                 /* At this point we hold neither the i_pages lock nor the
 705                  * page lock: the page may be truncated or invalidated
 706                  * (changing page->mapping to NULL), or even swizzled
 707                  * back from swapper_space to tmpfs file mapping
 708                  */
 709                 if (wbc->sync_mode != WB_SYNC_NONE) {
 710                         ret = lock_page_killable(page);
 711                         if (ret < 0) {
 712                                 put_page(page);
 713                                 return ret;
 714                         }
 715                 } else {
 716                         if (!trylock_page(page)) {
 717                                 put_page(page);
 718                                 return 0;
 719                         }
 720                 }
 721
 722                 if (page->mapping != mapping || !PageDirty(page)) {
 723                         start += thp_size(page);
 724                         unlock_page(page);
 725                         put_page(page);
 726                         continue;
 727                 }
 728
 729                 if (PageWriteback(page)) {
 730                         unlock_page(page);
 731                         if (wbc->sync_mode != WB_SYNC_NONE)
 732                                 wait_on_page_writeback(page);
 733                         put_page(page);
 734                         continue;
 735                 }
 736
 737                 if (!clear_page_dirty_for_io(page))
 738                         BUG();
 739                 ret = afs_write_back_from_locked_page(mapping, wbc, page, start, end);
 740                 put_page(page);
 741                 if (ret < 0) {
 742                         _leave(" = %zd", ret);
 743                         return ret;
 744                 }
 745
 746                 start += ret;
 747
 748                 cond_resched();
 749         } while (wbc->nr_to_write > 0);
 750
 751         *_next = start;
 752         _leave(" = 0 [%llx]", *_next);
 753         return 0;
 754 }
 755
 756 /*
 757  * write some of the pending data back to the server
 758  */
 759 int afs_writepages(struct address_space *mapping,
 760                    struct writeback_control *wbc)
 761 {
 762         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 763         loff_t start, next;
 764         int ret;
 765
 766         _enter("");
 767
 768         /* We have to be careful as we can end up racing with setattr()
 769          * truncating the pagecache since the caller doesn't take a lock here
 770          * to prevent it.
 771          */
 772         if (wbc->sync_mode == WB_SYNC_ALL)
 773                 down_read(&vnode->validate_lock);
 774         else if (!down_read_trylock(&vnode->validate_lock))
 775                 return 0;
 776
 777         if (wbc->range_cyclic) {
 778                 start = mapping->writeback_index * PAGE_SIZE;
 779                 ret = afs_writepages_region(mapping, wbc, start, LLONG_MAX, &next);
 780                 if (ret == 0) {
 781                         mapping->writeback_index = next / PAGE_SIZE;
 782                         if (start > 0 && wbc->nr_to_write > 0) {
 783                                 ret = afs_writepages_region(mapping, wbc, 0,
 784                                                             start, &next);
 785                                 if (ret == 0)
 786                                         mapping->writeback_index =
 787                                                 next / PAGE_SIZE;
 788                         }
 789                 }
 790         } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
 791                 ret = afs_writepages_region(mapping, wbc, 0, LLONG_MAX, &next);
 792                 if (wbc->nr_to_write > 0 && ret == 0)
 793                         mapping->writeback_index = next / PAGE_SIZE;
 794         } else {
 795                 ret = afs_writepages_region(mapping, wbc,
 796                                             wbc->range_start, wbc->range_end, &next);
 797         }
 798
 799         up_read(&vnode->validate_lock);
 800         _leave(" = %d", ret);
 801         return ret;
 802 }
 803
 804 /*
 805  * write to an AFS file
 806  */
 807 ssize_t afs_file_write(struct kiocb *iocb, struct iov_iter *from)
 808 {
 809         struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp));
 810         struct afs_file *af = iocb->ki_filp->private_data;
 811         ssize_t result;
 812         size_t count = iov_iter_count(from);
 813
 814         _enter("{%llx:%llu},{%zu},",
 815                vnode->fid.vid, vnode->fid.vnode, count);
 816
 817         if (IS_SWAPFILE(&vnode->vfs_inode)) {
 818                 printk(KERN_INFO
 819                        "AFS: Attempt to write to active swap file!\n");
 820                 return -EBUSY;
 821         }
 822
 823         if (!count)
 824                 return 0;
 825
 826         result = afs_validate(vnode, af->key);
 827         if (result < 0)
 828                 return result;
 829
 830         result = generic_file_write_iter(iocb, from);
 831
 832         _leave(" = %zd", result);
 833         return result;
 834 }
 835
 836 /*
 837  * flush any dirty pages for this process, and check for write errors.
 838  * - the return status from this call provides a reliable indication of
 839  *   whether any write errors occurred for this process.
 840  */
 841 int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 842 {
 843         struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
 844         struct afs_file *af = file->private_data;
 845         int ret;
 846
 847         _enter("{%llx:%llu},{n=%pD},%d",
 848                vnode->fid.vid, vnode->fid.vnode, file,
 849                datasync);
 850
 851         ret = afs_validate(vnode, af->key);
 852         if (ret < 0)
 853                 return ret;
 854
 855         return file_write_and_wait_range(file, start, end);
 856 }
 857
 858 /*
 859  * notification that a previously read-only page is about to become writable
 860  * - if it returns an error, the caller will deliver a bus error signal
 861  */
 862 vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
 863 {
 864         struct page *page = thp_head(vmf->page);
 865         struct file *file = vmf->vma->vm_file;
 866         struct inode *inode = file_inode(file);
 867         struct afs_vnode *vnode = AFS_FS_I(inode);
 868         struct afs_file *af = file->private_data;
 869         unsigned long priv;
 870         vm_fault_t ret = VM_FAULT_RETRY;
 871
 872         _enter("{{%llx:%llu}},{%lx}", vnode->fid.vid, vnode->fid.vnode, page->index);
 873
 874         afs_validate(vnode, af->key);
 875
 876         sb_start_pagefault(inode->i_sb);
 877
 878         /* Wait for the page to be written to the cache before we allow it to
 879          * be modified.  We then assume the entire page will need writing back.
 880          */
 881 #ifdef CONFIG_AFS_FSCACHE
 882         if (PageFsCache(page) &&
 883             wait_on_page_fscache_killable(page) < 0)
 884                 goto out;
 885 #endif
 886
 887         if (wait_on_page_writeback_killable(page))
 888                 goto out;
 889
 890         if (lock_page_killable(page) < 0)
 891                 goto out;
 892
 893         /* We mustn't change page->private until writeback is complete as that
 894          * details the portion of the page we need to write back and we might
 895          * need to redirty the page if there's a problem.
 896          */
 897         if (wait_on_page_writeback_killable(page) < 0) {
 898                 unlock_page(page);
 899                 goto out;
 900         }
 901
 902         priv = afs_page_dirty(page, 0, thp_size(page));
 903         priv = afs_page_dirty_mmapped(priv);
 904         if (PagePrivate(page)) {
 905                 set_page_private(page, priv);
 906                 trace_afs_page_dirty(vnode, tracepoint_string("mkwrite+"), page);
 907         } else {
 908                 attach_page_private(page, (void *)priv);
 909                 trace_afs_page_dirty(vnode, tracepoint_string("mkwrite"), page);
 910         }
 911         file_update_time(file);
 912
 913         ret = VM_FAULT_LOCKED;
 914 out:
 915         sb_end_pagefault(inode->i_sb);
 916         return ret;
 917 }
 918
 919 /*
 920  * Prune the keys cached for writeback.  The caller must hold vnode->wb_lock.
 921  */
 922 void afs_prune_wb_keys(struct afs_vnode *vnode)
 923 {
 924         LIST_HEAD(graveyard);
 925         struct afs_wb_key *wbk, *tmp;
 926
 927         /* Discard unused keys */
 928         spin_lock(&vnode->wb_lock);
 929
 930         if (!mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_WRITEBACK) &&
 931             !mapping_tagged(&vnode->vfs_inode.i_data, PAGECACHE_TAG_DIRTY)) {
 932                 list_for_each_entry_safe(wbk, tmp, &vnode->wb_keys, vnode_link) {
 933                         if (refcount_read(&wbk->usage) == 1)
 934                                 list_move(&wbk->vnode_link, &graveyard);
 935                 }
 936         }
 937
 938         spin_unlock(&vnode->wb_lock);
 939
 940         while (!list_empty(&graveyard)) {
 941                 wbk = list_entry(graveyard.next, struct afs_wb_key, vnode_link);
 942                 list_del(&wbk->vnode_link);
 943                 afs_put_wb_key(wbk);
 944         }
 945 }
 946
 947 /*
 948  * Clean up a page during invalidation.
 949  */
 950 int afs_launder_page(struct page *page)
 951 {
 952         struct address_space *mapping = page->mapping;
 953         struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 954         struct iov_iter iter;
 955         struct bio_vec bv[1];
 956         unsigned long priv;
 957         unsigned int f, t;
 958         int ret = 0;
 959
 960         _enter("{%lx}", page->index);
 961
 962         priv = page_private(page);
 963         if (clear_page_dirty_for_io(page)) {
 964                 f = 0;
 965                 t = thp_size(page);
 966                 if (PagePrivate(page)) {
 967                         f = afs_page_dirty_from(page, priv);
 968                         t = afs_page_dirty_to(page, priv);
 969                 }
 970
 971                 bv[0].bv_page = page;
 972                 bv[0].bv_offset = f;
 973                 bv[0].bv_len = t - f;
 974                 iov_iter_bvec(&iter, WRITE, bv, 1, bv[0].bv_len);
 975
 976                 trace_afs_page_dirty(vnode, tracepoint_string("launder"), page);
 977                 ret = afs_store_data(vnode, &iter, (loff_t)page->index * PAGE_SIZE,
 978                                      true);
 979         }
 980
 981         trace_afs_page_dirty(vnode, tracepoint_string("laundered"), page);
 982         detach_page_private(page);
 983         wait_on_page_fscache(page);
 984         return ret;
 985 }