fs/dax.c

   1 /*
   2  * fs/dax.c - Direct Access filesystem code
   3  * Copyright (c) 2013-2014 Intel Corporation
   4  * Author: Matthew Wilcox <matthew.r.wilcox@intel.com>
   5  * Author: Ross Zwisler <ross.zwisler@linux.intel.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms and conditions of the GNU General Public License,
   9  * version 2, as published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  14  * more details.
  15  */
  16
  17 #include <linux/atomic.h>
  18 #include <linux/blkdev.h>
  19 #include <linux/buffer_head.h>
  20 #include <linux/dax.h>
  21 #include <linux/fs.h>
  22 #include <linux/genhd.h>
  23 #include <linux/highmem.h>
  24 #include <linux/memcontrol.h>
  25 #include <linux/mm.h>
  26 #include <linux/mutex.h>
  27 #include <linux/pagevec.h>
  28 #include <linux/pmem.h>
  29 #include <linux/sched.h>
  30 #include <linux/uio.h>
  31 #include <linux/vmstat.h>
  32 #include <linux/pfn_t.h>
  33 #include <linux/sizes.h>
  34 #include <linux/mmu_notifier.h>
  35 #include <linux/iomap.h>
  36 #include "internal.h"
  37
  38 /* We choose 4096 entries - same as per-zone page wait tables */
  39 #define DAX_WAIT_TABLE_BITS 12
  40 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
  41
  42 static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
  43
  44 static int __init init_dax_wait_table(void)
  45 {
  46         int i;
  47
  48         for (i = 0; i < DAX_WAIT_TABLE_ENTRIES; i++)
  49                 init_waitqueue_head(wait_table + i);
  50         return 0;
  51 }
  52 fs_initcall(init_dax_wait_table);
  53
  54 static long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax)
  55 {
  56         struct request_queue *q = bdev->bd_queue;
  57         long rc = -EIO;
  58
  59         dax->addr = ERR_PTR(-EIO);
  60         if (blk_queue_enter(q, true) != 0)
  61                 return rc;
  62
  63         rc = bdev_direct_access(bdev, dax);
  64         if (rc < 0) {
  65                 dax->addr = ERR_PTR(rc);
  66                 blk_queue_exit(q);
  67                 return rc;
  68         }
  69         return rc;
  70 }
  71
  72 static void dax_unmap_atomic(struct block_device *bdev,
  73                 const struct blk_dax_ctl *dax)
  74 {
  75         if (IS_ERR(dax->addr))
  76                 return;
  77         blk_queue_exit(bdev->bd_queue);
  78 }
  79
  80 static int dax_is_pmd_entry(void *entry)
  81 {
  82         return (unsigned long)entry & RADIX_DAX_PMD;
  83 }
  84
  85 static int dax_is_pte_entry(void *entry)
  86 {
  87         return !((unsigned long)entry & RADIX_DAX_PMD);
  88 }
  89
  90 static int dax_is_zero_entry(void *entry)
  91 {
  92         return (unsigned long)entry & RADIX_DAX_HZP;
  93 }
  94
  95 static int dax_is_empty_entry(void *entry)
  96 {
  97         return (unsigned long)entry & RADIX_DAX_EMPTY;
  98 }
  99
 100 struct page *read_dax_sector(struct block_device *bdev, sector_t n)
 101 {
 102         struct page *page = alloc_pages(GFP_KERNEL, 0);
 103         struct blk_dax_ctl dax = {
 104                 .size = PAGE_SIZE,
 105                 .sector = n & ~((((int) PAGE_SIZE) / 512) - 1),
 106         };
 107         long rc;
 108
 109         if (!page)
 110                 return ERR_PTR(-ENOMEM);
 111
 112         rc = dax_map_atomic(bdev, &dax);
 113         if (rc < 0)
 114                 return ERR_PTR(rc);
 115         memcpy_from_pmem(page_address(page), dax.addr, PAGE_SIZE);
 116         dax_unmap_atomic(bdev, &dax);
 117         return page;
 118 }
 119
 120 /*
 121  * DAX radix tree locking
 122  */
 123 struct exceptional_entry_key {
 124         struct address_space *mapping;
 125         pgoff_t entry_start;
 126 };
 127
 128 struct wait_exceptional_entry_queue {
 129         wait_queue_t wait;
 130         struct exceptional_entry_key key;
 131 };
 132
 133 static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
 134                 pgoff_t index, void *entry, struct exceptional_entry_key *key)
 135 {
 136         unsigned long hash;
 137
 138         /*
 139          * If 'entry' is a PMD, align the 'index' that we use for the wait
 140          * queue to the start of that PMD.  This ensures that all offsets in
 141          * the range covered by the PMD map to the same bit lock.
 142          */
 143         if (dax_is_pmd_entry(entry))
 144                 index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
 145
 146         key->mapping = mapping;
 147         key->entry_start = index;
 148
 149         hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS);
 150         return wait_table + hash;
 151 }
 152
 153 static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode,
 154                                        int sync, void *keyp)
 155 {
 156         struct exceptional_entry_key *key = keyp;
 157         struct wait_exceptional_entry_queue *ewait =
 158                 container_of(wait, struct wait_exceptional_entry_queue, wait);
 159
 160         if (key->mapping != ewait->key.mapping ||
 161             key->entry_start != ewait->key.entry_start)
 162                 return 0;
 163         return autoremove_wake_function(wait, mode, sync, NULL);
 164 }
 165
 166 /*
 167  * Check whether the given slot is locked. The function must be called with
 168  * mapping->tree_lock held
 169  */
 170 static inline int slot_locked(struct address_space *mapping, void **slot)
 171 {
 172         unsigned long entry = (unsigned long)
 173                 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
 174         return entry & RADIX_DAX_ENTRY_LOCK;
 175 }
 176
 177 /*
 178  * Mark the given slot is locked. The function must be called with
 179  * mapping->tree_lock held
 180  */
 181 static inline void *lock_slot(struct address_space *mapping, void **slot)
 182 {
 183         unsigned long entry = (unsigned long)
 184                 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
 185
 186         entry |= RADIX_DAX_ENTRY_LOCK;
 187         radix_tree_replace_slot(&mapping->page_tree, slot, (void *)entry);
 188         return (void *)entry;
 189 }
 190
 191 /*
 192  * Mark the given slot is unlocked. The function must be called with
 193  * mapping->tree_lock held
 194  */
 195 static inline void *unlock_slot(struct address_space *mapping, void **slot)
 196 {
 197         unsigned long entry = (unsigned long)
 198                 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
 199
 200         entry &= ~(unsigned long)RADIX_DAX_ENTRY_LOCK;
 201         radix_tree_replace_slot(&mapping->page_tree, slot, (void *)entry);
 202         return (void *)entry;
 203 }
 204
 205 /*
 206  * Lookup entry in radix tree, wait for it to become unlocked if it is
 207  * exceptional entry and return it. The caller must call
 208  * put_unlocked_mapping_entry() when he decided not to lock the entry or
 209  * put_locked_mapping_entry() when he locked the entry and now wants to
 210  * unlock it.
 211  *
 212  * The function must be called with mapping->tree_lock held.
 213  */
 214 static void *get_unlocked_mapping_entry(struct address_space *mapping,
 215                                         pgoff_t index, void ***slotp)
 216 {
 217         void *entry, **slot;
 218         struct wait_exceptional_entry_queue ewait;
 219         wait_queue_head_t *wq;
 220
 221         init_wait(&ewait.wait);
 222         ewait.wait.func = wake_exceptional_entry_func;
 223
 224         for (;;) {
 225                 entry = __radix_tree_lookup(&mapping->page_tree, index, NULL,
 226                                           &slot);
 227                 if (!entry || !radix_tree_exceptional_entry(entry) ||
 228                     !slot_locked(mapping, slot)) {
 229                         if (slotp)
 230                                 *slotp = slot;
 231                         return entry;
 232                 }
 233
 234                 wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
 235                 prepare_to_wait_exclusive(wq, &ewait.wait,
 236                                           TASK_UNINTERRUPTIBLE);
 237                 spin_unlock_irq(&mapping->tree_lock);
 238                 schedule();
 239                 finish_wait(wq, &ewait.wait);
 240                 spin_lock_irq(&mapping->tree_lock);
 241         }
 242 }
 243
 244 static void dax_unlock_mapping_entry(struct address_space *mapping,
 245                                      pgoff_t index)
 246 {
 247         void *entry, **slot;
 248
 249         spin_lock_irq(&mapping->tree_lock);
 250         entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
 251         if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) ||
 252                          !slot_locked(mapping, slot))) {
 253                 spin_unlock_irq(&mapping->tree_lock);
 254                 return;
 255         }
 256         unlock_slot(mapping, slot);
 257         spin_unlock_irq(&mapping->tree_lock);
 258         dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 259 }
 260
 261 static void put_locked_mapping_entry(struct address_space *mapping,
 262                                      pgoff_t index, void *entry)
 263 {
 264         if (!radix_tree_exceptional_entry(entry)) {
 265                 unlock_page(entry);
 266                 put_page(entry);
 267         } else {
 268                 dax_unlock_mapping_entry(mapping, index);
 269         }
 270 }
 271
 272 /*
 273  * Called when we are done with radix tree entry we looked up via
 274  * get_unlocked_mapping_entry() and which we didn't lock in the end.
 275  */
 276 static void put_unlocked_mapping_entry(struct address_space *mapping,
 277                                        pgoff_t index, void *entry)
 278 {
 279         if (!radix_tree_exceptional_entry(entry))
 280                 return;
 281
 282         /* We have to wake up next waiter for the radix tree entry lock */
 283         dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 284 }
 285
 286 /*
 287  * Find radix tree entry at given index. If it points to a page, return with
 288  * the page locked. If it points to the exceptional entry, return with the
 289  * radix tree entry locked. If the radix tree doesn't contain given index,
 290  * create empty exceptional entry for the index and return with it locked.
 291  *
 292  * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
 293  * either return that locked entry or will return an error.  This error will
 294  * happen if there are any 4k entries (either zero pages or DAX entries)
 295  * within the 2MiB range that we are requesting.
 296  *
 297  * We always favor 4k entries over 2MiB entries. There isn't a flow where we
 298  * evict 4k entries in order to 'upgrade' them to a 2MiB entry.  A 2MiB
 299  * insertion will fail if it finds any 4k entries already in the tree, and a
 300  * 4k insertion will cause an existing 2MiB entry to be unmapped and
 301  * downgraded to 4k entries.  This happens for both 2MiB huge zero pages as
 302  * well as 2MiB empty entries.
 303  *
 304  * The exception to this downgrade path is for 2MiB DAX PMD entries that have
 305  * real storage backing them.  We will leave these real 2MiB DAX entries in
 306  * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
 307  *
 308  * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
 309  * persistent memory the benefit is doubtful. We can add that later if we can
 310  * show it helps.
 311  */
 312 static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
 313                 unsigned long size_flag)
 314 {
 315         bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
 316         void *entry, **slot;
 317
 318 restart:
 319         spin_lock_irq(&mapping->tree_lock);
 320         entry = get_unlocked_mapping_entry(mapping, index, &slot);
 321
 322         if (entry) {
 323                 if (size_flag & RADIX_DAX_PMD) {
 324                         if (!radix_tree_exceptional_entry(entry) ||
 325                             dax_is_pte_entry(entry)) {
 326                                 put_unlocked_mapping_entry(mapping, index,
 327                                                 entry);
 328                                 entry = ERR_PTR(-EEXIST);
 329                                 goto out_unlock;
 330                         }
 331                 } else { /* trying to grab a PTE entry */
 332                         if (radix_tree_exceptional_entry(entry) &&
 333                             dax_is_pmd_entry(entry) &&
 334                             (dax_is_zero_entry(entry) ||
 335                              dax_is_empty_entry(entry))) {
 336                                 pmd_downgrade = true;
 337                         }
 338                 }
 339         }
 340
 341         /* No entry for given index? Make sure radix tree is big enough. */
 342         if (!entry || pmd_downgrade) {
 343                 int err;
 344
 345                 if (pmd_downgrade) {
 346                         /*
 347                          * Make sure 'entry' remains valid while we drop
 348                          * mapping->tree_lock.
 349                          */
 350                         entry = lock_slot(mapping, slot);
 351                 }
 352
 353                 spin_unlock_irq(&mapping->tree_lock);
 354                 /*
 355                  * Besides huge zero pages the only other thing that gets
 356                  * downgraded are empty entries which don't need to be
 357                  * unmapped.
 358                  */
 359                 if (pmd_downgrade && dax_is_zero_entry(entry))
 360                         unmap_mapping_range(mapping,
 361                                 (index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
 362
 363                 err = radix_tree_preload(
 364                                 mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
 365                 if (err) {
 366                         if (pmd_downgrade)
 367                                 put_locked_mapping_entry(mapping, index, entry);
 368                         return ERR_PTR(err);
 369                 }
 370                 spin_lock_irq(&mapping->tree_lock);
 371
 372                 if (pmd_downgrade) {
 373                         radix_tree_delete(&mapping->page_tree, index);
 374                         mapping->nrexceptional--;
 375                         dax_wake_mapping_entry_waiter(mapping, index, entry,
 376                                         true);
 377                 }
 378
 379                 entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
 380
 381                 err = __radix_tree_insert(&mapping->page_tree, index,
 382                                 dax_radix_order(entry), entry);
 383                 radix_tree_preload_end();
 384                 if (err) {
 385                         spin_unlock_irq(&mapping->tree_lock);
 386                         /*
 387                          * Someone already created the entry?  This is a
 388                          * normal failure when inserting PMDs in a range
 389                          * that already contains PTEs.  In that case we want
 390                          * to return -EEXIST immediately.
 391                          */
 392                         if (err == -EEXIST && !(size_flag & RADIX_DAX_PMD))
 393                                 goto restart;
 394                         /*
 395                          * Our insertion of a DAX PMD entry failed, most
 396                          * likely because it collided with a PTE sized entry
 397                          * at a different index in the PMD range.  We haven't
 398                          * inserted anything into the radix tree and have no
 399                          * waiters to wake.
 400                          */
 401                         return ERR_PTR(err);
 402                 }
 403                 /* Good, we have inserted empty locked entry into the tree. */
 404                 mapping->nrexceptional++;
 405                 spin_unlock_irq(&mapping->tree_lock);
 406                 return entry;
 407         }
 408         /* Normal page in radix tree? */
 409         if (!radix_tree_exceptional_entry(entry)) {
 410                 struct page *page = entry;
 411
 412                 get_page(page);
 413                 spin_unlock_irq(&mapping->tree_lock);
 414                 lock_page(page);
 415                 /* Page got truncated? Retry... */
 416                 if (unlikely(page->mapping != mapping)) {
 417                         unlock_page(page);
 418                         put_page(page);
 419                         goto restart;
 420                 }
 421                 return page;
 422         }
 423         entry = lock_slot(mapping, slot);
 424  out_unlock:
 425         spin_unlock_irq(&mapping->tree_lock);
 426         return entry;
 427 }
 428
 429 /*
 430  * We do not necessarily hold the mapping->tree_lock when we call this
 431  * function so it is possible that 'entry' is no longer a valid item in the
 432  * radix tree.  This is okay because all we really need to do is to find the
 433  * correct waitqueue where tasks might be waiting for that old 'entry' and
 434  * wake them.
 435  */
 436 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 437                 pgoff_t index, void *entry, bool wake_all)
 438 {
 439         struct exceptional_entry_key key;
 440         wait_queue_head_t *wq;
 441
 442         wq = dax_entry_waitqueue(mapping, index, entry, &key);
 443
 444         /*
 445          * Checking for locked entry and prepare_to_wait_exclusive() happens
 446          * under mapping->tree_lock, ditto for entry handling in our callers.
 447          * So at this point all tasks that could have seen our entry locked
 448          * must be in the waitqueue and the following check will see them.
 449          */
 450         if (waitqueue_active(wq))
 451                 __wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
 452 }
 453
 454 /*
 455  * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
 456  * entry to get unlocked before deleting it.
 457  */
 458 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
 459 {
 460         void *entry;
 461
 462         spin_lock_irq(&mapping->tree_lock);
 463         entry = get_unlocked_mapping_entry(mapping, index, NULL);
 464         /*
 465          * This gets called from truncate / punch_hole path. As such, the caller
 466          * must hold locks protecting against concurrent modifications of the
 467          * radix tree (usually fs-private i_mmap_sem for writing). Since the
 468          * caller has seen exceptional entry for this index, we better find it
 469          * at that index as well...
 470          */
 471         if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry))) {
 472                 spin_unlock_irq(&mapping->tree_lock);
 473                 return 0;
 474         }
 475         radix_tree_delete(&mapping->page_tree, index);
 476         mapping->nrexceptional--;
 477         spin_unlock_irq(&mapping->tree_lock);
 478         dax_wake_mapping_entry_waiter(mapping, index, entry, true);
 479
 480         return 1;
 481 }
 482
 483 /*
 484  * The user has performed a load from a hole in the file.  Allocating
 485  * a new page in the file would cause excessive storage usage for
 486  * workloads with sparse files.  We allocate a page cache page instead.
 487  * We'll kick it out of the page cache if it's ever written to,
 488  * otherwise it will simply fall out of the page cache under memory
 489  * pressure without ever having been dirtied.
 490  */
 491 static int dax_load_hole(struct address_space *mapping, void *entry,
 492                          struct vm_fault *vmf)
 493 {
 494         struct page *page;
 495
 496         /* Hole page already exists? Return it...  */
 497         if (!radix_tree_exceptional_entry(entry)) {
 498                 vmf->page = entry;
 499                 return VM_FAULT_LOCKED;
 500         }
 501
 502         /* This will replace locked radix tree entry with a hole page */
 503         page = find_or_create_page(mapping, vmf->pgoff,
 504                                    vmf->gfp_mask | __GFP_ZERO);
 505         if (!page)
 506                 return VM_FAULT_OOM;
 507         vmf->page = page;
 508         return VM_FAULT_LOCKED;
 509 }
 510
 511 static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size,
 512                 struct page *to, unsigned long vaddr)
 513 {
 514         struct blk_dax_ctl dax = {
 515                 .sector = sector,
 516                 .size = size,
 517         };
 518         void *vto;
 519
 520         if (dax_map_atomic(bdev, &dax) < 0)
 521                 return PTR_ERR(dax.addr);
 522         vto = kmap_atomic(to);
 523         copy_user_page(vto, (void __force *)dax.addr, vaddr, to);
 524         kunmap_atomic(vto);
 525         dax_unmap_atomic(bdev, &dax);
 526         return 0;
 527 }
 528
 529 /*
 530  * By this point grab_mapping_entry() has ensured that we have a locked entry
 531  * of the appropriate size so we don't have to worry about downgrading PMDs to
 532  * PTEs.  If we happen to be trying to insert a PTE and there is a PMD
 533  * already in the tree, we will skip the insertion and just dirty the PMD as
 534  * appropriate.
 535  */
 536 static void *dax_insert_mapping_entry(struct address_space *mapping,
 537                                       struct vm_fault *vmf,
 538                                       void *entry, sector_t sector,
 539                                       unsigned long flags)
 540 {
 541         struct radix_tree_root *page_tree = &mapping->page_tree;
 542         int error = 0;
 543         bool hole_fill = false;
 544         void *new_entry;
 545         pgoff_t index = vmf->pgoff;
 546
 547         if (vmf->flags & FAULT_FLAG_WRITE)
 548                 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
 549
 550         /* Replacing hole page with block mapping? */
 551         if (!radix_tree_exceptional_entry(entry)) {
 552                 hole_fill = true;
 553                 /*
 554                  * Unmap the page now before we remove it from page cache below.
 555                  * The page is locked so it cannot be faulted in again.
 556                  */
 557                 unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
 558                                     PAGE_SIZE, 0);
 559                 error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM);
 560                 if (error)
 561                         return ERR_PTR(error);
 562         } else if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_HZP)) {
 563                 /* replacing huge zero page with PMD block mapping */
 564                 unmap_mapping_range(mapping,
 565                         (vmf->pgoff << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
 566         }
 567
 568         spin_lock_irq(&mapping->tree_lock);
 569         new_entry = dax_radix_locked_entry(sector, flags);
 570
 571         if (hole_fill) {
 572                 __delete_from_page_cache(entry, NULL);
 573                 /* Drop pagecache reference */
 574                 put_page(entry);
 575                 error = __radix_tree_insert(page_tree, index,
 576                                 dax_radix_order(new_entry), new_entry);
 577                 if (error) {
 578                         new_entry = ERR_PTR(error);
 579                         goto unlock;
 580                 }
 581                 mapping->nrexceptional++;
 582         } else if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
 583                 /*
 584                  * Only swap our new entry into the radix tree if the current
 585                  * entry is a zero page or an empty entry.  If a normal PTE or
 586                  * PMD entry is already in the tree, we leave it alone.  This
 587                  * means that if we are trying to insert a PTE and the
 588                  * existing entry is a PMD, we will just leave the PMD in the
 589                  * tree and dirty it if necessary.
 590                  */
 591                 struct radix_tree_node *node;
 592                 void **slot;
 593                 void *ret;
 594
 595                 ret = __radix_tree_lookup(page_tree, index, &node, &slot);
 596                 WARN_ON_ONCE(ret != entry);
 597                 __radix_tree_replace(page_tree, node, slot,
 598                                      new_entry, NULL, NULL);
 599         }
 600         if (vmf->flags & FAULT_FLAG_WRITE)
 601                 radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);
 602  unlock:
 603         spin_unlock_irq(&mapping->tree_lock);
 604         if (hole_fill) {
 605                 radix_tree_preload_end();
 606                 /*
 607                  * We don't need hole page anymore, it has been replaced with
 608                  * locked radix tree entry now.
 609                  */
 610                 if (mapping->a_ops->freepage)
 611                         mapping->a_ops->freepage(entry);
 612                 unlock_page(entry);
 613                 put_page(entry);
 614         }
 615         return new_entry;
 616 }
 617
 618 static inline unsigned long
 619 pgoff_address(pgoff_t pgoff, struct vm_area_struct *vma)
 620 {
 621         unsigned long address;
 622
 623         address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
 624         VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
 625         return address;
 626 }
 627
 628 /* Walk all mappings of a given index of a file and writeprotect them */
 629 static void dax_mapping_entry_mkclean(struct address_space *mapping,
 630                                       pgoff_t index, unsigned long pfn)
 631 {
 632         struct vm_area_struct *vma;
 633         pte_t *ptep;
 634         pte_t pte;
 635         spinlock_t *ptl;
 636         bool changed;
 637
 638         i_mmap_lock_read(mapping);
 639         vma_interval_tree_foreach(vma, &mapping->i_mmap, index, index) {
 640                 unsigned long address;
 641
 642                 cond_resched();
 643
 644                 if (!(vma->vm_flags & VM_SHARED))
 645                         continue;
 646
 647                 address = pgoff_address(index, vma);
 648                 changed = false;
 649                 if (follow_pte(vma->vm_mm, address, &ptep, &ptl))
 650                         continue;
 651                 if (pfn != pte_pfn(*ptep))
 652                         goto unlock;
 653                 if (!pte_dirty(*ptep) && !pte_write(*ptep))
 654                         goto unlock;
 655
 656                 flush_cache_page(vma, address, pfn);
 657                 pte = ptep_clear_flush(vma, address, ptep);
 658                 pte = pte_wrprotect(pte);
 659                 pte = pte_mkclean(pte);
 660                 set_pte_at(vma->vm_mm, address, ptep, pte);
 661                 changed = true;
 662 unlock:
 663                 pte_unmap_unlock(ptep, ptl);
 664
 665                 if (changed)
 666                         mmu_notifier_invalidate_page(vma->vm_mm, address);
 667         }
 668         i_mmap_unlock_read(mapping);
 669 }
 670
 671 static int dax_writeback_one(struct block_device *bdev,
 672                 struct address_space *mapping, pgoff_t index, void *entry)
 673 {
 674         struct radix_tree_root *page_tree = &mapping->page_tree;
 675         struct blk_dax_ctl dax;
 676         void *entry2, **slot;
 677         int ret = 0;
 678
 679         /*
 680          * A page got tagged dirty in DAX mapping? Something is seriously
 681          * wrong.
 682          */
 683         if (WARN_ON(!radix_tree_exceptional_entry(entry)))
 684                 return -EIO;
 685
 686         spin_lock_irq(&mapping->tree_lock);
 687         entry2 = get_unlocked_mapping_entry(mapping, index, &slot);
 688         /* Entry got punched out / reallocated? */
 689         if (!entry2 || !radix_tree_exceptional_entry(entry2))
 690                 goto put_unlocked;
 691         /*
 692          * Entry got reallocated elsewhere? No need to writeback. We have to
 693          * compare sectors as we must not bail out due to difference in lockbit
 694          * or entry type.
 695          */
 696         if (dax_radix_sector(entry2) != dax_radix_sector(entry))
 697                 goto put_unlocked;
 698         if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
 699                                 dax_is_zero_entry(entry))) {
 700                 ret = -EIO;
 701                 goto put_unlocked;
 702         }
 703
 704         /* Another fsync thread may have already written back this entry */
 705         if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
 706                 goto put_unlocked;
 707         /* Lock the entry to serialize with page faults */
 708         entry = lock_slot(mapping, slot);
 709         /*
 710          * We can clear the tag now but we have to be careful so that concurrent
 711          * dax_writeback_one() calls for the same index cannot finish before we
 712          * actually flush the caches. This is achieved as the calls will look
 713          * at the entry only under tree_lock and once they do that they will
 714          * see the entry locked and wait for it to unlock.
 715          */
 716         radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE);
 717         spin_unlock_irq(&mapping->tree_lock);
 718
 719         /*
 720          * Even if dax_writeback_mapping_range() was given a wbc->range_start
 721          * in the middle of a PMD, the 'index' we are given will be aligned to
 722          * the start index of the PMD, as will the sector we pull from
 723          * 'entry'.  This allows us to flush for PMD_SIZE and not have to
 724          * worry about partial PMD writebacks.
 725          */
 726         dax.sector = dax_radix_sector(entry);
 727         dax.size = PAGE_SIZE << dax_radix_order(entry);
 728
 729         /*
 730          * We cannot hold tree_lock while calling dax_map_atomic() because it
 731          * eventually calls cond_resched().
 732          */
 733         ret = dax_map_atomic(bdev, &dax);
 734         if (ret < 0) {
 735                 put_locked_mapping_entry(mapping, index, entry);
 736                 return ret;
 737         }
 738
 739         if (WARN_ON_ONCE(ret < dax.size)) {
 740                 ret = -EIO;
 741                 goto unmap;
 742         }
 743
 744         dax_mapping_entry_mkclean(mapping, index, pfn_t_to_pfn(dax.pfn));
 745         wb_cache_pmem(dax.addr, dax.size);
 746         /*
 747          * After we have flushed the cache, we can clear the dirty tag. There
 748          * cannot be new dirty data in the pfn after the flush has completed as
 749          * the pfn mappings are writeprotected and fault waits for mapping
 750          * entry lock.
 751          */
 752         spin_lock_irq(&mapping->tree_lock);
 753         radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_DIRTY);
 754         spin_unlock_irq(&mapping->tree_lock);
 755  unmap:
 756         dax_unmap_atomic(bdev, &dax);
 757         put_locked_mapping_entry(mapping, index, entry);
 758         return ret;
 759
 760  put_unlocked:
 761         put_unlocked_mapping_entry(mapping, index, entry2);
 762         spin_unlock_irq(&mapping->tree_lock);
 763         return ret;
 764 }
 765
 766 /*
 767  * Flush the mapping to the persistent domain within the byte range of [start,
 768  * end]. This is required by data integrity operations to ensure file data is
 769  * on persistent storage prior to completion of the operation.
 770  */
 771 int dax_writeback_mapping_range(struct address_space *mapping,
 772                 struct block_device *bdev, struct writeback_control *wbc)
 773 {
 774         struct inode *inode = mapping->host;
 775         pgoff_t start_index, end_index;
 776         pgoff_t indices[PAGEVEC_SIZE];
 777         struct pagevec pvec;
 778         bool done = false;
 779         int i, ret = 0;
 780
 781         if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
 782                 return -EIO;
 783
 784         if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
 785                 return 0;
 786
 787         start_index = wbc->range_start >> PAGE_SHIFT;
 788         end_index = wbc->range_end >> PAGE_SHIFT;
 789
 790         tag_pages_for_writeback(mapping, start_index, end_index);
 791
 792         pagevec_init(&pvec, 0);
 793         while (!done) {
 794                 pvec.nr = find_get_entries_tag(mapping, start_index,
 795                                 PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE,
 796                                 pvec.pages, indices);
 797
 798                 if (pvec.nr == 0)
 799                         break;
 800
 801                 for (i = 0; i < pvec.nr; i++) {
 802                         if (indices[i] > end_index) {
 803                                 done = true;
 804                                 break;
 805                         }
 806
 807                         ret = dax_writeback_one(bdev, mapping, indices[i],
 808                                         pvec.pages[i]);
 809                         if (ret < 0)
 810                                 return ret;
 811                 }
 812         }
 813         return 0;
 814 }
 815 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
 816
 817 static int dax_insert_mapping(struct address_space *mapping,
 818                 struct block_device *bdev, sector_t sector, size_t size,
 819                 void **entryp, struct vm_area_struct *vma, struct vm_fault *vmf)
 820 {
 821         unsigned long vaddr = vmf->address;
 822         struct blk_dax_ctl dax = {
 823                 .sector = sector,
 824                 .size = size,
 825         };
 826         void *ret;
 827         void *entry = *entryp;
 828
 829         if (dax_map_atomic(bdev, &dax) < 0)
 830                 return PTR_ERR(dax.addr);
 831         dax_unmap_atomic(bdev, &dax);
 832
 833         ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector, 0);
 834         if (IS_ERR(ret))
 835                 return PTR_ERR(ret);
 836         *entryp = ret;
 837
 838         return vm_insert_mixed(vma, vaddr, dax.pfn);
 839 }
 840
 841 /**
 842  * dax_pfn_mkwrite - handle first write to DAX page
 843  * @vma: The virtual memory area where the fault occurred
 844  * @vmf: The description of the fault
 845  */
 846 int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 847 {
 848         struct file *file = vma->vm_file;
 849         struct address_space *mapping = file->f_mapping;
 850         void *entry, **slot;
 851         pgoff_t index = vmf->pgoff;
 852
 853         spin_lock_irq(&mapping->tree_lock);
 854         entry = get_unlocked_mapping_entry(mapping, index, &slot);
 855         if (!entry || !radix_tree_exceptional_entry(entry)) {
 856                 if (entry)
 857                         put_unlocked_mapping_entry(mapping, index, entry);
 858                 spin_unlock_irq(&mapping->tree_lock);
 859                 return VM_FAULT_NOPAGE;
 860         }
 861         radix_tree_tag_set(&mapping->page_tree, index, PAGECACHE_TAG_DIRTY);
 862         entry = lock_slot(mapping, slot);
 863         spin_unlock_irq(&mapping->tree_lock);
 864         /*
 865          * If we race with somebody updating the PTE and finish_mkwrite_fault()
 866          * fails, we don't care. We need to return VM_FAULT_NOPAGE and retry
 867          * the fault in either case.
 868          */
 869         finish_mkwrite_fault(vmf);
 870         put_locked_mapping_entry(mapping, index, entry);
 871         return VM_FAULT_NOPAGE;
 872 }
 873 EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
 874
 875 static bool dax_range_is_aligned(struct block_device *bdev,
 876                                  unsigned int offset, unsigned int length)
 877 {
 878         unsigned short sector_size = bdev_logical_block_size(bdev);
 879
 880         if (!IS_ALIGNED(offset, sector_size))
 881                 return false;
 882         if (!IS_ALIGNED(length, sector_size))
 883                 return false;
 884
 885         return true;
 886 }
 887
 888 int __dax_zero_page_range(struct block_device *bdev, sector_t sector,
 889                 unsigned int offset, unsigned int length)
 890 {
 891         struct blk_dax_ctl dax = {
 892                 .sector         = sector,
 893                 .size           = PAGE_SIZE,
 894         };
 895
 896         if (dax_range_is_aligned(bdev, offset, length)) {
 897                 sector_t start_sector = dax.sector + (offset >> 9);
 898
 899                 return blkdev_issue_zeroout(bdev, start_sector,
 900                                 length >> 9, GFP_NOFS, true);
 901         } else {
 902                 if (dax_map_atomic(bdev, &dax) < 0)
 903                         return PTR_ERR(dax.addr);
 904                 clear_pmem(dax.addr + offset, length);
 905                 dax_unmap_atomic(bdev, &dax);
 906         }
 907         return 0;
 908 }
 909 EXPORT_SYMBOL_GPL(__dax_zero_page_range);
 910
 911 #ifdef CONFIG_FS_IOMAP
 912 static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
 913 {
 914         return iomap->blkno + (((pos & PAGE_MASK) - iomap->offset) >> 9);
 915 }
 916
 917 static loff_t
 918 dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 919                 struct iomap *iomap)
 920 {
 921         struct iov_iter *iter = data;
 922         loff_t end = pos + length, done = 0;
 923         ssize_t ret = 0;
 924
 925         if (iov_iter_rw(iter) == READ) {
 926                 end = min(end, i_size_read(inode));
 927                 if (pos >= end)
 928                         return 0;
 929
 930                 if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
 931                         return iov_iter_zero(min(length, end - pos), iter);
 932         }
 933
 934         if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED))
 935                 return -EIO;
 936
 937         while (pos < end) {
 938                 unsigned offset = pos & (PAGE_SIZE - 1);
 939                 struct blk_dax_ctl dax = { 0 };
 940                 ssize_t map_len;
 941
 942                 dax.sector = dax_iomap_sector(iomap, pos);
 943                 dax.size = (length + offset + PAGE_SIZE - 1) & PAGE_MASK;
 944                 map_len = dax_map_atomic(iomap->bdev, &dax);
 945                 if (map_len < 0) {
 946                         ret = map_len;
 947                         break;
 948                 }
 949
 950                 dax.addr += offset;
 951                 map_len -= offset;
 952                 if (map_len > end - pos)
 953                         map_len = end - pos;
 954
 955                 if (iov_iter_rw(iter) == WRITE)
 956                         map_len = copy_from_iter_pmem(dax.addr, map_len, iter);
 957                 else
 958                         map_len = copy_to_iter(dax.addr, map_len, iter);
 959                 dax_unmap_atomic(iomap->bdev, &dax);
 960                 if (map_len <= 0) {
 961                         ret = map_len ? map_len : -EFAULT;
 962                         break;
 963                 }
 964
 965                 pos += map_len;
 966                 length -= map_len;
 967                 done += map_len;
 968         }
 969
 970         return done ? done : ret;
 971 }
 972
 973 /**
 974  * dax_iomap_rw - Perform I/O to a DAX file
 975  * @iocb:       The control block for this I/O
 976  * @iter:       The addresses to do I/O from or to
 977  * @ops:        iomap ops passed from the file system
 978  *
 979  * This function performs read and write operations to directly mapped
 980  * persistent memory.  The callers needs to take care of read/write exclusion
 981  * and evicting any page cache pages in the region under I/O.
 982  */
 983 ssize_t
 984 dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 985                 struct iomap_ops *ops)
 986 {
 987         struct address_space *mapping = iocb->ki_filp->f_mapping;
 988         struct inode *inode = mapping->host;
 989         loff_t pos = iocb->ki_pos, ret = 0, done = 0;
 990         unsigned flags = 0;
 991
 992         if (iov_iter_rw(iter) == WRITE)
 993                 flags |= IOMAP_WRITE;
 994
 995         /*
 996          * Yes, even DAX files can have page cache attached to them:  A zeroed
 997          * page is inserted into the pagecache when we have to serve a write
 998          * fault on a hole.  It should never be dirtied and can simply be
 999          * dropped from the pagecache once we get real data for the page.
1000          *
1001          * XXX: This is racy against mmap, and there's nothing we can do about
1002          * it. We'll eventually need to shift this down even further so that
1003          * we can check if we allocated blocks over a hole first.
1004          */
1005         if (mapping->nrpages) {
1006                 ret = invalidate_inode_pages2_range(mapping,
1007                                 pos >> PAGE_SHIFT,
1008                                 (pos + iov_iter_count(iter) - 1) >> PAGE_SHIFT);
1009                 WARN_ON_ONCE(ret);
1010         }
1011
1012         while (iov_iter_count(iter)) {
1013                 ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
1014                                 iter, dax_iomap_actor);
1015                 if (ret <= 0)
1016                         break;
1017                 pos += ret;
1018                 done += ret;
1019         }
1020
1021         iocb->ki_pos += done;
1022         return done ? done : ret;
1023 }
1024 EXPORT_SYMBOL_GPL(dax_iomap_rw);
1025
1026 /**
1027  * dax_iomap_fault - handle a page fault on a DAX file
1028  * @vma: The virtual memory area where the fault occurred
1029  * @vmf: The description of the fault
1030  * @ops: iomap ops passed from the file system
1031  *
1032  * When a page fault occurs, filesystems may call this helper in their fault
1033  * or mkwrite handler for DAX files. Assumes the caller has done all the
1034  * necessary locking for the page fault to proceed successfully.
1035  */
1036 int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
1037                         struct iomap_ops *ops)
1038 {
1039         struct address_space *mapping = vma->vm_file->f_mapping;
1040         struct inode *inode = mapping->host;
1041         unsigned long vaddr = vmf->address;
1042         loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
1043         sector_t sector;
1044         struct iomap iomap = { 0 };
1045         unsigned flags = IOMAP_FAULT;
1046         int error, major = 0;
1047         int vmf_ret = 0;
1048         void *entry;
1049
1050         /*
1051          * Check whether offset isn't beyond end of file now. Caller is supposed
1052          * to hold locks serializing us with truncate / punch hole so this is
1053          * a reliable test.
1054          */
1055         if (pos >= i_size_read(inode))
1056                 return VM_FAULT_SIGBUS;
1057
1058         entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
1059         if (IS_ERR(entry)) {
1060                 error = PTR_ERR(entry);
1061                 goto out;
1062         }
1063
1064         if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page)
1065                 flags |= IOMAP_WRITE;
1066
1067         /*
1068          * Note that we don't bother to use iomap_apply here: DAX required
1069          * the file system block size to be equal the page size, which means
1070          * that we never have to deal with more than a single extent here.
1071          */
1072         error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap);
1073         if (error)
1074                 goto unlock_entry;
1075         if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
1076                 error = -EIO;           /* fs corruption? */
1077                 goto finish_iomap;
1078         }
1079
1080         sector = dax_iomap_sector(&iomap, pos);
1081
1082         if (vmf->cow_page) {
1083                 switch (iomap.type) {
1084                 case IOMAP_HOLE:
1085                 case IOMAP_UNWRITTEN:
1086                         clear_user_highpage(vmf->cow_page, vaddr);
1087                         break;
1088                 case IOMAP_MAPPED:
1089                         error = copy_user_dax(iomap.bdev, sector, PAGE_SIZE,
1090                                         vmf->cow_page, vaddr);
1091                         break;
1092                 default:
1093                         WARN_ON_ONCE(1);
1094                         error = -EIO;
1095                         break;
1096                 }
1097
1098                 if (error)
1099                         goto finish_iomap;
1100
1101                 __SetPageUptodate(vmf->cow_page);
1102                 vmf_ret = finish_fault(vmf);
1103                 if (!vmf_ret)
1104                         vmf_ret = VM_FAULT_DONE_COW;
1105                 goto finish_iomap;
1106         }
1107
1108         switch (iomap.type) {
1109         case IOMAP_MAPPED:
1110                 if (iomap.flags & IOMAP_F_NEW) {
1111                         count_vm_event(PGMAJFAULT);
1112                         mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1113                         major = VM_FAULT_MAJOR;
1114                 }
1115                 error = dax_insert_mapping(mapping, iomap.bdev, sector,
1116                                 PAGE_SIZE, &entry, vma, vmf);
1117                 break;
1118         case IOMAP_UNWRITTEN:
1119         case IOMAP_HOLE:
1120                 if (!(vmf->flags & FAULT_FLAG_WRITE)) {
1121                         vmf_ret = dax_load_hole(mapping, entry, vmf);
1122                         break;
1123                 }
1124                 /*FALLTHRU*/
1125         default:
1126                 WARN_ON_ONCE(1);
1127                 error = -EIO;
1128                 break;
1129         }
1130
1131  finish_iomap:
1132         if (ops->iomap_end) {
1133                 if (error || (vmf_ret & VM_FAULT_ERROR)) {
1134                         /* keep previous error */
1135                         ops->iomap_end(inode, pos, PAGE_SIZE, 0, flags,
1136                                         &iomap);
1137                 } else {
1138                         error = ops->iomap_end(inode, pos, PAGE_SIZE,
1139                                         PAGE_SIZE, flags, &iomap);
1140                 }
1141         }
1142  unlock_entry:
1143         if (vmf_ret != VM_FAULT_LOCKED || error)
1144                 put_locked_mapping_entry(mapping, vmf->pgoff, entry);
1145  out:
1146         if (error == -ENOMEM)
1147                 return VM_FAULT_OOM | major;
1148         /* -EBUSY is fine, somebody else faulted on the same PTE */
1149         if (error < 0 && error != -EBUSY)
1150                 return VM_FAULT_SIGBUS | major;
1151         if (vmf_ret) {
1152                 WARN_ON_ONCE(error); /* -EBUSY from ops->iomap_end? */
1153                 return vmf_ret;
1154         }
1155         return VM_FAULT_NOPAGE | major;
1156 }
1157 EXPORT_SYMBOL_GPL(dax_iomap_fault);
1158
1159 #ifdef CONFIG_FS_DAX_PMD
1160 /*
1161  * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
1162  * more often than one might expect in the below functions.
1163  */
1164 #define PG_PMD_COLOUR   ((PMD_SIZE >> PAGE_SHIFT) - 1)
1165
1166 static int dax_pmd_insert_mapping(struct vm_area_struct *vma, pmd_t *pmd,
1167                 struct vm_fault *vmf, unsigned long address,
1168                 struct iomap *iomap, loff_t pos, bool write, void **entryp)
1169 {
1170         struct address_space *mapping = vma->vm_file->f_mapping;
1171         struct block_device *bdev = iomap->bdev;
1172         struct blk_dax_ctl dax = {
1173                 .sector = dax_iomap_sector(iomap, pos),
1174                 .size = PMD_SIZE,
1175         };
1176         long length = dax_map_atomic(bdev, &dax);
1177         void *ret;
1178
1179         if (length < 0) /* dax_map_atomic() failed */
1180                 return VM_FAULT_FALLBACK;
1181         if (length < PMD_SIZE)
1182                 goto unmap_fallback;
1183         if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR)
1184                 goto unmap_fallback;
1185         if (!pfn_t_devmap(dax.pfn))
1186                 goto unmap_fallback;
1187
1188         dax_unmap_atomic(bdev, &dax);
1189
1190         ret = dax_insert_mapping_entry(mapping, vmf, *entryp, dax.sector,
1191                         RADIX_DAX_PMD);
1192         if (IS_ERR(ret))
1193                 return VM_FAULT_FALLBACK;
1194         *entryp = ret;
1195
1196         return vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write);
1197
1198  unmap_fallback:
1199         dax_unmap_atomic(bdev, &dax);
1200         return VM_FAULT_FALLBACK;
1201 }
1202
1203 static int dax_pmd_load_hole(struct vm_area_struct *vma, pmd_t *pmd,
1204                 struct vm_fault *vmf, unsigned long address,
1205                 struct iomap *iomap, void **entryp)
1206 {
1207         struct address_space *mapping = vma->vm_file->f_mapping;
1208         unsigned long pmd_addr = address & PMD_MASK;
1209         struct page *zero_page;
1210         spinlock_t *ptl;
1211         pmd_t pmd_entry;
1212         void *ret;
1213
1214         zero_page = mm_get_huge_zero_page(vma->vm_mm);
1215
1216         if (unlikely(!zero_page))
1217                 return VM_FAULT_FALLBACK;
1218
1219         ret = dax_insert_mapping_entry(mapping, vmf, *entryp, 0,
1220                         RADIX_DAX_PMD | RADIX_DAX_HZP);
1221         if (IS_ERR(ret))
1222                 return VM_FAULT_FALLBACK;
1223         *entryp = ret;
1224
1225         ptl = pmd_lock(vma->vm_mm, pmd);
1226         if (!pmd_none(*pmd)) {
1227                 spin_unlock(ptl);
1228                 return VM_FAULT_FALLBACK;
1229         }
1230
1231         pmd_entry = mk_pmd(zero_page, vma->vm_page_prot);
1232         pmd_entry = pmd_mkhuge(pmd_entry);
1233         set_pmd_at(vma->vm_mm, pmd_addr, pmd, pmd_entry);
1234         spin_unlock(ptl);
1235         return VM_FAULT_NOPAGE;
1236 }
1237
1238 int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
1239                 pmd_t *pmd, unsigned int flags, struct iomap_ops *ops)
1240 {
1241         struct address_space *mapping = vma->vm_file->f_mapping;
1242         unsigned long pmd_addr = address & PMD_MASK;
1243         bool write = flags & FAULT_FLAG_WRITE;
1244         unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT;
1245         struct inode *inode = mapping->host;
1246         int result = VM_FAULT_FALLBACK;
1247         struct iomap iomap = { 0 };
1248         pgoff_t max_pgoff, pgoff;
1249         struct vm_fault vmf;
1250         void *entry;
1251         loff_t pos;
1252         int error;
1253
1254         /* Fall back to PTEs if we're going to COW */
1255         if (write && !(vma->vm_flags & VM_SHARED))
1256                 goto fallback;
1257
1258         /* If the PMD would extend outside the VMA */
1259         if (pmd_addr < vma->vm_start)
1260                 goto fallback;
1261         if ((pmd_addr + PMD_SIZE) > vma->vm_end)
1262                 goto fallback;
1263
1264         /*
1265          * Check whether offset isn't beyond end of file now. Caller is
1266          * supposed to hold locks serializing us with truncate / punch hole so
1267          * this is a reliable test.
1268          */
1269         pgoff = linear_page_index(vma, pmd_addr);
1270         max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
1271
1272         if (pgoff > max_pgoff)
1273                 return VM_FAULT_SIGBUS;
1274
1275         /* If the PMD would extend beyond the file size */
1276         if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
1277                 goto fallback;
1278
1279         /*
1280          * grab_mapping_entry() will make sure we get a 2M empty entry, a DAX
1281          * PMD or a HZP entry.  If it can't (because a 4k page is already in
1282          * the tree, for instance), it will return -EEXIST and we just fall
1283          * back to 4k entries.
1284          */
1285         entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
1286         if (IS_ERR(entry))
1287                 goto fallback;
1288
1289         /*
1290          * Note that we don't use iomap_apply here.  We aren't doing I/O, only
1291          * setting up a mapping, so really we're using iomap_begin() as a way
1292          * to look up our filesystem block.
1293          */
1294         pos = (loff_t)pgoff << PAGE_SHIFT;
1295         error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
1296         if (error)
1297                 goto unlock_entry;
1298         if (iomap.offset + iomap.length < pos + PMD_SIZE)
1299                 goto finish_iomap;
1300
1301         vmf.pgoff = pgoff;
1302         vmf.flags = flags;
1303         vmf.gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
1304
1305         switch (iomap.type) {
1306         case IOMAP_MAPPED:
1307                 result = dax_pmd_insert_mapping(vma, pmd, &vmf, address,
1308                                 &iomap, pos, write, &entry);
1309                 break;
1310         case IOMAP_UNWRITTEN:
1311         case IOMAP_HOLE:
1312                 if (WARN_ON_ONCE(write))
1313                         goto finish_iomap;
1314                 result = dax_pmd_load_hole(vma, pmd, &vmf, address, &iomap,
1315                                 &entry);
1316                 break;
1317         default:
1318                 WARN_ON_ONCE(1);
1319                 break;
1320         }
1321
1322  finish_iomap:
1323         if (ops->iomap_end) {
1324                 if (result == VM_FAULT_FALLBACK) {
1325                         ops->iomap_end(inode, pos, PMD_SIZE, 0, iomap_flags,
1326                                         &iomap);
1327                 } else {
1328                         error = ops->iomap_end(inode, pos, PMD_SIZE, PMD_SIZE,
1329                                         iomap_flags, &iomap);
1330                         if (error)
1331                                 result = VM_FAULT_FALLBACK;
1332                 }
1333         }
1334  unlock_entry:
1335         put_locked_mapping_entry(mapping, pgoff, entry);
1336  fallback:
1337         if (result == VM_FAULT_FALLBACK) {
1338                 split_huge_pmd(vma, pmd, address);
1339                 count_vm_event(THP_FAULT_FALLBACK);
1340         }
1341         return result;
1342 }
1343 EXPORT_SYMBOL_GPL(dax_iomap_pmd_fault);
1344 #endif /* CONFIG_FS_DAX_PMD */
1345 #endif /* CONFIG_FS_IOMAP */