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
  35 #define RADIX_DAX_MASK  0xf
  36 #define RADIX_DAX_SHIFT 4
  37 #define RADIX_DAX_PTE  (0x4 | RADIX_TREE_EXCEPTIONAL_ENTRY)
  38 #define RADIX_DAX_PMD  (0x8 | RADIX_TREE_EXCEPTIONAL_ENTRY)
  39 #define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_MASK)
  40 #define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
  41 #define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
  42                 RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE)))
  43
  44 static long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax)
  45 {
  46         struct request_queue *q = bdev->bd_queue;
  47         long rc = -EIO;
  48
  49         dax->addr = (void __pmem *) ERR_PTR(-EIO);
  50         if (blk_queue_enter(q, true) != 0)
  51                 return rc;
  52
  53         rc = bdev_direct_access(bdev, dax);
  54         if (rc < 0) {
  55                 dax->addr = (void __pmem *) ERR_PTR(rc);
  56                 blk_queue_exit(q);
  57                 return rc;
  58         }
  59         return rc;
  60 }
  61
  62 static void dax_unmap_atomic(struct block_device *bdev,
  63                 const struct blk_dax_ctl *dax)
  64 {
  65         if (IS_ERR(dax->addr))
  66                 return;
  67         blk_queue_exit(bdev->bd_queue);
  68 }
  69
  70 struct page *read_dax_sector(struct block_device *bdev, sector_t n)
  71 {
  72         struct page *page = alloc_pages(GFP_KERNEL, 0);
  73         struct blk_dax_ctl dax = {
  74                 .size = PAGE_SIZE,
  75                 .sector = n & ~((((int) PAGE_SIZE) / 512) - 1),
  76         };
  77         long rc;
  78
  79         if (!page)
  80                 return ERR_PTR(-ENOMEM);
  81
  82         rc = dax_map_atomic(bdev, &dax);
  83         if (rc < 0)
  84                 return ERR_PTR(rc);
  85         memcpy_from_pmem(page_address(page), dax.addr, PAGE_SIZE);
  86         dax_unmap_atomic(bdev, &dax);
  87         return page;
  88 }
  89
  90 /*
  91  * dax_clear_sectors() is called from within transaction context from XFS,
  92  * and hence this means the stack from this point must follow GFP_NOFS
  93  * semantics for all operations.
  94  */
  95 int dax_clear_sectors(struct block_device *bdev, sector_t _sector, long _size)
  96 {
  97         struct blk_dax_ctl dax = {
  98                 .sector = _sector,
  99                 .size = _size,
 100         };
 101
 102         might_sleep();
 103         do {
 104                 long count, sz;
 105
 106                 count = dax_map_atomic(bdev, &dax);
 107                 if (count < 0)
 108                         return count;
 109                 sz = min_t(long, count, SZ_128K);
 110                 clear_pmem(dax.addr, sz);
 111                 dax.size -= sz;
 112                 dax.sector += sz / 512;
 113                 dax_unmap_atomic(bdev, &dax);
 114                 cond_resched();
 115         } while (dax.size);
 116
 117         wmb_pmem();
 118         return 0;
 119 }
 120 EXPORT_SYMBOL_GPL(dax_clear_sectors);
 121
 122 /* the clear_pmem() calls are ordered by a wmb_pmem() in the caller */
 123 static void dax_new_buf(void __pmem *addr, unsigned size, unsigned first,
 124                 loff_t pos, loff_t end)
 125 {
 126         loff_t final = end - pos + first; /* The final byte of the buffer */
 127
 128         if (first > 0)
 129                 clear_pmem(addr, first);
 130         if (final < size)
 131                 clear_pmem(addr + final, size - final);
 132 }
 133
 134 static bool buffer_written(struct buffer_head *bh)
 135 {
 136         return buffer_mapped(bh) && !buffer_unwritten(bh);
 137 }
 138
 139 /*
 140  * When ext4 encounters a hole, it returns without modifying the buffer_head
 141  * which means that we can't trust b_size.  To cope with this, we set b_state
 142  * to 0 before calling get_block and, if any bit is set, we know we can trust
 143  * b_size.  Unfortunate, really, since ext4 knows precisely how long a hole is
 144  * and would save us time calling get_block repeatedly.
 145  */
 146 static bool buffer_size_valid(struct buffer_head *bh)
 147 {
 148         return bh->b_state != 0;
 149 }
 150
 151
 152 static sector_t to_sector(const struct buffer_head *bh,
 153                 const struct inode *inode)
 154 {
 155         sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9);
 156
 157         return sector;
 158 }
 159
 160 static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
 161                       loff_t start, loff_t end, get_block_t get_block,
 162                       struct buffer_head *bh)
 163 {
 164         loff_t pos = start, max = start, bh_max = start;
 165         bool hole = false, need_wmb = false;
 166         struct block_device *bdev = NULL;
 167         int rw = iov_iter_rw(iter), rc;
 168         long map_len = 0;
 169         struct blk_dax_ctl dax = {
 170                 .addr = (void __pmem *) ERR_PTR(-EIO),
 171         };
 172
 173         if (rw == READ)
 174                 end = min(end, i_size_read(inode));
 175
 176         while (pos < end) {
 177                 size_t len;
 178                 if (pos == max) {
 179                         unsigned blkbits = inode->i_blkbits;
 180                         long page = pos >> PAGE_SHIFT;
 181                         sector_t block = page << (PAGE_SHIFT - blkbits);
 182                         unsigned first = pos - (block << blkbits);
 183                         long size;
 184
 185                         if (pos == bh_max) {
 186                                 bh->b_size = PAGE_ALIGN(end - pos);
 187                                 bh->b_state = 0;
 188                                 rc = get_block(inode, block, bh, rw == WRITE);
 189                                 if (rc)
 190                                         break;
 191                                 if (!buffer_size_valid(bh))
 192                                         bh->b_size = 1 << blkbits;
 193                                 bh_max = pos - first + bh->b_size;
 194                                 bdev = bh->b_bdev;
 195                         } else {
 196                                 unsigned done = bh->b_size -
 197                                                 (bh_max - (pos - first));
 198                                 bh->b_blocknr += done >> blkbits;
 199                                 bh->b_size -= done;
 200                         }
 201
 202                         hole = rw == READ && !buffer_written(bh);
 203                         if (hole) {
 204                                 size = bh->b_size - first;
 205                         } else {
 206                                 dax_unmap_atomic(bdev, &dax);
 207                                 dax.sector = to_sector(bh, inode);
 208                                 dax.size = bh->b_size;
 209                                 map_len = dax_map_atomic(bdev, &dax);
 210                                 if (map_len < 0) {
 211                                         rc = map_len;
 212                                         break;
 213                                 }
 214                                 if (buffer_unwritten(bh) || buffer_new(bh)) {
 215                                         dax_new_buf(dax.addr, map_len, first,
 216                                                         pos, end);
 217                                         need_wmb = true;
 218                                 }
 219                                 dax.addr += first;
 220                                 size = map_len - first;
 221                         }
 222                         max = min(pos + size, end);
 223                 }
 224
 225                 if (iov_iter_rw(iter) == WRITE) {
 226                         len = copy_from_iter_pmem(dax.addr, max - pos, iter);
 227                         need_wmb = true;
 228                 } else if (!hole)
 229                         len = copy_to_iter((void __force *) dax.addr, max - pos,
 230                                         iter);
 231                 else
 232                         len = iov_iter_zero(max - pos, iter);
 233
 234                 if (!len) {
 235                         rc = -EFAULT;
 236                         break;
 237                 }
 238
 239                 pos += len;
 240                 if (!IS_ERR(dax.addr))
 241                         dax.addr += len;
 242         }
 243
 244         if (need_wmb)
 245                 wmb_pmem();
 246         dax_unmap_atomic(bdev, &dax);
 247
 248         return (pos == start) ? rc : pos - start;
 249 }
 250
 251 /**
 252  * dax_do_io - Perform I/O to a DAX file
 253  * @iocb: The control block for this I/O
 254  * @inode: The file which the I/O is directed at
 255  * @iter: The addresses to do I/O from or to
 256  * @pos: The file offset where the I/O starts
 257  * @get_block: The filesystem method used to translate file offsets to blocks
 258  * @end_io: A filesystem callback for I/O completion
 259  * @flags: See below
 260  *
 261  * This function uses the same locking scheme as do_blockdev_direct_IO:
 262  * If @flags has DIO_LOCKING set, we assume that the i_mutex is held by the
 263  * caller for writes.  For reads, we take and release the i_mutex ourselves.
 264  * If DIO_LOCKING is not set, the filesystem takes care of its own locking.
 265  * As with do_blockdev_direct_IO(), we increment i_dio_count while the I/O
 266  * is in progress.
 267  */
 268 ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode,
 269                   struct iov_iter *iter, loff_t pos, get_block_t get_block,
 270                   dio_iodone_t end_io, int flags)
 271 {
 272         struct buffer_head bh;
 273         ssize_t retval = -EINVAL;
 274         loff_t end = pos + iov_iter_count(iter);
 275
 276         memset(&bh, 0, sizeof(bh));
 277         bh.b_bdev = inode->i_sb->s_bdev;
 278
 279         if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ) {
 280                 struct address_space *mapping = inode->i_mapping;
 281                 inode_lock(inode);
 282                 retval = filemap_write_and_wait_range(mapping, pos, end - 1);
 283                 if (retval) {
 284                         inode_unlock(inode);
 285                         goto out;
 286                 }
 287         }
 288
 289         /* Protects against truncate */
 290         if (!(flags & DIO_SKIP_DIO_COUNT))
 291                 inode_dio_begin(inode);
 292
 293         retval = dax_io(inode, iter, pos, end, get_block, &bh);
 294
 295         if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ)
 296                 inode_unlock(inode);
 297
 298         if (end_io) {
 299                 int err;
 300
 301                 err = end_io(iocb, pos, retval, bh.b_private);
 302                 if (err)
 303                         retval = err;
 304         }
 305
 306         if (!(flags & DIO_SKIP_DIO_COUNT))
 307                 inode_dio_end(inode);
 308  out:
 309         return retval;
 310 }
 311 EXPORT_SYMBOL_GPL(dax_do_io);
 312
 313 /*
 314  * The user has performed a load from a hole in the file.  Allocating
 315  * a new page in the file would cause excessive storage usage for
 316  * workloads with sparse files.  We allocate a page cache page instead.
 317  * We'll kick it out of the page cache if it's ever written to,
 318  * otherwise it will simply fall out of the page cache under memory
 319  * pressure without ever having been dirtied.
 320  */
 321 static int dax_load_hole(struct address_space *mapping, struct page *page,
 322                                                         struct vm_fault *vmf)
 323 {
 324         unsigned long size;
 325         struct inode *inode = mapping->host;
 326         if (!page)
 327                 page = find_or_create_page(mapping, vmf->pgoff,
 328                                                 GFP_KERNEL | __GFP_ZERO);
 329         if (!page)
 330                 return VM_FAULT_OOM;
 331         /* Recheck i_size under page lock to avoid truncate race */
 332         size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
 333         if (vmf->pgoff >= size) {
 334                 unlock_page(page);
 335                 put_page(page);
 336                 return VM_FAULT_SIGBUS;
 337         }
 338
 339         vmf->page = page;
 340         return VM_FAULT_LOCKED;
 341 }
 342
 343 static int copy_user_bh(struct page *to, struct inode *inode,
 344                 struct buffer_head *bh, unsigned long vaddr)
 345 {
 346         struct blk_dax_ctl dax = {
 347                 .sector = to_sector(bh, inode),
 348                 .size = bh->b_size,
 349         };
 350         struct block_device *bdev = bh->b_bdev;
 351         void *vto;
 352
 353         if (dax_map_atomic(bdev, &dax) < 0)
 354                 return PTR_ERR(dax.addr);
 355         vto = kmap_atomic(to);
 356         copy_user_page(vto, (void __force *)dax.addr, vaddr, to);
 357         kunmap_atomic(vto);
 358         dax_unmap_atomic(bdev, &dax);
 359         return 0;
 360 }
 361
 362 #define NO_SECTOR -1
 363 #define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT))
 364
 365 static int dax_radix_entry(struct address_space *mapping, pgoff_t index,
 366                 sector_t sector, bool pmd_entry, bool dirty)
 367 {
 368         struct radix_tree_root *page_tree = &mapping->page_tree;
 369         pgoff_t pmd_index = DAX_PMD_INDEX(index);
 370         int type, error = 0;
 371         void *entry;
 372
 373         WARN_ON_ONCE(pmd_entry && !dirty);
 374         if (dirty)
 375                 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
 376
 377         spin_lock_irq(&mapping->tree_lock);
 378
 379         entry = radix_tree_lookup(page_tree, pmd_index);
 380         if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD) {
 381                 index = pmd_index;
 382                 goto dirty;
 383         }
 384
 385         entry = radix_tree_lookup(page_tree, index);
 386         if (entry) {
 387                 type = RADIX_DAX_TYPE(entry);
 388                 if (WARN_ON_ONCE(type != RADIX_DAX_PTE &&
 389                                         type != RADIX_DAX_PMD)) {
 390                         error = -EIO;
 391                         goto unlock;
 392                 }
 393
 394                 if (!pmd_entry || type == RADIX_DAX_PMD)
 395                         goto dirty;
 396
 397                 /*
 398                  * We only insert dirty PMD entries into the radix tree.  This
 399                  * means we don't need to worry about removing a dirty PTE
 400                  * entry and inserting a clean PMD entry, thus reducing the
 401                  * range we would flush with a follow-up fsync/msync call.
 402                  */
 403                 radix_tree_delete(&mapping->page_tree, index);
 404                 mapping->nrexceptional--;
 405         }
 406
 407         if (sector == NO_SECTOR) {
 408                 /*
 409                  * This can happen during correct operation if our pfn_mkwrite
 410                  * fault raced against a hole punch operation.  If this
 411                  * happens the pte that was hole punched will have been
 412                  * unmapped and the radix tree entry will have been removed by
 413                  * the time we are called, but the call will still happen.  We
 414                  * will return all the way up to wp_pfn_shared(), where the
 415                  * pte_same() check will fail, eventually causing page fault
 416                  * to be retried by the CPU.
 417                  */
 418                 goto unlock;
 419         }
 420
 421         error = radix_tree_insert(page_tree, index,
 422                         RADIX_DAX_ENTRY(sector, pmd_entry));
 423         if (error)
 424                 goto unlock;
 425
 426         mapping->nrexceptional++;
 427  dirty:
 428         if (dirty)
 429                 radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);
 430  unlock:
 431         spin_unlock_irq(&mapping->tree_lock);
 432         return error;
 433 }
 434
 435 static int dax_writeback_one(struct block_device *bdev,
 436                 struct address_space *mapping, pgoff_t index, void *entry)
 437 {
 438         struct radix_tree_root *page_tree = &mapping->page_tree;
 439         int type = RADIX_DAX_TYPE(entry);
 440         struct radix_tree_node *node;
 441         struct blk_dax_ctl dax;
 442         void **slot;
 443         int ret = 0;
 444
 445         spin_lock_irq(&mapping->tree_lock);
 446         /*
 447          * Regular page slots are stabilized by the page lock even
 448          * without the tree itself locked.  These unlocked entries
 449          * need verification under the tree lock.
 450          */
 451         if (!__radix_tree_lookup(page_tree, index, &node, &slot))
 452                 goto unlock;
 453         if (*slot != entry)
 454                 goto unlock;
 455
 456         /* another fsync thread may have already written back this entry */
 457         if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
 458                 goto unlock;
 459
 460         if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) {
 461                 ret = -EIO;
 462                 goto unlock;
 463         }
 464
 465         dax.sector = RADIX_DAX_SECTOR(entry);
 466         dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE);
 467         spin_unlock_irq(&mapping->tree_lock);
 468
 469         /*
 470          * We cannot hold tree_lock while calling dax_map_atomic() because it
 471          * eventually calls cond_resched().
 472          */
 473         ret = dax_map_atomic(bdev, &dax);
 474         if (ret < 0)
 475                 return ret;
 476
 477         if (WARN_ON_ONCE(ret < dax.size)) {
 478                 ret = -EIO;
 479                 goto unmap;
 480         }
 481
 482         wb_cache_pmem(dax.addr, dax.size);
 483
 484         spin_lock_irq(&mapping->tree_lock);
 485         radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE);
 486         spin_unlock_irq(&mapping->tree_lock);
 487  unmap:
 488         dax_unmap_atomic(bdev, &dax);
 489         return ret;
 490
 491  unlock:
 492         spin_unlock_irq(&mapping->tree_lock);
 493         return ret;
 494 }
 495
 496 /*
 497  * Flush the mapping to the persistent domain within the byte range of [start,
 498  * end]. This is required by data integrity operations to ensure file data is
 499  * on persistent storage prior to completion of the operation.
 500  */
 501 int dax_writeback_mapping_range(struct address_space *mapping,
 502                 struct block_device *bdev, struct writeback_control *wbc)
 503 {
 504         struct inode *inode = mapping->host;
 505         pgoff_t start_index, end_index, pmd_index;
 506         pgoff_t indices[PAGEVEC_SIZE];
 507         struct pagevec pvec;
 508         bool done = false;
 509         int i, ret = 0;
 510         void *entry;
 511
 512         if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
 513                 return -EIO;
 514
 515         if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
 516                 return 0;
 517
 518         start_index = wbc->range_start >> PAGE_SHIFT;
 519         end_index = wbc->range_end >> PAGE_SHIFT;
 520         pmd_index = DAX_PMD_INDEX(start_index);
 521
 522         rcu_read_lock();
 523         entry = radix_tree_lookup(&mapping->page_tree, pmd_index);
 524         rcu_read_unlock();
 525
 526         /* see if the start of our range is covered by a PMD entry */
 527         if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
 528                 start_index = pmd_index;
 529
 530         tag_pages_for_writeback(mapping, start_index, end_index);
 531
 532         pagevec_init(&pvec, 0);
 533         while (!done) {
 534                 pvec.nr = find_get_entries_tag(mapping, start_index,
 535                                 PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE,
 536                                 pvec.pages, indices);
 537
 538                 if (pvec.nr == 0)
 539                         break;
 540
 541                 for (i = 0; i < pvec.nr; i++) {
 542                         if (indices[i] > end_index) {
 543                                 done = true;
 544                                 break;
 545                         }
 546
 547                         ret = dax_writeback_one(bdev, mapping, indices[i],
 548                                         pvec.pages[i]);
 549                         if (ret < 0)
 550                                 return ret;
 551                 }
 552         }
 553         wmb_pmem();
 554         return 0;
 555 }
 556 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
 557
 558 static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
 559                         struct vm_area_struct *vma, struct vm_fault *vmf)
 560 {
 561         unsigned long vaddr = (unsigned long)vmf->virtual_address;
 562         struct address_space *mapping = inode->i_mapping;
 563         struct block_device *bdev = bh->b_bdev;
 564         struct blk_dax_ctl dax = {
 565                 .sector = to_sector(bh, inode),
 566                 .size = bh->b_size,
 567         };
 568         pgoff_t size;
 569         int error;
 570
 571         i_mmap_lock_read(mapping);
 572
 573         /*
 574          * Check truncate didn't happen while we were allocating a block.
 575          * If it did, this block may or may not be still allocated to the
 576          * file.  We can't tell the filesystem to free it because we can't
 577          * take i_mutex here.  In the worst case, the file still has blocks
 578          * allocated past the end of the file.
 579          */
 580         size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
 581         if (unlikely(vmf->pgoff >= size)) {
 582                 error = -EIO;
 583                 goto out;
 584         }
 585
 586         if (dax_map_atomic(bdev, &dax) < 0) {
 587                 error = PTR_ERR(dax.addr);
 588                 goto out;
 589         }
 590
 591         if (buffer_unwritten(bh) || buffer_new(bh)) {
 592                 clear_pmem(dax.addr, PAGE_SIZE);
 593                 wmb_pmem();
 594         }
 595         dax_unmap_atomic(bdev, &dax);
 596
 597         error = dax_radix_entry(mapping, vmf->pgoff, dax.sector, false,
 598                         vmf->flags & FAULT_FLAG_WRITE);
 599         if (error)
 600                 goto out;
 601
 602         error = vm_insert_mixed(vma, vaddr, dax.pfn);
 603
 604  out:
 605         i_mmap_unlock_read(mapping);
 606
 607         return error;
 608 }
 609
 610 /**
 611  * __dax_fault - handle a page fault on a DAX file
 612  * @vma: The virtual memory area where the fault occurred
 613  * @vmf: The description of the fault
 614  * @get_block: The filesystem method used to translate file offsets to blocks
 615  *
 616  * When a page fault occurs, filesystems may call this helper in their
 617  * fault handler for DAX files. __dax_fault() assumes the caller has done all
 618  * the necessary locking for the page fault to proceed successfully.
 619  */
 620 int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 621                         get_block_t get_block)
 622 {
 623         struct file *file = vma->vm_file;
 624         struct address_space *mapping = file->f_mapping;
 625         struct inode *inode = mapping->host;
 626         struct page *page;
 627         struct buffer_head bh;
 628         unsigned long vaddr = (unsigned long)vmf->virtual_address;
 629         unsigned blkbits = inode->i_blkbits;
 630         sector_t block;
 631         pgoff_t size;
 632         int error;
 633         int major = 0;
 634
 635         size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
 636         if (vmf->pgoff >= size)
 637                 return VM_FAULT_SIGBUS;
 638
 639         memset(&bh, 0, sizeof(bh));
 640         block = (sector_t)vmf->pgoff << (PAGE_SHIFT - blkbits);
 641         bh.b_bdev = inode->i_sb->s_bdev;
 642         bh.b_size = PAGE_SIZE;
 643
 644  repeat:
 645         page = find_get_page(mapping, vmf->pgoff);
 646         if (page) {
 647                 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
 648                         put_page(page);
 649                         return VM_FAULT_RETRY;
 650                 }
 651                 if (unlikely(page->mapping != mapping)) {
 652                         unlock_page(page);
 653                         put_page(page);
 654                         goto repeat;
 655                 }
 656                 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
 657                 if (unlikely(vmf->pgoff >= size)) {
 658                         /*
 659                          * We have a struct page covering a hole in the file
 660                          * from a read fault and we've raced with a truncate
 661                          */
 662                         error = -EIO;
 663                         goto unlock_page;
 664                 }
 665         }
 666
 667         error = get_block(inode, block, &bh, 0);
 668         if (!error && (bh.b_size < PAGE_SIZE))
 669                 error = -EIO;           /* fs corruption? */
 670         if (error)
 671                 goto unlock_page;
 672
 673         if (!buffer_mapped(&bh) && !vmf->cow_page) {
 674                 if (vmf->flags & FAULT_FLAG_WRITE) {
 675                         error = get_block(inode, block, &bh, 1);
 676                         count_vm_event(PGMAJFAULT);
 677                         mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
 678                         major = VM_FAULT_MAJOR;
 679                         if (!error && (bh.b_size < PAGE_SIZE))
 680                                 error = -EIO;
 681                         if (error)
 682                                 goto unlock_page;
 683                 } else {
 684                         return dax_load_hole(mapping, page, vmf);
 685                 }
 686         }
 687
 688         if (vmf->cow_page) {
 689                 struct page *new_page = vmf->cow_page;
 690                 if (buffer_written(&bh))
 691                         error = copy_user_bh(new_page, inode, &bh, vaddr);
 692                 else
 693                         clear_user_highpage(new_page, vaddr);
 694                 if (error)
 695                         goto unlock_page;
 696                 vmf->page = page;
 697                 if (!page) {
 698                         i_mmap_lock_read(mapping);
 699                         /* Check we didn't race with truncate */
 700                         size = (i_size_read(inode) + PAGE_SIZE - 1) >>
 701                                                                 PAGE_SHIFT;
 702                         if (vmf->pgoff >= size) {
 703                                 i_mmap_unlock_read(mapping);
 704                                 error = -EIO;
 705                                 goto out;
 706                         }
 707                 }
 708                 return VM_FAULT_LOCKED;
 709         }
 710
 711         /* Check we didn't race with a read fault installing a new page */
 712         if (!page && major)
 713                 page = find_lock_page(mapping, vmf->pgoff);
 714
 715         if (page) {
 716                 unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
 717                                                         PAGE_SIZE, 0);
 718                 delete_from_page_cache(page);
 719                 unlock_page(page);
 720                 put_page(page);
 721                 page = NULL;
 722         }
 723
 724         /* Filesystem should not return unwritten buffers to us! */
 725         WARN_ON_ONCE(buffer_unwritten(&bh));
 726         error = dax_insert_mapping(inode, &bh, vma, vmf);
 727
 728  out:
 729         if (error == -ENOMEM)
 730                 return VM_FAULT_OOM | major;
 731         /* -EBUSY is fine, somebody else faulted on the same PTE */
 732         if ((error < 0) && (error != -EBUSY))
 733                 return VM_FAULT_SIGBUS | major;
 734         return VM_FAULT_NOPAGE | major;
 735
 736  unlock_page:
 737         if (page) {
 738                 unlock_page(page);
 739                 put_page(page);
 740         }
 741         goto out;
 742 }
 743 EXPORT_SYMBOL(__dax_fault);
 744
 745 /**
 746  * dax_fault - handle a page fault on a DAX file
 747  * @vma: The virtual memory area where the fault occurred
 748  * @vmf: The description of the fault
 749  * @get_block: The filesystem method used to translate file offsets to blocks
 750  *
 751  * When a page fault occurs, filesystems may call this helper in their
 752  * fault handler for DAX files.
 753  */
 754 int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 755               get_block_t get_block)
 756 {
 757         int result;
 758         struct super_block *sb = file_inode(vma->vm_file)->i_sb;
 759
 760         if (vmf->flags & FAULT_FLAG_WRITE) {
 761                 sb_start_pagefault(sb);
 762                 file_update_time(vma->vm_file);
 763         }
 764         result = __dax_fault(vma, vmf, get_block);
 765         if (vmf->flags & FAULT_FLAG_WRITE)
 766                 sb_end_pagefault(sb);
 767
 768         return result;
 769 }
 770 EXPORT_SYMBOL_GPL(dax_fault);
 771
 772 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 773 /*
 774  * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
 775  * more often than one might expect in the below function.
 776  */
 777 #define PG_PMD_COLOUR   ((PMD_SIZE >> PAGE_SHIFT) - 1)
 778
 779 static void __dax_dbg(struct buffer_head *bh, unsigned long address,
 780                 const char *reason, const char *fn)
 781 {
 782         if (bh) {
 783                 char bname[BDEVNAME_SIZE];
 784                 bdevname(bh->b_bdev, bname);
 785                 pr_debug("%s: %s addr: %lx dev %s state %lx start %lld "
 786                         "length %zd fallback: %s\n", fn, current->comm,
 787                         address, bname, bh->b_state, (u64)bh->b_blocknr,
 788                         bh->b_size, reason);
 789         } else {
 790                 pr_debug("%s: %s addr: %lx fallback: %s\n", fn,
 791                         current->comm, address, reason);
 792         }
 793 }
 794
 795 #define dax_pmd_dbg(bh, address, reason)        __dax_dbg(bh, address, reason, "dax_pmd")
 796
 797 int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 798                 pmd_t *pmd, unsigned int flags, get_block_t get_block)
 799 {
 800         struct file *file = vma->vm_file;
 801         struct address_space *mapping = file->f_mapping;
 802         struct inode *inode = mapping->host;
 803         struct buffer_head bh;
 804         unsigned blkbits = inode->i_blkbits;
 805         unsigned long pmd_addr = address & PMD_MASK;
 806         bool write = flags & FAULT_FLAG_WRITE;
 807         struct block_device *bdev;
 808         pgoff_t size, pgoff;
 809         sector_t block;
 810         int error, result = 0;
 811         bool alloc = false;
 812
 813         /* dax pmd mappings require pfn_t_devmap() */
 814         if (!IS_ENABLED(CONFIG_FS_DAX_PMD))
 815                 return VM_FAULT_FALLBACK;
 816
 817         /* Fall back to PTEs if we're going to COW */
 818         if (write && !(vma->vm_flags & VM_SHARED)) {
 819                 split_huge_pmd(vma, pmd, address);
 820                 dax_pmd_dbg(NULL, address, "cow write");
 821                 return VM_FAULT_FALLBACK;
 822         }
 823         /* If the PMD would extend outside the VMA */
 824         if (pmd_addr < vma->vm_start) {
 825                 dax_pmd_dbg(NULL, address, "vma start unaligned");
 826                 return VM_FAULT_FALLBACK;
 827         }
 828         if ((pmd_addr + PMD_SIZE) > vma->vm_end) {
 829                 dax_pmd_dbg(NULL, address, "vma end unaligned");
 830                 return VM_FAULT_FALLBACK;
 831         }
 832
 833         pgoff = linear_page_index(vma, pmd_addr);
 834         size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
 835         if (pgoff >= size)
 836                 return VM_FAULT_SIGBUS;
 837         /* If the PMD would cover blocks out of the file */
 838         if ((pgoff | PG_PMD_COLOUR) >= size) {
 839                 dax_pmd_dbg(NULL, address,
 840                                 "offset + huge page size > file size");
 841                 return VM_FAULT_FALLBACK;
 842         }
 843
 844         memset(&bh, 0, sizeof(bh));
 845         bh.b_bdev = inode->i_sb->s_bdev;
 846         block = (sector_t)pgoff << (PAGE_SHIFT - blkbits);
 847
 848         bh.b_size = PMD_SIZE;
 849
 850         if (get_block(inode, block, &bh, 0) != 0)
 851                 return VM_FAULT_SIGBUS;
 852
 853         if (!buffer_mapped(&bh) && write) {
 854                 if (get_block(inode, block, &bh, 1) != 0)
 855                         return VM_FAULT_SIGBUS;
 856                 alloc = true;
 857                 WARN_ON_ONCE(buffer_unwritten(&bh));
 858         }
 859
 860         bdev = bh.b_bdev;
 861
 862         /*
 863          * If the filesystem isn't willing to tell us the length of a hole,
 864          * just fall back to PTEs.  Calling get_block 512 times in a loop
 865          * would be silly.
 866          */
 867         if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) {
 868                 dax_pmd_dbg(&bh, address, "allocated block too small");
 869                 return VM_FAULT_FALLBACK;
 870         }
 871
 872         /*
 873          * If we allocated new storage, make sure no process has any
 874          * zero pages covering this hole
 875          */
 876         if (alloc) {
 877                 loff_t lstart = pgoff << PAGE_SHIFT;
 878                 loff_t lend = lstart + PMD_SIZE - 1; /* inclusive */
 879
 880                 truncate_pagecache_range(inode, lstart, lend);
 881         }
 882
 883         i_mmap_lock_read(mapping);
 884
 885         /*
 886          * If a truncate happened while we were allocating blocks, we may
 887          * leave blocks allocated to the file that are beyond EOF.  We can't
 888          * take i_mutex here, so just leave them hanging; they'll be freed
 889          * when the file is deleted.
 890          */
 891         size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
 892         if (pgoff >= size) {
 893                 result = VM_FAULT_SIGBUS;
 894                 goto out;
 895         }
 896         if ((pgoff | PG_PMD_COLOUR) >= size) {
 897                 dax_pmd_dbg(&bh, address,
 898                                 "offset + huge page size > file size");
 899                 goto fallback;
 900         }
 901
 902         if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {
 903                 spinlock_t *ptl;
 904                 pmd_t entry;
 905                 struct page *zero_page = get_huge_zero_page();
 906
 907                 if (unlikely(!zero_page)) {
 908                         dax_pmd_dbg(&bh, address, "no zero page");
 909                         goto fallback;
 910                 }
 911
 912                 ptl = pmd_lock(vma->vm_mm, pmd);
 913                 if (!pmd_none(*pmd)) {
 914                         spin_unlock(ptl);
 915                         dax_pmd_dbg(&bh, address, "pmd already present");
 916                         goto fallback;
 917                 }
 918
 919                 dev_dbg(part_to_dev(bdev->bd_part),
 920                                 "%s: %s addr: %lx pfn: <zero> sect: %llx\n",
 921                                 __func__, current->comm, address,
 922                                 (unsigned long long) to_sector(&bh, inode));
 923
 924                 entry = mk_pmd(zero_page, vma->vm_page_prot);
 925                 entry = pmd_mkhuge(entry);
 926                 set_pmd_at(vma->vm_mm, pmd_addr, pmd, entry);
 927                 result = VM_FAULT_NOPAGE;
 928                 spin_unlock(ptl);
 929         } else {
 930                 struct blk_dax_ctl dax = {
 931                         .sector = to_sector(&bh, inode),
 932                         .size = PMD_SIZE,
 933                 };
 934                 long length = dax_map_atomic(bdev, &dax);
 935
 936                 if (length < 0) {
 937                         result = VM_FAULT_SIGBUS;
 938                         goto out;
 939                 }
 940                 if (length < PMD_SIZE) {
 941                         dax_pmd_dbg(&bh, address, "dax-length too small");
 942                         dax_unmap_atomic(bdev, &dax);
 943                         goto fallback;
 944                 }
 945                 if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR) {
 946                         dax_pmd_dbg(&bh, address, "pfn unaligned");
 947                         dax_unmap_atomic(bdev, &dax);
 948                         goto fallback;
 949                 }
 950
 951                 if (!pfn_t_devmap(dax.pfn)) {
 952                         dax_unmap_atomic(bdev, &dax);
 953                         dax_pmd_dbg(&bh, address, "pfn not in memmap");
 954                         goto fallback;
 955                 }
 956
 957                 if (buffer_unwritten(&bh) || buffer_new(&bh)) {
 958                         clear_pmem(dax.addr, PMD_SIZE);
 959                         wmb_pmem();
 960                         count_vm_event(PGMAJFAULT);
 961                         mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
 962                         result |= VM_FAULT_MAJOR;
 963                 }
 964                 dax_unmap_atomic(bdev, &dax);
 965
 966                 /*
 967                  * For PTE faults we insert a radix tree entry for reads, and
 968                  * leave it clean.  Then on the first write we dirty the radix
 969                  * tree entry via the dax_pfn_mkwrite() path.  This sequence
 970                  * allows the dax_pfn_mkwrite() call to be simpler and avoid a
 971                  * call into get_block() to translate the pgoff to a sector in
 972                  * order to be able to create a new radix tree entry.
 973                  *
 974                  * The PMD path doesn't have an equivalent to
 975                  * dax_pfn_mkwrite(), though, so for a read followed by a
 976                  * write we traverse all the way through __dax_pmd_fault()
 977                  * twice.  This means we can just skip inserting a radix tree
 978                  * entry completely on the initial read and just wait until
 979                  * the write to insert a dirty entry.
 980                  */
 981                 if (write) {
 982                         error = dax_radix_entry(mapping, pgoff, dax.sector,
 983                                         true, true);
 984                         if (error) {
 985                                 dax_pmd_dbg(&bh, address,
 986                                                 "PMD radix insertion failed");
 987                                 goto fallback;
 988                         }
 989                 }
 990
 991                 dev_dbg(part_to_dev(bdev->bd_part),
 992                                 "%s: %s addr: %lx pfn: %lx sect: %llx\n",
 993                                 __func__, current->comm, address,
 994                                 pfn_t_to_pfn(dax.pfn),
 995                                 (unsigned long long) dax.sector);
 996                 result |= vmf_insert_pfn_pmd(vma, address, pmd,
 997                                 dax.pfn, write);
 998         }
 999
1000  out:
1001         i_mmap_unlock_read(mapping);
1002
1003         return result;
1004
1005  fallback:
1006         count_vm_event(THP_FAULT_FALLBACK);
1007         result = VM_FAULT_FALLBACK;
1008         goto out;
1009 }
1010 EXPORT_SYMBOL_GPL(__dax_pmd_fault);
1011
1012 /**
1013  * dax_pmd_fault - handle a PMD fault on a DAX file
1014  * @vma: The virtual memory area where the fault occurred
1015  * @vmf: The description of the fault
1016  * @get_block: The filesystem method used to translate file offsets to blocks
1017  *
1018  * When a page fault occurs, filesystems may call this helper in their
1019  * pmd_fault handler for DAX files.
1020  */
1021 int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
1022                         pmd_t *pmd, unsigned int flags, get_block_t get_block)
1023 {
1024         int result;
1025         struct super_block *sb = file_inode(vma->vm_file)->i_sb;
1026
1027         if (flags & FAULT_FLAG_WRITE) {
1028                 sb_start_pagefault(sb);
1029                 file_update_time(vma->vm_file);
1030         }
1031         result = __dax_pmd_fault(vma, address, pmd, flags, get_block);
1032         if (flags & FAULT_FLAG_WRITE)
1033                 sb_end_pagefault(sb);
1034
1035         return result;
1036 }
1037 EXPORT_SYMBOL_GPL(dax_pmd_fault);
1038 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
1039
1040 /**
1041  * dax_pfn_mkwrite - handle first write to DAX page
1042  * @vma: The virtual memory area where the fault occurred
1043  * @vmf: The description of the fault
1044  */
1045 int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
1046 {
1047         struct file *file = vma->vm_file;
1048         int error;
1049
1050         /*
1051          * We pass NO_SECTOR to dax_radix_entry() because we expect that a
1052          * RADIX_DAX_PTE entry already exists in the radix tree from a
1053          * previous call to __dax_fault().  We just want to look up that PTE
1054          * entry using vmf->pgoff and make sure the dirty tag is set.  This
1055          * saves us from having to make a call to get_block() here to look
1056          * up the sector.
1057          */
1058         error = dax_radix_entry(file->f_mapping, vmf->pgoff, NO_SECTOR, false,
1059                         true);
1060
1061         if (error == -ENOMEM)
1062                 return VM_FAULT_OOM;
1063         if (error)
1064                 return VM_FAULT_SIGBUS;
1065         return VM_FAULT_NOPAGE;
1066 }
1067 EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
1068
1069 /**
1070  * dax_zero_page_range - zero a range within a page of a DAX file
1071  * @inode: The file being truncated
1072  * @from: The file offset that is being truncated to
1073  * @length: The number of bytes to zero
1074  * @get_block: The filesystem method used to translate file offsets to blocks
1075  *
1076  * This function can be called by a filesystem when it is zeroing part of a
1077  * page in a DAX file.  This is intended for hole-punch operations.  If
1078  * you are truncating a file, the helper function dax_truncate_page() may be
1079  * more convenient.
1080  *
1081  * We work in terms of PAGE_SIZE here for commonality with
1082  * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
1083  * took care of disposing of the unnecessary blocks.  Even if the filesystem
1084  * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
1085  * since the file might be mmapped.
1086  */
1087 int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
1088                                                         get_block_t get_block)
1089 {
1090         struct buffer_head bh;
1091         pgoff_t index = from >> PAGE_SHIFT;
1092         unsigned offset = from & (PAGE_SIZE-1);
1093         int err;
1094
1095         /* Block boundary? Nothing to do */
1096         if (!length)
1097                 return 0;
1098         BUG_ON((offset + length) > PAGE_SIZE);
1099
1100         memset(&bh, 0, sizeof(bh));
1101         bh.b_bdev = inode->i_sb->s_bdev;
1102         bh.b_size = PAGE_SIZE;
1103         err = get_block(inode, index, &bh, 0);
1104         if (err < 0)
1105                 return err;
1106         if (buffer_written(&bh)) {
1107                 struct block_device *bdev = bh.b_bdev;
1108                 struct blk_dax_ctl dax = {
1109                         .sector = to_sector(&bh, inode),
1110                         .size = PAGE_SIZE,
1111                 };
1112
1113                 if (dax_map_atomic(bdev, &dax) < 0)
1114                         return PTR_ERR(dax.addr);
1115                 clear_pmem(dax.addr + offset, length);
1116                 wmb_pmem();
1117                 dax_unmap_atomic(bdev, &dax);
1118         }
1119
1120         return 0;
1121 }
1122 EXPORT_SYMBOL_GPL(dax_zero_page_range);
1123
1124 /**
1125  * dax_truncate_page - handle a partial page being truncated in a DAX file
1126  * @inode: The file being truncated
1127  * @from: The file offset that is being truncated to
1128  * @get_block: The filesystem method used to translate file offsets to blocks
1129  *
1130  * Similar to block_truncate_page(), this function can be called by a
1131  * filesystem when it is truncating a DAX file to handle the partial page.
1132  *
1133  * We work in terms of PAGE_SIZE here for commonality with
1134  * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
1135  * took care of disposing of the unnecessary blocks.  Even if the filesystem
1136  * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
1137  * since the file might be mmapped.
1138  */
1139 int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
1140 {
1141         unsigned length = PAGE_ALIGN(from) - from;
1142         return dax_zero_page_range(inode, from, length, get_block);
1143 }
1144 EXPORT_SYMBOL_GPL(dax_truncate_page);