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 static long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax) 36 { 37 struct request_queue *q = bdev->bd_queue; 38 long rc = -EIO; 39 40 dax->addr = (void __pmem *) ERR_PTR(-EIO); 41 if (blk_queue_enter(q, true) != 0) 42 return rc; 43 44 rc = bdev_direct_access(bdev, dax); 45 if (rc < 0) { 46 dax->addr = (void __pmem *) ERR_PTR(rc); 47 blk_queue_exit(q); 48 return rc; 49 } 50 return rc; 51 } 52 53 static void dax_unmap_atomic(struct block_device *bdev, 54 const struct blk_dax_ctl *dax) 55 { 56 if (IS_ERR(dax->addr)) 57 return; 58 blk_queue_exit(bdev->bd_queue); 59 } 60 61 struct page *read_dax_sector(struct block_device *bdev, sector_t n) 62 { 63 struct page *page = alloc_pages(GFP_KERNEL, 0); 64 struct blk_dax_ctl dax = { 65 .size = PAGE_SIZE, 66 .sector = n & ~((((int) PAGE_SIZE) / 512) - 1), 67 }; 68 long rc; 69 70 if (!page) 71 return ERR_PTR(-ENOMEM); 72 73 rc = dax_map_atomic(bdev, &dax); 74 if (rc < 0) 75 return ERR_PTR(rc); 76 memcpy_from_pmem(page_address(page), dax.addr, PAGE_SIZE); 77 dax_unmap_atomic(bdev, &dax); 78 return page; 79 } 80 81 /* 82 * dax_clear_blocks() is called from within transaction context from XFS, 83 * and hence this means the stack from this point must follow GFP_NOFS 84 * semantics for all operations. 85 */ 86 int dax_clear_blocks(struct inode *inode, sector_t block, long _size) 87 { 88 struct block_device *bdev = inode->i_sb->s_bdev; 89 struct blk_dax_ctl dax = { 90 .sector = block << (inode->i_blkbits - 9), 91 .size = _size, 92 }; 93 94 might_sleep(); 95 do { 96 long count, sz; 97 98 count = dax_map_atomic(bdev, &dax); 99 if (count < 0) 100 return count; 101 sz = min_t(long, count, SZ_128K); 102 clear_pmem(dax.addr, sz); 103 dax.size -= sz; 104 dax.sector += sz / 512; 105 dax_unmap_atomic(bdev, &dax); 106 cond_resched(); 107 } while (dax.size); 108 109 wmb_pmem(); 110 return 0; 111 } 112 EXPORT_SYMBOL_GPL(dax_clear_blocks); 113 114 /* the clear_pmem() calls are ordered by a wmb_pmem() in the caller */ 115 static void dax_new_buf(void __pmem *addr, unsigned size, unsigned first, 116 loff_t pos, loff_t end) 117 { 118 loff_t final = end - pos + first; /* The final byte of the buffer */ 119 120 if (first > 0) 121 clear_pmem(addr, first); 122 if (final < size) 123 clear_pmem(addr + final, size - final); 124 } 125 126 static bool buffer_written(struct buffer_head *bh) 127 { 128 return buffer_mapped(bh) && !buffer_unwritten(bh); 129 } 130 131 /* 132 * When ext4 encounters a hole, it returns without modifying the buffer_head 133 * which means that we can't trust b_size. To cope with this, we set b_state 134 * to 0 before calling get_block and, if any bit is set, we know we can trust 135 * b_size. Unfortunate, really, since ext4 knows precisely how long a hole is 136 * and would save us time calling get_block repeatedly. 137 */ 138 static bool buffer_size_valid(struct buffer_head *bh) 139 { 140 return bh->b_state != 0; 141 } 142 143 144 static sector_t to_sector(const struct buffer_head *bh, 145 const struct inode *inode) 146 { 147 sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9); 148 149 return sector; 150 } 151 152 static ssize_t dax_io(struct inode *inode, struct iov_iter *iter, 153 loff_t start, loff_t end, get_block_t get_block, 154 struct buffer_head *bh) 155 { 156 loff_t pos = start, max = start, bh_max = start; 157 bool hole = false, need_wmb = false; 158 struct block_device *bdev = NULL; 159 int rw = iov_iter_rw(iter), rc; 160 long map_len = 0; 161 struct blk_dax_ctl dax = { 162 .addr = (void __pmem *) ERR_PTR(-EIO), 163 }; 164 165 if (rw == READ) 166 end = min(end, i_size_read(inode)); 167 168 while (pos < end) { 169 size_t len; 170 if (pos == max) { 171 unsigned blkbits = inode->i_blkbits; 172 long page = pos >> PAGE_SHIFT; 173 sector_t block = page << (PAGE_SHIFT - blkbits); 174 unsigned first = pos - (block << blkbits); 175 long size; 176 177 if (pos == bh_max) { 178 bh->b_size = PAGE_ALIGN(end - pos); 179 bh->b_state = 0; 180 rc = get_block(inode, block, bh, rw == WRITE); 181 if (rc) 182 break; 183 if (!buffer_size_valid(bh)) 184 bh->b_size = 1 << blkbits; 185 bh_max = pos - first + bh->b_size; 186 bdev = bh->b_bdev; 187 } else { 188 unsigned done = bh->b_size - 189 (bh_max - (pos - first)); 190 bh->b_blocknr += done >> blkbits; 191 bh->b_size -= done; 192 } 193 194 hole = rw == READ && !buffer_written(bh); 195 if (hole) { 196 size = bh->b_size - first; 197 } else { 198 dax_unmap_atomic(bdev, &dax); 199 dax.sector = to_sector(bh, inode); 200 dax.size = bh->b_size; 201 map_len = dax_map_atomic(bdev, &dax); 202 if (map_len < 0) { 203 rc = map_len; 204 break; 205 } 206 if (buffer_unwritten(bh) || buffer_new(bh)) { 207 dax_new_buf(dax.addr, map_len, first, 208 pos, end); 209 need_wmb = true; 210 } 211 dax.addr += first; 212 size = map_len - first; 213 } 214 max = min(pos + size, end); 215 } 216 217 if (iov_iter_rw(iter) == WRITE) { 218 len = copy_from_iter_pmem(dax.addr, max - pos, iter); 219 need_wmb = true; 220 } else if (!hole) 221 len = copy_to_iter((void __force *) dax.addr, max - pos, 222 iter); 223 else 224 len = iov_iter_zero(max - pos, iter); 225 226 if (!len) { 227 rc = -EFAULT; 228 break; 229 } 230 231 pos += len; 232 if (!IS_ERR(dax.addr)) 233 dax.addr += len; 234 } 235 236 if (need_wmb) 237 wmb_pmem(); 238 dax_unmap_atomic(bdev, &dax); 239 240 return (pos == start) ? rc : pos - start; 241 } 242 243 /** 244 * dax_do_io - Perform I/O to a DAX file 245 * @iocb: The control block for this I/O 246 * @inode: The file which the I/O is directed at 247 * @iter: The addresses to do I/O from or to 248 * @pos: The file offset where the I/O starts 249 * @get_block: The filesystem method used to translate file offsets to blocks 250 * @end_io: A filesystem callback for I/O completion 251 * @flags: See below 252 * 253 * This function uses the same locking scheme as do_blockdev_direct_IO: 254 * If @flags has DIO_LOCKING set, we assume that the i_mutex is held by the 255 * caller for writes. For reads, we take and release the i_mutex ourselves. 256 * If DIO_LOCKING is not set, the filesystem takes care of its own locking. 257 * As with do_blockdev_direct_IO(), we increment i_dio_count while the I/O 258 * is in progress. 259 */ 260 ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode, 261 struct iov_iter *iter, loff_t pos, get_block_t get_block, 262 dio_iodone_t end_io, int flags) 263 { 264 struct buffer_head bh; 265 ssize_t retval = -EINVAL; 266 loff_t end = pos + iov_iter_count(iter); 267 268 memset(&bh, 0, sizeof(bh)); 269 bh.b_bdev = inode->i_sb->s_bdev; 270 271 if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ) { 272 struct address_space *mapping = inode->i_mapping; 273 inode_lock(inode); 274 retval = filemap_write_and_wait_range(mapping, pos, end - 1); 275 if (retval) { 276 inode_unlock(inode); 277 goto out; 278 } 279 } 280 281 /* Protects against truncate */ 282 if (!(flags & DIO_SKIP_DIO_COUNT)) 283 inode_dio_begin(inode); 284 285 retval = dax_io(inode, iter, pos, end, get_block, &bh); 286 287 if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ) 288 inode_unlock(inode); 289 290 if ((retval > 0) && end_io) 291 end_io(iocb, pos, retval, bh.b_private); 292 293 if (!(flags & DIO_SKIP_DIO_COUNT)) 294 inode_dio_end(inode); 295 out: 296 return retval; 297 } 298 EXPORT_SYMBOL_GPL(dax_do_io); 299 300 /* 301 * The user has performed a load from a hole in the file. Allocating 302 * a new page in the file would cause excessive storage usage for 303 * workloads with sparse files. We allocate a page cache page instead. 304 * We'll kick it out of the page cache if it's ever written to, 305 * otherwise it will simply fall out of the page cache under memory 306 * pressure without ever having been dirtied. 307 */ 308 static int dax_load_hole(struct address_space *mapping, struct page *page, 309 struct vm_fault *vmf) 310 { 311 unsigned long size; 312 struct inode *inode = mapping->host; 313 if (!page) 314 page = find_or_create_page(mapping, vmf->pgoff, 315 GFP_KERNEL | __GFP_ZERO); 316 if (!page) 317 return VM_FAULT_OOM; 318 /* Recheck i_size under page lock to avoid truncate race */ 319 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; 320 if (vmf->pgoff >= size) { 321 unlock_page(page); 322 page_cache_release(page); 323 return VM_FAULT_SIGBUS; 324 } 325 326 vmf->page = page; 327 return VM_FAULT_LOCKED; 328 } 329 330 static int copy_user_bh(struct page *to, struct inode *inode, 331 struct buffer_head *bh, unsigned long vaddr) 332 { 333 struct blk_dax_ctl dax = { 334 .sector = to_sector(bh, inode), 335 .size = bh->b_size, 336 }; 337 struct block_device *bdev = bh->b_bdev; 338 void *vto; 339 340 if (dax_map_atomic(bdev, &dax) < 0) 341 return PTR_ERR(dax.addr); 342 vto = kmap_atomic(to); 343 copy_user_page(vto, (void __force *)dax.addr, vaddr, to); 344 kunmap_atomic(vto); 345 dax_unmap_atomic(bdev, &dax); 346 return 0; 347 } 348 349 #define NO_SECTOR -1 350 #define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_CACHE_SHIFT)) 351 352 static int dax_radix_entry(struct address_space *mapping, pgoff_t index, 353 sector_t sector, bool pmd_entry, bool dirty) 354 { 355 struct radix_tree_root *page_tree = &mapping->page_tree; 356 pgoff_t pmd_index = DAX_PMD_INDEX(index); 357 int type, error = 0; 358 void *entry; 359 360 WARN_ON_ONCE(pmd_entry && !dirty); 361 if (dirty) 362 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); 363 364 spin_lock_irq(&mapping->tree_lock); 365 366 entry = radix_tree_lookup(page_tree, pmd_index); 367 if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD) { 368 index = pmd_index; 369 goto dirty; 370 } 371 372 entry = radix_tree_lookup(page_tree, index); 373 if (entry) { 374 type = RADIX_DAX_TYPE(entry); 375 if (WARN_ON_ONCE(type != RADIX_DAX_PTE && 376 type != RADIX_DAX_PMD)) { 377 error = -EIO; 378 goto unlock; 379 } 380 381 if (!pmd_entry || type == RADIX_DAX_PMD) 382 goto dirty; 383 384 /* 385 * We only insert dirty PMD entries into the radix tree. This 386 * means we don't need to worry about removing a dirty PTE 387 * entry and inserting a clean PMD entry, thus reducing the 388 * range we would flush with a follow-up fsync/msync call. 389 */ 390 radix_tree_delete(&mapping->page_tree, index); 391 mapping->nrexceptional--; 392 } 393 394 if (sector == NO_SECTOR) { 395 /* 396 * This can happen during correct operation if our pfn_mkwrite 397 * fault raced against a hole punch operation. If this 398 * happens the pte that was hole punched will have been 399 * unmapped and the radix tree entry will have been removed by 400 * the time we are called, but the call will still happen. We 401 * will return all the way up to wp_pfn_shared(), where the 402 * pte_same() check will fail, eventually causing page fault 403 * to be retried by the CPU. 404 */ 405 goto unlock; 406 } 407 408 error = radix_tree_insert(page_tree, index, 409 RADIX_DAX_ENTRY(sector, pmd_entry)); 410 if (error) 411 goto unlock; 412 413 mapping->nrexceptional++; 414 dirty: 415 if (dirty) 416 radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY); 417 unlock: 418 spin_unlock_irq(&mapping->tree_lock); 419 return error; 420 } 421 422 static int dax_writeback_one(struct block_device *bdev, 423 struct address_space *mapping, pgoff_t index, void *entry) 424 { 425 struct radix_tree_root *page_tree = &mapping->page_tree; 426 int type = RADIX_DAX_TYPE(entry); 427 struct radix_tree_node *node; 428 struct blk_dax_ctl dax; 429 void **slot; 430 int ret = 0; 431 432 spin_lock_irq(&mapping->tree_lock); 433 /* 434 * Regular page slots are stabilized by the page lock even 435 * without the tree itself locked. These unlocked entries 436 * need verification under the tree lock. 437 */ 438 if (!__radix_tree_lookup(page_tree, index, &node, &slot)) 439 goto unlock; 440 if (*slot != entry) 441 goto unlock; 442 443 /* another fsync thread may have already written back this entry */ 444 if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE)) 445 goto unlock; 446 447 if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) { 448 ret = -EIO; 449 goto unlock; 450 } 451 452 dax.sector = RADIX_DAX_SECTOR(entry); 453 dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE); 454 spin_unlock_irq(&mapping->tree_lock); 455 456 /* 457 * We cannot hold tree_lock while calling dax_map_atomic() because it 458 * eventually calls cond_resched(). 459 */ 460 ret = dax_map_atomic(bdev, &dax); 461 if (ret < 0) 462 return ret; 463 464 if (WARN_ON_ONCE(ret < dax.size)) { 465 ret = -EIO; 466 goto unmap; 467 } 468 469 wb_cache_pmem(dax.addr, dax.size); 470 471 spin_lock_irq(&mapping->tree_lock); 472 radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE); 473 spin_unlock_irq(&mapping->tree_lock); 474 unmap: 475 dax_unmap_atomic(bdev, &dax); 476 return ret; 477 478 unlock: 479 spin_unlock_irq(&mapping->tree_lock); 480 return ret; 481 } 482 483 /* 484 * Flush the mapping to the persistent domain within the byte range of [start, 485 * end]. This is required by data integrity operations to ensure file data is 486 * on persistent storage prior to completion of the operation. 487 */ 488 int dax_writeback_mapping_range(struct address_space *mapping, loff_t start, 489 loff_t end) 490 { 491 struct inode *inode = mapping->host; 492 struct block_device *bdev = inode->i_sb->s_bdev; 493 pgoff_t start_index, end_index, pmd_index; 494 pgoff_t indices[PAGEVEC_SIZE]; 495 struct pagevec pvec; 496 bool done = false; 497 int i, ret = 0; 498 void *entry; 499 500 if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT)) 501 return -EIO; 502 503 start_index = start >> PAGE_CACHE_SHIFT; 504 end_index = end >> PAGE_CACHE_SHIFT; 505 pmd_index = DAX_PMD_INDEX(start_index); 506 507 rcu_read_lock(); 508 entry = radix_tree_lookup(&mapping->page_tree, pmd_index); 509 rcu_read_unlock(); 510 511 /* see if the start of our range is covered by a PMD entry */ 512 if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD) 513 start_index = pmd_index; 514 515 tag_pages_for_writeback(mapping, start_index, end_index); 516 517 pagevec_init(&pvec, 0); 518 while (!done) { 519 pvec.nr = find_get_entries_tag(mapping, start_index, 520 PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE, 521 pvec.pages, indices); 522 523 if (pvec.nr == 0) 524 break; 525 526 for (i = 0; i < pvec.nr; i++) { 527 if (indices[i] > end_index) { 528 done = true; 529 break; 530 } 531 532 ret = dax_writeback_one(bdev, mapping, indices[i], 533 pvec.pages[i]); 534 if (ret < 0) 535 return ret; 536 } 537 } 538 wmb_pmem(); 539 return 0; 540 } 541 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range); 542 543 static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh, 544 struct vm_area_struct *vma, struct vm_fault *vmf) 545 { 546 unsigned long vaddr = (unsigned long)vmf->virtual_address; 547 struct address_space *mapping = inode->i_mapping; 548 struct block_device *bdev = bh->b_bdev; 549 struct blk_dax_ctl dax = { 550 .sector = to_sector(bh, inode), 551 .size = bh->b_size, 552 }; 553 pgoff_t size; 554 int error; 555 556 i_mmap_lock_read(mapping); 557 558 /* 559 * Check truncate didn't happen while we were allocating a block. 560 * If it did, this block may or may not be still allocated to the 561 * file. We can't tell the filesystem to free it because we can't 562 * take i_mutex here. In the worst case, the file still has blocks 563 * allocated past the end of the file. 564 */ 565 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; 566 if (unlikely(vmf->pgoff >= size)) { 567 error = -EIO; 568 goto out; 569 } 570 571 if (dax_map_atomic(bdev, &dax) < 0) { 572 error = PTR_ERR(dax.addr); 573 goto out; 574 } 575 576 if (buffer_unwritten(bh) || buffer_new(bh)) { 577 clear_pmem(dax.addr, PAGE_SIZE); 578 wmb_pmem(); 579 } 580 dax_unmap_atomic(bdev, &dax); 581 582 error = dax_radix_entry(mapping, vmf->pgoff, dax.sector, false, 583 vmf->flags & FAULT_FLAG_WRITE); 584 if (error) 585 goto out; 586 587 error = vm_insert_mixed(vma, vaddr, dax.pfn); 588 589 out: 590 i_mmap_unlock_read(mapping); 591 592 return error; 593 } 594 595 /** 596 * __dax_fault - handle a page fault on a DAX file 597 * @vma: The virtual memory area where the fault occurred 598 * @vmf: The description of the fault 599 * @get_block: The filesystem method used to translate file offsets to blocks 600 * @complete_unwritten: The filesystem method used to convert unwritten blocks 601 * to written so the data written to them is exposed. This is required for 602 * required by write faults for filesystems that will return unwritten 603 * extent mappings from @get_block, but it is optional for reads as 604 * dax_insert_mapping() will always zero unwritten blocks. If the fs does 605 * not support unwritten extents, the it should pass NULL. 606 * 607 * When a page fault occurs, filesystems may call this helper in their 608 * fault handler for DAX files. __dax_fault() assumes the caller has done all 609 * the necessary locking for the page fault to proceed successfully. 610 */ 611 int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, 612 get_block_t get_block, dax_iodone_t complete_unwritten) 613 { 614 struct file *file = vma->vm_file; 615 struct address_space *mapping = file->f_mapping; 616 struct inode *inode = mapping->host; 617 struct page *page; 618 struct buffer_head bh; 619 unsigned long vaddr = (unsigned long)vmf->virtual_address; 620 unsigned blkbits = inode->i_blkbits; 621 sector_t block; 622 pgoff_t size; 623 int error; 624 int major = 0; 625 626 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; 627 if (vmf->pgoff >= size) 628 return VM_FAULT_SIGBUS; 629 630 memset(&bh, 0, sizeof(bh)); 631 block = (sector_t)vmf->pgoff << (PAGE_SHIFT - blkbits); 632 bh.b_bdev = inode->i_sb->s_bdev; 633 bh.b_size = PAGE_SIZE; 634 635 repeat: 636 page = find_get_page(mapping, vmf->pgoff); 637 if (page) { 638 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) { 639 page_cache_release(page); 640 return VM_FAULT_RETRY; 641 } 642 if (unlikely(page->mapping != mapping)) { 643 unlock_page(page); 644 page_cache_release(page); 645 goto repeat; 646 } 647 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; 648 if (unlikely(vmf->pgoff >= size)) { 649 /* 650 * We have a struct page covering a hole in the file 651 * from a read fault and we've raced with a truncate 652 */ 653 error = -EIO; 654 goto unlock_page; 655 } 656 } 657 658 error = get_block(inode, block, &bh, 0); 659 if (!error && (bh.b_size < PAGE_SIZE)) 660 error = -EIO; /* fs corruption? */ 661 if (error) 662 goto unlock_page; 663 664 if (!buffer_mapped(&bh) && !buffer_unwritten(&bh) && !vmf->cow_page) { 665 if (vmf->flags & FAULT_FLAG_WRITE) { 666 error = get_block(inode, block, &bh, 1); 667 count_vm_event(PGMAJFAULT); 668 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT); 669 major = VM_FAULT_MAJOR; 670 if (!error && (bh.b_size < PAGE_SIZE)) 671 error = -EIO; 672 if (error) 673 goto unlock_page; 674 } else { 675 return dax_load_hole(mapping, page, vmf); 676 } 677 } 678 679 if (vmf->cow_page) { 680 struct page *new_page = vmf->cow_page; 681 if (buffer_written(&bh)) 682 error = copy_user_bh(new_page, inode, &bh, vaddr); 683 else 684 clear_user_highpage(new_page, vaddr); 685 if (error) 686 goto unlock_page; 687 vmf->page = page; 688 if (!page) { 689 i_mmap_lock_read(mapping); 690 /* Check we didn't race with truncate */ 691 size = (i_size_read(inode) + PAGE_SIZE - 1) >> 692 PAGE_SHIFT; 693 if (vmf->pgoff >= size) { 694 i_mmap_unlock_read(mapping); 695 error = -EIO; 696 goto out; 697 } 698 } 699 return VM_FAULT_LOCKED; 700 } 701 702 /* Check we didn't race with a read fault installing a new page */ 703 if (!page && major) 704 page = find_lock_page(mapping, vmf->pgoff); 705 706 if (page) { 707 unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT, 708 PAGE_CACHE_SIZE, 0); 709 delete_from_page_cache(page); 710 unlock_page(page); 711 page_cache_release(page); 712 page = NULL; 713 } 714 715 /* 716 * If we successfully insert the new mapping over an unwritten extent, 717 * we need to ensure we convert the unwritten extent. If there is an 718 * error inserting the mapping, the filesystem needs to leave it as 719 * unwritten to prevent exposure of the stale underlying data to 720 * userspace, but we still need to call the completion function so 721 * the private resources on the mapping buffer can be released. We 722 * indicate what the callback should do via the uptodate variable, same 723 * as for normal BH based IO completions. 724 */ 725 error = dax_insert_mapping(inode, &bh, vma, vmf); 726 if (buffer_unwritten(&bh)) { 727 if (complete_unwritten) 728 complete_unwritten(&bh, !error); 729 else 730 WARN_ON_ONCE(!(vmf->flags & FAULT_FLAG_WRITE)); 731 } 732 733 out: 734 if (error == -ENOMEM) 735 return VM_FAULT_OOM | major; 736 /* -EBUSY is fine, somebody else faulted on the same PTE */ 737 if ((error < 0) && (error != -EBUSY)) 738 return VM_FAULT_SIGBUS | major; 739 return VM_FAULT_NOPAGE | major; 740 741 unlock_page: 742 if (page) { 743 unlock_page(page); 744 page_cache_release(page); 745 } 746 goto out; 747 } 748 EXPORT_SYMBOL(__dax_fault); 749 750 /** 751 * dax_fault - handle a page fault on a DAX file 752 * @vma: The virtual memory area where the fault occurred 753 * @vmf: The description of the fault 754 * @get_block: The filesystem method used to translate file offsets to blocks 755 * 756 * When a page fault occurs, filesystems may call this helper in their 757 * fault handler for DAX files. 758 */ 759 int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, 760 get_block_t get_block, dax_iodone_t complete_unwritten) 761 { 762 int result; 763 struct super_block *sb = file_inode(vma->vm_file)->i_sb; 764 765 if (vmf->flags & FAULT_FLAG_WRITE) { 766 sb_start_pagefault(sb); 767 file_update_time(vma->vm_file); 768 } 769 result = __dax_fault(vma, vmf, get_block, complete_unwritten); 770 if (vmf->flags & FAULT_FLAG_WRITE) 771 sb_end_pagefault(sb); 772 773 return result; 774 } 775 EXPORT_SYMBOL_GPL(dax_fault); 776 777 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 778 /* 779 * The 'colour' (ie low bits) within a PMD of a page offset. This comes up 780 * more often than one might expect in the below function. 781 */ 782 #define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1) 783 784 static void __dax_dbg(struct buffer_head *bh, unsigned long address, 785 const char *reason, const char *fn) 786 { 787 if (bh) { 788 char bname[BDEVNAME_SIZE]; 789 bdevname(bh->b_bdev, bname); 790 pr_debug("%s: %s addr: %lx dev %s state %lx start %lld " 791 "length %zd fallback: %s\n", fn, current->comm, 792 address, bname, bh->b_state, (u64)bh->b_blocknr, 793 bh->b_size, reason); 794 } else { 795 pr_debug("%s: %s addr: %lx fallback: %s\n", fn, 796 current->comm, address, reason); 797 } 798 } 799 800 #define dax_pmd_dbg(bh, address, reason) __dax_dbg(bh, address, reason, "dax_pmd") 801 802 int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, 803 pmd_t *pmd, unsigned int flags, get_block_t get_block, 804 dax_iodone_t complete_unwritten) 805 { 806 struct file *file = vma->vm_file; 807 struct address_space *mapping = file->f_mapping; 808 struct inode *inode = mapping->host; 809 struct buffer_head bh; 810 unsigned blkbits = inode->i_blkbits; 811 unsigned long pmd_addr = address & PMD_MASK; 812 bool write = flags & FAULT_FLAG_WRITE; 813 struct block_device *bdev; 814 pgoff_t size, pgoff; 815 sector_t block; 816 int error, result = 0; 817 bool alloc = false; 818 819 /* dax pmd mappings require pfn_t_devmap() */ 820 if (!IS_ENABLED(CONFIG_FS_DAX_PMD)) 821 return VM_FAULT_FALLBACK; 822 823 /* Fall back to PTEs if we're going to COW */ 824 if (write && !(vma->vm_flags & VM_SHARED)) { 825 split_huge_pmd(vma, pmd, address); 826 dax_pmd_dbg(NULL, address, "cow write"); 827 return VM_FAULT_FALLBACK; 828 } 829 /* If the PMD would extend outside the VMA */ 830 if (pmd_addr < vma->vm_start) { 831 dax_pmd_dbg(NULL, address, "vma start unaligned"); 832 return VM_FAULT_FALLBACK; 833 } 834 if ((pmd_addr + PMD_SIZE) > vma->vm_end) { 835 dax_pmd_dbg(NULL, address, "vma end unaligned"); 836 return VM_FAULT_FALLBACK; 837 } 838 839 pgoff = linear_page_index(vma, pmd_addr); 840 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; 841 if (pgoff >= size) 842 return VM_FAULT_SIGBUS; 843 /* If the PMD would cover blocks out of the file */ 844 if ((pgoff | PG_PMD_COLOUR) >= size) { 845 dax_pmd_dbg(NULL, address, 846 "offset + huge page size > file size"); 847 return VM_FAULT_FALLBACK; 848 } 849 850 memset(&bh, 0, sizeof(bh)); 851 bh.b_bdev = inode->i_sb->s_bdev; 852 block = (sector_t)pgoff << (PAGE_SHIFT - blkbits); 853 854 bh.b_size = PMD_SIZE; 855 856 if (get_block(inode, block, &bh, 0) != 0) 857 return VM_FAULT_SIGBUS; 858 859 if (!buffer_mapped(&bh) && write) { 860 if (get_block(inode, block, &bh, 1) != 0) 861 return VM_FAULT_SIGBUS; 862 alloc = true; 863 } 864 865 bdev = bh.b_bdev; 866 867 /* 868 * If the filesystem isn't willing to tell us the length of a hole, 869 * just fall back to PTEs. Calling get_block 512 times in a loop 870 * would be silly. 871 */ 872 if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) { 873 dax_pmd_dbg(&bh, address, "allocated block too small"); 874 return VM_FAULT_FALLBACK; 875 } 876 877 /* 878 * If we allocated new storage, make sure no process has any 879 * zero pages covering this hole 880 */ 881 if (alloc) { 882 loff_t lstart = pgoff << PAGE_SHIFT; 883 loff_t lend = lstart + PMD_SIZE - 1; /* inclusive */ 884 885 truncate_pagecache_range(inode, lstart, lend); 886 } 887 888 i_mmap_lock_read(mapping); 889 890 /* 891 * If a truncate happened while we were allocating blocks, we may 892 * leave blocks allocated to the file that are beyond EOF. We can't 893 * take i_mutex here, so just leave them hanging; they'll be freed 894 * when the file is deleted. 895 */ 896 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; 897 if (pgoff >= size) { 898 result = VM_FAULT_SIGBUS; 899 goto out; 900 } 901 if ((pgoff | PG_PMD_COLOUR) >= size) { 902 dax_pmd_dbg(&bh, address, 903 "offset + huge page size > file size"); 904 goto fallback; 905 } 906 907 if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) { 908 spinlock_t *ptl; 909 pmd_t entry; 910 struct page *zero_page = get_huge_zero_page(); 911 912 if (unlikely(!zero_page)) { 913 dax_pmd_dbg(&bh, address, "no zero page"); 914 goto fallback; 915 } 916 917 ptl = pmd_lock(vma->vm_mm, pmd); 918 if (!pmd_none(*pmd)) { 919 spin_unlock(ptl); 920 dax_pmd_dbg(&bh, address, "pmd already present"); 921 goto fallback; 922 } 923 924 dev_dbg(part_to_dev(bdev->bd_part), 925 "%s: %s addr: %lx pfn: <zero> sect: %llx\n", 926 __func__, current->comm, address, 927 (unsigned long long) to_sector(&bh, inode)); 928 929 entry = mk_pmd(zero_page, vma->vm_page_prot); 930 entry = pmd_mkhuge(entry); 931 set_pmd_at(vma->vm_mm, pmd_addr, pmd, entry); 932 result = VM_FAULT_NOPAGE; 933 spin_unlock(ptl); 934 } else { 935 struct blk_dax_ctl dax = { 936 .sector = to_sector(&bh, inode), 937 .size = PMD_SIZE, 938 }; 939 long length = dax_map_atomic(bdev, &dax); 940 941 if (length < 0) { 942 result = VM_FAULT_SIGBUS; 943 goto out; 944 } 945 if (length < PMD_SIZE) { 946 dax_pmd_dbg(&bh, address, "dax-length too small"); 947 dax_unmap_atomic(bdev, &dax); 948 goto fallback; 949 } 950 if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR) { 951 dax_pmd_dbg(&bh, address, "pfn unaligned"); 952 dax_unmap_atomic(bdev, &dax); 953 goto fallback; 954 } 955 956 if (!pfn_t_devmap(dax.pfn)) { 957 dax_unmap_atomic(bdev, &dax); 958 dax_pmd_dbg(&bh, address, "pfn not in memmap"); 959 goto fallback; 960 } 961 962 if (buffer_unwritten(&bh) || buffer_new(&bh)) { 963 clear_pmem(dax.addr, PMD_SIZE); 964 wmb_pmem(); 965 count_vm_event(PGMAJFAULT); 966 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT); 967 result |= VM_FAULT_MAJOR; 968 } 969 dax_unmap_atomic(bdev, &dax); 970 971 /* 972 * For PTE faults we insert a radix tree entry for reads, and 973 * leave it clean. Then on the first write we dirty the radix 974 * tree entry via the dax_pfn_mkwrite() path. This sequence 975 * allows the dax_pfn_mkwrite() call to be simpler and avoid a 976 * call into get_block() to translate the pgoff to a sector in 977 * order to be able to create a new radix tree entry. 978 * 979 * The PMD path doesn't have an equivalent to 980 * dax_pfn_mkwrite(), though, so for a read followed by a 981 * write we traverse all the way through __dax_pmd_fault() 982 * twice. This means we can just skip inserting a radix tree 983 * entry completely on the initial read and just wait until 984 * the write to insert a dirty entry. 985 */ 986 if (write) { 987 error = dax_radix_entry(mapping, pgoff, dax.sector, 988 true, true); 989 if (error) { 990 dax_pmd_dbg(&bh, address, 991 "PMD radix insertion failed"); 992 goto fallback; 993 } 994 } 995 996 dev_dbg(part_to_dev(bdev->bd_part), 997 "%s: %s addr: %lx pfn: %lx sect: %llx\n", 998 __func__, current->comm, address, 999 pfn_t_to_pfn(dax.pfn), 1000 (unsigned long long) dax.sector); 1001 result |= vmf_insert_pfn_pmd(vma, address, pmd, 1002 dax.pfn, write); 1003 } 1004 1005 out: 1006 i_mmap_unlock_read(mapping); 1007 1008 if (buffer_unwritten(&bh)) 1009 complete_unwritten(&bh, !(result & VM_FAULT_ERROR)); 1010 1011 return result; 1012 1013 fallback: 1014 count_vm_event(THP_FAULT_FALLBACK); 1015 result = VM_FAULT_FALLBACK; 1016 goto out; 1017 } 1018 EXPORT_SYMBOL_GPL(__dax_pmd_fault); 1019 1020 /** 1021 * dax_pmd_fault - handle a PMD fault on a DAX file 1022 * @vma: The virtual memory area where the fault occurred 1023 * @vmf: The description of the fault 1024 * @get_block: The filesystem method used to translate file offsets to blocks 1025 * 1026 * When a page fault occurs, filesystems may call this helper in their 1027 * pmd_fault handler for DAX files. 1028 */ 1029 int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, 1030 pmd_t *pmd, unsigned int flags, get_block_t get_block, 1031 dax_iodone_t complete_unwritten) 1032 { 1033 int result; 1034 struct super_block *sb = file_inode(vma->vm_file)->i_sb; 1035 1036 if (flags & FAULT_FLAG_WRITE) { 1037 sb_start_pagefault(sb); 1038 file_update_time(vma->vm_file); 1039 } 1040 result = __dax_pmd_fault(vma, address, pmd, flags, get_block, 1041 complete_unwritten); 1042 if (flags & FAULT_FLAG_WRITE) 1043 sb_end_pagefault(sb); 1044 1045 return result; 1046 } 1047 EXPORT_SYMBOL_GPL(dax_pmd_fault); 1048 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ 1049 1050 /** 1051 * dax_pfn_mkwrite - handle first write to DAX page 1052 * @vma: The virtual memory area where the fault occurred 1053 * @vmf: The description of the fault 1054 */ 1055 int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) 1056 { 1057 struct file *file = vma->vm_file; 1058 1059 /* 1060 * We pass NO_SECTOR to dax_radix_entry() because we expect that a 1061 * RADIX_DAX_PTE entry already exists in the radix tree from a 1062 * previous call to __dax_fault(). We just want to look up that PTE 1063 * entry using vmf->pgoff and make sure the dirty tag is set. This 1064 * saves us from having to make a call to get_block() here to look 1065 * up the sector. 1066 */ 1067 dax_radix_entry(file->f_mapping, vmf->pgoff, NO_SECTOR, false, true); 1068 return VM_FAULT_NOPAGE; 1069 } 1070 EXPORT_SYMBOL_GPL(dax_pfn_mkwrite); 1071 1072 /** 1073 * dax_zero_page_range - zero a range within a page of a DAX file 1074 * @inode: The file being truncated 1075 * @from: The file offset that is being truncated to 1076 * @length: The number of bytes to zero 1077 * @get_block: The filesystem method used to translate file offsets to blocks 1078 * 1079 * This function can be called by a filesystem when it is zeroing part of a 1080 * page in a DAX file. This is intended for hole-punch operations. If 1081 * you are truncating a file, the helper function dax_truncate_page() may be 1082 * more convenient. 1083 * 1084 * We work in terms of PAGE_CACHE_SIZE here for commonality with 1085 * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem 1086 * took care of disposing of the unnecessary blocks. Even if the filesystem 1087 * block size is smaller than PAGE_SIZE, we have to zero the rest of the page 1088 * since the file might be mmapped. 1089 */ 1090 int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length, 1091 get_block_t get_block) 1092 { 1093 struct buffer_head bh; 1094 pgoff_t index = from >> PAGE_CACHE_SHIFT; 1095 unsigned offset = from & (PAGE_CACHE_SIZE-1); 1096 int err; 1097 1098 /* Block boundary? Nothing to do */ 1099 if (!length) 1100 return 0; 1101 BUG_ON((offset + length) > PAGE_CACHE_SIZE); 1102 1103 memset(&bh, 0, sizeof(bh)); 1104 bh.b_bdev = inode->i_sb->s_bdev; 1105 bh.b_size = PAGE_CACHE_SIZE; 1106 err = get_block(inode, index, &bh, 0); 1107 if (err < 0) 1108 return err; 1109 if (buffer_written(&bh)) { 1110 struct block_device *bdev = bh.b_bdev; 1111 struct blk_dax_ctl dax = { 1112 .sector = to_sector(&bh, inode), 1113 .size = PAGE_CACHE_SIZE, 1114 }; 1115 1116 if (dax_map_atomic(bdev, &dax) < 0) 1117 return PTR_ERR(dax.addr); 1118 clear_pmem(dax.addr + offset, length); 1119 wmb_pmem(); 1120 dax_unmap_atomic(bdev, &dax); 1121 } 1122 1123 return 0; 1124 } 1125 EXPORT_SYMBOL_GPL(dax_zero_page_range); 1126 1127 /** 1128 * dax_truncate_page - handle a partial page being truncated in a DAX file 1129 * @inode: The file being truncated 1130 * @from: The file offset that is being truncated to 1131 * @get_block: The filesystem method used to translate file offsets to blocks 1132 * 1133 * Similar to block_truncate_page(), this function can be called by a 1134 * filesystem when it is truncating a DAX file to handle the partial page. 1135 * 1136 * We work in terms of PAGE_CACHE_SIZE here for commonality with 1137 * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem 1138 * took care of disposing of the unnecessary blocks. Even if the filesystem 1139 * block size is smaller than PAGE_SIZE, we have to zero the rest of the page 1140 * since the file might be mmapped. 1141 */ 1142 int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block) 1143 { 1144 unsigned length = PAGE_CACHE_ALIGN(from) - from; 1145 return dax_zero_page_range(inode, from, length, get_block); 1146 } 1147 EXPORT_SYMBOL_GPL(dax_truncate_page); 1148