dax.c 21.1 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
/*
 * fs/dax.c - Direct Access filesystem code
 * Copyright (c) 2013-2014 Intel Corporation
 * Author: Matthew Wilcox <matthew.r.wilcox@intel.com>
 * Author: Ross Zwisler <ross.zwisler@linux.intel.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 */

#include <linux/atomic.h>
#include <linux/blkdev.h>
#include <linux/buffer_head.h>
#include <linux/fs.h>
#include <linux/genhd.h>
22 23 24
#include <linux/highmem.h>
#include <linux/memcontrol.h>
#include <linux/mm.h>
25
#include <linux/mutex.h>
26
#include <linux/sched.h>
27
#include <linux/uio.h>
28
#include <linux/vmstat.h>
29

30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
int dax_clear_blocks(struct inode *inode, sector_t block, long size)
{
	struct block_device *bdev = inode->i_sb->s_bdev;
	sector_t sector = block << (inode->i_blkbits - 9);

	might_sleep();
	do {
		void *addr;
		unsigned long pfn;
		long count;

		count = bdev_direct_access(bdev, sector, &addr, &pfn, size);
		if (count < 0)
			return count;
		BUG_ON(size < count);
		while (count > 0) {
			unsigned pgsz = PAGE_SIZE - offset_in_page(addr);
			if (pgsz > count)
				pgsz = count;
			if (pgsz < PAGE_SIZE)
				memset(addr, 0, pgsz);
			else
				clear_page(addr);
			addr += pgsz;
			size -= pgsz;
			count -= pgsz;
			BUG_ON(pgsz & 511);
			sector += pgsz / 512;
			cond_resched();
		}
	} while (size);

	return 0;
}
EXPORT_SYMBOL_GPL(dax_clear_blocks);

66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
static long dax_get_addr(struct buffer_head *bh, void **addr, unsigned blkbits)
{
	unsigned long pfn;
	sector_t sector = bh->b_blocknr << (blkbits - 9);
	return bdev_direct_access(bh->b_bdev, sector, addr, &pfn, bh->b_size);
}

static void dax_new_buf(void *addr, unsigned size, unsigned first, loff_t pos,
			loff_t end)
{
	loff_t final = end - pos + first; /* The final byte of the buffer */

	if (first > 0)
		memset(addr, 0, first);
	if (final < size)
		memset(addr + final, 0, size - final);
}

static bool buffer_written(struct buffer_head *bh)
{
	return buffer_mapped(bh) && !buffer_unwritten(bh);
}

/*
 * When ext4 encounters a hole, it returns without modifying the buffer_head
 * which means that we can't trust b_size.  To cope with this, we set b_state
 * to 0 before calling get_block and, if any bit is set, we know we can trust
 * b_size.  Unfortunate, really, since ext4 knows precisely how long a hole is
 * and would save us time calling get_block repeatedly.
 */
static bool buffer_size_valid(struct buffer_head *bh)
{
	return bh->b_state != 0;
}

O
Omar Sandoval 已提交
101 102 103
static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
		      loff_t start, loff_t end, get_block_t get_block,
		      struct buffer_head *bh)
104 105 106 107 108 109 110 111
{
	ssize_t retval = 0;
	loff_t pos = start;
	loff_t max = start;
	loff_t bh_max = start;
	void *addr;
	bool hole = false;

O
Omar Sandoval 已提交
112
	if (iov_iter_rw(iter) != WRITE)
113 114 115 116 117 118 119 120 121 122 123 124 125 126
		end = min(end, i_size_read(inode));

	while (pos < end) {
		unsigned len;
		if (pos == max) {
			unsigned blkbits = inode->i_blkbits;
			sector_t block = pos >> blkbits;
			unsigned first = pos - (block << blkbits);
			long size;

			if (pos == bh_max) {
				bh->b_size = PAGE_ALIGN(end - pos);
				bh->b_state = 0;
				retval = get_block(inode, block, bh,
O
Omar Sandoval 已提交
127
						   iov_iter_rw(iter) == WRITE);
128 129 130 131 132 133 134 135 136 137 138 139
				if (retval)
					break;
				if (!buffer_size_valid(bh))
					bh->b_size = 1 << blkbits;
				bh_max = pos - first + bh->b_size;
			} else {
				unsigned done = bh->b_size -
						(bh_max - (pos - first));
				bh->b_blocknr += done >> blkbits;
				bh->b_size -= done;
			}

O
Omar Sandoval 已提交
140
			hole = iov_iter_rw(iter) != WRITE && !buffer_written(bh);
141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156
			if (hole) {
				addr = NULL;
				size = bh->b_size - first;
			} else {
				retval = dax_get_addr(bh, &addr, blkbits);
				if (retval < 0)
					break;
				if (buffer_unwritten(bh) || buffer_new(bh))
					dax_new_buf(addr, retval, first, pos,
									end);
				addr += first;
				size = retval - first;
			}
			max = min(pos + size, end);
		}

O
Omar Sandoval 已提交
157
		if (iov_iter_rw(iter) == WRITE)
M
Matthew Wilcox 已提交
158
			len = copy_from_iter_nocache(addr, max - pos, iter);
159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190
		else if (!hole)
			len = copy_to_iter(addr, max - pos, iter);
		else
			len = iov_iter_zero(max - pos, iter);

		if (!len)
			break;

		pos += len;
		addr += len;
	}

	return (pos == start) ? retval : pos - start;
}

/**
 * dax_do_io - Perform I/O to a DAX file
 * @iocb: The control block for this I/O
 * @inode: The file which the I/O is directed at
 * @iter: The addresses to do I/O from or to
 * @pos: The file offset where the I/O starts
 * @get_block: The filesystem method used to translate file offsets to blocks
 * @end_io: A filesystem callback for I/O completion
 * @flags: See below
 *
 * This function uses the same locking scheme as do_blockdev_direct_IO:
 * If @flags has DIO_LOCKING set, we assume that the i_mutex is held by the
 * caller for writes.  For reads, we take and release the i_mutex ourselves.
 * If DIO_LOCKING is not set, the filesystem takes care of its own locking.
 * As with do_blockdev_direct_IO(), we increment i_dio_count while the I/O
 * is in progress.
 */
O
Omar Sandoval 已提交
191 192 193
ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode,
		  struct iov_iter *iter, loff_t pos, get_block_t get_block,
		  dio_iodone_t end_io, int flags)
194 195 196 197 198 199 200
{
	struct buffer_head bh;
	ssize_t retval = -EINVAL;
	loff_t end = pos + iov_iter_count(iter);

	memset(&bh, 0, sizeof(bh));

O
Omar Sandoval 已提交
201
	if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ) {
202 203 204 205 206 207 208 209 210 211
		struct address_space *mapping = inode->i_mapping;
		mutex_lock(&inode->i_mutex);
		retval = filemap_write_and_wait_range(mapping, pos, end - 1);
		if (retval) {
			mutex_unlock(&inode->i_mutex);
			goto out;
		}
	}

	/* Protects against truncate */
212 213
	if (!(flags & DIO_SKIP_DIO_COUNT))
		inode_dio_begin(inode);
214

O
Omar Sandoval 已提交
215
	retval = dax_io(inode, iter, pos, end, get_block, &bh);
216

O
Omar Sandoval 已提交
217
	if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ)
218 219 220 221 222
		mutex_unlock(&inode->i_mutex);

	if ((retval > 0) && end_io)
		end_io(iocb, pos, retval, bh.b_private);

223 224
	if (!(flags & DIO_SKIP_DIO_COUNT))
		inode_dio_end(inode);
225 226 227 228
 out:
	return retval;
}
EXPORT_SYMBOL_GPL(dax_do_io);
229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311

/*
 * The user has performed a load from a hole in the file.  Allocating
 * a new page in the file would cause excessive storage usage for
 * workloads with sparse files.  We allocate a page cache page instead.
 * We'll kick it out of the page cache if it's ever written to,
 * otherwise it will simply fall out of the page cache under memory
 * pressure without ever having been dirtied.
 */
static int dax_load_hole(struct address_space *mapping, struct page *page,
							struct vm_fault *vmf)
{
	unsigned long size;
	struct inode *inode = mapping->host;
	if (!page)
		page = find_or_create_page(mapping, vmf->pgoff,
						GFP_KERNEL | __GFP_ZERO);
	if (!page)
		return VM_FAULT_OOM;
	/* Recheck i_size under page lock to avoid truncate race */
	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
	if (vmf->pgoff >= size) {
		unlock_page(page);
		page_cache_release(page);
		return VM_FAULT_SIGBUS;
	}

	vmf->page = page;
	return VM_FAULT_LOCKED;
}

static int copy_user_bh(struct page *to, struct buffer_head *bh,
			unsigned blkbits, unsigned long vaddr)
{
	void *vfrom, *vto;
	if (dax_get_addr(bh, &vfrom, blkbits) < 0)
		return -EIO;
	vto = kmap_atomic(to);
	copy_user_page(vto, vfrom, vaddr, to);
	kunmap_atomic(vto);
	return 0;
}

static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
			struct vm_area_struct *vma, struct vm_fault *vmf)
{
	sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9);
	unsigned long vaddr = (unsigned long)vmf->virtual_address;
	void *addr;
	unsigned long pfn;
	pgoff_t size;
	int error;

	/*
	 * Check truncate didn't happen while we were allocating a block.
	 * If it did, this block may or may not be still allocated to the
	 * file.  We can't tell the filesystem to free it because we can't
	 * take i_mutex here.  In the worst case, the file still has blocks
	 * allocated past the end of the file.
	 */
	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
	if (unlikely(vmf->pgoff >= size)) {
		error = -EIO;
		goto out;
	}

	error = bdev_direct_access(bh->b_bdev, sector, &addr, &pfn, bh->b_size);
	if (error < 0)
		goto out;
	if (error < PAGE_SIZE) {
		error = -EIO;
		goto out;
	}

	if (buffer_unwritten(bh) || buffer_new(bh))
		clear_page(addr);

	error = vm_insert_mixed(vma, vaddr, pfn);

 out:
	return error;
}

312 313 314 315 316
/**
 * __dax_fault - handle a page fault on a DAX file
 * @vma: The virtual memory area where the fault occurred
 * @vmf: The description of the fault
 * @get_block: The filesystem method used to translate file offsets to blocks
317 318 319 320 321 322
 * @complete_unwritten: The filesystem method used to convert unwritten blocks
 *	to written so the data written to them is exposed. This is required for
 *	required by write faults for filesystems that will return unwritten
 *	extent mappings from @get_block, but it is optional for reads as
 *	dax_insert_mapping() will always zero unwritten blocks. If the fs does
 *	not support unwritten extents, the it should pass NULL.
323 324 325 326 327 328
 *
 * When a page fault occurs, filesystems may call this helper in their
 * fault handler for DAX files. __dax_fault() assumes the caller has done all
 * the necessary locking for the page fault to proceed successfully.
 */
int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
329
			get_block_t get_block, dax_iodone_t complete_unwritten)
330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369
{
	struct file *file = vma->vm_file;
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	struct page *page;
	struct buffer_head bh;
	unsigned long vaddr = (unsigned long)vmf->virtual_address;
	unsigned blkbits = inode->i_blkbits;
	sector_t block;
	pgoff_t size;
	int error;
	int major = 0;

	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
	if (vmf->pgoff >= size)
		return VM_FAULT_SIGBUS;

	memset(&bh, 0, sizeof(bh));
	block = (sector_t)vmf->pgoff << (PAGE_SHIFT - blkbits);
	bh.b_size = PAGE_SIZE;

 repeat:
	page = find_get_page(mapping, vmf->pgoff);
	if (page) {
		if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
			page_cache_release(page);
			return VM_FAULT_RETRY;
		}
		if (unlikely(page->mapping != mapping)) {
			unlock_page(page);
			page_cache_release(page);
			goto repeat;
		}
		size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
		if (unlikely(vmf->pgoff >= size)) {
			/*
			 * We have a struct page covering a hole in the file
			 * from a read fault and we've raced with a truncate
			 */
			error = -EIO;
370
			goto unlock;
371
		}
372 373
	} else {
		i_mmap_lock_write(mapping);
374 375 376 377 378 379
	}

	error = get_block(inode, block, &bh, 0);
	if (!error && (bh.b_size < PAGE_SIZE))
		error = -EIO;		/* fs corruption? */
	if (error)
380
		goto unlock;
381 382 383 384 385 386 387 388 389 390

	if (!buffer_mapped(&bh) && !buffer_unwritten(&bh) && !vmf->cow_page) {
		if (vmf->flags & FAULT_FLAG_WRITE) {
			error = get_block(inode, block, &bh, 1);
			count_vm_event(PGMAJFAULT);
			mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
			major = VM_FAULT_MAJOR;
			if (!error && (bh.b_size < PAGE_SIZE))
				error = -EIO;
			if (error)
391
				goto unlock;
392
		} else {
393
			i_mmap_unlock_write(mapping);
394 395 396 397 398 399 400 401 402 403 404
			return dax_load_hole(mapping, page, vmf);
		}
	}

	if (vmf->cow_page) {
		struct page *new_page = vmf->cow_page;
		if (buffer_written(&bh))
			error = copy_user_bh(new_page, &bh, blkbits, vaddr);
		else
			clear_user_highpage(new_page, vaddr);
		if (error)
405
			goto unlock;
406 407 408 409 410 411 412
		vmf->page = page;
		if (!page) {
			/* Check we didn't race with truncate */
			size = (i_size_read(inode) + PAGE_SIZE - 1) >>
								PAGE_SHIFT;
			if (vmf->pgoff >= size) {
				error = -EIO;
413
				goto unlock;
414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430
			}
		}
		return VM_FAULT_LOCKED;
	}

	/* Check we didn't race with a read fault installing a new page */
	if (!page && major)
		page = find_lock_page(mapping, vmf->pgoff);

	if (page) {
		unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
							PAGE_CACHE_SIZE, 0);
		delete_from_page_cache(page);
		unlock_page(page);
		page_cache_release(page);
	}

431 432 433 434 435 436 437 438 439 440
	/*
	 * If we successfully insert the new mapping over an unwritten extent,
	 * we need to ensure we convert the unwritten extent. If there is an
	 * error inserting the mapping, the filesystem needs to leave it as
	 * unwritten to prevent exposure of the stale underlying data to
	 * userspace, but we still need to call the completion function so
	 * the private resources on the mapping buffer can be released. We
	 * indicate what the callback should do via the uptodate variable, same
	 * as for normal BH based IO completions.
	 */
441
	error = dax_insert_mapping(inode, &bh, vma, vmf);
442 443 444 445 446 447
	if (buffer_unwritten(&bh)) {
		if (complete_unwritten)
			complete_unwritten(&bh, !error);
		else
			WARN_ON_ONCE(!(vmf->flags & FAULT_FLAG_WRITE));
	}
448

449 450
	if (!page)
		i_mmap_unlock_write(mapping);
451 452 453 454 455 456 457 458
 out:
	if (error == -ENOMEM)
		return VM_FAULT_OOM | major;
	/* -EBUSY is fine, somebody else faulted on the same PTE */
	if ((error < 0) && (error != -EBUSY))
		return VM_FAULT_SIGBUS | major;
	return VM_FAULT_NOPAGE | major;

459
 unlock:
460 461 462
	if (page) {
		unlock_page(page);
		page_cache_release(page);
463 464
	} else {
		i_mmap_unlock_write(mapping);
465
	}
466

467 468
	goto out;
}
469
EXPORT_SYMBOL(__dax_fault);
470 471 472 473 474 475 476 477 478 479 480

/**
 * dax_fault - handle a page fault on a DAX file
 * @vma: The virtual memory area where the fault occurred
 * @vmf: The description of the fault
 * @get_block: The filesystem method used to translate file offsets to blocks
 *
 * When a page fault occurs, filesystems may call this helper in their
 * fault handler for DAX files.
 */
int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
481
	      get_block_t get_block, dax_iodone_t complete_unwritten)
482 483 484 485 486 487 488 489
{
	int result;
	struct super_block *sb = file_inode(vma->vm_file)->i_sb;

	if (vmf->flags & FAULT_FLAG_WRITE) {
		sb_start_pagefault(sb);
		file_update_time(vma->vm_file);
	}
490
	result = __dax_fault(vma, vmf, get_block, complete_unwritten);
491 492 493 494 495 496
	if (vmf->flags & FAULT_FLAG_WRITE)
		sb_end_pagefault(sb);

	return result;
}
EXPORT_SYMBOL_GPL(dax_fault);
497

498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
/*
 * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
 * more often than one might expect in the below function.
 */
#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)

int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
		pmd_t *pmd, unsigned int flags, get_block_t get_block,
		dax_iodone_t complete_unwritten)
{
	struct file *file = vma->vm_file;
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	struct buffer_head bh;
	unsigned blkbits = inode->i_blkbits;
	unsigned long pmd_addr = address & PMD_MASK;
	bool write = flags & FAULT_FLAG_WRITE;
	long length;
	void *kaddr;
	pgoff_t size, pgoff;
	sector_t block, sector;
	unsigned long pfn;
	int result = 0;

	/* Fall back to PTEs if we're going to COW */
	if (write && !(vma->vm_flags & VM_SHARED))
		return VM_FAULT_FALLBACK;
	/* If the PMD would extend outside the VMA */
	if (pmd_addr < vma->vm_start)
		return VM_FAULT_FALLBACK;
	if ((pmd_addr + PMD_SIZE) > vma->vm_end)
		return VM_FAULT_FALLBACK;

	pgoff = ((pmd_addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
	if (pgoff >= size)
		return VM_FAULT_SIGBUS;
	/* If the PMD would cover blocks out of the file */
	if ((pgoff | PG_PMD_COLOUR) >= size)
		return VM_FAULT_FALLBACK;

	memset(&bh, 0, sizeof(bh));
	block = (sector_t)pgoff << (PAGE_SHIFT - blkbits);

	bh.b_size = PMD_SIZE;
544
	i_mmap_lock_write(mapping);
545 546 547 548 549 550 551 552 553 554 555 556
	length = get_block(inode, block, &bh, write);
	if (length)
		return VM_FAULT_SIGBUS;

	/*
	 * If the filesystem isn't willing to tell us the length of a hole,
	 * just fall back to PTEs.  Calling get_block 512 times in a loop
	 * would be silly.
	 */
	if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
		goto fallback;

557 558 559 560 561 562
	/*
	 * If a truncate happened while we were allocating blocks, we may
	 * leave blocks allocated to the file that are beyond EOF.  We can't
	 * take i_mutex here, so just leave them hanging; they'll be freed
	 * when the file is deleted.
	 */
563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613
	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
	if (pgoff >= size) {
		result = VM_FAULT_SIGBUS;
		goto out;
	}
	if ((pgoff | PG_PMD_COLOUR) >= size)
		goto fallback;

	if (is_huge_zero_pmd(*pmd))
		unmap_mapping_range(mapping, pgoff << PAGE_SHIFT, PMD_SIZE, 0);

	if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {
		bool set;
		spinlock_t *ptl;
		struct mm_struct *mm = vma->vm_mm;
		struct page *zero_page = get_huge_zero_page();
		if (unlikely(!zero_page))
			goto fallback;

		ptl = pmd_lock(mm, pmd);
		set = set_huge_zero_page(NULL, mm, vma, pmd_addr, pmd,
								zero_page);
		spin_unlock(ptl);
		result = VM_FAULT_NOPAGE;
	} else {
		sector = bh.b_blocknr << (blkbits - 9);
		length = bdev_direct_access(bh.b_bdev, sector, &kaddr, &pfn,
						bh.b_size);
		if (length < 0) {
			result = VM_FAULT_SIGBUS;
			goto out;
		}
		if ((length < PMD_SIZE) || (pfn & PG_PMD_COLOUR))
			goto fallback;

		if (buffer_unwritten(&bh) || buffer_new(&bh)) {
			int i;
			for (i = 0; i < PTRS_PER_PMD; i++)
				clear_page(kaddr + i * PAGE_SIZE);
			count_vm_event(PGMAJFAULT);
			mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
			result |= VM_FAULT_MAJOR;
		}

		result |= vmf_insert_pfn_pmd(vma, address, pmd, pfn, write);
	}

 out:
	if (buffer_unwritten(&bh))
		complete_unwritten(&bh, !(result & VM_FAULT_ERROR));

614 615
	i_mmap_unlock_write(mapping);

616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652
	return result;

 fallback:
	count_vm_event(THP_FAULT_FALLBACK);
	result = VM_FAULT_FALLBACK;
	goto out;
}
EXPORT_SYMBOL_GPL(__dax_pmd_fault);

/**
 * dax_pmd_fault - handle a PMD fault on a DAX file
 * @vma: The virtual memory area where the fault occurred
 * @vmf: The description of the fault
 * @get_block: The filesystem method used to translate file offsets to blocks
 *
 * When a page fault occurs, filesystems may call this helper in their
 * pmd_fault handler for DAX files.
 */
int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
			pmd_t *pmd, unsigned int flags, get_block_t get_block,
			dax_iodone_t complete_unwritten)
{
	int result;
	struct super_block *sb = file_inode(vma->vm_file)->i_sb;

	if (flags & FAULT_FLAG_WRITE) {
		sb_start_pagefault(sb);
		file_update_time(vma->vm_file);
	}
	result = __dax_pmd_fault(vma, address, pmd, flags, get_block,
				complete_unwritten);
	if (flags & FAULT_FLAG_WRITE)
		sb_end_pagefault(sb);

	return result;
}
EXPORT_SYMBOL_GPL(dax_pmd_fault);
653
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
654

655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671
/**
 * dax_pfn_mkwrite - handle first write to DAX page
 * @vma: The virtual memory area where the fault occurred
 * @vmf: The description of the fault
 *
 */
int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
{
	struct super_block *sb = file_inode(vma->vm_file)->i_sb;

	sb_start_pagefault(sb);
	file_update_time(vma->vm_file);
	sb_end_pagefault(sb);
	return VM_FAULT_NOPAGE;
}
EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);

672
/**
M
Matthew Wilcox 已提交
673
 * dax_zero_page_range - zero a range within a page of a DAX file
674 675
 * @inode: The file being truncated
 * @from: The file offset that is being truncated to
M
Matthew Wilcox 已提交
676
 * @length: The number of bytes to zero
677 678
 * @get_block: The filesystem method used to translate file offsets to blocks
 *
M
Matthew Wilcox 已提交
679 680 681 682
 * This function can be called by a filesystem when it is zeroing part of a
 * page in a DAX file.  This is intended for hole-punch operations.  If
 * you are truncating a file, the helper function dax_truncate_page() may be
 * more convenient.
683 684 685 686 687
 *
 * We work in terms of PAGE_CACHE_SIZE here for commonality with
 * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
 * took care of disposing of the unnecessary blocks.  Even if the filesystem
 * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
M
Matthew Wilcox 已提交
688
 * since the file might be mmapped.
689
 */
M
Matthew Wilcox 已提交
690 691
int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
							get_block_t get_block)
692 693 694 695 696 697 698 699 700
{
	struct buffer_head bh;
	pgoff_t index = from >> PAGE_CACHE_SHIFT;
	unsigned offset = from & (PAGE_CACHE_SIZE-1);
	int err;

	/* Block boundary? Nothing to do */
	if (!length)
		return 0;
M
Matthew Wilcox 已提交
701
	BUG_ON((offset + length) > PAGE_CACHE_SIZE);
702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717

	memset(&bh, 0, sizeof(bh));
	bh.b_size = PAGE_CACHE_SIZE;
	err = get_block(inode, index, &bh, 0);
	if (err < 0)
		return err;
	if (buffer_written(&bh)) {
		void *addr;
		err = dax_get_addr(&bh, &addr, inode->i_blkbits);
		if (err < 0)
			return err;
		memset(addr + offset, 0, length);
	}

	return 0;
}
M
Matthew Wilcox 已提交
718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739
EXPORT_SYMBOL_GPL(dax_zero_page_range);

/**
 * dax_truncate_page - handle a partial page being truncated in a DAX file
 * @inode: The file being truncated
 * @from: The file offset that is being truncated to
 * @get_block: The filesystem method used to translate file offsets to blocks
 *
 * Similar to block_truncate_page(), this function can be called by a
 * filesystem when it is truncating a DAX file to handle the partial page.
 *
 * We work in terms of PAGE_CACHE_SIZE here for commonality with
 * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
 * took care of disposing of the unnecessary blocks.  Even if the filesystem
 * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
 * since the file might be mmapped.
 */
int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
{
	unsigned length = PAGE_CACHE_ALIGN(from) - from;
	return dax_zero_page_range(inode, from, length, get_block);
}
740
EXPORT_SYMBOL_GPL(dax_truncate_page);