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>
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.
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
17 #include <linux/atomic.h>
18 #include <linux/blkdev.h>
19 #include <linux/buffer_head.h>
21 #include <linux/genhd.h>
22 #include <linux/highmem.h>
23 #include <linux/memcontrol.h>
25 #include <linux/mutex.h>
26 #include <linux/pmem.h>
27 #include <linux/sched.h>
28 #include <linux/uio.h>
29 #include <linux/vmstat.h>
31 int dax_clear_blocks(struct inode *inode, sector_t block, long size)
33 struct block_device *bdev = inode->i_sb->s_bdev;
34 sector_t sector = block << (inode->i_blkbits - 9);
42 count = bdev_direct_access(bdev, sector, &addr, &pfn, size);
47 unsigned pgsz = PAGE_SIZE - offset_in_page(addr);
50 clear_pmem(addr, pgsz);
63 EXPORT_SYMBOL_GPL(dax_clear_blocks);
65 static long dax_get_addr(struct buffer_head *bh, void __pmem **addr,
69 sector_t sector = bh->b_blocknr << (blkbits - 9);
70 return bdev_direct_access(bh->b_bdev, sector, addr, &pfn, bh->b_size);
73 /* the clear_pmem() calls are ordered by a wmb_pmem() in the caller */
74 static void dax_new_buf(void __pmem *addr, unsigned size, unsigned first,
75 loff_t pos, loff_t end)
77 loff_t final = end - pos + first; /* The final byte of the buffer */
80 clear_pmem(addr, first);
82 clear_pmem(addr + final, size - final);
85 static bool buffer_written(struct buffer_head *bh)
87 return buffer_mapped(bh) && !buffer_unwritten(bh);
91 * When ext4 encounters a hole, it returns without modifying the buffer_head
92 * which means that we can't trust b_size. To cope with this, we set b_state
93 * to 0 before calling get_block and, if any bit is set, we know we can trust
94 * b_size. Unfortunate, really, since ext4 knows precisely how long a hole is
95 * and would save us time calling get_block repeatedly.
97 static bool buffer_size_valid(struct buffer_head *bh)
99 return bh->b_state != 0;
102 static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
103 loff_t start, loff_t end, get_block_t get_block,
104 struct buffer_head *bh)
109 loff_t bh_max = start;
112 bool need_wmb = false;
114 if (iov_iter_rw(iter) != WRITE)
115 end = min(end, i_size_read(inode));
120 unsigned blkbits = inode->i_blkbits;
121 sector_t block = pos >> blkbits;
122 unsigned first = pos - (block << blkbits);
126 bh->b_size = PAGE_ALIGN(end - pos);
128 retval = get_block(inode, block, bh,
129 iov_iter_rw(iter) == WRITE);
132 if (!buffer_size_valid(bh))
133 bh->b_size = 1 << blkbits;
134 bh_max = pos - first + bh->b_size;
136 unsigned done = bh->b_size -
137 (bh_max - (pos - first));
138 bh->b_blocknr += done >> blkbits;
142 hole = iov_iter_rw(iter) != WRITE && !buffer_written(bh);
145 size = bh->b_size - first;
147 retval = dax_get_addr(bh, &addr, blkbits);
150 if (buffer_unwritten(bh) || buffer_new(bh)) {
151 dax_new_buf(addr, retval, first, pos,
156 size = retval - first;
158 max = min(pos + size, end);
161 if (iov_iter_rw(iter) == WRITE) {
162 len = copy_from_iter_pmem(addr, max - pos, iter);
165 len = copy_to_iter((void __force *)addr, max - pos,
168 len = iov_iter_zero(max - pos, iter);
180 return (pos == start) ? retval : pos - start;
184 * dax_do_io - Perform I/O to a DAX file
185 * @iocb: The control block for this I/O
186 * @inode: The file which the I/O is directed at
187 * @iter: The addresses to do I/O from or to
188 * @pos: The file offset where the I/O starts
189 * @get_block: The filesystem method used to translate file offsets to blocks
190 * @end_io: A filesystem callback for I/O completion
193 * This function uses the same locking scheme as do_blockdev_direct_IO:
194 * If @flags has DIO_LOCKING set, we assume that the i_mutex is held by the
195 * caller for writes. For reads, we take and release the i_mutex ourselves.
196 * If DIO_LOCKING is not set, the filesystem takes care of its own locking.
197 * As with do_blockdev_direct_IO(), we increment i_dio_count while the I/O
200 ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode,
201 struct iov_iter *iter, loff_t pos, get_block_t get_block,
202 dio_iodone_t end_io, int flags)
204 struct buffer_head bh;
205 ssize_t retval = -EINVAL;
206 loff_t end = pos + iov_iter_count(iter);
208 memset(&bh, 0, sizeof(bh));
210 if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ) {
211 struct address_space *mapping = inode->i_mapping;
212 mutex_lock(&inode->i_mutex);
213 retval = filemap_write_and_wait_range(mapping, pos, end - 1);
215 mutex_unlock(&inode->i_mutex);
220 /* Protects against truncate */
221 if (!(flags & DIO_SKIP_DIO_COUNT))
222 inode_dio_begin(inode);
224 retval = dax_io(inode, iter, pos, end, get_block, &bh);
226 if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ)
227 mutex_unlock(&inode->i_mutex);
229 if ((retval > 0) && end_io)
230 end_io(iocb, pos, retval, bh.b_private);
232 if (!(flags & DIO_SKIP_DIO_COUNT))
233 inode_dio_end(inode);
237 EXPORT_SYMBOL_GPL(dax_do_io);
240 * The user has performed a load from a hole in the file. Allocating
241 * a new page in the file would cause excessive storage usage for
242 * workloads with sparse files. We allocate a page cache page instead.
243 * We'll kick it out of the page cache if it's ever written to,
244 * otherwise it will simply fall out of the page cache under memory
245 * pressure without ever having been dirtied.
247 static int dax_load_hole(struct address_space *mapping, struct page *page,
248 struct vm_fault *vmf)
251 struct inode *inode = mapping->host;
253 page = find_or_create_page(mapping, vmf->pgoff,
254 GFP_KERNEL | __GFP_ZERO);
257 /* Recheck i_size under page lock to avoid truncate race */
258 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
259 if (vmf->pgoff >= size) {
261 page_cache_release(page);
262 return VM_FAULT_SIGBUS;
266 return VM_FAULT_LOCKED;
269 static int copy_user_bh(struct page *to, struct buffer_head *bh,
270 unsigned blkbits, unsigned long vaddr)
275 if (dax_get_addr(bh, &vfrom, blkbits) < 0)
277 vto = kmap_atomic(to);
278 copy_user_page(vto, (void __force *)vfrom, vaddr, to);
283 static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
284 struct vm_area_struct *vma, struct vm_fault *vmf)
286 struct address_space *mapping = inode->i_mapping;
287 sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9);
288 unsigned long vaddr = (unsigned long)vmf->virtual_address;
294 i_mmap_lock_read(mapping);
297 * Check truncate didn't happen while we were allocating a block.
298 * If it did, this block may or may not be still allocated to the
299 * file. We can't tell the filesystem to free it because we can't
300 * take i_mutex here. In the worst case, the file still has blocks
301 * allocated past the end of the file.
303 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
304 if (unlikely(vmf->pgoff >= size)) {
309 error = bdev_direct_access(bh->b_bdev, sector, &addr, &pfn, bh->b_size);
312 if (error < PAGE_SIZE) {
317 if (buffer_unwritten(bh) || buffer_new(bh)) {
318 clear_pmem(addr, PAGE_SIZE);
322 error = vm_insert_mixed(vma, vaddr, pfn);
325 i_mmap_unlock_read(mapping);
331 * __dax_fault - handle a page fault on a DAX file
332 * @vma: The virtual memory area where the fault occurred
333 * @vmf: The description of the fault
334 * @get_block: The filesystem method used to translate file offsets to blocks
335 * @complete_unwritten: The filesystem method used to convert unwritten blocks
336 * to written so the data written to them is exposed. This is required for
337 * required by write faults for filesystems that will return unwritten
338 * extent mappings from @get_block, but it is optional for reads as
339 * dax_insert_mapping() will always zero unwritten blocks. If the fs does
340 * not support unwritten extents, the it should pass NULL.
342 * When a page fault occurs, filesystems may call this helper in their
343 * fault handler for DAX files. __dax_fault() assumes the caller has done all
344 * the necessary locking for the page fault to proceed successfully.
346 int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
347 get_block_t get_block, dax_iodone_t complete_unwritten)
349 struct file *file = vma->vm_file;
350 struct address_space *mapping = file->f_mapping;
351 struct inode *inode = mapping->host;
353 struct buffer_head bh;
354 unsigned long vaddr = (unsigned long)vmf->virtual_address;
355 unsigned blkbits = inode->i_blkbits;
361 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
362 if (vmf->pgoff >= size)
363 return VM_FAULT_SIGBUS;
365 memset(&bh, 0, sizeof(bh));
366 block = (sector_t)vmf->pgoff << (PAGE_SHIFT - blkbits);
367 bh.b_size = PAGE_SIZE;
370 page = find_get_page(mapping, vmf->pgoff);
372 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
373 page_cache_release(page);
374 return VM_FAULT_RETRY;
376 if (unlikely(page->mapping != mapping)) {
378 page_cache_release(page);
381 size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
382 if (unlikely(vmf->pgoff >= size)) {
384 * We have a struct page covering a hole in the file
385 * from a read fault and we've raced with a truncate
392 error = get_block(inode, block, &bh, 0);
393 if (!error && (bh.b_size < PAGE_SIZE))
394 error = -EIO; /* fs corruption? */
398 if (!buffer_mapped(&bh) && !buffer_unwritten(&bh) && !vmf->cow_page) {
399 if (vmf->flags & FAULT_FLAG_WRITE) {
400 error = get_block(inode, block, &bh, 1);
401 count_vm_event(PGMAJFAULT);
402 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
403 major = VM_FAULT_MAJOR;
404 if (!error && (bh.b_size < PAGE_SIZE))
409 return dax_load_hole(mapping, page, vmf);
414 struct page *new_page = vmf->cow_page;
415 if (buffer_written(&bh))
416 error = copy_user_bh(new_page, &bh, blkbits, vaddr);
418 clear_user_highpage(new_page, vaddr);
423 i_mmap_lock_read(mapping);
424 /* Check we didn't race with truncate */
425 size = (i_size_read(inode) + PAGE_SIZE - 1) >>
427 if (vmf->pgoff >= size) {
428 i_mmap_unlock_read(mapping);
433 return VM_FAULT_LOCKED;
436 /* Check we didn't race with a read fault installing a new page */
438 page = find_lock_page(mapping, vmf->pgoff);
441 unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
443 delete_from_page_cache(page);
445 page_cache_release(page);
449 * If we successfully insert the new mapping over an unwritten extent,
450 * we need to ensure we convert the unwritten extent. If there is an
451 * error inserting the mapping, the filesystem needs to leave it as
452 * unwritten to prevent exposure of the stale underlying data to
453 * userspace, but we still need to call the completion function so
454 * the private resources on the mapping buffer can be released. We
455 * indicate what the callback should do via the uptodate variable, same
456 * as for normal BH based IO completions.
458 error = dax_insert_mapping(inode, &bh, vma, vmf);
459 if (buffer_unwritten(&bh)) {
460 if (complete_unwritten)
461 complete_unwritten(&bh, !error);
463 WARN_ON_ONCE(!(vmf->flags & FAULT_FLAG_WRITE));
467 if (error == -ENOMEM)
468 return VM_FAULT_OOM | major;
469 /* -EBUSY is fine, somebody else faulted on the same PTE */
470 if ((error < 0) && (error != -EBUSY))
471 return VM_FAULT_SIGBUS | major;
472 return VM_FAULT_NOPAGE | major;
477 page_cache_release(page);
481 EXPORT_SYMBOL(__dax_fault);
484 * dax_fault - handle a page fault on a DAX file
485 * @vma: The virtual memory area where the fault occurred
486 * @vmf: The description of the fault
487 * @get_block: The filesystem method used to translate file offsets to blocks
489 * When a page fault occurs, filesystems may call this helper in their
490 * fault handler for DAX files.
492 int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
493 get_block_t get_block, dax_iodone_t complete_unwritten)
496 struct super_block *sb = file_inode(vma->vm_file)->i_sb;
498 if (vmf->flags & FAULT_FLAG_WRITE) {
499 sb_start_pagefault(sb);
500 file_update_time(vma->vm_file);
502 result = __dax_fault(vma, vmf, get_block, complete_unwritten);
503 if (vmf->flags & FAULT_FLAG_WRITE)
504 sb_end_pagefault(sb);
508 EXPORT_SYMBOL_GPL(dax_fault);
511 * dax_pfn_mkwrite - handle first write to DAX page
512 * @vma: The virtual memory area where the fault occurred
513 * @vmf: The description of the fault
516 int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
518 struct super_block *sb = file_inode(vma->vm_file)->i_sb;
520 sb_start_pagefault(sb);
521 file_update_time(vma->vm_file);
522 sb_end_pagefault(sb);
523 return VM_FAULT_NOPAGE;
525 EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
528 * dax_zero_page_range - zero a range within a page of a DAX file
529 * @inode: The file being truncated
530 * @from: The file offset that is being truncated to
531 * @length: The number of bytes to zero
532 * @get_block: The filesystem method used to translate file offsets to blocks
534 * This function can be called by a filesystem when it is zeroing part of a
535 * page in a DAX file. This is intended for hole-punch operations. If
536 * you are truncating a file, the helper function dax_truncate_page() may be
539 * We work in terms of PAGE_CACHE_SIZE here for commonality with
540 * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
541 * took care of disposing of the unnecessary blocks. Even if the filesystem
542 * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
543 * since the file might be mmapped.
545 int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
546 get_block_t get_block)
548 struct buffer_head bh;
549 pgoff_t index = from >> PAGE_CACHE_SHIFT;
550 unsigned offset = from & (PAGE_CACHE_SIZE-1);
553 /* Block boundary? Nothing to do */
556 BUG_ON((offset + length) > PAGE_CACHE_SIZE);
558 memset(&bh, 0, sizeof(bh));
559 bh.b_size = PAGE_CACHE_SIZE;
560 err = get_block(inode, index, &bh, 0);
563 if (buffer_written(&bh)) {
565 err = dax_get_addr(&bh, &addr, inode->i_blkbits);
568 clear_pmem(addr + offset, length);
574 EXPORT_SYMBOL_GPL(dax_zero_page_range);
577 * dax_truncate_page - handle a partial page being truncated in a DAX file
578 * @inode: The file being truncated
579 * @from: The file offset that is being truncated to
580 * @get_block: The filesystem method used to translate file offsets to blocks
582 * Similar to block_truncate_page(), this function can be called by a
583 * filesystem when it is truncating a DAX file to handle the partial page.
585 * We work in terms of PAGE_CACHE_SIZE here for commonality with
586 * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
587 * took care of disposing of the unnecessary blocks. Even if the filesystem
588 * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
589 * since the file might be mmapped.
591 int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
593 unsigned length = PAGE_CACHE_ALIGN(from) - from;
594 return dax_zero_page_range(inode, from, length, get_block);
596 EXPORT_SYMBOL_GPL(dax_truncate_page);