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>
20 #include <linux/dax.h>
22 #include <linux/genhd.h>
23 #include <linux/highmem.h>
24 #include <linux/memcontrol.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>
35 static long dax_map_atomic(struct block_device
*bdev
, struct blk_dax_ctl
*dax
)
37 struct request_queue
*q
= bdev
->bd_queue
;
40 dax
->addr
= (void __pmem
*) ERR_PTR(-EIO
);
41 if (blk_queue_enter(q
, true) != 0)
44 rc
= bdev_direct_access(bdev
, dax
);
46 dax
->addr
= (void __pmem
*) ERR_PTR(rc
);
53 static void dax_unmap_atomic(struct block_device
*bdev
,
54 const struct blk_dax_ctl
*dax
)
56 if (IS_ERR(dax
->addr
))
58 blk_queue_exit(bdev
->bd_queue
);
61 struct page
*read_dax_sector(struct block_device
*bdev
, sector_t n
)
63 struct page
*page
= alloc_pages(GFP_KERNEL
, 0);
64 struct blk_dax_ctl dax
= {
66 .sector
= n
& ~((((int) PAGE_SIZE
) / 512) - 1),
71 return ERR_PTR(-ENOMEM
);
73 rc
= dax_map_atomic(bdev
, &dax
);
76 memcpy_from_pmem(page_address(page
), dax
.addr
, PAGE_SIZE
);
77 dax_unmap_atomic(bdev
, &dax
);
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.
86 int dax_clear_blocks(struct inode
*inode
, sector_t block
, long _size
)
88 struct block_device
*bdev
= inode
->i_sb
->s_bdev
;
89 struct blk_dax_ctl dax
= {
90 .sector
= block
<< (inode
->i_blkbits
- 9),
98 count
= dax_map_atomic(bdev
, &dax
);
101 sz
= min_t(long, count
, SZ_128K
);
102 clear_pmem(dax
.addr
, sz
);
104 dax
.sector
+= sz
/ 512;
105 dax_unmap_atomic(bdev
, &dax
);
112 EXPORT_SYMBOL_GPL(dax_clear_blocks
);
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
)
118 loff_t final
= end
- pos
+ first
; /* The final byte of the buffer */
121 clear_pmem(addr
, first
);
123 clear_pmem(addr
+ final
, size
- final
);
126 static bool buffer_written(struct buffer_head
*bh
)
128 return buffer_mapped(bh
) && !buffer_unwritten(bh
);
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.
138 static bool buffer_size_valid(struct buffer_head
*bh
)
140 return bh
->b_state
!= 0;
144 static sector_t
to_sector(const struct buffer_head
*bh
,
145 const struct inode
*inode
)
147 sector_t sector
= bh
->b_blocknr
<< (inode
->i_blkbits
- 9);
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
)
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
;
161 struct blk_dax_ctl dax
= {
162 .addr
= (void __pmem
*) ERR_PTR(-EIO
),
166 end
= min(end
, i_size_read(inode
));
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
);
178 bh
->b_size
= PAGE_ALIGN(end
- pos
);
180 rc
= get_block(inode
, block
, bh
, rw
== WRITE
);
183 if (!buffer_size_valid(bh
))
184 bh
->b_size
= 1 << blkbits
;
185 bh_max
= pos
- first
+ bh
->b_size
;
188 unsigned done
= bh
->b_size
-
189 (bh_max
- (pos
- first
));
190 bh
->b_blocknr
+= done
>> blkbits
;
194 hole
= rw
== READ
&& !buffer_written(bh
);
196 size
= bh
->b_size
- first
;
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
);
206 if (buffer_unwritten(bh
) || buffer_new(bh
)) {
207 dax_new_buf(dax
.addr
, map_len
, first
,
212 size
= map_len
- first
;
214 max
= min(pos
+ size
, end
);
217 if (iov_iter_rw(iter
) == WRITE
) {
218 len
= copy_from_iter_pmem(dax
.addr
, max
- pos
, iter
);
221 len
= copy_to_iter((void __force
*) dax
.addr
, max
- pos
,
224 len
= iov_iter_zero(max
- pos
, iter
);
232 if (!IS_ERR(dax
.addr
))
238 dax_unmap_atomic(bdev
, &dax
);
240 return (pos
== start
) ? rc
: pos
- start
;
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
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
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
)
264 struct buffer_head bh
;
265 ssize_t retval
= -EINVAL
;
266 loff_t end
= pos
+ iov_iter_count(iter
);
268 memset(&bh
, 0, sizeof(bh
));
269 bh
.b_bdev
= inode
->i_sb
->s_bdev
;
271 if ((flags
& DIO_LOCKING
) && iov_iter_rw(iter
) == READ
) {
272 struct address_space
*mapping
= inode
->i_mapping
;
274 retval
= filemap_write_and_wait_range(mapping
, pos
, end
- 1);
281 /* Protects against truncate */
282 if (!(flags
& DIO_SKIP_DIO_COUNT
))
283 inode_dio_begin(inode
);
285 retval
= dax_io(inode
, iter
, pos
, end
, get_block
, &bh
);
287 if ((flags
& DIO_LOCKING
) && iov_iter_rw(iter
) == READ
)
290 if ((retval
> 0) && end_io
)
291 end_io(iocb
, pos
, retval
, bh
.b_private
);
293 if (!(flags
& DIO_SKIP_DIO_COUNT
))
294 inode_dio_end(inode
);
298 EXPORT_SYMBOL_GPL(dax_do_io
);
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.
308 static int dax_load_hole(struct address_space
*mapping
, struct page
*page
,
309 struct vm_fault
*vmf
)
312 struct inode
*inode
= mapping
->host
;
314 page
= find_or_create_page(mapping
, vmf
->pgoff
,
315 GFP_KERNEL
| __GFP_ZERO
);
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
) {
322 page_cache_release(page
);
323 return VM_FAULT_SIGBUS
;
327 return VM_FAULT_LOCKED
;
330 static int copy_user_bh(struct page
*to
, struct inode
*inode
,
331 struct buffer_head
*bh
, unsigned long vaddr
)
333 struct blk_dax_ctl dax
= {
334 .sector
= to_sector(bh
, inode
),
337 struct block_device
*bdev
= bh
->b_bdev
;
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
);
345 dax_unmap_atomic(bdev
, &dax
);
350 #define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_CACHE_SHIFT))
352 static int dax_radix_entry(struct address_space
*mapping
, pgoff_t index
,
353 sector_t sector
, bool pmd_entry
, bool dirty
)
355 struct radix_tree_root
*page_tree
= &mapping
->page_tree
;
356 pgoff_t pmd_index
= DAX_PMD_INDEX(index
);
360 WARN_ON_ONCE(pmd_entry
&& !dirty
);
361 __mark_inode_dirty(mapping
->host
, I_DIRTY_PAGES
);
363 spin_lock_irq(&mapping
->tree_lock
);
365 entry
= radix_tree_lookup(page_tree
, pmd_index
);
366 if (entry
&& RADIX_DAX_TYPE(entry
) == RADIX_DAX_PMD
) {
371 entry
= radix_tree_lookup(page_tree
, index
);
373 type
= RADIX_DAX_TYPE(entry
);
374 if (WARN_ON_ONCE(type
!= RADIX_DAX_PTE
&&
375 type
!= RADIX_DAX_PMD
)) {
380 if (!pmd_entry
|| type
== RADIX_DAX_PMD
)
384 * We only insert dirty PMD entries into the radix tree. This
385 * means we don't need to worry about removing a dirty PTE
386 * entry and inserting a clean PMD entry, thus reducing the
387 * range we would flush with a follow-up fsync/msync call.
389 radix_tree_delete(&mapping
->page_tree
, index
);
390 mapping
->nrexceptional
--;
393 if (sector
== NO_SECTOR
) {
395 * This can happen during correct operation if our pfn_mkwrite
396 * fault raced against a hole punch operation. If this
397 * happens the pte that was hole punched will have been
398 * unmapped and the radix tree entry will have been removed by
399 * the time we are called, but the call will still happen. We
400 * will return all the way up to wp_pfn_shared(), where the
401 * pte_same() check will fail, eventually causing page fault
402 * to be retried by the CPU.
407 error
= radix_tree_insert(page_tree
, index
,
408 RADIX_DAX_ENTRY(sector
, pmd_entry
));
412 mapping
->nrexceptional
++;
415 radix_tree_tag_set(page_tree
, index
, PAGECACHE_TAG_DIRTY
);
417 spin_unlock_irq(&mapping
->tree_lock
);
421 static int dax_writeback_one(struct block_device
*bdev
,
422 struct address_space
*mapping
, pgoff_t index
, void *entry
)
424 struct radix_tree_root
*page_tree
= &mapping
->page_tree
;
425 int type
= RADIX_DAX_TYPE(entry
);
426 struct radix_tree_node
*node
;
427 struct blk_dax_ctl dax
;
431 spin_lock_irq(&mapping
->tree_lock
);
433 * Regular page slots are stabilized by the page lock even
434 * without the tree itself locked. These unlocked entries
435 * need verification under the tree lock.
437 if (!__radix_tree_lookup(page_tree
, index
, &node
, &slot
))
442 /* another fsync thread may have already written back this entry */
443 if (!radix_tree_tag_get(page_tree
, index
, PAGECACHE_TAG_TOWRITE
))
446 if (WARN_ON_ONCE(type
!= RADIX_DAX_PTE
&& type
!= RADIX_DAX_PMD
)) {
451 dax
.sector
= RADIX_DAX_SECTOR(entry
);
452 dax
.size
= (type
== RADIX_DAX_PMD
? PMD_SIZE
: PAGE_SIZE
);
453 spin_unlock_irq(&mapping
->tree_lock
);
456 * We cannot hold tree_lock while calling dax_map_atomic() because it
457 * eventually calls cond_resched().
459 ret
= dax_map_atomic(bdev
, &dax
);
463 if (WARN_ON_ONCE(ret
< dax
.size
)) {
468 wb_cache_pmem(dax
.addr
, dax
.size
);
470 spin_lock_irq(&mapping
->tree_lock
);
471 radix_tree_tag_clear(page_tree
, index
, PAGECACHE_TAG_TOWRITE
);
472 spin_unlock_irq(&mapping
->tree_lock
);
474 dax_unmap_atomic(bdev
, &dax
);
478 spin_unlock_irq(&mapping
->tree_lock
);
483 * Flush the mapping to the persistent domain within the byte range of [start,
484 * end]. This is required by data integrity operations to ensure file data is
485 * on persistent storage prior to completion of the operation.
487 int dax_writeback_mapping_range(struct address_space
*mapping
, loff_t start
,
490 struct inode
*inode
= mapping
->host
;
491 struct block_device
*bdev
= inode
->i_sb
->s_bdev
;
492 pgoff_t start_index
, end_index
, pmd_index
;
493 pgoff_t indices
[PAGEVEC_SIZE
];
499 if (WARN_ON_ONCE(inode
->i_blkbits
!= PAGE_SHIFT
))
502 start_index
= start
>> PAGE_CACHE_SHIFT
;
503 end_index
= end
>> PAGE_CACHE_SHIFT
;
504 pmd_index
= DAX_PMD_INDEX(start_index
);
507 entry
= radix_tree_lookup(&mapping
->page_tree
, pmd_index
);
510 /* see if the start of our range is covered by a PMD entry */
511 if (entry
&& RADIX_DAX_TYPE(entry
) == RADIX_DAX_PMD
)
512 start_index
= pmd_index
;
514 tag_pages_for_writeback(mapping
, start_index
, end_index
);
516 pagevec_init(&pvec
, 0);
518 pvec
.nr
= find_get_entries_tag(mapping
, start_index
,
519 PAGECACHE_TAG_TOWRITE
, PAGEVEC_SIZE
,
520 pvec
.pages
, indices
);
525 for (i
= 0; i
< pvec
.nr
; i
++) {
526 if (indices
[i
] > end_index
) {
531 ret
= dax_writeback_one(bdev
, mapping
, indices
[i
],
540 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range
);
542 static int dax_insert_mapping(struct inode
*inode
, struct buffer_head
*bh
,
543 struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
545 unsigned long vaddr
= (unsigned long)vmf
->virtual_address
;
546 struct address_space
*mapping
= inode
->i_mapping
;
547 struct block_device
*bdev
= bh
->b_bdev
;
548 struct blk_dax_ctl dax
= {
549 .sector
= to_sector(bh
, inode
),
555 i_mmap_lock_read(mapping
);
558 * Check truncate didn't happen while we were allocating a block.
559 * If it did, this block may or may not be still allocated to the
560 * file. We can't tell the filesystem to free it because we can't
561 * take i_mutex here. In the worst case, the file still has blocks
562 * allocated past the end of the file.
564 size
= (i_size_read(inode
) + PAGE_SIZE
- 1) >> PAGE_SHIFT
;
565 if (unlikely(vmf
->pgoff
>= size
)) {
570 if (dax_map_atomic(bdev
, &dax
) < 0) {
571 error
= PTR_ERR(dax
.addr
);
575 if (buffer_unwritten(bh
) || buffer_new(bh
)) {
576 clear_pmem(dax
.addr
, PAGE_SIZE
);
579 dax_unmap_atomic(bdev
, &dax
);
581 error
= dax_radix_entry(mapping
, vmf
->pgoff
, dax
.sector
, false,
582 vmf
->flags
& FAULT_FLAG_WRITE
);
586 error
= vm_insert_mixed(vma
, vaddr
, dax
.pfn
);
589 i_mmap_unlock_read(mapping
);
595 * __dax_fault - handle a page fault on a DAX file
596 * @vma: The virtual memory area where the fault occurred
597 * @vmf: The description of the fault
598 * @get_block: The filesystem method used to translate file offsets to blocks
599 * @complete_unwritten: The filesystem method used to convert unwritten blocks
600 * to written so the data written to them is exposed. This is required for
601 * required by write faults for filesystems that will return unwritten
602 * extent mappings from @get_block, but it is optional for reads as
603 * dax_insert_mapping() will always zero unwritten blocks. If the fs does
604 * not support unwritten extents, the it should pass NULL.
606 * When a page fault occurs, filesystems may call this helper in their
607 * fault handler for DAX files. __dax_fault() assumes the caller has done all
608 * the necessary locking for the page fault to proceed successfully.
610 int __dax_fault(struct vm_area_struct
*vma
, struct vm_fault
*vmf
,
611 get_block_t get_block
, dax_iodone_t complete_unwritten
)
613 struct file
*file
= vma
->vm_file
;
614 struct address_space
*mapping
= file
->f_mapping
;
615 struct inode
*inode
= mapping
->host
;
617 struct buffer_head bh
;
618 unsigned long vaddr
= (unsigned long)vmf
->virtual_address
;
619 unsigned blkbits
= inode
->i_blkbits
;
625 size
= (i_size_read(inode
) + PAGE_SIZE
- 1) >> PAGE_SHIFT
;
626 if (vmf
->pgoff
>= size
)
627 return VM_FAULT_SIGBUS
;
629 memset(&bh
, 0, sizeof(bh
));
630 block
= (sector_t
)vmf
->pgoff
<< (PAGE_SHIFT
- blkbits
);
631 bh
.b_bdev
= inode
->i_sb
->s_bdev
;
632 bh
.b_size
= PAGE_SIZE
;
635 page
= find_get_page(mapping
, vmf
->pgoff
);
637 if (!lock_page_or_retry(page
, vma
->vm_mm
, vmf
->flags
)) {
638 page_cache_release(page
);
639 return VM_FAULT_RETRY
;
641 if (unlikely(page
->mapping
!= mapping
)) {
643 page_cache_release(page
);
646 size
= (i_size_read(inode
) + PAGE_SIZE
- 1) >> PAGE_SHIFT
;
647 if (unlikely(vmf
->pgoff
>= size
)) {
649 * We have a struct page covering a hole in the file
650 * from a read fault and we've raced with a truncate
657 error
= get_block(inode
, block
, &bh
, 0);
658 if (!error
&& (bh
.b_size
< PAGE_SIZE
))
659 error
= -EIO
; /* fs corruption? */
663 if (!buffer_mapped(&bh
) && !buffer_unwritten(&bh
) && !vmf
->cow_page
) {
664 if (vmf
->flags
& FAULT_FLAG_WRITE
) {
665 error
= get_block(inode
, block
, &bh
, 1);
666 count_vm_event(PGMAJFAULT
);
667 mem_cgroup_count_vm_event(vma
->vm_mm
, PGMAJFAULT
);
668 major
= VM_FAULT_MAJOR
;
669 if (!error
&& (bh
.b_size
< PAGE_SIZE
))
674 return dax_load_hole(mapping
, page
, vmf
);
679 struct page
*new_page
= vmf
->cow_page
;
680 if (buffer_written(&bh
))
681 error
= copy_user_bh(new_page
, inode
, &bh
, vaddr
);
683 clear_user_highpage(new_page
, vaddr
);
688 i_mmap_lock_read(mapping
);
689 /* Check we didn't race with truncate */
690 size
= (i_size_read(inode
) + PAGE_SIZE
- 1) >>
692 if (vmf
->pgoff
>= size
) {
693 i_mmap_unlock_read(mapping
);
698 return VM_FAULT_LOCKED
;
701 /* Check we didn't race with a read fault installing a new page */
703 page
= find_lock_page(mapping
, vmf
->pgoff
);
706 unmap_mapping_range(mapping
, vmf
->pgoff
<< PAGE_SHIFT
,
708 delete_from_page_cache(page
);
710 page_cache_release(page
);
715 * If we successfully insert the new mapping over an unwritten extent,
716 * we need to ensure we convert the unwritten extent. If there is an
717 * error inserting the mapping, the filesystem needs to leave it as
718 * unwritten to prevent exposure of the stale underlying data to
719 * userspace, but we still need to call the completion function so
720 * the private resources on the mapping buffer can be released. We
721 * indicate what the callback should do via the uptodate variable, same
722 * as for normal BH based IO completions.
724 error
= dax_insert_mapping(inode
, &bh
, vma
, vmf
);
725 if (buffer_unwritten(&bh
)) {
726 if (complete_unwritten
)
727 complete_unwritten(&bh
, !error
);
729 WARN_ON_ONCE(!(vmf
->flags
& FAULT_FLAG_WRITE
));
733 if (error
== -ENOMEM
)
734 return VM_FAULT_OOM
| major
;
735 /* -EBUSY is fine, somebody else faulted on the same PTE */
736 if ((error
< 0) && (error
!= -EBUSY
))
737 return VM_FAULT_SIGBUS
| major
;
738 return VM_FAULT_NOPAGE
| major
;
743 page_cache_release(page
);
747 EXPORT_SYMBOL(__dax_fault
);
750 * dax_fault - handle a page fault on a DAX file
751 * @vma: The virtual memory area where the fault occurred
752 * @vmf: The description of the fault
753 * @get_block: The filesystem method used to translate file offsets to blocks
755 * When a page fault occurs, filesystems may call this helper in their
756 * fault handler for DAX files.
758 int dax_fault(struct vm_area_struct
*vma
, struct vm_fault
*vmf
,
759 get_block_t get_block
, dax_iodone_t complete_unwritten
)
762 struct super_block
*sb
= file_inode(vma
->vm_file
)->i_sb
;
764 if (vmf
->flags
& FAULT_FLAG_WRITE
) {
765 sb_start_pagefault(sb
);
766 file_update_time(vma
->vm_file
);
768 result
= __dax_fault(vma
, vmf
, get_block
, complete_unwritten
);
769 if (vmf
->flags
& FAULT_FLAG_WRITE
)
770 sb_end_pagefault(sb
);
774 EXPORT_SYMBOL_GPL(dax_fault
);
776 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
778 * The 'colour' (ie low bits) within a PMD of a page offset. This comes up
779 * more often than one might expect in the below function.
781 #define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1)
783 static void __dax_dbg(struct buffer_head
*bh
, unsigned long address
,
784 const char *reason
, const char *fn
)
787 char bname
[BDEVNAME_SIZE
];
788 bdevname(bh
->b_bdev
, bname
);
789 pr_debug("%s: %s addr: %lx dev %s state %lx start %lld "
790 "length %zd fallback: %s\n", fn
, current
->comm
,
791 address
, bname
, bh
->b_state
, (u64
)bh
->b_blocknr
,
794 pr_debug("%s: %s addr: %lx fallback: %s\n", fn
,
795 current
->comm
, address
, reason
);
799 #define dax_pmd_dbg(bh, address, reason) __dax_dbg(bh, address, reason, "dax_pmd")
801 int __dax_pmd_fault(struct vm_area_struct
*vma
, unsigned long address
,
802 pmd_t
*pmd
, unsigned int flags
, get_block_t get_block
,
803 dax_iodone_t complete_unwritten
)
805 struct file
*file
= vma
->vm_file
;
806 struct address_space
*mapping
= file
->f_mapping
;
807 struct inode
*inode
= mapping
->host
;
808 struct buffer_head bh
;
809 unsigned blkbits
= inode
->i_blkbits
;
810 unsigned long pmd_addr
= address
& PMD_MASK
;
811 bool write
= flags
& FAULT_FLAG_WRITE
;
812 struct block_device
*bdev
;
815 int error
, result
= 0;
818 /* dax pmd mappings require pfn_t_devmap() */
819 if (!IS_ENABLED(CONFIG_FS_DAX_PMD
))
820 return VM_FAULT_FALLBACK
;
822 /* Fall back to PTEs if we're going to COW */
823 if (write
&& !(vma
->vm_flags
& VM_SHARED
)) {
824 split_huge_pmd(vma
, pmd
, address
);
825 dax_pmd_dbg(NULL
, address
, "cow write");
826 return VM_FAULT_FALLBACK
;
828 /* If the PMD would extend outside the VMA */
829 if (pmd_addr
< vma
->vm_start
) {
830 dax_pmd_dbg(NULL
, address
, "vma start unaligned");
831 return VM_FAULT_FALLBACK
;
833 if ((pmd_addr
+ PMD_SIZE
) > vma
->vm_end
) {
834 dax_pmd_dbg(NULL
, address
, "vma end unaligned");
835 return VM_FAULT_FALLBACK
;
838 pgoff
= linear_page_index(vma
, pmd_addr
);
839 size
= (i_size_read(inode
) + PAGE_SIZE
- 1) >> PAGE_SHIFT
;
841 return VM_FAULT_SIGBUS
;
842 /* If the PMD would cover blocks out of the file */
843 if ((pgoff
| PG_PMD_COLOUR
) >= size
) {
844 dax_pmd_dbg(NULL
, address
,
845 "offset + huge page size > file size");
846 return VM_FAULT_FALLBACK
;
849 memset(&bh
, 0, sizeof(bh
));
850 bh
.b_bdev
= inode
->i_sb
->s_bdev
;
851 block
= (sector_t
)pgoff
<< (PAGE_SHIFT
- blkbits
);
853 bh
.b_size
= PMD_SIZE
;
855 if (get_block(inode
, block
, &bh
, 0) != 0)
856 return VM_FAULT_SIGBUS
;
858 if (!buffer_mapped(&bh
) && write
) {
859 if (get_block(inode
, block
, &bh
, 1) != 0)
860 return VM_FAULT_SIGBUS
;
867 * If the filesystem isn't willing to tell us the length of a hole,
868 * just fall back to PTEs. Calling get_block 512 times in a loop
871 if (!buffer_size_valid(&bh
) || bh
.b_size
< PMD_SIZE
) {
872 dax_pmd_dbg(&bh
, address
, "allocated block too small");
873 return VM_FAULT_FALLBACK
;
877 * If we allocated new storage, make sure no process has any
878 * zero pages covering this hole
881 loff_t lstart
= pgoff
<< PAGE_SHIFT
;
882 loff_t lend
= lstart
+ PMD_SIZE
- 1; /* inclusive */
884 truncate_pagecache_range(inode
, lstart
, lend
);
887 i_mmap_lock_read(mapping
);
890 * If a truncate happened while we were allocating blocks, we may
891 * leave blocks allocated to the file that are beyond EOF. We can't
892 * take i_mutex here, so just leave them hanging; they'll be freed
893 * when the file is deleted.
895 size
= (i_size_read(inode
) + PAGE_SIZE
- 1) >> PAGE_SHIFT
;
897 result
= VM_FAULT_SIGBUS
;
900 if ((pgoff
| PG_PMD_COLOUR
) >= size
) {
901 dax_pmd_dbg(&bh
, address
,
902 "offset + huge page size > file size");
906 if (!write
&& !buffer_mapped(&bh
) && buffer_uptodate(&bh
)) {
909 struct page
*zero_page
= get_huge_zero_page();
911 if (unlikely(!zero_page
)) {
912 dax_pmd_dbg(&bh
, address
, "no zero page");
916 ptl
= pmd_lock(vma
->vm_mm
, pmd
);
917 if (!pmd_none(*pmd
)) {
919 dax_pmd_dbg(&bh
, address
, "pmd already present");
923 dev_dbg(part_to_dev(bdev
->bd_part
),
924 "%s: %s addr: %lx pfn: <zero> sect: %llx\n",
925 __func__
, current
->comm
, address
,
926 (unsigned long long) to_sector(&bh
, inode
));
928 entry
= mk_pmd(zero_page
, vma
->vm_page_prot
);
929 entry
= pmd_mkhuge(entry
);
930 set_pmd_at(vma
->vm_mm
, pmd_addr
, pmd
, entry
);
931 result
= VM_FAULT_NOPAGE
;
934 struct blk_dax_ctl dax
= {
935 .sector
= to_sector(&bh
, inode
),
938 long length
= dax_map_atomic(bdev
, &dax
);
941 result
= VM_FAULT_SIGBUS
;
944 if (length
< PMD_SIZE
) {
945 dax_pmd_dbg(&bh
, address
, "dax-length too small");
946 dax_unmap_atomic(bdev
, &dax
);
949 if (pfn_t_to_pfn(dax
.pfn
) & PG_PMD_COLOUR
) {
950 dax_pmd_dbg(&bh
, address
, "pfn unaligned");
951 dax_unmap_atomic(bdev
, &dax
);
955 if (!pfn_t_devmap(dax
.pfn
)) {
956 dax_unmap_atomic(bdev
, &dax
);
957 dax_pmd_dbg(&bh
, address
, "pfn not in memmap");
961 if (buffer_unwritten(&bh
) || buffer_new(&bh
)) {
962 clear_pmem(dax
.addr
, PMD_SIZE
);
964 count_vm_event(PGMAJFAULT
);
965 mem_cgroup_count_vm_event(vma
->vm_mm
, PGMAJFAULT
);
966 result
|= VM_FAULT_MAJOR
;
968 dax_unmap_atomic(bdev
, &dax
);
971 * For PTE faults we insert a radix tree entry for reads, and
972 * leave it clean. Then on the first write we dirty the radix
973 * tree entry via the dax_pfn_mkwrite() path. This sequence
974 * allows the dax_pfn_mkwrite() call to be simpler and avoid a
975 * call into get_block() to translate the pgoff to a sector in
976 * order to be able to create a new radix tree entry.
978 * The PMD path doesn't have an equivalent to
979 * dax_pfn_mkwrite(), though, so for a read followed by a
980 * write we traverse all the way through __dax_pmd_fault()
981 * twice. This means we can just skip inserting a radix tree
982 * entry completely on the initial read and just wait until
983 * the write to insert a dirty entry.
986 error
= dax_radix_entry(mapping
, pgoff
, dax
.sector
,
989 dax_pmd_dbg(&bh
, address
,
990 "PMD radix insertion failed");
995 dev_dbg(part_to_dev(bdev
->bd_part
),
996 "%s: %s addr: %lx pfn: %lx sect: %llx\n",
997 __func__
, current
->comm
, address
,
998 pfn_t_to_pfn(dax
.pfn
),
999 (unsigned long long) dax
.sector
);
1000 result
|= vmf_insert_pfn_pmd(vma
, address
, pmd
,
1005 i_mmap_unlock_read(mapping
);
1007 if (buffer_unwritten(&bh
))
1008 complete_unwritten(&bh
, !(result
& VM_FAULT_ERROR
));
1013 count_vm_event(THP_FAULT_FALLBACK
);
1014 result
= VM_FAULT_FALLBACK
;
1017 EXPORT_SYMBOL_GPL(__dax_pmd_fault
);
1020 * dax_pmd_fault - handle a PMD fault on a DAX file
1021 * @vma: The virtual memory area where the fault occurred
1022 * @vmf: The description of the fault
1023 * @get_block: The filesystem method used to translate file offsets to blocks
1025 * When a page fault occurs, filesystems may call this helper in their
1026 * pmd_fault handler for DAX files.
1028 int dax_pmd_fault(struct vm_area_struct
*vma
, unsigned long address
,
1029 pmd_t
*pmd
, unsigned int flags
, get_block_t get_block
,
1030 dax_iodone_t complete_unwritten
)
1033 struct super_block
*sb
= file_inode(vma
->vm_file
)->i_sb
;
1035 if (flags
& FAULT_FLAG_WRITE
) {
1036 sb_start_pagefault(sb
);
1037 file_update_time(vma
->vm_file
);
1039 result
= __dax_pmd_fault(vma
, address
, pmd
, flags
, get_block
,
1040 complete_unwritten
);
1041 if (flags
& FAULT_FLAG_WRITE
)
1042 sb_end_pagefault(sb
);
1046 EXPORT_SYMBOL_GPL(dax_pmd_fault
);
1047 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
1050 * dax_pfn_mkwrite - handle first write to DAX page
1051 * @vma: The virtual memory area where the fault occurred
1052 * @vmf: The description of the fault
1054 int dax_pfn_mkwrite(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
1056 struct file
*file
= vma
->vm_file
;
1059 * We pass NO_SECTOR to dax_radix_entry() because we expect that a
1060 * RADIX_DAX_PTE entry already exists in the radix tree from a
1061 * previous call to __dax_fault(). We just want to look up that PTE
1062 * entry using vmf->pgoff and make sure the dirty tag is set. This
1063 * saves us from having to make a call to get_block() here to look
1066 dax_radix_entry(file
->f_mapping
, vmf
->pgoff
, NO_SECTOR
, false, true);
1067 return VM_FAULT_NOPAGE
;
1069 EXPORT_SYMBOL_GPL(dax_pfn_mkwrite
);
1072 * dax_zero_page_range - zero a range within a page of a DAX file
1073 * @inode: The file being truncated
1074 * @from: The file offset that is being truncated to
1075 * @length: The number of bytes to zero
1076 * @get_block: The filesystem method used to translate file offsets to blocks
1078 * This function can be called by a filesystem when it is zeroing part of a
1079 * page in a DAX file. This is intended for hole-punch operations. If
1080 * you are truncating a file, the helper function dax_truncate_page() may be
1083 * We work in terms of PAGE_CACHE_SIZE here for commonality with
1084 * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
1085 * took care of disposing of the unnecessary blocks. Even if the filesystem
1086 * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
1087 * since the file might be mmapped.
1089 int dax_zero_page_range(struct inode
*inode
, loff_t from
, unsigned length
,
1090 get_block_t get_block
)
1092 struct buffer_head bh
;
1093 pgoff_t index
= from
>> PAGE_CACHE_SHIFT
;
1094 unsigned offset
= from
& (PAGE_CACHE_SIZE
-1);
1097 /* Block boundary? Nothing to do */
1100 BUG_ON((offset
+ length
) > PAGE_CACHE_SIZE
);
1102 memset(&bh
, 0, sizeof(bh
));
1103 bh
.b_bdev
= inode
->i_sb
->s_bdev
;
1104 bh
.b_size
= PAGE_CACHE_SIZE
;
1105 err
= get_block(inode
, index
, &bh
, 0);
1108 if (buffer_written(&bh
)) {
1109 struct block_device
*bdev
= bh
.b_bdev
;
1110 struct blk_dax_ctl dax
= {
1111 .sector
= to_sector(&bh
, inode
),
1112 .size
= PAGE_CACHE_SIZE
,
1115 if (dax_map_atomic(bdev
, &dax
) < 0)
1116 return PTR_ERR(dax
.addr
);
1117 clear_pmem(dax
.addr
+ offset
, length
);
1119 dax_unmap_atomic(bdev
, &dax
);
1124 EXPORT_SYMBOL_GPL(dax_zero_page_range
);
1127 * dax_truncate_page - handle a partial page being truncated in a DAX file
1128 * @inode: The file being truncated
1129 * @from: The file offset that is being truncated to
1130 * @get_block: The filesystem method used to translate file offsets to blocks
1132 * Similar to block_truncate_page(), this function can be called by a
1133 * filesystem when it is truncating a DAX file to handle the partial page.
1135 * We work in terms of PAGE_CACHE_SIZE here for commonality with
1136 * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
1137 * took care of disposing of the unnecessary blocks. Even if the filesystem
1138 * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
1139 * since the file might be mmapped.
1141 int dax_truncate_page(struct inode
*inode
, loff_t from
, get_block_t get_block
)
1143 unsigned length
= PAGE_CACHE_ALIGN(from
) - from
;
1144 return dax_zero_page_range(inode
, from
, length
, get_block
);
1146 EXPORT_SYMBOL_GPL(dax_truncate_page
);