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>
34 #include <linux/iomap.h>
37 /* We choose 4096 entries - same as per-zone page wait tables */
38 #define DAX_WAIT_TABLE_BITS 12
39 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
41 static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
43 static int __init init_dax_wait_table(void)
47 for (i = 0; i < DAX_WAIT_TABLE_ENTRIES; i++)
48 init_waitqueue_head(wait_table + i);
51 fs_initcall(init_dax_wait_table);
53 static long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax)
55 struct request_queue *q = bdev->bd_queue;
58 dax->addr = ERR_PTR(-EIO);
59 if (blk_queue_enter(q, true) != 0)
62 rc = bdev_direct_access(bdev, dax);
64 dax->addr = ERR_PTR(rc);
71 static void dax_unmap_atomic(struct block_device *bdev,
72 const struct blk_dax_ctl *dax)
74 if (IS_ERR(dax->addr))
76 blk_queue_exit(bdev->bd_queue);
79 static int dax_is_pmd_entry(void *entry)
81 return (unsigned long)entry & RADIX_DAX_PMD;
84 static int dax_is_pte_entry(void *entry)
86 return !((unsigned long)entry & RADIX_DAX_PMD);
89 static int dax_is_zero_entry(void *entry)
91 return (unsigned long)entry & RADIX_DAX_HZP;
94 static int dax_is_empty_entry(void *entry)
96 return (unsigned long)entry & RADIX_DAX_EMPTY;
99 struct page *read_dax_sector(struct block_device *bdev, sector_t n)
101 struct page *page = alloc_pages(GFP_KERNEL, 0);
102 struct blk_dax_ctl dax = {
104 .sector = n & ~((((int) PAGE_SIZE) / 512) - 1),
109 return ERR_PTR(-ENOMEM);
111 rc = dax_map_atomic(bdev, &dax);
114 memcpy_from_pmem(page_address(page), dax.addr, PAGE_SIZE);
115 dax_unmap_atomic(bdev, &dax);
120 * DAX radix tree locking
122 struct exceptional_entry_key {
123 struct address_space *mapping;
127 struct wait_exceptional_entry_queue {
129 struct exceptional_entry_key key;
132 static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
133 pgoff_t index, void *entry, struct exceptional_entry_key *key)
138 * If 'entry' is a PMD, align the 'index' that we use for the wait
139 * queue to the start of that PMD. This ensures that all offsets in
140 * the range covered by the PMD map to the same bit lock.
142 if (dax_is_pmd_entry(entry))
143 index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
145 key->mapping = mapping;
146 key->entry_start = index;
148 hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS);
149 return wait_table + hash;
152 static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode,
153 int sync, void *keyp)
155 struct exceptional_entry_key *key = keyp;
156 struct wait_exceptional_entry_queue *ewait =
157 container_of(wait, struct wait_exceptional_entry_queue, wait);
159 if (key->mapping != ewait->key.mapping ||
160 key->entry_start != ewait->key.entry_start)
162 return autoremove_wake_function(wait, mode, sync, NULL);
166 * Check whether the given slot is locked. The function must be called with
167 * mapping->tree_lock held
169 static inline int slot_locked(struct address_space *mapping, void **slot)
171 unsigned long entry = (unsigned long)
172 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
173 return entry & RADIX_DAX_ENTRY_LOCK;
177 * Mark the given slot is locked. The function must be called with
178 * mapping->tree_lock held
180 static inline void *lock_slot(struct address_space *mapping, void **slot)
182 unsigned long entry = (unsigned long)
183 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
185 entry |= RADIX_DAX_ENTRY_LOCK;
186 radix_tree_replace_slot(&mapping->page_tree, slot, (void *)entry);
187 return (void *)entry;
191 * Mark the given slot is unlocked. The function must be called with
192 * mapping->tree_lock held
194 static inline void *unlock_slot(struct address_space *mapping, void **slot)
196 unsigned long entry = (unsigned long)
197 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
199 entry &= ~(unsigned long)RADIX_DAX_ENTRY_LOCK;
200 radix_tree_replace_slot(&mapping->page_tree, slot, (void *)entry);
201 return (void *)entry;
205 * Lookup entry in radix tree, wait for it to become unlocked if it is
206 * exceptional entry and return it. The caller must call
207 * put_unlocked_mapping_entry() when he decided not to lock the entry or
208 * put_locked_mapping_entry() when he locked the entry and now wants to
211 * The function must be called with mapping->tree_lock held.
213 static void *get_unlocked_mapping_entry(struct address_space *mapping,
214 pgoff_t index, void ***slotp)
217 struct wait_exceptional_entry_queue ewait;
218 wait_queue_head_t *wq;
220 init_wait(&ewait.wait);
221 ewait.wait.func = wake_exceptional_entry_func;
224 entry = __radix_tree_lookup(&mapping->page_tree, index, NULL,
226 if (!entry || !radix_tree_exceptional_entry(entry) ||
227 !slot_locked(mapping, slot)) {
233 wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
234 prepare_to_wait_exclusive(wq, &ewait.wait,
235 TASK_UNINTERRUPTIBLE);
236 spin_unlock_irq(&mapping->tree_lock);
238 finish_wait(wq, &ewait.wait);
239 spin_lock_irq(&mapping->tree_lock);
243 static void put_locked_mapping_entry(struct address_space *mapping,
244 pgoff_t index, void *entry)
246 if (!radix_tree_exceptional_entry(entry)) {
250 dax_unlock_mapping_entry(mapping, index);
255 * Called when we are done with radix tree entry we looked up via
256 * get_unlocked_mapping_entry() and which we didn't lock in the end.
258 static void put_unlocked_mapping_entry(struct address_space *mapping,
259 pgoff_t index, void *entry)
261 if (!radix_tree_exceptional_entry(entry))
264 /* We have to wake up next waiter for the radix tree entry lock */
265 dax_wake_mapping_entry_waiter(mapping, index, entry, false);
269 * Find radix tree entry at given index. If it points to a page, return with
270 * the page locked. If it points to the exceptional entry, return with the
271 * radix tree entry locked. If the radix tree doesn't contain given index,
272 * create empty exceptional entry for the index and return with it locked.
274 * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
275 * either return that locked entry or will return an error. This error will
276 * happen if there are any 4k entries (either zero pages or DAX entries)
277 * within the 2MiB range that we are requesting.
279 * We always favor 4k entries over 2MiB entries. There isn't a flow where we
280 * evict 4k entries in order to 'upgrade' them to a 2MiB entry. A 2MiB
281 * insertion will fail if it finds any 4k entries already in the tree, and a
282 * 4k insertion will cause an existing 2MiB entry to be unmapped and
283 * downgraded to 4k entries. This happens for both 2MiB huge zero pages as
284 * well as 2MiB empty entries.
286 * The exception to this downgrade path is for 2MiB DAX PMD entries that have
287 * real storage backing them. We will leave these real 2MiB DAX entries in
288 * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
290 * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
291 * persistent memory the benefit is doubtful. We can add that later if we can
294 static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
295 unsigned long size_flag)
297 bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
301 spin_lock_irq(&mapping->tree_lock);
302 entry = get_unlocked_mapping_entry(mapping, index, &slot);
305 if (size_flag & RADIX_DAX_PMD) {
306 if (!radix_tree_exceptional_entry(entry) ||
307 dax_is_pte_entry(entry)) {
308 put_unlocked_mapping_entry(mapping, index,
310 entry = ERR_PTR(-EEXIST);
313 } else { /* trying to grab a PTE entry */
314 if (radix_tree_exceptional_entry(entry) &&
315 dax_is_pmd_entry(entry) &&
316 (dax_is_zero_entry(entry) ||
317 dax_is_empty_entry(entry))) {
318 pmd_downgrade = true;
323 /* No entry for given index? Make sure radix tree is big enough. */
324 if (!entry || pmd_downgrade) {
329 * Make sure 'entry' remains valid while we drop
330 * mapping->tree_lock.
332 entry = lock_slot(mapping, slot);
335 spin_unlock_irq(&mapping->tree_lock);
337 * Besides huge zero pages the only other thing that gets
338 * downgraded are empty entries which don't need to be
341 if (pmd_downgrade && dax_is_zero_entry(entry))
342 unmap_mapping_range(mapping,
343 (index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
345 err = radix_tree_preload(
346 mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
349 put_locked_mapping_entry(mapping, index, entry);
352 spin_lock_irq(&mapping->tree_lock);
355 radix_tree_delete(&mapping->page_tree, index);
356 mapping->nrexceptional--;
357 dax_wake_mapping_entry_waiter(mapping, index, entry,
361 entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
363 err = __radix_tree_insert(&mapping->page_tree, index,
364 dax_radix_order(entry), entry);
365 radix_tree_preload_end();
367 spin_unlock_irq(&mapping->tree_lock);
369 * Someone already created the entry? This is a
370 * normal failure when inserting PMDs in a range
371 * that already contains PTEs. In that case we want
372 * to return -EEXIST immediately.
374 if (err == -EEXIST && !(size_flag & RADIX_DAX_PMD))
377 * Our insertion of a DAX PMD entry failed, most
378 * likely because it collided with a PTE sized entry
379 * at a different index in the PMD range. We haven't
380 * inserted anything into the radix tree and have no
385 /* Good, we have inserted empty locked entry into the tree. */
386 mapping->nrexceptional++;
387 spin_unlock_irq(&mapping->tree_lock);
390 /* Normal page in radix tree? */
391 if (!radix_tree_exceptional_entry(entry)) {
392 struct page *page = entry;
395 spin_unlock_irq(&mapping->tree_lock);
397 /* Page got truncated? Retry... */
398 if (unlikely(page->mapping != mapping)) {
405 entry = lock_slot(mapping, slot);
407 spin_unlock_irq(&mapping->tree_lock);
412 * We do not necessarily hold the mapping->tree_lock when we call this
413 * function so it is possible that 'entry' is no longer a valid item in the
414 * radix tree. This is okay because all we really need to do is to find the
415 * correct waitqueue where tasks might be waiting for that old 'entry' and
418 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
419 pgoff_t index, void *entry, bool wake_all)
421 struct exceptional_entry_key key;
422 wait_queue_head_t *wq;
424 wq = dax_entry_waitqueue(mapping, index, entry, &key);
427 * Checking for locked entry and prepare_to_wait_exclusive() happens
428 * under mapping->tree_lock, ditto for entry handling in our callers.
429 * So at this point all tasks that could have seen our entry locked
430 * must be in the waitqueue and the following check will see them.
432 if (waitqueue_active(wq))
433 __wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
436 void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
440 spin_lock_irq(&mapping->tree_lock);
441 entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
442 if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) ||
443 !slot_locked(mapping, slot))) {
444 spin_unlock_irq(&mapping->tree_lock);
447 unlock_slot(mapping, slot);
448 spin_unlock_irq(&mapping->tree_lock);
449 dax_wake_mapping_entry_waiter(mapping, index, entry, false);
453 * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
454 * entry to get unlocked before deleting it.
456 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
460 spin_lock_irq(&mapping->tree_lock);
461 entry = get_unlocked_mapping_entry(mapping, index, NULL);
463 * This gets called from truncate / punch_hole path. As such, the caller
464 * must hold locks protecting against concurrent modifications of the
465 * radix tree (usually fs-private i_mmap_sem for writing). Since the
466 * caller has seen exceptional entry for this index, we better find it
467 * at that index as well...
469 if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry))) {
470 spin_unlock_irq(&mapping->tree_lock);
473 radix_tree_delete(&mapping->page_tree, index);
474 mapping->nrexceptional--;
475 spin_unlock_irq(&mapping->tree_lock);
476 dax_wake_mapping_entry_waiter(mapping, index, entry, true);
482 * The user has performed a load from a hole in the file. Allocating
483 * a new page in the file would cause excessive storage usage for
484 * workloads with sparse files. We allocate a page cache page instead.
485 * We'll kick it out of the page cache if it's ever written to,
486 * otherwise it will simply fall out of the page cache under memory
487 * pressure without ever having been dirtied.
489 static int dax_load_hole(struct address_space *mapping, void *entry,
490 struct vm_fault *vmf)
494 /* Hole page already exists? Return it... */
495 if (!radix_tree_exceptional_entry(entry)) {
497 return VM_FAULT_LOCKED;
500 /* This will replace locked radix tree entry with a hole page */
501 page = find_or_create_page(mapping, vmf->pgoff,
502 vmf->gfp_mask | __GFP_ZERO);
504 put_locked_mapping_entry(mapping, vmf->pgoff, entry);
508 return VM_FAULT_LOCKED;
511 static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size,
512 struct page *to, unsigned long vaddr)
514 struct blk_dax_ctl dax = {
520 if (dax_map_atomic(bdev, &dax) < 0)
521 return PTR_ERR(dax.addr);
522 vto = kmap_atomic(to);
523 copy_user_page(vto, (void __force *)dax.addr, vaddr, to);
525 dax_unmap_atomic(bdev, &dax);
530 * By this point grab_mapping_entry() has ensured that we have a locked entry
531 * of the appropriate size so we don't have to worry about downgrading PMDs to
532 * PTEs. If we happen to be trying to insert a PTE and there is a PMD
533 * already in the tree, we will skip the insertion and just dirty the PMD as
536 static void *dax_insert_mapping_entry(struct address_space *mapping,
537 struct vm_fault *vmf,
538 void *entry, sector_t sector,
541 struct radix_tree_root *page_tree = &mapping->page_tree;
543 bool hole_fill = false;
545 pgoff_t index = vmf->pgoff;
547 if (vmf->flags & FAULT_FLAG_WRITE)
548 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
550 /* Replacing hole page with block mapping? */
551 if (!radix_tree_exceptional_entry(entry)) {
554 * Unmap the page now before we remove it from page cache below.
555 * The page is locked so it cannot be faulted in again.
557 unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
559 error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM);
561 return ERR_PTR(error);
562 } else if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_HZP)) {
563 /* replacing huge zero page with PMD block mapping */
564 unmap_mapping_range(mapping,
565 (vmf->pgoff << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
568 spin_lock_irq(&mapping->tree_lock);
569 new_entry = dax_radix_locked_entry(sector, flags);
572 __delete_from_page_cache(entry, NULL);
573 /* Drop pagecache reference */
575 error = __radix_tree_insert(page_tree, index,
576 dax_radix_order(new_entry), new_entry);
578 new_entry = ERR_PTR(error);
581 mapping->nrexceptional++;
582 } else if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
584 * Only swap our new entry into the radix tree if the current
585 * entry is a zero page or an empty entry. If a normal PTE or
586 * PMD entry is already in the tree, we leave it alone. This
587 * means that if we are trying to insert a PTE and the
588 * existing entry is a PMD, we will just leave the PMD in the
589 * tree and dirty it if necessary.
591 struct radix_tree_node *node;
595 ret = __radix_tree_lookup(page_tree, index, &node, &slot);
596 WARN_ON_ONCE(ret != entry);
597 __radix_tree_replace(page_tree, node, slot,
598 new_entry, NULL, NULL);
600 if (vmf->flags & FAULT_FLAG_WRITE)
601 radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);
603 spin_unlock_irq(&mapping->tree_lock);
605 radix_tree_preload_end();
607 * We don't need hole page anymore, it has been replaced with
608 * locked radix tree entry now.
610 if (mapping->a_ops->freepage)
611 mapping->a_ops->freepage(entry);
618 static int dax_writeback_one(struct block_device *bdev,
619 struct address_space *mapping, pgoff_t index, void *entry)
621 struct radix_tree_root *page_tree = &mapping->page_tree;
622 struct radix_tree_node *node;
623 struct blk_dax_ctl dax;
627 spin_lock_irq(&mapping->tree_lock);
629 * Regular page slots are stabilized by the page lock even
630 * without the tree itself locked. These unlocked entries
631 * need verification under the tree lock.
633 if (!__radix_tree_lookup(page_tree, index, &node, &slot))
638 /* another fsync thread may have already written back this entry */
639 if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
642 if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
643 dax_is_zero_entry(entry))) {
649 * Even if dax_writeback_mapping_range() was given a wbc->range_start
650 * in the middle of a PMD, the 'index' we are given will be aligned to
651 * the start index of the PMD, as will the sector we pull from
652 * 'entry'. This allows us to flush for PMD_SIZE and not have to
653 * worry about partial PMD writebacks.
655 dax.sector = dax_radix_sector(entry);
656 dax.size = PAGE_SIZE << dax_radix_order(entry);
657 spin_unlock_irq(&mapping->tree_lock);
660 * We cannot hold tree_lock while calling dax_map_atomic() because it
661 * eventually calls cond_resched().
663 ret = dax_map_atomic(bdev, &dax);
667 if (WARN_ON_ONCE(ret < dax.size)) {
672 wb_cache_pmem(dax.addr, dax.size);
674 spin_lock_irq(&mapping->tree_lock);
675 radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE);
676 spin_unlock_irq(&mapping->tree_lock);
678 dax_unmap_atomic(bdev, &dax);
682 spin_unlock_irq(&mapping->tree_lock);
687 * Flush the mapping to the persistent domain within the byte range of [start,
688 * end]. This is required by data integrity operations to ensure file data is
689 * on persistent storage prior to completion of the operation.
691 int dax_writeback_mapping_range(struct address_space *mapping,
692 struct block_device *bdev, struct writeback_control *wbc)
694 struct inode *inode = mapping->host;
695 pgoff_t start_index, end_index;
696 pgoff_t indices[PAGEVEC_SIZE];
701 if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
704 if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
707 start_index = wbc->range_start >> PAGE_SHIFT;
708 end_index = wbc->range_end >> PAGE_SHIFT;
710 tag_pages_for_writeback(mapping, start_index, end_index);
712 pagevec_init(&pvec, 0);
714 pvec.nr = find_get_entries_tag(mapping, start_index,
715 PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE,
716 pvec.pages, indices);
721 for (i = 0; i < pvec.nr; i++) {
722 if (indices[i] > end_index) {
727 ret = dax_writeback_one(bdev, mapping, indices[i],
735 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
737 static int dax_insert_mapping(struct address_space *mapping,
738 struct block_device *bdev, sector_t sector, size_t size,
739 void **entryp, struct vm_area_struct *vma, struct vm_fault *vmf)
741 unsigned long vaddr = (unsigned long)vmf->virtual_address;
742 struct blk_dax_ctl dax = {
747 void *entry = *entryp;
749 if (dax_map_atomic(bdev, &dax) < 0)
750 return PTR_ERR(dax.addr);
751 dax_unmap_atomic(bdev, &dax);
753 ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector, 0);
758 return vm_insert_mixed(vma, vaddr, dax.pfn);
762 * dax_pfn_mkwrite - handle first write to DAX page
763 * @vma: The virtual memory area where the fault occurred
764 * @vmf: The description of the fault
766 int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
768 struct file *file = vma->vm_file;
769 struct address_space *mapping = file->f_mapping;
771 pgoff_t index = vmf->pgoff;
773 spin_lock_irq(&mapping->tree_lock);
774 entry = get_unlocked_mapping_entry(mapping, index, NULL);
775 if (!entry || !radix_tree_exceptional_entry(entry))
777 radix_tree_tag_set(&mapping->page_tree, index, PAGECACHE_TAG_DIRTY);
778 put_unlocked_mapping_entry(mapping, index, entry);
780 spin_unlock_irq(&mapping->tree_lock);
781 return VM_FAULT_NOPAGE;
783 EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
785 static bool dax_range_is_aligned(struct block_device *bdev,
786 unsigned int offset, unsigned int length)
788 unsigned short sector_size = bdev_logical_block_size(bdev);
790 if (!IS_ALIGNED(offset, sector_size))
792 if (!IS_ALIGNED(length, sector_size))
798 int __dax_zero_page_range(struct block_device *bdev, sector_t sector,
799 unsigned int offset, unsigned int length)
801 struct blk_dax_ctl dax = {
806 if (dax_range_is_aligned(bdev, offset, length)) {
807 sector_t start_sector = dax.sector + (offset >> 9);
809 return blkdev_issue_zeroout(bdev, start_sector,
810 length >> 9, GFP_NOFS, true);
812 if (dax_map_atomic(bdev, &dax) < 0)
813 return PTR_ERR(dax.addr);
814 clear_pmem(dax.addr + offset, length);
815 dax_unmap_atomic(bdev, &dax);
819 EXPORT_SYMBOL_GPL(__dax_zero_page_range);
821 #ifdef CONFIG_FS_IOMAP
822 static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
824 return iomap->blkno + (((pos & PAGE_MASK) - iomap->offset) >> 9);
828 dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
831 struct iov_iter *iter = data;
832 loff_t end = pos + length, done = 0;
835 if (iov_iter_rw(iter) == READ) {
836 end = min(end, i_size_read(inode));
840 if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
841 return iov_iter_zero(min(length, end - pos), iter);
844 if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED))
848 unsigned offset = pos & (PAGE_SIZE - 1);
849 struct blk_dax_ctl dax = { 0 };
852 dax.sector = dax_iomap_sector(iomap, pos);
853 dax.size = (length + offset + PAGE_SIZE - 1) & PAGE_MASK;
854 map_len = dax_map_atomic(iomap->bdev, &dax);
862 if (map_len > end - pos)
865 if (iov_iter_rw(iter) == WRITE)
866 map_len = copy_from_iter_pmem(dax.addr, map_len, iter);
868 map_len = copy_to_iter(dax.addr, map_len, iter);
869 dax_unmap_atomic(iomap->bdev, &dax);
871 ret = map_len ? map_len : -EFAULT;
880 return done ? done : ret;
884 * dax_iomap_rw - Perform I/O to a DAX file
885 * @iocb: The control block for this I/O
886 * @iter: The addresses to do I/O from or to
887 * @ops: iomap ops passed from the file system
889 * This function performs read and write operations to directly mapped
890 * persistent memory. The callers needs to take care of read/write exclusion
891 * and evicting any page cache pages in the region under I/O.
894 dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
895 struct iomap_ops *ops)
897 struct address_space *mapping = iocb->ki_filp->f_mapping;
898 struct inode *inode = mapping->host;
899 loff_t pos = iocb->ki_pos, ret = 0, done = 0;
902 if (iov_iter_rw(iter) == WRITE)
903 flags |= IOMAP_WRITE;
906 * Yes, even DAX files can have page cache attached to them: A zeroed
907 * page is inserted into the pagecache when we have to serve a write
908 * fault on a hole. It should never be dirtied and can simply be
909 * dropped from the pagecache once we get real data for the page.
911 * XXX: This is racy against mmap, and there's nothing we can do about
912 * it. We'll eventually need to shift this down even further so that
913 * we can check if we allocated blocks over a hole first.
915 if (mapping->nrpages) {
916 ret = invalidate_inode_pages2_range(mapping,
918 (pos + iov_iter_count(iter) - 1) >> PAGE_SHIFT);
922 while (iov_iter_count(iter)) {
923 ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
924 iter, dax_iomap_actor);
931 iocb->ki_pos += done;
932 return done ? done : ret;
934 EXPORT_SYMBOL_GPL(dax_iomap_rw);
937 * dax_iomap_fault - handle a page fault on a DAX file
938 * @vma: The virtual memory area where the fault occurred
939 * @vmf: The description of the fault
940 * @ops: iomap ops passed from the file system
942 * When a page fault occurs, filesystems may call this helper in their fault
943 * or mkwrite handler for DAX files. Assumes the caller has done all the
944 * necessary locking for the page fault to proceed successfully.
946 int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
947 struct iomap_ops *ops)
949 struct address_space *mapping = vma->vm_file->f_mapping;
950 struct inode *inode = mapping->host;
951 unsigned long vaddr = (unsigned long)vmf->virtual_address;
952 loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
954 struct iomap iomap = { 0 };
955 unsigned flags = IOMAP_FAULT;
956 int error, major = 0;
957 int locked_status = 0;
961 * Check whether offset isn't beyond end of file now. Caller is supposed
962 * to hold locks serializing us with truncate / punch hole so this is
965 if (pos >= i_size_read(inode))
966 return VM_FAULT_SIGBUS;
968 entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
970 error = PTR_ERR(entry);
974 if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page)
975 flags |= IOMAP_WRITE;
978 * Note that we don't bother to use iomap_apply here: DAX required
979 * the file system block size to be equal the page size, which means
980 * that we never have to deal with more than a single extent here.
982 error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap);
985 if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
986 error = -EIO; /* fs corruption? */
990 sector = dax_iomap_sector(&iomap, pos);
993 switch (iomap.type) {
995 case IOMAP_UNWRITTEN:
996 clear_user_highpage(vmf->cow_page, vaddr);
999 error = copy_user_dax(iomap.bdev, sector, PAGE_SIZE,
1000 vmf->cow_page, vaddr);
1010 if (!radix_tree_exceptional_entry(entry)) {
1012 locked_status = VM_FAULT_LOCKED;
1015 locked_status = VM_FAULT_DAX_LOCKED;
1020 switch (iomap.type) {
1022 if (iomap.flags & IOMAP_F_NEW) {
1023 count_vm_event(PGMAJFAULT);
1024 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1025 major = VM_FAULT_MAJOR;
1027 error = dax_insert_mapping(mapping, iomap.bdev, sector,
1028 PAGE_SIZE, &entry, vma, vmf);
1030 case IOMAP_UNWRITTEN:
1032 if (!(vmf->flags & FAULT_FLAG_WRITE)) {
1033 locked_status = dax_load_hole(mapping, entry, vmf);
1044 if (ops->iomap_end) {
1046 /* keep previous error */
1047 ops->iomap_end(inode, pos, PAGE_SIZE, 0, flags,
1050 error = ops->iomap_end(inode, pos, PAGE_SIZE,
1051 PAGE_SIZE, flags, &iomap);
1055 if (!locked_status || error)
1056 put_locked_mapping_entry(mapping, vmf->pgoff, entry);
1058 if (error == -ENOMEM)
1059 return VM_FAULT_OOM | major;
1060 /* -EBUSY is fine, somebody else faulted on the same PTE */
1061 if (error < 0 && error != -EBUSY)
1062 return VM_FAULT_SIGBUS | major;
1063 if (locked_status) {
1064 WARN_ON_ONCE(error); /* -EBUSY from ops->iomap_end? */
1065 return locked_status;
1067 return VM_FAULT_NOPAGE | major;
1069 EXPORT_SYMBOL_GPL(dax_iomap_fault);
1071 #ifdef CONFIG_FS_DAX_PMD
1073 * The 'colour' (ie low bits) within a PMD of a page offset. This comes up
1074 * more often than one might expect in the below functions.
1076 #define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1)
1078 static int dax_pmd_insert_mapping(struct vm_area_struct *vma, pmd_t *pmd,
1079 struct vm_fault *vmf, unsigned long address,
1080 struct iomap *iomap, loff_t pos, bool write, void **entryp)
1082 struct address_space *mapping = vma->vm_file->f_mapping;
1083 struct block_device *bdev = iomap->bdev;
1084 struct blk_dax_ctl dax = {
1085 .sector = dax_iomap_sector(iomap, pos),
1088 long length = dax_map_atomic(bdev, &dax);
1091 if (length < 0) /* dax_map_atomic() failed */
1092 return VM_FAULT_FALLBACK;
1093 if (length < PMD_SIZE)
1094 goto unmap_fallback;
1095 if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR)
1096 goto unmap_fallback;
1097 if (!pfn_t_devmap(dax.pfn))
1098 goto unmap_fallback;
1100 dax_unmap_atomic(bdev, &dax);
1102 ret = dax_insert_mapping_entry(mapping, vmf, *entryp, dax.sector,
1105 return VM_FAULT_FALLBACK;
1108 return vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write);
1111 dax_unmap_atomic(bdev, &dax);
1112 return VM_FAULT_FALLBACK;
1115 static int dax_pmd_load_hole(struct vm_area_struct *vma, pmd_t *pmd,
1116 struct vm_fault *vmf, unsigned long address,
1117 struct iomap *iomap, void **entryp)
1119 struct address_space *mapping = vma->vm_file->f_mapping;
1120 unsigned long pmd_addr = address & PMD_MASK;
1121 struct page *zero_page;
1126 zero_page = mm_get_huge_zero_page(vma->vm_mm);
1128 if (unlikely(!zero_page))
1129 return VM_FAULT_FALLBACK;
1131 ret = dax_insert_mapping_entry(mapping, vmf, *entryp, 0,
1132 RADIX_DAX_PMD | RADIX_DAX_HZP);
1134 return VM_FAULT_FALLBACK;
1137 ptl = pmd_lock(vma->vm_mm, pmd);
1138 if (!pmd_none(*pmd)) {
1140 return VM_FAULT_FALLBACK;
1143 pmd_entry = mk_pmd(zero_page, vma->vm_page_prot);
1144 pmd_entry = pmd_mkhuge(pmd_entry);
1145 set_pmd_at(vma->vm_mm, pmd_addr, pmd, pmd_entry);
1147 return VM_FAULT_NOPAGE;
1150 int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
1151 pmd_t *pmd, unsigned int flags, struct iomap_ops *ops)
1153 struct address_space *mapping = vma->vm_file->f_mapping;
1154 unsigned long pmd_addr = address & PMD_MASK;
1155 bool write = flags & FAULT_FLAG_WRITE;
1156 unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT;
1157 struct inode *inode = mapping->host;
1158 int result = VM_FAULT_FALLBACK;
1159 struct iomap iomap = { 0 };
1160 pgoff_t max_pgoff, pgoff;
1161 struct vm_fault vmf;
1166 /* Fall back to PTEs if we're going to COW */
1167 if (write && !(vma->vm_flags & VM_SHARED))
1170 /* If the PMD would extend outside the VMA */
1171 if (pmd_addr < vma->vm_start)
1173 if ((pmd_addr + PMD_SIZE) > vma->vm_end)
1177 * Check whether offset isn't beyond end of file now. Caller is
1178 * supposed to hold locks serializing us with truncate / punch hole so
1179 * this is a reliable test.
1181 pgoff = linear_page_index(vma, pmd_addr);
1182 max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
1184 if (pgoff > max_pgoff)
1185 return VM_FAULT_SIGBUS;
1187 /* If the PMD would extend beyond the file size */
1188 if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
1192 * grab_mapping_entry() will make sure we get a 2M empty entry, a DAX
1193 * PMD or a HZP entry. If it can't (because a 4k page is already in
1194 * the tree, for instance), it will return -EEXIST and we just fall
1195 * back to 4k entries.
1197 entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
1202 * Note that we don't use iomap_apply here. We aren't doing I/O, only
1203 * setting up a mapping, so really we're using iomap_begin() as a way
1204 * to look up our filesystem block.
1206 pos = (loff_t)pgoff << PAGE_SHIFT;
1207 error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
1210 if (iomap.offset + iomap.length < pos + PMD_SIZE)
1215 vmf.gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
1217 switch (iomap.type) {
1219 result = dax_pmd_insert_mapping(vma, pmd, &vmf, address,
1220 &iomap, pos, write, &entry);
1222 case IOMAP_UNWRITTEN:
1224 if (WARN_ON_ONCE(write))
1226 result = dax_pmd_load_hole(vma, pmd, &vmf, address, &iomap,
1235 if (ops->iomap_end) {
1236 if (result == VM_FAULT_FALLBACK) {
1237 ops->iomap_end(inode, pos, PMD_SIZE, 0, iomap_flags,
1240 error = ops->iomap_end(inode, pos, PMD_SIZE, PMD_SIZE,
1241 iomap_flags, &iomap);
1243 result = VM_FAULT_FALLBACK;
1247 put_locked_mapping_entry(mapping, pgoff, entry);
1249 if (result == VM_FAULT_FALLBACK) {
1250 split_huge_pmd(vma, pmd, address);
1251 count_vm_event(THP_FAULT_FALLBACK);
1255 EXPORT_SYMBOL_GPL(dax_iomap_pmd_fault);
1256 #endif /* CONFIG_FS_DAX_PMD */
1257 #endif /* CONFIG_FS_IOMAP */