/* * fs/dax.c - Direct Access filesystem code * Copyright (c) 2013-2014 Intel Corporation * Author: Matthew Wilcox * Author: Ross Zwisler * * 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "internal.h" #define CREATE_TRACE_POINTS #include /* We choose 4096 entries - same as per-zone page wait tables */ #define DAX_WAIT_TABLE_BITS 12 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS) static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES]; static int __init init_dax_wait_table(void) { int i; for (i = 0; i < DAX_WAIT_TABLE_ENTRIES; i++) init_waitqueue_head(wait_table + i); return 0; } fs_initcall(init_dax_wait_table); static int dax_is_pmd_entry(void *entry) { return (unsigned long)entry & RADIX_DAX_PMD; } static int dax_is_pte_entry(void *entry) { return !((unsigned long)entry & RADIX_DAX_PMD); } static int dax_is_zero_entry(void *entry) { return (unsigned long)entry & RADIX_DAX_ZERO_PAGE; } static int dax_is_empty_entry(void *entry) { return (unsigned long)entry & RADIX_DAX_EMPTY; } /* * DAX radix tree locking */ struct exceptional_entry_key { struct address_space *mapping; pgoff_t entry_start; }; struct wait_exceptional_entry_queue { wait_queue_entry_t wait; struct exceptional_entry_key key; }; static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping, pgoff_t index, void *entry, struct exceptional_entry_key *key) { unsigned long hash; /* * If 'entry' is a PMD, align the 'index' that we use for the wait * queue to the start of that PMD. This ensures that all offsets in * the range covered by the PMD map to the same bit lock. */ if (dax_is_pmd_entry(entry)) index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1); key->mapping = mapping; key->entry_start = index; hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS); return wait_table + hash; } static int wake_exceptional_entry_func(wait_queue_entry_t *wait, unsigned int mode, int sync, void *keyp) { struct exceptional_entry_key *key = keyp; struct wait_exceptional_entry_queue *ewait = container_of(wait, struct wait_exceptional_entry_queue, wait); if (key->mapping != ewait->key.mapping || key->entry_start != ewait->key.entry_start) return 0; return autoremove_wake_function(wait, mode, sync, NULL); } /* * We do not necessarily hold the mapping->tree_lock when we call this * function so it is possible that 'entry' is no longer a valid item in the * radix tree. This is okay because all we really need to do is to find the * correct waitqueue where tasks might be waiting for that old 'entry' and * wake them. */ static void dax_wake_mapping_entry_waiter(struct address_space *mapping, pgoff_t index, void *entry, bool wake_all) { struct exceptional_entry_key key; wait_queue_head_t *wq; wq = dax_entry_waitqueue(mapping, index, entry, &key); /* * Checking for locked entry and prepare_to_wait_exclusive() happens * under mapping->tree_lock, ditto for entry handling in our callers. * So at this point all tasks that could have seen our entry locked * must be in the waitqueue and the following check will see them. */ if (waitqueue_active(wq)) __wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key); } /* * Check whether the given slot is locked. The function must be called with * mapping->tree_lock held */ static inline int slot_locked(struct address_space *mapping, void **slot) { unsigned long entry = (unsigned long) radix_tree_deref_slot_protected(slot, &mapping->tree_lock); return entry & RADIX_DAX_ENTRY_LOCK; } /* * Mark the given slot is locked. The function must be called with * mapping->tree_lock held */ static inline void *lock_slot(struct address_space *mapping, void **slot) { unsigned long entry = (unsigned long) radix_tree_deref_slot_protected(slot, &mapping->tree_lock); entry |= RADIX_DAX_ENTRY_LOCK; radix_tree_replace_slot(&mapping->page_tree, slot, (void *)entry); return (void *)entry; } /* * Mark the given slot is unlocked. The function must be called with * mapping->tree_lock held */ static inline void *unlock_slot(struct address_space *mapping, void **slot) { unsigned long entry = (unsigned long) radix_tree_deref_slot_protected(slot, &mapping->tree_lock); entry &= ~(unsigned long)RADIX_DAX_ENTRY_LOCK; radix_tree_replace_slot(&mapping->page_tree, slot, (void *)entry); return (void *)entry; } /* * Lookup entry in radix tree, wait for it to become unlocked if it is * exceptional entry and return it. The caller must call * put_unlocked_mapping_entry() when he decided not to lock the entry or * put_locked_mapping_entry() when he locked the entry and now wants to * unlock it. * * The function must be called with mapping->tree_lock held. */ static void *get_unlocked_mapping_entry(struct address_space *mapping, pgoff_t index, void ***slotp) { void *entry, **slot; struct wait_exceptional_entry_queue ewait; wait_queue_head_t *wq; init_wait(&ewait.wait); ewait.wait.func = wake_exceptional_entry_func; for (;;) { entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot); if (!entry || WARN_ON_ONCE(!radix_tree_exceptional_entry(entry)) || !slot_locked(mapping, slot)) { if (slotp) *slotp = slot; return entry; } wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key); prepare_to_wait_exclusive(wq, &ewait.wait, TASK_UNINTERRUPTIBLE); spin_unlock_irq(&mapping->tree_lock); schedule(); finish_wait(wq, &ewait.wait); spin_lock_irq(&mapping->tree_lock); } } static void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index) { void *entry, **slot; spin_lock_irq(&mapping->tree_lock); entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot); if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) || !slot_locked(mapping, slot))) { spin_unlock_irq(&mapping->tree_lock); return; } unlock_slot(mapping, slot); spin_unlock_irq(&mapping->tree_lock); dax_wake_mapping_entry_waiter(mapping, index, entry, false); } static void put_locked_mapping_entry(struct address_space *mapping, pgoff_t index) { dax_unlock_mapping_entry(mapping, index); } /* * Called when we are done with radix tree entry we looked up via * get_unlocked_mapping_entry() and which we didn't lock in the end. */ static void put_unlocked_mapping_entry(struct address_space *mapping, pgoff_t index, void *entry) { if (!entry) return; /* We have to wake up next waiter for the radix tree entry lock */ dax_wake_mapping_entry_waiter(mapping, index, entry, false); } /* * Find radix tree entry at given index. If it points to an exceptional entry, * return it with the radix tree entry locked. If the radix tree doesn't * contain given index, create an empty exceptional entry for the index and * return with it locked. * * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will * either return that locked entry or will return an error. This error will * happen if there are any 4k entries within the 2MiB range that we are * requesting. * * We always favor 4k entries over 2MiB entries. There isn't a flow where we * evict 4k entries in order to 'upgrade' them to a 2MiB entry. A 2MiB * insertion will fail if it finds any 4k entries already in the tree, and a * 4k insertion will cause an existing 2MiB entry to be unmapped and * downgraded to 4k entries. This happens for both 2MiB huge zero pages as * well as 2MiB empty entries. * * The exception to this downgrade path is for 2MiB DAX PMD entries that have * real storage backing them. We will leave these real 2MiB DAX entries in * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry. * * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For * persistent memory the benefit is doubtful. We can add that later if we can * show it helps. */ static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index, unsigned long size_flag) { bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */ void *entry, **slot; restart: spin_lock_irq(&mapping->tree_lock); entry = get_unlocked_mapping_entry(mapping, index, &slot); if (WARN_ON_ONCE(entry && !radix_tree_exceptional_entry(entry))) { entry = ERR_PTR(-EIO); goto out_unlock; } if (entry) { if (size_flag & RADIX_DAX_PMD) { if (dax_is_pte_entry(entry)) { put_unlocked_mapping_entry(mapping, index, entry); entry = ERR_PTR(-EEXIST); goto out_unlock; } } else { /* trying to grab a PTE entry */ if (dax_is_pmd_entry(entry) && (dax_is_zero_entry(entry) || dax_is_empty_entry(entry))) { pmd_downgrade = true; } } } /* No entry for given index? Make sure radix tree is big enough. */ if (!entry || pmd_downgrade) { int err; if (pmd_downgrade) { /* * Make sure 'entry' remains valid while we drop * mapping->tree_lock. */ entry = lock_slot(mapping, slot); } spin_unlock_irq(&mapping->tree_lock); /* * Besides huge zero pages the only other thing that gets * downgraded are empty entries which don't need to be * unmapped. */ if (pmd_downgrade && dax_is_zero_entry(entry)) unmap_mapping_range(mapping, (index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0); err = radix_tree_preload( mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM); if (err) { if (pmd_downgrade) put_locked_mapping_entry(mapping, index); return ERR_PTR(err); } spin_lock_irq(&mapping->tree_lock); if (!entry) { /* * We needed to drop the page_tree lock while calling * radix_tree_preload() and we didn't have an entry to * lock. See if another thread inserted an entry at * our index during this time. */ entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot); if (entry) { radix_tree_preload_end(); spin_unlock_irq(&mapping->tree_lock); goto restart; } } if (pmd_downgrade) { radix_tree_delete(&mapping->page_tree, index); mapping->nrexceptional--; dax_wake_mapping_entry_waiter(mapping, index, entry, true); } entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY); err = __radix_tree_insert(&mapping->page_tree, index, dax_radix_order(entry), entry); radix_tree_preload_end(); if (err) { spin_unlock_irq(&mapping->tree_lock); /* * Our insertion of a DAX entry failed, most likely * because we were inserting a PMD entry and it * collided with a PTE sized entry at a different * index in the PMD range. We haven't inserted * anything into the radix tree and have no waiters to * wake. */ return ERR_PTR(err); } /* Good, we have inserted empty locked entry into the tree. */ mapping->nrexceptional++; spin_unlock_irq(&mapping->tree_lock); return entry; } entry = lock_slot(mapping, slot); out_unlock: spin_unlock_irq(&mapping->tree_lock); return entry; } static int __dax_invalidate_mapping_entry(struct address_space *mapping, pgoff_t index, bool trunc) { int ret = 0; void *entry; struct radix_tree_root *page_tree = &mapping->page_tree; spin_lock_irq(&mapping->tree_lock); entry = get_unlocked_mapping_entry(mapping, index, NULL); if (!entry || WARN_ON_ONCE(!radix_tree_exceptional_entry(entry))) goto out; if (!trunc && (radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_DIRTY) || radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))) goto out; radix_tree_delete(page_tree, index); mapping->nrexceptional--; ret = 1; out: put_unlocked_mapping_entry(mapping, index, entry); spin_unlock_irq(&mapping->tree_lock); return ret; } /* * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree * entry to get unlocked before deleting it. */ int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index) { int ret = __dax_invalidate_mapping_entry(mapping, index, true); /* * This gets called from truncate / punch_hole path. As such, the caller * must hold locks protecting against concurrent modifications of the * radix tree (usually fs-private i_mmap_sem for writing). Since the * caller has seen exceptional entry for this index, we better find it * at that index as well... */ WARN_ON_ONCE(!ret); return ret; } /* * Invalidate exceptional DAX entry if it is clean. */ int dax_invalidate_mapping_entry_sync(struct address_space *mapping, pgoff_t index) { return __dax_invalidate_mapping_entry(mapping, index, false); } static int copy_user_dax(struct block_device *bdev, struct dax_device *dax_dev, sector_t sector, size_t size, struct page *to, unsigned long vaddr) { void *vto, *kaddr; pgoff_t pgoff; pfn_t pfn; long rc; int id; rc = bdev_dax_pgoff(bdev, sector, size, &pgoff); if (rc) return rc; id = dax_read_lock(); rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, &pfn); if (rc < 0) { dax_read_unlock(id); return rc; } vto = kmap_atomic(to); copy_user_page(vto, (void __force *)kaddr, vaddr, to); kunmap_atomic(vto); dax_read_unlock(id); return 0; } /* * By this point grab_mapping_entry() has ensured that we have a locked entry * of the appropriate size so we don't have to worry about downgrading PMDs to * PTEs. If we happen to be trying to insert a PTE and there is a PMD * already in the tree, we will skip the insertion and just dirty the PMD as * appropriate. */ static void *dax_insert_mapping_entry(struct address_space *mapping, struct vm_fault *vmf, void *entry, sector_t sector, unsigned long flags) { struct radix_tree_root *page_tree = &mapping->page_tree; void *new_entry; pgoff_t index = vmf->pgoff; if (vmf->flags & FAULT_FLAG_WRITE) __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_ZERO_PAGE)) { /* we are replacing a zero page with block mapping */ if (dax_is_pmd_entry(entry)) unmap_mapping_range(mapping, (vmf->pgoff << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0); else /* pte entry */ unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT, PAGE_SIZE, 0); } spin_lock_irq(&mapping->tree_lock); new_entry = dax_radix_locked_entry(sector, flags); if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) { /* * Only swap our new entry into the radix tree if the current * entry is a zero page or an empty entry. If a normal PTE or * PMD entry is already in the tree, we leave it alone. This * means that if we are trying to insert a PTE and the * existing entry is a PMD, we will just leave the PMD in the * tree and dirty it if necessary. */ struct radix_tree_node *node; void **slot; void *ret; ret = __radix_tree_lookup(page_tree, index, &node, &slot); WARN_ON_ONCE(ret != entry); __radix_tree_replace(page_tree, node, slot, new_entry, NULL, NULL); entry = new_entry; } if (vmf->flags & FAULT_FLAG_WRITE) radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY); spin_unlock_irq(&mapping->tree_lock); return entry; } static inline unsigned long pgoff_address(pgoff_t pgoff, struct vm_area_struct *vma) { unsigned long address; address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma); return address; } /* Walk all mappings of a given index of a file and writeprotect them */ static void dax_mapping_entry_mkclean(struct address_space *mapping, pgoff_t index, unsigned long pfn) { struct vm_area_struct *vma; pte_t pte, *ptep = NULL; pmd_t *pmdp = NULL; spinlock_t *ptl; i_mmap_lock_read(mapping); vma_interval_tree_foreach(vma, &mapping->i_mmap, index, index) { unsigned long address, start, end; cond_resched(); if (!(vma->vm_flags & VM_SHARED)) continue; address = pgoff_address(index, vma); /* * Note because we provide start/end to follow_pte_pmd it will * call mmu_notifier_invalidate_range_start() on our behalf * before taking any lock. */ if (follow_pte_pmd(vma->vm_mm, address, &start, &end, &ptep, &pmdp, &ptl)) continue; if (pmdp) { #ifdef CONFIG_FS_DAX_PMD pmd_t pmd; if (pfn != pmd_pfn(*pmdp)) goto unlock_pmd; if (!pmd_dirty(*pmdp) && !pmd_write(*pmdp)) goto unlock_pmd; flush_cache_page(vma, address, pfn); pmd = pmdp_huge_clear_flush(vma, address, pmdp); pmd = pmd_wrprotect(pmd); pmd = pmd_mkclean(pmd); set_pmd_at(vma->vm_mm, address, pmdp, pmd); mmu_notifier_invalidate_range(vma->vm_mm, start, end); unlock_pmd: spin_unlock(ptl); #endif } else { if (pfn != pte_pfn(*ptep)) goto unlock_pte; if (!pte_dirty(*ptep) && !pte_write(*ptep)) goto unlock_pte; flush_cache_page(vma, address, pfn); pte = ptep_clear_flush(vma, address, ptep); pte = pte_wrprotect(pte); pte = pte_mkclean(pte); set_pte_at(vma->vm_mm, address, ptep, pte); mmu_notifier_invalidate_range(vma->vm_mm, start, end); unlock_pte: pte_unmap_unlock(ptep, ptl); } mmu_notifier_invalidate_range_end(vma->vm_mm, start, end); } i_mmap_unlock_read(mapping); } static int dax_writeback_one(struct block_device *bdev, struct dax_device *dax_dev, struct address_space *mapping, pgoff_t index, void *entry) { struct radix_tree_root *page_tree = &mapping->page_tree; void *entry2, **slot, *kaddr; long ret = 0, id; sector_t sector; pgoff_t pgoff; size_t size; pfn_t pfn; /* * A page got tagged dirty in DAX mapping? Something is seriously * wrong. */ if (WARN_ON(!radix_tree_exceptional_entry(entry))) return -EIO; spin_lock_irq(&mapping->tree_lock); entry2 = get_unlocked_mapping_entry(mapping, index, &slot); /* Entry got punched out / reallocated? */ if (!entry2 || WARN_ON_ONCE(!radix_tree_exceptional_entry(entry2))) goto put_unlocked; /* * Entry got reallocated elsewhere? No need to writeback. We have to * compare sectors as we must not bail out due to difference in lockbit * or entry type. */ if (dax_radix_sector(entry2) != dax_radix_sector(entry)) goto put_unlocked; if (WARN_ON_ONCE(dax_is_empty_entry(entry) || dax_is_zero_entry(entry))) { ret = -EIO; goto put_unlocked; } /* Another fsync thread may have already written back this entry */ if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE)) goto put_unlocked; /* Lock the entry to serialize with page faults */ entry = lock_slot(mapping, slot); /* * We can clear the tag now but we have to be careful so that concurrent * dax_writeback_one() calls for the same index cannot finish before we * actually flush the caches. This is achieved as the calls will look * at the entry only under tree_lock and once they do that they will * see the entry locked and wait for it to unlock. */ radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE); spin_unlock_irq(&mapping->tree_lock); /* * Even if dax_writeback_mapping_range() was given a wbc->range_start * in the middle of a PMD, the 'index' we are given will be aligned to * the start index of the PMD, as will the sector we pull from * 'entry'. This allows us to flush for PMD_SIZE and not have to * worry about partial PMD writebacks. */ sector = dax_radix_sector(entry); size = PAGE_SIZE << dax_radix_order(entry); id = dax_read_lock(); ret = bdev_dax_pgoff(bdev, sector, size, &pgoff); if (ret) goto dax_unlock; /* * dax_direct_access() may sleep, so cannot hold tree_lock over * its invocation. */ ret = dax_direct_access(dax_dev, pgoff, size / PAGE_SIZE, &kaddr, &pfn); if (ret < 0) goto dax_unlock; if (WARN_ON_ONCE(ret < size / PAGE_SIZE)) { ret = -EIO; goto dax_unlock; } dax_mapping_entry_mkclean(mapping, index, pfn_t_to_pfn(pfn)); dax_flush(dax_dev, pgoff, kaddr, size); /* * After we have flushed the cache, we can clear the dirty tag. There * cannot be new dirty data in the pfn after the flush has completed as * the pfn mappings are writeprotected and fault waits for mapping * entry lock. */ spin_lock_irq(&mapping->tree_lock); radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_DIRTY); spin_unlock_irq(&mapping->tree_lock); trace_dax_writeback_one(mapping->host, index, size >> PAGE_SHIFT); dax_unlock: dax_read_unlock(id); put_locked_mapping_entry(mapping, index); return ret; put_unlocked: put_unlocked_mapping_entry(mapping, index, entry2); spin_unlock_irq(&mapping->tree_lock); return ret; } /* * Flush the mapping to the persistent domain within the byte range of [start, * end]. This is required by data integrity operations to ensure file data is * on persistent storage prior to completion of the operation. */ int dax_writeback_mapping_range(struct address_space *mapping, struct block_device *bdev, struct writeback_control *wbc) { struct inode *inode = mapping->host; pgoff_t start_index, end_index; pgoff_t indices[PAGEVEC_SIZE]; struct dax_device *dax_dev; struct pagevec pvec; bool done = false; int i, ret = 0; if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT)) return -EIO; if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL) return 0; dax_dev = dax_get_by_host(bdev->bd_disk->disk_name); if (!dax_dev) return -EIO; start_index = wbc->range_start >> PAGE_SHIFT; end_index = wbc->range_end >> PAGE_SHIFT; trace_dax_writeback_range(inode, start_index, end_index); tag_pages_for_writeback(mapping, start_index, end_index); pagevec_init(&pvec, 0); while (!done) { pvec.nr = find_get_entries_tag(mapping, start_index, PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE, pvec.pages, indices); if (pvec.nr == 0) break; for (i = 0; i < pvec.nr; i++) { if (indices[i] > end_index) { done = true; break; } ret = dax_writeback_one(bdev, dax_dev, mapping, indices[i], pvec.pages[i]); if (ret < 0) { mapping_set_error(mapping, ret); goto out; } } start_index = indices[pvec.nr - 1] + 1; } out: put_dax(dax_dev); trace_dax_writeback_range_done(inode, start_index, end_index); return (ret < 0 ? ret : 0); } EXPORT_SYMBOL_GPL(dax_writeback_mapping_range); static int dax_insert_mapping(struct address_space *mapping, struct block_device *bdev, struct dax_device *dax_dev, sector_t sector, size_t size, void *entry, struct vm_area_struct *vma, struct vm_fault *vmf) { unsigned long vaddr = vmf->address; void *ret, *kaddr; pgoff_t pgoff; int id, rc; pfn_t pfn; rc = bdev_dax_pgoff(bdev, sector, size, &pgoff); if (rc) return rc; id = dax_read_lock(); rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, &pfn); if (rc < 0) { dax_read_unlock(id); return rc; } dax_read_unlock(id); ret = dax_insert_mapping_entry(mapping, vmf, entry, sector, 0); if (IS_ERR(ret)) return PTR_ERR(ret); trace_dax_insert_mapping(mapping->host, vmf, ret); if (vmf->flags & FAULT_FLAG_WRITE) return vm_insert_mixed_mkwrite(vma, vaddr, pfn); else return vm_insert_mixed(vma, vaddr, pfn); } /* * 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. Instead we insert a read-only mapping of the 4k zero page. * If this page is ever written to we will re-fault and change the mapping to * point to real DAX storage instead. */ static int dax_load_hole(struct address_space *mapping, void *entry, struct vm_fault *vmf) { struct inode *inode = mapping->host; unsigned long vaddr = vmf->address; int ret = VM_FAULT_NOPAGE; struct page *zero_page; void *entry2; zero_page = ZERO_PAGE(0); if (unlikely(!zero_page)) { ret = VM_FAULT_OOM; goto out; } entry2 = dax_insert_mapping_entry(mapping, vmf, entry, 0, RADIX_DAX_ZERO_PAGE); if (IS_ERR(entry2)) { ret = VM_FAULT_SIGBUS; goto out; } vm_insert_mixed(vmf->vma, vaddr, page_to_pfn_t(zero_page)); out: trace_dax_load_hole(inode, vmf, ret); return ret; } static bool dax_range_is_aligned(struct block_device *bdev, unsigned int offset, unsigned int length) { unsigned short sector_size = bdev_logical_block_size(bdev); if (!IS_ALIGNED(offset, sector_size)) return false; if (!IS_ALIGNED(length, sector_size)) return false; return true; } int __dax_zero_page_range(struct block_device *bdev, struct dax_device *dax_dev, sector_t sector, unsigned int offset, unsigned int size) { if (dax_range_is_aligned(bdev, offset, size)) { sector_t start_sector = sector + (offset >> 9); return blkdev_issue_zeroout(bdev, start_sector, size >> 9, GFP_NOFS, 0); } else { pgoff_t pgoff; long rc, id; void *kaddr; pfn_t pfn; rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff); if (rc) return rc; id = dax_read_lock(); rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr, &pfn); if (rc < 0) { dax_read_unlock(id); return rc; } memset(kaddr + offset, 0, size); dax_flush(dax_dev, pgoff, kaddr + offset, size); dax_read_unlock(id); } return 0; } EXPORT_SYMBOL_GPL(__dax_zero_page_range); static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos) { return iomap->blkno + (((pos & PAGE_MASK) - iomap->offset) >> 9); } static loff_t dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data, struct iomap *iomap) { struct block_device *bdev = iomap->bdev; struct dax_device *dax_dev = iomap->dax_dev; struct iov_iter *iter = data; loff_t end = pos + length, done = 0; ssize_t ret = 0; int id; if (iov_iter_rw(iter) == READ) { end = min(end, i_size_read(inode)); if (pos >= end) return 0; if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN) return iov_iter_zero(min(length, end - pos), iter); } if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED)) return -EIO; /* * Write can allocate block for an area which has a hole page mapped * into page tables. We have to tear down these mappings so that data * written by write(2) is visible in mmap. */ if (iomap->flags & IOMAP_F_NEW) { invalidate_inode_pages2_range(inode->i_mapping, pos >> PAGE_SHIFT, (end - 1) >> PAGE_SHIFT); } id = dax_read_lock(); while (pos < end) { unsigned offset = pos & (PAGE_SIZE - 1); const size_t size = ALIGN(length + offset, PAGE_SIZE); const sector_t sector = dax_iomap_sector(iomap, pos); ssize_t map_len; pgoff_t pgoff; void *kaddr; pfn_t pfn; if (fatal_signal_pending(current)) { ret = -EINTR; break; } ret = bdev_dax_pgoff(bdev, sector, size, &pgoff); if (ret) break; map_len = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, &pfn); if (map_len < 0) { ret = map_len; break; } map_len = PFN_PHYS(map_len); kaddr += offset; map_len -= offset; if (map_len > end - pos) map_len = end - pos; if (iov_iter_rw(iter) == WRITE) map_len = dax_copy_from_iter(dax_dev, pgoff, kaddr, map_len, iter); else map_len = copy_to_iter(kaddr, map_len, iter); if (map_len <= 0) { ret = map_len ? map_len : -EFAULT; break; } pos += map_len; length -= map_len; done += map_len; } dax_read_unlock(id); return done ? done : ret; } /** * dax_iomap_rw - Perform I/O to a DAX file * @iocb: The control block for this I/O * @iter: The addresses to do I/O from or to * @ops: iomap ops passed from the file system * * This function performs read and write operations to directly mapped * persistent memory. The callers needs to take care of read/write exclusion * and evicting any page cache pages in the region under I/O. */ ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter, const struct iomap_ops *ops) { struct address_space *mapping = iocb->ki_filp->f_mapping; struct inode *inode = mapping->host; loff_t pos = iocb->ki_pos, ret = 0, done = 0; unsigned flags = 0; if (iov_iter_rw(iter) == WRITE) { lockdep_assert_held_exclusive(&inode->i_rwsem); flags |= IOMAP_WRITE; } else { lockdep_assert_held(&inode->i_rwsem); } while (iov_iter_count(iter)) { ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops, iter, dax_iomap_actor); if (ret <= 0) break; pos += ret; done += ret; } iocb->ki_pos += done; return done ? done : ret; } EXPORT_SYMBOL_GPL(dax_iomap_rw); static int dax_fault_return(int error) { if (error == 0) return VM_FAULT_NOPAGE; if (error == -ENOMEM) return VM_FAULT_OOM; return VM_FAULT_SIGBUS; } static int dax_iomap_pte_fault(struct vm_fault *vmf, const struct iomap_ops *ops) { struct address_space *mapping = vmf->vma->vm_file->f_mapping; struct inode *inode = mapping->host; unsigned long vaddr = vmf->address; loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT; sector_t sector; struct iomap iomap = { 0 }; unsigned flags = IOMAP_FAULT; int error, major = 0; int vmf_ret = 0; void *entry; trace_dax_pte_fault(inode, vmf, vmf_ret); /* * Check whether offset isn't beyond end of file now. Caller is supposed * to hold locks serializing us with truncate / punch hole so this is * a reliable test. */ if (pos >= i_size_read(inode)) { vmf_ret = VM_FAULT_SIGBUS; goto out; } if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page) flags |= IOMAP_WRITE; entry = grab_mapping_entry(mapping, vmf->pgoff, 0); if (IS_ERR(entry)) { vmf_ret = dax_fault_return(PTR_ERR(entry)); goto out; } /* * It is possible, particularly with mixed reads & writes to private * mappings, that we have raced with a PMD fault that overlaps with * the PTE we need to set up. If so just return and the fault will be * retried. */ if (pmd_trans_huge(*vmf->pmd) || pmd_devmap(*vmf->pmd)) { vmf_ret = VM_FAULT_NOPAGE; goto unlock_entry; } /* * Note that we don't bother to use iomap_apply here: DAX required * the file system block size to be equal the page size, which means * that we never have to deal with more than a single extent here. */ error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap); if (error) { vmf_ret = dax_fault_return(error); goto unlock_entry; } if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) { error = -EIO; /* fs corruption? */ goto error_finish_iomap; } sector = dax_iomap_sector(&iomap, pos); if (vmf->cow_page) { switch (iomap.type) { case IOMAP_HOLE: case IOMAP_UNWRITTEN: clear_user_highpage(vmf->cow_page, vaddr); break; case IOMAP_MAPPED: error = copy_user_dax(iomap.bdev, iomap.dax_dev, sector, PAGE_SIZE, vmf->cow_page, vaddr); break; default: WARN_ON_ONCE(1); error = -EIO; break; } if (error) goto error_finish_iomap; __SetPageUptodate(vmf->cow_page); vmf_ret = finish_fault(vmf); if (!vmf_ret) vmf_ret = VM_FAULT_DONE_COW; goto finish_iomap; } switch (iomap.type) { case IOMAP_MAPPED: if (iomap.flags & IOMAP_F_NEW) { count_vm_event(PGMAJFAULT); count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT); major = VM_FAULT_MAJOR; } error = dax_insert_mapping(mapping, iomap.bdev, iomap.dax_dev, sector, PAGE_SIZE, entry, vmf->vma, vmf); /* -EBUSY is fine, somebody else faulted on the same PTE */ if (error == -EBUSY) error = 0; break; case IOMAP_UNWRITTEN: case IOMAP_HOLE: if (!(vmf->flags & FAULT_FLAG_WRITE)) { vmf_ret = dax_load_hole(mapping, entry, vmf); goto finish_iomap; } /*FALLTHRU*/ default: WARN_ON_ONCE(1); error = -EIO; break; } error_finish_iomap: vmf_ret = dax_fault_return(error) | major; finish_iomap: if (ops->iomap_end) { int copied = PAGE_SIZE; if (vmf_ret & VM_FAULT_ERROR) copied = 0; /* * The fault is done by now and there's no way back (other * thread may be already happily using PTE we have installed). * Just ignore error from ->iomap_end since we cannot do much * with it. */ ops->iomap_end(inode, pos, PAGE_SIZE, copied, flags, &iomap); } unlock_entry: put_locked_mapping_entry(mapping, vmf->pgoff); out: trace_dax_pte_fault_done(inode, vmf, vmf_ret); return vmf_ret; } #ifdef CONFIG_FS_DAX_PMD /* * The 'colour' (ie low bits) within a PMD of a page offset. This comes up * more often than one might expect in the below functions. */ #define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1) static int dax_pmd_insert_mapping(struct vm_fault *vmf, struct iomap *iomap, loff_t pos, void *entry) { struct address_space *mapping = vmf->vma->vm_file->f_mapping; const sector_t sector = dax_iomap_sector(iomap, pos); struct dax_device *dax_dev = iomap->dax_dev; struct block_device *bdev = iomap->bdev; struct inode *inode = mapping->host; const size_t size = PMD_SIZE; void *ret = NULL, *kaddr; long length = 0; pgoff_t pgoff; pfn_t pfn; int id; if (bdev_dax_pgoff(bdev, sector, size, &pgoff) != 0) goto fallback; id = dax_read_lock(); length = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, &pfn); if (length < 0) goto unlock_fallback; length = PFN_PHYS(length); if (length < size) goto unlock_fallback; if (pfn_t_to_pfn(pfn) & PG_PMD_COLOUR) goto unlock_fallback; if (!pfn_t_devmap(pfn)) goto unlock_fallback; dax_read_unlock(id); ret = dax_insert_mapping_entry(mapping, vmf, entry, sector, RADIX_DAX_PMD); if (IS_ERR(ret)) goto fallback; trace_dax_pmd_insert_mapping(inode, vmf, length, pfn, ret); return vmf_insert_pfn_pmd(vmf->vma, vmf->address, vmf->pmd, pfn, vmf->flags & FAULT_FLAG_WRITE); unlock_fallback: dax_read_unlock(id); fallback: trace_dax_pmd_insert_mapping_fallback(inode, vmf, length, pfn, ret); return VM_FAULT_FALLBACK; } static int dax_pmd_load_hole(struct vm_fault *vmf, struct iomap *iomap, void *entry) { struct address_space *mapping = vmf->vma->vm_file->f_mapping; unsigned long pmd_addr = vmf->address & PMD_MASK; struct inode *inode = mapping->host; struct page *zero_page; void *ret = NULL; spinlock_t *ptl; pmd_t pmd_entry; zero_page = mm_get_huge_zero_page(vmf->vma->vm_mm); if (unlikely(!zero_page)) goto fallback; ret = dax_insert_mapping_entry(mapping, vmf, entry, 0, RADIX_DAX_PMD | RADIX_DAX_ZERO_PAGE); if (IS_ERR(ret)) goto fallback; ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd); if (!pmd_none(*(vmf->pmd))) { spin_unlock(ptl); goto fallback; } pmd_entry = mk_pmd(zero_page, vmf->vma->vm_page_prot); pmd_entry = pmd_mkhuge(pmd_entry); set_pmd_at(vmf->vma->vm_mm, pmd_addr, vmf->pmd, pmd_entry); spin_unlock(ptl); trace_dax_pmd_load_hole(inode, vmf, zero_page, ret); return VM_FAULT_NOPAGE; fallback: trace_dax_pmd_load_hole_fallback(inode, vmf, zero_page, ret); return VM_FAULT_FALLBACK; } static int dax_iomap_pmd_fault(struct vm_fault *vmf, const struct iomap_ops *ops) { struct vm_area_struct *vma = vmf->vma; struct address_space *mapping = vma->vm_file->f_mapping; unsigned long pmd_addr = vmf->address & PMD_MASK; bool write = vmf->flags & FAULT_FLAG_WRITE; unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT; struct inode *inode = mapping->host; int result = VM_FAULT_FALLBACK; struct iomap iomap = { 0 }; pgoff_t max_pgoff, pgoff; void *entry; loff_t pos; int error; /* * Check whether offset isn't beyond end of file now. Caller is * supposed to hold locks serializing us with truncate / punch hole so * this is a reliable test. */ pgoff = linear_page_index(vma, pmd_addr); max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT; trace_dax_pmd_fault(inode, vmf, max_pgoff, 0); /* * Make sure that the faulting address's PMD offset (color) matches * the PMD offset from the start of the file. This is necessary so * that a PMD range in the page table overlaps exactly with a PMD * range in the radix tree. */ if ((vmf->pgoff & PG_PMD_COLOUR) != ((vmf->address >> PAGE_SHIFT) & PG_PMD_COLOUR)) goto fallback; /* Fall back to PTEs if we're going to COW */ if (write && !(vma->vm_flags & VM_SHARED)) goto fallback; /* If the PMD would extend outside the VMA */ if (pmd_addr < vma->vm_start) goto fallback; if ((pmd_addr + PMD_SIZE) > vma->vm_end) goto fallback; if (pgoff > max_pgoff) { result = VM_FAULT_SIGBUS; goto out; } /* If the PMD would extend beyond the file size */ if ((pgoff | PG_PMD_COLOUR) > max_pgoff) goto fallback; /* * grab_mapping_entry() will make sure we get a 2MiB empty entry, a * 2MiB zero page entry or a DAX PMD. If it can't (because a 4k page * is already in the tree, for instance), it will return -EEXIST and * we just fall back to 4k entries. */ entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD); if (IS_ERR(entry)) goto fallback; /* * It is possible, particularly with mixed reads & writes to private * mappings, that we have raced with a PTE fault that overlaps with * the PMD we need to set up. If so just return and the fault will be * retried. */ if (!pmd_none(*vmf->pmd) && !pmd_trans_huge(*vmf->pmd) && !pmd_devmap(*vmf->pmd)) { result = 0; goto unlock_entry; } /* * Note that we don't use iomap_apply here. We aren't doing I/O, only * setting up a mapping, so really we're using iomap_begin() as a way * to look up our filesystem block. */ pos = (loff_t)pgoff << PAGE_SHIFT; error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap); if (error) goto unlock_entry; if (iomap.offset + iomap.length < pos + PMD_SIZE) goto finish_iomap; switch (iomap.type) { case IOMAP_MAPPED: result = dax_pmd_insert_mapping(vmf, &iomap, pos, entry); break; case IOMAP_UNWRITTEN: case IOMAP_HOLE: if (WARN_ON_ONCE(write)) break; result = dax_pmd_load_hole(vmf, &iomap, entry); break; default: WARN_ON_ONCE(1); break; } finish_iomap: if (ops->iomap_end) { int copied = PMD_SIZE; if (result == VM_FAULT_FALLBACK) copied = 0; /* * The fault is done by now and there's no way back (other * thread may be already happily using PMD we have installed). * Just ignore error from ->iomap_end since we cannot do much * with it. */ ops->iomap_end(inode, pos, PMD_SIZE, copied, iomap_flags, &iomap); } unlock_entry: put_locked_mapping_entry(mapping, pgoff); fallback: if (result == VM_FAULT_FALLBACK) { split_huge_pmd(vma, vmf->pmd, vmf->address); count_vm_event(THP_FAULT_FALLBACK); } out: trace_dax_pmd_fault_done(inode, vmf, max_pgoff, result); return result; } #else static int dax_iomap_pmd_fault(struct vm_fault *vmf, const struct iomap_ops *ops) { return VM_FAULT_FALLBACK; } #endif /* CONFIG_FS_DAX_PMD */ /** * dax_iomap_fault - handle a page fault on a DAX file * @vmf: The description of the fault * @ops: iomap ops passed from the file system * * When a page fault occurs, filesystems may call this helper in * their fault handler for DAX files. dax_iomap_fault() assumes the caller * has done all the necessary locking for page fault to proceed * successfully. */ int dax_iomap_fault(struct vm_fault *vmf, enum page_entry_size pe_size, const struct iomap_ops *ops) { switch (pe_size) { case PE_SIZE_PTE: return dax_iomap_pte_fault(vmf, ops); case PE_SIZE_PMD: return dax_iomap_pmd_fault(vmf, ops); default: return VM_FAULT_FALLBACK; } } EXPORT_SYMBOL_GPL(dax_iomap_fault);