// SPDX-License-Identifier: GPL-2.0-only /* * fs/dax.c - Direct Access filesystem code * Copyright (c) 2013-2014 Intel Corporation * Author: Matthew Wilcox <matthew.r.wilcox@intel.com> * Author: Ross Zwisler <ross.zwisler@linux.intel.com> */ #include <linux/atomic.h> #include <linux/blkdev.h> #include <linux/buffer_head.h> #include <linux/dax.h> #include <linux/fs.h> #include <linux/genhd.h> #include <linux/highmem.h> #include <linux/memcontrol.h> #include <linux/mm.h> #include <linux/mutex.h> #include <linux/pagevec.h> #include <linux/sched.h> #include <linux/sched/signal.h> #include <linux/uio.h> #include <linux/vmstat.h> #include <linux/pfn_t.h> #include <linux/sizes.h> #include <linux/mmu_notifier.h> #include <linux/iomap.h> #include <asm/pgalloc.h> #define CREATE_TRACE_POINTS #include <trace/events/fs_dax.h> static inline unsigned int pe_order(enum page_entry_size pe_size) { if (pe_size == PE_SIZE_PTE) return PAGE_SHIFT - PAGE_SHIFT; if (pe_size == PE_SIZE_PMD) return PMD_SHIFT - PAGE_SHIFT; if (pe_size == PE_SIZE_PUD) return PUD_SHIFT - PAGE_SHIFT; return ~0; } /* 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) /* The 'colour' (ie low bits) within a PMD of a page offset. */ #define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1) #define PG_PMD_NR (PMD_SIZE >> PAGE_SHIFT) /* The order of a PMD entry */ #define PMD_ORDER (PMD_SHIFT - PAGE_SHIFT) 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); /* * DAX pagecache entries use XArray value entries so they can't be mistaken * for pages. We use one bit for locking, one bit for the entry size (PMD) * and two more to tell us if the entry is a zero page or an empty entry that * is just used for locking. In total four special bits. * * If the PMD bit isn't set the entry has size PAGE_SIZE, and if the ZERO_PAGE * and EMPTY bits aren't set the entry is a normal DAX entry with a filesystem * block allocation. */ #define DAX_SHIFT (4) #define DAX_LOCKED (1UL << 0) #define DAX_PMD (1UL << 1) #define DAX_ZERO_PAGE (1UL << 2) #define DAX_EMPTY (1UL << 3) static unsigned long dax_to_pfn(void *entry) { return xa_to_value(entry) >> DAX_SHIFT; } static void *dax_make_entry(pfn_t pfn, unsigned long flags) { return xa_mk_value(flags | (pfn_t_to_pfn(pfn) << DAX_SHIFT)); } static bool dax_is_locked(void *entry) { return xa_to_value(entry) & DAX_LOCKED; } static unsigned int dax_entry_order(void *entry) { if (xa_to_value(entry) & DAX_PMD) return PMD_ORDER; return 0; } static unsigned long dax_is_pmd_entry(void *entry) { return xa_to_value(entry) & DAX_PMD; } static bool dax_is_pte_entry(void *entry) { return !(xa_to_value(entry) & DAX_PMD); } static int dax_is_zero_entry(void *entry) { return xa_to_value(entry) & DAX_ZERO_PAGE; } static int dax_is_empty_entry(void *entry) { return xa_to_value(entry) & DAX_EMPTY; } /* * true if the entry that was found is of a smaller order than the entry * we were looking for */ static bool dax_is_conflict(void *entry) { return entry == XA_RETRY_ENTRY; } /* * DAX page cache entry locking */ struct exceptional_entry_key { struct xarray *xa; 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 xa_state *xas, void *entry, struct exceptional_entry_key *key) { unsigned long hash; unsigned long index = xas->xa_index; /* * 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 &= ~PG_PMD_COLOUR; key->xa = xas->xa; key->entry_start = index; hash = hash_long((unsigned long)xas->xa ^ 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->xa != ewait->key.xa || key->entry_start != ewait->key.entry_start) return 0; return autoremove_wake_function(wait, mode, sync, NULL); } /* * @entry may no longer be the entry at the index in the mapping. * The important information it's conveying is whether the entry at * this index used to be a PMD entry. */ static void dax_wake_entry(struct xa_state *xas, void *entry, bool wake_all) { struct exceptional_entry_key key; wait_queue_head_t *wq; wq = dax_entry_waitqueue(xas, entry, &key); /* * Checking for locked entry and prepare_to_wait_exclusive() happens * under the i_pages 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); } /* * Look up entry in page cache, wait for it to become unlocked if it * is a DAX entry and return it. The caller must subsequently call * put_unlocked_entry() if it did not lock the entry or dax_unlock_entry() * if it did. The entry returned may have a larger order than @order. * If @order is larger than the order of the entry found in i_pages, this * function returns a dax_is_conflict entry. * * Must be called with the i_pages lock held. */ static void *get_unlocked_entry(struct xa_state *xas, unsigned int order) { void *entry; struct wait_exceptional_entry_queue ewait; wait_queue_head_t *wq; init_wait(&ewait.wait); ewait.wait.func = wake_exceptional_entry_func; for (;;) { entry = xas_find_conflict(xas); if (!entry || WARN_ON_ONCE(!xa_is_value(entry))) return entry; if (dax_entry_order(entry) < order) return XA_RETRY_ENTRY; if (!dax_is_locked(entry)) return entry; wq = dax_entry_waitqueue(xas, entry, &ewait.key); prepare_to_wait_exclusive(wq, &ewait.wait, TASK_UNINTERRUPTIBLE); xas_unlock_irq(xas); xas_reset(xas); schedule(); finish_wait(wq, &ewait.wait); xas_lock_irq(xas); } } /* * The only thing keeping the address space around is the i_pages lock * (it's cycled in clear_inode() after removing the entries from i_pages) * After we call xas_unlock_irq(), we cannot touch xas->xa. */ static void wait_entry_unlocked(struct xa_state *xas, void *entry) { struct wait_exceptional_entry_queue ewait; wait_queue_head_t *wq; init_wait(&ewait.wait); ewait.wait.func = wake_exceptional_entry_func; wq = dax_entry_waitqueue(xas, entry, &ewait.key); /* * Unlike get_unlocked_entry() there is no guarantee that this * path ever successfully retrieves an unlocked entry before an * inode dies. Perform a non-exclusive wait in case this path * never successfully performs its own wake up. */ prepare_to_wait(wq, &ewait.wait, TASK_UNINTERRUPTIBLE); xas_unlock_irq(xas); schedule(); finish_wait(wq, &ewait.wait); } static void put_unlocked_entry(struct xa_state *xas, void *entry) { /* If we were the only waiter woken, wake the next one */ if (entry && !dax_is_conflict(entry)) dax_wake_entry(xas, entry, false); } /* * We used the xa_state to get the entry, but then we locked the entry and * dropped the xa_lock, so we know the xa_state is stale and must be reset * before use. */ static void dax_unlock_entry(struct xa_state *xas, void *entry) { void *old; BUG_ON(dax_is_locked(entry)); xas_reset(xas); xas_lock_irq(xas); old = xas_store(xas, entry); xas_unlock_irq(xas); BUG_ON(!dax_is_locked(old)); dax_wake_entry(xas, entry, false); } /* * Return: The entry stored at this location before it was locked. */ static void *dax_lock_entry(struct xa_state *xas, void *entry) { unsigned long v = xa_to_value(entry); return xas_store(xas, xa_mk_value(v | DAX_LOCKED)); } static unsigned long dax_entry_size(void *entry) { if (dax_is_zero_entry(entry)) return 0; else if (dax_is_empty_entry(entry)) return 0; else if (dax_is_pmd_entry(entry)) return PMD_SIZE; else return PAGE_SIZE; } static unsigned long dax_end_pfn(void *entry) { return dax_to_pfn(entry) + dax_entry_size(entry) / PAGE_SIZE; } /* * Iterate through all mapped pfns represented by an entry, i.e. skip * 'empty' and 'zero' entries. */ #define for_each_mapped_pfn(entry, pfn) \ for (pfn = dax_to_pfn(entry); \ pfn < dax_end_pfn(entry); pfn++) /* * TODO: for reflink+dax we need a way to associate a single page with * multiple address_space instances at different linear_page_index() * offsets. */ static void dax_associate_entry(void *entry, struct address_space *mapping, struct vm_area_struct *vma, unsigned long address) { unsigned long size = dax_entry_size(entry), pfn, index; int i = 0; if (IS_ENABLED(CONFIG_FS_DAX_LIMITED)) return; index = linear_page_index(vma, address & ~(size - 1)); for_each_mapped_pfn(entry, pfn) { struct page *page = pfn_to_page(pfn); WARN_ON_ONCE(page->mapping); page->mapping = mapping; page->index = index + i++; } } static void dax_disassociate_entry(void *entry, struct address_space *mapping, bool trunc) { unsigned long pfn; if (IS_ENABLED(CONFIG_FS_DAX_LIMITED)) return; for_each_mapped_pfn(entry, pfn) { struct page *page = pfn_to_page(pfn); WARN_ON_ONCE(trunc && page_ref_count(page) > 1); WARN_ON_ONCE(page->mapping && page->mapping != mapping); page->mapping = NULL; page->index = 0; } } static struct page *dax_busy_page(void *entry) { unsigned long pfn; for_each_mapped_pfn(entry, pfn) { struct page *page = pfn_to_page(pfn); if (page_ref_count(page) > 1) return page; } return NULL; } /* * dax_lock_mapping_entry - Lock the DAX entry corresponding to a page * @page: The page whose entry we want to lock * * Context: Process context. * Return: A cookie to pass to dax_unlock_page() or 0 if the entry could * not be locked. */ dax_entry_t dax_lock_page(struct page *page) { XA_STATE(xas, NULL, 0); void *entry; /* Ensure page->mapping isn't freed while we look at it */ rcu_read_lock(); for (;;) { struct address_space *mapping = READ_ONCE(page->mapping); entry = NULL; if (!mapping || !dax_mapping(mapping)) break; /* * In the device-dax case there's no need to lock, a * struct dev_pagemap pin is sufficient to keep the * inode alive, and we assume we have dev_pagemap pin * otherwise we would not have a valid pfn_to_page() * translation. */ entry = (void *)~0UL; if (S_ISCHR(mapping->host->i_mode)) break; xas.xa = &mapping->i_pages; xas_lock_irq(&xas); if (mapping != page->mapping) { xas_unlock_irq(&xas); continue; } xas_set(&xas, page->index); entry = xas_load(&xas); if (dax_is_locked(entry)) { rcu_read_unlock(); wait_entry_unlocked(&xas, entry); rcu_read_lock(); continue; } dax_lock_entry(&xas, entry); xas_unlock_irq(&xas); break; } rcu_read_unlock(); return (dax_entry_t)entry; } void dax_unlock_page(struct page *page, dax_entry_t cookie) { struct address_space *mapping = page->mapping; XA_STATE(xas, &mapping->i_pages, page->index); if (S_ISCHR(mapping->host->i_mode)) return; dax_unlock_entry(&xas, (void *)cookie); } /* * Find page cache entry at given index. If it is a DAX entry, return it * with the entry locked. If the page cache doesn't contain an entry at * that index, add a locked empty entry. * * When requesting an entry with size DAX_PMD, grab_mapping_entry() will * either return that locked entry or will return VM_FAULT_FALLBACK. * This will happen if there are any PTE entries within the PMD range * that we are requesting. * * We always favor PTE entries over PMD entries. There isn't a flow where we * evict PTE entries in order to 'upgrade' them to a PMD entry. A PMD * insertion will fail if it finds any PTE entries already in the tree, and a * PTE insertion will cause an existing PMD entry to be unmapped and * downgraded to PTE entries. This happens for both PMD zero pages as * well as PMD empty entries. * * The exception to this downgrade path is for PMD entries that have * real storage backing them. We will leave these real PMD entries in * the tree, and PTE writes will simply dirty the entire PMD 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. * * On error, this function does not return an ERR_PTR. Instead it returns * a VM_FAULT code, encoded as an xarray internal entry. The ERR_PTR values * overlap with xarray value entries. */ static void *grab_mapping_entry(struct xa_state *xas, struct address_space *mapping, unsigned int order) { unsigned long index = xas->xa_index; bool pmd_downgrade = false; /* splitting PMD entry into PTE entries? */ void *entry; retry: xas_lock_irq(xas); entry = get_unlocked_entry(xas, order); if (entry) { if (dax_is_conflict(entry)) goto fallback; if (!xa_is_value(entry)) { xas_set_err(xas, -EIO); goto out_unlock; } if (order == 0) { if (dax_is_pmd_entry(entry) && (dax_is_zero_entry(entry) || dax_is_empty_entry(entry))) { pmd_downgrade = true; } } } if (pmd_downgrade) { /* * Make sure 'entry' remains valid while we drop * the i_pages lock. */ dax_lock_entry(xas, entry); /* * Besides huge zero pages the only other thing that gets * downgraded are empty entries which don't need to be * unmapped. */ if (dax_is_zero_entry(entry)) { xas_unlock_irq(xas); unmap_mapping_pages(mapping, xas->xa_index & ~PG_PMD_COLOUR, PG_PMD_NR, false); xas_reset(xas); xas_lock_irq(xas); } dax_disassociate_entry(entry, mapping, false); xas_store(xas, NULL); /* undo the PMD join */ dax_wake_entry(xas, entry, true); mapping->nrexceptional--; entry = NULL; xas_set(xas, index); } if (entry) { dax_lock_entry(xas, entry); } else { unsigned long flags = DAX_EMPTY; if (order > 0) flags |= DAX_PMD; entry = dax_make_entry(pfn_to_pfn_t(0), flags); dax_lock_entry(xas, entry); if (xas_error(xas)) goto out_unlock; mapping->nrexceptional++; } out_unlock: xas_unlock_irq(xas); if (xas_nomem(xas, mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM)) goto retry; if (xas->xa_node == XA_ERROR(-ENOMEM)) return xa_mk_internal(VM_FAULT_OOM); if (xas_error(xas)) return xa_mk_internal(VM_FAULT_SIGBUS); return entry; fallback: xas_unlock_irq(xas); return xa_mk_internal(VM_FAULT_FALLBACK); } /** * dax_layout_busy_page_range - find first pinned page in @mapping * @mapping: address space to scan for a page with ref count > 1 * @start: Starting offset. Page containing 'start' is included. * @end: End offset. Page containing 'end' is included. If 'end' is LLONG_MAX, * pages from 'start' till the end of file are included. * * DAX requires ZONE_DEVICE mapped pages. These pages are never * 'onlined' to the page allocator so they are considered idle when * page->count == 1. A filesystem uses this interface to determine if * any page in the mapping is busy, i.e. for DMA, or other * get_user_pages() usages. * * It is expected that the filesystem is holding locks to block the * establishment of new mappings in this address_space. I.e. it expects * to be able to run unmap_mapping_range() and subsequently not race * mapping_mapped() becoming true. */ struct page *dax_layout_busy_page_range(struct address_space *mapping, loff_t start, loff_t end) { void *entry; unsigned int scanned = 0; struct page *page = NULL; pgoff_t start_idx = start >> PAGE_SHIFT; pgoff_t end_idx; XA_STATE(xas, &mapping->i_pages, start_idx); /* * In the 'limited' case get_user_pages() for dax is disabled. */ if (IS_ENABLED(CONFIG_FS_DAX_LIMITED)) return NULL; if (!dax_mapping(mapping) || !mapping_mapped(mapping)) return NULL; /* If end == LLONG_MAX, all pages from start to till end of file */ if (end == LLONG_MAX) end_idx = ULONG_MAX; else end_idx = end >> PAGE_SHIFT; /* * If we race get_user_pages_fast() here either we'll see the * elevated page count in the iteration and wait, or * get_user_pages_fast() will see that the page it took a reference * against is no longer mapped in the page tables and bail to the * get_user_pages() slow path. The slow path is protected by * pte_lock() and pmd_lock(). New references are not taken without * holding those locks, and unmap_mapping_pages() will not zero the * pte or pmd without holding the respective lock, so we are * guaranteed to either see new references or prevent new * references from being established. */ unmap_mapping_pages(mapping, start_idx, end_idx - start_idx + 1, 0); xas_lock_irq(&xas); xas_for_each(&xas, entry, end_idx) { if (WARN_ON_ONCE(!xa_is_value(entry))) continue; if (unlikely(dax_is_locked(entry))) entry = get_unlocked_entry(&xas, 0); if (entry) page = dax_busy_page(entry); put_unlocked_entry(&xas, entry); if (page) break; if (++scanned % XA_CHECK_SCHED) continue; xas_pause(&xas); xas_unlock_irq(&xas); cond_resched(); xas_lock_irq(&xas); } xas_unlock_irq(&xas); return page; } EXPORT_SYMBOL_GPL(dax_layout_busy_page_range); struct page *dax_layout_busy_page(struct address_space *mapping) { return dax_layout_busy_page_range(mapping, 0, LLONG_MAX); } EXPORT_SYMBOL_GPL(dax_layout_busy_page); static int __dax_invalidate_entry(struct address_space *mapping, pgoff_t index, bool trunc) { XA_STATE(xas, &mapping->i_pages, index); int ret = 0; void *entry; xas_lock_irq(&xas); entry = get_unlocked_entry(&xas, 0); if (!entry || WARN_ON_ONCE(!xa_is_value(entry))) goto out; if (!trunc && (xas_get_mark(&xas, PAGECACHE_TAG_DIRTY) || xas_get_mark(&xas, PAGECACHE_TAG_TOWRITE))) goto out; dax_disassociate_entry(entry, mapping, trunc); xas_store(&xas, NULL); mapping->nrexceptional--; ret = 1; out: put_unlocked_entry(&xas, entry); xas_unlock_irq(&xas); return ret; } /* * Delete DAX entry at @index from @mapping. Wait for it * to be unlocked before deleting it. */ int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index) { int ret = __dax_invalidate_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 * page cache (usually fs-private i_mmap_sem for writing). Since the * caller has seen a DAX entry for this index, we better find it * at that index as well... */ WARN_ON_ONCE(!ret); return ret; } /* * Invalidate DAX entry if it is clean. */ int dax_invalidate_mapping_entry_sync(struct address_space *mapping, pgoff_t index) { return __dax_invalidate_entry(mapping, index, false); } static int copy_cow_page_dax(struct block_device *bdev, struct dax_device *dax_dev, sector_t sector, struct page *to, unsigned long vaddr) { void *vto, *kaddr; pgoff_t pgoff; long rc; int id; rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff); if (rc) return rc; id = dax_read_lock(); rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(PAGE_SIZE), &kaddr, NULL); 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_entry(struct xa_state *xas, struct address_space *mapping, struct vm_fault *vmf, void *entry, pfn_t pfn, unsigned long flags, bool dirty) { void *new_entry = dax_make_entry(pfn, flags); if (dirty) __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); if (dax_is_zero_entry(entry) && !(flags & DAX_ZERO_PAGE)) { unsigned long index = xas->xa_index; /* we are replacing a zero page with block mapping */ if (dax_is_pmd_entry(entry)) unmap_mapping_pages(mapping, index & ~PG_PMD_COLOUR, PG_PMD_NR, false); else /* pte entry */ unmap_mapping_pages(mapping, index, 1, false); } xas_reset(xas); xas_lock_irq(xas); if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) { void *old; dax_disassociate_entry(entry, mapping, false); dax_associate_entry(new_entry, mapping, vmf->vma, vmf->address); /* * Only swap our new entry into the page cache if the current * entry is a zero page or an empty entry. If a normal PTE or * PMD entry is already in the cache, 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. */ old = dax_lock_entry(xas, new_entry); WARN_ON_ONCE(old != xa_mk_value(xa_to_value(entry) | DAX_LOCKED)); entry = new_entry; } else { xas_load(xas); /* Walk the xa_state */ } if (dirty) xas_set_mark(xas, PAGECACHE_TAG_DIRTY); xas_unlock_irq(xas); 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_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) { struct mmu_notifier_range range; unsigned long address; cond_resched(); if (!(vma->vm_flags & VM_SHARED)) continue; address = pgoff_address(index, vma); /* * Note because we provide range to follow_pte it will call * mmu_notifier_invalidate_range_start() on our behalf before * taking any lock. */ if (follow_pte(vma->vm_mm, address, &range, &ptep, &pmdp, &ptl)) continue; /* * No need to call mmu_notifier_invalidate_range() as we are * downgrading page table protection not changing it to point * to a new page. * * See Documentation/vm/mmu_notifier.rst */ 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_invalidate(vma, address, pmdp); pmd = pmd_wrprotect(pmd); pmd = pmd_mkclean(pmd); set_pmd_at(vma->vm_mm, address, pmdp, pmd); unlock_pmd: #endif spin_unlock(ptl); } 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); unlock_pte: pte_unmap_unlock(ptep, ptl); } mmu_notifier_invalidate_range_end(&range); } i_mmap_unlock_read(mapping); } static int dax_writeback_one(struct xa_state *xas, struct dax_device *dax_dev, struct address_space *mapping, void *entry) { unsigned long pfn, index, count; long ret = 0; /* * A page got tagged dirty in DAX mapping? Something is seriously * wrong. */ if (WARN_ON(!xa_is_value(entry))) return -EIO; if (unlikely(dax_is_locked(entry))) { void *old_entry = entry; entry = get_unlocked_entry(xas, 0); /* Entry got punched out / reallocated? */ if (!entry || WARN_ON_ONCE(!xa_is_value(entry))) goto put_unlocked; /* * Entry got reallocated elsewhere? No need to writeback. * We have to compare pfns as we must not bail out due to * difference in lockbit or entry type. */ if (dax_to_pfn(old_entry) != dax_to_pfn(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 done this entry */ if (!xas_get_mark(xas, PAGECACHE_TAG_TOWRITE)) goto put_unlocked; } /* Lock the entry to serialize with page faults */ dax_lock_entry(xas, entry); /* * 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 the i_pages lock and once they do that * they will see the entry locked and wait for it to unlock. */ xas_clear_mark(xas, PAGECACHE_TAG_TOWRITE); xas_unlock_irq(xas); /* * If dax_writeback_mapping_range() was given a wbc->range_start * in the middle of a PMD, the 'index' we use needs to be * aligned to the start of the PMD. * This allows us to flush for PMD_SIZE and not have to worry about * partial PMD writebacks. */ pfn = dax_to_pfn(entry); count = 1UL << dax_entry_order(entry); index = xas->xa_index & ~(count - 1); dax_entry_mkclean(mapping, index, pfn); dax_flush(dax_dev, page_address(pfn_to_page(pfn)), count * PAGE_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. */ xas_reset(xas); xas_lock_irq(xas); xas_store(xas, entry); xas_clear_mark(xas, PAGECACHE_TAG_DIRTY); dax_wake_entry(xas, entry, false); trace_dax_writeback_one(mapping->host, index, count); return ret; put_unlocked: put_unlocked_entry(xas, entry); 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 dax_device *dax_dev, struct writeback_control *wbc) { XA_STATE(xas, &mapping->i_pages, wbc->range_start >> PAGE_SHIFT); struct inode *inode = mapping->host; pgoff_t end_index = wbc->range_end >> PAGE_SHIFT; void *entry; int ret = 0; unsigned int scanned = 0; if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT)) return -EIO; if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL) return 0; trace_dax_writeback_range(inode, xas.xa_index, end_index); tag_pages_for_writeback(mapping, xas.xa_index, end_index); xas_lock_irq(&xas); xas_for_each_marked(&xas, entry, end_index, PAGECACHE_TAG_TOWRITE) { ret = dax_writeback_one(&xas, dax_dev, mapping, entry); if (ret < 0) { mapping_set_error(mapping, ret); break; } if (++scanned % XA_CHECK_SCHED) continue; xas_pause(&xas); xas_unlock_irq(&xas); cond_resched(); xas_lock_irq(&xas); } xas_unlock_irq(&xas); trace_dax_writeback_range_done(inode, xas.xa_index, end_index); return ret; } EXPORT_SYMBOL_GPL(dax_writeback_mapping_range); static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos) { return (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9; } static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size, pfn_t *pfnp) { const sector_t sector = dax_iomap_sector(iomap, pos); pgoff_t pgoff; int id, rc; long length; rc = bdev_dax_pgoff(iomap->bdev, sector, size, &pgoff); if (rc) return rc; id = dax_read_lock(); length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size), NULL, pfnp); if (length < 0) { rc = length; goto out; } rc = -EINVAL; if (PFN_PHYS(length) < size) goto out; if (pfn_t_to_pfn(*pfnp) & (PHYS_PFN(size)-1)) goto out; /* For larger pages we need devmap */ if (length > 1 && !pfn_t_devmap(*pfnp)) goto out; rc = 0; out: dax_read_unlock(id); return rc; } /* * 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 vm_fault_t dax_load_hole(struct xa_state *xas, struct address_space *mapping, void **entry, struct vm_fault *vmf) { struct inode *inode = mapping->host; unsigned long vaddr = vmf->address; pfn_t pfn = pfn_to_pfn_t(my_zero_pfn(vaddr)); vm_fault_t ret; *entry = dax_insert_entry(xas, mapping, vmf, *entry, pfn, DAX_ZERO_PAGE, false); ret = vmf_insert_mixed(vmf->vma, vaddr, pfn); trace_dax_load_hole(inode, vmf, ret); return ret; } s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap) { sector_t sector = iomap_sector(iomap, pos & PAGE_MASK); pgoff_t pgoff; long rc, id; void *kaddr; bool page_aligned = false; unsigned offset = offset_in_page(pos); unsigned size = min_t(u64, PAGE_SIZE - offset, length); if (IS_ALIGNED(sector << SECTOR_SHIFT, PAGE_SIZE) && (size == PAGE_SIZE)) page_aligned = true; rc = bdev_dax_pgoff(iomap->bdev, sector, PAGE_SIZE, &pgoff); if (rc) return rc; id = dax_read_lock(); if (page_aligned) rc = dax_zero_page_range(iomap->dax_dev, pgoff, 1); else rc = dax_direct_access(iomap->dax_dev, pgoff, 1, &kaddr, NULL); if (rc < 0) { dax_read_unlock(id); return rc; } if (!page_aligned) { memset(kaddr + offset, 0, size); dax_flush(iomap->dax_dev, kaddr + offset, size); } dax_read_unlock(id); return size; } static loff_t dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data, struct iomap *iomap, struct iomap *srcmap) { 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; size_t xfer; 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; 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, NULL); 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; /* * The userspace address for the memory copy has already been * validated via access_ok() in either vfs_read() or * vfs_write(), depending on which operation we are doing. */ if (iov_iter_rw(iter) == WRITE) xfer = dax_copy_from_iter(dax_dev, pgoff, kaddr, map_len, iter); else xfer = dax_copy_to_iter(dax_dev, pgoff, kaddr, map_len, iter); pos += xfer; length -= xfer; done += xfer; if (xfer == 0) ret = -EFAULT; if (xfer < map_len) break; } 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_write(&inode->i_rwsem); flags |= IOMAP_WRITE; } else { lockdep_assert_held(&inode->i_rwsem); } if (iocb->ki_flags & IOCB_NOWAIT) flags |= IOMAP_NOWAIT; 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 vm_fault_t dax_fault_return(int error) { if (error == 0) return VM_FAULT_NOPAGE; return vmf_error(error); } /* * MAP_SYNC on a dax mapping guarantees dirty metadata is * flushed on write-faults (non-cow), but not read-faults. */ static bool dax_fault_is_synchronous(unsigned long flags, struct vm_area_struct *vma, struct iomap *iomap) { return (flags & IOMAP_WRITE) && (vma->vm_flags & VM_SYNC) && (iomap->flags & IOMAP_F_DIRTY); } static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp, int *iomap_errp, const struct iomap_ops *ops) { struct vm_area_struct *vma = vmf->vma; struct address_space *mapping = vma->vm_file->f_mapping; XA_STATE(xas, &mapping->i_pages, vmf->pgoff); struct inode *inode = mapping->host; unsigned long vaddr = vmf->address; loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT; struct iomap iomap = { .type = IOMAP_HOLE }; struct iomap srcmap = { .type = IOMAP_HOLE }; unsigned flags = IOMAP_FAULT; int error, major = 0; bool write = vmf->flags & FAULT_FLAG_WRITE; bool sync; vm_fault_t ret = 0; void *entry; pfn_t pfn; trace_dax_pte_fault(inode, 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)) { ret = VM_FAULT_SIGBUS; goto out; } if (write && !vmf->cow_page) flags |= IOMAP_WRITE; entry = grab_mapping_entry(&xas, mapping, 0); if (xa_is_internal(entry)) { ret = xa_to_internal(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)) { 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, &srcmap); if (iomap_errp) *iomap_errp = error; if (error) { 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; } if (vmf->cow_page) { sector_t sector = dax_iomap_sector(&iomap, pos); switch (iomap.type) { case IOMAP_HOLE: case IOMAP_UNWRITTEN: clear_user_highpage(vmf->cow_page, vaddr); break; case IOMAP_MAPPED: error = copy_cow_page_dax(iomap.bdev, iomap.dax_dev, sector, vmf->cow_page, vaddr); break; default: WARN_ON_ONCE(1); error = -EIO; break; } if (error) goto error_finish_iomap; __SetPageUptodate(vmf->cow_page); ret = finish_fault(vmf); if (!ret) ret = VM_FAULT_DONE_COW; goto finish_iomap; } sync = dax_fault_is_synchronous(flags, vma, &iomap); switch (iomap.type) { case IOMAP_MAPPED: if (iomap.flags & IOMAP_F_NEW) { count_vm_event(PGMAJFAULT); count_memcg_event_mm(vma->vm_mm, PGMAJFAULT); major = VM_FAULT_MAJOR; } error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn); if (error < 0) goto error_finish_iomap; entry = dax_insert_entry(&xas, mapping, vmf, entry, pfn, 0, write && !sync); /* * If we are doing synchronous page fault and inode needs fsync, * we can insert PTE into page tables only after that happens. * Skip insertion for now and return the pfn so that caller can * insert it after fsync is done. */ if (sync) { if (WARN_ON_ONCE(!pfnp)) { error = -EIO; goto error_finish_iomap; } *pfnp = pfn; ret = VM_FAULT_NEEDDSYNC | major; goto finish_iomap; } trace_dax_insert_mapping(inode, vmf, entry); if (write) ret = vmf_insert_mixed_mkwrite(vma, vaddr, pfn); else ret = vmf_insert_mixed(vma, vaddr, pfn); goto finish_iomap; case IOMAP_UNWRITTEN: case IOMAP_HOLE: if (!write) { ret = dax_load_hole(&xas, mapping, &entry, vmf); goto finish_iomap; } fallthrough; default: WARN_ON_ONCE(1); error = -EIO; break; } error_finish_iomap: ret = dax_fault_return(error); finish_iomap: if (ops->iomap_end) { int copied = PAGE_SIZE; if (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: dax_unlock_entry(&xas, entry); out: trace_dax_pte_fault_done(inode, vmf, ret); return ret | major; } #ifdef CONFIG_FS_DAX_PMD static vm_fault_t dax_pmd_load_hole(struct xa_state *xas, 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 vm_area_struct *vma = vmf->vma; struct inode *inode = mapping->host; pgtable_t pgtable = NULL; struct page *zero_page; spinlock_t *ptl; pmd_t pmd_entry; pfn_t pfn; zero_page = mm_get_huge_zero_page(vmf->vma->vm_mm); if (unlikely(!zero_page)) goto fallback; pfn = page_to_pfn_t(zero_page); *entry = dax_insert_entry(xas, mapping, vmf, *entry, pfn, DAX_PMD | DAX_ZERO_PAGE, false); if (arch_needs_pgtable_deposit()) { pgtable = pte_alloc_one(vma->vm_mm); if (!pgtable) return VM_FAULT_OOM; } ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd); if (!pmd_none(*(vmf->pmd))) { spin_unlock(ptl); goto fallback; } if (pgtable) { pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable); mm_inc_nr_ptes(vma->vm_mm); } 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, *entry); return VM_FAULT_NOPAGE; fallback: if (pgtable) pte_free(vma->vm_mm, pgtable); trace_dax_pmd_load_hole_fallback(inode, vmf, zero_page, *entry); return VM_FAULT_FALLBACK; } static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp, const struct iomap_ops *ops) { struct vm_area_struct *vma = vmf->vma; struct address_space *mapping = vma->vm_file->f_mapping; XA_STATE_ORDER(xas, &mapping->i_pages, vmf->pgoff, PMD_ORDER); unsigned long pmd_addr = vmf->address & PMD_MASK; bool write = vmf->flags & FAULT_FLAG_WRITE; bool sync; unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT; struct inode *inode = mapping->host; vm_fault_t result = VM_FAULT_FALLBACK; struct iomap iomap = { .type = IOMAP_HOLE }; struct iomap srcmap = { .type = IOMAP_HOLE }; pgoff_t max_pgoff; void *entry; loff_t pos; int error; pfn_t pfn; /* * 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. */ max_pgoff = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); 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 page cache. */ 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 (xas.xa_index >= max_pgoff) { result = VM_FAULT_SIGBUS; goto out; } /* If the PMD would extend beyond the file size */ if ((xas.xa_index | PG_PMD_COLOUR) >= max_pgoff) goto fallback; /* * grab_mapping_entry() will make sure we get an empty PMD entry, * a zero PMD entry or a DAX PMD. If it can't (because a PTE * entry is already in the array, for instance), it will return * VM_FAULT_FALLBACK. */ entry = grab_mapping_entry(&xas, mapping, PMD_ORDER); if (xa_is_internal(entry)) { result = xa_to_internal(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)xas.xa_index << PAGE_SHIFT; error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap, &srcmap); if (error) goto unlock_entry; if (iomap.offset + iomap.length < pos + PMD_SIZE) goto finish_iomap; sync = dax_fault_is_synchronous(iomap_flags, vma, &iomap); switch (iomap.type) { case IOMAP_MAPPED: error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn); if (error < 0) goto finish_iomap; entry = dax_insert_entry(&xas, mapping, vmf, entry, pfn, DAX_PMD, write && !sync); /* * If we are doing synchronous page fault and inode needs fsync, * we can insert PMD into page tables only after that happens. * Skip insertion for now and return the pfn so that caller can * insert it after fsync is done. */ if (sync) { if (WARN_ON_ONCE(!pfnp)) goto finish_iomap; *pfnp = pfn; result = VM_FAULT_NEEDDSYNC; goto finish_iomap; } trace_dax_pmd_insert_mapping(inode, vmf, PMD_SIZE, pfn, entry); result = vmf_insert_pfn_pmd(vmf, pfn, write); break; case IOMAP_UNWRITTEN: case IOMAP_HOLE: if (WARN_ON_ONCE(write)) break; result = dax_pmd_load_hole(&xas, 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: dax_unlock_entry(&xas, entry); 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 vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp, 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 * @pe_size: Size of the page to fault in * @pfnp: PFN to insert for synchronous faults if fsync is required * @iomap_errp: Storage for detailed error code in case of error * @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. */ vm_fault_t dax_iomap_fault(struct vm_fault *vmf, enum page_entry_size pe_size, pfn_t *pfnp, int *iomap_errp, const struct iomap_ops *ops) { switch (pe_size) { case PE_SIZE_PTE: return dax_iomap_pte_fault(vmf, pfnp, iomap_errp, ops); case PE_SIZE_PMD: return dax_iomap_pmd_fault(vmf, pfnp, ops); default: return VM_FAULT_FALLBACK; } } EXPORT_SYMBOL_GPL(dax_iomap_fault); /* * dax_insert_pfn_mkwrite - insert PTE or PMD entry into page tables * @vmf: The description of the fault * @pfn: PFN to insert * @order: Order of entry to insert. * * This function inserts a writeable PTE or PMD entry into the page tables * for an mmaped DAX file. It also marks the page cache entry as dirty. */ static vm_fault_t dax_insert_pfn_mkwrite(struct vm_fault *vmf, pfn_t pfn, unsigned int order) { struct address_space *mapping = vmf->vma->vm_file->f_mapping; XA_STATE_ORDER(xas, &mapping->i_pages, vmf->pgoff, order); void *entry; vm_fault_t ret; xas_lock_irq(&xas); entry = get_unlocked_entry(&xas, order); /* Did we race with someone splitting entry or so? */ if (!entry || dax_is_conflict(entry) || (order == 0 && !dax_is_pte_entry(entry))) { put_unlocked_entry(&xas, entry); xas_unlock_irq(&xas); trace_dax_insert_pfn_mkwrite_no_entry(mapping->host, vmf, VM_FAULT_NOPAGE); return VM_FAULT_NOPAGE; } xas_set_mark(&xas, PAGECACHE_TAG_DIRTY); dax_lock_entry(&xas, entry); xas_unlock_irq(&xas); if (order == 0) ret = vmf_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn); #ifdef CONFIG_FS_DAX_PMD else if (order == PMD_ORDER) ret = vmf_insert_pfn_pmd(vmf, pfn, FAULT_FLAG_WRITE); #endif else ret = VM_FAULT_FALLBACK; dax_unlock_entry(&xas, entry); trace_dax_insert_pfn_mkwrite(mapping->host, vmf, ret); return ret; } /** * dax_finish_sync_fault - finish synchronous page fault * @vmf: The description of the fault * @pe_size: Size of entry to be inserted * @pfn: PFN to insert * * This function ensures that the file range touched by the page fault is * stored persistently on the media and handles inserting of appropriate page * table entry. */ vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf, enum page_entry_size pe_size, pfn_t pfn) { int err; loff_t start = ((loff_t)vmf->pgoff) << PAGE_SHIFT; unsigned int order = pe_order(pe_size); size_t len = PAGE_SIZE << order; err = vfs_fsync_range(vmf->vma->vm_file, start, start + len - 1, 1); if (err) return VM_FAULT_SIGBUS; return dax_insert_pfn_mkwrite(vmf, pfn, order); } EXPORT_SYMBOL_GPL(dax_finish_sync_fault);