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Diffstat (limited to 'fs/dax.c')
| -rw-r--r-- | fs/dax.c | 1820 |
1 files changed, 1820 insertions, 0 deletions
diff --git a/fs/dax.c b/fs/dax.c new file mode 100644 index 000000000..7451efc50 --- /dev/null +++ b/fs/dax.c @@ -0,0 +1,1820 @@ +/* + * 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> + * + * 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 <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 "internal.h" + +#define CREATE_TRACE_POINTS +#include <trace/events/fs_dax.h> + +/* 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) + +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); + +/* + * We use lowest available bit in exceptional entry 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 RADIX_DAX_SHIFT (RADIX_TREE_EXCEPTIONAL_SHIFT + 4) +#define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT) +#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1)) +#define RADIX_DAX_ZERO_PAGE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2)) +#define RADIX_DAX_EMPTY (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 3)) + +static unsigned long dax_radix_pfn(void *entry) +{ + return (unsigned long)entry >> RADIX_DAX_SHIFT; +} + +static void *dax_radix_locked_entry(unsigned long pfn, unsigned long flags) +{ + return (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | flags | + (pfn << RADIX_DAX_SHIFT) | RADIX_DAX_ENTRY_LOCK); +} + +static unsigned int dax_radix_order(void *entry) +{ + if ((unsigned long)entry & RADIX_DAX_PMD) + return PMD_SHIFT - PAGE_SHIFT; + return 0; +} + +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 &= ~PG_PMD_COLOUR; + + 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); +} + +/* + * @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_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 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); +} + +/* + * Check whether the given slot is locked. Must be called with the i_pages + * 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->i_pages.xa_lock); + return entry & RADIX_DAX_ENTRY_LOCK; +} + +/* + * Mark the given slot as locked. Must be called with the i_pages 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->i_pages.xa_lock); + + entry |= RADIX_DAX_ENTRY_LOCK; + radix_tree_replace_slot(&mapping->i_pages, slot, (void *)entry); + return (void *)entry; +} + +/* + * Mark the given slot as unlocked. Must be called with the i_pages 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->i_pages.xa_lock); + + entry &= ~(unsigned long)RADIX_DAX_ENTRY_LOCK; + radix_tree_replace_slot(&mapping->i_pages, slot, (void *)entry); + return (void *)entry; +} + +static void put_unlocked_mapping_entry(struct address_space *mapping, + pgoff_t index, 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. + * + * Must be called with the i_pages 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->i_pages, 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); + xa_unlock_irq(&mapping->i_pages); + schedule(); + finish_wait(wq, &ewait.wait); + xa_lock_irq(&mapping->i_pages); + } +} + +/* + * 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 address_space *mapping, pgoff_t index, + void ***slotp, 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(mapping, index, 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); + xa_unlock_irq(&mapping->i_pages); + schedule(); + finish_wait(wq, &ewait.wait); +} + +static void unlock_mapping_entry(struct address_space *mapping, pgoff_t index) +{ + void *entry, **slot; + + xa_lock_irq(&mapping->i_pages); + entry = __radix_tree_lookup(&mapping->i_pages, index, NULL, &slot); + if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) || + !slot_locked(mapping, slot))) { + xa_unlock_irq(&mapping->i_pages); + return; + } + unlock_slot(mapping, slot); + xa_unlock_irq(&mapping->i_pages); + dax_wake_mapping_entry_waiter(mapping, index, entry, false); +} + +static void put_locked_mapping_entry(struct address_space *mapping, + pgoff_t index) +{ + 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); +} + +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_radix_end_pfn(void *entry) +{ + return dax_radix_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_radix_pfn(entry); \ + pfn < dax_radix_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; +} + +bool dax_lock_mapping_entry(struct page *page) +{ + pgoff_t index; + struct inode *inode; + bool did_lock = false; + void *entry = NULL, **slot; + struct address_space *mapping; + + rcu_read_lock(); + for (;;) { + mapping = READ_ONCE(page->mapping); + + 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. + */ + inode = mapping->host; + if (S_ISCHR(inode->i_mode)) { + did_lock = true; + break; + } + + xa_lock_irq(&mapping->i_pages); + if (mapping != page->mapping) { + xa_unlock_irq(&mapping->i_pages); + continue; + } + index = page->index; + + entry = __radix_tree_lookup(&mapping->i_pages, index, + NULL, &slot); + if (!entry) { + xa_unlock_irq(&mapping->i_pages); + break; + } else if (slot_locked(mapping, slot)) { + rcu_read_unlock(); + wait_entry_unlocked(mapping, index, &slot, entry); + rcu_read_lock(); + continue; + } + lock_slot(mapping, slot); + did_lock = true; + xa_unlock_irq(&mapping->i_pages); + break; + } + rcu_read_unlock(); + + return did_lock; +} + +void dax_unlock_mapping_entry(struct page *page) +{ + struct address_space *mapping = page->mapping; + struct inode *inode = mapping->host; + + if (S_ISCHR(inode->i_mode)) + return; + + unlock_mapping_entry(mapping, page->index); +} + +/* + * 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: + xa_lock_irq(&mapping->i_pages); + 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 + * the i_pages lock. + */ + entry = lock_slot(mapping, slot); + } + + xa_unlock_irq(&mapping->i_pages); + /* + * 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_pages(mapping, index & ~PG_PMD_COLOUR, + PG_PMD_NR, false); + + 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); + } + xa_lock_irq(&mapping->i_pages); + + if (!entry) { + /* + * We needed to drop the i_pages 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->i_pages, index, + NULL, &slot); + if (entry) { + radix_tree_preload_end(); + xa_unlock_irq(&mapping->i_pages); + goto restart; + } + } + + if (pmd_downgrade) { + dax_disassociate_entry(entry, mapping, false); + radix_tree_delete(&mapping->i_pages, 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->i_pages, index, + dax_radix_order(entry), entry); + radix_tree_preload_end(); + if (err) { + xa_unlock_irq(&mapping->i_pages); + /* + * 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++; + xa_unlock_irq(&mapping->i_pages); + return entry; + } + entry = lock_slot(mapping, slot); + out_unlock: + xa_unlock_irq(&mapping->i_pages); + return entry; +} + +/** + * dax_layout_busy_page - find first pinned page in @mapping + * @mapping: address space to scan for a page with ref count > 1 + * + * 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(struct address_space *mapping) +{ + pgoff_t indices[PAGEVEC_SIZE]; + struct page *page = NULL; + struct pagevec pvec; + pgoff_t index, end; + unsigned i; + + /* + * 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; + + pagevec_init(&pvec); + index = 0; + end = -1; + + /* + * If we race get_user_pages_fast() here either we'll see the + * elevated page count in the pagevec_lookup 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_range() 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_range(mapping, 0, 0, 0); + + while (index < end && pagevec_lookup_entries(&pvec, mapping, index, + min(end - index, (pgoff_t)PAGEVEC_SIZE), + indices)) { + pgoff_t nr_pages = 1; + + for (i = 0; i < pagevec_count(&pvec); i++) { + struct page *pvec_ent = pvec.pages[i]; + void *entry; + + index = indices[i]; + if (index >= end) + break; + + if (WARN_ON_ONCE( + !radix_tree_exceptional_entry(pvec_ent))) + continue; + + xa_lock_irq(&mapping->i_pages); + entry = get_unlocked_mapping_entry(mapping, index, NULL); + if (entry) { + page = dax_busy_page(entry); + /* + * Account for multi-order entries at + * the end of the pagevec. + */ + if (i + 1 >= pagevec_count(&pvec)) + nr_pages = 1UL << dax_radix_order(entry); + } + put_unlocked_mapping_entry(mapping, index, entry); + xa_unlock_irq(&mapping->i_pages); + if (page) + break; + } + + /* + * We don't expect normal struct page entries to exist in our + * tree, but we keep these pagevec calls so that this code is + * consistent with the common pattern for handling pagevecs + * throughout the kernel. + */ + pagevec_remove_exceptionals(&pvec); + pagevec_release(&pvec); + index += nr_pages; + + if (page) + break; + } + return page; +} +EXPORT_SYMBOL_GPL(dax_layout_busy_page); + +static int __dax_invalidate_mapping_entry(struct address_space *mapping, + pgoff_t index, bool trunc) +{ + int ret = 0; + void *entry; + struct radix_tree_root *pages = &mapping->i_pages; + + xa_lock_irq(pages); + 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(pages, index, PAGECACHE_TAG_DIRTY) || + radix_tree_tag_get(pages, index, PAGECACHE_TAG_TOWRITE))) + goto out; + dax_disassociate_entry(entry, mapping, trunc); + radix_tree_delete(pages, index); + mapping->nrexceptional--; + ret = 1; +out: + put_unlocked_mapping_entry(mapping, index, entry); + xa_unlock_irq(pages); + 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; + 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, 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_mapping_entry(struct address_space *mapping, + struct vm_fault *vmf, + void *entry, pfn_t pfn_t, + unsigned long flags, bool dirty) +{ + struct radix_tree_root *pages = &mapping->i_pages; + unsigned long pfn = pfn_t_to_pfn(pfn_t); + pgoff_t index = vmf->pgoff; + void *new_entry; + + if (dirty) + __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_pages(mapping, index & ~PG_PMD_COLOUR, + PG_PMD_NR, false); + else /* pte entry */ + unmap_mapping_pages(mapping, vmf->pgoff, 1, false); + } + + xa_lock_irq(pages); + new_entry = dax_radix_locked_entry(pfn, flags); + if (dax_entry_size(entry) != dax_entry_size(new_entry)) { + dax_disassociate_entry(entry, mapping, false); + dax_associate_entry(new_entry, mapping, vmf->vma, vmf->address); + } + + 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(pages, index, &node, &slot); + WARN_ON_ONCE(ret != entry); + __radix_tree_replace(pages, node, slot, + new_entry, NULL); + entry = new_entry; + } + + if (dirty) + radix_tree_tag_set(pages, index, PAGECACHE_TAG_DIRTY); + + xa_unlock_irq(pages); + 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; + + /* + * 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_range(vma, address, + address + HPAGE_PMD_SIZE); + 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(vma->vm_mm, start, end); + } + i_mmap_unlock_read(mapping); +} + +static int dax_writeback_one(struct dax_device *dax_dev, + struct address_space *mapping, pgoff_t index, void *entry) +{ + struct radix_tree_root *pages = &mapping->i_pages; + void *entry2, **slot; + unsigned long pfn; + long ret = 0; + size_t size; + + /* + * A page got tagged dirty in DAX mapping? Something is seriously + * wrong. + */ + if (WARN_ON(!radix_tree_exceptional_entry(entry))) + return -EIO; + + xa_lock_irq(pages); + 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 pfns as we must not bail out due to difference in lockbit + * or entry type. + */ + if (dax_radix_pfn(entry2) != dax_radix_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 written back this entry */ + if (!radix_tree_tag_get(pages, 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 the i_pages lock and once they do that + * they will see the entry locked and wait for it to unlock. + */ + radix_tree_tag_clear(pages, index, PAGECACHE_TAG_TOWRITE); + xa_unlock_irq(pages); + + /* + * 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 pfn we pull from 'entry'. + * This allows us to flush for PMD_SIZE and not have to worry about + * partial PMD writebacks. + */ + pfn = dax_radix_pfn(entry); + size = PAGE_SIZE << dax_radix_order(entry); + + dax_mapping_entry_mkclean(mapping, index, pfn); + dax_flush(dax_dev, page_address(pfn_to_page(pfn)), 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. + */ + xa_lock_irq(pages); + radix_tree_tag_clear(pages, index, PAGECACHE_TAG_DIRTY); + xa_unlock_irq(pages); + trace_dax_writeback_one(mapping->host, index, size >> PAGE_SHIFT); + put_locked_mapping_entry(mapping, index); + return ret; + + put_unlocked: + put_unlocked_mapping_entry(mapping, index, entry2); + xa_unlock_irq(pages); + 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); + 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(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 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 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; + + dax_insert_mapping_entry(mapping, vmf, entry, pfn, RADIX_DAX_ZERO_PAGE, + false); + ret = vmf_insert_mixed(vmf->vma, vaddr, pfn); + 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; + + 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, NULL); + if (rc < 0) { + dax_read_unlock(id); + return rc; + } + memset(kaddr + offset, 0, size); + dax_flush(dax_dev, kaddr + offset, size); + dax_read_unlock(id); + } + return 0; +} +EXPORT_SYMBOL_GPL(__dax_zero_page_range); + +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; + 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_exclusive(&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; + if (error == -ENOMEM) + return VM_FAULT_OOM; + return VM_FAULT_SIGBUS; +} + +/* + * 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; + struct inode *inode = mapping->host; + unsigned long vaddr = vmf->address; + loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT; + struct iomap iomap = { 0 }; + 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(mapping, vmf->pgoff, 0); + if (IS_ERR(entry)) { + 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)) { + 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 (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_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); + 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_mapping_entry(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(mapping, entry, vmf); + goto finish_iomap; + } + /*FALLTHRU*/ + 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: + put_locked_mapping_entry(mapping, vmf->pgoff); + 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 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; + 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); + ret = dax_insert_mapping_entry(mapping, vmf, entry, pfn, + RADIX_DAX_PMD | RADIX_DAX_ZERO_PAGE, false); + + 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 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; + 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 = { 0 }; + pgoff_t max_pgoff, 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. + */ + pgoff = linear_page_index(vma, pmd_addr); + 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 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; + + 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_mapping_entry(mapping, vmf, entry, pfn, + RADIX_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(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 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 + * @pe_size: Size of entry to be inserted + * @pfn: PFN to insert + * + * This function inserts writeable PTE or PMD entry into page tables for mmaped + * DAX file. It takes care of marking corresponding radix tree entry as dirty + * as well. + */ +static vm_fault_t dax_insert_pfn_mkwrite(struct vm_fault *vmf, + enum page_entry_size pe_size, + pfn_t pfn) +{ + struct address_space *mapping = vmf->vma->vm_file->f_mapping; + void *entry, **slot; + pgoff_t index = vmf->pgoff; + vm_fault_t ret; + + xa_lock_irq(&mapping->i_pages); + entry = get_unlocked_mapping_entry(mapping, index, &slot); + /* Did we race with someone splitting entry or so? */ + if (!entry || + (pe_size == PE_SIZE_PTE && !dax_is_pte_entry(entry)) || + (pe_size == PE_SIZE_PMD && !dax_is_pmd_entry(entry))) { + put_unlocked_mapping_entry(mapping, index, entry); + xa_unlock_irq(&mapping->i_pages); + trace_dax_insert_pfn_mkwrite_no_entry(mapping->host, vmf, + VM_FAULT_NOPAGE); + return VM_FAULT_NOPAGE; + } + radix_tree_tag_set(&mapping->i_pages, index, PAGECACHE_TAG_DIRTY); + entry = lock_slot(mapping, slot); + xa_unlock_irq(&mapping->i_pages); + switch (pe_size) { + case PE_SIZE_PTE: + ret = vmf_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn); + break; +#ifdef CONFIG_FS_DAX_PMD + case PE_SIZE_PMD: + ret = vmf_insert_pfn_pmd(vmf, pfn, FAULT_FLAG_WRITE); + break; +#endif + default: + ret = VM_FAULT_FALLBACK; + } + put_locked_mapping_entry(mapping, index); + 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; + size_t len = 0; + + if (pe_size == PE_SIZE_PTE) + len = PAGE_SIZE; + else if (pe_size == PE_SIZE_PMD) + len = PMD_SIZE; + else + WARN_ON_ONCE(1); + 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, pe_size, pfn); +} +EXPORT_SYMBOL_GPL(dax_finish_sync_fault); |