diff options
Diffstat (limited to 'fs/dax.c')
-rw-r--r-- | fs/dax.c | 1320 |
1 files changed, 597 insertions, 723 deletions
@@ -31,28 +31,15 @@ #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" -/* - * We use lowest available bit in exceptional entry for locking, other two - * bits to determine entry type. In total 3 special bits. - */ -#define RADIX_DAX_SHIFT (RADIX_TREE_EXCEPTIONAL_SHIFT + 3) -#define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1)) -#define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2)) -#define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD) -#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK) -#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT)) -#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \ - RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \ - RADIX_TREE_EXCEPTIONAL_ENTRY)) - /* 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) -wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES]; +static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES]; static int __init init_dax_wait_table(void) { @@ -64,14 +51,6 @@ static int __init init_dax_wait_table(void) } fs_initcall(init_dax_wait_table); -static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping, - pgoff_t index) -{ - unsigned long hash = hash_long((unsigned long)mapping ^ index, - DAX_WAIT_TABLE_BITS); - return wait_table + hash; -} - static long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax) { struct request_queue *q = bdev->bd_queue; @@ -98,209 +77,52 @@ static void dax_unmap_atomic(struct block_device *bdev, blk_queue_exit(bdev->bd_queue); } -struct page *read_dax_sector(struct block_device *bdev, sector_t n) +static int dax_is_pmd_entry(void *entry) { - struct page *page = alloc_pages(GFP_KERNEL, 0); - struct blk_dax_ctl dax = { - .size = PAGE_SIZE, - .sector = n & ~((((int) PAGE_SIZE) / 512) - 1), - }; - long rc; - - if (!page) - return ERR_PTR(-ENOMEM); - - rc = dax_map_atomic(bdev, &dax); - if (rc < 0) - return ERR_PTR(rc); - memcpy_from_pmem(page_address(page), dax.addr, PAGE_SIZE); - dax_unmap_atomic(bdev, &dax); - return page; + return (unsigned long)entry & RADIX_DAX_PMD; } -static bool buffer_written(struct buffer_head *bh) +static int dax_is_pte_entry(void *entry) { - return buffer_mapped(bh) && !buffer_unwritten(bh); + return !((unsigned long)entry & RADIX_DAX_PMD); } -/* - * When ext4 encounters a hole, it returns without modifying the buffer_head - * which means that we can't trust b_size. To cope with this, we set b_state - * to 0 before calling get_block and, if any bit is set, we know we can trust - * b_size. Unfortunate, really, since ext4 knows precisely how long a hole is - * and would save us time calling get_block repeatedly. - */ -static bool buffer_size_valid(struct buffer_head *bh) +static int dax_is_zero_entry(void *entry) { - return bh->b_state != 0; + return (unsigned long)entry & RADIX_DAX_HZP; } - -static sector_t to_sector(const struct buffer_head *bh, - const struct inode *inode) +static int dax_is_empty_entry(void *entry) { - sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9); - - return sector; + return (unsigned long)entry & RADIX_DAX_EMPTY; } -static ssize_t dax_io(struct inode *inode, struct iov_iter *iter, - loff_t start, loff_t end, get_block_t get_block, - struct buffer_head *bh) +struct page *read_dax_sector(struct block_device *bdev, sector_t n) { - loff_t pos = start, max = start, bh_max = start; - bool hole = false; - struct block_device *bdev = NULL; - int rw = iov_iter_rw(iter), rc; - long map_len = 0; + struct page *page = alloc_pages(GFP_KERNEL, 0); struct blk_dax_ctl dax = { - .addr = ERR_PTR(-EIO), + .size = PAGE_SIZE, + .sector = n & ~((((int) PAGE_SIZE) / 512) - 1), }; - unsigned blkbits = inode->i_blkbits; - sector_t file_blks = (i_size_read(inode) + (1 << blkbits) - 1) - >> blkbits; - - if (rw == READ) - end = min(end, i_size_read(inode)); - - while (pos < end) { - size_t len; - if (pos == max) { - long page = pos >> PAGE_SHIFT; - sector_t block = page << (PAGE_SHIFT - blkbits); - unsigned first = pos - (block << blkbits); - long size; - - if (pos == bh_max) { - bh->b_size = PAGE_ALIGN(end - pos); - bh->b_state = 0; - rc = get_block(inode, block, bh, rw == WRITE); - if (rc) - break; - if (!buffer_size_valid(bh)) - bh->b_size = 1 << blkbits; - bh_max = pos - first + bh->b_size; - bdev = bh->b_bdev; - /* - * We allow uninitialized buffers for writes - * beyond EOF as those cannot race with faults - */ - WARN_ON_ONCE( - (buffer_new(bh) && block < file_blks) || - (rw == WRITE && buffer_unwritten(bh))); - } else { - unsigned done = bh->b_size - - (bh_max - (pos - first)); - bh->b_blocknr += done >> blkbits; - bh->b_size -= done; - } - - hole = rw == READ && !buffer_written(bh); - if (hole) { - size = bh->b_size - first; - } else { - dax_unmap_atomic(bdev, &dax); - dax.sector = to_sector(bh, inode); - dax.size = bh->b_size; - map_len = dax_map_atomic(bdev, &dax); - if (map_len < 0) { - rc = map_len; - break; - } - dax.addr += first; - size = map_len - first; - } - /* - * pos + size is one past the last offset for IO, - * so pos + size can overflow loff_t at extreme offsets. - * Cast to u64 to catch this and get the true minimum. - */ - max = min_t(u64, pos + size, end); - } - - if (iov_iter_rw(iter) == WRITE) { - len = copy_from_iter_pmem(dax.addr, max - pos, iter); - } else if (!hole) - len = copy_to_iter((void __force *) dax.addr, max - pos, - iter); - else - len = iov_iter_zero(max - pos, iter); - - if (!len) { - rc = -EFAULT; - break; - } + long rc; - pos += len; - if (!IS_ERR(dax.addr)) - dax.addr += len; - } + if (!page) + return ERR_PTR(-ENOMEM); + rc = dax_map_atomic(bdev, &dax); + if (rc < 0) + return ERR_PTR(rc); + memcpy_from_pmem(page_address(page), dax.addr, PAGE_SIZE); dax_unmap_atomic(bdev, &dax); - - return (pos == start) ? rc : pos - start; -} - -/** - * dax_do_io - Perform I/O to a DAX file - * @iocb: The control block for this I/O - * @inode: The file which the I/O is directed at - * @iter: The addresses to do I/O from or to - * @get_block: The filesystem method used to translate file offsets to blocks - * @end_io: A filesystem callback for I/O completion - * @flags: See below - * - * This function uses the same locking scheme as do_blockdev_direct_IO: - * If @flags has DIO_LOCKING set, we assume that the i_mutex is held by the - * caller for writes. For reads, we take and release the i_mutex ourselves. - * If DIO_LOCKING is not set, the filesystem takes care of its own locking. - * As with do_blockdev_direct_IO(), we increment i_dio_count while the I/O - * is in progress. - */ -ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode, - struct iov_iter *iter, get_block_t get_block, - dio_iodone_t end_io, int flags) -{ - struct buffer_head bh; - ssize_t retval = -EINVAL; - loff_t pos = iocb->ki_pos; - loff_t end = pos + iov_iter_count(iter); - - memset(&bh, 0, sizeof(bh)); - bh.b_bdev = inode->i_sb->s_bdev; - - if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ) - inode_lock(inode); - - /* Protects against truncate */ - if (!(flags & DIO_SKIP_DIO_COUNT)) - inode_dio_begin(inode); - - retval = dax_io(inode, iter, pos, end, get_block, &bh); - - if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ) - inode_unlock(inode); - - if (end_io) { - int err; - - err = end_io(iocb, pos, retval, bh.b_private); - if (err) - retval = err; - } - - if (!(flags & DIO_SKIP_DIO_COUNT)) - inode_dio_end(inode); - return retval; + return page; } -EXPORT_SYMBOL_GPL(dax_do_io); /* * DAX radix tree locking */ struct exceptional_entry_key { struct address_space *mapping; - unsigned long index; + pgoff_t entry_start; }; struct wait_exceptional_entry_queue { @@ -308,6 +130,26 @@ struct wait_exceptional_entry_queue { struct exceptional_entry_key key; }; +static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping, + pgoff_t index, void *entry, struct exceptional_entry_key *key) +{ + unsigned long hash; + + /* + * If 'entry' is a PMD, align the 'index' that we use for the wait + * queue to the start of that PMD. This ensures that all offsets in + * the range covered by the PMD map to the same bit lock. + */ + if (dax_is_pmd_entry(entry)) + index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1); + + key->mapping = mapping; + key->entry_start = index; + + hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS); + return wait_table + hash; +} + static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode, int sync, void *keyp) { @@ -316,7 +158,7 @@ static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode, container_of(wait, struct wait_exceptional_entry_queue, wait); if (key->mapping != ewait->key.mapping || - key->index != ewait->key.index) + key->entry_start != ewait->key.entry_start) return 0; return autoremove_wake_function(wait, mode, sync, NULL); } @@ -342,7 +184,7 @@ static inline void *lock_slot(struct address_space *mapping, void **slot) radix_tree_deref_slot_protected(slot, &mapping->tree_lock); entry |= RADIX_DAX_ENTRY_LOCK; - radix_tree_replace_slot(slot, (void *)entry); + radix_tree_replace_slot(&mapping->page_tree, slot, (void *)entry); return (void *)entry; } @@ -356,7 +198,7 @@ static inline void *unlock_slot(struct address_space *mapping, void **slot) radix_tree_deref_slot_protected(slot, &mapping->tree_lock); entry &= ~(unsigned long)RADIX_DAX_ENTRY_LOCK; - radix_tree_replace_slot(slot, (void *)entry); + radix_tree_replace_slot(&mapping->page_tree, slot, (void *)entry); return (void *)entry; } @@ -372,24 +214,24 @@ static inline void *unlock_slot(struct address_space *mapping, void **slot) static void *get_unlocked_mapping_entry(struct address_space *mapping, pgoff_t index, void ***slotp) { - void *ret, **slot; + void *entry, **slot; struct wait_exceptional_entry_queue ewait; - wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index); + wait_queue_head_t *wq; init_wait(&ewait.wait); ewait.wait.func = wake_exceptional_entry_func; - ewait.key.mapping = mapping; - ewait.key.index = index; for (;;) { - ret = __radix_tree_lookup(&mapping->page_tree, index, NULL, + entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot); - if (!ret || !radix_tree_exceptional_entry(ret) || + if (!entry || !radix_tree_exceptional_entry(entry) || !slot_locked(mapping, slot)) { if (slotp) *slotp = slot; - return ret; + return entry; } + + wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key); prepare_to_wait_exclusive(wq, &ewait.wait, TASK_UNINTERRUPTIBLE); spin_unlock_irq(&mapping->tree_lock); @@ -399,52 +241,173 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping, } } +static void dax_unlock_mapping_entry(struct address_space *mapping, + pgoff_t index) +{ + void *entry, **slot; + + spin_lock_irq(&mapping->tree_lock); + entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot); + if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) || + !slot_locked(mapping, slot))) { + spin_unlock_irq(&mapping->tree_lock); + return; + } + unlock_slot(mapping, slot); + spin_unlock_irq(&mapping->tree_lock); + dax_wake_mapping_entry_waiter(mapping, index, entry, false); +} + +static void put_locked_mapping_entry(struct address_space *mapping, + pgoff_t index, void *entry) +{ + if (!radix_tree_exceptional_entry(entry)) { + unlock_page(entry); + put_page(entry); + } else { + dax_unlock_mapping_entry(mapping, index); + } +} + +/* + * Called when we are done with radix tree entry we looked up via + * get_unlocked_mapping_entry() and which we didn't lock in the end. + */ +static void put_unlocked_mapping_entry(struct address_space *mapping, + pgoff_t index, void *entry) +{ + if (!radix_tree_exceptional_entry(entry)) + return; + + /* We have to wake up next waiter for the radix tree entry lock */ + dax_wake_mapping_entry_waiter(mapping, index, entry, false); +} + /* * Find radix tree entry at given index. If it points to a page, return with * the page locked. If it points to the exceptional entry, return with the * radix tree entry locked. If the radix tree doesn't contain given index, * create 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 (either zero pages or DAX 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) +static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index, + unsigned long size_flag) { - void *ret, **slot; + bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */ + void *entry, **slot; restart: spin_lock_irq(&mapping->tree_lock); - ret = get_unlocked_mapping_entry(mapping, index, &slot); + entry = get_unlocked_mapping_entry(mapping, index, &slot); + + if (entry) { + if (size_flag & RADIX_DAX_PMD) { + if (!radix_tree_exceptional_entry(entry) || + 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 (radix_tree_exceptional_entry(entry) && + 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 (!ret) { + if (!entry || pmd_downgrade) { int err; + if (pmd_downgrade) { + /* + * Make sure 'entry' remains valid while we drop + * mapping->tree_lock. + */ + entry = lock_slot(mapping, slot); + } + spin_unlock_irq(&mapping->tree_lock); + /* + * Besides huge zero pages the only other thing that gets + * downgraded are empty entries which don't need to be + * unmapped. + */ + if (pmd_downgrade && dax_is_zero_entry(entry)) + unmap_mapping_range(mapping, + (index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0); + err = radix_tree_preload( mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM); - if (err) + if (err) { + if (pmd_downgrade) + put_locked_mapping_entry(mapping, index, entry); return ERR_PTR(err); - ret = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | - RADIX_DAX_ENTRY_LOCK); + } spin_lock_irq(&mapping->tree_lock); - err = radix_tree_insert(&mapping->page_tree, index, ret); + + if (pmd_downgrade) { + radix_tree_delete(&mapping->page_tree, index); + mapping->nrexceptional--; + dax_wake_mapping_entry_waiter(mapping, index, entry, + true); + } + + entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY); + + err = __radix_tree_insert(&mapping->page_tree, index, + dax_radix_order(entry), entry); radix_tree_preload_end(); if (err) { spin_unlock_irq(&mapping->tree_lock); - /* Someone already created the entry? */ - if (err == -EEXIST) + /* + * Someone already created the entry? This is a + * normal failure when inserting PMDs in a range + * that already contains PTEs. In that case we want + * to return -EEXIST immediately. + */ + if (err == -EEXIST && !(size_flag & RADIX_DAX_PMD)) goto restart; + /* + * Our insertion of a DAX PMD entry failed, most + * likely because it collided with a PTE sized entry + * at a different index in the PMD range. We haven't + * inserted anything into the radix tree and have no + * waiters to wake. + */ return ERR_PTR(err); } /* Good, we have inserted empty locked entry into the tree. */ mapping->nrexceptional++; spin_unlock_irq(&mapping->tree_lock); - return ret; + return entry; } /* Normal page in radix tree? */ - if (!radix_tree_exceptional_entry(ret)) { - struct page *page = ret; + if (!radix_tree_exceptional_entry(entry)) { + struct page *page = entry; get_page(page); spin_unlock_irq(&mapping->tree_lock); @@ -457,15 +420,26 @@ restart: } return page; } - ret = lock_slot(mapping, slot); + entry = lock_slot(mapping, slot); + out_unlock: spin_unlock_irq(&mapping->tree_lock); - return ret; + return entry; } +/* + * We do not necessarily hold the mapping->tree_lock when we call this + * function so it is possible that 'entry' is no longer a valid item in the + * radix tree. This is okay because all we really need to do is to find the + * correct waitqueue where tasks might be waiting for that old 'entry' and + * wake them. + */ void dax_wake_mapping_entry_waiter(struct address_space *mapping, - pgoff_t index, bool wake_all) + pgoff_t index, void *entry, bool wake_all) { - wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index); + 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 @@ -473,54 +447,8 @@ void dax_wake_mapping_entry_waiter(struct address_space *mapping, * 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)) { - struct exceptional_entry_key key; - - key.mapping = mapping; - key.index = index; + if (waitqueue_active(wq)) __wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key); - } -} - -void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index) -{ - void *ret, **slot; - - spin_lock_irq(&mapping->tree_lock); - ret = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot); - if (WARN_ON_ONCE(!ret || !radix_tree_exceptional_entry(ret) || - !slot_locked(mapping, slot))) { - spin_unlock_irq(&mapping->tree_lock); - return; - } - unlock_slot(mapping, slot); - spin_unlock_irq(&mapping->tree_lock); - dax_wake_mapping_entry_waiter(mapping, index, false); -} - -static void put_locked_mapping_entry(struct address_space *mapping, - pgoff_t index, void *entry) -{ - if (!radix_tree_exceptional_entry(entry)) { - unlock_page(entry); - put_page(entry); - } else { - dax_unlock_mapping_entry(mapping, index); - } -} - -/* - * Called when we are done with radix tree entry we looked up via - * get_unlocked_mapping_entry() and which we didn't lock in the end. - */ -static void put_unlocked_mapping_entry(struct address_space *mapping, - pgoff_t index, void *entry) -{ - if (!radix_tree_exceptional_entry(entry)) - return; - - /* We have to wake up next waiter for the radix tree entry lock */ - dax_wake_mapping_entry_waiter(mapping, index, false); } /* @@ -547,7 +475,7 @@ int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index) radix_tree_delete(&mapping->page_tree, index); mapping->nrexceptional--; spin_unlock_irq(&mapping->tree_lock); - dax_wake_mapping_entry_waiter(mapping, index, true); + dax_wake_mapping_entry_waiter(mapping, index, entry, true); return 1; } @@ -574,10 +502,8 @@ static int dax_load_hole(struct address_space *mapping, void *entry, /* This will replace locked radix tree entry with a hole page */ page = find_or_create_page(mapping, vmf->pgoff, vmf->gfp_mask | __GFP_ZERO); - if (!page) { - put_locked_mapping_entry(mapping, vmf->pgoff, entry); + if (!page) return VM_FAULT_OOM; - } vmf->page = page; return VM_FAULT_LOCKED; } @@ -600,11 +526,17 @@ static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size return 0; } -#define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT)) - +/* + * By this point grab_mapping_entry() has ensured that we have a locked entry + * of the appropriate size so we don't have to worry about downgrading PMDs to + * PTEs. If we happen to be trying to insert a PTE and there is a PMD + * already in the tree, we will skip the insertion and just dirty the PMD as + * appropriate. + */ static void *dax_insert_mapping_entry(struct address_space *mapping, struct vm_fault *vmf, - void *entry, sector_t sector) + void *entry, sector_t sector, + unsigned long flags) { struct radix_tree_root *page_tree = &mapping->page_tree; int error = 0; @@ -627,28 +559,43 @@ static void *dax_insert_mapping_entry(struct address_space *mapping, error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM); if (error) return ERR_PTR(error); + } else if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_HZP)) { + /* replacing huge zero page with PMD block mapping */ + unmap_mapping_range(mapping, + (vmf->pgoff << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0); } spin_lock_irq(&mapping->tree_lock); - new_entry = (void *)((unsigned long)RADIX_DAX_ENTRY(sector, false) | - RADIX_DAX_ENTRY_LOCK); + new_entry = dax_radix_locked_entry(sector, flags); + if (hole_fill) { __delete_from_page_cache(entry, NULL); /* Drop pagecache reference */ put_page(entry); - error = radix_tree_insert(page_tree, index, new_entry); + error = __radix_tree_insert(page_tree, index, + dax_radix_order(new_entry), new_entry); if (error) { new_entry = ERR_PTR(error); goto unlock; } mapping->nrexceptional++; - } else { + } else if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) { + /* + * Only swap our new entry into the radix tree if the current + * entry is a zero page or an empty entry. If a normal PTE or + * PMD entry is already in the tree, we leave it alone. This + * means that if we are trying to insert a PTE and the + * existing entry is a PMD, we will just leave the PMD in the + * tree and dirty it if necessary. + */ + struct radix_tree_node *node; void **slot; void *ret; - ret = __radix_tree_lookup(page_tree, index, NULL, &slot); + ret = __radix_tree_lookup(page_tree, index, &node, &slot); WARN_ON_ONCE(ret != entry); - radix_tree_replace_slot(slot, new_entry); + __radix_tree_replace(page_tree, node, slot, + new_entry, NULL, NULL); } if (vmf->flags & FAULT_FLAG_WRITE) radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY); @@ -668,63 +615,150 @@ static void *dax_insert_mapping_entry(struct address_space *mapping, return new_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 *ptep; + pte_t pte; + spinlock_t *ptl; + bool changed; + + i_mmap_lock_read(mapping); + vma_interval_tree_foreach(vma, &mapping->i_mmap, index, index) { + unsigned long address; + + cond_resched(); + + if (!(vma->vm_flags & VM_SHARED)) + continue; + + address = pgoff_address(index, vma); + changed = false; + if (follow_pte(vma->vm_mm, address, &ptep, &ptl)) + continue; + if (pfn != pte_pfn(*ptep)) + goto unlock; + if (!pte_dirty(*ptep) && !pte_write(*ptep)) + goto unlock; + + 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); + changed = true; +unlock: + pte_unmap_unlock(ptep, ptl); + + if (changed) + mmu_notifier_invalidate_page(vma->vm_mm, address); + } + i_mmap_unlock_read(mapping); +} + static int dax_writeback_one(struct block_device *bdev, struct address_space *mapping, pgoff_t index, void *entry) { struct radix_tree_root *page_tree = &mapping->page_tree; - int type = RADIX_DAX_TYPE(entry); - struct radix_tree_node *node; struct blk_dax_ctl dax; - void **slot; + void *entry2, **slot; int ret = 0; - spin_lock_irq(&mapping->tree_lock); /* - * Regular page slots are stabilized by the page lock even - * without the tree itself locked. These unlocked entries - * need verification under the tree lock. + * A page got tagged dirty in DAX mapping? Something is seriously + * wrong. */ - if (!__radix_tree_lookup(page_tree, index, &node, &slot)) - goto unlock; - if (*slot != entry) - goto unlock; - - /* another fsync thread may have already written back this entry */ - if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE)) - goto unlock; + if (WARN_ON(!radix_tree_exceptional_entry(entry))) + return -EIO; - if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) { + spin_lock_irq(&mapping->tree_lock); + entry2 = get_unlocked_mapping_entry(mapping, index, &slot); + /* Entry got punched out / reallocated? */ + if (!entry2 || !radix_tree_exceptional_entry(entry2)) + goto put_unlocked; + /* + * Entry got reallocated elsewhere? No need to writeback. We have to + * compare sectors as we must not bail out due to difference in lockbit + * or entry type. + */ + if (dax_radix_sector(entry2) != dax_radix_sector(entry)) + goto put_unlocked; + if (WARN_ON_ONCE(dax_is_empty_entry(entry) || + dax_is_zero_entry(entry))) { ret = -EIO; - goto unlock; + goto put_unlocked; } - dax.sector = RADIX_DAX_SECTOR(entry); - dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE); + /* Another fsync thread may have already written back this entry */ + if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE)) + goto put_unlocked; + /* Lock the entry to serialize with page faults */ + entry = lock_slot(mapping, slot); + /* + * We can clear the tag now but we have to be careful so that concurrent + * dax_writeback_one() calls for the same index cannot finish before we + * actually flush the caches. This is achieved as the calls will look + * at the entry only under tree_lock and once they do that they will + * see the entry locked and wait for it to unlock. + */ + radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE); spin_unlock_irq(&mapping->tree_lock); /* + * Even if dax_writeback_mapping_range() was given a wbc->range_start + * in the middle of a PMD, the 'index' we are given will be aligned to + * the start index of the PMD, as will the sector we pull from + * 'entry'. This allows us to flush for PMD_SIZE and not have to + * worry about partial PMD writebacks. + */ + dax.sector = dax_radix_sector(entry); + dax.size = PAGE_SIZE << dax_radix_order(entry); + + /* * We cannot hold tree_lock while calling dax_map_atomic() because it * eventually calls cond_resched(). */ ret = dax_map_atomic(bdev, &dax); - if (ret < 0) + if (ret < 0) { + put_locked_mapping_entry(mapping, index, entry); return ret; + } if (WARN_ON_ONCE(ret < dax.size)) { ret = -EIO; goto unmap; } + dax_mapping_entry_mkclean(mapping, index, pfn_t_to_pfn(dax.pfn)); wb_cache_pmem(dax.addr, dax.size); - + /* + * After we have flushed the cache, we can clear the dirty tag. There + * cannot be new dirty data in the pfn after the flush has completed as + * the pfn mappings are writeprotected and fault waits for mapping + * entry lock. + */ spin_lock_irq(&mapping->tree_lock); - radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE); + radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_DIRTY); spin_unlock_irq(&mapping->tree_lock); unmap: dax_unmap_atomic(bdev, &dax); + put_locked_mapping_entry(mapping, index, entry); return ret; - unlock: + put_unlocked: + put_unlocked_mapping_entry(mapping, index, entry2); spin_unlock_irq(&mapping->tree_lock); return ret; } @@ -738,12 +772,11 @@ 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, pmd_index; + pgoff_t start_index, end_index; pgoff_t indices[PAGEVEC_SIZE]; struct pagevec pvec; bool done = false; int i, ret = 0; - void *entry; if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT)) return -EIO; @@ -753,15 +786,6 @@ int dax_writeback_mapping_range(struct address_space *mapping, start_index = wbc->range_start >> PAGE_SHIFT; end_index = wbc->range_end >> PAGE_SHIFT; - pmd_index = DAX_PMD_INDEX(start_index); - - rcu_read_lock(); - entry = radix_tree_lookup(&mapping->page_tree, pmd_index); - rcu_read_unlock(); - - /* see if the start of our range is covered by a PMD entry */ - if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD) - start_index = pmd_index; tag_pages_for_writeback(mapping, start_index, end_index); @@ -794,7 +818,7 @@ static int dax_insert_mapping(struct address_space *mapping, struct block_device *bdev, sector_t sector, size_t size, void **entryp, struct vm_area_struct *vma, struct vm_fault *vmf) { - unsigned long vaddr = (unsigned long)vmf->virtual_address; + unsigned long vaddr = vmf->address; struct blk_dax_ctl dax = { .sector = sector, .size = size, @@ -806,7 +830,7 @@ static int dax_insert_mapping(struct address_space *mapping, return PTR_ERR(dax.addr); dax_unmap_atomic(bdev, &dax); - ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector); + ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector, 0); if (IS_ERR(ret)) return PTR_ERR(ret); *entryp = ret; @@ -815,323 +839,6 @@ static int dax_insert_mapping(struct address_space *mapping, } /** - * dax_fault - handle a page fault on a DAX file - * @vma: The virtual memory area where the fault occurred - * @vmf: The description of the fault - * @get_block: The filesystem method used to translate file offsets to blocks - * - * When a page fault occurs, filesystems may call this helper in their - * fault handler for DAX files. dax_fault() assumes the caller has done all - * the necessary locking for the page fault to proceed successfully. - */ -int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, - get_block_t get_block) -{ - struct file *file = vma->vm_file; - struct address_space *mapping = file->f_mapping; - struct inode *inode = mapping->host; - void *entry; - struct buffer_head bh; - unsigned long vaddr = (unsigned long)vmf->virtual_address; - unsigned blkbits = inode->i_blkbits; - sector_t block; - pgoff_t size; - int error; - int major = 0; - - /* - * 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. - */ - size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; - if (vmf->pgoff >= size) - return VM_FAULT_SIGBUS; - - memset(&bh, 0, sizeof(bh)); - block = (sector_t)vmf->pgoff << (PAGE_SHIFT - blkbits); - bh.b_bdev = inode->i_sb->s_bdev; - bh.b_size = PAGE_SIZE; - - entry = grab_mapping_entry(mapping, vmf->pgoff); - if (IS_ERR(entry)) { - error = PTR_ERR(entry); - goto out; - } - - error = get_block(inode, block, &bh, 0); - if (!error && (bh.b_size < PAGE_SIZE)) - error = -EIO; /* fs corruption? */ - if (error) - goto unlock_entry; - - if (vmf->cow_page) { - struct page *new_page = vmf->cow_page; - if (buffer_written(&bh)) - error = copy_user_dax(bh.b_bdev, to_sector(&bh, inode), - bh.b_size, new_page, vaddr); - else - clear_user_highpage(new_page, vaddr); - if (error) - goto unlock_entry; - if (!radix_tree_exceptional_entry(entry)) { - vmf->page = entry; - return VM_FAULT_LOCKED; - } - vmf->entry = entry; - return VM_FAULT_DAX_LOCKED; - } - - if (!buffer_mapped(&bh)) { - if (vmf->flags & FAULT_FLAG_WRITE) { - error = get_block(inode, block, &bh, 1); - count_vm_event(PGMAJFAULT); - mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT); - major = VM_FAULT_MAJOR; - if (!error && (bh.b_size < PAGE_SIZE)) - error = -EIO; - if (error) - goto unlock_entry; - } else { - return dax_load_hole(mapping, entry, vmf); - } - } - - /* Filesystem should not return unwritten buffers to us! */ - WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh)); - error = dax_insert_mapping(mapping, bh.b_bdev, to_sector(&bh, inode), - bh.b_size, &entry, vma, vmf); - unlock_entry: - put_locked_mapping_entry(mapping, vmf->pgoff, entry); - out: - if (error == -ENOMEM) - return VM_FAULT_OOM | major; - /* -EBUSY is fine, somebody else faulted on the same PTE */ - if ((error < 0) && (error != -EBUSY)) - return VM_FAULT_SIGBUS | major; - return VM_FAULT_NOPAGE | major; -} -EXPORT_SYMBOL_GPL(dax_fault); - -#if defined(CONFIG_TRANSPARENT_HUGEPAGE) -/* - * The 'colour' (ie low bits) within a PMD of a page offset. This comes up - * more often than one might expect in the below function. - */ -#define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1) - -static void __dax_dbg(struct buffer_head *bh, unsigned long address, - const char *reason, const char *fn) -{ - if (bh) { - char bname[BDEVNAME_SIZE]; - bdevname(bh->b_bdev, bname); - pr_debug("%s: %s addr: %lx dev %s state %lx start %lld " - "length %zd fallback: %s\n", fn, current->comm, - address, bname, bh->b_state, (u64)bh->b_blocknr, - bh->b_size, reason); - } else { - pr_debug("%s: %s addr: %lx fallback: %s\n", fn, - current->comm, address, reason); - } -} - -#define dax_pmd_dbg(bh, address, reason) __dax_dbg(bh, address, reason, "dax_pmd") - -/** - * dax_pmd_fault - handle a PMD fault on a DAX file - * @vma: The virtual memory area where the fault occurred - * @vmf: The description of the |