| /* |
| * 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/pmem.h> |
| #include <linux/sched.h> |
| #include <linux/uio.h> |
| #include <linux/vmstat.h> |
| #include <linux/pfn_t.h> |
| #include <linux/sizes.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 int __init init_dax_wait_table(void) |
| { |
| int i; |
| |
| for (i = 0; i < DAX_WAIT_TABLE_ENTRIES; i++) |
| init_waitqueue_head(wait_table + i); |
| return 0; |
| } |
| fs_initcall(init_dax_wait_table); |
| |
| static 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; |
| long rc = -EIO; |
| |
| dax->addr = ERR_PTR(-EIO); |
| if (blk_queue_enter(q, true) != 0) |
| return rc; |
| |
| rc = bdev_direct_access(bdev, dax); |
| if (rc < 0) { |
| dax->addr = ERR_PTR(rc); |
| blk_queue_exit(q); |
| return rc; |
| } |
| return rc; |
| } |
| |
| static void dax_unmap_atomic(struct block_device *bdev, |
| const struct blk_dax_ctl *dax) |
| { |
| if (IS_ERR(dax->addr)) |
| return; |
| blk_queue_exit(bdev->bd_queue); |
| } |
| |
| struct page *read_dax_sector(struct block_device *bdev, sector_t n) |
| { |
| 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; |
| } |
| |
| static bool buffer_written(struct buffer_head *bh) |
| { |
| return buffer_mapped(bh) && !buffer_unwritten(bh); |
| } |
| |
| /* |
| * 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) |
| { |
| return bh->b_state != 0; |
| } |
| |
| |
| static sector_t to_sector(const struct buffer_head *bh, |
| const struct inode *inode) |
| { |
| sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9); |
| |
| return sector; |
| } |
| |
| 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) |
| { |
| 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 blk_dax_ctl dax = { |
| .addr = ERR_PTR(-EIO), |
| }; |
| 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; |
| } |
| max = min(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; |
| } |
| |
| pos += len; |
| if (!IS_ERR(dax.addr)) |
| dax.addr += len; |
| } |
| |
| 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; |
| } |
| EXPORT_SYMBOL_GPL(dax_do_io); |
| |
| /* |
| * DAX radix tree locking |
| */ |
| struct exceptional_entry_key { |
| struct address_space *mapping; |
| unsigned long index; |
| }; |
| |
| struct wait_exceptional_entry_queue { |
| wait_queue_t wait; |
| struct exceptional_entry_key key; |
| }; |
| |
| static int wake_exceptional_entry_func(wait_queue_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->index != ewait->key.index) |
| return 0; |
| return autoremove_wake_function(wait, mode, sync, NULL); |
| } |
| |
| /* |
| * Check whether the given slot is locked. The function must be called with |
| * mapping->tree_lock held |
| */ |
| static inline int slot_locked(struct address_space *mapping, void **slot) |
| { |
| unsigned long entry = (unsigned long) |
| radix_tree_deref_slot_protected(slot, &mapping->tree_lock); |
| return entry & RADIX_DAX_ENTRY_LOCK; |
| } |
| |
| /* |
| * Mark the given slot is locked. The function must be called with |
| * mapping->tree_lock held |
| */ |
| static inline void *lock_slot(struct address_space *mapping, void **slot) |
| { |
| unsigned long entry = (unsigned long) |
| radix_tree_deref_slot_protected(slot, &mapping->tree_lock); |
| |
| entry |= RADIX_DAX_ENTRY_LOCK; |
| radix_tree_replace_slot(slot, (void *)entry); |
| return (void *)entry; |
| } |
| |
| /* |
| * Mark the given slot is unlocked. The function must be called with |
| * mapping->tree_lock held |
| */ |
| static inline void *unlock_slot(struct address_space *mapping, void **slot) |
| { |
| unsigned long entry = (unsigned long) |
| radix_tree_deref_slot_protected(slot, &mapping->tree_lock); |
| |
| entry &= ~(unsigned long)RADIX_DAX_ENTRY_LOCK; |
| radix_tree_replace_slot(slot, (void *)entry); |
| return (void *)entry; |
| } |
| |
| /* |
| * Lookup entry in radix tree, wait for it to become unlocked if it is |
| * exceptional entry and return it. The caller must call |
| * put_unlocked_mapping_entry() when he decided not to lock the entry or |
| * put_locked_mapping_entry() when he locked the entry and now wants to |
| * unlock it. |
| * |
| * The function must be called with mapping->tree_lock held. |
| */ |
| static void *get_unlocked_mapping_entry(struct address_space *mapping, |
| pgoff_t index, void ***slotp) |
| { |
| void *ret, **slot; |
| struct wait_exceptional_entry_queue ewait; |
| wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index); |
| |
| 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, |
| &slot); |
| if (!ret || !radix_tree_exceptional_entry(ret) || |
| !slot_locked(mapping, slot)) { |
| if (slotp) |
| *slotp = slot; |
| return ret; |
| } |
| prepare_to_wait_exclusive(wq, &ewait.wait, |
| TASK_UNINTERRUPTIBLE); |
| spin_unlock_irq(&mapping->tree_lock); |
| schedule(); |
| finish_wait(wq, &ewait.wait); |
| spin_lock_irq(&mapping->tree_lock); |
| } |
| } |
| |
| /* |
| * 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. |
| * |
| * 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) |
| { |
| void *ret, **slot; |
| |
| restart: |
| spin_lock_irq(&mapping->tree_lock); |
| ret = get_unlocked_mapping_entry(mapping, index, &slot); |
| /* No entry for given index? Make sure radix tree is big enough. */ |
| if (!ret) { |
| int err; |
| |
| spin_unlock_irq(&mapping->tree_lock); |
| err = radix_tree_preload( |
| mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM); |
| if (err) |
| 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); |
| radix_tree_preload_end(); |
| if (err) { |
| spin_unlock_irq(&mapping->tree_lock); |
| /* Someone already created the entry? */ |
| if (err == -EEXIST) |
| goto restart; |
| return ERR_PTR(err); |
| } |
| /* Good, we have inserted empty locked entry into the tree. */ |
| mapping->nrexceptional++; |
| spin_unlock_irq(&mapping->tree_lock); |
| return ret; |
| } |
| /* Normal page in radix tree? */ |
| if (!radix_tree_exceptional_entry(ret)) { |
| struct page *page = ret; |
| |
| get_page(page); |
| spin_unlock_irq(&mapping->tree_lock); |
| lock_page(page); |
| /* Page got truncated? Retry... */ |
| if (unlikely(page->mapping != mapping)) { |
| unlock_page(page); |
| put_page(page); |
| goto restart; |
| } |
| return page; |
| } |
| ret = lock_slot(mapping, slot); |
| spin_unlock_irq(&mapping->tree_lock); |
| return ret; |
| } |
| |
| void dax_wake_mapping_entry_waiter(struct address_space *mapping, |
| pgoff_t index, bool wake_all) |
| { |
| wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index); |
| |
| /* |
| * Checking for locked entry and prepare_to_wait_exclusive() happens |
| * under mapping->tree_lock, ditto for entry handling in our callers. |
| * So at this point all tasks that could have seen our entry locked |
| * must be in the waitqueue and the following check will see them. |
| */ |
| if (waitqueue_active(wq)) { |
| struct exceptional_entry_key key; |
| |
| key.mapping = mapping; |
| key.index = index; |
| __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); |
| } |
| |
| /* |
| * 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) |
| { |
| void *entry; |
| |
| spin_lock_irq(&mapping->tree_lock); |
| entry = get_unlocked_mapping_entry(mapping, index, NULL); |
| /* |
| * 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... |
| */ |
| if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry))) { |
| spin_unlock_irq(&mapping->tree_lock); |
| return 0; |
| } |
| radix_tree_delete(&mapping->page_tree, index); |
| mapping->nrexceptional--; |
| spin_unlock_irq(&mapping->tree_lock); |
| dax_wake_mapping_entry_waiter(mapping, index, true); |
| |
| return 1; |
| } |
| |
| /* |
| * 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. We allocate a page cache page instead. |
| * We'll kick it out of the page cache if it's ever written to, |
| * otherwise it will simply fall out of the page cache under memory |
| * pressure without ever having been dirtied. |
| */ |
| static int dax_load_hole(struct address_space *mapping, void *entry, |
| struct vm_fault *vmf) |
| { |
| struct page *page; |
| |
| /* Hole page already exists? Return it... */ |
| if (!radix_tree_exceptional_entry(entry)) { |
| vmf->page = entry; |
| return VM_FAULT_LOCKED; |
| } |
| |
| /* 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); |
| return VM_FAULT_OOM; |
| } |
| vmf->page = page; |
| return VM_FAULT_LOCKED; |
| } |
| |
| static int copy_user_bh(struct page *to, struct inode *inode, |
| struct buffer_head *bh, unsigned long vaddr) |
| { |
| struct blk_dax_ctl dax = { |
| .sector = to_sector(bh, inode), |
| .size = bh->b_size, |
| }; |
| struct block_device *bdev = bh->b_bdev; |
| void *vto; |
| |
| if (dax_map_atomic(bdev, &dax) < 0) |
| return PTR_ERR(dax.addr); |
| vto = kmap_atomic(to); |
| copy_user_page(vto, (void __force *)dax.addr, vaddr, to); |
| kunmap_atomic(vto); |
| dax_unmap_atomic(bdev, &dax); |
| return 0; |
| } |
| |
| #define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT)) |
| |
| static void *dax_insert_mapping_entry(struct address_space *mapping, |
| struct vm_fault *vmf, |
| void *entry, sector_t sector) |
| { |
| struct radix_tree_root *page_tree = &mapping->page_tree; |
| int error = 0; |
| bool hole_fill = false; |
| void *new_entry; |
| pgoff_t index = vmf->pgoff; |
| |
| if (vmf->flags & FAULT_FLAG_WRITE) |
| __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); |
| |
| /* Replacing hole page with block mapping? */ |
| if (!radix_tree_exceptional_entry(entry)) { |
| hole_fill = true; |
| /* |
| * Unmap the page now before we remove it from page cache below. |
| * The page is locked so it cannot be faulted in again. |
| */ |
| unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT, |
| PAGE_SIZE, 0); |
| error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM); |
| if (error) |
| return ERR_PTR(error); |
| } |
| |
| spin_lock_irq(&mapping->tree_lock); |
| new_entry = (void *)((unsigned long)RADIX_DAX_ENTRY(sector, false) | |
| RADIX_DAX_ENTRY_LOCK); |
| if (hole_fill) { |
| __delete_from_page_cache(entry, NULL); |
| /* Drop pagecache reference */ |
| put_page(entry); |
| error = radix_tree_insert(page_tree, index, new_entry); |
| if (error) { |
| new_entry = ERR_PTR(error); |
| goto unlock; |
| } |
| mapping->nrexceptional++; |
| } else { |
| void **slot; |
| void *ret; |
| |
| ret = __radix_tree_lookup(page_tree, index, NULL, &slot); |
| WARN_ON_ONCE(ret != entry); |
| radix_tree_replace_slot(slot, new_entry); |
| } |
| if (vmf->flags & FAULT_FLAG_WRITE) |
| radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY); |
| unlock: |
| spin_unlock_irq(&mapping->tree_lock); |
| if (hole_fill) { |
| radix_tree_preload_end(); |
| /* |
| * We don't need hole page anymore, it has been replaced with |
| * locked radix tree entry now. |
| */ |
| if (mapping->a_ops->freepage) |
| mapping->a_ops->freepage(entry); |
| unlock_page(entry); |
| put_page(entry); |
| } |
| return new_entry; |
| } |
| |
| 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; |
| 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. |
| */ |
| 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_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) { |
| ret = -EIO; |
| goto unlock; |
| } |
| |
| dax.sector = RADIX_DAX_SECTOR(entry); |
| dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE); |
| spin_unlock_irq(&mapping->tree_lock); |
| |
| /* |
| * 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) |
| return ret; |
| |
| if (WARN_ON_ONCE(ret < dax.size)) { |
| ret = -EIO; |
| goto unmap; |
| } |
| |
| wb_cache_pmem(dax.addr, dax.size); |
| |
| spin_lock_irq(&mapping->tree_lock); |
| radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE); |
| spin_unlock_irq(&mapping->tree_lock); |
| unmap: |
| dax_unmap_atomic(bdev, &dax); |
| return ret; |
| |
| unlock: |
| spin_unlock_irq(&mapping->tree_lock); |
| return ret; |
| } |
| |
| /* |
| * Flush the mapping to the persistent domain within the byte range of [start, |
| * end]. This is required by data integrity operations to ensure file data is |
| * on persistent storage prior to completion of the operation. |
| */ |
| int dax_writeback_mapping_range(struct address_space *mapping, |
| struct block_device *bdev, struct writeback_control *wbc) |
| { |
| struct inode *inode = mapping->host; |
| pgoff_t start_index, end_index, pmd_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; |
| |
| if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL) |
| return 0; |
| |
| 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); |
| |
| pagevec_init(&pvec, 0); |
| while (!done) { |
| pvec.nr = find_get_entries_tag(mapping, start_index, |
| PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE, |
| pvec.pages, indices); |
| |
| if (pvec.nr == 0) |
| break; |
| |
| for (i = 0; i < pvec.nr; i++) { |
| if (indices[i] > end_index) { |
| done = true; |
| break; |
| } |
| |
| ret = dax_writeback_one(bdev, mapping, indices[i], |
| pvec.pages[i]); |
| if (ret < 0) |
| return ret; |
| } |
| } |
| return 0; |
| } |
| EXPORT_SYMBOL_GPL(dax_writeback_mapping_range); |
| |
| static int dax_insert_mapping(struct address_space *mapping, |
| struct buffer_head *bh, void **entryp, |
| struct vm_area_struct *vma, struct vm_fault *vmf) |
| { |
| unsigned long vaddr = (unsigned long)vmf->virtual_address; |
| struct block_device *bdev = bh->b_bdev; |
| struct blk_dax_ctl dax = { |
| .sector = to_sector(bh, mapping->host), |
| .size = bh->b_size, |
| }; |
| void *ret; |
| void *entry = *entryp; |
| |
| if (dax_map_atomic(bdev, &dax) < 0) |
| return PTR_ERR(dax.addr); |
| dax_unmap_atomic(bdev, &dax); |
| |
| ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector); |
| if (IS_ERR(ret)) |
| return PTR_ERR(ret); |
| *entryp = ret; |
| |
| return vm_insert_mixed(vma, vaddr, dax.pfn); |
| } |
| |
| /** |
| * __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_bh(new_page, inode, &bh, 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, &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(__dax_fault); |
| |
| /** |
| * 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. |
| */ |
| int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, |
| get_block_t get_block) |
| { |
| int result; |
| struct super_block *sb = file_inode(vma->vm_file)->i_sb; |
| |
| if (vmf->flags & FAULT_FLAG_WRITE) { |
| sb_start_pagefault(sb); |
| file_update_time(vma->vm_file); |
| } |
| result = __dax_fault(vma, vmf, get_block); |
| if (vmf->flags & FAULT_FLAG_WRITE) |
| sb_end_pagefault(sb); |
| |
| return result; |
| } |
| 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") |
| |
| int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, |
| pmd_t *pmd, unsigned int flags, get_block_t get_block) |
| { |
| struct file *file = vma->vm_file; |
| struct address_space *mapping = file->f_mapping; |
| struct inode *inode = mapping->host; |
| struct buffer_head bh; |
| unsigned blkbits = inode->i_blkbits; |
| unsigned long pmd_addr = address & PMD_MASK; |
| bool write = flags & FAULT_FLAG_WRITE; |
| struct block_device *bdev; |
| pgoff_t size, pgoff; |
| sector_t block; |
| int result = 0; |
| bool alloc = false; |
| |
| /* dax pmd mappings require pfn_t_devmap() */ |
| if (!IS_ENABLED(CONFIG_FS_DAX_PMD)) |
| return VM_FAULT_FALLBACK; |
| |
| /* Fall back to PTEs if we're going to COW */ |
| if (write && !(vma->vm_flags & VM_SHARED)) { |
| split_huge_pmd(vma, pmd, address); |
| dax_pmd_dbg(NULL, address, "cow write"); |
| return VM_FAULT_FALLBACK; |
| } |
| /* If the PMD would extend outside the VMA */ |
| if (pmd_addr < vma->vm_start) { |
| dax_pmd_dbg(NULL, address, "vma start unaligned"); |
| return VM_FAULT_FALLBACK; |
| } |
| if ((pmd_addr + PMD_SIZE) > vma->vm_end) { |
| dax_pmd_dbg(NULL, address, "vma end unaligned"); |
| return VM_FAULT_FALLBACK; |
| } |
| |
| pgoff = linear_page_index(vma, pmd_addr); |
| size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; |
| if (pgoff >= size) |
| return VM_FAULT_SIGBUS; |
| /* If the PMD would cover blocks out of the file */ |
| if ((pgoff | PG_PMD_COLOUR) >= size) { |
| dax_pmd_dbg(NULL, address, |
| "offset + huge page size > file size"); |
| return VM_FAULT_FALLBACK; |
| } |
| |
| memset(&bh, 0, sizeof(bh)); |
| bh.b_bdev = inode->i_sb->s_bdev; |
| block = (sector_t)pgoff << (PAGE_SHIFT - blkbits); |
| |
| bh.b_size = PMD_SIZE; |
| |
| if (get_block(inode, block, &bh, 0) != 0) |
| return VM_FAULT_SIGBUS; |
| |
| if (!buffer_mapped(&bh) && write) { |
| if (get_block(inode, block, &bh, 1) != 0) |
| return VM_FAULT_SIGBUS; |
| alloc = true; |
| WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh)); |
| } |
| |
| bdev = bh.b_bdev; |
| |
| /* |
| * If the filesystem isn't willing to tell us the length of a hole, |
| * just fall back to PTEs. Calling get_block 512 times in a loop |
| * would be silly. |
| */ |
| if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) { |
| dax_pmd_dbg(&bh, address, "allocated block too small"); |
| return VM_FAULT_FALLBACK; |
| } |
| |
| /* |
| * If we allocated new storage, make sure no process has any |
| * zero pages covering this hole |
| */ |
| if (alloc) { |
| loff_t lstart = pgoff << PAGE_SHIFT; |
| loff_t lend = lstart + PMD_SIZE - 1; /* inclusive */ |
| |
| truncate_pagecache_range(inode, lstart, lend); |
| } |
| |
| if (!write && !buffer_mapped(&bh)) { |
| spinlock_t *ptl; |
| pmd_t entry; |
| struct page *zero_page = get_huge_zero_page(); |
| |
| if (unlikely(!zero_page)) { |
| dax_pmd_dbg(&bh, address, "no zero page"); |
| goto fallback; |
| } |
| |
| ptl = pmd_lock(vma->vm_mm, pmd); |
| if (!pmd_none(*pmd)) { |
| spin_unlock(ptl); |
| dax_pmd_dbg(&bh, address, "pmd already present"); |
| goto fallback; |
| } |
| |
| dev_dbg(part_to_dev(bdev->bd_part), |
| "%s: %s addr: %lx pfn: <zero> sect: %llx\n", |
| __func__, current->comm, address, |
| (unsigned long long) to_sector(&bh, inode)); |
| |
| entry = mk_pmd(zero_page, vma->vm_page_prot); |
| entry = pmd_mkhuge(entry); |
| set_pmd_at(vma->vm_mm, pmd_addr, pmd, entry); |
| result = VM_FAULT_NOPAGE; |
| spin_unlock(ptl); |
| } else { |
| struct blk_dax_ctl dax = { |
| .sector = to_sector(&bh, inode), |
| .size = PMD_SIZE, |
| }; |
| long length = dax_map_atomic(bdev, &dax); |
| |
| if (length < 0) { |
| dax_pmd_dbg(&bh, address, "dax-error fallback"); |
| goto fallback; |
| } |
| if (length < PMD_SIZE) { |
| dax_pmd_dbg(&bh, address, "dax-length too small"); |
| dax_unmap_atomic(bdev, &dax); |
| goto fallback; |
| } |
| if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR) { |
| dax_pmd_dbg(&bh, address, "pfn unaligned"); |
| dax_unmap_atomic(bdev, &dax); |
| goto fallback; |
| } |
| |
| if (!pfn_t_devmap(dax.pfn)) { |
| dax_unmap_atomic(bdev, &dax); |
| dax_pmd_dbg(&bh, address, "pfn not in memmap"); |
| goto fallback; |
| } |
| dax_unmap_atomic(bdev, &dax); |
| |
| /* |
| * For PTE faults we insert a radix tree entry for reads, and |
| * leave it clean. Then on the first write we dirty the radix |
| * tree entry via the dax_pfn_mkwrite() path. This sequence |
| * allows the dax_pfn_mkwrite() call to be simpler and avoid a |
| * call into get_block() to translate the pgoff to a sector in |
| * order to be able to create a new radix tree entry. |
| * |
| * The PMD path doesn't have an equivalent to |
| * dax_pfn_mkwrite(), though, so for a read followed by a |
| * write we traverse all the way through __dax_pmd_fault() |
| * twice. This means we can just skip inserting a radix tree |
| * entry completely on the initial read and just wait until |
| * the write to insert a dirty entry. |
| */ |
| if (write) { |
| /* |
| * We should insert radix-tree entry and dirty it here. |
| * For now this is broken... |
| */ |
| } |
| |
| dev_dbg(part_to_dev(bdev->bd_part), |
| "%s: %s addr: %lx pfn: %lx sect: %llx\n", |
| __func__, current->comm, address, |
| pfn_t_to_pfn(dax.pfn), |
| (unsigned long long) dax.sector); |
| result |= vmf_insert_pfn_pmd(vma, address, pmd, |
| dax.pfn, write); |
| } |
| |
| out: |
| return result; |
| |
| fallback: |
| count_vm_event(THP_FAULT_FALLBACK); |
| result = VM_FAULT_FALLBACK; |
| goto out; |
| } |
| EXPORT_SYMBOL_GPL(__dax_pmd_fault); |
| |
| /** |
| * 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 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 |
| * pmd_fault handler for DAX files. |
| */ |
| int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, |
| pmd_t *pmd, unsigned int flags, get_block_t get_block) |
| { |
| int result; |
| struct super_block *sb = file_inode(vma->vm_file)->i_sb; |
| |
| if (flags & FAULT_FLAG_WRITE) { |
| sb_start_pagefault(sb); |
| file_update_time(vma->vm_file); |
| } |
| result = __dax_pmd_fault(vma, address, pmd, flags, get_block); |
| if (flags & FAULT_FLAG_WRITE) |
| sb_end_pagefault(sb); |
| |
| return result; |
| } |
| EXPORT_SYMBOL_GPL(dax_pmd_fault); |
| #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ |
| |
| /** |
| * dax_pfn_mkwrite - handle first write to DAX page |
| * @vma: The virtual memory area where the fault occurred |
| * @vmf: The description of the fault |
| */ |
| int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) |
| { |
| struct file *file = vma->vm_file; |
| struct address_space *mapping = file->f_mapping; |
| void *entry; |
| pgoff_t index = vmf->pgoff; |
| |
| spin_lock_irq(&mapping->tree_lock); |
| entry = get_unlocked_mapping_entry(mapping, index, NULL); |
| if (!entry || !radix_tree_exceptional_entry(entry)) |
| goto out; |
| radix_tree_tag_set(&mapping->page_tree, index, PAGECACHE_TAG_DIRTY); |
| put_unlocked_mapping_entry(mapping, index, entry); |
| out: |
| spin_unlock_irq(&mapping->tree_lock); |
| return VM_FAULT_NOPAGE; |
| } |
| EXPORT_SYMBOL_GPL(dax_pfn_mkwrite); |
| |
| 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, sector_t sector, |
| unsigned int offset, unsigned int length) |
| { |
| struct blk_dax_ctl dax = { |
| .sector = sector, |
| .size = PAGE_SIZE, |
| }; |
| |
| if (dax_range_is_aligned(bdev, offset, length)) { |
| sector_t start_sector = dax.sector + (offset >> 9); |
| |
| return blkdev_issue_zeroout(bdev, start_sector, |
| length >> 9, GFP_NOFS, true); |
| } else { |
| if (dax_map_atomic(bdev, &dax) < 0) |
| return PTR_ERR(dax.addr); |
| clear_pmem(dax.addr + offset, length); |
| dax_unmap_atomic(bdev, &dax); |
| } |
| return 0; |
| } |
| EXPORT_SYMBOL_GPL(__dax_zero_page_range); |
| |
| /** |
| * dax_zero_page_range - zero a range within a page of a DAX file |
| * @inode: The file being truncated |
| * @from: The file offset that is being truncated to |
| * @length: The number of bytes to zero |
| * @get_block: The filesystem method used to translate file offsets to blocks |
| * |
| * This function can be called by a filesystem when it is zeroing part of a |
| * page in a DAX file. This is intended for hole-punch operations. If |
| * you are truncating a file, the helper function dax_truncate_page() may be |
| * more convenient. |
| */ |
| int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length, |
| get_block_t get_block) |
| { |
| struct buffer_head bh; |
| pgoff_t index = from >> PAGE_SHIFT; |
| unsigned offset = from & (PAGE_SIZE-1); |
| int err; |
| |
| /* Block boundary? Nothing to do */ |
| if (!length) |
| return 0; |
| BUG_ON((offset + length) > PAGE_SIZE); |
| |
| memset(&bh, 0, sizeof(bh)); |
| bh.b_bdev = inode->i_sb->s_bdev; |
| bh.b_size = PAGE_SIZE; |
| err = get_block(inode, index, &bh, 0); |
| if (err < 0 || !buffer_written(&bh)) |
| return err; |
| |
| return __dax_zero_page_range(bh.b_bdev, to_sector(&bh, inode), |
| offset, length); |
| } |
| EXPORT_SYMBOL_GPL(dax_zero_page_range); |
| |
| /** |
| * dax_truncate_page - handle a partial page being truncated in a DAX file |
| * @inode: The file being truncated |
| * @from: The file offset that is being truncated to |
| * @get_block: The filesystem method used to translate file offsets to blocks |
| * |
| * Similar to block_truncate_page(), this function can be called by a |
| * filesystem when it is truncating a DAX file to handle the partial page. |
| */ |
| int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block) |
| { |
| unsigned length = PAGE_ALIGN(from) - from; |
| return dax_zero_page_range(inode, from, length, get_block); |
| } |
| EXPORT_SYMBOL_GPL(dax_truncate_page); |