Linux-libre 4.7.1-gnupck-4.7.1-gnu

1 files changed, 493 insertions, 360 deletions

diff --git a/fs/dax.c b/fs/dax.c
index 75ba46d82..e207f8f9b 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -32,6 +32,44 @@
 #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;
@@ -78,50 +116,6 @@ struct page *read_dax_sector(struct block_device *bdev, sector_t n)
 	return page;
 }
 
-/*
- * dax_clear_sectors() is called from within transaction context from XFS,
- * and hence this means the stack from this point must follow GFP_NOFS
- * semantics for all operations.
- */
-int dax_clear_sectors(struct block_device *bdev, sector_t _sector, long _size)
-{
-	struct blk_dax_ctl dax = {
-		.sector = _sector,
-		.size = _size,
-	};
-
-	might_sleep();
-	do {
-		long count, sz;
-
-		count = dax_map_atomic(bdev, &dax);
-		if (count < 0)
-			return count;
-		sz = min_t(long, count, SZ_128K);
-		clear_pmem(dax.addr, sz);
-		dax.size -= sz;
-		dax.sector += sz / 512;
-		dax_unmap_atomic(bdev, &dax);
-		cond_resched();
-	} while (dax.size);
-
-	wmb_pmem();
-	return 0;
-}
-EXPORT_SYMBOL_GPL(dax_clear_sectors);
-
-/* the clear_pmem() calls are ordered by a wmb_pmem() in the caller */
-static void dax_new_buf(void __pmem *addr, unsigned size, unsigned first,
-		loff_t pos, loff_t end)
-{
-	loff_t final = end - pos + first; /* The final byte of the buffer */
-
-	if (first > 0)
-		clear_pmem(addr, first);
-	if (final < size)
-		clear_pmem(addr + final, size - final);
-}
-
 static bool buffer_written(struct buffer_head *bh)
 {
 	return buffer_mapped(bh) && !buffer_unwritten(bh);
@@ -160,6 +154,9 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
 	struct blk_dax_ctl dax = {
 		.addr = (void __pmem *) 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));
@@ -167,7 +164,6 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
 	while (pos < end) {
 		size_t len;
 		if (pos == max) {
-			unsigned blkbits = inode->i_blkbits;
 			long page = pos >> PAGE_SHIFT;
 			sector_t block = page << (PAGE_SHIFT - blkbits);
 			unsigned first = pos - (block << blkbits);
@@ -183,6 +179,13 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
 					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));
@@ -202,15 +205,15 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
 					rc = map_len;
 					break;
 				}
-				if (buffer_unwritten(bh) || buffer_new(bh)) {
-					dax_new_buf(dax.addr, map_len, first,
-							pos, end);
-					need_wmb = true;
-				}
 				dax.addr += first;
 				size = map_len - first;
 			}
-			max = min(pos + size, end);
+			/*
+			 * 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) {
@@ -244,7 +247,6 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
  * @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
- * @pos: The file offset where the I/O starts
  * @get_block: The filesystem method used to translate file offsets to blocks
  * @end_io: A filesystem callback for I/O completion
  * @flags: See below
@@ -257,25 +259,19 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
  * is in progress.
  */
 ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode,
-		  struct iov_iter *iter, loff_t pos, get_block_t get_block,
+		  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) {
-		struct address_space *mapping = inode->i_mapping;
+	if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ)
 		inode_lock(inode);
-		retval = filemap_write_and_wait_range(mapping, pos, end - 1);
-		if (retval) {
-			inode_unlock(inode);
-			goto out;
-		}
-	}
 
 	/* Protects against truncate */
 	if (!(flags & DIO_SKIP_DIO_COUNT))
@@ -296,12 +292,268 @@ ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode,
 
 	if (!(flags & DIO_SKIP_DIO_COUNT))
 		inode_dio_end(inode);
- out:
 	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.
@@ -309,24 +561,24 @@ EXPORT_SYMBOL_GPL(dax_do_io);
  * 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, struct page *page,
-							struct vm_fault *vmf)
+static int dax_load_hole(struct address_space *mapping, void *entry,
+			 struct vm_fault *vmf)
 {
-	unsigned long size;
-	struct inode *inode = mapping->host;
-	if (!page)
-		page = find_or_create_page(mapping, vmf->pgoff,
-						GFP_KERNEL | __GFP_ZERO);
-	if (!page)
-		return VM_FAULT_OOM;
-	/* Recheck i_size under page lock to avoid truncate race */
-	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
-	if (vmf->pgoff >= size) {
-		unlock_page(page);
-		put_page(page);
-		return VM_FAULT_SIGBUS;
+	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;
 }
@@ -350,77 +602,72 @@ static int copy_user_bh(struct page *to, struct inode *inode,
 	return 0;
 }
 
-#define NO_SECTOR -1
 #define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT))
 
-static int dax_radix_entry(struct address_space *mapping, pgoff_t index,
-		sector_t sector, bool pmd_entry, bool dirty)
+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;
-	pgoff_t pmd_index = DAX_PMD_INDEX(index);
-	int type, error = 0;
-	void *entry;
+	int error = 0;
+	bool hole_fill = false;
+	void *new_entry;
+	pgoff_t index = vmf->pgoff;
 
-	WARN_ON_ONCE(pmd_entry && !dirty);
-	if (dirty)
+	if (vmf->flags & FAULT_FLAG_WRITE)
 		__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
 
-	spin_lock_irq(&mapping->tree_lock);
-
-	entry = radix_tree_lookup(page_tree, pmd_index);
-	if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD) {
-		index = pmd_index;
-		goto dirty;
+	/* 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);
 	}
 
-	entry = radix_tree_lookup(page_tree, index);
-	if (entry) {
-		type = RADIX_DAX_TYPE(entry);
-		if (WARN_ON_ONCE(type != RADIX_DAX_PTE &&
-					type != RADIX_DAX_PMD)) {
-			error = -EIO;
+	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;
 
-		if (!pmd_entry || type == RADIX_DAX_PMD)
-			goto dirty;
-
-		/*
-		 * We only insert dirty PMD entries into the radix tree.  This
-		 * means we don't need to worry about removing a dirty PTE
-		 * entry and inserting a clean PMD entry, thus reducing the
-		 * range we would flush with a follow-up fsync/msync call.
-		 */
-		radix_tree_delete(&mapping->page_tree, index);
-		mapping->nrexceptional--;
-	}
-
-	if (sector == NO_SECTOR) {
-		/*
-		 * This can happen during correct operation if our pfn_mkwrite
-		 * fault raced against a hole punch operation.  If this
-		 * happens the pte that was hole punched will have been
-		 * unmapped and the radix tree entry will have been removed by
-		 * the time we are called, but the call will still happen.  We
-		 * will return all the way up to wp_pfn_shared(), where the
-		 * pte_same() check will fail, eventually causing page fault
-		 * to be retried by the CPU.
-		 */
-		goto unlock;
+		ret = __radix_tree_lookup(page_tree, index, NULL, &slot);
+		WARN_ON_ONCE(ret != entry);
+		radix_tree_replace_slot(slot, new_entry);
 	}
-
-	error = radix_tree_insert(page_tree, index,
-			RADIX_DAX_ENTRY(sector, pmd_entry));
-	if (error)
-		goto unlock;
-
-	mapping->nrexceptional++;
- dirty:
-	if (dirty)
+	if (vmf->flags & FAULT_FLAG_WRITE)
 		radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);
  unlock:
 	spin_unlock_irq(&mapping->tree_lock);
-	return error;
+	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,
@@ -546,56 +793,29 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 }
 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
 
-static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
+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 address_space *mapping = inode->i_mapping;
 	struct block_device *bdev = bh->b_bdev;
 	struct blk_dax_ctl dax = {
-		.sector = to_sector(bh, inode),
+		.sector = to_sector(bh, mapping->host),
 		.size = bh->b_size,
 	};
-	pgoff_t size;
-	int error;
-
-	i_mmap_lock_read(mapping);
-
-	/*
-	 * Check truncate didn't happen while we were allocating a block.
-	 * If it did, this block may or may not be still allocated to the
-	 * file.  We can't tell the filesystem to free it because we can't
-	 * take i_mutex here.  In the worst case, the file still has blocks
-	 * allocated past the end of the file.
-	 */
-	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
-	if (unlikely(vmf->pgoff >= size)) {
-		error = -EIO;
-		goto out;
-	}
+	void *ret;
+	void *entry = *entryp;
 
-	if (dax_map_atomic(bdev, &dax) < 0) {
-		error = PTR_ERR(dax.addr);
-		goto out;
-	}
-
-	if (buffer_unwritten(bh) || buffer_new(bh)) {
-		clear_pmem(dax.addr, PAGE_SIZE);
-		wmb_pmem();
-	}
+	if (dax_map_atomic(bdev, &dax) < 0)
+		return PTR_ERR(dax.addr);
 	dax_unmap_atomic(bdev, &dax);
 
-	error = dax_radix_entry(mapping, vmf->pgoff, dax.sector, false,
-			vmf->flags & FAULT_FLAG_WRITE);
-	if (error)
-		goto out;
-
-	error = vm_insert_mixed(vma, vaddr, dax.pfn);
+	ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector);
+	if (IS_ERR(ret))
+		return PTR_ERR(ret);
+	*entryp = ret;
 
- out:
-	i_mmap_unlock_read(mapping);
-
-	return error;
+	return vm_insert_mixed(vma, vaddr, dax.pfn);
 }
 
 /**
@@ -603,24 +823,18 @@ static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
  * @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
- * @complete_unwritten: The filesystem method used to convert unwritten blocks
- *	to written so the data written to them is exposed. This is required for
- *	required by write faults for filesystems that will return unwritten
- *	extent mappings from @get_block, but it is optional for reads as
- *	dax_insert_mapping() will always zero unwritten blocks. If the fs does
- *	not support unwritten extents, the it should pass NULL.
  *
  * 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, dax_iodone_t complete_unwritten)
+			get_block_t get_block)
 {
 	struct file *file = vma->vm_file;
 	struct address_space *mapping = file->f_mapping;
 	struct inode *inode = mapping->host;
-	struct page *page;
+	void *entry;
 	struct buffer_head bh;
 	unsigned long vaddr = (unsigned long)vmf->virtual_address;
 	unsigned blkbits = inode->i_blkbits;
@@ -629,6 +843,11 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	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;
@@ -638,49 +857,17 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	bh.b_bdev = inode->i_sb->s_bdev;
 	bh.b_size = PAGE_SIZE;
 
- repeat:
-	page = find_get_page(mapping, vmf->pgoff);
-	if (page) {
-		if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
-			put_page(page);
-			return VM_FAULT_RETRY;
-		}
-		if (unlikely(page->mapping != mapping)) {
-			unlock_page(page);
-			put_page(page);
-			goto repeat;
-		}
-		size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
-		if (unlikely(vmf->pgoff >= size)) {
-			/*
-			 * We have a struct page covering a hole in the file
-			 * from a read fault and we've raced with a truncate
-			 */
-			error = -EIO;
-			goto unlock_page;
-		}
+	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_page;
-
-	if (!buffer_mapped(&bh) && !buffer_unwritten(&bh) && !vmf->cow_page) {
-		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_page;
-		} else {
-			return dax_load_hole(mapping, page, vmf);
-		}
-	}
+		goto unlock_entry;
 
 	if (vmf->cow_page) {
 		struct page *new_page = vmf->cow_page;
@@ -689,53 +876,35 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		else
 			clear_user_highpage(new_page, vaddr);
 		if (error)
-			goto unlock_page;
-		vmf->page = page;
-		if (!page) {
-			i_mmap_lock_read(mapping);
-			/* Check we didn't race with truncate */
-			size = (i_size_read(inode) + PAGE_SIZE - 1) >>
-								PAGE_SHIFT;
-			if (vmf->pgoff >= size) {
-				i_mmap_unlock_read(mapping);
-				error = -EIO;
-				goto out;
-			}
+			goto unlock_entry;
+		if (!radix_tree_exceptional_entry(entry)) {
+			vmf->page = entry;
+			return VM_FAULT_LOCKED;
 		}
-		return VM_FAULT_LOCKED;
+		vmf->entry = entry;
+		return VM_FAULT_DAX_LOCKED;
 	}
 
-	/* Check we didn't race with a read fault installing a new page */
-	if (!page && major)
-		page = find_lock_page(mapping, vmf->pgoff);
-
-	if (page) {
-		unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
-							PAGE_SIZE, 0);
-		delete_from_page_cache(page);
-		unlock_page(page);
-		put_page(page);
-		page = NULL;
-	}
-
-	/*
-	 * If we successfully insert the new mapping over an unwritten extent,
-	 * we need to ensure we convert the unwritten extent. If there is an
-	 * error inserting the mapping, the filesystem needs to leave it as
-	 * unwritten to prevent exposure of the stale underlying data to
-	 * userspace, but we still need to call the completion function so
-	 * the private resources on the mapping buffer can be released. We
-	 * indicate what the callback should do via the uptodate variable, same
-	 * as for normal BH based IO completions.
-	 */
-	error = dax_insert_mapping(inode, &bh, vma, vmf);
-	if (buffer_unwritten(&bh)) {
-		if (complete_unwritten)
-			complete_unwritten(&bh, !error);
-		else
-			WARN_ON_ONCE(!(vmf->flags & FAULT_FLAG_WRITE));
+	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;
@@ -743,13 +912,6 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	if ((error < 0) && (error != -EBUSY))
 		return VM_FAULT_SIGBUS | major;
 	return VM_FAULT_NOPAGE | major;
-
- unlock_page:
-	if (page) {
-		unlock_page(page);
-		put_page(page);
-	}
-	goto out;
 }
 EXPORT_SYMBOL(__dax_fault);
 
@@ -763,7 +925,7 @@ EXPORT_SYMBOL(__dax_fault);
  * fault handler for DAX files.
  */
 int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
-	      get_block_t get_block, dax_iodone_t complete_unwritten)
+	      get_block_t get_block)
 {
 	int result;
 	struct super_block *sb = file_inode(vma->vm_file)->i_sb;
@@ -772,7 +934,7 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		sb_start_pagefault(sb);
 		file_update_time(vma->vm_file);
 	}
-	result = __dax_fault(vma, vmf, get_block, complete_unwritten);
+	result = __dax_fault(vma, vmf, get_block);
 	if (vmf->flags & FAULT_FLAG_WRITE)
 		sb_end_pagefault(sb);
 
@@ -780,7 +942,7 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 }
 EXPORT_SYMBOL_GPL(dax_fault);
 
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+#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.
@@ -806,8 +968,7 @@ static void __dax_dbg(struct buffer_head *bh, unsigned long address,
 #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,
-		dax_iodone_t complete_unwritten)
+		pmd_t *pmd, unsigned int flags, get_block_t get_block)
 {
 	struct file *file = vma->vm_file;
 	struct address_space *mapping = file->f_mapping;
@@ -819,7 +980,7 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 	struct block_device *bdev;
 	pgoff_t size, pgoff;
 	sector_t block;
-	int error, result = 0;
+	int result = 0;
 	bool alloc = false;
 
 	/* dax pmd mappings require pfn_t_devmap() */
@@ -866,6 +1027,7 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 		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;
@@ -891,26 +1053,7 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 		truncate_pagecache_range(inode, lstart, lend);
 	}
 
-	i_mmap_lock_read(mapping);
-
-	/*
-	 * If a truncate happened while we were allocating blocks, we may
-	 * leave blocks allocated to the file that are beyond EOF.  We can't
-	 * take i_mutex here, so just leave them hanging; they'll be freed
-	 * when the file is deleted.
-	 */
-	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
-	if (pgoff >= size) {
-		result = VM_FAULT_SIGBUS;
-		goto out;
-	}
-	if ((pgoff | PG_PMD_COLOUR) >= size) {
-		dax_pmd_dbg(&bh, address,
-				"offset + huge page size > file size");
-		goto fallback;
-	}
-
-	if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {
+	if (!write && !buffer_mapped(&bh)) {
 		spinlock_t *ptl;
 		pmd_t entry;
 		struct page *zero_page = get_huge_zero_page();
@@ -945,8 +1088,8 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 		long length = dax_map_atomic(bdev, &dax);
 
 		if (length < 0) {
-			result = VM_FAULT_SIGBUS;
-			goto out;
+			dax_pmd_dbg(&bh, address, "dax-error fallback");
+			goto fallback;
 		}
 		if (length < PMD_SIZE) {
 			dax_pmd_dbg(&bh, address, "dax-length too small");
@@ -964,14 +1107,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 			dax_pmd_dbg(&bh, address, "pfn not in memmap");
 			goto fallback;
 		}
-
-		if (buffer_unwritten(&bh) || buffer_new(&bh)) {
-			clear_pmem(dax.addr, PMD_SIZE);
-			wmb_pmem();
-			count_vm_event(PGMAJFAULT);
-			mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
-			result |= VM_FAULT_MAJOR;
-		}
 		dax_unmap_atomic(bdev, &dax);
 
 		/*
@@ -990,13 +1125,10 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 		 * the write to insert a dirty entry.
 		 */
 		if (write) {
-			error = dax_radix_entry(mapping, pgoff, dax.sector,
-					true, true);
-			if (error) {
-				dax_pmd_dbg(&bh, address,
-						"PMD radix insertion failed");
-				goto fallback;
-			}
+			/*
+			 * We should insert radix-tree entry and dirty it here.
+			 * For now this is broken...
+			 */
 		}
 
 		dev_dbg(part_to_dev(bdev->bd_part),
@@ -1009,11 +1141,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 	}
 
  out:
-	i_mmap_unlock_read(mapping);
-
-	if (buffer_unwritten(&bh))
-		complete_unwritten(&bh, !(result & VM_FAULT_ERROR));
-
 	return result;
 
  fallback:
@@ -1033,8 +1160,7 @@ EXPORT_SYMBOL_GPL(__dax_pmd_fault);
  * 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,
-			dax_iodone_t complete_unwritten)
+			pmd_t *pmd, unsigned int flags, get_block_t get_block)
 {
 	int result;
 	struct super_block *sb = file_inode(vma->vm_file)->i_sb;
@@ -1043,8 +1169,7 @@ int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 		sb_start_pagefault(sb);
 		file_update_time(vma->vm_file);
 	}
-	result = __dax_pmd_fault(vma, address, pmd, flags, get_block,
-				complete_unwritten);
+	result = __dax_pmd_fault(vma, address, pmd, flags, get_block);
 	if (flags & FAULT_FLAG_WRITE)
 		sb_end_pagefault(sb);
 
@@ -1061,27 +1186,59 @@ EXPORT_SYMBOL_GPL(dax_pmd_fault);
 int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
 	struct file *file = vma->vm_file;
-	int error;
-
-	/*
-	 * We pass NO_SECTOR to dax_radix_entry() because we expect that a
-	 * RADIX_DAX_PTE entry already exists in the radix tree from a
-	 * previous call to __dax_fault().  We just want to look up that PTE
-	 * entry using vmf->pgoff and make sure the dirty tag is set.  This
-	 * saves us from having to make a call to get_block() here to look
-	 * up the sector.
-	 */
-	error = dax_radix_entry(file->f_mapping, vmf->pgoff, NO_SECTOR, false,
-			true);
+	struct address_space *mapping = file->f_mapping;
+	void *entry;
+	pgoff_t index = vmf->pgoff;
 
-	if (error == -ENOMEM)
-		return VM_FAULT_OOM;
-	if (error)
-		return VM_FAULT_SIGBUS;
+	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);
+		wmb_pmem();
+		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
@@ -1093,12 +1250,6 @@ EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
  * 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.
- *
- * We work in terms of PAGE_SIZE here for commonality with
- * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
- * took care of disposing of the unnecessary blocks.  Even if the filesystem
- * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
- * since the file might be mmapped.
  */
 int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
 							get_block_t get_block)
@@ -1117,23 +1268,11 @@ int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
 	bh.b_bdev = inode->i_sb->s_bdev;
 	bh.b_size = PAGE_SIZE;
 	err = get_block(inode, index, &bh, 0);
-	if (err < 0)
+	if (err < 0 || !buffer_written(&bh))
 		return err;
-	if (buffer_written(&bh)) {
-		struct block_device *bdev = bh.b_bdev;
-		struct blk_dax_ctl dax = {
-			.sector = to_sector(&bh, inode),
-			.size = PAGE_SIZE,
-		};
 
-		if (dax_map_atomic(bdev, &dax) < 0)
-			return PTR_ERR(dax.addr);
-		clear_pmem(dax.addr + offset, length);
-		wmb_pmem();
-		dax_unmap_atomic(bdev, &dax);
-	}
-
-	return 0;
+	return __dax_zero_page_range(bh.b_bdev, to_sector(&bh, inode),
+			offset, length);
 }
 EXPORT_SYMBOL_GPL(dax_zero_page_range);
 
@@ -1145,12 +1284,6 @@ EXPORT_SYMBOL_GPL(dax_zero_page_range);
  *
  * 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.
- *
- * We work in terms of PAGE_SIZE here for commonality with
- * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
- * took care of disposing of the unnecessary blocks.  Even if the filesystem
- * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
- * since the file might be mmapped.
  */
 int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
 {