1 files changed, 594 insertions, 0 deletions
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
new file mode 100644
index 000000000..da4438f31
--- /dev/null
+++ b/drivers/dax/super.c
@@ -0,0 +1,594 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright(c) 2017 Intel Corporation. All rights reserved.
+ */
+#include <linux/pagemap.h>
+#include <linux/module.h>
+#include <linux/mount.h>
+#include <linux/pseudo_fs.h>
+#include <linux/magic.h>
+#include <linux/pfn_t.h>
+#include <linux/cdev.h>
+#include <linux/slab.h>
+#include <linux/uio.h>
+#include <linux/dax.h>
+#include <linux/fs.h>
+#include "dax-private.h"
+
+/**
+ * struct dax_device - anchor object for dax services
+ * @inode: core vfs
+ * @cdev: optional character interface for "device dax"
+ * @private: dax driver private data
+ * @flags: state and boolean properties
+ * @ops: operations for this device
+ * @holder_data: holder of a dax_device: could be filesystem or mapped device
+ * @holder_ops: operations for the inner holder
+ */
+struct dax_device {
+	struct inode inode;
+	struct cdev cdev;
+	void *private;
+	unsigned long flags;
+	const struct dax_operations *ops;
+	void *holder_data;
+	const struct dax_holder_operations *holder_ops;
+};
+
+static dev_t dax_devt;
+DEFINE_STATIC_SRCU(dax_srcu);
+static struct vfsmount *dax_mnt;
+static DEFINE_IDA(dax_minor_ida);
+static struct kmem_cache *dax_cache __read_mostly;
+static struct super_block *dax_superblock __read_mostly;
+
+int dax_read_lock(void)
+{
+	return srcu_read_lock(&dax_srcu);
+}
+EXPORT_SYMBOL_GPL(dax_read_lock);
+
+void dax_read_unlock(int id)
+{
+	srcu_read_unlock(&dax_srcu, id);
+}
+EXPORT_SYMBOL_GPL(dax_read_unlock);
+
+#if defined(CONFIG_BLOCK) && defined(CONFIG_FS_DAX)
+#include <linux/blkdev.h>
+
+static DEFINE_XARRAY(dax_hosts);
+
+int dax_add_host(struct dax_device *dax_dev, struct gendisk *disk)
+{
+	return xa_insert(&dax_hosts, (unsigned long)disk, dax_dev, GFP_KERNEL);
+}
+EXPORT_SYMBOL_GPL(dax_add_host);
+
+void dax_remove_host(struct gendisk *disk)
+{
+	xa_erase(&dax_hosts, (unsigned long)disk);
+}
+EXPORT_SYMBOL_GPL(dax_remove_host);
+
+/**
+ * fs_dax_get_by_bdev() - temporary lookup mechanism for filesystem-dax
+ * @bdev: block device to find a dax_device for
+ * @start_off: returns the byte offset into the dax_device that @bdev starts
+ * @holder: filesystem or mapped device inside the dax_device
+ * @ops: operations for the inner holder
+ */
+struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev, u64 *start_off,
+		void *holder, const struct dax_holder_operations *ops)
+{
+	struct dax_device *dax_dev;
+	u64 part_size;
+	int id;
+
+	if (!blk_queue_dax(bdev->bd_disk->queue))
+		return NULL;
+
+	*start_off = get_start_sect(bdev) * SECTOR_SIZE;
+	part_size = bdev_nr_sectors(bdev) * SECTOR_SIZE;
+	if (*start_off % PAGE_SIZE || part_size % PAGE_SIZE) {
+		pr_info("%pg: error: unaligned partition for dax\n", bdev);
+		return NULL;
+	}
+
+	id = dax_read_lock();
+	dax_dev = xa_load(&dax_hosts, (unsigned long)bdev->bd_disk);
+	if (!dax_dev || !dax_alive(dax_dev) || !igrab(&dax_dev->inode))
+		dax_dev = NULL;
+	else if (holder) {
+		if (!cmpxchg(&dax_dev->holder_data, NULL, holder))
+			dax_dev->holder_ops = ops;
+		else
+			dax_dev = NULL;
+	}
+	dax_read_unlock(id);
+
+	return dax_dev;
+}
+EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);
+
+void fs_put_dax(struct dax_device *dax_dev, void *holder)
+{
+	if (dax_dev && holder &&
+	    cmpxchg(&dax_dev->holder_data, holder, NULL) == holder)
+		dax_dev->holder_ops = NULL;
+	put_dax(dax_dev);
+}
+EXPORT_SYMBOL_GPL(fs_put_dax);
+#endif /* CONFIG_BLOCK && CONFIG_FS_DAX */
+
+enum dax_device_flags {
+	/* !alive + rcu grace period == no new operations / mappings */
+	DAXDEV_ALIVE,
+	/* gate whether dax_flush() calls the low level flush routine */
+	DAXDEV_WRITE_CACHE,
+	/* flag to check if device supports synchronous flush */
+	DAXDEV_SYNC,
+	/* do not leave the caches dirty after writes */
+	DAXDEV_NOCACHE,
+	/* handle CPU fetch exceptions during reads */
+	DAXDEV_NOMC,
+};
+
+/**
+ * dax_direct_access() - translate a device pgoff to an absolute pfn
+ * @dax_dev: a dax_device instance representing the logical memory range
+ * @pgoff: offset in pages from the start of the device to translate
+ * @nr_pages: number of consecutive pages caller can handle relative to @pfn
+ * @mode: indicator on normal access or recovery write
+ * @kaddr: output parameter that returns a virtual address mapping of pfn
+ * @pfn: output parameter that returns an absolute pfn translation of @pgoff
+ *
+ * Return: negative errno if an error occurs, otherwise the number of
+ * pages accessible at the device relative @pgoff.
+ */
+long dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, long nr_pages,
+		enum dax_access_mode mode, void **kaddr, pfn_t *pfn)
+{
+	long avail;
+
+	if (!dax_dev)
+		return -EOPNOTSUPP;
+
+	if (!dax_alive(dax_dev))
+		return -ENXIO;
+
+	if (nr_pages < 0)
+		return -EINVAL;
+
+	avail = dax_dev->ops->direct_access(dax_dev, pgoff, nr_pages,
+			mode, kaddr, pfn);
+	if (!avail)
+		return -ERANGE;
+	return min(avail, nr_pages);
+}
+EXPORT_SYMBOL_GPL(dax_direct_access);
+
+size_t dax_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
+		size_t bytes, struct iov_iter *i)
+{
+	if (!dax_alive(dax_dev))
+		return 0;
+
+	/*
+	 * The userspace address for the memory copy has already been validated
+	 * via access_ok() in vfs_write, so use the 'no check' version to bypass
+	 * the HARDENED_USERCOPY overhead.
+	 */
+	if (test_bit(DAXDEV_NOCACHE, &dax_dev->flags))
+		return _copy_from_iter_flushcache(addr, bytes, i);
+	return _copy_from_iter(addr, bytes, i);
+}
+
+size_t dax_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
+		size_t bytes, struct iov_iter *i)
+{
+	if (!dax_alive(dax_dev))
+		return 0;
+
+	/*
+	 * The userspace address for the memory copy has already been validated
+	 * via access_ok() in vfs_red, so use the 'no check' version to bypass
+	 * the HARDENED_USERCOPY overhead.
+	 */
+	if (test_bit(DAXDEV_NOMC, &dax_dev->flags))
+		return _copy_mc_to_iter(addr, bytes, i);
+	return _copy_to_iter(addr, bytes, i);
+}
+
+int dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff,
+			size_t nr_pages)
+{
+	if (!dax_alive(dax_dev))
+		return -ENXIO;
+	/*
+	 * There are no callers that want to zero more than one page as of now.
+	 * Once users are there, this check can be removed after the
+	 * device mapper code has been updated to split ranges across targets.
+	 */
+	if (nr_pages != 1)
+		return -EIO;
+
+	return dax_dev->ops->zero_page_range(dax_dev, pgoff, nr_pages);
+}
+EXPORT_SYMBOL_GPL(dax_zero_page_range);
+
+size_t dax_recovery_write(struct dax_device *dax_dev, pgoff_t pgoff,
+		void *addr, size_t bytes, struct iov_iter *iter)
+{
+	if (!dax_dev->ops->recovery_write)
+		return 0;
+	return dax_dev->ops->recovery_write(dax_dev, pgoff, addr, bytes, iter);
+}
+EXPORT_SYMBOL_GPL(dax_recovery_write);
+
+int dax_holder_notify_failure(struct dax_device *dax_dev, u64 off,
+			      u64 len, int mf_flags)
+{
+	int rc, id;
+
+	id = dax_read_lock();
+	if (!dax_alive(dax_dev)) {
+		rc = -ENXIO;
+		goto out;
+	}
+
+	if (!dax_dev->holder_ops) {
+		rc = -EOPNOTSUPP;
+		goto out;
+	}
+
+	rc = dax_dev->holder_ops->notify_failure(dax_dev, off, len, mf_flags);
+out:
+	dax_read_unlock(id);
+	return rc;
+}
+EXPORT_SYMBOL_GPL(dax_holder_notify_failure);
+
+#ifdef CONFIG_ARCH_HAS_PMEM_API
+void arch_wb_cache_pmem(void *addr, size_t size);
+void dax_flush(struct dax_device *dax_dev, void *addr, size_t size)
+{
+	if (unlikely(!dax_write_cache_enabled(dax_dev)))
+		return;
+
+	arch_wb_cache_pmem(addr, size);
+}
+#else
+void dax_flush(struct dax_device *dax_dev, void *addr, size_t size)
+{
+}
+#endif
+EXPORT_SYMBOL_GPL(dax_flush);
+
+void dax_write_cache(struct dax_device *dax_dev, bool wc)
+{
+	if (wc)
+		set_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
+	else
+		clear_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(dax_write_cache);
+
+bool dax_write_cache_enabled(struct dax_device *dax_dev)
+{
+	return test_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
+
+bool dax_synchronous(struct dax_device *dax_dev)
+{
+	return test_bit(DAXDEV_SYNC, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(dax_synchronous);
+
+void set_dax_synchronous(struct dax_device *dax_dev)
+{
+	set_bit(DAXDEV_SYNC, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(set_dax_synchronous);
+
+void set_dax_nocache(struct dax_device *dax_dev)
+{
+	set_bit(DAXDEV_NOCACHE, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(set_dax_nocache);
+
+void set_dax_nomc(struct dax_device *dax_dev)
+{
+	set_bit(DAXDEV_NOMC, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(set_dax_nomc);
+
+bool dax_alive(struct dax_device *dax_dev)
+{
+	lockdep_assert_held(&dax_srcu);
+	return test_bit(DAXDEV_ALIVE, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(dax_alive);
+
+/*
+ * Note, rcu is not protecting the liveness of dax_dev, rcu is ensuring
+ * that any fault handlers or operations that might have seen
+ * dax_alive(), have completed.  Any operations that start after
+ * synchronize_srcu() has run will abort upon seeing !dax_alive().
+ */
+void kill_dax(struct dax_device *dax_dev)
+{
+	if (!dax_dev)
+		return;
+
+	if (dax_dev->holder_data != NULL)
+		dax_holder_notify_failure(dax_dev, 0, U64_MAX, 0);
+
+	clear_bit(DAXDEV_ALIVE, &dax_dev->flags);
+	synchronize_srcu(&dax_srcu);
+
+	/* clear holder data */
+	dax_dev->holder_ops = NULL;
+	dax_dev->holder_data = NULL;
+}
+EXPORT_SYMBOL_GPL(kill_dax);
+
+void run_dax(struct dax_device *dax_dev)
+{
+	set_bit(DAXDEV_ALIVE, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(run_dax);
+
+static struct inode *dax_alloc_inode(struct super_block *sb)
+{
+	struct dax_device *dax_dev;
+	struct inode *inode;
+
+	dax_dev = alloc_inode_sb(sb, dax_cache, GFP_KERNEL);
+	if (!dax_dev)
+		return NULL;
+
+	inode = &dax_dev->inode;
+	inode->i_rdev = 0;
+	return inode;
+}
+
+static struct dax_device *to_dax_dev(struct inode *inode)
+{
+	return container_of(inode, struct dax_device, inode);
+}
+
+static void dax_free_inode(struct inode *inode)
+{
+	struct dax_device *dax_dev = to_dax_dev(inode);
+	if (inode->i_rdev)
+		ida_free(&dax_minor_ida, iminor(inode));
+	kmem_cache_free(dax_cache, dax_dev);
+}
+
+static void dax_destroy_inode(struct inode *inode)
+{
+	struct dax_device *dax_dev = to_dax_dev(inode);
+	WARN_ONCE(test_bit(DAXDEV_ALIVE, &dax_dev->flags),
+			"kill_dax() must be called before final iput()\n");
+}
+
+static const struct super_operations dax_sops = {
+	.statfs = simple_statfs,
+	.alloc_inode = dax_alloc_inode,
+	.destroy_inode = dax_destroy_inode,
+	.free_inode = dax_free_inode,
+	.drop_inode = generic_delete_inode,
+};
+
+static int dax_init_fs_context(struct fs_context *fc)
+{
+	struct pseudo_fs_context *ctx = init_pseudo(fc, DAXFS_MAGIC);
+	if (!ctx)
+		return -ENOMEM;
+	ctx->ops = &dax_sops;
+	return 0;
+}
+
+static struct file_system_type dax_fs_type = {
+	.name		= "dax",
+	.init_fs_context = dax_init_fs_context,
+	.kill_sb	= kill_anon_super,
+};
+
+static int dax_test(struct inode *inode, void *data)
+{
+	dev_t devt = *(dev_t *) data;
+
+	return inode->i_rdev == devt;
+}
+
+static int dax_set(struct inode *inode, void *data)
+{
+	dev_t devt = *(dev_t *) data;
+
+	inode->i_rdev = devt;
+	return 0;
+}
+
+static struct dax_device *dax_dev_get(dev_t devt)
+{
+	struct dax_device *dax_dev;
+	struct inode *inode;
+
+	inode = iget5_locked(dax_superblock, hash_32(devt + DAXFS_MAGIC, 31),
+			dax_test, dax_set, &devt);
+
+	if (!inode)
+		return NULL;
+
+	dax_dev = to_dax_dev(inode);
+	if (inode->i_state & I_NEW) {
+		set_bit(DAXDEV_ALIVE, &dax_dev->flags);
+		inode->i_cdev = &dax_dev->cdev;
+		inode->i_mode = S_IFCHR;
+		inode->i_flags = S_DAX;
+		mapping_set_gfp_mask(&inode->i_data, GFP_USER);
+		unlock_new_inode(inode);
+	}
+
+	return dax_dev;
+}
+
+struct dax_device *alloc_dax(void *private, const struct dax_operations *ops)
+{
+	struct dax_device *dax_dev;
+	dev_t devt;
+	int minor;
+
+	if (WARN_ON_ONCE(ops && !ops->zero_page_range))
+		return ERR_PTR(-EINVAL);
+
+	minor = ida_alloc_max(&dax_minor_ida, MINORMASK, GFP_KERNEL);
+	if (minor < 0)
+		return ERR_PTR(-ENOMEM);
+
+	devt = MKDEV(MAJOR(dax_devt), minor);
+	dax_dev = dax_dev_get(devt);
+	if (!dax_dev)
+		goto err_dev;
+
+	dax_dev->ops = ops;
+	dax_dev->private = private;
+	return dax_dev;
+
+ err_dev:
+	ida_free(&dax_minor_ida, minor);
+	return ERR_PTR(-ENOMEM);
+}
+EXPORT_SYMBOL_GPL(alloc_dax);
+
+void put_dax(struct dax_device *dax_dev)
+{
+	if (!dax_dev)
+		return;
+	iput(&dax_dev->inode);
+}
+EXPORT_SYMBOL_GPL(put_dax);
+
+/**
+ * dax_holder() - obtain the holder of a dax device
+ * @dax_dev: a dax_device instance
+
+ * Return: the holder's data which represents the holder if registered,
+ * otherwize NULL.
+ */
+void *dax_holder(struct dax_device *dax_dev)
+{
+	return dax_dev->holder_data;
+}
+EXPORT_SYMBOL_GPL(dax_holder);
+
+/**
+ * inode_dax: convert a public inode into its dax_dev
+ * @inode: An inode with i_cdev pointing to a dax_dev
+ *
+ * Note this is not equivalent to to_dax_dev() which is for private
+ * internal use where we know the inode filesystem type == dax_fs_type.
+ */
+struct dax_device *inode_dax(struct inode *inode)
+{
+	struct cdev *cdev = inode->i_cdev;
+
+	return container_of(cdev, struct dax_device, cdev);
+}
+EXPORT_SYMBOL_GPL(inode_dax);
+
+struct inode *dax_inode(struct dax_device *dax_dev)
+{
+	return &dax_dev->inode;
+}
+EXPORT_SYMBOL_GPL(dax_inode);
+
+void *dax_get_private(struct dax_device *dax_dev)
+{
+	if (!test_bit(DAXDEV_ALIVE, &dax_dev->flags))
+		return NULL;
+	return dax_dev->private;
+}
+EXPORT_SYMBOL_GPL(dax_get_private);
+
+static void init_once(void *_dax_dev)
+{
+	struct dax_device *dax_dev = _dax_dev;
+	struct inode *inode = &dax_dev->inode;
+
+	memset(dax_dev, 0, sizeof(*dax_dev));
+	inode_init_once(inode);
+}
+
+static int dax_fs_init(void)
+{
+	int rc;
+
+	dax_cache = kmem_cache_create("dax_cache", sizeof(struct dax_device), 0,
+			(SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
+			 SLAB_MEM_SPREAD|SLAB_ACCOUNT),
+			init_once);
+	if (!dax_cache)
+		return -ENOMEM;
+
+	dax_mnt = kern_mount(&dax_fs_type);
+	if (IS_ERR(dax_mnt)) {
+		rc = PTR_ERR(dax_mnt);
+		goto err_mount;
+	}
+	dax_superblock = dax_mnt->mnt_sb;
+
+	return 0;
+
+ err_mount:
+	kmem_cache_destroy(dax_cache);
+
+	return rc;
+}
+
+static void dax_fs_exit(void)
+{
+	kern_unmount(dax_mnt);
+	rcu_barrier();
+	kmem_cache_destroy(dax_cache);
+}
+
+static int __init dax_core_init(void)
+{
+	int rc;
+
+	rc = dax_fs_init();
+	if (rc)
+		return rc;
+
+	rc = alloc_chrdev_region(&dax_devt, 0, MINORMASK+1, "dax");
+	if (rc)
+		goto err_chrdev;
+
+	rc = dax_bus_init();
+	if (rc)
+		goto err_bus;
+	return 0;
+
+err_bus:
+	unregister_chrdev_region(dax_devt, MINORMASK+1);
+err_chrdev:
+	dax_fs_exit();
+	return 0;
+}
+
+static void __exit dax_core_exit(void)
+{
+	dax_bus_exit();
+	unregister_chrdev_region(dax_devt, MINORMASK+1);
+	ida_destroy(&dax_minor_ida);
+	dax_fs_exit();
+}
+
+MODULE_AUTHOR("Intel Corporation");
+MODULE_LICENSE("GPL v2");
+subsys_initcall(dax_core_init);
+module_exit(dax_core_exit);