[mirror_ubuntu-artful-kernel.git] / drivers / dax / super.c

/*
 * Copyright(c) 2017 Intel Corporation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that 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/pagemap.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/magic.h>
#include <linux/genhd.h>
#include <linux/cdev.h>
#include <linux/hash.h>
#include <linux/slab.h>
#include <linux/uio.h>
#include <linux/dax.h>
#include <linux/fs.h>

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;

#define DAX_HASH_SIZE (PAGE_SIZE / sizeof(struct hlist_head))
static struct hlist_head dax_host_list[DAX_HASH_SIZE];
static DEFINE_SPINLOCK(dax_host_lock);

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);

#ifdef CONFIG_BLOCK
int bdev_dax_pgoff(struct block_device *bdev, sector_t sector, size_t size,
		pgoff_t *pgoff)
{
	phys_addr_t phys_off = (get_start_sect(bdev) + sector) * 512;

	if (pgoff)
		*pgoff = PHYS_PFN(phys_off);
	if (phys_off % PAGE_SIZE || size % PAGE_SIZE)
		return -EINVAL;
	return 0;
}
EXPORT_SYMBOL(bdev_dax_pgoff);

/**
 * __bdev_dax_supported() - Check if the device supports dax for filesystem
 * @sb: The superblock of the device
 * @blocksize: The block size of the device
 *
 * This is a library function for filesystems to check if the block device
 * can be mounted with dax option.
 *
 * Return: negative errno if unsupported, 0 if supported.
 */
int __bdev_dax_supported(struct super_block *sb, int blocksize)
{
	struct block_device *bdev = sb->s_bdev;
	struct dax_device *dax_dev;
	pgoff_t pgoff;
	int err, id;
	void *kaddr;
	pfn_t pfn;
	long len;

	if (blocksize != PAGE_SIZE) {
		pr_err("VFS (%s): error: unsupported blocksize for dax\n",
				sb->s_id);
		return -EINVAL;
	}

	err = bdev_dax_pgoff(bdev, 0, PAGE_SIZE, &pgoff);
	if (err) {
		pr_err("VFS (%s): error: unaligned partition for dax\n",
				sb->s_id);
		return err;
	}

	dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
	if (!dax_dev) {
		pr_err("VFS (%s): error: device does not support dax\n",
				sb->s_id);
		return -EOPNOTSUPP;
	}

	id = dax_read_lock();
	len = dax_direct_access(dax_dev, pgoff, 1, &kaddr, &pfn);
	dax_read_unlock(id);

	put_dax(dax_dev);

	if (len < 1) {
		pr_err("VFS (%s): error: dax access failed (%ld)",
				sb->s_id, len);
		return len < 0 ? len : -EIO;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(__bdev_dax_supported);
#endif

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,
};

/**
 * struct dax_device - anchor object for dax services
 * @inode: core vfs
 * @cdev: optional character interface for "device dax"
 * @host: optional name for lookups where the device path is not available
 * @private: dax driver private data
 * @flags: state and boolean properties
 */
struct dax_device {
	struct hlist_node list;
	struct inode inode;
	struct cdev cdev;
	const char *host;
	void *private;
	unsigned long flags;
	const struct dax_operations *ops;
};

static ssize_t write_cache_show(struct device *dev,
		struct device_attribute *attr, char *buf)
{
	struct dax_device *dax_dev = dax_get_by_host(dev_name(dev));
	ssize_t rc;

	WARN_ON_ONCE(!dax_dev);
	if (!dax_dev)
		return -ENXIO;

	rc = sprintf(buf, "%d\n", !!test_bit(DAXDEV_WRITE_CACHE,
				&dax_dev->flags));
	put_dax(dax_dev);
	return rc;
}

static ssize_t write_cache_store(struct device *dev,
		struct device_attribute *attr, const char *buf, size_t len)
{
	bool write_cache;
	int rc = strtobool(buf, &write_cache);
	struct dax_device *dax_dev = dax_get_by_host(dev_name(dev));

	WARN_ON_ONCE(!dax_dev);
	if (!dax_dev)
		return -ENXIO;

	if (rc)
		len = rc;
	else if (write_cache)
		set_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
	else
		clear_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);

	put_dax(dax_dev);
	return len;
}
static DEVICE_ATTR_RW(write_cache);

static umode_t dax_visible(struct kobject *kobj, struct attribute *a, int n)
{
	struct device *dev = container_of(kobj, typeof(*dev), kobj);
	struct dax_device *dax_dev = dax_get_by_host(dev_name(dev));

	WARN_ON_ONCE(!dax_dev);
	if (!dax_dev)
		return 0;

	if (a == &dev_attr_write_cache.attr && !dax_dev->ops->flush)
		return 0;
	return a->mode;
}

static struct attribute *dax_attributes[] = {
	&dev_attr_write_cache.attr,
	NULL,
};

struct attribute_group dax_attribute_group = {
	.name = "dax",
	.attrs = dax_attributes,
	.is_visible = dax_visible,
};
EXPORT_SYMBOL_GPL(dax_attribute_group);

/**
 * 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
 * @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,
		void **kaddr, pfn_t *pfn)
{
	long avail;

	/*
	 * The device driver is allowed to sleep, in order to make the
	 * memory directly accessible.
	 */
	might_sleep();

	if (!dax_dev)
		return -EOPNOTSUPP;

	if (!dax_alive(dax_dev))
		return -ENXIO;

	if (nr_pages < 0)
		return nr_pages;

	avail = dax_dev->ops->direct_access(dax_dev, pgoff, nr_pages,
			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;

	return dax_dev->ops->copy_from_iter(dax_dev, pgoff, addr, bytes, i);
}
EXPORT_SYMBOL_GPL(dax_copy_from_iter);

void dax_flush(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
		size_t size)
{
	if (!dax_alive(dax_dev))
		return;

	if (!test_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags))
		return;

	if (dax_dev->ops->flush)
		dax_dev->ops->flush(dax_dev, pgoff, addr, size);
}
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_alive(struct dax_device *dax_dev)
{
	lockdep_assert_held(&dax_srcu);
	return test_bit(DAXDEV_ALIVE, &dax_dev->flags);
}
EXPORT_SYMBOL_GPL(dax_alive);

static int dax_host_hash(const char *host)
{
	return hashlen_hash(hashlen_string("DAX", host)) % DAX_HASH_SIZE;
}

/*
 * 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;

	clear_bit(DAXDEV_ALIVE, &dax_dev->flags);

	synchronize_srcu(&dax_srcu);

	spin_lock(&dax_host_lock);
	hlist_del_init(&dax_dev->list);
	spin_unlock(&dax_host_lock);

	dax_dev->private = NULL;
}
EXPORT_SYMBOL_GPL(kill_dax);

static struct inode *dax_alloc_inode(struct super_block *sb)
{
	struct dax_device *dax_dev;
	struct inode *inode;

	dax_dev = kmem_cache_alloc(dax_cache, GFP_KERNEL);
	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_i_callback(struct rcu_head *head)
{
	struct inode *inode = container_of(head, struct inode, i_rcu);
	struct dax_device *dax_dev = to_dax_dev(inode);

	kfree(dax_dev->host);
	dax_dev->host = NULL;
	if (inode->i_rdev)
		ida_simple_remove(&dax_minor_ida, MINOR(inode->i_rdev));
	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");
	call_rcu(&inode->i_rcu, dax_i_callback);
}

static const struct super_operations dax_sops = {
	.statfs = simple_statfs,
	.alloc_inode = dax_alloc_inode,
	.destroy_inode = dax_destroy_inode,
	.drop_inode = generic_delete_inode,
};

static struct dentry *dax_mount(struct file_system_type *fs_type,
		int flags, const char *dev_name, void *data)
{
	return mount_pseudo(fs_type, "dax:", &dax_sops, NULL, DAXFS_MAGIC);
}

static struct file_system_type dax_fs_type = {
	.name = "dax",
	.mount = dax_mount,
	.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;
}

static void dax_add_host(struct dax_device *dax_dev, const char *host)
{
	int hash;

	/*
	 * Unconditionally init dax_dev since it's coming from a
	 * non-zeroed slab cache
	 */
	INIT_HLIST_NODE(&dax_dev->list);
	dax_dev->host = host;
	if (!host)
		return;

	hash = dax_host_hash(host);
	spin_lock(&dax_host_lock);
	hlist_add_head(&dax_dev->list, &dax_host_list[hash]);
	spin_unlock(&dax_host_lock);
}

struct dax_device *alloc_dax(void *private, const char *__host,
		const struct dax_operations *ops)
{
	struct dax_device *dax_dev;
	const char *host;
	dev_t devt;
	int minor;

	host = kstrdup(__host, GFP_KERNEL);
	if (__host && !host)
		return NULL;

	minor = ida_simple_get(&dax_minor_ida, 0, MINORMASK+1, GFP_KERNEL);
	if (minor < 0)
		goto err_minor;

	devt = MKDEV(MAJOR(dax_devt), minor);
	dax_dev = dax_dev_get(devt);
	if (!dax_dev)
		goto err_dev;

	dax_add_host(dax_dev, host);
	dax_dev->ops = ops;
	dax_dev->private = private;
	return dax_dev;

 err_dev:
	ida_simple_remove(&dax_minor_ida, minor);
 err_minor:
	kfree(host);
	return NULL;
}
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_get_by_host() - temporary lookup mechanism for filesystem-dax
 * @host: alternate name for the device registered by a dax driver
 */
struct dax_device *dax_get_by_host(const char *host)
{
	struct dax_device *dax_dev, *found = NULL;
	int hash, id;

	if (!host)
		return NULL;

	hash = dax_host_hash(host);

	id = dax_read_lock();
	spin_lock(&dax_host_lock);
	hlist_for_each_entry(dax_dev, &dax_host_list[hash], list) {
		if (!dax_alive(dax_dev)
				|| strcmp(host, dax_dev->host) != 0)
			continue;

		if (igrab(&dax_dev->inode))
			found = dax_dev;
		break;
	}
	spin_unlock(&dax_host_lock);
	dax_read_unlock(id);

	return found;
}
EXPORT_SYMBOL_GPL(dax_get_by_host);

/**
 * 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)
{
	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;

	rc = register_filesystem(&dax_fs_type);
	if (rc)
		goto err_register_fs;

	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:
	unregister_filesystem(&dax_fs_type);
 err_register_fs:
	kmem_cache_destroy(dax_cache);

	return rc;
}

static void __dax_fs_exit(void)
{
	kern_unmount(dax_mnt);
	unregister_filesystem(&dax_fs_type);
	kmem_cache_destroy(dax_cache);
}

static int __init dax_fs_init(void)
{
	int rc;

	rc = __dax_fs_init();
	if (rc)
		return rc;

	rc = alloc_chrdev_region(&dax_devt, 0, MINORMASK+1, "dax");
	if (rc)
		__dax_fs_exit();
	return rc;
}

static void __exit dax_fs_exit(void)
{
	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_fs_init);
module_exit(dax_fs_exit);
Commit	Line	Data
7b6be844 DW	1	/*
	2	* Copyright(c) 2017 Intel Corporation. All rights reserved.
	3	*
	4	* This program is free software; you can redistribute it and/or modify
	5	* it under the terms of version 2 of the GNU General Public License as
	6	* published by the Free Software Foundation.
	7	*
	8	* This program is distributed in the hope that it will be useful, but
	9	* WITHOUT ANY WARRANTY; without even the implied warranty of
	10	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	11	* General Public License for more details.
	12	*/
	13	#include <linux/pagemap.h>
	14	#include <linux/module.h>
	15	#include <linux/mount.h>
	16	#include <linux/magic.h>
ef510424	17	#include <linux/genhd.h>
7b6be844 DW	18	#include <linux/cdev.h>
	19	#include <linux/hash.h>
	20	#include <linux/slab.h>
7e026c8c	21	#include <linux/uio.h>
6568b08b	22	#include <linux/dax.h>
7b6be844 DW	23	#include <linux/fs.h>
7b6be844 DW	24
7b6be844 DW	25	static dev_t dax_devt;
	26	DEFINE_STATIC_SRCU(dax_srcu);
	27	static struct vfsmount *dax_mnt;
	28	static DEFINE_IDA(dax_minor_ida);
	29	static struct kmem_cache *dax_cache __read_mostly;
	30	static struct super_block *dax_superblock __read_mostly;
	31
72058005 DW	32	#define DAX_HASH_SIZE (PAGE_SIZE / sizeof(struct hlist_head))
	33	static struct hlist_head dax_host_list[DAX_HASH_SIZE];
	34	static DEFINE_SPINLOCK(dax_host_lock);
	35
7b6be844 DW	36	int dax_read_lock(void)
	37	{
	38	return srcu_read_lock(&dax_srcu);
	39	}
	40	EXPORT_SYMBOL_GPL(dax_read_lock);
	41
	42	void dax_read_unlock(int id)
	43	{
	44	srcu_read_unlock(&dax_srcu, id);
	45	}
	46	EXPORT_SYMBOL_GPL(dax_read_unlock);
	47
9d109081	48	#ifdef CONFIG_BLOCK
ef510424 DW	49	int bdev_dax_pgoff(struct block_device *bdev, sector_t sector, size_t size,
	50	pgoff_t *pgoff)
	51	{
	52	phys_addr_t phys_off = (get_start_sect(bdev) + sector) * 512;
	53
	54	if (pgoff)
	55	*pgoff = PHYS_PFN(phys_off);
	56	if (phys_off % PAGE_SIZE \|\| size % PAGE_SIZE)
	57	return -EINVAL;
	58	return 0;
	59	}
	60	EXPORT_SYMBOL(bdev_dax_pgoff);
	61
	62	/**
	63	* __bdev_dax_supported() - Check if the device supports dax for filesystem
	64	* @sb: The superblock of the device
	65	* @blocksize: The block size of the device
	66	*
	67	* This is a library function for filesystems to check if the block device
	68	* can be mounted with dax option.
	69	*
	70	* Return: negative errno if unsupported, 0 if supported.
	71	*/
	72	int __bdev_dax_supported(struct super_block *sb, int blocksize)
	73	{
	74	struct block_device *bdev = sb->s_bdev;
	75	struct dax_device *dax_dev;
	76	pgoff_t pgoff;
	77	int err, id;
	78	void *kaddr;
	79	pfn_t pfn;
	80	long len;
	81
	82	if (blocksize != PAGE_SIZE) {
	83	pr_err("VFS (%s): error: unsupported blocksize for dax\n",
	84	sb->s_id);
	85	return -EINVAL;
	86	}
	87
	88	err = bdev_dax_pgoff(bdev, 0, PAGE_SIZE, &pgoff);
	89	if (err) {
	90	pr_err("VFS (%s): error: unaligned partition for dax\n",
	91	sb->s_id);
	92	return err;
	93	}
	94
	95	dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
	96	if (!dax_dev) {
	97	pr_err("VFS (%s): error: device does not support dax\n",
	98	sb->s_id);
	99	return -EOPNOTSUPP;
	100	}
	101
	102	id = dax_read_lock();
	103	len = dax_direct_access(dax_dev, pgoff, 1, &kaddr, &pfn);
	104	dax_read_unlock(id);
	105
	106	put_dax(dax_dev);
	107
	108	if (len < 1) {
	109	pr_err("VFS (%s): error: dax access failed (%ld)",
	110	sb->s_id, len);
	111	return len < 0 ? len : -EIO;
	112	}
113
114	return 0;
115	}
116	EXPORT_SYMBOL_GPL(__bdev_dax_supported);
9d109081	117	#endif
ef510424	118
9a60c3ef DW	119	enum dax_device_flags {
	120	/* !alive + rcu grace period == no new operations / mappings */
	121	DAXDEV_ALIVE,
6e0c90d6 DW	122	/* gate whether dax_flush() calls the low level flush routine */
6e0c90d6 DW	123	DAXDEV_WRITE_CACHE,
9a60c3ef DW	124	};
9a60c3ef DW	125
7b6be844 DW	126	/**
	127	* struct dax_device - anchor object for dax services
	128	* @inode: core vfs
	129	* @cdev: optional character interface for "device dax"
72058005	130	* @host: optional name for lookups where the device path is not available
7b6be844	131	* @private: dax driver private data
9a60c3ef	132	* @flags: state and boolean properties
7b6be844 DW	133	*/
7b6be844 DW	134	struct dax_device {
72058005	135	struct hlist_node list;
7b6be844 DW	136	struct inode inode;
7b6be844 DW	137	struct cdev cdev;
72058005	138	const char *host;
7b6be844	139	void *private;
9a60c3ef	140	unsigned long flags;
6568b08b	141	const struct dax_operations *ops;
7b6be844 DW	142	};
7b6be844 DW	143
6e0c90d6 DW	144	static ssize_t write_cache_show(struct device *dev,
	145	struct device_attribute attr, char buf)
	146	{
	147	struct dax_device *dax_dev = dax_get_by_host(dev_name(dev));
	148	ssize_t rc;
	149
	150	WARN_ON_ONCE(!dax_dev);
	151	if (!dax_dev)
	152	return -ENXIO;
	153
	154	rc = sprintf(buf, "%d\n", !!test_bit(DAXDEV_WRITE_CACHE,
	155	&dax_dev->flags));
	156	put_dax(dax_dev);
	157	return rc;
	158	}
	159
	160	static ssize_t write_cache_store(struct device *dev,
	161	struct device_attribute attr, const char buf, size_t len)
	162	{
	163	bool write_cache;
	164	int rc = strtobool(buf, &write_cache);
	165	struct dax_device *dax_dev = dax_get_by_host(dev_name(dev));
	166
	167	WARN_ON_ONCE(!dax_dev);
	168	if (!dax_dev)
	169	return -ENXIO;
	170
	171	if (rc)
	172	len = rc;
	173	else if (write_cache)
	174	set_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
	175	else
	176	clear_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
	177
	178	put_dax(dax_dev);
	179	return len;
	180	}
	181	static DEVICE_ATTR_RW(write_cache);
	182
	183	static umode_t dax_visible(struct kobject kobj, struct attribute a, int n)
	184	{
	185	struct device dev = container_of(kobj, typeof(dev), kobj);
	186	struct dax_device *dax_dev = dax_get_by_host(dev_name(dev));
	187
	188	WARN_ON_ONCE(!dax_dev);
	189	if (!dax_dev)
	190	return 0;
	191
	192	if (a == &dev_attr_write_cache.attr && !dax_dev->ops->flush)
	193	return 0;
	194	return a->mode;
	195	}
	196
	197	static struct attribute *dax_attributes[] = {
	198	&dev_attr_write_cache.attr,
	199	NULL,
	200	};
	201
	202	struct attribute_group dax_attribute_group = {
	203	.name = "dax",
	204	.attrs = dax_attributes,
	205	.is_visible = dax_visible,
	206	};
	207	EXPORT_SYMBOL_GPL(dax_attribute_group);
208
b0686260 DW	209	/**
	210	* dax_direct_access() - translate a device pgoff to an absolute pfn
	211	* @dax_dev: a dax_device instance representing the logical memory range
	212	* @pgoff: offset in pages from the start of the device to translate
	213	* @nr_pages: number of consecutive pages caller can handle relative to @pfn
	214	* @kaddr: output parameter that returns a virtual address mapping of pfn
	215	* @pfn: output parameter that returns an absolute pfn translation of @pgoff
	216	*
	217	* Return: negative errno if an error occurs, otherwise the number of
	218	* pages accessible at the device relative @pgoff.
	219	*/
	220	long dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, long nr_pages,
	221	void *kaddr, pfn_t pfn)
	222	{
	223	long avail;
	224
	225	/*
	226	* The device driver is allowed to sleep, in order to make the
	227	* memory directly accessible.
	228	*/
	229	might_sleep();
	230
	231	if (!dax_dev)
	232	return -EOPNOTSUPP;
	233
	234	if (!dax_alive(dax_dev))
	235	return -ENXIO;
	236
	237	if (nr_pages < 0)
	238	return nr_pages;
	239
	240	avail = dax_dev->ops->direct_access(dax_dev, pgoff, nr_pages,
	241	kaddr, pfn);
	242	if (!avail)
	243	return -ERANGE;
	244	return min(avail, nr_pages);
	245	}
	246	EXPORT_SYMBOL_GPL(dax_direct_access);
	247
7e026c8c DW	248	size_t dax_copy_from_iter(struct dax_device dax_dev, pgoff_t pgoff, void addr,
	249	size_t bytes, struct iov_iter *i)
	250	{
	251	if (!dax_alive(dax_dev))
	252	return 0;
	253
7e026c8c DW	254	return dax_dev->ops->copy_from_iter(dax_dev, pgoff, addr, bytes, i);
	255	}
	256	EXPORT_SYMBOL_GPL(dax_copy_from_iter);
	257
abebfbe2 DW	258	void dax_flush(struct dax_device dax_dev, pgoff_t pgoff, void addr,
	259	size_t size)
	260	{
	261	if (!dax_alive(dax_dev))
	262	return;
	263
6e0c90d6 DW	264	if (!test_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags))
	265	return;
	266
abebfbe2 DW	267	if (dax_dev->ops->flush)
	268	dax_dev->ops->flush(dax_dev, pgoff, addr, size);
	269	}
	270	EXPORT_SYMBOL_GPL(dax_flush);
	271
6e0c90d6 DW	272	void dax_write_cache(struct dax_device *dax_dev, bool wc)
	273	{
	274	if (wc)
	275	set_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
	276	else
	277	clear_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
	278	}
	279	EXPORT_SYMBOL_GPL(dax_write_cache);
	280
273752c9 VG	281	bool dax_write_cache_enabled(struct dax_device *dax_dev)
	282	{
	283	return test_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
	284	}
	285	EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
	286
7b6be844 DW	287	bool dax_alive(struct dax_device *dax_dev)
	288	{
	289	lockdep_assert_held(&dax_srcu);
9a60c3ef	290	return test_bit(DAXDEV_ALIVE, &dax_dev->flags);
7b6be844 DW	291	}
	292	EXPORT_SYMBOL_GPL(dax_alive);
	293
72058005 DW	294	static int dax_host_hash(const char *host)
	295	{
	296	return hashlen_hash(hashlen_string("DAX", host)) % DAX_HASH_SIZE;
	297	}
	298
7b6be844 DW	299	/*
	300	* Note, rcu is not protecting the liveness of dax_dev, rcu is ensuring
	301	* that any fault handlers or operations that might have seen
	302	* dax_alive(), have completed. Any operations that start after
	303	* synchronize_srcu() has run will abort upon seeing !dax_alive().
	304	*/
	305	void kill_dax(struct dax_device *dax_dev)
	306	{
	307	if (!dax_dev)
	308	return;
	309
9a60c3ef	310	clear_bit(DAXDEV_ALIVE, &dax_dev->flags);
72058005	311
7b6be844	312	synchronize_srcu(&dax_srcu);
72058005 DW	313
	314	spin_lock(&dax_host_lock);
	315	hlist_del_init(&dax_dev->list);
	316	spin_unlock(&dax_host_lock);
	317
7b6be844 DW	318	dax_dev->private = NULL;
	319	}
	320	EXPORT_SYMBOL_GPL(kill_dax);
	321
	322	static struct inode dax_alloc_inode(struct super_block sb)
	323	{
	324	struct dax_device *dax_dev;
b9d39d17	325	struct inode *inode;
7b6be844 DW	326
7b6be844 DW	327	dax_dev = kmem_cache_alloc(dax_cache, GFP_KERNEL);
b9d39d17 DW	328	inode = &dax_dev->inode;
	329	inode->i_rdev = 0;
	330	return inode;
7b6be844 DW	331	}
	332
	333	static struct dax_device to_dax_dev(struct inode inode)
	334	{
	335	return container_of(inode, struct dax_device, inode);
	336	}
	337
	338	static void dax_i_callback(struct rcu_head *head)
	339	{
	340	struct inode *inode = container_of(head, struct inode, i_rcu);
	341	struct dax_device *dax_dev = to_dax_dev(inode);
	342
72058005 DW	343	kfree(dax_dev->host);
72058005 DW	344	dax_dev->host = NULL;
b9d39d17 DW	345	if (inode->i_rdev)
b9d39d17 DW	346	ida_simple_remove(&dax_minor_ida, MINOR(inode->i_rdev));
7b6be844 DW	347	kmem_cache_free(dax_cache, dax_dev);
	348	}
	349
	350	static void dax_destroy_inode(struct inode *inode)
	351	{
	352	struct dax_device *dax_dev = to_dax_dev(inode);
	353
9a60c3ef	354	WARN_ONCE(test_bit(DAXDEV_ALIVE, &dax_dev->flags),
7b6be844 DW	355	"kill_dax() must be called before final iput()\n");
	356	call_rcu(&inode->i_rcu, dax_i_callback);
	357	}
	358
	359	static const struct super_operations dax_sops = {
	360	.statfs = simple_statfs,
	361	.alloc_inode = dax_alloc_inode,
	362	.destroy_inode = dax_destroy_inode,
	363	.drop_inode = generic_delete_inode,
	364	};
	365
	366	static struct dentry dax_mount(struct file_system_type fs_type,
	367	int flags, const char dev_name, void data)
	368	{
	369	return mount_pseudo(fs_type, "dax:", &dax_sops, NULL, DAXFS_MAGIC);
	370	}
	371
	372	static struct file_system_type dax_fs_type = {
	373	.name = "dax",
	374	.mount = dax_mount,
	375	.kill_sb = kill_anon_super,
	376	};
	377
	378	static int dax_test(struct inode inode, void data)
	379	{
	380	dev_t devt = (dev_t ) data;
	381
	382	return inode->i_rdev == devt;
	383	}
	384
	385	static int dax_set(struct inode inode, void data)
	386	{
	387	dev_t devt = (dev_t ) data;
	388
	389	inode->i_rdev = devt;
	390	return 0;
	391	}
	392
	393	static struct dax_device *dax_dev_get(dev_t devt)
	394	{
	395	struct dax_device *dax_dev;
	396	struct inode *inode;
	397
	398	inode = iget5_locked(dax_superblock, hash_32(devt + DAXFS_MAGIC, 31),
	399	dax_test, dax_set, &devt);
	400
	401	if (!inode)
	402	return NULL;
	403
	404	dax_dev = to_dax_dev(inode);
	405	if (inode->i_state & I_NEW) {
9a60c3ef	406	set_bit(DAXDEV_ALIVE, &dax_dev->flags);
7b6be844 DW	407	inode->i_cdev = &dax_dev->cdev;
	408	inode->i_mode = S_IFCHR;
	409	inode->i_flags = S_DAX;
	410	mapping_set_gfp_mask(&inode->i_data, GFP_USER);
	411	unlock_new_inode(inode);
	412	}
	413
	414	return dax_dev;
	415	}
	416
72058005 DW	417	static void dax_add_host(struct dax_device dax_dev, const char host)
	418	{
	419	int hash;
	420
	421	/*
	422	* Unconditionally init dax_dev since it's coming from a
	423	* non-zeroed slab cache
	424	*/
	425	INIT_HLIST_NODE(&dax_dev->list);
	426	dax_dev->host = host;
	427	if (!host)
	428	return;
	429
	430	hash = dax_host_hash(host);
	431	spin_lock(&dax_host_lock);
	432	hlist_add_head(&dax_dev->list, &dax_host_list[hash]);
	433	spin_unlock(&dax_host_lock);
	434	}
	435
6568b08b DW	436	struct dax_device alloc_dax(void private, const char *__host,
6568b08b DW	437	const struct dax_operations *ops)
7b6be844 DW	438	{
7b6be844 DW	439	struct dax_device *dax_dev;
72058005	440	const char *host;
7b6be844 DW	441	dev_t devt;
	442	int minor;
	443
72058005 DW	444	host = kstrdup(__host, GFP_KERNEL);
	445	if (__host && !host)
	446	return NULL;
	447
cf1e2289	448	minor = ida_simple_get(&dax_minor_ida, 0, MINORMASK+1, GFP_KERNEL);
7b6be844	449	if (minor < 0)
72058005	450	goto err_minor;
7b6be844 DW	451
	452	devt = MKDEV(MAJOR(dax_devt), minor);
	453	dax_dev = dax_dev_get(devt);
	454	if (!dax_dev)
72058005	455	goto err_dev;
7b6be844	456
72058005	457	dax_add_host(dax_dev, host);
6568b08b	458	dax_dev->ops = ops;
7b6be844 DW	459	dax_dev->private = private;
	460	return dax_dev;
	461
72058005	462	err_dev:
7b6be844	463	ida_simple_remove(&dax_minor_ida, minor);
72058005 DW	464	err_minor:
72058005 DW	465	kfree(host);
7b6be844 DW	466	return NULL;
	467	}
	468	EXPORT_SYMBOL_GPL(alloc_dax);
	469
	470	void put_dax(struct dax_device *dax_dev)
	471	{
	472	if (!dax_dev)
	473	return;
	474	iput(&dax_dev->inode);
	475	}
	476	EXPORT_SYMBOL_GPL(put_dax);
	477
72058005 DW	478	/**
	479	* dax_get_by_host() - temporary lookup mechanism for filesystem-dax
	480	* @host: alternate name for the device registered by a dax driver
	481	*/
	482	struct dax_device dax_get_by_host(const char host)
	483	{
	484	struct dax_device dax_dev, found = NULL;
	485	int hash, id;
	486
	487	if (!host)
	488	return NULL;
	489
	490	hash = dax_host_hash(host);
	491
	492	id = dax_read_lock();
	493	spin_lock(&dax_host_lock);
	494	hlist_for_each_entry(dax_dev, &dax_host_list[hash], list) {
	495	if (!dax_alive(dax_dev)
	496	\|\| strcmp(host, dax_dev->host) != 0)
	497	continue;
	498
	499	if (igrab(&dax_dev->inode))
	500	found = dax_dev;
	501	break;
	502	}
	503	spin_unlock(&dax_host_lock);
	504	dax_read_unlock(id);
	505
	506	return found;
	507	}
	508	EXPORT_SYMBOL_GPL(dax_get_by_host);
	509
7b6be844 DW	510	/**
	511	* inode_dax: convert a public inode into its dax_dev
	512	* @inode: An inode with i_cdev pointing to a dax_dev
	513	*
	514	* Note this is not equivalent to to_dax_dev() which is for private
	515	* internal use where we know the inode filesystem type == dax_fs_type.
	516	*/
	517	struct dax_device inode_dax(struct inode inode)
	518	{
	519	struct cdev *cdev = inode->i_cdev;
	520
	521	return container_of(cdev, struct dax_device, cdev);
	522	}
	523	EXPORT_SYMBOL_GPL(inode_dax);
	524
	525	struct inode dax_inode(struct dax_device dax_dev)
	526	{
	527	return &dax_dev->inode;
	528	}
	529	EXPORT_SYMBOL_GPL(dax_inode);
	530
	531	void dax_get_private(struct dax_device dax_dev)
	532	{
	533	return dax_dev->private;
	534	}
	535	EXPORT_SYMBOL_GPL(dax_get_private);
	536
	537	static void init_once(void *_dax_dev)
	538	{
	539	struct dax_device *dax_dev = _dax_dev;
	540	struct inode *inode = &dax_dev->inode;
	541
b9d39d17	542	memset(dax_dev, 0, sizeof(*dax_dev));
7b6be844 DW	543	inode_init_once(inode);
	544	}
	545
	546	static int __dax_fs_init(void)
	547	{
	548	int rc;
	549
	550	dax_cache = kmem_cache_create("dax_cache", sizeof(struct dax_device), 0,
	551	(SLAB_HWCACHE_ALIGN\|SLAB_RECLAIM_ACCOUNT\|
	552	SLAB_MEM_SPREAD\|SLAB_ACCOUNT),
	553	init_once);
	554	if (!dax_cache)
	555	return -ENOMEM;
	556
	557	rc = register_filesystem(&dax_fs_type);
	558	if (rc)
	559	goto err_register_fs;
	560
	561	dax_mnt = kern_mount(&dax_fs_type);
	562	if (IS_ERR(dax_mnt)) {
	563	rc = PTR_ERR(dax_mnt);
	564	goto err_mount;
	565	}
	566	dax_superblock = dax_mnt->mnt_sb;
	567
	568	return 0;
	569
	570	err_mount:
	571	unregister_filesystem(&dax_fs_type);
	572	err_register_fs:
	573	kmem_cache_destroy(dax_cache);
	574
	575	return rc;
	576	}
	577
	578	static void __dax_fs_exit(void)
	579	{
	580	kern_unmount(dax_mnt);
	581	unregister_filesystem(&dax_fs_type);
	582	kmem_cache_destroy(dax_cache);
	583	}
	584
	585	static int __init dax_fs_init(void)
	586	{
	587	int rc;
	588
	589	rc = __dax_fs_init();
	590	if (rc)
	591	return rc;
	592
cf1e2289	593	rc = alloc_chrdev_region(&dax_devt, 0, MINORMASK+1, "dax");
7b6be844 DW	594	if (rc)
	595	__dax_fs_exit();
	596	return rc;
	597	}
	598
	599	static void __exit dax_fs_exit(void)
	600	{
cf1e2289	601	unregister_chrdev_region(dax_devt, MINORMASK+1);
7b6be844 DW	602	ida_destroy(&dax_minor_ida);
	603	__dax_fs_exit();
	604	}
	605
	606	MODULE_AUTHOR("Intel Corporation");
	607	MODULE_LICENSE("GPL v2");
	608	subsys_initcall(dax_fs_init);
	609	module_exit(dax_fs_exit);