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/*
* 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/pfn_t.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
#include <linux/blkdev.h>
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);
#if IS_ENABLED(CONFIG_FS_DAX)
struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev)
{
if (!blk_queue_dax(bdev->bd_queue))
return NULL;
return fs_dax_get_by_host(bdev->bd_disk->disk_name);
}
EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);
#endif
/**
* __bdev_dax_supported() - Check if the device supports dax for filesystem
* @bdev: block device to check
* @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 block_device *bdev, int blocksize)
{
struct dax_device *dax_dev;
pgoff_t pgoff;
int err, id;
void *kaddr;
pfn_t pfn;
long len;
char buf[BDEVNAME_SIZE];
if (blocksize != PAGE_SIZE) {
pr_debug("%s: error: unsupported blocksize for dax\n",
bdevname(bdev, buf));
return -EINVAL;
}
err = bdev_dax_pgoff(bdev, 0, PAGE_SIZE, &pgoff);
if (err) {
pr_debug("%s: error: unaligned partition for dax\n",
bdevname(bdev, buf));
return err;
}
dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
if (!dax_dev) {
pr_debug("%s: error: device does not support dax\n",
bdevname(bdev, buf));
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_debug("%s: error: dax access failed (%ld)\n",
bdevname(bdev, buf), len);
return len < 0 ? len : -EIO;
}
if (IS_ENABLED(CONFIG_FS_DAX_LIMITED) && pfn_t_special(pfn)) {
/*
* An arch that has enabled the pmem api should also
* have its drivers support pfn_t_devmap()
*
* This is a developer warning and should not trigger in
* production. dax_flush() will crash since it depends
* on being able to do (page_address(pfn_to_page())).
*/
WARN_ON(IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API));
} else if (pfn_t_devmap(pfn)) {
/* pass */;
} else {
pr_debug("%s: error: dax support not enabled\n",
bdevname(bdev, buf));
return -EOPNOTSUPP;
}
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;
#ifndef CONFIG_ARCH_HAS_PMEM_API
if (a == &dev_attr_write_cache.attr)
return 0;
#endif
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;
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);
#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(!test_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags)))
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_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);
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_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);
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