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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/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
* @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,
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