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// 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)
{
int ret;
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;
ret = dax_dev->ops->zero_page_range(dax_dev, pgoff, nr_pages);
return dax_mem2blk_err(ret);
}
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,
MF_MEM_PRE_REMOVE);
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);