2 * Copyright(c) 2017 Intel Corporation. All rights reserved.
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.
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.
13 #include <linux/pagemap.h>
14 #include <linux/module.h>
15 #include <linux/mount.h>
16 #include <linux/magic.h>
17 #include <linux/genhd.h>
18 #include <linux/cdev.h>
19 #include <linux/hash.h>
20 #include <linux/slab.h>
21 #include <linux/dax.h>
24 static dev_t dax_devt
;
25 DEFINE_STATIC_SRCU(dax_srcu
);
26 static struct vfsmount
*dax_mnt
;
27 static DEFINE_IDA(dax_minor_ida
);
28 static struct kmem_cache
*dax_cache __read_mostly
;
29 static struct super_block
*dax_superblock __read_mostly
;
31 #define DAX_HASH_SIZE (PAGE_SIZE / sizeof(struct hlist_head))
32 static struct hlist_head dax_host_list
[DAX_HASH_SIZE
];
33 static DEFINE_SPINLOCK(dax_host_lock
);
35 int dax_read_lock(void)
37 return srcu_read_lock(&dax_srcu
);
39 EXPORT_SYMBOL_GPL(dax_read_lock
);
41 void dax_read_unlock(int id
)
43 srcu_read_unlock(&dax_srcu
, id
);
45 EXPORT_SYMBOL_GPL(dax_read_unlock
);
47 int bdev_dax_pgoff(struct block_device
*bdev
, sector_t sector
, size_t size
,
50 phys_addr_t phys_off
= (get_start_sect(bdev
) + sector
) * 512;
53 *pgoff
= PHYS_PFN(phys_off
);
54 if (phys_off
% PAGE_SIZE
|| size
% PAGE_SIZE
)
58 EXPORT_SYMBOL(bdev_dax_pgoff
);
61 * __bdev_dax_supported() - Check if the device supports dax for filesystem
62 * @sb: The superblock of the device
63 * @blocksize: The block size of the device
65 * This is a library function for filesystems to check if the block device
66 * can be mounted with dax option.
68 * Return: negative errno if unsupported, 0 if supported.
70 int __bdev_dax_supported(struct super_block
*sb
, int blocksize
)
72 struct block_device
*bdev
= sb
->s_bdev
;
73 struct dax_device
*dax_dev
;
80 if (blocksize
!= PAGE_SIZE
) {
81 pr_err("VFS (%s): error: unsupported blocksize for dax\n",
86 err
= bdev_dax_pgoff(bdev
, 0, PAGE_SIZE
, &pgoff
);
88 pr_err("VFS (%s): error: unaligned partition for dax\n",
93 dax_dev
= dax_get_by_host(bdev
->bd_disk
->disk_name
);
95 pr_err("VFS (%s): error: device does not support dax\n",
100 id
= dax_read_lock();
101 len
= dax_direct_access(dax_dev
, pgoff
, 1, &kaddr
, &pfn
);
107 pr_err("VFS (%s): error: dax access failed (%ld)",
109 return len
< 0 ? len
: -EIO
;
114 EXPORT_SYMBOL_GPL(__bdev_dax_supported
);
117 * struct dax_device - anchor object for dax services
119 * @cdev: optional character interface for "device dax"
120 * @host: optional name for lookups where the device path is not available
121 * @private: dax driver private data
122 * @alive: !alive + rcu grace period == no new operations / mappings
125 struct hlist_node list
;
131 const struct dax_operations
*ops
;
135 * dax_direct_access() - translate a device pgoff to an absolute pfn
136 * @dax_dev: a dax_device instance representing the logical memory range
137 * @pgoff: offset in pages from the start of the device to translate
138 * @nr_pages: number of consecutive pages caller can handle relative to @pfn
139 * @kaddr: output parameter that returns a virtual address mapping of pfn
140 * @pfn: output parameter that returns an absolute pfn translation of @pgoff
142 * Return: negative errno if an error occurs, otherwise the number of
143 * pages accessible at the device relative @pgoff.
145 long dax_direct_access(struct dax_device
*dax_dev
, pgoff_t pgoff
, long nr_pages
,
146 void **kaddr
, pfn_t
*pfn
)
151 * The device driver is allowed to sleep, in order to make the
152 * memory directly accessible.
159 if (!dax_alive(dax_dev
))
165 avail
= dax_dev
->ops
->direct_access(dax_dev
, pgoff
, nr_pages
,
169 return min(avail
, nr_pages
);
171 EXPORT_SYMBOL_GPL(dax_direct_access
);
173 bool dax_alive(struct dax_device
*dax_dev
)
175 lockdep_assert_held(&dax_srcu
);
176 return dax_dev
->alive
;
178 EXPORT_SYMBOL_GPL(dax_alive
);
180 static int dax_host_hash(const char *host
)
182 return hashlen_hash(hashlen_string("DAX", host
)) % DAX_HASH_SIZE
;
186 * Note, rcu is not protecting the liveness of dax_dev, rcu is ensuring
187 * that any fault handlers or operations that might have seen
188 * dax_alive(), have completed. Any operations that start after
189 * synchronize_srcu() has run will abort upon seeing !dax_alive().
191 void kill_dax(struct dax_device
*dax_dev
)
196 dax_dev
->alive
= false;
198 synchronize_srcu(&dax_srcu
);
200 spin_lock(&dax_host_lock
);
201 hlist_del_init(&dax_dev
->list
);
202 spin_unlock(&dax_host_lock
);
204 dax_dev
->private = NULL
;
206 EXPORT_SYMBOL_GPL(kill_dax
);
208 static struct inode
*dax_alloc_inode(struct super_block
*sb
)
210 struct dax_device
*dax_dev
;
212 dax_dev
= kmem_cache_alloc(dax_cache
, GFP_KERNEL
);
213 return &dax_dev
->inode
;
216 static struct dax_device
*to_dax_dev(struct inode
*inode
)
218 return container_of(inode
, struct dax_device
, inode
);
221 static void dax_i_callback(struct rcu_head
*head
)
223 struct inode
*inode
= container_of(head
, struct inode
, i_rcu
);
224 struct dax_device
*dax_dev
= to_dax_dev(inode
);
226 kfree(dax_dev
->host
);
227 dax_dev
->host
= NULL
;
228 ida_simple_remove(&dax_minor_ida
, MINOR(inode
->i_rdev
));
229 kmem_cache_free(dax_cache
, dax_dev
);
232 static void dax_destroy_inode(struct inode
*inode
)
234 struct dax_device
*dax_dev
= to_dax_dev(inode
);
236 WARN_ONCE(dax_dev
->alive
,
237 "kill_dax() must be called before final iput()\n");
238 call_rcu(&inode
->i_rcu
, dax_i_callback
);
241 static const struct super_operations dax_sops
= {
242 .statfs
= simple_statfs
,
243 .alloc_inode
= dax_alloc_inode
,
244 .destroy_inode
= dax_destroy_inode
,
245 .drop_inode
= generic_delete_inode
,
248 static struct dentry
*dax_mount(struct file_system_type
*fs_type
,
249 int flags
, const char *dev_name
, void *data
)
251 return mount_pseudo(fs_type
, "dax:", &dax_sops
, NULL
, DAXFS_MAGIC
);
254 static struct file_system_type dax_fs_type
= {
257 .kill_sb
= kill_anon_super
,
260 static int dax_test(struct inode
*inode
, void *data
)
262 dev_t devt
= *(dev_t
*) data
;
264 return inode
->i_rdev
== devt
;
267 static int dax_set(struct inode
*inode
, void *data
)
269 dev_t devt
= *(dev_t
*) data
;
271 inode
->i_rdev
= devt
;
275 static struct dax_device
*dax_dev_get(dev_t devt
)
277 struct dax_device
*dax_dev
;
280 inode
= iget5_locked(dax_superblock
, hash_32(devt
+ DAXFS_MAGIC
, 31),
281 dax_test
, dax_set
, &devt
);
286 dax_dev
= to_dax_dev(inode
);
287 if (inode
->i_state
& I_NEW
) {
288 dax_dev
->alive
= true;
289 inode
->i_cdev
= &dax_dev
->cdev
;
290 inode
->i_mode
= S_IFCHR
;
291 inode
->i_flags
= S_DAX
;
292 mapping_set_gfp_mask(&inode
->i_data
, GFP_USER
);
293 unlock_new_inode(inode
);
299 static void dax_add_host(struct dax_device
*dax_dev
, const char *host
)
304 * Unconditionally init dax_dev since it's coming from a
305 * non-zeroed slab cache
307 INIT_HLIST_NODE(&dax_dev
->list
);
308 dax_dev
->host
= host
;
312 hash
= dax_host_hash(host
);
313 spin_lock(&dax_host_lock
);
314 hlist_add_head(&dax_dev
->list
, &dax_host_list
[hash
]);
315 spin_unlock(&dax_host_lock
);
318 struct dax_device
*alloc_dax(void *private, const char *__host
,
319 const struct dax_operations
*ops
)
321 struct dax_device
*dax_dev
;
326 host
= kstrdup(__host
, GFP_KERNEL
);
330 minor
= ida_simple_get(&dax_minor_ida
, 0, MINORMASK
+1, GFP_KERNEL
);
334 devt
= MKDEV(MAJOR(dax_devt
), minor
);
335 dax_dev
= dax_dev_get(devt
);
339 dax_add_host(dax_dev
, host
);
341 dax_dev
->private = private;
345 ida_simple_remove(&dax_minor_ida
, minor
);
350 EXPORT_SYMBOL_GPL(alloc_dax
);
352 void put_dax(struct dax_device
*dax_dev
)
356 iput(&dax_dev
->inode
);
358 EXPORT_SYMBOL_GPL(put_dax
);
361 * dax_get_by_host() - temporary lookup mechanism for filesystem-dax
362 * @host: alternate name for the device registered by a dax driver
364 struct dax_device
*dax_get_by_host(const char *host
)
366 struct dax_device
*dax_dev
, *found
= NULL
;
372 hash
= dax_host_hash(host
);
374 id
= dax_read_lock();
375 spin_lock(&dax_host_lock
);
376 hlist_for_each_entry(dax_dev
, &dax_host_list
[hash
], list
) {
377 if (!dax_alive(dax_dev
)
378 || strcmp(host
, dax_dev
->host
) != 0)
381 if (igrab(&dax_dev
->inode
))
385 spin_unlock(&dax_host_lock
);
390 EXPORT_SYMBOL_GPL(dax_get_by_host
);
393 * inode_dax: convert a public inode into its dax_dev
394 * @inode: An inode with i_cdev pointing to a dax_dev
396 * Note this is not equivalent to to_dax_dev() which is for private
397 * internal use where we know the inode filesystem type == dax_fs_type.
399 struct dax_device
*inode_dax(struct inode
*inode
)
401 struct cdev
*cdev
= inode
->i_cdev
;
403 return container_of(cdev
, struct dax_device
, cdev
);
405 EXPORT_SYMBOL_GPL(inode_dax
);
407 struct inode
*dax_inode(struct dax_device
*dax_dev
)
409 return &dax_dev
->inode
;
411 EXPORT_SYMBOL_GPL(dax_inode
);
413 void *dax_get_private(struct dax_device
*dax_dev
)
415 return dax_dev
->private;
417 EXPORT_SYMBOL_GPL(dax_get_private
);
419 static void init_once(void *_dax_dev
)
421 struct dax_device
*dax_dev
= _dax_dev
;
422 struct inode
*inode
= &dax_dev
->inode
;
424 inode_init_once(inode
);
427 static int __dax_fs_init(void)
431 dax_cache
= kmem_cache_create("dax_cache", sizeof(struct dax_device
), 0,
432 (SLAB_HWCACHE_ALIGN
|SLAB_RECLAIM_ACCOUNT
|
433 SLAB_MEM_SPREAD
|SLAB_ACCOUNT
),
438 rc
= register_filesystem(&dax_fs_type
);
440 goto err_register_fs
;
442 dax_mnt
= kern_mount(&dax_fs_type
);
443 if (IS_ERR(dax_mnt
)) {
444 rc
= PTR_ERR(dax_mnt
);
447 dax_superblock
= dax_mnt
->mnt_sb
;
452 unregister_filesystem(&dax_fs_type
);
454 kmem_cache_destroy(dax_cache
);
459 static void __dax_fs_exit(void)
461 kern_unmount(dax_mnt
);
462 unregister_filesystem(&dax_fs_type
);
463 kmem_cache_destroy(dax_cache
);
466 static int __init
dax_fs_init(void)
470 rc
= __dax_fs_init();
474 rc
= alloc_chrdev_region(&dax_devt
, 0, MINORMASK
+1, "dax");
480 static void __exit
dax_fs_exit(void)
482 unregister_chrdev_region(dax_devt
, MINORMASK
+1);
483 ida_destroy(&dax_minor_ida
);
487 MODULE_AUTHOR("Intel Corporation");
488 MODULE_LICENSE("GPL v2");
489 subsys_initcall(dax_fs_init
);
490 module_exit(dax_fs_exit
);