1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2001 Sistina Software (UK) Limited
4 *
5 * This file is released under the GPL.
6 */
7
8#include "dm-core.h"
9
10#include <linux/module.h>
11#include <linux/init.h>
12#include <linux/kmod.h>
13#include <linux/bio.h>
14#include <linux/dax.h>
15
16#define DM_MSG_PREFIX "target"
17
18static LIST_HEAD(_targets);
19static DECLARE_RWSEM(_lock);
20
21static inline struct target_type *__find_target_type(const char *name)
22{
23	struct target_type *tt;
24
25	list_for_each_entry(tt, &_targets, list)
26		if (!strcmp(name, tt->name))
27			return tt;
28
29	return NULL;
30}
31
32static struct target_type *get_target_type(const char *name)
33{
34	struct target_type *tt;
35
36	down_read(&_lock);
37
38	tt = __find_target_type(name);
39	if (tt && !try_module_get(tt->module))
40		tt = NULL;
41
42	up_read(&_lock);
43	return tt;
44}
45
46static void load_module(const char *name)
47{
48	request_module("dm-%s", name);
49}
50
51struct target_type *dm_get_target_type(const char *name)
52{
53	struct target_type *tt = get_target_type(name);
54
55	if (!tt) {
56		load_module(name);
57		tt = get_target_type(name);
58	}
59
60	return tt;
61}
62
63void dm_put_target_type(struct target_type *tt)
64{
65	down_read(&_lock);
66	module_put(tt->module);
67	up_read(&_lock);
68}
69
70int dm_target_iterate(void (*iter_func)(struct target_type *tt,
71					void *param), void *param)
72{
73	struct target_type *tt;
74
75	down_read(&_lock);
76	list_for_each_entry(tt, &_targets, list)
77		iter_func(tt, param);
78	up_read(&_lock);
79
80	return 0;
81}
82
83int dm_register_target(struct target_type *tt)
84{
85	int rv = 0;
86
87	down_write(&_lock);
88	if (__find_target_type(tt->name)) {
89		DMERR("%s: '%s' target already registered",
90		      __func__, tt->name);
91		rv = -EEXIST;
92	} else {
93		list_add(&tt->list, &_targets);
94	}
95	up_write(&_lock);
96
97	return rv;
98}
99EXPORT_SYMBOL(dm_register_target);
100
101void dm_unregister_target(struct target_type *tt)
102{
103	down_write(&_lock);
104	if (!__find_target_type(tt->name)) {
105		DMCRIT("Unregistering unrecognised target: %s", tt->name);
106		BUG();
107	}
108
109	list_del(&tt->list);
110
111	up_write(&_lock);
112}
113EXPORT_SYMBOL(dm_unregister_target);
114
115/*
116 * io-err: always fails an io, useful for bringing
117 * up LVs that have holes in them.
118 */
119struct io_err_c {
120	struct dm_dev *dev;
121	sector_t start;
122};
123
124static int io_err_get_args(struct dm_target *tt, unsigned int argc, char **args)
125{
126	unsigned long long start;
127	struct io_err_c *ioec;
128	char dummy;
129	int ret;
130
131	ioec = kmalloc(sizeof(*ioec), GFP_KERNEL);
132	if (!ioec) {
133		tt->error = "Cannot allocate io_err context";
134		return -ENOMEM;
135	}
136
137	ret = -EINVAL;
138	if (sscanf(args[1], "%llu%c", &start, &dummy) != 1 ||
139	    start != (sector_t)start) {
140		tt->error = "Invalid device sector";
141		goto bad;
142	}
143	ioec->start = start;
144
145	ret = dm_get_device(tt, args[0], dm_table_get_mode(tt->table), &ioec->dev);
146	if (ret) {
147		tt->error = "Device lookup failed";
148		goto bad;
149	}
150
151	tt->private = ioec;
152
153	return 0;
154
155bad:
156	kfree(ioec);
157
158	return ret;
159}
160
161static int io_err_ctr(struct dm_target *tt, unsigned int argc, char **args)
162{
163	/*
164	 * If we have arguments, assume it is the path to the backing
165	 * block device and its mapping start sector (same as dm-linear).
166	 * In this case, get the device so that we can get its limits.
167	 */
168	if (argc == 2) {
169		int ret = io_err_get_args(tt, argc, args);
170
171		if (ret)
172			return ret;
173	}
174
175	/*
176	 * Return error for discards instead of -EOPNOTSUPP
177	 */
178	tt->num_discard_bios = 1;
179	tt->discards_supported = true;
180
181	return 0;
182}
183
184static void io_err_dtr(struct dm_target *tt)
185{
186	struct io_err_c *ioec = tt->private;
187
188	if (ioec) {
189		dm_put_device(tt, ioec->dev);
190		kfree(ioec);
191	}
192}
193
194static int io_err_map(struct dm_target *tt, struct bio *bio)
195{
196	return DM_MAPIO_KILL;
197}
198
199static int io_err_clone_and_map_rq(struct dm_target *ti, struct request *rq,
200				   union map_info *map_context,
201				   struct request **clone)
202{
203	return DM_MAPIO_KILL;
204}
205
206static void io_err_release_clone_rq(struct request *clone,
207				    union map_info *map_context)
208{
209}
210
211#ifdef CONFIG_BLK_DEV_ZONED
212static sector_t io_err_map_sector(struct dm_target *ti, sector_t bi_sector)
213{
214	struct io_err_c *ioec = ti->private;
215
216	return ioec->start + dm_target_offset(ti, bi_sector);
217}
218
219static int io_err_report_zones(struct dm_target *ti,
220		struct dm_report_zones_args *args, unsigned int nr_zones)
221{
222	struct io_err_c *ioec = ti->private;
223
224	/*
225	 * This should never be called when we do not have a backing device
226	 * as that mean the target is not a zoned one.
227	 */
228	if (WARN_ON_ONCE(!ioec))
229		return -EIO;
230
231	return dm_report_zones(ioec->dev->bdev, ioec->start,
232			       io_err_map_sector(ti, args->next_sector),
233			       args, nr_zones);
234}
235#else
236#define io_err_report_zones NULL
237#endif
238
239static int io_err_iterate_devices(struct dm_target *ti,
240				  iterate_devices_callout_fn fn, void *data)
241{
242	struct io_err_c *ioec = ti->private;
243
244	if (!ioec)
245		return 0;
246
247	return fn(ti, ioec->dev, ioec->start, ti->len, data);
248}
249
250static void io_err_io_hints(struct dm_target *ti, struct queue_limits *limits)
251{
252	limits->max_discard_sectors = UINT_MAX;
253	limits->max_hw_discard_sectors = UINT_MAX;
254	limits->discard_granularity = 512;
255}
256
257static long io_err_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
258		long nr_pages, enum dax_access_mode mode, void **kaddr,
259		pfn_t *pfn)
260{
261	return -EIO;
262}
263
264static struct target_type error_target = {
265	.name = "error",
266	.version = {1, 7, 0},
267	.features = DM_TARGET_WILDCARD | DM_TARGET_ZONED_HM,
268	.ctr  = io_err_ctr,
269	.dtr  = io_err_dtr,
270	.map  = io_err_map,
271	.clone_and_map_rq = io_err_clone_and_map_rq,
272	.release_clone_rq = io_err_release_clone_rq,
273	.iterate_devices = io_err_iterate_devices,
274	.io_hints = io_err_io_hints,
275	.direct_access = io_err_dax_direct_access,
276	.report_zones = io_err_report_zones,
277};
278
279int __init dm_target_init(void)
280{
281	return dm_register_target(&error_target);
282}
283
284void dm_target_exit(void)
285{
286	dm_unregister_target(&error_target);
287}
288