Root/drivers/md/persistent-data/dm-transaction-manager.c

1/*
2 * Copyright (C) 2011 Red Hat, Inc.
3 *
4 * This file is released under the GPL.
5 */
6#include "dm-transaction-manager.h"
7#include "dm-space-map.h"
8#include "dm-space-map-disk.h"
9#include "dm-space-map-metadata.h"
10#include "dm-persistent-data-internal.h"
11
12#include <linux/export.h>
13#include <linux/slab.h>
14#include <linux/device-mapper.h>
15
16#define DM_MSG_PREFIX "transaction manager"
17
18/*----------------------------------------------------------------*/
19
20struct shadow_info {
21    struct hlist_node hlist;
22    dm_block_t where;
23};
24
25/*
26 * It would be nice if we scaled with the size of transaction.
27 */
28#define HASH_SIZE 256
29#define HASH_MASK (HASH_SIZE - 1)
30
31struct dm_transaction_manager {
32    int is_clone;
33    struct dm_transaction_manager *real;
34
35    struct dm_block_manager *bm;
36    struct dm_space_map *sm;
37
38    spinlock_t lock;
39    struct hlist_head buckets[HASH_SIZE];
40};
41
42/*----------------------------------------------------------------*/
43
44static int is_shadow(struct dm_transaction_manager *tm, dm_block_t b)
45{
46    int r = 0;
47    unsigned bucket = dm_hash_block(b, HASH_MASK);
48    struct shadow_info *si;
49    struct hlist_node *n;
50
51    spin_lock(&tm->lock);
52    hlist_for_each_entry(si, n, tm->buckets + bucket, hlist)
53        if (si->where == b) {
54            r = 1;
55            break;
56        }
57    spin_unlock(&tm->lock);
58
59    return r;
60}
61
62/*
63 * This can silently fail if there's no memory. We're ok with this since
64 * creating redundant shadows causes no harm.
65 */
66static void insert_shadow(struct dm_transaction_manager *tm, dm_block_t b)
67{
68    unsigned bucket;
69    struct shadow_info *si;
70
71    si = kmalloc(sizeof(*si), GFP_NOIO);
72    if (si) {
73        si->where = b;
74        bucket = dm_hash_block(b, HASH_MASK);
75        spin_lock(&tm->lock);
76        hlist_add_head(&si->hlist, tm->buckets + bucket);
77        spin_unlock(&tm->lock);
78    }
79}
80
81static void wipe_shadow_table(struct dm_transaction_manager *tm)
82{
83    struct shadow_info *si;
84    struct hlist_node *n, *tmp;
85    struct hlist_head *bucket;
86    int i;
87
88    spin_lock(&tm->lock);
89    for (i = 0; i < HASH_SIZE; i++) {
90        bucket = tm->buckets + i;
91        hlist_for_each_entry_safe(si, n, tmp, bucket, hlist)
92            kfree(si);
93
94        INIT_HLIST_HEAD(bucket);
95    }
96
97    spin_unlock(&tm->lock);
98}
99
100/*----------------------------------------------------------------*/
101
102static struct dm_transaction_manager *dm_tm_create(struct dm_block_manager *bm,
103                           struct dm_space_map *sm)
104{
105    int i;
106    struct dm_transaction_manager *tm;
107
108    tm = kmalloc(sizeof(*tm), GFP_KERNEL);
109    if (!tm)
110        return ERR_PTR(-ENOMEM);
111
112    tm->is_clone = 0;
113    tm->real = NULL;
114    tm->bm = bm;
115    tm->sm = sm;
116
117    spin_lock_init(&tm->lock);
118    for (i = 0; i < HASH_SIZE; i++)
119        INIT_HLIST_HEAD(tm->buckets + i);
120
121    return tm;
122}
123
124struct dm_transaction_manager *dm_tm_create_non_blocking_clone(struct dm_transaction_manager *real)
125{
126    struct dm_transaction_manager *tm;
127
128    tm = kmalloc(sizeof(*tm), GFP_KERNEL);
129    if (tm) {
130        tm->is_clone = 1;
131        tm->real = real;
132    }
133
134    return tm;
135}
136EXPORT_SYMBOL_GPL(dm_tm_create_non_blocking_clone);
137
138void dm_tm_destroy(struct dm_transaction_manager *tm)
139{
140    if (!tm->is_clone)
141        wipe_shadow_table(tm);
142
143    kfree(tm);
144}
145EXPORT_SYMBOL_GPL(dm_tm_destroy);
146
147int dm_tm_pre_commit(struct dm_transaction_manager *tm)
148{
149    int r;
150
151    if (tm->is_clone)
152        return -EWOULDBLOCK;
153
154    r = dm_sm_commit(tm->sm);
155    if (r < 0)
156        return r;
157
158    return 0;
159}
160EXPORT_SYMBOL_GPL(dm_tm_pre_commit);
161
162int dm_tm_commit(struct dm_transaction_manager *tm, struct dm_block *root)
163{
164    if (tm->is_clone)
165        return -EWOULDBLOCK;
166
167    wipe_shadow_table(tm);
168
169    return dm_bm_flush_and_unlock(tm->bm, root);
170}
171EXPORT_SYMBOL_GPL(dm_tm_commit);
172
173int dm_tm_new_block(struct dm_transaction_manager *tm,
174            struct dm_block_validator *v,
175            struct dm_block **result)
176{
177    int r;
178    dm_block_t new_block;
179
180    if (tm->is_clone)
181        return -EWOULDBLOCK;
182
183    r = dm_sm_new_block(tm->sm, &new_block);
184    if (r < 0)
185        return r;
186
187    r = dm_bm_write_lock_zero(tm->bm, new_block, v, result);
188    if (r < 0) {
189        dm_sm_dec_block(tm->sm, new_block);
190        return r;
191    }
192
193    /*
194     * New blocks count as shadows in that they don't need to be
195     * shadowed again.
196     */
197    insert_shadow(tm, new_block);
198
199    return 0;
200}
201
202static int __shadow_block(struct dm_transaction_manager *tm, dm_block_t orig,
203              struct dm_block_validator *v,
204              struct dm_block **result)
205{
206    int r;
207    dm_block_t new;
208    struct dm_block *orig_block;
209
210    r = dm_sm_new_block(tm->sm, &new);
211    if (r < 0)
212        return r;
213
214    r = dm_sm_dec_block(tm->sm, orig);
215    if (r < 0)
216        return r;
217
218    r = dm_bm_read_lock(tm->bm, orig, v, &orig_block);
219    if (r < 0)
220        return r;
221
222    /*
223     * It would be tempting to use dm_bm_unlock_move here, but some
224     * code, such as the space maps, keeps using the old data structures
225     * secure in the knowledge they won't be changed until the next
226     * transaction. Using unlock_move would force a synchronous read
227     * since the old block would no longer be in the cache.
228     */
229    r = dm_bm_write_lock_zero(tm->bm, new, v, result);
230    if (r) {
231        dm_bm_unlock(orig_block);
232        return r;
233    }
234
235    memcpy(dm_block_data(*result), dm_block_data(orig_block),
236           dm_bm_block_size(tm->bm));
237
238    dm_bm_unlock(orig_block);
239    return r;
240}
241
242int dm_tm_shadow_block(struct dm_transaction_manager *tm, dm_block_t orig,
243               struct dm_block_validator *v, struct dm_block **result,
244               int *inc_children)
245{
246    int r;
247
248    if (tm->is_clone)
249        return -EWOULDBLOCK;
250
251    r = dm_sm_count_is_more_than_one(tm->sm, orig, inc_children);
252    if (r < 0)
253        return r;
254
255    if (is_shadow(tm, orig) && !*inc_children)
256        return dm_bm_write_lock(tm->bm, orig, v, result);
257
258    r = __shadow_block(tm, orig, v, result);
259    if (r < 0)
260        return r;
261    insert_shadow(tm, dm_block_location(*result));
262
263    return r;
264}
265EXPORT_SYMBOL_GPL(dm_tm_shadow_block);
266
267int dm_tm_read_lock(struct dm_transaction_manager *tm, dm_block_t b,
268            struct dm_block_validator *v,
269            struct dm_block **blk)
270{
271    if (tm->is_clone)
272        return dm_bm_read_try_lock(tm->real->bm, b, v, blk);
273
274    return dm_bm_read_lock(tm->bm, b, v, blk);
275}
276EXPORT_SYMBOL_GPL(dm_tm_read_lock);
277
278int dm_tm_unlock(struct dm_transaction_manager *tm, struct dm_block *b)
279{
280    return dm_bm_unlock(b);
281}
282EXPORT_SYMBOL_GPL(dm_tm_unlock);
283
284void dm_tm_inc(struct dm_transaction_manager *tm, dm_block_t b)
285{
286    /*
287     * The non-blocking clone doesn't support this.
288     */
289    BUG_ON(tm->is_clone);
290
291    dm_sm_inc_block(tm->sm, b);
292}
293EXPORT_SYMBOL_GPL(dm_tm_inc);
294
295void dm_tm_dec(struct dm_transaction_manager *tm, dm_block_t b)
296{
297    /*
298     * The non-blocking clone doesn't support this.
299     */
300    BUG_ON(tm->is_clone);
301
302    dm_sm_dec_block(tm->sm, b);
303}
304EXPORT_SYMBOL_GPL(dm_tm_dec);
305
306int dm_tm_ref(struct dm_transaction_manager *tm, dm_block_t b,
307          uint32_t *result)
308{
309    if (tm->is_clone)
310        return -EWOULDBLOCK;
311
312    return dm_sm_get_count(tm->sm, b, result);
313}
314
315struct dm_block_manager *dm_tm_get_bm(struct dm_transaction_manager *tm)
316{
317    return tm->bm;
318}
319
320/*----------------------------------------------------------------*/
321
322static int dm_tm_create_internal(struct dm_block_manager *bm,
323                 dm_block_t sb_location,
324                 struct dm_transaction_manager **tm,
325                 struct dm_space_map **sm,
326                 int create,
327                 void *sm_root, size_t sm_len)
328{
329    int r;
330
331    *sm = dm_sm_metadata_init();
332    if (IS_ERR(*sm))
333        return PTR_ERR(*sm);
334
335    *tm = dm_tm_create(bm, *sm);
336    if (IS_ERR(*tm)) {
337        dm_sm_destroy(*sm);
338        return PTR_ERR(*tm);
339    }
340
341    if (create) {
342        r = dm_sm_metadata_create(*sm, *tm, dm_bm_nr_blocks(bm),
343                      sb_location);
344        if (r) {
345            DMERR("couldn't create metadata space map");
346            goto bad;
347        }
348
349    } else {
350        r = dm_sm_metadata_open(*sm, *tm, sm_root, sm_len);
351        if (r) {
352            DMERR("couldn't open metadata space map");
353            goto bad;
354        }
355    }
356
357    return 0;
358
359bad:
360    dm_tm_destroy(*tm);
361    dm_sm_destroy(*sm);
362    return r;
363}
364
365int dm_tm_create_with_sm(struct dm_block_manager *bm, dm_block_t sb_location,
366             struct dm_transaction_manager **tm,
367             struct dm_space_map **sm)
368{
369    return dm_tm_create_internal(bm, sb_location, tm, sm, 1, NULL, 0);
370}
371EXPORT_SYMBOL_GPL(dm_tm_create_with_sm);
372
373int dm_tm_open_with_sm(struct dm_block_manager *bm, dm_block_t sb_location,
374               void *sm_root, size_t root_len,
375               struct dm_transaction_manager **tm,
376               struct dm_space_map **sm)
377{
378    return dm_tm_create_internal(bm, sb_location, tm, sm, 0, sm_root, root_len);
379}
380EXPORT_SYMBOL_GPL(dm_tm_open_with_sm);
381
382/*----------------------------------------------------------------*/
383

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