hlist: drop the node parameter from iterators
[linux-3.10.git] / drivers / md / dm-bio-prison.c
1 /*
2  * Copyright (C) 2012 Red Hat, Inc.
3  *
4  * This file is released under the GPL.
5  */
6
7 #include "dm.h"
8 #include "dm-bio-prison.h"
9
10 #include <linux/spinlock.h>
11 #include <linux/mempool.h>
12 #include <linux/module.h>
13 #include <linux/slab.h>
14
15 /*----------------------------------------------------------------*/
16
17 struct dm_bio_prison_cell {
18         struct hlist_node list;
19         struct dm_bio_prison *prison;
20         struct dm_cell_key key;
21         struct bio *holder;
22         struct bio_list bios;
23 };
24
25 struct dm_bio_prison {
26         spinlock_t lock;
27         mempool_t *cell_pool;
28
29         unsigned nr_buckets;
30         unsigned hash_mask;
31         struct hlist_head *cells;
32 };
33
34 /*----------------------------------------------------------------*/
35
36 static uint32_t calc_nr_buckets(unsigned nr_cells)
37 {
38         uint32_t n = 128;
39
40         nr_cells /= 4;
41         nr_cells = min(nr_cells, 8192u);
42
43         while (n < nr_cells)
44                 n <<= 1;
45
46         return n;
47 }
48
49 static struct kmem_cache *_cell_cache;
50
51 /*
52  * @nr_cells should be the number of cells you want in use _concurrently_.
53  * Don't confuse it with the number of distinct keys.
54  */
55 struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells)
56 {
57         unsigned i;
58         uint32_t nr_buckets = calc_nr_buckets(nr_cells);
59         size_t len = sizeof(struct dm_bio_prison) +
60                 (sizeof(struct hlist_head) * nr_buckets);
61         struct dm_bio_prison *prison = kmalloc(len, GFP_KERNEL);
62
63         if (!prison)
64                 return NULL;
65
66         spin_lock_init(&prison->lock);
67         prison->cell_pool = mempool_create_slab_pool(nr_cells, _cell_cache);
68         if (!prison->cell_pool) {
69                 kfree(prison);
70                 return NULL;
71         }
72
73         prison->nr_buckets = nr_buckets;
74         prison->hash_mask = nr_buckets - 1;
75         prison->cells = (struct hlist_head *) (prison + 1);
76         for (i = 0; i < nr_buckets; i++)
77                 INIT_HLIST_HEAD(prison->cells + i);
78
79         return prison;
80 }
81 EXPORT_SYMBOL_GPL(dm_bio_prison_create);
82
83 void dm_bio_prison_destroy(struct dm_bio_prison *prison)
84 {
85         mempool_destroy(prison->cell_pool);
86         kfree(prison);
87 }
88 EXPORT_SYMBOL_GPL(dm_bio_prison_destroy);
89
90 static uint32_t hash_key(struct dm_bio_prison *prison, struct dm_cell_key *key)
91 {
92         const unsigned long BIG_PRIME = 4294967291UL;
93         uint64_t hash = key->block * BIG_PRIME;
94
95         return (uint32_t) (hash & prison->hash_mask);
96 }
97
98 static int keys_equal(struct dm_cell_key *lhs, struct dm_cell_key *rhs)
99 {
100                return (lhs->virtual == rhs->virtual) &&
101                        (lhs->dev == rhs->dev) &&
102                        (lhs->block == rhs->block);
103 }
104
105 static struct dm_bio_prison_cell *__search_bucket(struct hlist_head *bucket,
106                                                   struct dm_cell_key *key)
107 {
108         struct dm_bio_prison_cell *cell;
109
110         hlist_for_each_entry(cell, bucket, list)
111                 if (keys_equal(&cell->key, key))
112                         return cell;
113
114         return NULL;
115 }
116
117 /*
118  * This may block if a new cell needs allocating.  You must ensure that
119  * cells will be unlocked even if the calling thread is blocked.
120  *
121  * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
122  */
123 int dm_bio_detain(struct dm_bio_prison *prison, struct dm_cell_key *key,
124                   struct bio *inmate, struct dm_bio_prison_cell **ref)
125 {
126         int r = 1;
127         unsigned long flags;
128         uint32_t hash = hash_key(prison, key);
129         struct dm_bio_prison_cell *cell, *cell2;
130
131         BUG_ON(hash > prison->nr_buckets);
132
133         spin_lock_irqsave(&prison->lock, flags);
134
135         cell = __search_bucket(prison->cells + hash, key);
136         if (cell) {
137                 bio_list_add(&cell->bios, inmate);
138                 goto out;
139         }
140
141         /*
142          * Allocate a new cell
143          */
144         spin_unlock_irqrestore(&prison->lock, flags);
145         cell2 = mempool_alloc(prison->cell_pool, GFP_NOIO);
146         spin_lock_irqsave(&prison->lock, flags);
147
148         /*
149          * We've been unlocked, so we have to double check that
150          * nobody else has inserted this cell in the meantime.
151          */
152         cell = __search_bucket(prison->cells + hash, key);
153         if (cell) {
154                 mempool_free(cell2, prison->cell_pool);
155                 bio_list_add(&cell->bios, inmate);
156                 goto out;
157         }
158
159         /*
160          * Use new cell.
161          */
162         cell = cell2;
163
164         cell->prison = prison;
165         memcpy(&cell->key, key, sizeof(cell->key));
166         cell->holder = inmate;
167         bio_list_init(&cell->bios);
168         hlist_add_head(&cell->list, prison->cells + hash);
169
170         r = 0;
171
172 out:
173         spin_unlock_irqrestore(&prison->lock, flags);
174
175         *ref = cell;
176
177         return r;
178 }
179 EXPORT_SYMBOL_GPL(dm_bio_detain);
180
181 /*
182  * @inmates must have been initialised prior to this call
183  */
184 static void __cell_release(struct dm_bio_prison_cell *cell, struct bio_list *inmates)
185 {
186         struct dm_bio_prison *prison = cell->prison;
187
188         hlist_del(&cell->list);
189
190         if (inmates) {
191                 bio_list_add(inmates, cell->holder);
192                 bio_list_merge(inmates, &cell->bios);
193         }
194
195         mempool_free(cell, prison->cell_pool);
196 }
197
198 void dm_cell_release(struct dm_bio_prison_cell *cell, struct bio_list *bios)
199 {
200         unsigned long flags;
201         struct dm_bio_prison *prison = cell->prison;
202
203         spin_lock_irqsave(&prison->lock, flags);
204         __cell_release(cell, bios);
205         spin_unlock_irqrestore(&prison->lock, flags);
206 }
207 EXPORT_SYMBOL_GPL(dm_cell_release);
208
209 /*
210  * Sometimes we don't want the holder, just the additional bios.
211  */
212 static void __cell_release_no_holder(struct dm_bio_prison_cell *cell, struct bio_list *inmates)
213 {
214         struct dm_bio_prison *prison = cell->prison;
215
216         hlist_del(&cell->list);
217         bio_list_merge(inmates, &cell->bios);
218
219         mempool_free(cell, prison->cell_pool);
220 }
221
222 void dm_cell_release_no_holder(struct dm_bio_prison_cell *cell, struct bio_list *inmates)
223 {
224         unsigned long flags;
225         struct dm_bio_prison *prison = cell->prison;
226
227         spin_lock_irqsave(&prison->lock, flags);
228         __cell_release_no_holder(cell, inmates);
229         spin_unlock_irqrestore(&prison->lock, flags);
230 }
231 EXPORT_SYMBOL_GPL(dm_cell_release_no_holder);
232
233 void dm_cell_error(struct dm_bio_prison_cell *cell)
234 {
235         struct dm_bio_prison *prison = cell->prison;
236         struct bio_list bios;
237         struct bio *bio;
238         unsigned long flags;
239
240         bio_list_init(&bios);
241
242         spin_lock_irqsave(&prison->lock, flags);
243         __cell_release(cell, &bios);
244         spin_unlock_irqrestore(&prison->lock, flags);
245
246         while ((bio = bio_list_pop(&bios)))
247                 bio_io_error(bio);
248 }
249 EXPORT_SYMBOL_GPL(dm_cell_error);
250
251 /*----------------------------------------------------------------*/
252
253 #define DEFERRED_SET_SIZE 64
254
255 struct dm_deferred_entry {
256         struct dm_deferred_set *ds;
257         unsigned count;
258         struct list_head work_items;
259 };
260
261 struct dm_deferred_set {
262         spinlock_t lock;
263         unsigned current_entry;
264         unsigned sweeper;
265         struct dm_deferred_entry entries[DEFERRED_SET_SIZE];
266 };
267
268 struct dm_deferred_set *dm_deferred_set_create(void)
269 {
270         int i;
271         struct dm_deferred_set *ds;
272
273         ds = kmalloc(sizeof(*ds), GFP_KERNEL);
274         if (!ds)
275                 return NULL;
276
277         spin_lock_init(&ds->lock);
278         ds->current_entry = 0;
279         ds->sweeper = 0;
280         for (i = 0; i < DEFERRED_SET_SIZE; i++) {
281                 ds->entries[i].ds = ds;
282                 ds->entries[i].count = 0;
283                 INIT_LIST_HEAD(&ds->entries[i].work_items);
284         }
285
286         return ds;
287 }
288 EXPORT_SYMBOL_GPL(dm_deferred_set_create);
289
290 void dm_deferred_set_destroy(struct dm_deferred_set *ds)
291 {
292         kfree(ds);
293 }
294 EXPORT_SYMBOL_GPL(dm_deferred_set_destroy);
295
296 struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds)
297 {
298         unsigned long flags;
299         struct dm_deferred_entry *entry;
300
301         spin_lock_irqsave(&ds->lock, flags);
302         entry = ds->entries + ds->current_entry;
303         entry->count++;
304         spin_unlock_irqrestore(&ds->lock, flags);
305
306         return entry;
307 }
308 EXPORT_SYMBOL_GPL(dm_deferred_entry_inc);
309
310 static unsigned ds_next(unsigned index)
311 {
312         return (index + 1) % DEFERRED_SET_SIZE;
313 }
314
315 static void __sweep(struct dm_deferred_set *ds, struct list_head *head)
316 {
317         while ((ds->sweeper != ds->current_entry) &&
318                !ds->entries[ds->sweeper].count) {
319                 list_splice_init(&ds->entries[ds->sweeper].work_items, head);
320                 ds->sweeper = ds_next(ds->sweeper);
321         }
322
323         if ((ds->sweeper == ds->current_entry) && !ds->entries[ds->sweeper].count)
324                 list_splice_init(&ds->entries[ds->sweeper].work_items, head);
325 }
326
327 void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head)
328 {
329         unsigned long flags;
330
331         spin_lock_irqsave(&entry->ds->lock, flags);
332         BUG_ON(!entry->count);
333         --entry->count;
334         __sweep(entry->ds, head);
335         spin_unlock_irqrestore(&entry->ds->lock, flags);
336 }
337 EXPORT_SYMBOL_GPL(dm_deferred_entry_dec);
338
339 /*
340  * Returns 1 if deferred or 0 if no pending items to delay job.
341  */
342 int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work)
343 {
344         int r = 1;
345         unsigned long flags;
346         unsigned next_entry;
347
348         spin_lock_irqsave(&ds->lock, flags);
349         if ((ds->sweeper == ds->current_entry) &&
350             !ds->entries[ds->current_entry].count)
351                 r = 0;
352         else {
353                 list_add(work, &ds->entries[ds->current_entry].work_items);
354                 next_entry = ds_next(ds->current_entry);
355                 if (!ds->entries[next_entry].count)
356                         ds->current_entry = next_entry;
357         }
358         spin_unlock_irqrestore(&ds->lock, flags);
359
360         return r;
361 }
362 EXPORT_SYMBOL_GPL(dm_deferred_set_add_work);
363
364 /*----------------------------------------------------------------*/
365
366 static int __init dm_bio_prison_init(void)
367 {
368         _cell_cache = KMEM_CACHE(dm_bio_prison_cell, 0);
369         if (!_cell_cache)
370                 return -ENOMEM;
371
372         return 0;
373 }
374
375 static void __exit dm_bio_prison_exit(void)
376 {
377         kmem_cache_destroy(_cell_cache);
378         _cell_cache = NULL;
379 }
380
381 /*
382  * module hooks
383  */
384 module_init(dm_bio_prison_init);
385 module_exit(dm_bio_prison_exit);
386
387 MODULE_DESCRIPTION(DM_NAME " bio prison");
388 MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
389 MODULE_LICENSE("GPL");