1 // SPDX-License-Identifier: GPL-2.0-or-later
2 #include "cache.h"
3 #include "backing_dev.h"
4 #include "cache_dev.h"
5 #include "dm_pcache.h"
6
7 /**
8 * cache_key_gc - Releases the reference of a cache key segment.
9 * @cache: Pointer to the pcache_cache structure.
10 * @key: Pointer to the cache key to be garbage collected.
11 *
12 * This function decrements the reference count of the cache segment
13 * associated with the given key. If the reference count drops to zero,
14 * the segment may be invalidated and reused.
15 */
cache_key_gc(struct pcache_cache * cache,struct pcache_cache_key * key)16 static void cache_key_gc(struct pcache_cache *cache, struct pcache_cache_key *key)
17 {
18 cache_seg_put(key->cache_pos.cache_seg);
19 }
20
need_gc(struct pcache_cache * cache,struct pcache_cache_pos * dirty_tail,struct pcache_cache_pos * key_tail)21 static bool need_gc(struct pcache_cache *cache, struct pcache_cache_pos *dirty_tail, struct pcache_cache_pos *key_tail)
22 {
23 struct dm_pcache *pcache = CACHE_TO_PCACHE(cache);
24 struct pcache_cache_kset_onmedia *kset_onmedia;
25 void *dirty_addr, *key_addr;
26 u32 segs_used, segs_gc_threshold, to_copy;
27 int ret;
28
29 dirty_addr = cache_pos_addr(dirty_tail);
30 key_addr = cache_pos_addr(key_tail);
31 if (dirty_addr == key_addr) {
32 pcache_dev_debug(pcache, "key tail is equal to dirty tail: %u:%u\n",
33 dirty_tail->cache_seg->cache_seg_id,
34 dirty_tail->seg_off);
35 return false;
36 }
37
38 kset_onmedia = (struct pcache_cache_kset_onmedia *)cache->gc_kset_onmedia_buf;
39
40 to_copy = min(PCACHE_KSET_ONMEDIA_SIZE_MAX, PCACHE_SEG_SIZE - key_tail->seg_off);
41 ret = copy_mc_to_kernel(kset_onmedia, key_addr, to_copy);
42 if (ret) {
43 pcache_dev_err(pcache, "error to read kset: %d", ret);
44 return false;
45 }
46
47 /* Check if kset_onmedia is corrupted */
48 if (kset_onmedia->magic != PCACHE_KSET_MAGIC) {
49 pcache_dev_debug(pcache, "gc error: magic is not as expected. key_tail: %u:%u magic: %llx, expected: %llx\n",
50 key_tail->cache_seg->cache_seg_id, key_tail->seg_off,
51 kset_onmedia->magic, PCACHE_KSET_MAGIC);
52 return false;
53 }
54
55 /* Verify the CRC of the kset_onmedia */
56 if (kset_onmedia->crc != cache_kset_crc(kset_onmedia)) {
57 pcache_dev_debug(pcache, "gc error: crc is not as expected. crc: %x, expected: %x\n",
58 cache_kset_crc(kset_onmedia), kset_onmedia->crc);
59 return false;
60 }
61
62 segs_used = bitmap_weight(cache->seg_map, cache->n_segs);
63 segs_gc_threshold = cache->n_segs * pcache_cache_get_gc_percent(cache) / 100;
64 if (segs_used < segs_gc_threshold) {
65 pcache_dev_debug(pcache, "segs_used: %u, segs_gc_threshold: %u\n", segs_used, segs_gc_threshold);
66 return false;
67 }
68
69 return true;
70 }
71
72 /**
73 * last_kset_gc - Advances the garbage collection for the last kset.
74 * @cache: Pointer to the pcache_cache structure.
75 * @kset_onmedia: Pointer to the kset_onmedia structure for the last kset.
76 */
last_kset_gc(struct pcache_cache * cache,struct pcache_cache_kset_onmedia * kset_onmedia)77 static void last_kset_gc(struct pcache_cache *cache, struct pcache_cache_kset_onmedia *kset_onmedia)
78 {
79 struct dm_pcache *pcache = CACHE_TO_PCACHE(cache);
80 struct pcache_cache_segment *cur_seg, *next_seg;
81
82 cur_seg = cache->key_tail.cache_seg;
83
84 next_seg = &cache->segments[kset_onmedia->next_cache_seg_id];
85
86 mutex_lock(&cache->key_tail_lock);
87 cache->key_tail.cache_seg = next_seg;
88 cache->key_tail.seg_off = 0;
89 cache_encode_key_tail(cache);
90 mutex_unlock(&cache->key_tail_lock);
91
92 pcache_dev_debug(pcache, "gc advance kset seg: %u\n", cur_seg->cache_seg_id);
93
94 spin_lock(&cache->seg_map_lock);
95 __clear_bit(cur_seg->cache_seg_id, cache->seg_map);
96 spin_unlock(&cache->seg_map_lock);
97 }
98
pcache_cache_gc_fn(struct work_struct * work)99 void pcache_cache_gc_fn(struct work_struct *work)
100 {
101 struct pcache_cache *cache = container_of(work, struct pcache_cache, gc_work.work);
102 struct dm_pcache *pcache = CACHE_TO_PCACHE(cache);
103 struct pcache_cache_pos dirty_tail, key_tail;
104 struct pcache_cache_kset_onmedia *kset_onmedia;
105 struct pcache_cache_key_onmedia *key_onmedia;
106 struct pcache_cache_key *key;
107 int ret;
108 int i;
109
110 kset_onmedia = (struct pcache_cache_kset_onmedia *)cache->gc_kset_onmedia_buf;
111
112 while (true) {
113 if (pcache_is_stopping(pcache) || atomic_read(&cache->gc_errors))
114 return;
115
116 /* Get new tail positions */
117 mutex_lock(&cache->dirty_tail_lock);
118 cache_pos_copy(&dirty_tail, &cache->dirty_tail);
119 mutex_unlock(&cache->dirty_tail_lock);
120
121 mutex_lock(&cache->key_tail_lock);
122 cache_pos_copy(&key_tail, &cache->key_tail);
123 mutex_unlock(&cache->key_tail_lock);
124
125 if (!need_gc(cache, &dirty_tail, &key_tail))
126 break;
127
128 if (kset_onmedia->flags & PCACHE_KSET_FLAGS_LAST) {
129 /* Don't move to the next segment if dirty_tail has not moved */
130 if (dirty_tail.cache_seg == key_tail.cache_seg)
131 break;
132
133 last_kset_gc(cache, kset_onmedia);
134 continue;
135 }
136
137 for (i = 0; i < kset_onmedia->key_num; i++) {
138 struct pcache_cache_key key_tmp = { 0 };
139
140 key_onmedia = &kset_onmedia->data[i];
141
142 key = &key_tmp;
143 cache_key_init(&cache->req_key_tree, key);
144
145 ret = cache_key_decode(cache, key_onmedia, key);
146 if (ret) {
147 /* return without re-arm gc work, and prevent future
148 * gc, because we can't retry the partial-gc-ed kset
149 */
150 atomic_inc(&cache->gc_errors);
151 pcache_dev_err(pcache, "failed to decode cache key in gc\n");
152 return;
153 }
154
155 cache_key_gc(cache, key);
156 }
157
158 pcache_dev_debug(pcache, "gc advance: %u:%u %u\n",
159 key_tail.cache_seg->cache_seg_id,
160 key_tail.seg_off,
161 get_kset_onmedia_size(kset_onmedia));
162
163 mutex_lock(&cache->key_tail_lock);
164 cache_pos_advance(&cache->key_tail, get_kset_onmedia_size(kset_onmedia));
165 cache_encode_key_tail(cache);
166 mutex_unlock(&cache->key_tail_lock);
167 }
168
169 queue_delayed_work(cache_get_wq(cache), &cache->gc_work, PCACHE_CACHE_GC_INTERVAL);
170 }
171