1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2018 HUAWEI, Inc. 4 * https://www.huawei.com/ 5 */ 6 #include "internal.h" 7 8 struct page *erofs_allocpage(struct page **pagepool, gfp_t gfp) 9 { 10 struct page *page = *pagepool; 11 12 if (page) { 13 DBG_BUGON(page_ref_count(page) != 1); 14 *pagepool = (struct page *)page_private(page); 15 } else { 16 page = alloc_page(gfp); 17 } 18 return page; 19 } 20 21 void erofs_release_pages(struct page **pagepool) 22 { 23 while (*pagepool) { 24 struct page *page = *pagepool; 25 26 *pagepool = (struct page *)page_private(page); 27 put_page(page); 28 } 29 } 30 31 #ifdef CONFIG_EROFS_FS_ZIP 32 /* global shrink count (for all mounted EROFS instances) */ 33 static atomic_long_t erofs_global_shrink_cnt; 34 35 static bool erofs_workgroup_get(struct erofs_workgroup *grp) 36 { 37 if (lockref_get_not_zero(&grp->lockref)) 38 return true; 39 40 spin_lock(&grp->lockref.lock); 41 if (__lockref_is_dead(&grp->lockref)) { 42 spin_unlock(&grp->lockref.lock); 43 return false; 44 } 45 46 if (!grp->lockref.count++) 47 atomic_long_dec(&erofs_global_shrink_cnt); 48 spin_unlock(&grp->lockref.lock); 49 return true; 50 } 51 52 struct erofs_workgroup *erofs_find_workgroup(struct super_block *sb, 53 pgoff_t index) 54 { 55 struct erofs_sb_info *sbi = EROFS_SB(sb); 56 struct erofs_workgroup *grp; 57 58 repeat: 59 rcu_read_lock(); 60 grp = xa_load(&sbi->managed_pslots, index); 61 if (grp) { 62 if (!erofs_workgroup_get(grp)) { 63 /* prefer to relax rcu read side */ 64 rcu_read_unlock(); 65 goto repeat; 66 } 67 68 DBG_BUGON(index != grp->index); 69 } 70 rcu_read_unlock(); 71 return grp; 72 } 73 74 struct erofs_workgroup *erofs_insert_workgroup(struct super_block *sb, 75 struct erofs_workgroup *grp) 76 { 77 struct erofs_sb_info *const sbi = EROFS_SB(sb); 78 struct erofs_workgroup *pre; 79 80 /* 81 * Bump up before making this visible to others for the XArray in order 82 * to avoid potential UAF without serialized by xa_lock. 83 */ 84 lockref_get(&grp->lockref); 85 86 repeat: 87 xa_lock(&sbi->managed_pslots); 88 pre = __xa_cmpxchg(&sbi->managed_pslots, grp->index, 89 NULL, grp, GFP_NOFS); 90 if (pre) { 91 if (xa_is_err(pre)) { 92 pre = ERR_PTR(xa_err(pre)); 93 } else if (!erofs_workgroup_get(pre)) { 94 /* try to legitimize the current in-tree one */ 95 xa_unlock(&sbi->managed_pslots); 96 cond_resched(); 97 goto repeat; 98 } 99 lockref_put_return(&grp->lockref); 100 grp = pre; 101 } 102 xa_unlock(&sbi->managed_pslots); 103 return grp; 104 } 105 106 static void __erofs_workgroup_free(struct erofs_workgroup *grp) 107 { 108 atomic_long_dec(&erofs_global_shrink_cnt); 109 erofs_workgroup_free_rcu(grp); 110 } 111 112 void erofs_workgroup_put(struct erofs_workgroup *grp) 113 { 114 if (lockref_put_or_lock(&grp->lockref)) 115 return; 116 117 DBG_BUGON(__lockref_is_dead(&grp->lockref)); 118 if (grp->lockref.count == 1) 119 atomic_long_inc(&erofs_global_shrink_cnt); 120 --grp->lockref.count; 121 spin_unlock(&grp->lockref.lock); 122 } 123 124 static bool erofs_try_to_release_workgroup(struct erofs_sb_info *sbi, 125 struct erofs_workgroup *grp) 126 { 127 int free = false; 128 129 spin_lock(&grp->lockref.lock); 130 if (grp->lockref.count) 131 goto out; 132 133 /* 134 * Note that all cached pages should be detached before deleted from 135 * the XArray. Otherwise some cached pages could be still attached to 136 * the orphan old workgroup when the new one is available in the tree. 137 */ 138 if (erofs_try_to_free_all_cached_pages(sbi, grp)) 139 goto out; 140 141 /* 142 * It's impossible to fail after the workgroup is freezed, 143 * however in order to avoid some race conditions, add a 144 * DBG_BUGON to observe this in advance. 145 */ 146 DBG_BUGON(__xa_erase(&sbi->managed_pslots, grp->index) != grp); 147 148 lockref_mark_dead(&grp->lockref); 149 free = true; 150 out: 151 spin_unlock(&grp->lockref.lock); 152 if (free) 153 __erofs_workgroup_free(grp); 154 return free; 155 } 156 157 static unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi, 158 unsigned long nr_shrink) 159 { 160 struct erofs_workgroup *grp; 161 unsigned int freed = 0; 162 unsigned long index; 163 164 xa_lock(&sbi->managed_pslots); 165 xa_for_each(&sbi->managed_pslots, index, grp) { 166 /* try to shrink each valid workgroup */ 167 if (!erofs_try_to_release_workgroup(sbi, grp)) 168 continue; 169 xa_unlock(&sbi->managed_pslots); 170 171 ++freed; 172 if (!--nr_shrink) 173 return freed; 174 xa_lock(&sbi->managed_pslots); 175 } 176 xa_unlock(&sbi->managed_pslots); 177 return freed; 178 } 179 180 /* protected by 'erofs_sb_list_lock' */ 181 static unsigned int shrinker_run_no; 182 183 /* protects the mounted 'erofs_sb_list' */ 184 static DEFINE_SPINLOCK(erofs_sb_list_lock); 185 static LIST_HEAD(erofs_sb_list); 186 187 void erofs_shrinker_register(struct super_block *sb) 188 { 189 struct erofs_sb_info *sbi = EROFS_SB(sb); 190 191 mutex_init(&sbi->umount_mutex); 192 193 spin_lock(&erofs_sb_list_lock); 194 list_add(&sbi->list, &erofs_sb_list); 195 spin_unlock(&erofs_sb_list_lock); 196 } 197 198 void erofs_shrinker_unregister(struct super_block *sb) 199 { 200 struct erofs_sb_info *const sbi = EROFS_SB(sb); 201 202 mutex_lock(&sbi->umount_mutex); 203 /* clean up all remaining workgroups in memory */ 204 erofs_shrink_workstation(sbi, ~0UL); 205 206 spin_lock(&erofs_sb_list_lock); 207 list_del(&sbi->list); 208 spin_unlock(&erofs_sb_list_lock); 209 mutex_unlock(&sbi->umount_mutex); 210 } 211 212 static unsigned long erofs_shrink_count(struct shrinker *shrink, 213 struct shrink_control *sc) 214 { 215 return atomic_long_read(&erofs_global_shrink_cnt); 216 } 217 218 static unsigned long erofs_shrink_scan(struct shrinker *shrink, 219 struct shrink_control *sc) 220 { 221 struct erofs_sb_info *sbi; 222 struct list_head *p; 223 224 unsigned long nr = sc->nr_to_scan; 225 unsigned int run_no; 226 unsigned long freed = 0; 227 228 spin_lock(&erofs_sb_list_lock); 229 do { 230 run_no = ++shrinker_run_no; 231 } while (run_no == 0); 232 233 /* Iterate over all mounted superblocks and try to shrink them */ 234 p = erofs_sb_list.next; 235 while (p != &erofs_sb_list) { 236 sbi = list_entry(p, struct erofs_sb_info, list); 237 238 /* 239 * We move the ones we do to the end of the list, so we stop 240 * when we see one we have already done. 241 */ 242 if (sbi->shrinker_run_no == run_no) 243 break; 244 245 if (!mutex_trylock(&sbi->umount_mutex)) { 246 p = p->next; 247 continue; 248 } 249 250 spin_unlock(&erofs_sb_list_lock); 251 sbi->shrinker_run_no = run_no; 252 253 freed += erofs_shrink_workstation(sbi, nr - freed); 254 255 spin_lock(&erofs_sb_list_lock); 256 /* Get the next list element before we move this one */ 257 p = p->next; 258 259 /* 260 * Move this one to the end of the list to provide some 261 * fairness. 262 */ 263 list_move_tail(&sbi->list, &erofs_sb_list); 264 mutex_unlock(&sbi->umount_mutex); 265 266 if (freed >= nr) 267 break; 268 } 269 spin_unlock(&erofs_sb_list_lock); 270 return freed; 271 } 272 273 static struct shrinker erofs_shrinker_info = { 274 .scan_objects = erofs_shrink_scan, 275 .count_objects = erofs_shrink_count, 276 .seeks = DEFAULT_SEEKS, 277 }; 278 279 int __init erofs_init_shrinker(void) 280 { 281 return register_shrinker(&erofs_shrinker_info, "erofs-shrinker"); 282 } 283 284 void erofs_exit_shrinker(void) 285 { 286 unregister_shrinker(&erofs_shrinker_info); 287 } 288 #endif /* !CONFIG_EROFS_FS_ZIP */ 289