drivers/staging/erofs/utils.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * linux/drivers/staging/erofs/utils.c
   4  *
   5  * Copyright (C) 2018 HUAWEI, Inc.
   6  *             http://www.huawei.com/
   7  * Created by Gao Xiang <[email protected]>
   8  *
   9  * This file is subject to the terms and conditions of the GNU General Public
  10  * License.  See the file COPYING in the main directory of the Linux
  11  * distribution for more details.
  12  */
  13
  14 #include "internal.h"
  15 #include <linux/pagevec.h>
  16
  17 struct page *erofs_allocpage(struct list_head *pool, gfp_t gfp)
  18 {
  19         struct page *page;
  20
  21         if (!list_empty(pool)) {
  22                 page = lru_to_page(pool);
  23                 list_del(&page->lru);
  24         } else {
  25                 page = alloc_pages(gfp | __GFP_NOFAIL, 0);
  26
  27                 BUG_ON(page == NULL);
  28                 BUG_ON(page->mapping != NULL);
  29         }
  30         return page;
  31 }
  32
  33 /* global shrink count (for all mounted EROFS instances) */
  34 static atomic_long_t erofs_global_shrink_cnt;
  35
  36 #ifdef CONFIG_EROFS_FS_ZIP
  37
  38 struct erofs_workgroup *erofs_find_workgroup(
  39         struct super_block *sb, pgoff_t index, bool *tag)
  40 {
  41         struct erofs_sb_info *sbi = EROFS_SB(sb);
  42         struct erofs_workgroup *grp;
  43         int oldcount;
  44
  45 repeat:
  46         rcu_read_lock();
  47         grp = radix_tree_lookup(&sbi->workstn_tree, index);
  48         if (grp != NULL) {
  49                 *tag = xa_pointer_tag(grp);
  50                 grp = xa_untag_pointer(grp);
  51
  52                 if (erofs_workgroup_get(grp, &oldcount)) {
  53                         /* prefer to relax rcu read side */
  54                         rcu_read_unlock();
  55                         goto repeat;
  56                 }
  57
  58                 /* decrease refcount added by erofs_workgroup_put */
  59                 if (unlikely(oldcount == 1))
  60                         atomic_long_dec(&erofs_global_shrink_cnt);
  61                 BUG_ON(index != grp->index);
  62         }
  63         rcu_read_unlock();
  64         return grp;
  65 }
  66
  67 int erofs_register_workgroup(struct super_block *sb,
  68                              struct erofs_workgroup *grp,
  69                              bool tag)
  70 {
  71         struct erofs_sb_info *sbi;
  72         int err;
  73
  74         /* grp->refcount should not < 1 */
  75         BUG_ON(!atomic_read(&grp->refcount));
  76
  77         err = radix_tree_preload(GFP_NOFS);
  78         if (err)
  79                 return err;
  80
  81         sbi = EROFS_SB(sb);
  82         erofs_workstn_lock(sbi);
  83
  84         grp = xa_tag_pointer(grp, tag);
  85
  86         err = radix_tree_insert(&sbi->workstn_tree,
  87                 grp->index, grp);
  88
  89         if (!err) {
  90                 __erofs_workgroup_get(grp);
  91         }
  92
  93         erofs_workstn_unlock(sbi);
  94         radix_tree_preload_end();
  95         return err;
  96 }
  97
  98 extern void erofs_workgroup_free_rcu(struct erofs_workgroup *grp);
  99
 100 int erofs_workgroup_put(struct erofs_workgroup *grp)
 101 {
 102         int count = atomic_dec_return(&grp->refcount);
 103
 104         if (count == 1)
 105                 atomic_long_inc(&erofs_global_shrink_cnt);
 106         else if (!count) {
 107                 atomic_long_dec(&erofs_global_shrink_cnt);
 108                 erofs_workgroup_free_rcu(grp);
 109         }
 110         return count;
 111 }
 112
 113 unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi,
 114                                        unsigned long nr_shrink,
 115                                        bool cleanup)
 116 {
 117         pgoff_t first_index = 0;
 118         void *batch[PAGEVEC_SIZE];
 119         unsigned int freed = 0;
 120
 121         int i, found;
 122 repeat:
 123         erofs_workstn_lock(sbi);
 124
 125         found = radix_tree_gang_lookup(&sbi->workstn_tree,
 126                 batch, first_index, PAGEVEC_SIZE);
 127
 128         for (i = 0; i < found; ++i) {
 129                 int cnt;
 130                 struct erofs_workgroup *grp = xa_untag_pointer(batch[i]);
 131
 132                 first_index = grp->index + 1;
 133
 134                 cnt = atomic_read(&grp->refcount);
 135                 BUG_ON(cnt <= 0);
 136
 137                 if (cleanup)
 138                         BUG_ON(cnt != 1);
 139
 140 #ifndef EROFS_FS_HAS_MANAGED_CACHE
 141                 else if (cnt > 1)
 142 #else
 143                 if (!erofs_workgroup_try_to_freeze(grp, 1))
 144 #endif
 145                         continue;
 146
 147                 if (xa_untag_pointer(radix_tree_delete(&sbi->workstn_tree,
 148                         grp->index)) != grp) {
 149 #ifdef EROFS_FS_HAS_MANAGED_CACHE
 150 skip:
 151                         erofs_workgroup_unfreeze(grp, 1);
 152 #endif
 153                         continue;
 154                 }
 155
 156 #ifdef EROFS_FS_HAS_MANAGED_CACHE
 157                 if (erofs_try_to_free_all_cached_pages(sbi, grp))
 158                         goto skip;
 159
 160                 erofs_workgroup_unfreeze(grp, 1);
 161 #endif
 162                 /* (rarely) grabbed again when freeing */
 163                 erofs_workgroup_put(grp);
 164
 165                 ++freed;
 166                 if (unlikely(!--nr_shrink))
 167                         break;
 168         }
 169         erofs_workstn_unlock(sbi);
 170
 171         if (i && nr_shrink)
 172                 goto repeat;
 173         return freed;
 174 }
 175
 176 #endif
 177
 178 /* protected by 'erofs_sb_list_lock' */
 179 static unsigned int shrinker_run_no;
 180
 181 /* protects the mounted 'erofs_sb_list' */
 182 static DEFINE_SPINLOCK(erofs_sb_list_lock);
 183 static LIST_HEAD(erofs_sb_list);
 184
 185 void erofs_register_super(struct super_block *sb)
 186 {
 187         struct erofs_sb_info *sbi = EROFS_SB(sb);
 188
 189         mutex_init(&sbi->umount_mutex);
 190
 191         spin_lock(&erofs_sb_list_lock);
 192         list_add(&sbi->list, &erofs_sb_list);
 193         spin_unlock(&erofs_sb_list_lock);
 194 }
 195
 196 void erofs_unregister_super(struct super_block *sb)
 197 {
 198         spin_lock(&erofs_sb_list_lock);
 199         list_del(&EROFS_SB(sb)->list);
 200         spin_unlock(&erofs_sb_list_lock);
 201 }
 202
 203 unsigned long erofs_shrink_count(struct shrinker *shrink,
 204                                  struct shrink_control *sc)
 205 {
 206         return atomic_long_read(&erofs_global_shrink_cnt);
 207 }
 208
 209 unsigned long erofs_shrink_scan(struct shrinker *shrink,
 210                                 struct shrink_control *sc)
 211 {
 212         struct erofs_sb_info *sbi;
 213         struct list_head *p;
 214
 215         unsigned long nr = sc->nr_to_scan;
 216         unsigned int run_no;
 217         unsigned long freed = 0;
 218
 219         spin_lock(&erofs_sb_list_lock);
 220         do
 221                 run_no = ++shrinker_run_no;
 222         while (run_no == 0);
 223
 224         /* Iterate over all mounted superblocks and try to shrink them */
 225         p = erofs_sb_list.next;
 226         while (p != &erofs_sb_list) {
 227                 sbi = list_entry(p, struct erofs_sb_info, list);
 228
 229                 /*
 230                  * We move the ones we do to the end of the list, so we stop
 231                  * when we see one we have already done.
 232                  */
 233                 if (sbi->shrinker_run_no == run_no)
 234                         break;
 235
 236                 if (!mutex_trylock(&sbi->umount_mutex)) {
 237                         p = p->next;
 238                         continue;
 239                 }
 240
 241                 spin_unlock(&erofs_sb_list_lock);
 242                 sbi->shrinker_run_no = run_no;
 243
 244 #ifdef CONFIG_EROFS_FS_ZIP
 245                 freed += erofs_shrink_workstation(sbi, nr, false);
 246 #endif
 247
 248                 spin_lock(&erofs_sb_list_lock);
 249                 /* Get the next list element before we move this one */
 250                 p = p->next;
 251
 252                 /*
 253                  * Move this one to the end of the list to provide some
 254                  * fairness.
 255                  */
 256                 list_move_tail(&sbi->list, &erofs_sb_list);
 257                 mutex_unlock(&sbi->umount_mutex);
 258
 259                 if (freed >= nr)
 260                         break;
 261         }
 262         spin_unlock(&erofs_sb_list_lock);
 263         return freed;
 264 }
 265