mm/shrinker_debug.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/idr.h>
   3 #include <linux/slab.h>
   4 #include <linux/debugfs.h>
   5 #include <linux/seq_file.h>
   6 #include <linux/shrinker.h>
   7 #include <linux/memcontrol.h>
   8
   9 /* defined in vmscan.c */
  10 extern struct rw_semaphore shrinker_rwsem;
  11 extern struct list_head shrinker_list;
  12
  13 static DEFINE_IDA(shrinker_debugfs_ida);
  14 static struct dentry *shrinker_debugfs_root;
  15
  16 static unsigned long shrinker_count_objects(struct shrinker *shrinker,
  17                                             struct mem_cgroup *memcg,
  18                                             unsigned long *count_per_node)
  19 {
  20         unsigned long nr, total = 0;
  21         int nid;
  22
  23         for_each_node(nid) {
  24                 if (nid == 0 || (shrinker->flags & SHRINKER_NUMA_AWARE)) {
  25                         struct shrink_control sc = {
  26                                 .gfp_mask = GFP_KERNEL,
  27                                 .nid = nid,
  28                                 .memcg = memcg,
  29                         };
  30
  31                         nr = shrinker->count_objects(shrinker, &sc);
  32                         if (nr == SHRINK_EMPTY)
  33                                 nr = 0;
  34                 } else {
  35                         nr = 0;
  36                 }
  37
  38                 count_per_node[nid] = nr;
  39                 total += nr;
  40         }
  41
  42         return total;
  43 }
  44
  45 static int shrinker_debugfs_count_show(struct seq_file *m, void *v)
  46 {
  47         struct shrinker *shrinker = m->private;
  48         unsigned long *count_per_node;
  49         struct mem_cgroup *memcg;
  50         unsigned long total;
  51         bool memcg_aware;
  52         int ret, nid;
  53
  54         count_per_node = kcalloc(nr_node_ids, sizeof(unsigned long), GFP_KERNEL);
  55         if (!count_per_node)
  56                 return -ENOMEM;
  57
  58         ret = down_read_killable(&shrinker_rwsem);
  59         if (ret) {
  60                 kfree(count_per_node);
  61                 return ret;
  62         }
  63         rcu_read_lock();
  64
  65         memcg_aware = shrinker->flags & SHRINKER_MEMCG_AWARE;
  66
  67         memcg = mem_cgroup_iter(NULL, NULL, NULL);
  68         do {
  69                 if (memcg && !mem_cgroup_online(memcg))
  70                         continue;
  71
  72                 total = shrinker_count_objects(shrinker,
  73                                                memcg_aware ? memcg : NULL,
  74                                                count_per_node);
  75                 if (total) {
  76                         seq_printf(m, "%lu", mem_cgroup_ino(memcg));
  77                         for_each_node(nid)
  78                                 seq_printf(m, " %lu", count_per_node[nid]);
  79                         seq_putc(m, '\n');
  80                 }
  81
  82                 if (!memcg_aware) {
  83                         mem_cgroup_iter_break(NULL, memcg);
  84                         break;
  85                 }
  86
  87                 if (signal_pending(current)) {
  88                         mem_cgroup_iter_break(NULL, memcg);
  89                         ret = -EINTR;
  90                         break;
  91                 }
  92         } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
  93
  94         rcu_read_unlock();
  95         up_read(&shrinker_rwsem);
  96
  97         kfree(count_per_node);
  98         return ret;
  99 }
 100 DEFINE_SHOW_ATTRIBUTE(shrinker_debugfs_count);
 101
 102 static int shrinker_debugfs_scan_open(struct inode *inode, struct file *file)
 103 {
 104         file->private_data = inode->i_private;
 105         return nonseekable_open(inode, file);
 106 }
 107
 108 static ssize_t shrinker_debugfs_scan_write(struct file *file,
 109                                            const char __user *buf,
 110                                            size_t size, loff_t *pos)
 111 {
 112         struct shrinker *shrinker = file->private_data;
 113         unsigned long nr_to_scan = 0, ino, read_len;
 114         struct shrink_control sc = {
 115                 .gfp_mask = GFP_KERNEL,
 116         };
 117         struct mem_cgroup *memcg = NULL;
 118         int nid;
 119         char kbuf[72];
 120         ssize_t ret;
 121
 122         read_len = size < (sizeof(kbuf) - 1) ? size : (sizeof(kbuf) - 1);
 123         if (copy_from_user(kbuf, buf, read_len))
 124                 return -EFAULT;
 125         kbuf[read_len] = '\0';
 126
 127         if (sscanf(kbuf, "%lu %d %lu", &ino, &nid, &nr_to_scan) != 3)
 128                 return -EINVAL;
 129
 130         if (nid < 0 || nid >= nr_node_ids)
 131                 return -EINVAL;
 132
 133         if (nr_to_scan == 0)
 134                 return size;
 135
 136         if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
 137                 memcg = mem_cgroup_get_from_ino(ino);
 138                 if (!memcg || IS_ERR(memcg))
 139                         return -ENOENT;
 140
 141                 if (!mem_cgroup_online(memcg)) {
 142                         mem_cgroup_put(memcg);
 143                         return -ENOENT;
 144                 }
 145         } else if (ino != 0) {
 146                 return -EINVAL;
 147         }
 148
 149         ret = down_read_killable(&shrinker_rwsem);
 150         if (ret) {
 151                 mem_cgroup_put(memcg);
 152                 return ret;
 153         }
 154
 155         sc.nid = nid;
 156         sc.memcg = memcg;
 157         sc.nr_to_scan = nr_to_scan;
 158         sc.nr_scanned = nr_to_scan;
 159
 160         shrinker->scan_objects(shrinker, &sc);
 161
 162         up_read(&shrinker_rwsem);
 163         mem_cgroup_put(memcg);
 164
 165         return size;
 166 }
 167
 168 static const struct file_operations shrinker_debugfs_scan_fops = {
 169         .owner   = THIS_MODULE,
 170         .open    = shrinker_debugfs_scan_open,
 171         .write   = shrinker_debugfs_scan_write,
 172 };
 173
 174 int shrinker_debugfs_add(struct shrinker *shrinker)
 175 {
 176         struct dentry *entry;
 177         char buf[128];
 178         int id;
 179
 180         lockdep_assert_held(&shrinker_rwsem);
 181
 182         /* debugfs isn't initialized yet, add debugfs entries later. */
 183         if (!shrinker_debugfs_root)
 184                 return 0;
 185
 186         id = ida_alloc(&shrinker_debugfs_ida, GFP_KERNEL);
 187         if (id < 0)
 188                 return id;
 189         shrinker->debugfs_id = id;
 190
 191         snprintf(buf, sizeof(buf), "%s-%d", shrinker->name, id);
 192
 193         /* create debugfs entry */
 194         entry = debugfs_create_dir(buf, shrinker_debugfs_root);
 195         if (IS_ERR(entry)) {
 196                 ida_free(&shrinker_debugfs_ida, id);
 197                 return PTR_ERR(entry);
 198         }
 199         shrinker->debugfs_entry = entry;
 200
 201         debugfs_create_file("count", 0440, entry, shrinker,
 202                             &shrinker_debugfs_count_fops);
 203         debugfs_create_file("scan", 0220, entry, shrinker,
 204                             &shrinker_debugfs_scan_fops);
 205         return 0;
 206 }
 207
 208 int shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...)
 209 {
 210         struct dentry *entry;
 211         char buf[128];
 212         const char *new, *old;
 213         va_list ap;
 214         int ret = 0;
 215
 216         va_start(ap, fmt);
 217         new = kvasprintf_const(GFP_KERNEL, fmt, ap);
 218         va_end(ap);
 219
 220         if (!new)
 221                 return -ENOMEM;
 222
 223         down_write(&shrinker_rwsem);
 224
 225         old = shrinker->name;
 226         shrinker->name = new;
 227
 228         if (shrinker->debugfs_entry) {
 229                 snprintf(buf, sizeof(buf), "%s-%d", shrinker->name,
 230                          shrinker->debugfs_id);
 231
 232                 entry = debugfs_rename(shrinker_debugfs_root,
 233                                        shrinker->debugfs_entry,
 234                                        shrinker_debugfs_root, buf);
 235                 if (IS_ERR(entry))
 236                         ret = PTR_ERR(entry);
 237                 else
 238                         shrinker->debugfs_entry = entry;
 239         }
 240
 241         up_write(&shrinker_rwsem);
 242
 243         kfree_const(old);
 244
 245         return ret;
 246 }
 247 EXPORT_SYMBOL(shrinker_debugfs_rename);
 248
 249 struct dentry *shrinker_debugfs_detach(struct shrinker *shrinker,
 250                                        int *debugfs_id)
 251 {
 252         struct dentry *entry = shrinker->debugfs_entry;
 253
 254         lockdep_assert_held(&shrinker_rwsem);
 255
 256         kfree_const(shrinker->name);
 257         shrinker->name = NULL;
 258
 259         *debugfs_id = entry ? shrinker->debugfs_id : -1;
 260         shrinker->debugfs_entry = NULL;
 261
 262         return entry;
 263 }
 264
 265 void shrinker_debugfs_remove(struct dentry *debugfs_entry, int debugfs_id)
 266 {
 267         debugfs_remove_recursive(debugfs_entry);
 268         ida_free(&shrinker_debugfs_ida, debugfs_id);
 269 }
 270
 271 static int __init shrinker_debugfs_init(void)
 272 {
 273         struct shrinker *shrinker;
 274         struct dentry *dentry;
 275         int ret = 0;
 276
 277         dentry = debugfs_create_dir("shrinker", NULL);
 278         if (IS_ERR(dentry))
 279                 return PTR_ERR(dentry);
 280         shrinker_debugfs_root = dentry;
 281
 282         /* Create debugfs entries for shrinkers registered at boot */
 283         down_write(&shrinker_rwsem);
 284         list_for_each_entry(shrinker, &shrinker_list, list)
 285                 if (!shrinker->debugfs_entry) {
 286                         ret = shrinker_debugfs_add(shrinker);
 287                         if (ret)
 288                                 break;
 289                 }
 290         up_write(&shrinker_rwsem);
 291
 292         return ret;
 293 }
 294 late_initcall(shrinker_debugfs_init);