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