mm/backing-dev.c

   1
   2 #include <linux/wait.h>
   3 #include <linux/backing-dev.h>
   4 #include <linux/fs.h>
   5 #include <linux/pagemap.h>
   6 #include <linux/sched.h>
   7 #include <linux/module.h>
   8 #include <linux/writeback.h>
   9 #include <linux/device.h>
  10
  11 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
  12 {
  13 }
  14 EXPORT_SYMBOL(default_unplug_io_fn);
  15
  16 struct backing_dev_info default_backing_dev_info = {
  17         .ra_pages       = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
  18         .state          = 0,
  19         .capabilities   = BDI_CAP_MAP_COPY,
  20         .unplug_io_fn   = default_unplug_io_fn,
  21 };
  22 EXPORT_SYMBOL_GPL(default_backing_dev_info);
  23
  24 static struct class *bdi_class;
  25
  26 #ifdef CONFIG_DEBUG_FS
  27 #include <linux/debugfs.h>
  28 #include <linux/seq_file.h>
  29
  30 static struct dentry *bdi_debug_root;
  31
  32 static void bdi_debug_init(void)
  33 {
  34         bdi_debug_root = debugfs_create_dir("bdi", NULL);
  35 }
  36
  37 static int bdi_debug_stats_show(struct seq_file *m, void *v)
  38 {
  39         struct backing_dev_info *bdi = m->private;
  40         unsigned long background_thresh;
  41         unsigned long dirty_thresh;
  42         unsigned long bdi_thresh;
  43
  44         get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi);
  45
  46 #define K(x) ((x) << (PAGE_SHIFT - 10))
  47         seq_printf(m,
  48                    "BdiWriteback:     %8lu kB\n"
  49                    "BdiReclaimable:   %8lu kB\n"
  50                    "BdiDirtyThresh:   %8lu kB\n"
  51                    "DirtyThresh:      %8lu kB\n"
  52                    "BackgroundThresh: %8lu kB\n",
  53                    (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
  54                    (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
  55                    K(bdi_thresh),
  56                    K(dirty_thresh),
  57                    K(background_thresh));
  58 #undef K
  59
  60         return 0;
  61 }
  62
  63 static int bdi_debug_stats_open(struct inode *inode, struct file *file)
  64 {
  65         return single_open(file, bdi_debug_stats_show, inode->i_private);
  66 }
  67
  68 static const struct file_operations bdi_debug_stats_fops = {
  69         .open           = bdi_debug_stats_open,
  70         .read           = seq_read,
  71         .llseek         = seq_lseek,
  72         .release        = single_release,
  73 };
  74
  75 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
  76 {
  77         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
  78         bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
  79                                                bdi, &bdi_debug_stats_fops);
  80 }
  81
  82 static void bdi_debug_unregister(struct backing_dev_info *bdi)
  83 {
  84         debugfs_remove(bdi->debug_stats);
  85         debugfs_remove(bdi->debug_dir);
  86 }
  87 #else
  88 static inline void bdi_debug_init(void)
  89 {
  90 }
  91 static inline void bdi_debug_register(struct backing_dev_info *bdi,
  92                                       const char *name)
  93 {
  94 }
  95 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
  96 {
  97 }
  98 #endif
  99
 100 static ssize_t read_ahead_kb_store(struct device *dev,
 101                                   struct device_attribute *attr,
 102                                   const char *buf, size_t count)
 103 {
 104         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 105         char *end;
 106         unsigned long read_ahead_kb;
 107         ssize_t ret = -EINVAL;
 108
 109         read_ahead_kb = simple_strtoul(buf, &end, 10);
 110         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
 111                 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
 112                 ret = count;
 113         }
 114         return ret;
 115 }
 116
 117 #define K(pages) ((pages) << (PAGE_SHIFT - 10))
 118
 119 #define BDI_SHOW(name, expr)                                            \
 120 static ssize_t name##_show(struct device *dev,                          \
 121                            struct device_attribute *attr, char *page)   \
 122 {                                                                       \
 123         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
 124                                                                         \
 125         return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);  \
 126 }
 127
 128 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
 129
 130 static ssize_t min_ratio_store(struct device *dev,
 131                 struct device_attribute *attr, const char *buf, size_t count)
 132 {
 133         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 134         char *end;
 135         unsigned int ratio;
 136         ssize_t ret = -EINVAL;
 137
 138         ratio = simple_strtoul(buf, &end, 10);
 139         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
 140                 ret = bdi_set_min_ratio(bdi, ratio);
 141                 if (!ret)
 142                         ret = count;
 143         }
 144         return ret;
 145 }
 146 BDI_SHOW(min_ratio, bdi->min_ratio)
 147
 148 static ssize_t max_ratio_store(struct device *dev,
 149                 struct device_attribute *attr, const char *buf, size_t count)
 150 {
 151         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 152         char *end;
 153         unsigned int ratio;
 154         ssize_t ret = -EINVAL;
 155
 156         ratio = simple_strtoul(buf, &end, 10);
 157         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
 158                 ret = bdi_set_max_ratio(bdi, ratio);
 159                 if (!ret)
 160                         ret = count;
 161         }
 162         return ret;
 163 }
 164 BDI_SHOW(max_ratio, bdi->max_ratio)
 165
 166 #define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
 167
 168 static struct device_attribute bdi_dev_attrs[] = {
 169         __ATTR_RW(read_ahead_kb),
 170         __ATTR_RW(min_ratio),
 171         __ATTR_RW(max_ratio),
 172         __ATTR_NULL,
 173 };
 174
 175 static __init int bdi_class_init(void)
 176 {
 177         bdi_class = class_create(THIS_MODULE, "bdi");
 178         bdi_class->dev_attrs = bdi_dev_attrs;
 179         bdi_debug_init();
 180         return 0;
 181 }
 182 postcore_initcall(bdi_class_init);
 183
 184 static int __init default_bdi_init(void)
 185 {
 186         int err;
 187
 188         err = bdi_init(&default_backing_dev_info);
 189         if (!err)
 190                 bdi_register(&default_backing_dev_info, NULL, "default");
 191
 192         return err;
 193 }
 194 subsys_initcall(default_bdi_init);
 195
 196 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 197                 const char *fmt, ...)
 198 {
 199         va_list args;
 200         int ret = 0;
 201         struct device *dev;
 202
 203         if (bdi->dev)   /* The driver needs to use separate queues per device */
 204                 goto exit;
 205
 206         va_start(args, fmt);
 207         dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
 208         va_end(args);
 209         if (IS_ERR(dev)) {
 210                 ret = PTR_ERR(dev);
 211                 goto exit;
 212         }
 213
 214         bdi->dev = dev;
 215         bdi_debug_register(bdi, dev_name(dev));
 216
 217 exit:
 218         return ret;
 219 }
 220 EXPORT_SYMBOL(bdi_register);
 221
 222 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
 223 {
 224         return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
 225 }
 226 EXPORT_SYMBOL(bdi_register_dev);
 227
 228 void bdi_unregister(struct backing_dev_info *bdi)
 229 {
 230         if (bdi->dev) {
 231                 bdi_debug_unregister(bdi);
 232                 device_unregister(bdi->dev);
 233                 bdi->dev = NULL;
 234         }
 235 }
 236 EXPORT_SYMBOL(bdi_unregister);
 237
 238 int bdi_init(struct backing_dev_info *bdi)
 239 {
 240         int i;
 241         int err;
 242
 243         bdi->dev = NULL;
 244
 245         bdi->min_ratio = 0;
 246         bdi->max_ratio = 100;
 247         bdi->max_prop_frac = PROP_FRAC_BASE;
 248
 249         for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
 250                 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
 251                 if (err)
 252                         goto err;
 253         }
 254
 255         bdi->dirty_exceeded = 0;
 256         err = prop_local_init_percpu(&bdi->completions);
 257
 258         if (err) {
 259 err:
 260                 while (i--)
 261                         percpu_counter_destroy(&bdi->bdi_stat[i]);
 262         }
 263
 264         return err;
 265 }
 266 EXPORT_SYMBOL(bdi_init);
 267
 268 void bdi_destroy(struct backing_dev_info *bdi)
 269 {
 270         int i;
 271
 272         bdi_unregister(bdi);
 273
 274         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
 275                 percpu_counter_destroy(&bdi->bdi_stat[i]);
 276
 277         prop_local_destroy_percpu(&bdi->completions);
 278 }
 279 EXPORT_SYMBOL(bdi_destroy);
 280
 281 static wait_queue_head_t congestion_wqh[2] = {
 282                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
 283                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
 284         };
 285
 286
 287 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
 288 {
 289         enum bdi_state bit;
 290         wait_queue_head_t *wqh = &congestion_wqh[sync];
 291
 292         bit = sync ? BDI_sync_congested : BDI_async_congested;
 293         clear_bit(bit, &bdi->state);
 294         smp_mb__after_clear_bit();
 295         if (waitqueue_active(wqh))
 296                 wake_up(wqh);
 297 }
 298 EXPORT_SYMBOL(clear_bdi_congested);
 299
 300 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
 301 {
 302         enum bdi_state bit;
 303
 304         bit = sync ? BDI_sync_congested : BDI_async_congested;
 305         set_bit(bit, &bdi->state);
 306 }
 307 EXPORT_SYMBOL(set_bdi_congested);
 308
 309 /**
 310  * congestion_wait - wait for a backing_dev to become uncongested
 311  * @rw: READ or WRITE
 312  * @timeout: timeout in jiffies
 313  *
 314  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
 315  * write congestion.  If no backing_devs are congested then just wait for the
 316  * next write to be completed.
 317  */
 318 long congestion_wait(int rw, long timeout)
 319 {
 320         long ret;
 321         DEFINE_WAIT(wait);
 322         wait_queue_head_t *wqh = &congestion_wqh[rw];
 323
 324         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
 325         ret = io_schedule_timeout(timeout);
 326         finish_wait(wqh, &wait);
 327         return ret;
 328 }
 329 EXPORT_SYMBOL(congestion_wait);
 330