mm/backing-dev.c

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