ClabureDB: Classified Bug-Reports Database

  
  #include <linux/wait.h>
  #include <linux/backing-dev.h>
  #include <linux/fs.h>
  #include <linux/sched.h>
  #include <linux/module.h>
  #include <linux/writeback.h>
  #include <linux/device.h>
  
 
 static struct class *bdi_class;
 
 #ifdef CONFIG_DEBUG_FS
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
 
 static struct dentry *bdi_debug_root;
 
 static void bdi_debug_init(void)
 {
         bdi_debug_root = debugfs_create_dir("bdi", NULL);
 }
 
 static int bdi_debug_stats_show(struct seq_file *m, void *v)
 {
         struct backing_dev_info *bdi = m->private;
         long background_thresh;
         long dirty_thresh;
         long bdi_thresh;
 
         get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi);
 
 #define K(x) ((x) << (PAGE_SHIFT - 10))
         seq_printf(m,
                    "BdiWriteback:     %8lu kB\n"
                    "BdiReclaimable:   %8lu kB\n"
                    "BdiDirtyThresh:   %8lu kB\n"
                    "DirtyThresh:      %8lu kB\n"
                    "BackgroundThresh: %8lu kB\n",
                    (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
                    (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
                    K(bdi_thresh),
                    K(dirty_thresh),
                    K(background_thresh));
 #undef K
 
         return 0;
 }
 
 static int bdi_debug_stats_open(struct inode *inode, struct file *file)
 {
         return single_open(file, bdi_debug_stats_show, inode->i_private);
 }
 
 static const struct file_operations bdi_debug_stats_fops = {
         .open                = bdi_debug_stats_open,
         .read                = seq_read,
         .llseek                = seq_lseek,
         .release        = single_release,
 };
 
 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
 {
         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
         bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
                                                bdi, &bdi_debug_stats_fops);
 }
 
 static void bdi_debug_unregister(struct backing_dev_info *bdi)
 {
         debugfs_remove(bdi->debug_stats);
         debugfs_remove(bdi->debug_dir);
 }
 #else
 static inline void bdi_debug_init(void)
 {
 }
 static inline void bdi_debug_register(struct backing_dev_info *bdi,
                                       const char *name)
 {
 }
 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
 {
 }
 #endif
 
 static ssize_t read_ahead_kb_store(struct device *dev,
                                   struct device_attribute *attr,
                                   const char *buf, size_t count)
 {
         struct backing_dev_info *bdi = dev_get_drvdata(dev);
         char *end;
         unsigned long read_ahead_kb;
         ssize_t ret = -EINVAL;
 
         read_ahead_kb = simple_strtoul(buf, &end, 10);
         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
                 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
                 ret = count;
        }
        return ret;
}

#define K(pages) ((pages) << (PAGE_SHIFT - 10))

#define BDI_SHOW(name, expr)                                                \
static ssize_t name##_show(struct device *dev,                                \
                           struct device_attribute *attr, char *page)        \
{                                                                        \
        struct backing_dev_info *bdi = dev_get_drvdata(dev);                \
                                                                        \
        return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);        \
}

BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))

static ssize_t min_ratio_store(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t count)
{
        struct backing_dev_info *bdi = dev_get_drvdata(dev);
        char *end;
        unsigned int ratio;
        ssize_t ret = -EINVAL;

        ratio = simple_strtoul(buf, &end, 10);
        if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
                ret = bdi_set_min_ratio(bdi, ratio);
                if (!ret)
                        ret = count;
        }
        return ret;
}
BDI_SHOW(min_ratio, bdi->min_ratio)

static ssize_t max_ratio_store(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t count)
{
        struct backing_dev_info *bdi = dev_get_drvdata(dev);
        char *end;
        unsigned int ratio;
        ssize_t ret = -EINVAL;

        ratio = simple_strtoul(buf, &end, 10);
        if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
                ret = bdi_set_max_ratio(bdi, ratio);
                if (!ret)
                        ret = count;
        }
        return ret;
}
BDI_SHOW(max_ratio, bdi->max_ratio)

#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)

static struct device_attribute bdi_dev_attrs[] = {
        __ATTR_RW(read_ahead_kb),
        __ATTR_RW(min_ratio),
        __ATTR_RW(max_ratio),
        __ATTR_NULL,
};

static __init int bdi_class_init(void)
{
        bdi_class = class_create(THIS_MODULE, "bdi");
        bdi_class->dev_attrs = bdi_dev_attrs;
        bdi_debug_init();
        return 0;
}

postcore_initcall(bdi_class_init);

int bdi_register(struct backing_dev_info *bdi, struct device *parent,
                const char *fmt, ...)
{
        va_list args;
        int ret = 0;
        struct device *dev;

        if (bdi->dev)        /* The driver needs to use separate queues per device */
                goto exit;

        va_start(args, fmt);
        dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
        va_end(args);
        if (IS_ERR(dev)) {
                ret = PTR_ERR(dev);
                goto exit;
        }

        bdi->dev = dev;
        bdi_debug_register(bdi, dev_name(dev));

exit:
        return ret;
}
EXPORT_SYMBOL(bdi_register);

int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
{
        return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
}
EXPORT_SYMBOL(bdi_register_dev);

void bdi_unregister(struct backing_dev_info *bdi)
{
        if (bdi->dev) {
                bdi_debug_unregister(bdi);
                device_unregister(bdi->dev);
                bdi->dev = NULL;
        }
}
EXPORT_SYMBOL(bdi_unregister);

int bdi_init(struct backing_dev_info *bdi)
{
        int i;
        int err;

        bdi->dev = NULL;

        bdi->min_ratio = 0;
        bdi->max_ratio = 100;
        bdi->max_prop_frac = PROP_FRAC_BASE;

        for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
                err = percpu_counter_init_irq(&bdi->bdi_stat[i], 0);
                if (err)
                        goto err;
        }

        bdi->dirty_exceeded = 0;
        err = prop_local_init_percpu(&bdi->completions);

        if (err) {
err:
                while (i--)
                        percpu_counter_destroy(&bdi->bdi_stat[i]);
        }

        return err;
}
EXPORT_SYMBOL(bdi_init);

void bdi_destroy(struct backing_dev_info *bdi)
{
        int i;

        bdi_unregister(bdi);

        for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
                percpu_counter_destroy(&bdi->bdi_stat[i]);

        prop_local_destroy_percpu(&bdi->completions);
}
EXPORT_SYMBOL(bdi_destroy);

static wait_queue_head_t congestion_wqh[2] = {
                __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
                __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
        };


void clear_bdi_congested(struct backing_dev_info *bdi, int rw)
{
        enum bdi_state bit;
        wait_queue_head_t *wqh = &congestion_wqh[rw];

        bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
        clear_bit(bit, &bdi->state);
        smp_mb__after_clear_bit();
        if (waitqueue_active(wqh))
                wake_up(wqh);
}
EXPORT_SYMBOL(clear_bdi_congested);

void set_bdi_congested(struct backing_dev_info *bdi, int rw)
{
        enum bdi_state bit;

        bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
        set_bit(bit, &bdi->state);
}
EXPORT_SYMBOL(set_bdi_congested);

/**
 * congestion_wait - wait for a backing_dev to become uncongested
 * @rw: READ or WRITE
 * @timeout: timeout in jiffies
 *
 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
 * write congestion.  If no backing_devs are congested then just wait for the
 * next write to be completed.
 */
long congestion_wait(int rw, long timeout)
{
        long ret;
        DEFINE_WAIT(wait);
        wait_queue_head_t *wqh = &congestion_wqh[rw];

        prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
        ret = io_schedule_timeout(timeout);
        finish_wait(wqh, &wait);
        return ret;
}
EXPORT_SYMBOL(congestion_wait);