![Jens Axboe](/assets/img/avatar_default.png)
Also a debugging aid. We want to catch dirty inodes being added to backing devices that don't do writeback. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
697 lines
16 KiB
C
697 lines
16 KiB
C
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#include <linux/wait.h>
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#include <linux/backing-dev.h>
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#include <linux/kthread.h>
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#include <linux/freezer.h>
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#include <linux/fs.h>
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#include <linux/pagemap.h>
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#include <linux/mm.h>
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#include <linux/sched.h>
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#include <linux/module.h>
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#include <linux/writeback.h>
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#include <linux/device.h>
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void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
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{
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}
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EXPORT_SYMBOL(default_unplug_io_fn);
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struct backing_dev_info default_backing_dev_info = {
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.name = "default",
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.ra_pages = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
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.state = 0,
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.capabilities = BDI_CAP_MAP_COPY,
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.unplug_io_fn = default_unplug_io_fn,
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};
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EXPORT_SYMBOL_GPL(default_backing_dev_info);
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static struct class *bdi_class;
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DEFINE_SPINLOCK(bdi_lock);
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LIST_HEAD(bdi_list);
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LIST_HEAD(bdi_pending_list);
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static struct task_struct *sync_supers_tsk;
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static struct timer_list sync_supers_timer;
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static int bdi_sync_supers(void *);
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static void sync_supers_timer_fn(unsigned long);
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static void arm_supers_timer(void);
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static void bdi_add_default_flusher_task(struct backing_dev_info *bdi);
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#ifdef CONFIG_DEBUG_FS
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#include <linux/debugfs.h>
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#include <linux/seq_file.h>
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static struct dentry *bdi_debug_root;
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static void bdi_debug_init(void)
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{
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bdi_debug_root = debugfs_create_dir("bdi", NULL);
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}
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static int bdi_debug_stats_show(struct seq_file *m, void *v)
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{
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struct backing_dev_info *bdi = m->private;
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struct bdi_writeback *wb;
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unsigned long background_thresh;
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unsigned long dirty_thresh;
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unsigned long bdi_thresh;
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unsigned long nr_dirty, nr_io, nr_more_io, nr_wb;
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struct inode *inode;
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/*
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* inode lock is enough here, the bdi->wb_list is protected by
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* RCU on the reader side
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*/
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nr_wb = nr_dirty = nr_io = nr_more_io = 0;
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spin_lock(&inode_lock);
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list_for_each_entry(wb, &bdi->wb_list, list) {
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nr_wb++;
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list_for_each_entry(inode, &wb->b_dirty, i_list)
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nr_dirty++;
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list_for_each_entry(inode, &wb->b_io, i_list)
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nr_io++;
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list_for_each_entry(inode, &wb->b_more_io, i_list)
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nr_more_io++;
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}
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spin_unlock(&inode_lock);
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get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi);
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#define K(x) ((x) << (PAGE_SHIFT - 10))
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seq_printf(m,
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"BdiWriteback: %8lu kB\n"
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"BdiReclaimable: %8lu kB\n"
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"BdiDirtyThresh: %8lu kB\n"
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"DirtyThresh: %8lu kB\n"
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"BackgroundThresh: %8lu kB\n"
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"WriteBack threads:%8lu\n"
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"b_dirty: %8lu\n"
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"b_io: %8lu\n"
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"b_more_io: %8lu\n"
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"bdi_list: %8u\n"
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"state: %8lx\n"
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"wb_mask: %8lx\n"
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"wb_list: %8u\n"
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"wb_cnt: %8u\n",
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(unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
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(unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
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K(bdi_thresh), K(dirty_thresh),
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K(background_thresh), nr_wb, nr_dirty, nr_io, nr_more_io,
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!list_empty(&bdi->bdi_list), bdi->state, bdi->wb_mask,
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!list_empty(&bdi->wb_list), bdi->wb_cnt);
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#undef K
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return 0;
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}
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static int bdi_debug_stats_open(struct inode *inode, struct file *file)
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{
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return single_open(file, bdi_debug_stats_show, inode->i_private);
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}
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static const struct file_operations bdi_debug_stats_fops = {
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.open = bdi_debug_stats_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = single_release,
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};
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static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
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{
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bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
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bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
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bdi, &bdi_debug_stats_fops);
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}
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static void bdi_debug_unregister(struct backing_dev_info *bdi)
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{
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debugfs_remove(bdi->debug_stats);
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debugfs_remove(bdi->debug_dir);
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}
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#else
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static inline void bdi_debug_init(void)
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{
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}
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static inline void bdi_debug_register(struct backing_dev_info *bdi,
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const char *name)
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{
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}
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static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
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{
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}
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#endif
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static ssize_t read_ahead_kb_store(struct device *dev,
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struct device_attribute *attr,
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const char *buf, size_t count)
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{
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struct backing_dev_info *bdi = dev_get_drvdata(dev);
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char *end;
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unsigned long read_ahead_kb;
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ssize_t ret = -EINVAL;
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read_ahead_kb = simple_strtoul(buf, &end, 10);
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if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
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bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
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ret = count;
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}
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return ret;
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}
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#define K(pages) ((pages) << (PAGE_SHIFT - 10))
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#define BDI_SHOW(name, expr) \
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static ssize_t name##_show(struct device *dev, \
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struct device_attribute *attr, char *page) \
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{ \
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struct backing_dev_info *bdi = dev_get_drvdata(dev); \
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\
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return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \
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}
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BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
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static ssize_t min_ratio_store(struct device *dev,
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struct device_attribute *attr, const char *buf, size_t count)
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{
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struct backing_dev_info *bdi = dev_get_drvdata(dev);
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char *end;
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unsigned int ratio;
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ssize_t ret = -EINVAL;
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ratio = simple_strtoul(buf, &end, 10);
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if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
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ret = bdi_set_min_ratio(bdi, ratio);
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if (!ret)
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ret = count;
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}
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return ret;
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}
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BDI_SHOW(min_ratio, bdi->min_ratio)
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static ssize_t max_ratio_store(struct device *dev,
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struct device_attribute *attr, const char *buf, size_t count)
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{
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struct backing_dev_info *bdi = dev_get_drvdata(dev);
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char *end;
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unsigned int ratio;
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ssize_t ret = -EINVAL;
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ratio = simple_strtoul(buf, &end, 10);
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if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
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ret = bdi_set_max_ratio(bdi, ratio);
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if (!ret)
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ret = count;
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}
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return ret;
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}
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BDI_SHOW(max_ratio, bdi->max_ratio)
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#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
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static struct device_attribute bdi_dev_attrs[] = {
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__ATTR_RW(read_ahead_kb),
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__ATTR_RW(min_ratio),
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__ATTR_RW(max_ratio),
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__ATTR_NULL,
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};
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static __init int bdi_class_init(void)
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{
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bdi_class = class_create(THIS_MODULE, "bdi");
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bdi_class->dev_attrs = bdi_dev_attrs;
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bdi_debug_init();
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return 0;
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}
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postcore_initcall(bdi_class_init);
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static int __init default_bdi_init(void)
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{
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int err;
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sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers");
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BUG_ON(IS_ERR(sync_supers_tsk));
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init_timer(&sync_supers_timer);
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setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0);
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arm_supers_timer();
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err = bdi_init(&default_backing_dev_info);
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if (!err)
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bdi_register(&default_backing_dev_info, NULL, "default");
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return err;
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}
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subsys_initcall(default_bdi_init);
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static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
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{
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memset(wb, 0, sizeof(*wb));
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wb->bdi = bdi;
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wb->last_old_flush = jiffies;
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INIT_LIST_HEAD(&wb->b_dirty);
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INIT_LIST_HEAD(&wb->b_io);
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INIT_LIST_HEAD(&wb->b_more_io);
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}
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static void bdi_task_init(struct backing_dev_info *bdi,
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struct bdi_writeback *wb)
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{
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struct task_struct *tsk = current;
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spin_lock(&bdi->wb_lock);
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list_add_tail_rcu(&wb->list, &bdi->wb_list);
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spin_unlock(&bdi->wb_lock);
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tsk->flags |= PF_FLUSHER | PF_SWAPWRITE;
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set_freezable();
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/*
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* Our parent may run at a different priority, just set us to normal
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*/
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set_user_nice(tsk, 0);
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}
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static int bdi_start_fn(void *ptr)
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{
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struct bdi_writeback *wb = ptr;
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struct backing_dev_info *bdi = wb->bdi;
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int ret;
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/*
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* Add us to the active bdi_list
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*/
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spin_lock(&bdi_lock);
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list_add(&bdi->bdi_list, &bdi_list);
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spin_unlock(&bdi_lock);
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bdi_task_init(bdi, wb);
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/*
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* Clear pending bit and wakeup anybody waiting to tear us down
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*/
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clear_bit(BDI_pending, &bdi->state);
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smp_mb__after_clear_bit();
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wake_up_bit(&bdi->state, BDI_pending);
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ret = bdi_writeback_task(wb);
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/*
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* Remove us from the list
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*/
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spin_lock(&bdi->wb_lock);
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list_del_rcu(&wb->list);
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spin_unlock(&bdi->wb_lock);
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/*
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* Flush any work that raced with us exiting. No new work
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* will be added, since this bdi isn't discoverable anymore.
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*/
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if (!list_empty(&bdi->work_list))
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wb_do_writeback(wb, 1);
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wb->task = NULL;
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return ret;
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}
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int bdi_has_dirty_io(struct backing_dev_info *bdi)
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{
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return wb_has_dirty_io(&bdi->wb);
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}
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static void bdi_flush_io(struct backing_dev_info *bdi)
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{
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struct writeback_control wbc = {
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.bdi = bdi,
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.sync_mode = WB_SYNC_NONE,
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.older_than_this = NULL,
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.range_cyclic = 1,
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.nr_to_write = 1024,
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};
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writeback_inodes_wbc(&wbc);
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}
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/*
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* kupdated() used to do this. We cannot do it from the bdi_forker_task()
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* or we risk deadlocking on ->s_umount. The longer term solution would be
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* to implement sync_supers_bdi() or similar and simply do it from the
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* bdi writeback tasks individually.
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*/
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static int bdi_sync_supers(void *unused)
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{
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set_user_nice(current, 0);
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while (!kthread_should_stop()) {
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set_current_state(TASK_INTERRUPTIBLE);
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schedule();
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/*
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* Do this periodically, like kupdated() did before.
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*/
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sync_supers();
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}
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return 0;
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}
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static void arm_supers_timer(void)
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{
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unsigned long next;
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next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies;
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mod_timer(&sync_supers_timer, round_jiffies_up(next));
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}
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static void sync_supers_timer_fn(unsigned long unused)
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{
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wake_up_process(sync_supers_tsk);
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arm_supers_timer();
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}
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static int bdi_forker_task(void *ptr)
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{
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struct bdi_writeback *me = ptr;
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bdi_task_init(me->bdi, me);
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for (;;) {
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struct backing_dev_info *bdi, *tmp;
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struct bdi_writeback *wb;
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/*
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* Temporary measure, we want to make sure we don't see
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* dirty data on the default backing_dev_info
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*/
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if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list))
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wb_do_writeback(me, 0);
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spin_lock(&bdi_lock);
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/*
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* Check if any existing bdi's have dirty data without
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* a thread registered. If so, set that up.
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*/
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list_for_each_entry_safe(bdi, tmp, &bdi_list, bdi_list) {
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if (bdi->wb.task)
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continue;
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if (list_empty(&bdi->work_list) &&
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!bdi_has_dirty_io(bdi))
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continue;
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bdi_add_default_flusher_task(bdi);
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}
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set_current_state(TASK_INTERRUPTIBLE);
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if (list_empty(&bdi_pending_list)) {
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unsigned long wait;
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spin_unlock(&bdi_lock);
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wait = msecs_to_jiffies(dirty_writeback_interval * 10);
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schedule_timeout(wait);
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try_to_freeze();
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continue;
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}
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__set_current_state(TASK_RUNNING);
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/*
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* This is our real job - check for pending entries in
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* bdi_pending_list, and create the tasks that got added
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*/
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bdi = list_entry(bdi_pending_list.next, struct backing_dev_info,
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bdi_list);
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list_del_init(&bdi->bdi_list);
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spin_unlock(&bdi_lock);
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wb = &bdi->wb;
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wb->task = kthread_run(bdi_start_fn, wb, "flush-%s",
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dev_name(bdi->dev));
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/*
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* If task creation fails, then readd the bdi to
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* the pending list and force writeout of the bdi
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* from this forker thread. That will free some memory
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* and we can try again.
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*/
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if (IS_ERR(wb->task)) {
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wb->task = NULL;
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/*
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* Add this 'bdi' to the back, so we get
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* a chance to flush other bdi's to free
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* memory.
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*/
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spin_lock(&bdi_lock);
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list_add_tail(&bdi->bdi_list, &bdi_pending_list);
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spin_unlock(&bdi_lock);
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bdi_flush_io(bdi);
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}
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}
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return 0;
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}
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/*
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* Add the default flusher task that gets created for any bdi
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* that has dirty data pending writeout
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*/
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void static bdi_add_default_flusher_task(struct backing_dev_info *bdi)
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{
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if (!bdi_cap_writeback_dirty(bdi))
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return;
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if (WARN_ON(!test_bit(BDI_registered, &bdi->state))) {
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printk(KERN_ERR "bdi %p/%s is not registered!\n",
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bdi, bdi->name);
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return;
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}
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/*
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* Check with the helper whether to proceed adding a task. Will only
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* abort if we two or more simultanous calls to
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* bdi_add_default_flusher_task() occured, further additions will block
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* waiting for previous additions to finish.
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*/
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if (!test_and_set_bit(BDI_pending, &bdi->state)) {
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list_move_tail(&bdi->bdi_list, &bdi_pending_list);
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/*
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* We are now on the pending list, wake up bdi_forker_task()
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* to finish the job and add us back to the active bdi_list
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*/
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wake_up_process(default_backing_dev_info.wb.task);
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}
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}
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int bdi_register(struct backing_dev_info *bdi, struct device *parent,
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const char *fmt, ...)
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{
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va_list args;
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int ret = 0;
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struct device *dev;
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if (bdi->dev) /* The driver needs to use separate queues per device */
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goto exit;
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va_start(args, fmt);
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dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
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va_end(args);
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if (IS_ERR(dev)) {
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ret = PTR_ERR(dev);
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goto exit;
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}
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spin_lock(&bdi_lock);
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|
list_add_tail(&bdi->bdi_list, &bdi_list);
|
|
spin_unlock(&bdi_lock);
|
|
|
|
bdi->dev = dev;
|
|
|
|
/*
|
|
* Just start the forker thread for our default backing_dev_info,
|
|
* and add other bdi's to the list. They will get a thread created
|
|
* on-demand when they need it.
|
|
*/
|
|
if (bdi_cap_flush_forker(bdi)) {
|
|
struct bdi_writeback *wb = &bdi->wb;
|
|
|
|
wb->task = kthread_run(bdi_forker_task, wb, "bdi-%s",
|
|
dev_name(dev));
|
|
if (IS_ERR(wb->task)) {
|
|
wb->task = NULL;
|
|
ret = -ENOMEM;
|
|
|
|
spin_lock(&bdi_lock);
|
|
list_del(&bdi->bdi_list);
|
|
spin_unlock(&bdi_lock);
|
|
goto exit;
|
|
}
|
|
}
|
|
|
|
bdi_debug_register(bdi, dev_name(dev));
|
|
set_bit(BDI_registered, &bdi->state);
|
|
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);
|
|
|
|
/*
|
|
* Remove bdi from the global list and shutdown any threads we have running
|
|
*/
|
|
static void bdi_wb_shutdown(struct backing_dev_info *bdi)
|
|
{
|
|
struct bdi_writeback *wb;
|
|
|
|
if (!bdi_cap_writeback_dirty(bdi))
|
|
return;
|
|
|
|
/*
|
|
* If setup is pending, wait for that to complete first
|
|
*/
|
|
wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
|
|
TASK_UNINTERRUPTIBLE);
|
|
|
|
/*
|
|
* Make sure nobody finds us on the bdi_list anymore
|
|
*/
|
|
spin_lock(&bdi_lock);
|
|
list_del(&bdi->bdi_list);
|
|
spin_unlock(&bdi_lock);
|
|
|
|
/*
|
|
* Finally, kill the kernel threads. We don't need to be RCU
|
|
* safe anymore, since the bdi is gone from visibility.
|
|
*/
|
|
list_for_each_entry(wb, &bdi->wb_list, list)
|
|
kthread_stop(wb->task);
|
|
}
|
|
|
|
void bdi_unregister(struct backing_dev_info *bdi)
|
|
{
|
|
if (bdi->dev) {
|
|
if (!bdi_cap_flush_forker(bdi))
|
|
bdi_wb_shutdown(bdi);
|
|
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, err;
|
|
|
|
bdi->dev = NULL;
|
|
|
|
bdi->min_ratio = 0;
|
|
bdi->max_ratio = 100;
|
|
bdi->max_prop_frac = PROP_FRAC_BASE;
|
|
spin_lock_init(&bdi->wb_lock);
|
|
INIT_LIST_HEAD(&bdi->bdi_list);
|
|
INIT_LIST_HEAD(&bdi->wb_list);
|
|
INIT_LIST_HEAD(&bdi->work_list);
|
|
|
|
bdi_wb_init(&bdi->wb, bdi);
|
|
|
|
/*
|
|
* Just one thread support for now, hard code mask and count
|
|
*/
|
|
bdi->wb_mask = 1;
|
|
bdi->wb_cnt = 1;
|
|
|
|
for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
|
|
err = percpu_counter_init(&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;
|
|
|
|
WARN_ON(bdi_has_dirty_io(bdi));
|
|
|
|
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 sync)
|
|
{
|
|
enum bdi_state bit;
|
|
wait_queue_head_t *wqh = &congestion_wqh[sync];
|
|
|
|
bit = sync ? BDI_sync_congested : BDI_async_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 sync)
|
|
{
|
|
enum bdi_state bit;
|
|
|
|
bit = sync ? BDI_sync_congested : BDI_async_congested;
|
|
set_bit(bit, &bdi->state);
|
|
}
|
|
EXPORT_SYMBOL(set_bdi_congested);
|
|
|
|
/**
|
|
* congestion_wait - wait for a backing_dev to become uncongested
|
|
* @sync: SYNC or ASYNC IO
|
|
* @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 sync, long timeout)
|
|
{
|
|
long ret;
|
|
DEFINE_WAIT(wait);
|
|
wait_queue_head_t *wqh = &congestion_wqh[sync];
|
|
|
|
prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
|
|
ret = io_schedule_timeout(timeout);
|
|
finish_wait(wqh, &wait);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(congestion_wait);
|
|
|