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![Peter Zijlstra](/assets/img/avatar_default.png)
Mostly scripted conversion of the smp_mb__* barriers. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Link: http://lkml.kernel.org/n/tip-55dhyhocezdw1dg7u19hmh1u@git.kernel.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: linux-arch@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
676 lines
17 KiB
C
676 lines
17 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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#include <trace/events/writeback.h>
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static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
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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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};
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EXPORT_SYMBOL_GPL(default_backing_dev_info);
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struct backing_dev_info noop_backing_dev_info = {
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.name = "noop",
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.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
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};
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EXPORT_SYMBOL_GPL(noop_backing_dev_info);
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static struct class *bdi_class;
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/*
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* bdi_lock protects updates to bdi_list. bdi_list has RCU reader side
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* locking.
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*/
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DEFINE_SPINLOCK(bdi_lock);
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LIST_HEAD(bdi_list);
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/* bdi_wq serves all asynchronous writeback tasks */
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struct workqueue_struct *bdi_wq;
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void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2)
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{
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if (wb1 < wb2) {
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spin_lock(&wb1->list_lock);
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spin_lock_nested(&wb2->list_lock, 1);
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} else {
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spin_lock(&wb2->list_lock);
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spin_lock_nested(&wb1->list_lock, 1);
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}
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}
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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 = &bdi->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;
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struct inode *inode;
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nr_dirty = nr_io = nr_more_io = 0;
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spin_lock(&wb->list_lock);
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list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
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nr_dirty++;
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list_for_each_entry(inode, &wb->b_io, i_wb_list)
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nr_io++;
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list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
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nr_more_io++;
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spin_unlock(&wb->list_lock);
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global_dirty_limits(&background_thresh, &dirty_thresh);
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bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
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#define K(x) ((x) << (PAGE_SHIFT - 10))
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seq_printf(m,
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"BdiWriteback: %10lu kB\n"
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"BdiReclaimable: %10lu kB\n"
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"BdiDirtyThresh: %10lu kB\n"
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"DirtyThresh: %10lu kB\n"
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"BackgroundThresh: %10lu kB\n"
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"BdiDirtied: %10lu kB\n"
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"BdiWritten: %10lu kB\n"
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"BdiWriteBandwidth: %10lu kBps\n"
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"b_dirty: %10lu\n"
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"b_io: %10lu\n"
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"b_more_io: %10lu\n"
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"bdi_list: %10u\n"
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"state: %10lx\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),
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K(dirty_thresh),
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K(background_thresh),
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(unsigned long) K(bdi_stat(bdi, BDI_DIRTIED)),
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(unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)),
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(unsigned long) K(bdi->write_bandwidth),
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nr_dirty,
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nr_io,
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nr_more_io,
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!list_empty(&bdi->bdi_list), bdi->state);
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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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unsigned long read_ahead_kb;
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ssize_t ret;
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ret = kstrtoul(buf, 10, &read_ahead_kb);
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if (ret < 0)
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return ret;
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bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
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return count;
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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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static DEVICE_ATTR_RW(name);
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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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unsigned int ratio;
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ssize_t ret;
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ret = kstrtouint(buf, 10, &ratio);
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if (ret < 0)
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return ret;
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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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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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unsigned int ratio;
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ssize_t ret;
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ret = kstrtouint(buf, 10, &ratio);
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if (ret < 0)
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return ret;
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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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return ret;
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}
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BDI_SHOW(max_ratio, bdi->max_ratio)
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static ssize_t stable_pages_required_show(struct device *dev,
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struct device_attribute *attr,
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char *page)
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{
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struct backing_dev_info *bdi = dev_get_drvdata(dev);
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return snprintf(page, PAGE_SIZE-1, "%d\n",
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bdi_cap_stable_pages_required(bdi) ? 1 : 0);
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}
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static DEVICE_ATTR_RO(stable_pages_required);
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static struct attribute *bdi_dev_attrs[] = {
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&dev_attr_read_ahead_kb.attr,
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&dev_attr_min_ratio.attr,
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&dev_attr_max_ratio.attr,
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&dev_attr_stable_pages_required.attr,
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NULL,
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};
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ATTRIBUTE_GROUPS(bdi_dev);
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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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if (IS_ERR(bdi_class))
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return PTR_ERR(bdi_class);
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bdi_class->dev_groups = bdi_dev_groups;
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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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bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_FREEZABLE |
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WQ_UNBOUND | WQ_SYSFS, 0);
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if (!bdi_wq)
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return -ENOMEM;
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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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err = bdi_init(&noop_backing_dev_info);
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return err;
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}
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subsys_initcall(default_bdi_init);
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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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/*
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* This function is used when the first inode for this bdi is marked dirty. It
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* wakes-up the corresponding bdi thread which should then take care of the
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* periodic background write-out of dirty inodes. Since the write-out would
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* starts only 'dirty_writeback_interval' centisecs from now anyway, we just
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* set up a timer which wakes the bdi thread up later.
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*
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* Note, we wouldn't bother setting up the timer, but this function is on the
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* fast-path (used by '__mark_inode_dirty()'), so we save few context switches
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* by delaying the wake-up.
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*
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* We have to be careful not to postpone flush work if it is scheduled for
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* earlier. Thus we use queue_delayed_work().
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*/
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void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
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{
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unsigned long timeout;
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timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
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spin_lock_bh(&bdi->wb_lock);
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if (test_bit(BDI_registered, &bdi->state))
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queue_delayed_work(bdi_wq, &bdi->wb.dwork, timeout);
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spin_unlock_bh(&bdi->wb_lock);
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}
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/*
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* Remove bdi from bdi_list, and ensure that it is no longer visible
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*/
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static void bdi_remove_from_list(struct backing_dev_info *bdi)
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{
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spin_lock_bh(&bdi_lock);
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list_del_rcu(&bdi->bdi_list);
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spin_unlock_bh(&bdi_lock);
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synchronize_rcu_expedited();
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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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struct device *dev;
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if (bdi->dev) /* The driver needs to use separate queues per device */
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return 0;
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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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return PTR_ERR(dev);
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bdi->dev = dev;
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bdi_debug_register(bdi, dev_name(dev));
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set_bit(BDI_registered, &bdi->state);
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spin_lock_bh(&bdi_lock);
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list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
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spin_unlock_bh(&bdi_lock);
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trace_writeback_bdi_register(bdi);
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return 0;
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}
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EXPORT_SYMBOL(bdi_register);
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int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
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{
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return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
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}
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EXPORT_SYMBOL(bdi_register_dev);
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/*
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* Remove bdi from the global list and shutdown any threads we have running
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*/
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static void bdi_wb_shutdown(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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/*
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* Make sure nobody finds us on the bdi_list anymore
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*/
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bdi_remove_from_list(bdi);
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/* Make sure nobody queues further work */
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spin_lock_bh(&bdi->wb_lock);
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clear_bit(BDI_registered, &bdi->state);
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spin_unlock_bh(&bdi->wb_lock);
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/*
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* Drain work list and shutdown the delayed_work. At this point,
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* @bdi->bdi_list is empty telling bdi_Writeback_workfn() that @bdi
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* is dying and its work_list needs to be drained no matter what.
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*/
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mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
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flush_delayed_work(&bdi->wb.dwork);
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WARN_ON(!list_empty(&bdi->work_list));
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/*
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* This shouldn't be necessary unless @bdi for some reason has
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* unflushed dirty IO after work_list is drained. Do it anyway
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* just in case.
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*/
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cancel_delayed_work_sync(&bdi->wb.dwork);
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}
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/*
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* This bdi is going away now, make sure that no super_blocks point to it
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*/
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static void bdi_prune_sb(struct backing_dev_info *bdi)
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{
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struct super_block *sb;
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spin_lock(&sb_lock);
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list_for_each_entry(sb, &super_blocks, s_list) {
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if (sb->s_bdi == bdi)
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sb->s_bdi = &default_backing_dev_info;
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}
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spin_unlock(&sb_lock);
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}
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void bdi_unregister(struct backing_dev_info *bdi)
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{
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struct device *dev = bdi->dev;
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if (dev) {
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bdi_set_min_ratio(bdi, 0);
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trace_writeback_bdi_unregister(bdi);
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bdi_prune_sb(bdi);
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bdi_wb_shutdown(bdi);
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bdi_debug_unregister(bdi);
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spin_lock_bh(&bdi->wb_lock);
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bdi->dev = NULL;
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spin_unlock_bh(&bdi->wb_lock);
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device_unregister(dev);
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}
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}
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EXPORT_SYMBOL(bdi_unregister);
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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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spin_lock_init(&wb->list_lock);
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INIT_DELAYED_WORK(&wb->dwork, bdi_writeback_workfn);
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}
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/*
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* Initial write bandwidth: 100 MB/s
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*/
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#define INIT_BW (100 << (20 - PAGE_SHIFT))
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int bdi_init(struct backing_dev_info *bdi)
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{
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int i, err;
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bdi->dev = NULL;
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bdi->min_ratio = 0;
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bdi->max_ratio = 100;
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bdi->max_prop_frac = FPROP_FRAC_BASE;
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spin_lock_init(&bdi->wb_lock);
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INIT_LIST_HEAD(&bdi->bdi_list);
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INIT_LIST_HEAD(&bdi->work_list);
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bdi_wb_init(&bdi->wb, bdi);
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for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
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err = percpu_counter_init(&bdi->bdi_stat[i], 0);
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if (err)
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goto err;
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}
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bdi->dirty_exceeded = 0;
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bdi->bw_time_stamp = jiffies;
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bdi->written_stamp = 0;
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bdi->balanced_dirty_ratelimit = INIT_BW;
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bdi->dirty_ratelimit = INIT_BW;
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bdi->write_bandwidth = INIT_BW;
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bdi->avg_write_bandwidth = INIT_BW;
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err = fprop_local_init_percpu(&bdi->completions);
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if (err) {
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err:
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while (i--)
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percpu_counter_destroy(&bdi->bdi_stat[i]);
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}
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return err;
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}
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EXPORT_SYMBOL(bdi_init);
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void bdi_destroy(struct backing_dev_info *bdi)
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{
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int i;
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/*
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* Splice our entries to the default_backing_dev_info, if this
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* bdi disappears
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*/
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if (bdi_has_dirty_io(bdi)) {
|
|
struct bdi_writeback *dst = &default_backing_dev_info.wb;
|
|
|
|
bdi_lock_two(&bdi->wb, dst);
|
|
list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
|
|
list_splice(&bdi->wb.b_io, &dst->b_io);
|
|
list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
|
|
spin_unlock(&bdi->wb.list_lock);
|
|
spin_unlock(&dst->list_lock);
|
|
}
|
|
|
|
bdi_unregister(bdi);
|
|
|
|
/*
|
|
* If bdi_unregister() had already been called earlier, the dwork
|
|
* could still be pending because bdi_prune_sb() can race with the
|
|
* bdi_wakeup_thread_delayed() calls from __mark_inode_dirty().
|
|
*/
|
|
cancel_delayed_work_sync(&bdi->wb.dwork);
|
|
|
|
for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
|
|
percpu_counter_destroy(&bdi->bdi_stat[i]);
|
|
|
|
fprop_local_destroy_percpu(&bdi->completions);
|
|
}
|
|
EXPORT_SYMBOL(bdi_destroy);
|
|
|
|
/*
|
|
* For use from filesystems to quickly init and register a bdi associated
|
|
* with dirty writeback
|
|
*/
|
|
int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
|
|
unsigned int cap)
|
|
{
|
|
int err;
|
|
|
|
bdi->name = name;
|
|
bdi->capabilities = cap;
|
|
err = bdi_init(bdi);
|
|
if (err)
|
|
return err;
|
|
|
|
err = bdi_register(bdi, NULL, "%.28s-%ld", name,
|
|
atomic_long_inc_return(&bdi_seq));
|
|
if (err) {
|
|
bdi_destroy(bdi);
|
|
return err;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(bdi_setup_and_register);
|
|
|
|
static wait_queue_head_t congestion_wqh[2] = {
|
|
__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
|
|
__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
|
|
};
|
|
static atomic_t nr_bdi_congested[2];
|
|
|
|
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;
|
|
if (test_and_clear_bit(bit, &bdi->state))
|
|
atomic_dec(&nr_bdi_congested[sync]);
|
|
smp_mb__after_atomic();
|
|
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;
|
|
if (!test_and_set_bit(bit, &bdi->state))
|
|
atomic_inc(&nr_bdi_congested[sync]);
|
|
}
|
|
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;
|
|
unsigned long start = jiffies;
|
|
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);
|
|
|
|
trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
|
|
jiffies_to_usecs(jiffies - start));
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(congestion_wait);
|
|
|
|
/**
|
|
* wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
|
|
* @zone: A zone to check if it is heavily congested
|
|
* @sync: SYNC or ASYNC IO
|
|
* @timeout: timeout in jiffies
|
|
*
|
|
* In the event of a congested backing_dev (any backing_dev) and the given
|
|
* @zone has experienced recent congestion, this waits for up to @timeout
|
|
* jiffies for either a BDI to exit congestion of the given @sync queue
|
|
* or a write to complete.
|
|
*
|
|
* In the absence of zone congestion, cond_resched() is called to yield
|
|
* the processor if necessary but otherwise does not sleep.
|
|
*
|
|
* The return value is 0 if the sleep is for the full timeout. Otherwise,
|
|
* it is the number of jiffies that were still remaining when the function
|
|
* returned. return_value == timeout implies the function did not sleep.
|
|
*/
|
|
long wait_iff_congested(struct zone *zone, int sync, long timeout)
|
|
{
|
|
long ret;
|
|
unsigned long start = jiffies;
|
|
DEFINE_WAIT(wait);
|
|
wait_queue_head_t *wqh = &congestion_wqh[sync];
|
|
|
|
/*
|
|
* If there is no congestion, or heavy congestion is not being
|
|
* encountered in the current zone, yield if necessary instead
|
|
* of sleeping on the congestion queue
|
|
*/
|
|
if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
|
|
!zone_is_reclaim_congested(zone)) {
|
|
cond_resched();
|
|
|
|
/* In case we scheduled, work out time remaining */
|
|
ret = timeout - (jiffies - start);
|
|
if (ret < 0)
|
|
ret = 0;
|
|
|
|
goto out;
|
|
}
|
|
|
|
/* Sleep until uncongested or a write happens */
|
|
prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
|
|
ret = io_schedule_timeout(timeout);
|
|
finish_wait(wqh, &wait);
|
|
|
|
out:
|
|
trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
|
|
jiffies_to_usecs(jiffies - start));
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(wait_iff_congested);
|
|
|
|
int pdflush_proc_obsolete(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp, loff_t *ppos)
|
|
{
|
|
char kbuf[] = "0\n";
|
|
|
|
if (*ppos || *lenp < sizeof(kbuf)) {
|
|
*lenp = 0;
|
|
return 0;
|
|
}
|
|
|
|
if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
|
|
return -EFAULT;
|
|
printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",
|
|
table->procname);
|
|
|
|
*lenp = 2;
|
|
*ppos += *lenp;
|
|
return 2;
|
|
}
|