/* * mm/page-writeback.c * * Copyright (C) 2002, Linus Torvalds. * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra * * Contains functions related to writing back dirty pages at the * address_space level. * * 10Apr2002 Andrew Morton * Initial version */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define MAX_PAUSE max(HZ/5, 1) #define DIRTY_POLL_THRESH (128 >> (PAGE_SHIFT - 10)) #define BANDWIDTH_INTERVAL max(HZ/5, 1) #define RATELIMIT_CALC_SHIFT 10 static long ratelimit_pages = 32; int dirty_background_ratio = 10; unsigned long dirty_background_bytes; int vm_highmem_is_dirtyable; int vm_dirty_ratio = 20; unsigned long vm_dirty_bytes; unsigned int dirty_writeback_interval = 5 * 100; EXPORT_SYMBOL_GPL(dirty_writeback_interval); unsigned int dirty_expire_interval = 30 * 100; int block_dump; int laptop_mode; EXPORT_SYMBOL(laptop_mode); unsigned long global_dirty_limit; /* * Scale the writeback cache size proportional to the relative writeout speeds. * * We do this by keeping a floating proportion between BDIs, based on page * writeback completions [end_page_writeback()]. Those devices that write out * pages fastest will get the larger share, while the slower will get a smaller * share. * * We use page writeout completions because we are interested in getting rid of * dirty pages. Having them written out is the primary goal. * * We introduce a concept of time, a period over which we measure these events, * because demand can/will vary over time. The length of this period itself is * measured in page writeback completions. * */ static struct prop_descriptor vm_completions; static unsigned long highmem_dirtyable_memory(unsigned long total) { #ifdef CONFIG_HIGHMEM int node; unsigned long x = 0; for_each_node_state(node, N_HIGH_MEMORY) { struct zone *z = &NODE_DATA(node)->node_zones[ZONE_HIGHMEM]; x += zone_page_state(z, NR_FREE_PAGES) + zone_reclaimable_pages(z) - z->dirty_balance_reserve; } return min(x, total); #else return 0; #endif } unsigned long global_dirtyable_memory(void) { unsigned long x; x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages() - dirty_balance_reserve; if (!vm_highmem_is_dirtyable) x -= highmem_dirtyable_memory(x); return x + 1; } void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) { unsigned long background; unsigned long dirty; unsigned long uninitialized_var(available_memory); struct task_struct *tsk; if (!vm_dirty_bytes || !dirty_background_bytes) available_memory = global_dirtyable_memory(); if (vm_dirty_bytes) dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); else dirty = (vm_dirty_ratio * available_memory) / 100; if (dirty_background_bytes) background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE); else background = (dirty_background_ratio * available_memory) / 100; if (background >= dirty) background = dirty / 2; tsk = current; if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { background += background / 4; dirty += dirty / 4; } *pbackground = background; *pdirty = dirty; trace_global_dirty_state(background, dirty); } static unsigned long zone_dirtyable_memory(struct zone *zone) { return zone_page_state(zone, NR_FREE_PAGES) + zone_reclaimable_pages(zone) - zone->dirty_balance_reserve; } static unsigned long zone_dirty_limit(struct zone *zone) { unsigned long zone_memory = zone_dirtyable_memory(zone); struct task_struct *tsk = current; unsigned long dirty; if (vm_dirty_bytes) dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE) * zone_memory / global_dirtyable_memory(); else dirty = vm_dirty_ratio * zone_memory / 100; if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) dirty += dirty / 4; return dirty; } bool zone_dirty_ok(struct zone *zone) { unsigned long limit = zone_dirty_limit(zone); return zone_page_state(zone, NR_FILE_DIRTY) + zone_page_state(zone, NR_UNSTABLE_NFS) + zone_page_state(zone, NR_WRITEBACK) <= limit; } static int calc_period_shift(void) { unsigned long dirty_total; if (vm_dirty_bytes) dirty_total = vm_dirty_bytes / PAGE_SIZE; else dirty_total = (vm_dirty_ratio * global_dirtyable_memory()) / 100; return 2 + ilog2(dirty_total - 1); } static void update_completion_period(void) { int shift = calc_period_shift(); prop_change_shift(&vm_completions, shift); writeback_set_ratelimit(); } int dirty_background_ratio_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { int ret; ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); if (ret == 0 && write) dirty_background_bytes = 0; return ret; } int dirty_background_bytes_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { int ret; ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); if (ret == 0 && write) dirty_background_ratio = 0; return ret; } int dirty_ratio_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { int old_ratio = vm_dirty_ratio; int ret; ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); if (ret == 0 && write && vm_dirty_ratio != old_ratio) { update_completion_period(); vm_dirty_bytes = 0; } return ret; } int dirty_bytes_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { unsigned long old_bytes = vm_dirty_bytes; int ret; ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); if (ret == 0 && write && vm_dirty_bytes != old_bytes) { update_completion_period(); vm_dirty_ratio = 0; } return ret; } static inline void __bdi_writeout_inc(struct backing_dev_info *bdi) { __inc_bdi_stat(bdi, BDI_WRITTEN); __prop_inc_percpu_max(&vm_completions, &bdi->completions, bdi->max_prop_frac); } void bdi_writeout_inc(struct backing_dev_info *bdi) { unsigned long flags; local_irq_save(flags); __bdi_writeout_inc(bdi); local_irq_restore(flags); } EXPORT_SYMBOL_GPL(bdi_writeout_inc); static void bdi_writeout_fraction(struct backing_dev_info *bdi, long *numerator, long *denominator) { prop_fraction_percpu(&vm_completions, &bdi->completions, numerator, denominator); } static unsigned int bdi_min_ratio; int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) { int ret = 0; spin_lock_bh(&bdi_lock); if (min_ratio > bdi->max_ratio) { ret = -EINVAL; } else { min_ratio -= bdi->min_ratio; if (bdi_min_ratio + min_ratio < 100) { bdi_min_ratio += min_ratio; bdi->min_ratio += min_ratio; } else { ret = -EINVAL; } } spin_unlock_bh(&bdi_lock); return ret; } int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) { int ret = 0; if (max_ratio > 100) return -EINVAL; spin_lock_bh(&bdi_lock); if (bdi->min_ratio > max_ratio) { ret = -EINVAL; } else { bdi->max_ratio = max_ratio; bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100; } spin_unlock_bh(&bdi_lock); return ret; } EXPORT_SYMBOL(bdi_set_max_ratio); static unsigned long dirty_freerun_ceiling(unsigned long thresh, unsigned long bg_thresh) { return (thresh + bg_thresh) / 2; } static unsigned long hard_dirty_limit(unsigned long thresh) { return max(thresh, global_dirty_limit); } unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty) { u64 bdi_dirty; long numerator, denominator; bdi_writeout_fraction(bdi, &numerator, &denominator); bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100; bdi_dirty *= numerator; do_div(bdi_dirty, denominator); bdi_dirty += (dirty * bdi->min_ratio) / 100; if (bdi_dirty > (dirty * bdi->max_ratio) / 100) bdi_dirty = dirty * bdi->max_ratio / 100; return bdi_dirty; } static unsigned long bdi_position_ratio(struct backing_dev_info *bdi, unsigned long thresh, unsigned long bg_thresh, unsigned long dirty, unsigned long bdi_thresh, unsigned long bdi_dirty) { unsigned long write_bw = bdi->avg_write_bandwidth; unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh); unsigned long limit = hard_dirty_limit(thresh); unsigned long x_intercept; unsigned long setpoint; unsigned long bdi_setpoint; unsigned long span; long long pos_ratio; long x; if (unlikely(dirty >= limit)) return 0; setpoint = (freerun + limit) / 2; x = div_s64((setpoint - dirty) << RATELIMIT_CALC_SHIFT, limit - setpoint + 1); pos_ratio = x; pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; pos_ratio += 1 << RATELIMIT_CALC_SHIFT; if (unlikely(bdi_thresh > thresh)) bdi_thresh = thresh; bdi_thresh = max(bdi_thresh, (limit - dirty) / 8); x = div_u64((u64)bdi_thresh << 16, thresh + 1); bdi_setpoint = setpoint * (u64)x >> 16; span = (thresh - bdi_thresh + 8 * write_bw) * (u64)x >> 16; x_intercept = bdi_setpoint + span; if (bdi_dirty < x_intercept - span / 4) { pos_ratio = div_u64(pos_ratio * (x_intercept - bdi_dirty), x_intercept - bdi_setpoint + 1); } else pos_ratio /= 4; x_intercept = bdi_thresh / 2; if (bdi_dirty < x_intercept) { if (bdi_dirty > x_intercept / 8) pos_ratio = div_u64(pos_ratio * x_intercept, bdi_dirty); else pos_ratio *= 8; } return pos_ratio; } static void bdi_update_write_bandwidth(struct backing_dev_info *bdi, unsigned long elapsed, unsigned long written) { const unsigned long period = roundup_pow_of_two(3 * HZ); unsigned long avg = bdi->avg_write_bandwidth; unsigned long old = bdi->write_bandwidth; u64 bw; /* * bw = written * HZ / elapsed * * bw * elapsed + write_bandwidth * (period - elapsed) * write_bandwidth = --------------------------------------------------- * period */ bw = written - bdi->written_stamp; bw *= HZ; if (unlikely(elapsed > period)) { do_div(bw, elapsed); avg = bw; goto out; } bw += (u64)bdi->write_bandwidth * (period - elapsed); bw >>= ilog2(period); if (avg > old && old >= (unsigned long)bw) avg -= (avg - old) >> 3; if (avg < old && old <= (unsigned long)bw) avg += (old - avg) >> 3; out: bdi->write_bandwidth = bw; bdi->avg_write_bandwidth = avg; } static void update_dirty_limit(unsigned long thresh, unsigned long dirty) { unsigned long limit = global_dirty_limit; if (limit < thresh) { limit = thresh; goto update; } thresh = max(thresh, dirty); if (limit > thresh) { limit -= (limit - thresh) >> 5; goto update; } return; update: global_dirty_limit = limit; } static void global_update_bandwidth(unsigned long thresh, unsigned long dirty, unsigned long now) { static DEFINE_SPINLOCK(dirty_lock); static unsigned long update_time; if (time_before(now, update_time + BANDWIDTH_INTERVAL)) return; spin_lock(&dirty_lock); if (time_after_eq(now, update_time + BANDWIDTH_INTERVAL)) { update_dirty_limit(thresh, dirty); update_time = now; } spin_unlock(&dirty_lock); } static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi, unsigned long thresh, unsigned long bg_thresh, unsigned long dirty, unsigned long bdi_thresh, unsigned long bdi_dirty, unsigned long dirtied, unsigned long elapsed) { unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh); unsigned long limit = hard_dirty_limit(thresh); unsigned long setpoint = (freerun + limit) / 2; unsigned long write_bw = bdi->avg_write_bandwidth; unsigned long dirty_ratelimit = bdi->dirty_ratelimit; unsigned long dirty_rate; unsigned long task_ratelimit; unsigned long balanced_dirty_ratelimit; unsigned long pos_ratio; unsigned long step; unsigned long x; dirty_rate = (dirtied - bdi->dirtied_stamp) * HZ / elapsed; pos_ratio = bdi_position_ratio(bdi, thresh, bg_thresh, dirty, bdi_thresh, bdi_dirty); task_ratelimit = (u64)dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT; task_ratelimit++; balanced_dirty_ratelimit = div_u64((u64)task_ratelimit * write_bw, dirty_rate | 1); if (unlikely(balanced_dirty_ratelimit > write_bw)) balanced_dirty_ratelimit = write_bw; step = 0; if (dirty < setpoint) { x = min(bdi->balanced_dirty_ratelimit, min(balanced_dirty_ratelimit, task_ratelimit)); if (dirty_ratelimit < x) step = x - dirty_ratelimit; } else { x = max(bdi->balanced_dirty_ratelimit, max(balanced_dirty_ratelimit, task_ratelimit)); if (dirty_ratelimit > x) step = dirty_ratelimit - x; } step >>= dirty_ratelimit / (2 * step + 1); step = (step + 7) / 8; if (dirty_ratelimit < balanced_dirty_ratelimit) dirty_ratelimit += step; else dirty_ratelimit -= step; bdi->dirty_ratelimit = max(dirty_ratelimit, 1UL); bdi->balanced_dirty_ratelimit = balanced_dirty_ratelimit; trace_bdi_dirty_ratelimit(bdi, dirty_rate, task_ratelimit); } void __bdi_update_bandwidth(struct backing_dev_info *bdi, unsigned long thresh, unsigned long bg_thresh, unsigned long dirty, unsigned long bdi_thresh, unsigned long bdi_dirty, unsigned long start_time) { unsigned long now = jiffies; unsigned long elapsed = now - bdi->bw_time_stamp; unsigned long dirtied; unsigned long written; if (elapsed < BANDWIDTH_INTERVAL) return; dirtied = percpu_counter_read(&bdi->bdi_stat[BDI_DIRTIED]); written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]); if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time)) goto snapshot; if (thresh) { global_update_bandwidth(thresh, dirty, now); bdi_update_dirty_ratelimit(bdi, thresh, bg_thresh, dirty, bdi_thresh, bdi_dirty, dirtied, elapsed); } bdi_update_write_bandwidth(bdi, elapsed, written); snapshot: bdi->dirtied_stamp = dirtied; bdi->written_stamp = written; bdi->bw_time_stamp = now; } static void bdi_update_bandwidth(struct backing_dev_info *bdi, unsigned long thresh, unsigned long bg_thresh, unsigned long dirty, unsigned long bdi_thresh, unsigned long bdi_dirty, unsigned long start_time) { if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL)) return; spin_lock(&bdi->wb.list_lock); __bdi_update_bandwidth(bdi, thresh, bg_thresh, dirty, bdi_thresh, bdi_dirty, start_time); spin_unlock(&bdi->wb.list_lock); } static unsigned long dirty_poll_interval(unsigned long dirty, unsigned long thresh) { if (thresh > dirty) return 1UL << (ilog2(thresh - dirty) >> 1); return 1; } static long bdi_max_pause(struct backing_dev_info *bdi, unsigned long bdi_dirty) { long bw = bdi->avg_write_bandwidth; long t; t = bdi_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8)); t++; return min_t(long, t, MAX_PAUSE); } static long bdi_min_pause(struct backing_dev_info *bdi, long max_pause, unsigned long task_ratelimit, unsigned long dirty_ratelimit, int *nr_dirtied_pause) { long hi = ilog2(bdi->avg_write_bandwidth); long lo = ilog2(bdi->dirty_ratelimit); long t; long pause; int pages; t = max(1, HZ / 100); if (hi > lo) t += (hi - lo) * (10 * HZ) / 1024; t = min(t, 1 + max_pause / 2); pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); if (pages < DIRTY_POLL_THRESH) { t = max_pause; pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); if (pages > DIRTY_POLL_THRESH) { pages = DIRTY_POLL_THRESH; t = HZ * DIRTY_POLL_THRESH / dirty_ratelimit; } } pause = HZ * pages / (task_ratelimit + 1); if (pause > max_pause) { t = max_pause; pages = task_ratelimit * t / roundup_pow_of_two(HZ); } *nr_dirtied_pause = pages; return pages >= DIRTY_POLL_THRESH ? 1 + t / 2 : t; } static void balance_dirty_pages(struct address_space *mapping, unsigned long pages_dirtied) { unsigned long nr_reclaimable; unsigned long bdi_reclaimable; unsigned long nr_dirty; unsigned long bdi_dirty; unsigned long freerun; unsigned long background_thresh; unsigned long dirty_thresh; unsigned long bdi_thresh; long period; long pause; long max_pause; long min_pause; int nr_dirtied_pause; bool dirty_exceeded = false; unsigned long task_ratelimit; unsigned long dirty_ratelimit; unsigned long pos_ratio; struct backing_dev_info *bdi = mapping->backing_dev_info; unsigned long start_time = jiffies; for (;;) { unsigned long now = jiffies; /* * Unstable writes are a feature of certain networked * filesystems (i.e. NFS) in which data may have been * written to the server's write cache, but has not yet * been flushed to permanent storage. */ nr_reclaimable = global_page_state(NR_FILE_DIRTY) + global_page_state(NR_UNSTABLE_NFS); nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK); global_dirty_limits(&background_thresh, &dirty_thresh); freerun = dirty_freerun_ceiling(dirty_thresh, background_thresh); if (nr_dirty <= freerun) { current->dirty_paused_when = now; current->nr_dirtied = 0; current->nr_dirtied_pause = dirty_poll_interval(nr_dirty, dirty_thresh); break; } if (unlikely(!writeback_in_progress(bdi))) bdi_start_background_writeback(bdi); bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh); if (bdi_thresh < 2 * bdi_stat_error(bdi)) { bdi_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); bdi_dirty = bdi_reclaimable + bdi_stat_sum(bdi, BDI_WRITEBACK); } else { bdi_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); bdi_dirty = bdi_reclaimable + bdi_stat(bdi, BDI_WRITEBACK); } dirty_exceeded = (bdi_dirty > bdi_thresh) && (nr_dirty > dirty_thresh); if (dirty_exceeded && !bdi->dirty_exceeded) bdi->dirty_exceeded = 1; bdi_update_bandwidth(bdi, dirty_thresh, background_thresh, nr_dirty, bdi_thresh, bdi_dirty, start_time); dirty_ratelimit = bdi->dirty_ratelimit; pos_ratio = bdi_position_ratio(bdi, dirty_thresh, background_thresh, nr_dirty, bdi_thresh, bdi_dirty); task_ratelimit = ((u64)dirty_ratelimit * pos_ratio) >> RATELIMIT_CALC_SHIFT; max_pause = bdi_max_pause(bdi, bdi_dirty); min_pause = bdi_min_pause(bdi, max_pause, task_ratelimit, dirty_ratelimit, &nr_dirtied_pause); if (unlikely(task_ratelimit == 0)) { period = max_pause; pause = max_pause; goto pause; } period = HZ * pages_dirtied / task_ratelimit; pause = period; if (current->dirty_paused_when) pause -= now - current->dirty_paused_when; if (pause < min_pause) { trace_balance_dirty_pages(bdi, dirty_thresh, background_thresh, nr_dirty, bdi_thresh, bdi_dirty, dirty_ratelimit, task_ratelimit, pages_dirtied, period, min(pause, 0L), start_time); if (pause < -HZ) { current->dirty_paused_when = now; current->nr_dirtied = 0; } else if (period) { current->dirty_paused_when += period; current->nr_dirtied = 0; } else if (current->nr_dirtied_pause <= pages_dirtied) current->nr_dirtied_pause += pages_dirtied; break; } if (unlikely(pause > max_pause)) { now += min(pause - max_pause, max_pause); pause = max_pause; } pause: trace_balance_dirty_pages(bdi, dirty_thresh, background_thresh, nr_dirty, bdi_thresh, bdi_dirty, dirty_ratelimit, task_ratelimit, pages_dirtied, period, pause, start_time); __set_current_state(TASK_KILLABLE); io_schedule_timeout(pause); current->dirty_paused_when = now + pause; current->nr_dirtied = 0; current->nr_dirtied_pause = nr_dirtied_pause; if (task_ratelimit) break; if (bdi_dirty <= bdi_stat_error(bdi)) break; if (fatal_signal_pending(current)) break; } if (!dirty_exceeded && bdi->dirty_exceeded) bdi->dirty_exceeded = 0; if (writeback_in_progress(bdi)) return; if (laptop_mode) return; if (nr_reclaimable > background_thresh) bdi_start_background_writeback(bdi); } void set_page_dirty_balance(struct page *page, int page_mkwrite) { if (set_page_dirty(page) || page_mkwrite) { struct address_space *mapping = page_mapping(page); if (mapping) balance_dirty_pages_ratelimited(mapping); } } static DEFINE_PER_CPU(int, bdp_ratelimits); DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0; void balance_dirty_pages_ratelimited_nr(struct address_space *mapping, unsigned long nr_pages_dirtied) { struct backing_dev_info *bdi = mapping->backing_dev_info; int ratelimit; int *p; if (!bdi_cap_account_dirty(bdi)) return; ratelimit = current->nr_dirtied_pause; if (bdi->dirty_exceeded) ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10)); preempt_disable(); p = &__get_cpu_var(bdp_ratelimits); if (unlikely(current->nr_dirtied >= ratelimit)) *p = 0; else if (unlikely(*p >= ratelimit_pages)) { *p = 0; ratelimit = 0; } p = &__get_cpu_var(dirty_throttle_leaks); if (*p > 0 && current->nr_dirtied < ratelimit) { nr_pages_dirtied = min(*p, ratelimit - current->nr_dirtied); *p -= nr_pages_dirtied; current->nr_dirtied += nr_pages_dirtied; } preempt_enable(); if (unlikely(current->nr_dirtied >= ratelimit)) balance_dirty_pages(mapping, current->nr_dirtied); } EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr); void throttle_vm_writeout(gfp_t gfp_mask) { unsigned long background_thresh; unsigned long dirty_thresh; for ( ; ; ) { global_dirty_limits(&background_thresh, &dirty_thresh); dirty_thresh = hard_dirty_limit(dirty_thresh); dirty_thresh += dirty_thresh / 10; if (global_page_state(NR_UNSTABLE_NFS) + global_page_state(NR_WRITEBACK) <= dirty_thresh) break; congestion_wait(BLK_RW_ASYNC, HZ/10); if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) break; } } int dirty_writeback_centisecs_handler(ctl_table *table, int write, void __user *buffer, size_t *length, loff_t *ppos) { proc_dointvec(table, write, buffer, length, ppos); bdi_arm_supers_timer(); return 0; } #ifdef CONFIG_BLOCK void laptop_mode_timer_fn(unsigned long data) { struct request_queue *q = (struct request_queue *)data; int nr_pages = global_page_state(NR_FILE_DIRTY) + global_page_state(NR_UNSTABLE_NFS); if (bdi_has_dirty_io(&q->backing_dev_info)) bdi_start_writeback(&q->backing_dev_info, nr_pages, WB_REASON_LAPTOP_TIMER); } void laptop_io_completion(struct backing_dev_info *info) { mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode); } /* * We're in laptop mode and we've just synced. The sync's writes will have * caused another writeback to be scheduled by laptop_io_completion. * Nothing needs to be written back anymore, so we unschedule the writeback. */ void laptop_sync_completion(void) { struct backing_dev_info *bdi; rcu_read_lock(); list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) del_timer(&bdi->laptop_mode_wb_timer); rcu_read_unlock(); } #endif void writeback_set_ratelimit(void) { unsigned long background_thresh; unsigned long dirty_thresh; global_dirty_limits(&background_thresh, &dirty_thresh); ratelimit_pages = dirty_thresh / (num_online_cpus() * 32); if (ratelimit_pages < 16) ratelimit_pages = 16; } static int __cpuinit ratelimit_handler(struct notifier_block *self, unsigned long u, void *v) { writeback_set_ratelimit(); return NOTIFY_DONE; } static struct notifier_block __cpuinitdata ratelimit_nb = { .notifier_call = ratelimit_handler, .next = NULL, }; void __init page_writeback_init(void) { int shift; writeback_set_ratelimit(); register_cpu_notifier(&ratelimit_nb); shift = calc_period_shift(); prop_descriptor_init(&vm_completions, shift); } /** * tag_pages_for_writeback - tag pages to be written by write_cache_pages * @mapping: address space structure to write * @start: starting page index * @end: ending page index (inclusive) * * This function scans the page range from @start to @end (inclusive) and tags * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is * that write_cache_pages (or whoever calls this function) will then use * TOWRITE tag to identify pages eligible for writeback. This mechanism is * used to avoid livelocking of writeback by a process steadily creating new * dirty pages in the file (thus it is important for this function to be quick * so that it can tag pages faster than a dirtying process can create them). */ void tag_pages_for_writeback(struct address_space *mapping, pgoff_t start, pgoff_t end) { #define WRITEBACK_TAG_BATCH 4096 unsigned long tagged; do { spin_lock_irq(&mapping->tree_lock); tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree, &start, end, WRITEBACK_TAG_BATCH, PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE); spin_unlock_irq(&mapping->tree_lock); WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH); cond_resched(); } while (tagged >= WRITEBACK_TAG_BATCH && start); } EXPORT_SYMBOL(tag_pages_for_writeback); /** * write_cache_pages - walk the list of dirty pages of the given address space and write all of them. * @mapping: address space structure to write * @wbc: subtract the number of written pages from *@wbc->nr_to_write * @writepage: function called for each page * @data: data passed to writepage function * * If a page is already under I/O, write_cache_pages() skips it, even * if it's dirty. This is desirable behaviour for memory-cleaning writeback, * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() * and msync() need to guarantee that all the data which was dirty at the time * the call was made get new I/O started against them. If wbc->sync_mode is * WB_SYNC_ALL then we were called for data integrity and we must wait for * existing IO to complete. * * To avoid livelocks (when other process dirties new pages), we first tag * pages which should be written back with TOWRITE tag and only then start * writing them. For data-integrity sync we have to be careful so that we do * not miss some pages (e.g., because some other process has cleared TOWRITE * tag we set). The rule we follow is that TOWRITE tag can be cleared only * by the process clearing the DIRTY tag (and submitting the page for IO). */ int write_cache_pages(struct address_space *mapping, struct writeback_control *wbc, writepage_t writepage, void *data) { int ret = 0; int done = 0; struct pagevec pvec; int nr_pages; pgoff_t uninitialized_var(writeback_index); pgoff_t index; pgoff_t end; pgoff_t done_index; int cycled; int range_whole = 0; int tag; pagevec_init(&pvec, 0); if (wbc->range_cyclic) { writeback_index = mapping->writeback_index; index = writeback_index; if (index == 0) cycled = 1; else cycled = 0; end = -1; } else { index = wbc->range_start >> PAGE_CACHE_SHIFT; end = wbc->range_end >> PAGE_CACHE_SHIFT; if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) range_whole = 1; cycled = 1; } if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) tag = PAGECACHE_TAG_TOWRITE; else tag = PAGECACHE_TAG_DIRTY; retry: if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) tag_pages_for_writeback(mapping, index, end); done_index = index; while (!done && (index <= end)) { int i; nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag, min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1); if (nr_pages == 0) break; for (i = 0; i < nr_pages; i++) { struct page *page = pvec.pages[i]; if (page->index > end) { done = 1; break; } done_index = page->index; lock_page(page); if (unlikely(page->mapping != mapping)) { continue_unlock: unlock_page(page); continue; } if (!PageDirty(page)) { goto continue_unlock; } if (PageWriteback(page)) { if (wbc->sync_mode != WB_SYNC_NONE) wait_on_page_writeback(page); else goto continue_unlock; } BUG_ON(PageWriteback(page)); if (!clear_page_dirty_for_io(page)) goto continue_unlock; trace_wbc_writepage(wbc, mapping->backing_dev_info); ret = (*writepage)(page, wbc, data); if (unlikely(ret)) { if (ret == AOP_WRITEPAGE_ACTIVATE) { unlock_page(page); ret = 0; } else { done_index = page->index + 1; done = 1; break; } } /* * We stop writing back only if we are not doing * integrity sync. In case of integrity sync we have to * keep going until we have written all the pages * we tagged for writeback prior to entering this loop. */ if (--wbc->nr_to_write <= 0 && wbc->sync_mode == WB_SYNC_NONE) { done = 1; break; } } pagevec_release(&pvec); cond_resched(); } if (!cycled && !done) { cycled = 1; index = 0; end = writeback_index - 1; goto retry; } if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) mapping->writeback_index = done_index; return ret; } EXPORT_SYMBOL(write_cache_pages); static int __writepage(struct page *page, struct writeback_control *wbc, void *data) { struct address_space *mapping = data; int ret = mapping->a_ops->writepage(page, wbc); mapping_set_error(mapping, ret); return ret; } /** * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them. * @mapping: address space structure to write * @wbc: subtract the number of written pages from *@wbc->nr_to_write * * This is a library function, which implements the writepages() * address_space_operation. */ int generic_writepages(struct address_space *mapping, struct writeback_control *wbc) { struct blk_plug plug; int ret; if (!mapping->a_ops->writepage) return 0; blk_start_plug(&plug); ret = write_cache_pages(mapping, wbc, __writepage, mapping); blk_finish_plug(&plug); return ret; } EXPORT_SYMBOL(generic_writepages); int do_writepages(struct address_space *mapping, struct writeback_control *wbc) { int ret; if (wbc->nr_to_write <= 0) return 0; if (mapping->a_ops->writepages) ret = mapping->a_ops->writepages(mapping, wbc); else ret = generic_writepages(mapping, wbc); return ret; } int write_one_page(struct page *page, int wait) { struct address_space *mapping = page->mapping; int ret = 0; struct writeback_control wbc = { .sync_mode = WB_SYNC_ALL, .nr_to_write = 1, }; BUG_ON(!PageLocked(page)); if (wait) wait_on_page_writeback(page); if (clear_page_dirty_for_io(page)) { page_cache_get(page); ret = mapping->a_ops->writepage(page, &wbc); if (ret == 0 && wait) { wait_on_page_writeback(page); if (PageError(page)) ret = -EIO; } page_cache_release(page); } else { unlock_page(page); } return ret; } EXPORT_SYMBOL(write_one_page); int __set_page_dirty_no_writeback(struct page *page) { if (!PageDirty(page)) return !TestSetPageDirty(page); return 0; } void account_page_dirtied(struct page *page, struct address_space *mapping) { if (mapping_cap_account_dirty(mapping)) { __inc_zone_page_state(page, NR_FILE_DIRTY); __inc_zone_page_state(page, NR_DIRTIED); __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); __inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED); task_io_account_write(PAGE_CACHE_SIZE); current->nr_dirtied++; this_cpu_inc(bdp_ratelimits); } } EXPORT_SYMBOL(account_page_dirtied); void account_page_writeback(struct page *page) { inc_zone_page_state(page, NR_WRITEBACK); } EXPORT_SYMBOL(account_page_writeback); int __set_page_dirty_nobuffers(struct page *page) { if (!TestSetPageDirty(page)) { struct address_space *mapping = page_mapping(page); struct address_space *mapping2; unsigned long flags; if (!mapping) return 1; spin_lock_irqsave(&mapping->tree_lock, flags); mapping2 = page_mapping(page); if (mapping2) { BUG_ON(mapping2 != mapping); WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page)); account_page_dirtied(page, mapping); radix_tree_tag_set(&mapping->page_tree, page_index(page), PAGECACHE_TAG_DIRTY); } spin_unlock_irqrestore(&mapping->tree_lock, flags); if (mapping->host) { __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); } return 1; } return 0; } EXPORT_SYMBOL(__set_page_dirty_nobuffers); /* * Call this whenever redirtying a page, to de-account the dirty counters * (NR_DIRTIED, BDI_DIRTIED, tsk->nr_dirtied), so that they match the written * counters (NR_WRITTEN, BDI_WRITTEN) in long term. The mismatches will lead to * systematic errors in balanced_dirty_ratelimit and the dirty pages position * control. */ void account_page_redirty(struct page *page) { struct address_space *mapping = page->mapping; if (mapping && mapping_cap_account_dirty(mapping)) { current->nr_dirtied--; dec_zone_page_state(page, NR_DIRTIED); dec_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED); } } EXPORT_SYMBOL(account_page_redirty); int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) { wbc->pages_skipped++; account_page_redirty(page); return __set_page_dirty_nobuffers(page); } EXPORT_SYMBOL(redirty_page_for_writepage); int set_page_dirty(struct page *page) { struct address_space *mapping = page_mapping(page); if (likely(mapping)) { int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; /* * readahead/lru_deactivate_page could remain * PG_readahead/PG_reclaim due to race with end_page_writeback * About readahead, if the page is written, the flags would be * reset. So no problem. * About lru_deactivate_page, if the page is redirty, the flag * will be reset. So no problem. but if the page is used by readahead * it will confuse readahead and make it restart the size rampup * process. But it's a trivial problem. */ ClearPageReclaim(page); #ifdef CONFIG_BLOCK if (!spd) spd = __set_page_dirty_buffers; #endif return (*spd)(page); } if (!PageDirty(page)) { if (!TestSetPageDirty(page)) return 1; } return 0; } EXPORT_SYMBOL(set_page_dirty); int set_page_dirty_lock(struct page *page) { int ret; lock_page(page); ret = set_page_dirty(page); unlock_page(page); return ret; } EXPORT_SYMBOL(set_page_dirty_lock); int clear_page_dirty_for_io(struct page *page) { struct address_space *mapping = page_mapping(page); BUG_ON(!PageLocked(page)); if (mapping && mapping_cap_account_dirty(mapping)) { if (page_mkclean(page)) set_page_dirty(page); if (TestClearPageDirty(page)) { dec_zone_page_state(page, NR_FILE_DIRTY); dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); return 1; } return 0; } return TestClearPageDirty(page); } EXPORT_SYMBOL(clear_page_dirty_for_io); int test_clear_page_writeback(struct page *page) { struct address_space *mapping = page_mapping(page); int ret; if (mapping) { struct backing_dev_info *bdi = mapping->backing_dev_info; unsigned long flags; spin_lock_irqsave(&mapping->tree_lock, flags); ret = TestClearPageWriteback(page); if (ret) { radix_tree_tag_clear(&mapping->page_tree, page_index(page), PAGECACHE_TAG_WRITEBACK); if (bdi_cap_account_writeback(bdi)) { __dec_bdi_stat(bdi, BDI_WRITEBACK); __bdi_writeout_inc(bdi); } } spin_unlock_irqrestore(&mapping->tree_lock, flags); } else { ret = TestClearPageWriteback(page); } if (ret) { dec_zone_page_state(page, NR_WRITEBACK); inc_zone_page_state(page, NR_WRITTEN); } return ret; } int test_set_page_writeback(struct page *page) { struct address_space *mapping = page_mapping(page); int ret; if (mapping) { struct backing_dev_info *bdi = mapping->backing_dev_info; unsigned long flags; spin_lock_irqsave(&mapping->tree_lock, flags); ret = TestSetPageWriteback(page); if (!ret) { radix_tree_tag_set(&mapping->page_tree, page_index(page), PAGECACHE_TAG_WRITEBACK); if (bdi_cap_account_writeback(bdi)) __inc_bdi_stat(bdi, BDI_WRITEBACK); } if (!PageDirty(page)) radix_tree_tag_clear(&mapping->page_tree, page_index(page), PAGECACHE_TAG_DIRTY); radix_tree_tag_clear(&mapping->page_tree, page_index(page), PAGECACHE_TAG_TOWRITE); spin_unlock_irqrestore(&mapping->tree_lock, flags); } else { ret = TestSetPageWriteback(page); } if (!ret) account_page_writeback(page); return ret; } EXPORT_SYMBOL(test_set_page_writeback); int mapping_tagged(struct address_space *mapping, int tag) { return radix_tree_tagged(&mapping->page_tree, tag); } EXPORT_SYMBOL(mapping_tagged);