| /* |
| * 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 <linux/kernel.h> |
| #include <linux/export.h> |
| #include <linux/spinlock.h> |
| #include <linux/fs.h> |
| #include <linux/mm.h> |
| #include <linux/swap.h> |
| #include <linux/slab.h> |
| #include <linux/pagemap.h> |
| #include <linux/writeback.h> |
| #include <linux/init.h> |
| #include <linux/backing-dev.h> |
| #include <linux/task_io_accounting_ops.h> |
| #include <linux/blkdev.h> |
| #include <linux/mpage.h> |
| #include <linux/rmap.h> |
| #include <linux/percpu.h> |
| #include <linux/notifier.h> |
| #include <linux/smp.h> |
| #include <linux/sysctl.h> |
| #include <linux/cpu.h> |
| #include <linux/syscalls.h> |
| #include <linux/buffer_head.h> /* __set_page_dirty_buffers */ |
| #include <linux/pagevec.h> |
| #include <linux/timer.h> |
| #include <linux/sched/rt.h> |
| #include <linux/sched/signal.h> |
| #include <linux/mm_inline.h> |
| #include <trace/events/writeback.h> |
| |
| #include "internal.h" |
| |
| /* |
| * Sleep at most 200ms at a time in balance_dirty_pages(). |
| */ |
| #define MAX_PAUSE max(HZ/5, 1) |
| |
| /* |
| * Try to keep balance_dirty_pages() call intervals higher than this many pages |
| * by raising pause time to max_pause when falls below it. |
| */ |
| #define DIRTY_POLL_THRESH (128 >> (PAGE_SHIFT - 10)) |
| |
| /* |
| * Estimate write bandwidth at 200ms intervals. |
| */ |
| #define BANDWIDTH_INTERVAL max(HZ/5, 1) |
| |
| #define RATELIMIT_CALC_SHIFT 10 |
| |
| /* |
| * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited |
| * will look to see if it needs to force writeback or throttling. |
| */ |
| static long ratelimit_pages = 32; |
| |
| /* The following parameters are exported via /proc/sys/vm */ |
| |
| /* |
| * Start background writeback (via writeback threads) at this percentage |
| */ |
| int dirty_background_ratio = 10; |
| |
| /* |
| * dirty_background_bytes starts at 0 (disabled) so that it is a function of |
| * dirty_background_ratio * the amount of dirtyable memory |
| */ |
| unsigned long dirty_background_bytes; |
| |
| /* |
| * free highmem will not be subtracted from the total free memory |
| * for calculating free ratios if vm_highmem_is_dirtyable is true |
| */ |
| int vm_highmem_is_dirtyable; |
| |
| /* |
| * The generator of dirty data starts writeback at this percentage |
| */ |
| int vm_dirty_ratio = 20; |
| |
| /* |
| * vm_dirty_bytes starts at 0 (disabled) so that it is a function of |
| * vm_dirty_ratio * the amount of dirtyable memory |
| */ |
| unsigned long vm_dirty_bytes; |
| |
| /* |
| * The interval between `kupdate'-style writebacks |
| */ |
| unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */ |
| |
| EXPORT_SYMBOL_GPL(dirty_writeback_interval); |
| |
| /* |
| * The longest time for which data is allowed to remain dirty |
| */ |
| unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */ |
| |
| /* |
| * Flag that makes the machine dump writes/reads and block dirtyings. |
| */ |
| int block_dump; |
| |
| /* |
| * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies: |
| * a full sync is triggered after this time elapses without any disk activity. |
| */ |
| int laptop_mode; |
| |
| EXPORT_SYMBOL(laptop_mode); |
| |
| /* End of sysctl-exported parameters */ |
| |
| struct wb_domain global_wb_domain; |
| |
| /* consolidated parameters for balance_dirty_pages() and its subroutines */ |
| struct dirty_throttle_control { |
| #ifdef CONFIG_CGROUP_WRITEBACK |
| struct wb_domain *dom; |
| struct dirty_throttle_control *gdtc; /* only set in memcg dtc's */ |
| #endif |
| struct bdi_writeback *wb; |
| struct fprop_local_percpu *wb_completions; |
| |
| unsigned long avail; /* dirtyable */ |
| unsigned long dirty; /* file_dirty + write + nfs */ |
| unsigned long thresh; /* dirty threshold */ |
| unsigned long bg_thresh; /* dirty background threshold */ |
| |
| unsigned long wb_dirty; /* per-wb counterparts */ |
| unsigned long wb_thresh; |
| unsigned long wb_bg_thresh; |
| |
| unsigned long pos_ratio; |
| }; |
| |
| /* |
| * Length of period for aging writeout fractions of bdis. This is an |
| * arbitrarily chosen number. The longer the period, the slower fractions will |
| * reflect changes in current writeout rate. |
| */ |
| #define VM_COMPLETIONS_PERIOD_LEN (3*HZ) |
| |
| #ifdef CONFIG_CGROUP_WRITEBACK |
| |
| #define GDTC_INIT(__wb) .wb = (__wb), \ |
| .dom = &global_wb_domain, \ |
| .wb_completions = &(__wb)->completions |
| |
| #define GDTC_INIT_NO_WB .dom = &global_wb_domain |
| |
| #define MDTC_INIT(__wb, __gdtc) .wb = (__wb), \ |
| .dom = mem_cgroup_wb_domain(__wb), \ |
| .wb_completions = &(__wb)->memcg_completions, \ |
| .gdtc = __gdtc |
| |
| static bool mdtc_valid(struct dirty_throttle_control *dtc) |
| { |
| return dtc->dom; |
| } |
| |
| static struct wb_domain *dtc_dom(struct dirty_throttle_control *dtc) |
| { |
| return dtc->dom; |
| } |
| |
| static struct dirty_throttle_control *mdtc_gdtc(struct dirty_throttle_control *mdtc) |
| { |
| return mdtc->gdtc; |
| } |
| |
| static struct fprop_local_percpu *wb_memcg_completions(struct bdi_writeback *wb) |
| { |
| return &wb->memcg_completions; |
| } |
| |
| static void wb_min_max_ratio(struct bdi_writeback *wb, |
| unsigned long *minp, unsigned long *maxp) |
| { |
| unsigned long this_bw = wb->avg_write_bandwidth; |
| unsigned long tot_bw = atomic_long_read(&wb->bdi->tot_write_bandwidth); |
| unsigned long long min = wb->bdi->min_ratio; |
| unsigned long long max = wb->bdi->max_ratio; |
| |
| /* |
| * @wb may already be clean by the time control reaches here and |
| * the total may not include its bw. |
| */ |
| if (this_bw < tot_bw) { |
| if (min) { |
| min *= this_bw; |
| do_div(min, tot_bw); |
| } |
| if (max < 100) { |
| max *= this_bw; |
| do_div(max, tot_bw); |
| } |
| } |
| |
| *minp = min; |
| *maxp = max; |
| } |
| |
| #else /* CONFIG_CGROUP_WRITEBACK */ |
| |
| #define GDTC_INIT(__wb) .wb = (__wb), \ |
| .wb_completions = &(__wb)->completions |
| #define GDTC_INIT_NO_WB |
| #define MDTC_INIT(__wb, __gdtc) |
| |
| static bool mdtc_valid(struct dirty_throttle_control *dtc) |
| { |
| return false; |
| } |
| |
| static struct wb_domain *dtc_dom(struct dirty_throttle_control *dtc) |
| { |
| return &global_wb_domain; |
| } |
| |
| static struct dirty_throttle_control *mdtc_gdtc(struct dirty_throttle_control *mdtc) |
| { |
| return NULL; |
| } |
| |
| static struct fprop_local_percpu *wb_memcg_completions(struct bdi_writeback *wb) |
| { |
| return NULL; |
| } |
| |
| static void wb_min_max_ratio(struct bdi_writeback *wb, |
| unsigned long *minp, unsigned long *maxp) |
| { |
| *minp = wb->bdi->min_ratio; |
| *maxp = wb->bdi->max_ratio; |
| } |
| |
| #endif /* CONFIG_CGROUP_WRITEBACK */ |
| |
| /* |
| * In a memory zone, there is a certain amount of pages we consider |
| * available for the page cache, which is essentially the number of |
| * free and reclaimable pages, minus some zone reserves to protect |
| * lowmem and the ability to uphold the zone's watermarks without |
| * requiring writeback. |
| * |
| * This number of dirtyable pages is the base value of which the |
| * user-configurable dirty ratio is the effictive number of pages that |
| * are allowed to be actually dirtied. Per individual zone, or |
| * globally by using the sum of dirtyable pages over all zones. |
| * |
| * Because the user is allowed to specify the dirty limit globally as |
| * absolute number of bytes, calculating the per-zone dirty limit can |
| * require translating the configured limit into a percentage of |
| * global dirtyable memory first. |
| */ |
| |
| /** |
| * node_dirtyable_memory - number of dirtyable pages in a node |
| * @pgdat: the node |
| * |
| * Returns the node's number of pages potentially available for dirty |
| * page cache. This is the base value for the per-node dirty limits. |
| */ |
| static unsigned long node_dirtyable_memory(struct pglist_data *pgdat) |
| { |
| unsigned long nr_pages = 0; |
| int z; |
| |
| for (z = 0; z < MAX_NR_ZONES; z++) { |
| struct zone *zone = pgdat->node_zones + z; |
| |
| if (!populated_zone(zone)) |
| continue; |
| |
| nr_pages += zone_page_state(zone, NR_FREE_PAGES); |
| } |
| |
| /* |
| * Pages reserved for the kernel should not be considered |
| * dirtyable, to prevent a situation where reclaim has to |
| * clean pages in order to balance the zones. |
| */ |
| nr_pages -= min(nr_pages, pgdat->totalreserve_pages); |
| |
| nr_pages += node_page_state(pgdat, NR_INACTIVE_FILE); |
| nr_pages += node_page_state(pgdat, NR_ACTIVE_FILE); |
| |
| return nr_pages; |
| } |
| |
| static unsigned long highmem_dirtyable_memory(unsigned long total) |
| { |
| #ifdef CONFIG_HIGHMEM |
| int node; |
| unsigned long x = 0; |
| int i; |
| |
| for_each_node_state(node, N_HIGH_MEMORY) { |
| for (i = ZONE_NORMAL + 1; i < MAX_NR_ZONES; i++) { |
| struct zone *z; |
| unsigned long nr_pages; |
| |
| if (!is_highmem_idx(i)) |
| continue; |
| |
| z = &NODE_DATA(node)->node_zones[i]; |
| if (!populated_zone(z)) |
| continue; |
| |
| nr_pages = zone_page_state(z, NR_FREE_PAGES); |
| /* watch for underflows */ |
| nr_pages -= min(nr_pages, high_wmark_pages(z)); |
| nr_pages += zone_page_state(z, NR_ZONE_INACTIVE_FILE); |
| nr_pages += zone_page_state(z, NR_ZONE_ACTIVE_FILE); |
| x += nr_pages; |
| } |
| } |
| |
| /* |
| * Unreclaimable memory (kernel memory or anonymous memory |
| * without swap) can bring down the dirtyable pages below |
| * the zone's dirty balance reserve and the above calculation |
| * will underflow. However we still want to add in nodes |
| * which are below threshold (negative values) to get a more |
| * accurate calculation but make sure that the total never |
| * underflows. |
| */ |
| if ((long)x < 0) |
| x = 0; |
| |
| /* |
| * Make sure that the number of highmem pages is never larger |
| * than the number of the total dirtyable memory. This can only |
| * occur in very strange VM situations but we want to make sure |
| * that this does not occur. |
| */ |
| return min(x, total); |
| #else |
| return 0; |
| #endif |
| } |
| |
| /** |
| * global_dirtyable_memory - number of globally dirtyable pages |
| * |
| * Returns the global number of pages potentially available for dirty |
| * page cache. This is the base value for the global dirty limits. |
| */ |
| static unsigned long global_dirtyable_memory(void) |
| { |
| unsigned long x; |
| |
| x = global_zone_page_state(NR_FREE_PAGES); |
| /* |
| * Pages reserved for the kernel should not be considered |
| * dirtyable, to prevent a situation where reclaim has to |
| * clean pages in order to balance the zones. |
| */ |
| x -= min(x, totalreserve_pages); |
| |
| x += global_node_page_state(NR_INACTIVE_FILE); |
| x += global_node_page_state(NR_ACTIVE_FILE); |
| |
| if (!vm_highmem_is_dirtyable) |
| x -= highmem_dirtyable_memory(x); |
| |
| return x + 1; /* Ensure that we never return 0 */ |
| } |
| |
| /** |
| * domain_dirty_limits - calculate thresh and bg_thresh for a wb_domain |
| * @dtc: dirty_throttle_control of interest |
| * |
| * Calculate @dtc->thresh and ->bg_thresh considering |
| * vm_dirty_{bytes|ratio} and dirty_background_{bytes|ratio}. The caller |
| * must ensure that @dtc->avail is set before calling this function. The |
| * dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and |
| * real-time tasks. |
| */ |
| static void domain_dirty_limits(struct dirty_throttle_control *dtc) |
| { |
| const unsigned long available_memory = dtc->avail; |
| struct dirty_throttle_control *gdtc = mdtc_gdtc(dtc); |
| unsigned long bytes = vm_dirty_bytes; |
| unsigned long bg_bytes = dirty_background_bytes; |
| /* convert ratios to per-PAGE_SIZE for higher precision */ |
| unsigned long ratio = (vm_dirty_ratio * PAGE_SIZE) / 100; |
| unsigned long bg_ratio = (dirty_background_ratio * PAGE_SIZE) / 100; |
| unsigned long thresh; |
| unsigned long bg_thresh; |
| struct task_struct *tsk; |
| |
| /* gdtc is !NULL iff @dtc is for memcg domain */ |
| if (gdtc) { |
| unsigned long global_avail = gdtc->avail; |
| |
| /* |
| * The byte settings can't be applied directly to memcg |
| * domains. Convert them to ratios by scaling against |
| * globally available memory. As the ratios are in |
| * per-PAGE_SIZE, they can be obtained by dividing bytes by |
| * number of pages. |
| */ |
| if (bytes) |
| ratio = min(DIV_ROUND_UP(bytes, global_avail), |
| PAGE_SIZE); |
| if (bg_bytes) |
| bg_ratio = min(DIV_ROUND_UP(bg_bytes, global_avail), |
| PAGE_SIZE); |
| bytes = bg_bytes = 0; |
| } |
| |
| if (bytes) |
| thresh = DIV_ROUND_UP(bytes, PAGE_SIZE); |
| else |
| thresh = (ratio * available_memory) / PAGE_SIZE; |
| |
| if (bg_bytes) |
| bg_thresh = DIV_ROUND_UP(bg_bytes, PAGE_SIZE); |
| else |
| bg_thresh = (bg_ratio * available_memory) / PAGE_SIZE; |
| |
| if (bg_thresh >= thresh) |
| bg_thresh = thresh / 2; |
| tsk = current; |
| if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { |
| bg_thresh += bg_thresh / 4 + global_wb_domain.dirty_limit / 32; |
| thresh += thresh / 4 + global_wb_domain.dirty_limit / 32; |
| } |
| dtc->thresh = thresh; |
| dtc->bg_thresh = bg_thresh; |
| |
| /* we should eventually report the domain in the TP */ |
| if (!gdtc) |
| trace_global_dirty_state(bg_thresh, thresh); |
| } |
| |
| /** |
| * global_dirty_limits - background-writeback and dirty-throttling thresholds |
| * @pbackground: out parameter for bg_thresh |
| * @pdirty: out parameter for thresh |
| * |
| * Calculate bg_thresh and thresh for global_wb_domain. See |
| * domain_dirty_limits() for details. |
| */ |
| void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) |
| { |
| struct dirty_throttle_control gdtc = { GDTC_INIT_NO_WB }; |
| |
| gdtc.avail = global_dirtyable_memory(); |
| domain_dirty_limits(&gdtc); |
| |
| *pbackground = gdtc.bg_thresh; |
| *pdirty = gdtc.thresh; |
| } |
| |
| /** |
| * node_dirty_limit - maximum number of dirty pages allowed in a node |
| * @pgdat: the node |
| * |
| * Returns the maximum number of dirty pages allowed in a node, based |
| * on the node's dirtyable memory. |
| */ |
| static unsigned long node_dirty_limit(struct pglist_data *pgdat) |
| { |
| unsigned long node_memory = node_dirtyable_memory(pgdat); |
| struct task_struct *tsk = current; |
| unsigned long dirty; |
| |
| if (vm_dirty_bytes) |
| dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE) * |
| node_memory / global_dirtyable_memory(); |
| else |
| dirty = vm_dirty_ratio * node_memory / 100; |
| |
| if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) |
| dirty += dirty / 4; |
| |
| return dirty; |
| } |
| |
| /** |
| * node_dirty_ok - tells whether a node is within its dirty limits |
| * @pgdat: the node to check |
| * |
| * Returns %true when the dirty pages in @pgdat are within the node's |
| * dirty limit, %false if the limit is exceeded. |
| */ |
| bool node_dirty_ok(struct pglist_data *pgdat) |
| { |
| unsigned long limit = node_dirty_limit(pgdat); |
| unsigned long nr_pages = 0; |
| |
| nr_pages += node_page_state(pgdat, NR_FILE_DIRTY); |
| nr_pages += node_page_state(pgdat, NR_UNSTABLE_NFS); |
| nr_pages += node_page_state(pgdat, NR_WRITEBACK); |
| |
| return nr_pages <= limit; |
| } |
| |
| 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) { |
| writeback_set_ratelimit(); |
| 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) { |
| writeback_set_ratelimit(); |
| vm_dirty_ratio = 0; |
| } |
| return ret; |
| } |
| |
| static unsigned long wp_next_time(unsigned long cur_time) |
| { |
| cur_time += VM_COMPLETIONS_PERIOD_LEN; |
| /* 0 has a special meaning... */ |
| if (!cur_time) |
| return 1; |
| return cur_time; |
| } |
| |
| static void wb_domain_writeout_inc(struct wb_domain *dom, |
| struct fprop_local_percpu *completions, |
| unsigned int max_prop_frac) |
| { |
| __fprop_inc_percpu_max(&dom->completions, completions, |
| max_prop_frac); |
| /* First event after period switching was turned off? */ |
| if (unlikely(!dom->period_time)) { |
| /* |
| * We can race with other __bdi_writeout_inc calls here but |
| * it does not cause any harm since the resulting time when |
| * timer will fire and what is in writeout_period_time will be |
| * roughly the same. |
| */ |
| dom->period_time = wp_next_time(jiffies); |
| mod_timer(&dom->period_timer, dom->period_time); |
| } |
| } |
| |
| /* |
| * Increment @wb's writeout completion count and the global writeout |
| * completion count. Called from test_clear_page_writeback(). |
| */ |
| static inline void __wb_writeout_inc(struct bdi_writeback *wb) |
| { |
| struct wb_domain *cgdom; |
| |
| inc_wb_stat(wb, WB_WRITTEN); |
| wb_domain_writeout_inc(&global_wb_domain, &wb->completions, |
| wb->bdi->max_prop_frac); |
| |
| cgdom = mem_cgroup_wb_domain(wb); |
| if (cgdom) |
| wb_domain_writeout_inc(cgdom, wb_memcg_completions(wb), |
| wb->bdi->max_prop_frac); |
| } |
| |
| void wb_writeout_inc(struct bdi_writeback *wb) |
| { |
| unsigned long flags; |
| |
| local_irq_save(flags); |
| __wb_writeout_inc(wb); |
| local_irq_restore(flags); |
| } |
| EXPORT_SYMBOL_GPL(wb_writeout_inc); |
| |
| /* |
| * On idle system, we can be called long after we scheduled because we use |
| * deferred timers so count with missed periods. |
| */ |
| static void writeout_period(unsigned long t) |
| { |
| struct wb_domain *dom = (void *)t; |
| int miss_periods = (jiffies - dom->period_time) / |
| VM_COMPLETIONS_PERIOD_LEN; |
| |
| if (fprop_new_period(&dom->completions, miss_periods + 1)) { |
| dom->period_time = wp_next_time(dom->period_time + |
| miss_periods * VM_COMPLETIONS_PERIOD_LEN); |
| mod_timer(&dom->period_timer, dom->period_time); |
| } else { |
| /* |
| * Aging has zeroed all fractions. Stop wasting CPU on period |
| * updates. |
| */ |
| dom->period_time = 0; |
| } |
| } |
| |
| int wb_domain_init(struct wb_domain *dom, gfp_t gfp) |
| { |
| memset(dom, 0, sizeof(*dom)); |
| |
| spin_lock_init(&dom->lock); |
| |
| setup_deferrable_timer(&dom->period_timer, writeout_period, |
| (unsigned long)dom); |
| |
| dom->dirty_limit_tstamp = jiffies; |
| |
| return fprop_global_init(&dom->completions, gfp); |
| } |
| |
| #ifdef CONFIG_CGROUP_WRITEBACK |
| void wb_domain_exit(struct wb_domain *dom) |
| { |
| del_timer_sync(&dom->period_timer); |
| fprop_global_destroy(&dom->completions); |
| } |
| #endif |
| |
| /* |
| * bdi_min_ratio keeps the sum of the minimum dirty shares of all |
| * registered backing devices, which, for obvious reasons, can not |
| * exceed 100%. |
| */ |
| 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 = (FPROP_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(struct wb_domain *dom, |
| unsigned long thresh) |
| { |
| return max(thresh, dom->dirty_limit); |
| } |
| |
| /* |
| * Memory which can be further allocated to a memcg domain is capped by |
| * system-wide clean memory excluding the amount being used in the domain. |
| */ |
| static void mdtc_calc_avail(struct dirty_throttle_control *mdtc, |
| unsigned long filepages, unsigned long headroom) |
| { |
| struct dirty_throttle_control *gdtc = mdtc_gdtc(mdtc); |
| unsigned long clean = filepages - min(filepages, mdtc->dirty); |
| unsigned long global_clean = gdtc->avail - min(gdtc->avail, gdtc->dirty); |
| unsigned long other_clean = global_clean - min(global_clean, clean); |
| |
| mdtc->avail = filepages + min(headroom, other_clean); |
| } |
| |
| /** |
| * __wb_calc_thresh - @wb's share of dirty throttling threshold |
| * @dtc: dirty_throttle_context of interest |
| * |
| * Returns @wb's dirty limit in pages. The term "dirty" in the context of |
| * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages. |
| * |
| * Note that balance_dirty_pages() will only seriously take it as a hard limit |
| * when sleeping max_pause per page is not enough to keep the dirty pages under |
| * control. For example, when the device is completely stalled due to some error |
| * conditions, or when there are 1000 dd tasks writing to a slow 10MB/s USB key. |
| * In the other normal situations, it acts more gently by throttling the tasks |
| * more (rather than completely block them) when the wb dirty pages go high. |
| * |
| * It allocates high/low dirty limits to fast/slow devices, in order to prevent |
| * - starving fast devices |
| * - piling up dirty pages (that will take long time to sync) on slow devices |
| * |
| * The wb's share of dirty limit will be adapting to its throughput and |
| * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set. |
| */ |
| static unsigned long __wb_calc_thresh(struct dirty_throttle_control *dtc) |
| { |
| struct wb_domain *dom = dtc_dom(dtc); |
| unsigned long thresh = dtc->thresh; |
| u64 wb_thresh; |
| long numerator, denominator; |
| unsigned long wb_min_ratio, wb_max_ratio; |
| |
| /* |
| * Calculate this BDI's share of the thresh ratio. |
| */ |
| fprop_fraction_percpu(&dom->completions, dtc->wb_completions, |
| &numerator, &denominator); |
| |
| wb_thresh = (thresh * (100 - bdi_min_ratio)) / 100; |
| wb_thresh *= numerator; |
| do_div(wb_thresh, denominator); |
| |
| wb_min_max_ratio(dtc->wb, &wb_min_ratio, &wb_max_ratio); |
| |
| wb_thresh += (thresh * wb_min_ratio) / 100; |
| if (wb_thresh > (thresh * wb_max_ratio) / 100) |
| wb_thresh = thresh * wb_max_ratio / 100; |
| |
| return wb_thresh; |
| } |
| |
| unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh) |
| { |
| struct dirty_throttle_control gdtc = { GDTC_INIT(wb), |
| .thresh = thresh }; |
| return __wb_calc_thresh(&gdtc); |
| } |
| |
| /* |
| * setpoint - dirty 3 |
| * f(dirty) := 1.0 + (----------------) |
| * limit - setpoint |
| * |
| * it's a 3rd order polynomial that subjects to |
| * |
| * (1) f(freerun) = 2.0 => rampup dirty_ratelimit reasonably fast |
| * (2) f(setpoint) = 1.0 => the balance point |
| * (3) f(limit) = 0 => the hard limit |
| * (4) df/dx <= 0 => negative feedback control |
| * (5) the closer to setpoint, the smaller |df/dx| (and the reverse) |
| * => fast response on large errors; small oscillation near setpoint |
| */ |
| static long long pos_ratio_polynom(unsigned long setpoint, |
| unsigned long dirty, |
| unsigned long limit) |
| { |
| long long pos_ratio; |
| long x; |
| |
| x = div64_s64(((s64)setpoint - (s64)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; |
| |
| return clamp(pos_ratio, 0LL, 2LL << RATELIMIT_CALC_SHIFT); |
| } |
| |
| /* |
| * Dirty position control. |
| * |
| * (o) global/bdi setpoints |
| * |
| * We want the dirty pages be balanced around the global/wb setpoints. |
| * When the number of dirty pages is higher/lower than the setpoint, the |
| * dirty position control ratio (and hence task dirty ratelimit) will be |
| * decreased/increased to bring the dirty pages back to the setpoint. |
| * |
| * pos_ratio = 1 << RATELIMIT_CALC_SHIFT |
| * |
| * if (dirty < setpoint) scale up pos_ratio |
| * if (dirty > setpoint) scale down pos_ratio |
| * |
| * if (wb_dirty < wb_setpoint) scale up pos_ratio |
| * if (wb_dirty > wb_setpoint) scale down pos_ratio |
| * |
| * task_ratelimit = dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT |
| * |
| * (o) global control line |
| * |
| * ^ pos_ratio |
| * | |
| * | |<===== global dirty control scope ======>| |
| * 2.0 .............* |
| * | .* |
| * | . * |
| * | . * |
| * | . * |
| * | . * |
| * | . * |
| * 1.0 ................................* |
| * | . . * |
| * | . . * |
| * | . . * |
| * | . . * |
| * | . . * |
| * 0 +------------.------------------.----------------------*-------------> |
| * freerun^ setpoint^ limit^ dirty pages |
| * |
| * (o) wb control line |
| * |
| * ^ pos_ratio |
| * | |
| * | * |
| * | * |
| * | * |
| * | * |
| * | * |<=========== span ============>| |
| * 1.0 .......................* |
| * | . * |
| * | . * |
| * | . * |
| * | . * |
| * | . * |
| * | . * |
| * | . * |
| * | . * |
| * | . * |
| * | . * |
| * | . * |
| * 1/4 ...............................................* * * * * * * * * * * * |
| * | . . |
| * | . . |
| * | . . |
| * 0 +----------------------.-------------------------------.-------------> |
| * wb_setpoint^ x_intercept^ |
| * |
| * The wb control line won't drop below pos_ratio=1/4, so that wb_dirty can |
| * be smoothly throttled down to normal if it starts high in situations like |
| * - start writing to a slow SD card and a fast disk at the same time. The SD |
| * card's wb_dirty may rush to many times higher than wb_setpoint. |
| * - the wb dirty thresh drops quickly due to change of JBOD workload |
| */ |
| static void wb_position_ratio(struct dirty_throttle_control *dtc) |
| { |
| struct bdi_writeback *wb = dtc->wb; |
| unsigned long write_bw = wb->avg_write_bandwidth; |
| unsigned long freerun = dirty_freerun_ceiling(dtc->thresh, dtc->bg_thresh); |
| unsigned long limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh); |
| unsigned long wb_thresh = dtc->wb_thresh; |
| unsigned long x_intercept; |
| unsigned long setpoint; /* dirty pages' target balance point */ |
| unsigned long wb_setpoint; |
| unsigned long span; |
| long long pos_ratio; /* for scaling up/down the rate limit */ |
| long x; |
| |
| dtc->pos_ratio = 0; |
| |
| if (unlikely(dtc->dirty >= limit)) |
| return; |
| |
| /* |
| * global setpoint |
| * |
| * See comment for pos_ratio_polynom(). |
| */ |
| setpoint = (freerun + limit) / 2; |
| pos_ratio = pos_ratio_polynom(setpoint, dtc->dirty, limit); |
| |
| /* |
| * The strictlimit feature is a tool preventing mistrusted filesystems |
| * from growing a large number of dirty pages before throttling. For |
| * such filesystems balance_dirty_pages always checks wb counters |
| * against wb limits. Even if global "nr_dirty" is under "freerun". |
| * This is especially important for fuse which sets bdi->max_ratio to |
| * 1% by default. Without strictlimit feature, fuse writeback may |
| * consume arbitrary amount of RAM because it is accounted in |
| * NR_WRITEBACK_TEMP which is not involved in calculating "nr_dirty". |
| * |
| * Here, in wb_position_ratio(), we calculate pos_ratio based on |
| * two values: wb_dirty and wb_thresh. Let's consider an example: |
| * total amount of RAM is 16GB, bdi->max_ratio is equal to 1%, global |
| * limits are set by default to 10% and 20% (background and throttle). |
| * Then wb_thresh is 1% of 20% of 16GB. This amounts to ~8K pages. |
| * wb_calc_thresh(wb, bg_thresh) is about ~4K pages. wb_setpoint is |
| * about ~6K pages (as the average of background and throttle wb |
| * limits). The 3rd order polynomial will provide positive feedback if |
| * wb_dirty is under wb_setpoint and vice versa. |
| * |
| * Note, that we cannot use global counters in these calculations |
| * because we want to throttle process writing to a strictlimit wb |
| * much earlier than global "freerun" is reached (~23MB vs. ~2.3GB |
| * in the example above). |
| */ |
| if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { |
| long long wb_pos_ratio; |
| |
| if (dtc->wb_dirty < 8) { |
| dtc->pos_ratio = min_t(long long, pos_ratio * 2, |
| 2 << RATELIMIT_CALC_SHIFT); |
| return; |
| } |
| |
| if (dtc->wb_dirty >= wb_thresh) |
| return; |
| |
| wb_setpoint = dirty_freerun_ceiling(wb_thresh, |
| dtc->wb_bg_thresh); |
| |
| if (wb_setpoint == 0 || wb_setpoint == wb_thresh) |
| return; |
| |
| wb_pos_ratio = pos_ratio_polynom(wb_setpoint, dtc->wb_dirty, |
| wb_thresh); |
| |
| /* |
| * Typically, for strictlimit case, wb_setpoint << setpoint |
| * and pos_ratio >> wb_pos_ratio. In the other words global |
| * state ("dirty") is not limiting factor and we have to |
| * make decision based on wb counters. But there is an |
| * important case when global pos_ratio should get precedence: |
| * global limits are exceeded (e.g. due to activities on other |
| * wb's) while given strictlimit wb is below limit. |
| * |
| * "pos_ratio * wb_pos_ratio" would work for the case above, |
| * but it would look too non-natural for the case of all |
| * activity in the system coming from a single strictlimit wb |
| * with bdi->max_ratio == 100%. |
| * |
| * Note that min() below somewhat changes the dynamics of the |
| * control system. Normally, pos_ratio value can be well over 3 |
| * (when globally we are at freerun and wb is well below wb |
| * setpoint). Now the maximum pos_ratio in the same situation |
| * is 2. We might want to tweak this if we observe the control |
| * system is too slow to adapt. |
| */ |
| dtc->pos_ratio = min(pos_ratio, wb_pos_ratio); |
| return; |
| } |
| |
| /* |
| * We have computed basic pos_ratio above based on global situation. If |
| * the wb is over/under its share of dirty pages, we want to scale |
| * pos_ratio further down/up. That is done by the following mechanism. |
| */ |
| |
| /* |
| * wb setpoint |
| * |
| * f(wb_dirty) := 1.0 + k * (wb_dirty - wb_setpoint) |
| * |
| * x_intercept - wb_dirty |
| * := -------------------------- |
| * x_intercept - wb_setpoint |
| * |
| * The main wb control line is a linear function that subjects to |
| * |
| * (1) f(wb_setpoint) = 1.0 |
| * (2) k = - 1 / (8 * write_bw) (in single wb case) |
| * or equally: x_intercept = wb_setpoint + 8 * write_bw |
| * |
| * For single wb case, the dirty pages are observed to fluctuate |
| * regularly within range |
| * [wb_setpoint - write_bw/2, wb_setpoint + write_bw/2] |
| * for various filesystems, where (2) can yield in a reasonable 12.5% |
| * fluctuation range for pos_ratio. |
| * |
| * For JBOD case, wb_thresh (not wb_dirty!) could fluctuate up to its |
| * own size, so move the slope over accordingly and choose a slope that |
| * yields 100% pos_ratio fluctuation on suddenly doubled wb_thresh. |
| */ |
| if (unlikely(wb_thresh > dtc->thresh)) |
| wb_thresh = dtc->thresh; |
| /* |
| * It's very possible that wb_thresh is close to 0 not because the |
| * device is slow, but that it has remained inactive for long time. |
| * Honour such devices a reasonable good (hopefully IO efficient) |
| * threshold, so that the occasional writes won't be blocked and active |
| * writes can rampup the threshold quickly. |
| */ |
| wb_thresh = max(wb_thresh, (limit - dtc->dirty) / 8); |
| /* |
| * scale global setpoint to wb's: |
| * wb_setpoint = setpoint * wb_thresh / thresh |
| */ |
| x = div_u64((u64)wb_thresh << 16, dtc->thresh | 1); |
| wb_setpoint = setpoint * (u64)x >> 16; |
| /* |
| * Use span=(8*write_bw) in single wb case as indicated by |
| * (thresh - wb_thresh ~= 0) and transit to wb_thresh in JBOD case. |
| * |
| * wb_thresh thresh - wb_thresh |
| * span = --------- * (8 * write_bw) + ------------------ * wb_thresh |
| * thresh thresh |
| */ |
| span = (dtc->thresh - wb_thresh + 8 * write_bw) * (u64)x >> 16; |
| x_intercept = wb_setpoint + span; |
| |
| if (dtc->wb_dirty < x_intercept - span / 4) { |
| pos_ratio = div64_u64(pos_ratio * (x_intercept - dtc->wb_dirty), |
| (x_intercept - wb_setpoint) | 1); |
| } else |
| pos_ratio /= 4; |
| |
| /* |
| * wb reserve area, safeguard against dirty pool underrun and disk idle |
| * It may push the desired control point of global dirty pages higher |
| * than setpoint. |
| */ |
| x_intercept = wb_thresh / 2; |
| if (dtc->wb_dirty < x_intercept) { |
| if (dtc->wb_dirty > x_intercept / 8) |
| pos_ratio = div_u64(pos_ratio * x_intercept, |
| dtc->wb_dirty); |
| else |
| pos_ratio *= 8; |
| } |
| |
| dtc->pos_ratio = pos_ratio; |
| } |
| |
| static void wb_update_write_bandwidth(struct bdi_writeback *wb, |
| unsigned long elapsed, |
| unsigned long written) |
| { |
| const unsigned long period = roundup_pow_of_two(3 * HZ); |
| unsigned long avg = wb->avg_write_bandwidth; |
| unsigned long old = wb->write_bandwidth; |
| u64 bw; |
| |
| /* |
| * bw = written * HZ / elapsed |
| * |
| * bw * elapsed + write_bandwidth * (period - elapsed) |
| * write_bandwidth = --------------------------------------------------- |
| * period |
| * |
| * @written may have decreased due to account_page_redirty(). |
| * Avoid underflowing @bw calculation. |
| */ |
| bw = written - min(written, wb->written_stamp); |
| bw *= HZ; |
| if (unlikely(elapsed > period)) { |
| do_div(bw, elapsed); |
| avg = bw; |
| goto out; |
| } |
| bw += (u64)wb->write_bandwidth * (period - elapsed); |
| bw >>= ilog2(period); |
| |
| /* |
| * one more level of smoothing, for filtering out sudden spikes |
| */ |
| if (avg > old && old >= (unsigned long)bw) |
| avg -= (avg - old) >> 3; |
| |
| if (avg < old && old <= (unsigned long)bw) |
| avg += (old - avg) >> 3; |
| |
| out: |
| /* keep avg > 0 to guarantee that tot > 0 if there are dirty wbs */ |
| avg = max(avg, 1LU); |
| if (wb_has_dirty_io(wb)) { |
| long delta = avg - wb->avg_write_bandwidth; |
| WARN_ON_ONCE(atomic_long_add_return(delta, |
| &wb->bdi->tot_write_bandwidth) <= 0); |
| } |
| wb->write_bandwidth = bw; |
| wb->avg_write_bandwidth = avg; |
| } |
| |
| static void update_dirty_limit(struct dirty_throttle_control *dtc) |
| { |
| struct wb_domain *dom = dtc_dom(dtc); |
| unsigned long thresh = dtc->thresh; |
| unsigned long limit = dom->dirty_limit; |
| |
| /* |
| * Follow up in one step. |
| */ |
| if (limit < thresh) { |
| limit = thresh; |
| goto update; |
| } |
| |
| /* |
| * Follow down slowly. Use the higher one as the target, because thresh |
| * may drop below dirty. This is exactly the reason to introduce |
| * dom->dirty_limit which is guaranteed to lie above the dirty pages. |
| */ |
| thresh = max(thresh, dtc->dirty); |
| if (limit > thresh) { |
| limit -= (limit - thresh) >> 5; |
| goto update; |
| } |
| return; |
| update: |
| dom->dirty_limit = limit; |
| } |
| |
| static void domain_update_bandwidth(struct dirty_throttle_control *dtc, |
| unsigned long now) |
| { |
| struct wb_domain *dom = dtc_dom(dtc); |
| |
| /* |
| * check locklessly first to optimize away locking for the most time |
| */ |
| if (time_before(now, dom->dirty_limit_tstamp + BANDWIDTH_INTERVAL)) |
| return; |
| |
| spin_lock(&dom->lock); |
| if (time_after_eq(now, dom->dirty_limit_tstamp + BANDWIDTH_INTERVAL)) { |
| update_dirty_limit(dtc); |
| dom->dirty_limit_tstamp = now; |
| } |
| spin_unlock(&dom->lock); |
| } |
| |
| /* |
| * Maintain wb->dirty_ratelimit, the base dirty throttle rate. |
| * |
| * Normal wb tasks will be curbed at or below it in long term. |
| * Obviously it should be around (write_bw / N) when there are N dd tasks. |
| */ |
| static void wb_update_dirty_ratelimit(struct dirty_throttle_control *dtc, |
| unsigned long dirtied, |
| unsigned long elapsed) |
| { |
| struct bdi_writeback *wb = dtc->wb; |
| unsigned long dirty = dtc->dirty; |
| unsigned long freerun = dirty_freerun_ceiling(dtc->thresh, dtc->bg_thresh); |
| unsigned long limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh); |
| unsigned long setpoint = (freerun + limit) / 2; |
| unsigned long write_bw = wb->avg_write_bandwidth; |
| unsigned long dirty_ratelimit = wb->dirty_ratelimit; |
| unsigned long dirty_rate; |
| unsigned long task_ratelimit; |
| unsigned long balanced_dirty_ratelimit; |
| unsigned long step; |
| unsigned long x; |
| unsigned long shift; |
| |
| /* |
| * The dirty rate will match the writeout rate in long term, except |
| * when dirty pages are truncated by userspace or re-dirtied by FS. |
| */ |
| dirty_rate = (dirtied - wb->dirtied_stamp) * HZ / elapsed; |
| |
| /* |
| * task_ratelimit reflects each dd's dirty rate for the past 200ms. |
| */ |
| task_ratelimit = (u64)dirty_ratelimit * |
| dtc->pos_ratio >> RATELIMIT_CALC_SHIFT; |
| task_ratelimit++; /* it helps rampup dirty_ratelimit from tiny values */ |
| |
| /* |
| * A linear estimation of the "balanced" throttle rate. The theory is, |
| * if there are N dd tasks, each throttled at task_ratelimit, the wb's |
| * dirty_rate will be measured to be (N * task_ratelimit). So the below |
| * formula will yield the balanced rate limit (write_bw / N). |
| * |
| * Note that the expanded form is not a pure rate feedback: |
| * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) (1) |
| * but also takes pos_ratio into account: |
| * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) * pos_ratio (2) |
| * |
| * (1) is not realistic because pos_ratio also takes part in balancing |
| * the dirty rate. Consider the state |
| * pos_ratio = 0.5 (3) |
| * rate = 2 * (write_bw / N) (4) |
| * If (1) is used, it will stuck in that state! Because each dd will |
| * be throttled at |
| * task_ratelimit = pos_ratio * rate = (write_bw / N) (5) |
| * yielding |
| * dirty_rate = N * task_ratelimit = write_bw (6) |
| * put (6) into (1) we get |
| * rate_(i+1) = rate_(i) (7) |
| * |
| * So we end up using (2) to always keep |
| * rate_(i+1) ~= (write_bw / N) (8) |
| * regardless of the value of pos_ratio. As long as (8) is satisfied, |
| * pos_ratio is able to drive itself to 1.0, which is not only where |
| * the dirty count meet the setpoint, but also where the slope of |
| * pos_ratio is most flat and hence task_ratelimit is least fluctuated. |
| */ |
| balanced_dirty_ratelimit = div_u64((u64)task_ratelimit * write_bw, |
| dirty_rate | 1); |
| /* |
| * balanced_dirty_ratelimit ~= (write_bw / N) <= write_bw |
| */ |
| if (unlikely(balanced_dirty_ratelimit > write_bw)) |
| balanced_dirty_ratelimit = write_bw; |
| |
| /* |
| * We could safely do this and return immediately: |
| * |
| * wb->dirty_ratelimit = balanced_dirty_ratelimit; |
| * |
| * However to get a more stable dirty_ratelimit, the below elaborated |
| * code makes use of task_ratelimit to filter out singular points and |
| * limit the step size. |
| * |
| * The below code essentially only uses the relative value of |
| * |
| * task_ratelimit - dirty_ratelimit |
| * = (pos_ratio - 1) * dirty_ratelimit |
| * |
| * which reflects the direction and size of dirty position error. |
| */ |
| |
| /* |
| * dirty_ratelimit will follow balanced_dirty_ratelimit iff |
| * task_ratelimit is on the same side of dirty_ratelimit, too. |
| * For example, when |
| * - dirty_ratelimit > balanced_dirty_ratelimit |
| * - dirty_ratelimit > task_ratelimit (dirty pages are above setpoint) |
| * lowering dirty_ratelimit will help meet both the position and rate |
| * control targets. Otherwise, don't update dirty_ratelimit if it will |
| * only help meet the rate target. After all, what the users ultimately |
| * feel and care are stable dirty rate and small position error. |
| * |
| * |task_ratelimit - dirty_ratelimit| is used to limit the step size |
| * and filter out the singular points of balanced_dirty_ratelimit. Which |
| * keeps jumping around randomly and can even leap far away at times |
| * due to the small 200ms estimation period of dirty_rate (we want to |
| * keep that period small to reduce time lags). |
| */ |
| step = 0; |
| |
| /* |
| * For strictlimit case, calculations above were based on wb counters |
| * and limits (starting from pos_ratio = wb_position_ratio() and up to |
| * balanced_dirty_ratelimit = task_ratelimit * write_bw / dirty_rate). |
| * Hence, to calculate "step" properly, we have to use wb_dirty as |
| * "dirty" and wb_setpoint as "setpoint". |
| * |
| * We rampup dirty_ratelimit forcibly if wb_dirty is low because |
| * it's possible that wb_thresh is close to zero due to inactivity |
| * of backing device. |
| */ |
| if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { |
| dirty = dtc->wb_dirty; |
| if (dtc->wb_dirty < 8) |
| setpoint = dtc->wb_dirty + 1; |
| else |
| setpoint = (dtc->wb_thresh + dtc->wb_bg_thresh) / 2; |
| } |
| |
| if (dirty < setpoint) { |
| x = min3(wb->balanced_dirty_ratelimit, |
| balanced_dirty_ratelimit, task_ratelimit); |
| if (dirty_ratelimit < x) |
| step = x - dirty_ratelimit; |
| } else { |
| x = max3(wb->balanced_dirty_ratelimit, |
| balanced_dirty_ratelimit, task_ratelimit); |
| if (dirty_ratelimit > x) |
| step = dirty_ratelimit - x; |
| } |
| |
| /* |
| * Don't pursue 100% rate matching. It's impossible since the balanced |
| * rate itself is constantly fluctuating. So decrease the track speed |
| * when it gets close to the target. Helps eliminate pointless tremors. |
| */ |
| shift = dirty_ratelimit / (2 * step + 1); |
| if (shift < BITS_PER_LONG) |
| step = DIV_ROUND_UP(step >> shift, 8); |
| else |
| step = 0; |
| |
| if (dirty_ratelimit < balanced_dirty_ratelimit) |
| dirty_ratelimit += step; |
| else |
| dirty_ratelimit -= step; |
| |
| wb->dirty_ratelimit = max(dirty_ratelimit, 1UL); |
| wb->balanced_dirty_ratelimit = balanced_dirty_ratelimit; |
| |
| trace_bdi_dirty_ratelimit(wb, dirty_rate, task_ratelimit); |
| } |
| |
| static void __wb_update_bandwidth(struct dirty_throttle_control *gdtc, |
| struct dirty_throttle_control *mdtc, |
| unsigned long start_time, |
| bool update_ratelimit) |
| { |
| struct bdi_writeback *wb = gdtc->wb; |
| unsigned long now = jiffies; |
| unsigned long elapsed = now - wb->bw_time_stamp; |
| unsigned long dirtied; |
| unsigned long written; |
| |
| lockdep_assert_held(&wb->list_lock); |
| |
| /* |
| * rate-limit, only update once every 200ms. |
| */ |
| if (elapsed < BANDWIDTH_INTERVAL) |
| return; |
| |
| dirtied = percpu_counter_read(&wb->stat[WB_DIRTIED]); |
| written = percpu_counter_read(&wb->stat[WB_WRITTEN]); |
| |
| /* |
| * Skip quiet periods when disk bandwidth is under-utilized. |
| * (at least 1s idle time between two flusher runs) |
| */ |
| if (elapsed > HZ && time_before(wb->bw_time_stamp, start_time)) |
| goto snapshot; |
| |
| if (update_ratelimit) { |
| domain_update_bandwidth(gdtc, now); |
| wb_update_dirty_ratelimit(gdtc, dirtied, elapsed); |
| |
| /* |
| * @mdtc is always NULL if !CGROUP_WRITEBACK but the |
| * compiler has no way to figure that out. Help it. |
| */ |
| if (IS_ENABLED(CONFIG_CGROUP_WRITEBACK) && mdtc) { |
| domain_update_bandwidth(mdtc, now); |
| wb_update_dirty_ratelimit(mdtc, dirtied, elapsed); |
| } |
| } |
| wb_update_write_bandwidth(wb, elapsed, written); |
| |
| snapshot: |
| wb->dirtied_stamp = dirtied; |
| wb->written_stamp = written; |
| wb->bw_time_stamp = now; |
| } |
| |
| void wb_update_bandwidth(struct bdi_writeback *wb, unsigned long start_time) |
| { |
| struct dirty_throttle_control gdtc = { GDTC_INIT(wb) }; |
| |
| __wb_update_bandwidth(&gdtc, NULL, start_time, false); |
| } |
| |
| /* |
| * After a task dirtied this many pages, balance_dirty_pages_ratelimited() |
| * will look to see if it needs to start dirty throttling. |
| * |
| * If dirty_poll_interval is too low, big NUMA machines will call the expensive |
| * global_zone_page_state() too often. So scale it near-sqrt to the safety margin |
| * (the number of pages we may dirty without exceeding the dirty limits). |
| */ |
| static unsigned long dirty_poll_interval(unsigned long dirty, |
| unsigned long thresh) |
| { |
| if (thresh > dirty) |
| return 1UL << (ilog2(thresh - dirty) >> 1); |
| |
| return 1; |
| } |
| |
| static unsigned long wb_max_pause(struct bdi_writeback *wb, |
| unsigned long wb_dirty) |
| { |
| unsigned long bw = wb->avg_write_bandwidth; |
| unsigned long t; |
| |
| /* |
| * Limit pause time for small memory systems. If sleeping for too long |
| * time, a small pool of dirty/writeback pages may go empty and disk go |
| * idle. |
| * |
| * 8 serves as the safety ratio. |
| */ |
| t = wb_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8)); |
| t++; |
| |
| return min_t(unsigned long, t, MAX_PAUSE); |
| } |
| |
| static long wb_min_pause(struct bdi_writeback *wb, |
| long max_pause, |
| unsigned long task_ratelimit, |
| unsigned long dirty_ratelimit, |
| int *nr_dirtied_pause) |
| { |
| long hi = ilog2(wb->avg_write_bandwidth); |
| long lo = ilog2(wb->dirty_ratelimit); |
| long t; /* target pause */ |
| long pause; /* estimated next pause */ |
| int pages; /* target nr_dirtied_pause */ |
| |
| /* target for 10ms pause on 1-dd case */ |
| t = max(1, HZ / 100); |
| |
| /* |
| * Scale up pause time for concurrent dirtiers in order to reduce CPU |
| * overheads. |
| * |
| * (N * 10ms) on 2^N concurrent tasks. |
| */ |
| if (hi > lo) |
| t += (hi - lo) * (10 * HZ) / 1024; |
| |
| /* |
| * This is a bit convoluted. We try to base the next nr_dirtied_pause |
| * on the much more stable dirty_ratelimit. However the next pause time |
| * will be computed based on task_ratelimit and the two rate limits may |
| * depart considerably at some time. Especially if task_ratelimit goes |
| * below dirty_ratelimit/2 and the target pause is max_pause, the next |
| * pause time will be max_pause*2 _trimmed down_ to max_pause. As a |
| * result task_ratelimit won't be executed faithfully, which could |
| * eventually bring down dirty_ratelimit. |
| * |
| * We apply two rules to fix it up: |
| * 1) try to estimate the next pause time and if necessary, use a lower |
| * nr_dirtied_pause so as not to exceed max_pause. When this happens, |
| * nr_dirtied_pause will be "dancing" with task_ratelimit. |
| * 2) limit the target pause time to max_pause/2, so that the normal |
| * small fluctuations of task_ratelimit won't trigger rule (1) and |
| * nr_dirtied_pause will remain as stable as dirty_ratelimit. |
| */ |
| t = min(t, 1 + max_pause / 2); |
| pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); |
| |
| /* |
| * Tiny nr_dirtied_pause is found to hurt I/O performance in the test |
| * case fio-mmap-randwrite-64k, which does 16*{sync read, async write}. |
| * When the 16 consecutive reads are often interrupted by some dirty |
| * throttling pause during the async writes, cfq will go into idles |
| * (deadline is fine). So push nr_dirtied_pause as high as possible |
| * until reaches DIRTY_POLL_THRESH=32 pages. |
| */ |
| 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; |
| /* |
| * The minimal pause time will normally be half the target pause time. |
| */ |
| return pages >= DIRTY_POLL_THRESH ? 1 + t / 2 : t; |
| } |
| |
| static inline void wb_dirty_limits(struct dirty_throttle_control *dtc) |
| { |
| struct bdi_writeback *wb = dtc->wb; |
| unsigned long wb_reclaimable; |
| |
| /* |
| * wb_thresh is not treated as some limiting factor as |
| * dirty_thresh, due to reasons |
| * - in JBOD setup, wb_thresh can fluctuate a lot |
| * - in a system with HDD and USB key, the USB key may somehow |
| * go into state (wb_dirty >> wb_thresh) either because |
| * wb_dirty starts high, or because wb_thresh drops low. |
| * In this case we don't want to hard throttle the USB key |
| * dirtiers for 100 seconds until wb_dirty drops under |
| * wb_thresh. Instead the auxiliary wb control line in |
| * wb_position_ratio() will let the dirtier task progress |
| * at some rate <= (write_bw / 2) for bringing down wb_dirty. |
| */ |
| dtc->wb_thresh = __wb_calc_thresh(dtc); |
| dtc->wb_bg_thresh = dtc->thresh ? |
| div_u64((u64)dtc->wb_thresh * dtc->bg_thresh, dtc->thresh) : 0; |
| |
| /* |
| * In order to avoid the stacked BDI deadlock we need |
| * to ensure we accurately count the 'dirty' pages when |
| * the threshold is low. |
| * |
| * Otherwise it would be possible to get thresh+n pages |
| * reported dirty, even though there are thresh-m pages |
| * actually dirty; with m+n sitting in the percpu |
| * deltas. |
| */ |
| if (dtc->wb_thresh < 2 * wb_stat_error(wb)) { |
| wb_reclaimable = wb_stat_sum(wb, WB_RECLAIMABLE); |
| dtc->wb_dirty = wb_reclaimable + wb_stat_sum(wb, WB_WRITEBACK); |
| } else { |
| wb_reclaimable = wb_stat(wb, WB_RECLAIMABLE); |
| dtc->wb_dirty = wb_reclaimable + wb_stat(wb, WB_WRITEBACK); |
| } |
| } |
| |
| /* |
| * balance_dirty_pages() must be called by processes which are generating dirty |
| * data. It looks at the number of dirty pages in the machine and will force |
| * the caller to wait once crossing the (background_thresh + dirty_thresh) / 2. |
| * If we're over `background_thresh' then the writeback threads are woken to |
| * perform some writeout. |
| */ |
| static void balance_dirty_pages(struct address_space *mapping, |
| struct bdi_writeback *wb, |
| unsigned long pages_dirtied) |
| { |
| struct dirty_throttle_control gdtc_stor = { GDTC_INIT(wb) }; |
| struct dirty_throttle_control mdtc_stor = { MDTC_INIT(wb, &gdtc_stor) }; |
| struct dirty_throttle_control * const gdtc = &gdtc_stor; |
| struct dirty_throttle_control * const mdtc = mdtc_valid(&mdtc_stor) ? |
| &mdtc_stor : NULL; |
| struct dirty_throttle_control *sdtc; |
| unsigned long nr_reclaimable; /* = file_dirty + unstable_nfs */ |
| 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; |
| struct backing_dev_info *bdi = wb->bdi; |
| bool strictlimit = bdi->capabilities & BDI_CAP_STRICTLIMIT; |
| unsigned long start_time = jiffies; |
| |
| for (;;) { |
| unsigned long now = jiffies; |
| unsigned long dirty, thresh, bg_thresh; |
| unsigned long m_dirty = 0; /* stop bogus uninit warnings */ |
| unsigned long m_thresh = 0; |
| unsigned long m_bg_thresh = 0; |
| |
| /* |
| * 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_node_page_state(NR_FILE_DIRTY) + |
| global_node_page_state(NR_UNSTABLE_NFS); |
| gdtc->avail = global_dirtyable_memory(); |
| gdtc->dirty = nr_reclaimable + global_node_page_state(NR_WRITEBACK); |
| |
| domain_dirty_limits(gdtc); |
| |
| if (unlikely(strictlimit)) { |
| wb_dirty_limits(gdtc); |
| |
| dirty = gdtc->wb_dirty; |
| thresh = gdtc->wb_thresh; |
| bg_thresh = gdtc->wb_bg_thresh; |
| } else { |
| dirty = gdtc->dirty; |
| thresh = gdtc->thresh; |
| bg_thresh = gdtc->bg_thresh; |
| } |
| |
| if (mdtc) { |
| unsigned long filepages, headroom, writeback; |
| |
| /* |
| * If @wb belongs to !root memcg, repeat the same |
| * basic calculations for the memcg domain. |
| */ |
| mem_cgroup_wb_stats(wb, &filepages, &headroom, |
| &mdtc->dirty, &writeback); |
| mdtc->dirty += writeback; |
| mdtc_calc_avail(mdtc, filepages, headroom); |
| |
| domain_dirty_limits(mdtc); |
| |
| if (unlikely(strictlimit)) { |
| wb_dirty_limits(mdtc); |
| m_dirty = mdtc->wb_dirty; |
| m_thresh = mdtc->wb_thresh; |
| m_bg_thresh = mdtc->wb_bg_thresh; |
| } else { |
| m_dirty = mdtc->dirty; |
| m_thresh = mdtc->thresh; |
| m_bg_thresh = mdtc->bg_thresh; |
| } |
| } |
| |
| /* |
| * Throttle it only when the background writeback cannot |
| * catch-up. This avoids (excessively) small writeouts |
| * when the wb limits are ramping up in case of !strictlimit. |
| * |
| * In strictlimit case make decision based on the wb counters |
| * and limits. Small writeouts when the wb limits are ramping |
| * up are the price we consciously pay for strictlimit-ing. |
| * |
| * If memcg domain is in effect, @dirty should be under |
| * both global and memcg freerun ceilings. |
| */ |
| if (dirty <= dirty_freerun_ceiling(thresh, bg_thresh) && |
| (!mdtc || |
| m_dirty <= dirty_freerun_ceiling(m_thresh, m_bg_thresh))) { |
| unsigned long intv = dirty_poll_interval(dirty, thresh); |
| unsigned long m_intv = ULONG_MAX; |
| |
| current->dirty_paused_when = now; |
| current->nr_dirtied = 0; |
| if (mdtc) |
| m_intv = dirty_poll_interval(m_dirty, m_thresh); |
| current->nr_dirtied_pause = min(intv, m_intv); |
| break; |
| } |
| |
| if (unlikely(!writeback_in_progress(wb))) |
| wb_start_background_writeback(wb); |
| |
| /* |
| * Calculate global domain's pos_ratio and select the |
| * global dtc by default. |
| */ |
| if (!strictlimit) |
| wb_dirty_limits(gdtc); |
| |
| dirty_exceeded = (gdtc->wb_dirty > gdtc->wb_thresh) && |
| ((gdtc->dirty > gdtc->thresh) || strictlimit); |
| |
| wb_position_ratio(gdtc); |
| sdtc = gdtc; |
| |
| if (mdtc) { |
| /* |
| * If memcg domain is in effect, calculate its |
| * pos_ratio. @wb should satisfy constraints from |
| * both global and memcg domains. Choose the one |
| * w/ lower pos_ratio. |
| */ |
| if (!strictlimit) |
| wb_dirty_limits(mdtc); |
| |
| dirty_exceeded |= (mdtc->wb_dirty > mdtc->wb_thresh) && |
| ((mdtc->dirty > mdtc->thresh) || strictlimit); |
| |
| wb_position_ratio(mdtc); |
| if (mdtc->pos_ratio < gdtc->pos_ratio) |
| sdtc = mdtc; |
| } |
| |
| if (dirty_exceeded && !wb->dirty_exceeded) |
| wb->dirty_exceeded = 1; |
| |
| if (time_is_before_jiffies(wb->bw_time_stamp + |
| BANDWIDTH_INTERVAL)) { |
| spin_lock(&wb->list_lock); |
| __wb_update_bandwidth(gdtc, mdtc, start_time, true); |
| spin_unlock(&wb->list_lock); |
| } |
| |
| /* throttle according to the chosen dtc */ |
| dirty_ratelimit = wb->dirty_ratelimit; |
| task_ratelimit = ((u64)dirty_ratelimit * sdtc->pos_ratio) >> |
| RATELIMIT_CALC_SHIFT; |
| max_pause = wb_max_pause(wb, sdtc->wb_dirty); |
| min_pause = wb_min_pause(wb, 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; |
| /* |
| * For less than 1s think time (ext3/4 may block the dirtier |
| * for up to 800ms from time to time on 1-HDD; so does xfs, |
| * however at much less frequency), try to compensate it in |
| * future periods by updating the virtual time; otherwise just |
| * do a reset, as it may be a light dirtier. |
| */ |
| if (pause < min_pause) { |
| trace_balance_dirty_pages(wb, |
| sdtc->thresh, |
| sdtc->bg_thresh, |
| sdtc->dirty, |
| sdtc->wb_thresh, |
| sdtc->wb_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)) { |
| /* for occasional dropped task_ratelimit */ |
| now += min(pause - max_pause, max_pause); |
| pause = max_pause; |
| } |
| |
| pause: |
| trace_balance_dirty_pages(wb, |
| sdtc->thresh, |
| sdtc->bg_thresh, |
| sdtc->dirty, |
| sdtc->wb_thresh, |
| sdtc->wb_dirty, |
| dirty_ratelimit, |
| task_ratelimit, |
| pages_dirtied, |
| period, |
| pause, |
| start_time); |
| __set_current_state(TASK_KILLABLE); |
| wb->dirty_sleep = now; |
| io_schedule_timeout(pause); |
| |
| current->dirty_paused_when = now + pause; |
| current->nr_dirtied = 0; |
| current->nr_dirtied_pause = nr_dirtied_pause; |
| |
| /* |
| * This is typically equal to (dirty < thresh) and can also |
| * keep "1000+ dd on a slow USB stick" under control. |
| */ |
| if (task_ratelimit) |
| break; |
| |
| /* |
| * In the case of an unresponding NFS server and the NFS dirty |
| * pages exceeds dirty_thresh, give the other good wb's a pipe |
| * to go through, so that tasks on them still remain responsive. |
| * |
| * In theory 1 page is enough to keep the consumer-producer |
| * pipe going: the flusher cleans 1 page => the task dirties 1 |
| * more page. However wb_dirty has accounting errors. So use |
| * the larger and more IO friendly wb_stat_error. |
| */ |
| if (sdtc->wb_dirty <= wb_stat_error(wb)) |
| break; |
| |
| if (fatal_signal_pending(current)) |
| break; |
| } |
| |
| if (!dirty_exceeded && wb->dirty_exceeded) |
| wb->dirty_exceeded = 0; |
| |
| if (writeback_in_progress(wb)) |
| return; |
| |
| /* |
| * In laptop mode, we wait until hitting the higher threshold before |
| * starting background writeout, and then write out all the way down |
| * to the lower threshold. So slow writers cause minimal disk activity. |
| * |
| * In normal mode, we start background writeout at the lower |
| * background_thresh, to keep the amount of dirty memory low. |
| */ |
| if (laptop_mode) |
| return; |
| |
| if (nr_reclaimable > gdtc->bg_thresh) |
| wb_start_background_writeback(wb); |
| } |
| |
| static DEFINE_PER_CPU(int, bdp_ratelimits); |
| |
| /* |
| * Normal tasks are throttled by |
| * loop { |
| * dirty tsk->nr_dirtied_pause pages; |
| * take a snap in balance_dirty_pages(); |
| * } |
| * However there is a worst case. If every task exit immediately when dirtied |
| * (tsk->nr_dirtied_pause - 1) pages, balance_dirty_pages() will never be |
| * called to throttle the page dirties. The solution is to save the not yet |
| * throttled page dirties in dirty_throttle_leaks on task exit and charge them |
| * randomly into the running tasks. This works well for the above worst case, |
| * as the new task will pick up and accumulate the old task's leaked dirty |
| * count and eventually get throttled. |
| */ |
| DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0; |
| |
| /** |
| * balance_dirty_pages_ratelimited - balance dirty memory state |
| * @mapping: address_space which was dirtied |
| * |
| * Processes which are dirtying memory should call in here once for each page |
| * which was newly dirtied. The function will periodically check the system's |
| * dirty state and will initiate writeback if needed. |
| * |
| * On really big machines, get_writeback_state is expensive, so try to avoid |
| * calling it too often (ratelimiting). But once we're over the dirty memory |
| * limit we decrease the ratelimiting by a lot, to prevent individual processes |
| * from overshooting the limit by (ratelimit_pages) each. |
| */ |
| void balance_dirty_pages_ratelimited(struct address_space *mapping) |
| { |
| struct inode *inode = mapping->host; |
| struct backing_dev_info *bdi = inode_to_bdi(inode); |
| struct bdi_writeback *wb = NULL; |
| int ratelimit; |
| int *p; |
| |
| if (!bdi_cap_account_dirty(bdi)) |
| return; |
| |
| if (inode_cgwb_enabled(inode)) |
| wb = wb_get_create_current(bdi, GFP_KERNEL); |
| if (!wb) |
| wb = &bdi->wb; |
| |
| ratelimit = current->nr_dirtied_pause; |
| if (wb->dirty_exceeded) |
| ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10)); |
| |
| preempt_disable(); |
| /* |
| * This prevents one CPU to accumulate too many dirtied pages without |
| * calling into balance_dirty_pages(), which can happen when there are |
| * 1000+ tasks, all of them start dirtying pages at exactly the same |
| * time, hence all honoured too large initial task->nr_dirtied_pause. |
| */ |
| p = this_cpu_ptr(&bdp_ratelimits); |
| if (unlikely(current->nr_dirtied >= ratelimit)) |
| *p = 0; |
| else if (unlikely(*p >= ratelimit_pages)) { |
| *p = 0; |
| ratelimit = 0; |
| } |
| /* |
| * Pick up the dirtied pages by the exited tasks. This avoids lots of |
| * short-lived tasks (eg. gcc invocations in a kernel build) escaping |
| * the dirty throttling and livelock other long-run dirtiers. |
| */ |
| p = this_cpu_ptr(&dirty_throttle_leaks); |
| if (*p > 0 && current->nr_dirtied < ratelimit) { |
| unsigned long nr_pages_dirtied; |
| 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, wb, current->nr_dirtied); |
| |
| wb_put(wb); |
| } |
| EXPORT_SYMBOL(balance_dirty_pages_ratelimited); |
| |
| /** |
| * wb_over_bg_thresh - does @wb need to be written back? |
| * @wb: bdi_writeback of interest |
| * |
| * Determines whether background writeback should keep writing @wb or it's |
| * clean enough. Returns %true if writeback should continue. |
| */ |
| bool wb_over_bg_thresh(struct bdi_writeback *wb) |
| { |
| struct dirty_throttle_control gdtc_stor = { GDTC_INIT(wb) }; |
| struct dirty_throttle_control mdtc_stor = { MDTC_INIT(wb, &gdtc_stor) }; |
| struct dirty_throttle_control * const gdtc = &gdtc_stor; |
| struct dirty_throttle_control * const mdtc = mdtc_valid(&mdtc_stor) ? |
| &mdtc_stor : NULL; |
| |
| /* |
| * Similar to balance_dirty_pages() but ignores pages being written |
| * as we're trying to decide whether to put more under writeback. |
| */ |
| gdtc->avail = global_dirtyable_memory(); |
| gdtc->dirty = global_node_page_state(NR_FILE_DIRTY) + |
| global_node_page_state(NR_UNSTABLE_NFS); |
| domain_dirty_limits(gdtc); |
| |
| if (gdtc->dirty > gdtc->bg_thresh) |
| return true; |
| |
| if (wb_stat(wb, WB_RECLAIMABLE) > |
| wb_calc_thresh(gdtc->wb, gdtc->bg_thresh)) |
| return true; |
| |
| if (mdtc) { |
| unsigned long filepages, headroom, writeback; |
| |
| mem_cgroup_wb_stats(wb, &filepages, &headroom, &mdtc->dirty, |
| &writeback); |
| mdtc_calc_avail(mdtc, filepages, headroom); |
| domain_dirty_limits(mdtc); /* ditto, ignore writeback */ |
| |
| if (mdtc->dirty > mdtc->bg_thresh) |
| return true; |
| |
| if (wb_stat(wb, WB_RECLAIMABLE) > |
| wb_calc_thresh(mdtc->wb, mdtc->bg_thresh)) |
| return true; |
| } |
| |
| return false; |
| } |
| |
| /* |
| * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs |
| */ |
| int dirty_writeback_centisecs_handler(struct ctl_table *table, int write, |
| void __user *buffer, size_t *length, loff_t *ppos) |
| { |
| proc_dointvec(table, write, buffer, length, ppos); |
| 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_node_page_state(NR_FILE_DIRTY) + |
| global_node_page_state(NR_UNSTABLE_NFS); |
| struct bdi_writeback *wb; |
| |
| /* |
| * We want to write everything out, not just down to the dirty |
| * threshold |
| */ |
| if (!bdi_has_dirty_io(q->backing_dev_info)) |
| return; |
| |
| rcu_read_lock(); |
| list_for_each_entry_rcu(wb, &q->backing_dev_info->wb_list, bdi_node) |
| if (wb_has_dirty_io(wb)) |
| wb_start_writeback(wb, nr_pages, true, |
| WB_REASON_LAPTOP_TIMER); |
| rcu_read_unlock(); |
| } |
| |
| /* |
| * We've spun up the disk and we're in laptop mode: schedule writeback |
| * of all dirty data a few seconds from now. If the flush is already scheduled |
| * then push it back - the user is still using the disk. |
| */ |
| 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 |
| |
| /* |
| * If ratelimit_pages is too high then we can get into dirty-data overload |
| * if a large number of processes all perform writes at the same time. |
| * If it is too low then SMP machines will call the (expensive) |
| * get_writeback_state too often. |
| * |
| * Here we set ratelimit_pages to a level which ensures that when all CPUs are |
| * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory |
| * thresholds. |
| */ |
| |
| void writeback_set_ratelimit(void) |
| { |
| struct wb_domain *dom = &global_wb_domain; |
| unsigned long background_thresh; |
| unsigned long dirty_thresh; |
| |
| global_dirty_limits(&background_thresh, &dirty_thresh); |
| dom->dirty_limit = dirty_thresh; |
| ratelimit_pages = dirty_thresh / (num_online_cpus() * 32); |
| if (ratelimit_pages < 16) |
| ratelimit_pages = 16; |
| } |
| |
| static int page_writeback_cpu_online(unsigned int cpu) |
| { |
| writeback_set_ratelimit(); |
| return 0; |
| } |
| |
| /* |
| * Called early on to tune the page writeback dirty limits. |
| * |
| * We used to scale dirty pages according to how total memory |
| * related to pages that could be allocated for buffers (by |
| * comparing nr_free_buffer_pages() to vm_total_pages. |
| * |
| * However, that was when we used "dirty_ratio" to scale with |
| * all memory, and we don't do that any more. "dirty_ratio" |
| * is now applied to total non-HIGHPAGE memory (by subtracting |
| * totalhigh_pages from vm_total_pages), and as such we can't |
| * get into the old insane situation any more where we had |
| * large amounts of dirty pages compared to a small amount of |
| * non-HIGHMEM memory. |
| * |
| * But we might still want to scale the dirty_ratio by how |
| * much memory the box has.. |
| */ |
| void __init page_writeback_init(void) |
| { |
| BUG_ON(wb_domain_init(&global_wb_domain, GFP_KERNEL)); |
| |
| cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mm/writeback:online", |
| page_writeback_cpu_online, NULL); |
| cpuhp_setup_state(CPUHP_MM_WRITEBACK_DEAD, "mm/writeback:dead", NULL, |
| page_writeback_cpu_online); |
| } |
| |
| /** |
| * 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). |
| */ |
| /* |
| * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency. |
| */ |
| void tag_pages_for_writeback(struct address_space *mapping, |
| pgoff_t start, pgoff_t end) |
| { |
| #define WRITEBACK_TAG_BATCH 4096 |
| unsigned long tagged = 0; |
| struct radix_tree_iter iter; |
| void **slot; |
| |
| spin_lock_irq(&mapping->tree_lock); |
| radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter, start, |
| PAGECACHE_TAG_DIRTY) { |
| if (iter.index > end) |
| break; |
| radix_tree_iter_tag_set(&mapping->page_tree, &iter, |
| PAGECACHE_TAG_TOWRITE); |
| tagged++; |
| if ((tagged % WRITEBACK_TAG_BATCH) != 0) |
| continue; |
| slot = radix_tree_iter_resume(slot, &iter); |
| spin_unlock_irq(&mapping->tree_lock); |
| cond_resched(); |
| spin_lock_irq(&mapping->tree_lock); |
| } |
| spin_unlock_irq(&mapping->tree_lock); |
| } |
| 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; |
| int error; |
| struct pagevec pvec; |
| int nr_pages; |
| pgoff_t uninitialized_var(writeback_index); |
| pgoff_t index; |
| pgoff_t end; /* Inclusive */ |
| 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; /* prev offset */ |
| index = writeback_index; |
| if (index == 0) |
| cycled = 1; |
| else |
| cycled = 0; |
| end = -1; |
| } else { |
| index = wbc->range_start >> PAGE_SHIFT; |
| end = wbc->range_end >> PAGE_SHIFT; |
| if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) |
| range_whole = 1; |
| cycled = 1; /* ignore range_cyclic tests */ |
| } |
| 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_range_tag(&pvec, mapping, &index, end, |
| tag); |
| if (nr_pages == 0) |
| break; |
| |
| for (i = 0; i < nr_pages; i++) { |
| struct page *page = pvec.pages[i]; |
| |
| done_index = page->index; |
| |
| lock_page(page); |
| |
| /* |
| * Page truncated or invalidated. We can freely skip it |
| * then, even for data integrity operations: the page |
| * has disappeared concurrently, so there could be no |
| * real expectation of this data interity operation |
| * even if there is now a new, dirty page at the same |
| * pagecache address. |
| */ |
| if (unlikely(page->mapping != mapping)) { |
| continue_unlock: |
| unlock_page(page); |
| continue; |
| } |
| |
| if (!PageDirty(page)) { |
| /* someone wrote it for us */ |
| 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, inode_to_bdi(mapping->host)); |
| error = (*writepage)(page, wbc, data); |
| if (unlikely(error)) { |
| /* |
| * Handle errors according to the type of |
| * writeback. There's no need to continue for |
| * background writeback. Just push done_index |
| * past this page so media errors won't choke |
| * writeout for the entire file. For integrity |
| * writeback, we must process the entire dirty |
| * set regardless of errors because the fs may |
| * still have state to clear for each page. In |
| * that case we continue processing and return |
| * the first error. |
| */ |
| if (error == AOP_WRITEPAGE_ACTIVATE) { |
| unlock_page(page); |
| error = 0; |
| } else if (wbc->sync_mode != WB_SYNC_ALL) { |
| ret = error; |
| done_index = page->index + 1; |
| done = 1; |
| break; |
| } |
| if (!ret) |
| ret = error; |
| } |
| |
| /* |
| * 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) { |
| /* |
| * range_cyclic: |
| * We hit the last page and there is more work to be done: wrap |
| * back to the start of the file |
| */ |
| 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); |
| |
| /* |
| * Function used by generic_writepages to call the real writepage |
| * function and set the mapping flags on error |
| */ |
| 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; |
| |
| /* deal with chardevs and other special file */ |
| 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; |
| while (1) { |
| if (mapping->a_ops->writepages) |
| ret = mapping->a_ops->writepages(mapping, wbc); |
| else |
| ret = generic_writepages(mapping, wbc); |
| if ((ret != -ENOMEM) || (wbc->sync_mode != WB_SYNC_ALL)) |
| break; |
| cond_resched(); |
| congestion_wait(BLK_RW_ASYNC, HZ/50); |
| } |
| return ret; |
| } |
| |
| /** |
| * write_one_page - write out a single page and wait on I/O |
| * @page: the page to write |
| * |
| * The page must be locked by the caller and will be unlocked upon return. |
| * |
| * Note that the mapping's AS_EIO/AS_ENOSPC flags will be cleared when this |
| * function returns. |
| */ |
| int write_one_page(struct page *page) |
| { |
| 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)); |
| |
| wait_on_page_writeback(page); |
| |
| if (clear_page_dirty_for_io(page)) { |
| get_page(page); |
| ret = mapping->a_ops->writepage(page, &wbc); |
| if (ret == 0) |
| wait_on_page_writeback(page); |
| put_page(page); |
| } else { |
| unlock_page(page); |
| } |
| |
| if (!ret) |
| ret = filemap_check_errors(mapping); |
| return ret; |
| } |
| EXPORT_SYMBOL(write_one_page); |
| |
| /* |
| * For address_spaces which do not use buffers nor write back. |
| */ |
| int __set_page_dirty_no_writeback(struct page *page) |
| { |
| if (!PageDirty(page)) |
| return !TestSetPageDirty(page); |
| return 0; |
| } |
| |
| /* |
| * Helper function for set_page_dirty family. |
| * |
| * Caller must hold lock_page_memcg(). |
| * |
| * NOTE: This relies on being atomic wrt interrupts. |
| */ |
| void account_page_dirtied(struct page *page, struct address_space *mapping) |
| { |
| struct inode *inode = mapping->host; |
| |
| trace_writeback_dirty_page(page, mapping); |
| |
| if (mapping_cap_account_dirty(mapping)) { |
| struct bdi_writeback *wb; |
| |
| inode_attach_wb(inode, page); |
| wb = inode_to_wb(inode); |
| |
| __inc_lruvec_page_state(page, NR_FILE_DIRTY); |
| __inc_zone_page_state(page, NR_ZONE_WRITE_PENDING); |
| __inc_node_page_state(page, NR_DIRTIED); |
| inc_wb_stat(wb, WB_RECLAIMABLE); |
| inc_wb_stat(wb, WB_DIRTIED); |
| task_io_account_write(PAGE_SIZE); |
| current->nr_dirtied++; |
| this_cpu_inc(bdp_ratelimits); |
| } |
| } |
| EXPORT_SYMBOL(account_page_dirtied); |
| |
| /* |
| * Helper function for deaccounting dirty page without writeback. |
| * |
| * Caller must hold lock_page_memcg(). |
| */ |
| void account_page_cleaned(struct page *page, struct address_space *mapping, |
| struct bdi_writeback *wb) |
| { |
| if (mapping_cap_account_dirty(mapping)) { |
| dec_lruvec_page_state(page, NR_FILE_DIRTY); |
| dec_zone_page_state(page, NR_ZONE_WRITE_PENDING); |
| dec_wb_stat(wb, WB_RECLAIMABLE); |
| task_io_account_cancelled_write(PAGE_SIZE); |
| } |
| } |
| |
| /* |
| * For address_spaces which do not use buffers. Just tag the page as dirty in |
| * its radix tree. |
| * |
| * This is also used when a single buffer is being dirtied: we want to set the |
| * page dirty in that case, but not all the buffers. This is a "bottom-up" |
| * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying. |
| * |
| * The caller must ensure this doesn't race with truncation. Most will simply |
| * hold the page lock, but e.g. zap_pte_range() calls with the page mapped and |
| * the pte lock held, which also locks out truncation. |
| */ |
| int __set_page_dirty_nobuffers(struct page *page) |
| { |
| lock_page_memcg(page); |
| if (!TestSetPageDirty(page)) { |
| struct address_space *mapping = page_mapping(page); |
| unsigned long flags; |
| |
| if (!mapping) { |
| unlock_page_memcg(page); |
| return 1; |
| } |
| |
| spin_lock_irqsave(&mapping->tree_lock, flags); |
| BUG_ON(page_mapping(page) != 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); |
| unlock_page_memcg(page); |
| |
| if (mapping->host) { |
| /* !PageAnon && !swapper_space */ |
| __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); |
| } |
| return 1; |
| } |
| unlock_page_memcg(page); |
| 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)) { |
| struct inode *inode = mapping->host; |
| struct bdi_writeback *wb; |
| struct wb_lock_cookie cookie = {}; |
| |
| wb = unlocked_inode_to_wb_begin(inode, &cookie); |
| current->nr_dirtied--; |
| dec_node_page_state(page, NR_DIRTIED); |
| dec_wb_stat(wb, WB_DIRTIED); |
| unlocked_inode_to_wb_end(inode, &cookie); |
| } |
| } |
| EXPORT_SYMBOL(account_page_redirty); |
| |
| /* |
| * When a writepage implementation decides that it doesn't want to write this |
| * page for some reason, it should redirty the locked page via |
| * redirty_page_for_writepage() and it should then unlock the page and return 0 |
| */ |
| int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) |
| { |
| int ret; |
| |
| wbc->pages_skipped++; |
| ret = __set_page_dirty_nobuffers(page); |
| account_page_redirty(page); |
| return ret; |
| } |
| EXPORT_SYMBOL(redirty_page_for_writepage); |
| |
| /* |
| * Dirty a page. |
| * |
| * For pages with a mapping this should be done under the page lock |
| * for the benefit of asynchronous memory errors who prefer a consistent |
| * dirty state. This rule can be broken in some special cases, |
| * but should be better not to. |
| * |
| * If the mapping doesn't provide a set_page_dirty a_op, then |
| * just fall through and assume that it wants buffer_heads. |
| */ |
| int set_page_dirty(struct page *page) |
| { |
| struct address_space *mapping = page_mapping(page); |
| |
| page = compound_head(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. |
| */ |
| if (PageReclaim(page)) |
| 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); |
| |
| /* |
| * set_page_dirty() is racy if the caller has no reference against |
| * page->mapping->host, and if the page is unlocked. This is because another |
| * CPU could truncate the page off the mapping and then free the mapping. |
| * |
| * Usually, the page _is_ locked, or the caller is a user-space process which |
| * holds a reference on the inode by having an open file. |
| * |
| * In other cases, the page should be locked before running 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); |
| |
| /* |
| * This cancels just the dirty bit on the kernel page itself, it does NOT |
| * actually remove dirty bits on any mmap's that may be around. It also |
| * leaves the page tagged dirty, so any sync activity will still find it on |
| * the dirty lists, and in particular, clear_page_dirty_for_io() will still |
| * look at the dirty bits in the VM. |
| * |
| * Doing this should *normally* only ever be done when a page is truncated, |
| * and is not actually mapped anywhere at all. However, fs/buffer.c does |
| * this when it notices that somebody has cleaned out all the buffers on a |
| * page without actually doing it through the VM. Can you say "ext3 is |
| * horribly ugly"? Thought you could. |
| */ |
| void cancel_dirty_page(struct page *page) |
| { |
| struct address_space *mapping = page_mapping(page); |
| |
| if (mapping_cap_account_dirty(mapping)) { |
| struct inode *inode = mapping->host; |
| struct bdi_writeback *wb; |
| struct wb_lock_cookie cookie = {}; |
| |
| lock_page_memcg(page); |
| wb = unlocked_inode_to_wb_begin(inode, &cookie); |
| |
| if (TestClearPageDirty(page)) |
| account_page_cleaned(page, mapping, wb); |
| |
| unlocked_inode_to_wb_end(inode, &cookie); |
| unlock_page_memcg(page); |
| } else { |
| ClearPageDirty(page); |
| } |
| } |
| EXPORT_SYMBOL(cancel_dirty_page); |
| |
| /* |
| * Clear a page's dirty flag, while caring for dirty memory accounting. |
| * Returns true if the page was previously dirty. |
| * |
| * This is for preparing to put the page under writeout. We leave the page |
| * tagged as dirty in the radix tree so that a concurrent write-for-sync |
| * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage |
| * implementation will run either set_page_writeback() or set_page_dirty(), |
| * at which stage we bring the page's dirty flag and radix-tree dirty tag |
| * back into sync. |
| * |
| * This incoherency between the page's dirty flag and radix-tree tag is |
| * unfortunate, but it only exists while the page is locked. |
| */ |
| int clear_page_dirty_for_io(struct page *page) |
| { |
| struct address_space *mapping = page_mapping(page); |
| int ret = 0; |
| |
| BUG_ON(!PageLocked(page)); |
| |
| if (mapping && mapping_cap_account_dirty(mapping)) { |
| struct inode *inode = mapping->host; |
| struct bdi_writeback *wb; |
| struct wb_lock_cookie cookie = {}; |
| |
| /* |
| * Yes, Virginia, this is indeed insane. |
| * |
| * We use this sequence to make sure that |
| * (a) we account for dirty stats properly |
| * (b) we tell the low-level filesystem to |
| * mark the whole page dirty if it was |
| * dirty in a pagetable. Only to then |
| * (c) clean the page again and return 1 to |
| * cause the writeback. |
| * |
| * This way we avoid all nasty races with the |
| * dirty bit in multiple places and clearing |
| * them concurrently from different threads. |
| * |
| * Note! Normally the "set_page_dirty(page)" |
| * has no effect on the actual dirty bit - since |
| * that will already usually be set. But we |
| * need the side effects, and it can help us |
| * avoid races. |
| * |
| * We basically use the page "master dirty bit" |
| * as a serialization point for all the different |
| * threads doing their things. |
| */ |
| if (page_mkclean(page)) |
| set_page_dirty(page); |
| /* |
| * We carefully synchronise fault handlers against |
| * installing a dirty pte and marking the page dirty |
| * at this point. We do this by having them hold the |
| * page lock while dirtying the page, and pages are |
| * always locked coming in here, so we get the desired |
| * exclusion. |
| */ |
| wb = unlocked_inode_to_wb_begin(inode, &cookie); |
| if (TestClearPageDirty(page)) { |
| dec_lruvec_page_state(page, NR_FILE_DIRTY); |
| dec_zone_page_state(page, NR_ZONE_WRITE_PENDING); |
| dec_wb_stat(wb, WB_RECLAIMABLE); |
| ret = 1; |
| } |
| unlocked_inode_to_wb_end(inode, &cookie); |
| return ret; |
| } |
| 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); |
| struct mem_cgroup *memcg; |
| struct lruvec *lruvec; |
| int ret; |
| |
| memcg = lock_page_memcg(page); |
| lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page)); |
| if (mapping && mapping_use_writeback_tags(mapping)) { |
| struct inode *inode = mapping->host; |
| struct backing_dev_info *bdi = inode_to_bdi(inode); |
| 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)) { |
| struct bdi_writeback *wb = inode_to_wb(inode); |
| |
| dec_wb_stat(wb, WB_WRITEBACK); |
| __wb_writeout_inc(wb); |
| } |
| } |
| |
| if (mapping->host && !mapping_tagged(mapping, |
| PAGECACHE_TAG_WRITEBACK)) |
| sb_clear_inode_writeback(mapping->host); |
| |
| spin_unlock_irqrestore(&mapping->tree_lock, flags); |
| } else { |
| ret = TestClearPageWriteback(page); |
| } |
| /* |
| * NOTE: Page might be free now! Writeback doesn't hold a page |
| * reference on its own, it relies on truncation to wait for |
| * the clearing of PG_writeback. The below can only access |
| * page state that is static across allocation cycles. |
| */ |
| if (ret) { |
| dec_lruvec_state(lruvec, NR_WRITEBACK); |
| dec_zone_page_state(page, NR_ZONE_WRITE_PENDING); |
| inc_node_page_state(page, NR_WRITTEN); |
| } |
| __unlock_page_memcg(memcg); |
| return ret; |
| } |
| |
| int __test_set_page_writeback(struct page *page, bool keep_write) |
| { |
| struct address_space *mapping = page_mapping(page); |
| int ret; |
| |
| lock_page_memcg(page); |
| if (mapping && mapping_use_writeback_tags(mapping)) { |
| struct inode *inode = mapping->host; |
| struct backing_dev_info *bdi = inode_to_bdi(inode); |
| unsigned long flags; |
| |
| spin_lock_irqsave(&mapping->tree_lock, flags); |
| ret = TestSetPageWriteback(page); |
| if (!ret) { |
| bool on_wblist; |
| |
| on_wblist = mapping_tagged(mapping, |
| PAGECACHE_TAG_WRITEBACK); |
| |
| radix_tree_tag_set(&mapping->page_tree, |
| page_index(page), |
| PAGECACHE_TAG_WRITEBACK); |
| if (bdi_cap_account_writeback(bdi)) |
| inc_wb_stat(inode_to_wb(inode), WB_WRITEBACK); |
| |
| /* |
| * We can come through here when swapping anonymous |
| * pages, so we don't necessarily have an inode to track |
| * for sync. |
| */ |
| if (mapping->host && !on_wblist) |
| sb_mark_inode_writeback(mapping->host); |
| } |
| if (!PageDirty(page)) |
| radix_tree_tag_clear(&mapping->page_tree, |
| page_index(page), |
| PAGECACHE_TAG_DIRTY); |
| if (!keep_write) |
| 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) { |
| inc_lruvec_page_state(page, NR_WRITEBACK); |
| inc_zone_page_state(page, NR_ZONE_WRITE_PENDING); |
| } |
| unlock_page_memcg(page); |
| return ret; |
| |
| } |
| EXPORT_SYMBOL(__test_set_page_writeback); |
| |
| /* |
| * Return true if any of the pages in the mapping are marked with the |
| * passed tag. |
| */ |
| int mapping_tagged(struct address_space *mapping, int tag) |
| { |
| return radix_tree_tagged(&mapping->page_tree, tag); |
| } |
| EXPORT_SYMBOL(mapping_tagged); |
| |
| /** |
| * wait_for_stable_page() - wait for writeback to finish, if necessary. |
| * @page: The page to wait on. |
| * |
| * This function determines if the given page is related to a backing device |
| * that requires page contents to be held stable during writeback. If so, then |
| * it will wait for any pending writeback to complete. |
| */ |
| void wait_for_stable_page(struct page *page) |
| { |
| if (bdi_cap_stable_pages_required(inode_to_bdi(page->mapping->host))) |
| wait_on_page_writeback(page); |
| } |
| EXPORT_SYMBOL_GPL(wait_for_stable_page); |