| /* |
| * mm/page-writeback.c |
| * |
| * Copyright (C) 2002, Linus Torvalds. |
| * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> |
| * |
| * Contains functions related to writing back dirty pages at the |
| * address_space level. |
| * |
| * 10Apr2002 Andrew Morton |
| * Initial version |
| */ |
| |
| #include <linux/kernel.h> |
| #include <linux/module.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> |
| #include <linux/pagevec.h> |
| #include <trace/events/writeback.h> |
| |
| /* |
| * 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; |
| |
| /* |
| * When balance_dirty_pages decides that the caller needs to perform some |
| * non-background writeback, this is how many pages it will attempt to write. |
| * It should be somewhat larger than dirtied pages to ensure that reasonably |
| * large amounts of I/O are submitted. |
| */ |
| static inline long sync_writeback_pages(unsigned long dirtied) |
| { |
| if (dirtied < ratelimit_pages) |
| dirtied = ratelimit_pages; |
| |
| return dirtied + dirtied / 2; |
| } |
| |
| /* 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 */ |
| |
| /* |
| * 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 */ |
| |
| |
| /* |
| * 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 struct prop_descriptor vm_dirties; |
| |
| /* |
| * couple the period to the dirty_ratio: |
| * |
| * period/2 ~ roundup_pow_of_two(dirty 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 * determine_dirtyable_memory()) / |
| 100; |
| return 2 + ilog2(dirty_total - 1); |
| } |
| |
| /* |
| * update the period when the dirty threshold changes. |
| */ |
| static void update_completion_period(void) |
| { |
| int shift = calc_period_shift(); |
| prop_change_shift(&vm_completions, shift); |
| prop_change_shift(&vm_dirties, shift); |
| } |
| |
| 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; |
| } |
| |
| /* |
| * Increment the BDI's writeout completion count and the global writeout |
| * completion count. Called from test_clear_page_writeback(). |
| */ |
| static inline void __bdi_writeout_inc(struct backing_dev_info *bdi) |
| { |
| __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); |
| |
| void task_dirty_inc(struct task_struct *tsk) |
| { |
| prop_inc_single(&vm_dirties, &tsk->dirties); |
| } |
| |
| /* |
| * Obtain an accurate fraction of the BDI's portion. |
| */ |
| static void bdi_writeout_fraction(struct backing_dev_info *bdi, |
| long *numerator, long *denominator) |
| { |
| if (bdi_cap_writeback_dirty(bdi)) { |
| prop_fraction_percpu(&vm_completions, &bdi->completions, |
| numerator, denominator); |
| } else { |
| *numerator = 0; |
| *denominator = 1; |
| } |
| } |
| |
| /* |
| * Clip the earned share of dirty pages to that which is actually available. |
| * This avoids exceeding the total dirty_limit when the floating averages |
| * fluctuate too quickly. |
| */ |
| static void clip_bdi_dirty_limit(struct backing_dev_info *bdi, |
| unsigned long dirty, unsigned long *pbdi_dirty) |
| { |
| unsigned long avail_dirty; |
| |
| avail_dirty = global_page_state(NR_FILE_DIRTY) + |
| global_page_state(NR_WRITEBACK) + |
| global_page_state(NR_UNSTABLE_NFS) + |
| global_page_state(NR_WRITEBACK_TEMP); |
| |
| if (avail_dirty < dirty) |
| avail_dirty = dirty - avail_dirty; |
| else |
| avail_dirty = 0; |
| |
| avail_dirty += bdi_stat(bdi, BDI_RECLAIMABLE) + |
| bdi_stat(bdi, BDI_WRITEBACK); |
| |
| *pbdi_dirty = min(*pbdi_dirty, avail_dirty); |
| } |
| |
| static inline void task_dirties_fraction(struct task_struct *tsk, |
| long *numerator, long *denominator) |
| { |
| prop_fraction_single(&vm_dirties, &tsk->dirties, |
| numerator, denominator); |
| } |
| |
| /* |
| * scale the dirty limit |
| * |
| * task specific dirty limit: |
| * |
| * dirty -= (dirty/8) * p_{t} |
| */ |
| static void task_dirty_limit(struct task_struct *tsk, unsigned long *pdirty) |
| { |
| long numerator, denominator; |
| unsigned long dirty = *pdirty; |
| u64 inv = dirty >> 3; |
| |
| task_dirties_fraction(tsk, &numerator, &denominator); |
| inv *= numerator; |
| do_div(inv, denominator); |
| |
| dirty -= inv; |
| if (dirty < *pdirty/2) |
| dirty = *pdirty/2; |
| |
| *pdirty = dirty; |
| } |
| |
| /* |
| * |
| */ |
| 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); |
| |
| /* |
| * Work out the current dirty-memory clamping and background writeout |
| * thresholds. |
| * |
| * The main aim here is to lower them aggressively if there is a lot of mapped |
| * memory around. To avoid stressing page reclaim with lots of unreclaimable |
| * pages. It is better to clamp down on writers than to start swapping, and |
| * performing lots of scanning. |
| * |
| * We only allow 1/2 of the currently-unmapped memory to be dirtied. |
| * |
| * We don't permit the clamping level to fall below 5% - that is getting rather |
| * excessive. |
| * |
| * We make sure that the background writeout level is below the adjusted |
| * clamping level. |
| */ |
| |
| 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); |
| } |
| /* |
| * 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 |
| } |
| |
| /** |
| * determine_dirtyable_memory - amount of memory that may be used |
| * |
| * Returns the numebr of pages that can currently be freed and used |
| * by the kernel for direct mappings. |
| */ |
| unsigned long determine_dirtyable_memory(void) |
| { |
| unsigned long x; |
| |
| x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages(); |
| |
| if (!vm_highmem_is_dirtyable) |
| x -= highmem_dirtyable_memory(x); |
| |
| return x + 1; /* Ensure that we never return 0 */ |
| } |
| |
| void |
| get_dirty_limits(unsigned long *pbackground, unsigned long *pdirty, |
| unsigned long *pbdi_dirty, struct backing_dev_info *bdi) |
| { |
| unsigned long background; |
| unsigned long dirty; |
| unsigned long available_memory = determine_dirtyable_memory(); |
| struct task_struct *tsk; |
| |
| if (vm_dirty_bytes) |
| dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); |
| else { |
| int dirty_ratio; |
| |
| dirty_ratio = vm_dirty_ratio; |
| if (dirty_ratio < 5) |
| dirty_ratio = 5; |
| dirty = (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; |
| |
| if (bdi) { |
| u64 bdi_dirty; |
| long numerator, denominator; |
| |
| /* |
| * Calculate this BDI's share of the dirty ratio. |
| */ |
| 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; |
| |
| *pbdi_dirty = bdi_dirty; |
| clip_bdi_dirty_limit(bdi, dirty, pbdi_dirty); |
| task_dirty_limit(current, pbdi_dirty); |
| } |
| } |
| |
| /* |
| * 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 perform writeback if the system is over `vm_dirty_ratio'. |
| * 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, |
| unsigned long write_chunk) |
| { |
| long nr_reclaimable, bdi_nr_reclaimable; |
| long nr_writeback, bdi_nr_writeback; |
| unsigned long background_thresh; |
| unsigned long dirty_thresh; |
| unsigned long bdi_thresh; |
| unsigned long pages_written = 0; |
| unsigned long pause = 1; |
| |
| struct backing_dev_info *bdi = mapping->backing_dev_info; |
| |
| for (;;) { |
| struct writeback_control wbc = { |
| .sync_mode = WB_SYNC_NONE, |
| .older_than_this = NULL, |
| .nr_to_write = write_chunk, |
| .range_cyclic = 1, |
| }; |
| |
| get_dirty_limits(&background_thresh, &dirty_thresh, |
| &bdi_thresh, bdi); |
| |
| nr_reclaimable = global_page_state(NR_FILE_DIRTY) + |
| global_page_state(NR_UNSTABLE_NFS); |
| nr_writeback = global_page_state(NR_WRITEBACK); |
| |
| bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); |
| bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK); |
| |
| if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh) |
| break; |
| |
| /* |
| * Throttle it only when the background writeback cannot |
| * catch-up. This avoids (excessively) small writeouts |
| * when the bdi limits are ramping up. |
| */ |
| if (nr_reclaimable + nr_writeback < |
| (background_thresh + dirty_thresh) / 2) |
| break; |
| |
| if (!bdi->dirty_exceeded) |
| bdi->dirty_exceeded = 1; |
| |
| /* Note: nr_reclaimable denotes nr_dirty + nr_unstable. |
| * 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. |
| * Only move pages to writeback if this bdi is over its |
| * threshold otherwise wait until the disk writes catch |
| * up. |
| */ |
| trace_wbc_balance_dirty_start(&wbc, bdi); |
| if (bdi_nr_reclaimable > bdi_thresh) { |
| writeback_inodes_wb(&bdi->wb, &wbc); |
| pages_written += write_chunk - wbc.nr_to_write; |
| get_dirty_limits(&background_thresh, &dirty_thresh, |
| &bdi_thresh, bdi); |
| trace_wbc_balance_dirty_written(&wbc, bdi); |
| } |
| |
| /* |
| * 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 (bdi_thresh < 2*bdi_stat_error(bdi)) { |
| bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); |
| bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK); |
| } else if (bdi_nr_reclaimable) { |
| bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); |
| bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK); |
| } |
| |
| if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh) |
| break; |
| if (pages_written >= write_chunk) |
| break; /* We've done our duty */ |
| |
| trace_wbc_balance_dirty_wait(&wbc, bdi); |
| __set_current_state(TASK_INTERRUPTIBLE); |
| io_schedule_timeout(pause); |
| |
| /* |
| * Increase the delay for each loop, up to our previous |
| * default of taking a 100ms nap. |
| */ |
| pause <<= 1; |
| if (pause > HZ / 10) |
| pause = HZ / 10; |
| } |
| |
| if (bdi_nr_reclaimable + bdi_nr_writeback < bdi_thresh && |
| bdi->dirty_exceeded) |
| bdi->dirty_exceeded = 0; |
| |
| if (writeback_in_progress(bdi)) |
| 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 && pages_written) || |
| (!laptop_mode && ((global_page_state(NR_FILE_DIRTY) |
| + global_page_state(NR_UNSTABLE_NFS)) |
| > 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(unsigned long, bdp_ratelimits) = 0; |
| |
| /** |
| * balance_dirty_pages_ratelimited_nr - balance dirty memory state |
| * @mapping: address_space which was dirtied |
| * @nr_pages_dirtied: number of pages which the caller has just 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_nr(struct address_space *mapping, |
| unsigned long nr_pages_dirtied) |
| { |
| unsigned long ratelimit; |
| unsigned long *p; |
| |
| ratelimit = ratelimit_pages; |
| if (mapping->backing_dev_info->dirty_exceeded) |
| ratelimit = 8; |
| |
| /* |
| * Check the rate limiting. Also, we do not want to throttle real-time |
| * tasks in balance_dirty_pages(). Period. |
| */ |
| preempt_disable(); |
| p = &__get_cpu_var(bdp_ratelimits); |
| *p += nr_pages_dirtied; |
| if (unlikely(*p >= ratelimit)) { |
| ratelimit = sync_writeback_pages(*p); |
| *p = 0; |
| preempt_enable(); |
| balance_dirty_pages(mapping, ratelimit); |
| return; |
| } |
| preempt_enable(); |
| } |
| EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr); |
| |
| void throttle_vm_writeout(gfp_t gfp_mask) |
| { |
| unsigned long background_thresh; |
| unsigned long dirty_thresh; |
| |
| for ( ; ; ) { |
| get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL); |
| |
| /* |
| * Boost the allowable dirty threshold a bit for page |
| * allocators so they don't get DoS'ed by heavy writers |
| */ |
| dirty_thresh += dirty_thresh / 10; /* wheeee... */ |
| |
| if (global_page_state(NR_UNSTABLE_NFS) + |
| global_page_state(NR_WRITEBACK) <= dirty_thresh) |
| break; |
| congestion_wait(BLK_RW_ASYNC, HZ/10); |
| |
| /* |
| * The caller might hold locks which can prevent IO completion |
| * or progress in the filesystem. So we cannot just sit here |
| * waiting for IO to complete. |
| */ |
| if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) |
| break; |
| } |
| } |
| |
| /* |
| * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs |
| */ |
| 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); |
| |
| /* |
| * We want to write everything out, not just down to the dirty |
| * threshold |
| */ |
| if (bdi_has_dirty_io(&q->backing_dev_info)) |
| bdi_start_writeback(&q->backing_dev_info, nr_pages); |
| } |
| |
| /* |
| * 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 before writeback cuts in. |
| * |
| * But the limit should not be set too high. Because it also controls the |
| * amount of memory which the balance_dirty_pages() caller has to write back. |
| * If this is too large then the caller will block on the IO queue all the |
| * time. So limit it to four megabytes - the balance_dirty_pages() caller |
| * will write six megabyte chunks, max. |
| */ |
| |
| void writeback_set_ratelimit(void) |
| { |
| ratelimit_pages = vm_total_pages / (num_online_cpus() * 32); |
| if (ratelimit_pages < 16) |
| ratelimit_pages = 16; |
| if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024) |
| ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE; |
| } |
| |
| 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, |
| }; |
| |
| /* |
| * 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) |
| { |
| int shift; |
| |
| writeback_set_ratelimit(); |
| register_cpu_notifier(&ratelimit_nb); |
| |
| shift = calc_period_shift(); |
| prop_descriptor_init(&vm_completions, shift); |
| prop_descriptor_init(&vm_dirties, 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). |
| */ |
| /* |
| * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency. |
| */ |
| #define WRITEBACK_TAG_BATCH 4096 |
| void tag_pages_for_writeback(struct address_space *mapping, |
| pgoff_t start, pgoff_t end) |
| { |
| 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); |
| } |
| 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; /* 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_CACHE_SHIFT; |
| end = wbc->range_end >> PAGE_CACHE_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) |
| tag = PAGECACHE_TAG_TOWRITE; |
| else |
| tag = PAGECACHE_TAG_DIRTY; |
| retry: |
| if (wbc->sync_mode == WB_SYNC_ALL) |
| 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]; |
| |
| /* |
| * At this point, the page may be truncated or |
| * invalidated (changing page->mapping to NULL), or |
| * even swizzled back from swapper_space to tmpfs file |
| * mapping. However, page->index will not change |
| * because we have a reference on the page. |
| */ |
| if (page->index > end) { |
| /* |
| * can't be range_cyclic (1st pass) because |
| * end == -1 in that case. |
| */ |
| done = 1; |
| break; |
| } |
| |
| done_index = page->index + 1; |
| |
| 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, 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 is set past this page, |
| * so media errors will not choke |
| * background writeout for the entire |
| * file. This has consequences for |
| * range_cyclic semantics (ie. it may |
| * not be suitable for data integrity |
| * writeout). |
| */ |
| done = 1; |
| break; |
| } |
| } |
| |
| if (wbc->nr_to_write > 0) { |
| if (--wbc->nr_to_write == 0 && |
| wbc->sync_mode == WB_SYNC_NONE) { |
| /* |
| * We stop writing back only if we are |
| * not doing integrity sync. In case of |
| * integrity sync we have to keep going |
| * because someone may be concurrently |
| * dirtying pages, and we might have |
| * synced a lot of newly appeared dirty |
| * pages, but have not synced all of the |
| * old dirty pages. |
| */ |
| 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) |
| { |
| /* deal with chardevs and other special file */ |
| if (!mapping->a_ops->writepage) |
| return 0; |
| |
| return write_cache_pages(mapping, wbc, __writepage, mapping); |
| } |
| |
| 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; |
| } |
| |
| /** |
| * write_one_page - write out a single page and optionally wait on I/O |
| * @page: the page to write |
| * @wait: if true, wait on writeout |
| * |
| * The page must be locked by the caller and will be unlocked upon return. |
| * |
| * write_one_page() returns a negative error code if I/O failed. |
| */ |
| 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); |
| |
| /* |
| * For address_spaces which do not use buffers nor write back. |
| */ |
| int __set_page_dirty_no_writeback(struct page *page) |
| { |
| if (!PageDirty(page)) |
| SetPageDirty(page); |
| return 0; |
| } |
| |
| /* |
| * Helper function for set_page_dirty family. |
| * NOTE: This relies on being atomic wrt interrupts. |
| */ |
| 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_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); |
| task_dirty_inc(current); |
| task_io_account_write(PAGE_CACHE_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. |
| * |
| * Most callers have locked the page, which pins the address_space in memory. |
| * But zap_pte_range() does not lock the page, however in that case the |
| * mapping is pinned by the vma's ->vm_file reference. |
| * |
| * We take care to handle the case where the page was truncated from the |
| * mapping by re-checking page_mapping() inside tree_lock. |
| */ |
| int __set_page_dirty_nobuffers(struct page *page) |
| { |
| if (!TestSetPageDirty(page)) { |
| struct address_space *mapping = page_mapping(page); |
| struct address_space *mapping2; |
| |
| if (!mapping) |
| return 1; |
| |
| spin_lock_irq(&mapping->tree_lock); |
| mapping2 = page_mapping(page); |
| if (mapping2) { /* Race with truncate? */ |
| 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_irq(&mapping->tree_lock); |
| if (mapping->host) { |
| /* !PageAnon && !swapper_space */ |
| __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); |
| } |
| return 1; |
| } |
| return 0; |
| } |
| EXPORT_SYMBOL(__set_page_dirty_nobuffers); |
| |
| /* |
| * 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) |
| { |
| wbc->pages_skipped++; |
| return __set_page_dirty_nobuffers(page); |
| } |
| 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); |
| |
| if (likely(mapping)) { |
| int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; |
| #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_nosync(page); |
| ret = set_page_dirty(page); |
| unlock_page(page); |
| return ret; |
| } |
| EXPORT_SYMBOL(set_page_dirty_lock); |
| |
| /* |
| * 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); |
| |
| BUG_ON(!PageLocked(page)); |
| |
| ClearPageReclaim(page); |
| if (mapping && mapping_cap_account_dirty(mapping)) { |
| /* |
| * 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 at some point after installing their |
| * pte, but before marking the page dirty. |
| * Pages are always locked coming in here, so we get |
| * the desired exclusion. See mm/memory.c:do_wp_page() |
| * for more comments. |
| */ |
| 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); |
| 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) |
| inc_zone_page_state(page, NR_WRITEBACK); |
| 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) |
| { |
| int ret; |
| rcu_read_lock(); |
| ret = radix_tree_tagged(&mapping->page_tree, tag); |
| rcu_read_unlock(); |
| return ret; |
| } |
| EXPORT_SYMBOL(mapping_tagged); |