diff options
Diffstat (limited to 'mm/page-writeback.c')
| -rw-r--r-- | mm/page-writeback.c | 421 |
1 files changed, 291 insertions, 130 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 0713bfbf095..e0c943014eb 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -35,8 +35,12 @@ #include <linux/buffer_head.h> /* __set_page_dirty_buffers */ #include <linux/pagevec.h> #include <linux/timer.h> +#include <linux/sched/rt.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(). */ @@ -152,24 +156,6 @@ static unsigned long writeout_period_time = 0; #define VM_COMPLETIONS_PERIOD_LEN (3*HZ) /* - * 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. - */ - -/* * 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 @@ -187,6 +173,26 @@ static unsigned long writeout_period_time = 0; * global dirtyable memory first. */ +/** + * zone_dirtyable_memory - number of dirtyable pages in a zone + * @zone: the zone + * + * Returns the zone's number of pages potentially available for dirty + * page cache. This is the base value for the per-zone dirty limits. + */ +static unsigned long zone_dirtyable_memory(struct zone *zone) +{ + unsigned long nr_pages; + + nr_pages = zone_page_state(zone, NR_FREE_PAGES); + nr_pages -= min(nr_pages, zone->dirty_balance_reserve); + + nr_pages += zone_page_state(zone, NR_INACTIVE_FILE); + nr_pages += zone_page_state(zone, NR_ACTIVE_FILE); + + return nr_pages; +} + static unsigned long highmem_dirtyable_memory(unsigned long total) { #ifdef CONFIG_HIGHMEM @@ -194,11 +200,9 @@ static unsigned long highmem_dirtyable_memory(unsigned long total) unsigned long x = 0; for_each_node_state(node, N_HIGH_MEMORY) { - struct zone *z = - &NODE_DATA(node)->node_zones[ZONE_HIGHMEM]; + struct zone *z = &NODE_DATA(node)->node_zones[ZONE_HIGHMEM]; - x += zone_page_state(z, NR_FREE_PAGES) + - zone_reclaimable_pages(z) - z->dirty_balance_reserve; + x += zone_dirtyable_memory(z); } /* * Unreclaimable memory (kernel memory or anonymous memory @@ -234,9 +238,12 @@ static unsigned long global_dirtyable_memory(void) { unsigned long x; - x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages(); + x = global_page_state(NR_FREE_PAGES); x -= min(x, dirty_balance_reserve); + x += global_page_state(NR_INACTIVE_FILE); + x += global_page_state(NR_ACTIVE_FILE); + if (!vm_highmem_is_dirtyable) x -= highmem_dirtyable_memory(x); @@ -285,32 +292,6 @@ void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) } /** - * zone_dirtyable_memory - number of dirtyable pages in a zone - * @zone: the zone - * - * Returns the zone's number of pages potentially available for dirty - * page cache. This is the base value for the per-zone dirty limits. - */ -static unsigned long zone_dirtyable_memory(struct zone *zone) -{ - /* - * The effective global number of dirtyable pages may exclude - * highmem as a big-picture measure to keep the ratio between - * dirty memory and lowmem reasonable. - * - * But this function is purely about the individual zone and a - * highmem zone can hold its share of dirty pages, so we don't - * care about vm_highmem_is_dirtyable here. - */ - unsigned long nr_pages = zone_page_state(zone, NR_FREE_PAGES) + - zone_reclaimable_pages(zone); - - /* don't allow this to underflow */ - nr_pages -= min(nr_pages, zone->dirty_balance_reserve); - return nr_pages; -} - -/** * zone_dirty_limit - maximum number of dirty pages allowed in a zone * @zone: the zone * @@ -581,6 +562,37 @@ unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty) } /* + * 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 @@ -678,26 +690,80 @@ static unsigned long bdi_position_ratio(struct backing_dev_info *bdi, /* * global setpoint * - * setpoint - dirty 3 - * f(dirty) := 1.0 + (----------------) - * limit - setpoint + * See comment for pos_ratio_polynom(). + */ + setpoint = (freerun + limit) / 2; + pos_ratio = pos_ratio_polynom(setpoint, 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 bdi counters + * against bdi 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". * - * it's a 3rd order polynomial that subjects to + * Here, in bdi_position_ratio(), we calculate pos_ratio based on + * two values: bdi_dirty and bdi_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 bdi_thresh is 1% of 20% of 16GB. This amounts to ~8K pages. + * bdi_dirty_limit(bdi, bg_thresh) is about ~4K pages. bdi_setpoint is + * about ~6K pages (as the average of background and throttle bdi + * limits). The 3rd order polynomial will provide positive feedback if + * bdi_dirty is under bdi_setpoint and vice versa. * - * (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 + * Note, that we cannot use global counters in these calculations + * because we want to throttle process writing to a strictlimit BDI + * much earlier than global "freerun" is reached (~23MB vs. ~2.3GB + * in the example above). */ - setpoint = (freerun + limit) / 2; - x = div_s64((setpoint - dirty) << RATELIMIT_CALC_SHIFT, - limit - setpoint + 1); - pos_ratio = x; - pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; - pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; - pos_ratio += 1 << RATELIMIT_CALC_SHIFT; + if (unlikely(bdi->capabilities & BDI_CAP_STRICTLIMIT)) { + long long bdi_pos_ratio; + unsigned long bdi_bg_thresh; + + if (bdi_dirty < 8) + return min_t(long long, pos_ratio * 2, + 2 << RATELIMIT_CALC_SHIFT); + + if (bdi_dirty >= bdi_thresh) + return 0; + + bdi_bg_thresh = div_u64((u64)bdi_thresh * bg_thresh, thresh); + bdi_setpoint = dirty_freerun_ceiling(bdi_thresh, + bdi_bg_thresh); + + if (bdi_setpoint == 0 || bdi_setpoint == bdi_thresh) + return 0; + + bdi_pos_ratio = pos_ratio_polynom(bdi_setpoint, bdi_dirty, + bdi_thresh); + + /* + * Typically, for strictlimit case, bdi_setpoint << setpoint + * and pos_ratio >> bdi_pos_ratio. In the other words global + * state ("dirty") is not limiting factor and we have to + * make decision based on bdi 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 + * BDIs) while given strictlimit BDI is below limit. + * + * "pos_ratio * bdi_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 BDI + * 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 bdi is well below bdi + * 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. + */ + return min(pos_ratio, bdi_pos_ratio); + } /* * We have computed basic pos_ratio above based on global situation. If @@ -758,7 +824,7 @@ static unsigned long bdi_position_ratio(struct backing_dev_info *bdi, x_intercept = bdi_setpoint + span; if (bdi_dirty < x_intercept - span / 4) { - pos_ratio = div_u64(pos_ratio * (x_intercept - bdi_dirty), + pos_ratio = div64_u64(pos_ratio * (x_intercept - bdi_dirty), x_intercept - bdi_setpoint + 1); } else pos_ratio /= 4; @@ -990,6 +1056,27 @@ static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi, * keep that period small to reduce time lags). */ step = 0; + + /* + * For strictlimit case, calculations above were based on bdi counters + * and limits (starting from pos_ratio = bdi_position_ratio() and up to + * balanced_dirty_ratelimit = task_ratelimit * write_bw / dirty_rate). + * Hence, to calculate "step" properly, we have to use bdi_dirty as + * "dirty" and bdi_setpoint as "setpoint". + * + * We rampup dirty_ratelimit forcibly if bdi_dirty is low because + * it's possible that bdi_thresh is close to zero due to inactivity + * of backing device (see the implementation of bdi_dirty_limit()). + */ + if (unlikely(bdi->capabilities & BDI_CAP_STRICTLIMIT)) { + dirty = bdi_dirty; + if (bdi_dirty < 8) + setpoint = bdi_dirty + 1; + else + setpoint = (bdi_thresh + + bdi_dirty_limit(bdi, bg_thresh)) / 2; + } + if (dirty < setpoint) { x = min(bdi->balanced_dirty_ratelimit, min(balanced_dirty_ratelimit, task_ratelimit)); @@ -1100,11 +1187,11 @@ static unsigned long dirty_poll_interval(unsigned long dirty, return 1; } -static long bdi_max_pause(struct backing_dev_info *bdi, - unsigned long bdi_dirty) +static unsigned long bdi_max_pause(struct backing_dev_info *bdi, + unsigned long bdi_dirty) { - long bw = bdi->avg_write_bandwidth; - long t; + unsigned long bw = bdi->avg_write_bandwidth; + unsigned long t; /* * Limit pause time for small memory systems. If sleeping for too long @@ -1116,7 +1203,7 @@ static long bdi_max_pause(struct backing_dev_info *bdi, t = bdi_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8)); t++; - return min_t(long, t, MAX_PAUSE); + return min_t(unsigned long, t, MAX_PAUSE); } static long bdi_min_pause(struct backing_dev_info *bdi, @@ -1194,6 +1281,56 @@ static long bdi_min_pause(struct backing_dev_info *bdi, return pages >= DIRTY_POLL_THRESH ? 1 + t / 2 : t; } +static inline void bdi_dirty_limits(struct backing_dev_info *bdi, + unsigned long dirty_thresh, + unsigned long background_thresh, + unsigned long *bdi_dirty, + unsigned long *bdi_thresh, + unsigned long *bdi_bg_thresh) +{ + unsigned long bdi_reclaimable; + + /* + * bdi_thresh is not treated as some limiting factor as + * dirty_thresh, due to reasons + * - in JBOD setup, bdi_thresh can fluctuate a lot + * - in a system with HDD and USB key, the USB key may somehow + * go into state (bdi_dirty >> bdi_thresh) either because + * bdi_dirty starts high, or because bdi_thresh drops low. + * In this case we don't want to hard throttle the USB key + * dirtiers for 100 seconds until bdi_dirty drops under + * bdi_thresh. Instead the auxiliary bdi control line in + * bdi_position_ratio() will let the dirtier task progress + * at some rate <= (write_bw / 2) for bringing down bdi_dirty. + */ + *bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh); + + if (bdi_bg_thresh) + *bdi_bg_thresh = dirty_thresh ? div_u64((u64)*bdi_thresh * + background_thresh, + dirty_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 (*bdi_thresh < 2 * bdi_stat_error(bdi)) { + bdi_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); + *bdi_dirty = bdi_reclaimable + + bdi_stat_sum(bdi, BDI_WRITEBACK); + } else { + bdi_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); + *bdi_dirty = bdi_reclaimable + + bdi_stat(bdi, BDI_WRITEBACK); + } +} + /* * 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 @@ -1205,13 +1342,9 @@ static void balance_dirty_pages(struct address_space *mapping, unsigned long pages_dirtied) { unsigned long nr_reclaimable; /* = file_dirty + unstable_nfs */ - unsigned long bdi_reclaimable; unsigned long nr_dirty; /* = file_dirty + writeback + unstable_nfs */ - unsigned long bdi_dirty; - unsigned long freerun; unsigned long background_thresh; unsigned long dirty_thresh; - unsigned long bdi_thresh; long period; long pause; long max_pause; @@ -1222,10 +1355,16 @@ static void balance_dirty_pages(struct address_space *mapping, unsigned long dirty_ratelimit; unsigned long pos_ratio; struct backing_dev_info *bdi = mapping->backing_dev_info; + bool strictlimit = bdi->capabilities & BDI_CAP_STRICTLIMIT; unsigned long start_time = jiffies; for (;;) { unsigned long now = jiffies; + unsigned long uninitialized_var(bdi_thresh); + unsigned long thresh; + unsigned long uninitialized_var(bdi_dirty); + unsigned long dirty; + unsigned long bg_thresh; /* * Unstable writes are a feature of certain networked @@ -1239,61 +1378,44 @@ static void balance_dirty_pages(struct address_space *mapping, global_dirty_limits(&background_thresh, &dirty_thresh); + if (unlikely(strictlimit)) { + bdi_dirty_limits(bdi, dirty_thresh, background_thresh, + &bdi_dirty, &bdi_thresh, &bg_thresh); + + dirty = bdi_dirty; + thresh = bdi_thresh; + } else { + dirty = nr_dirty; + thresh = dirty_thresh; + bg_thresh = background_thresh; + } + /* * Throttle it only when the background writeback cannot * catch-up. This avoids (excessively) small writeouts - * when the bdi limits are ramping up. + * when the bdi limits are ramping up in case of !strictlimit. + * + * In strictlimit case make decision based on the bdi counters + * and limits. Small writeouts when the bdi limits are ramping + * up are the price we consciously pay for strictlimit-ing. */ - freerun = dirty_freerun_ceiling(dirty_thresh, - background_thresh); - if (nr_dirty <= freerun) { + if (dirty <= dirty_freerun_ceiling(thresh, bg_thresh)) { current->dirty_paused_when = now; current->nr_dirtied = 0; current->nr_dirtied_pause = - dirty_poll_interval(nr_dirty, dirty_thresh); + dirty_poll_interval(dirty, thresh); break; } if (unlikely(!writeback_in_progress(bdi))) bdi_start_background_writeback(bdi); - /* - * bdi_thresh is not treated as some limiting factor as - * dirty_thresh, due to reasons - * - in JBOD setup, bdi_thresh can fluctuate a lot - * - in a system with HDD and USB key, the USB key may somehow - * go into state (bdi_dirty >> bdi_thresh) either because - * bdi_dirty starts high, or because bdi_thresh drops low. - * In this case we don't want to hard throttle the USB key - * dirtiers for 100 seconds until bdi_dirty drops under - * bdi_thresh. Instead the auxiliary bdi control line in - * bdi_position_ratio() will let the dirtier task progress - * at some rate <= (write_bw / 2) for bringing down bdi_dirty. - */ - bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh); - - /* - * 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_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); - bdi_dirty = bdi_reclaimable + - bdi_stat_sum(bdi, BDI_WRITEBACK); - } else { - bdi_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); - bdi_dirty = bdi_reclaimable + - bdi_stat(bdi, BDI_WRITEBACK); - } + if (!strictlimit) + bdi_dirty_limits(bdi, dirty_thresh, background_thresh, + &bdi_dirty, &bdi_thresh, NULL); dirty_exceeded = (bdi_dirty > bdi_thresh) && - (nr_dirty > dirty_thresh); + ((nr_dirty > dirty_thresh) || strictlimit); if (dirty_exceeded && !bdi->dirty_exceeded) bdi->dirty_exceeded = 1; @@ -1422,9 +1544,9 @@ pause: bdi_start_background_writeback(bdi); } -void set_page_dirty_balance(struct page *page, int page_mkwrite) +void set_page_dirty_balance(struct page *page) { - if (set_page_dirty(page) || page_mkwrite) { + if (set_page_dirty(page)) { struct address_space *mapping = page_mapping(page); if (mapping) @@ -1483,7 +1605,7 @@ void balance_dirty_pages_ratelimited(struct address_space *mapping) * 1000+ tasks, all of them start dirtying pages at exactly the same * time, hence all honoured too large initial task->nr_dirtied_pause. */ - p = &__get_cpu_var(bdp_ratelimits); + p = this_cpu_ptr(&bdp_ratelimits); if (unlikely(current->nr_dirtied >= ratelimit)) *p = 0; else if (unlikely(*p >= ratelimit_pages)) { @@ -1495,7 +1617,7 @@ void balance_dirty_pages_ratelimited(struct address_space *mapping) * short-lived tasks (eg. gcc invocations in a kernel build) escaping * the dirty throttling and livelock other long-run dirtiers. */ - p = &__get_cpu_var(dirty_throttle_leaks); + 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); @@ -1542,7 +1664,7 @@ void throttle_vm_writeout(gfp_t gfp_mask) /* * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs */ -int dirty_writeback_centisecs_handler(ctl_table *table, int write, +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); @@ -1615,7 +1737,7 @@ void writeback_set_ratelimit(void) ratelimit_pages = 16; } -static int __cpuinit +static int ratelimit_handler(struct notifier_block *self, unsigned long action, void *hcpu) { @@ -1630,7 +1752,7 @@ ratelimit_handler(struct notifier_block *self, unsigned long action, } } -static struct notifier_block __cpuinitdata ratelimit_nb = { +static struct notifier_block ratelimit_nb = { .notifier_call = ratelimit_handler, .next = NULL, }; @@ -1982,6 +2104,8 @@ int __set_page_dirty_no_writeback(struct page *page) */ void account_page_dirtied(struct page *page, struct address_space *mapping) { + trace_writeback_dirty_page(page, mapping); + if (mapping_cap_account_dirty(mapping)) { __inc_zone_page_state(page, NR_FILE_DIRTY); __inc_zone_page_state(page, NR_DIRTIED); @@ -1996,11 +2120,17 @@ EXPORT_SYMBOL(account_page_dirtied); /* * Helper function for set_page_writeback family. + * + * The caller must hold mem_cgroup_begin/end_update_page_stat() lock + * while calling this function. + * See test_set_page_writeback for example. + * * NOTE: Unlike account_page_dirtied this does not rely on being atomic * wrt interrupts. */ void account_page_writeback(struct page *page) { + mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_WRITEBACK); inc_zone_page_state(page, NR_WRITEBACK); } EXPORT_SYMBOL(account_page_writeback); @@ -2025,11 +2155,12 @@ int __set_page_dirty_nobuffers(struct page *page) if (!TestSetPageDirty(page)) { struct address_space *mapping = page_mapping(page); struct address_space *mapping2; + unsigned long flags; if (!mapping) return 1; - spin_lock_irq(&mapping->tree_lock); + spin_lock_irqsave(&mapping->tree_lock, flags); mapping2 = page_mapping(page); if (mapping2) { /* Race with truncate? */ BUG_ON(mapping2 != mapping); @@ -2038,7 +2169,7 @@ int __set_page_dirty_nobuffers(struct page *page) radix_tree_tag_set(&mapping->page_tree, page_index(page), PAGECACHE_TAG_DIRTY); } - spin_unlock_irq(&mapping->tree_lock); + spin_unlock_irqrestore(&mapping->tree_lock, flags); if (mapping->host) { /* !PageAnon && !swapper_space */ __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); @@ -2217,7 +2348,10 @@ int test_clear_page_writeback(struct page *page) { struct address_space *mapping = page_mapping(page); int ret; + bool locked; + unsigned long memcg_flags; + mem_cgroup_begin_update_page_stat(page, &locked, &memcg_flags); if (mapping) { struct backing_dev_info *bdi = mapping->backing_dev_info; unsigned long flags; @@ -2238,17 +2372,22 @@ int test_clear_page_writeback(struct page *page) ret = TestClearPageWriteback(page); } if (ret) { + mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_WRITEBACK); dec_zone_page_state(page, NR_WRITEBACK); inc_zone_page_state(page, NR_WRITTEN); } + mem_cgroup_end_update_page_stat(page, &locked, &memcg_flags); return ret; } -int test_set_page_writeback(struct page *page) +int __test_set_page_writeback(struct page *page, bool keep_write) { struct address_space *mapping = page_mapping(page); int ret; + bool locked; + unsigned long memcg_flags; + mem_cgroup_begin_update_page_stat(page, &locked, &memcg_flags); if (mapping) { struct backing_dev_info *bdi = mapping->backing_dev_info; unsigned long flags; @@ -2266,19 +2405,21 @@ int test_set_page_writeback(struct page *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); + 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) account_page_writeback(page); + mem_cgroup_end_update_page_stat(page, &locked, &memcg_flags); return ret; } -EXPORT_SYMBOL(test_set_page_writeback); +EXPORT_SYMBOL(__test_set_page_writeback); /* * Return true if any of the pages in the mapping are marked with the @@ -2289,3 +2430,23 @@ 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) +{ + struct address_space *mapping = page_mapping(page); + struct backing_dev_info *bdi = mapping->backing_dev_info; + + if (!bdi_cap_stable_pages_required(bdi)) + return; + + wait_on_page_writeback(page); +} +EXPORT_SYMBOL_GPL(wait_for_stable_page); |