mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
synced 2024-12-29 09:12:07 +00:00
fdd96c5971
Address the feedback from 39ac99852f ("mm/page-writeback: raise
wb_thresh to prevent write blocking with strictlimit)". The wb_thresh
bumping logic is scattered across wb_position_ratio, __wb_calc_thresh, and
wb_update_dirty_ratelimit. For consistency, consolidate all wb_thresh
bumping logic into __wb_calc_thresh.
Link: https://lkml.kernel.org/r/20241121100539.605818-1-jimzhao.ai@gmail.com
Signed-off-by: Jim Zhao <jimzhao.ai@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
3222 lines
96 KiB
C
3222 lines
96 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
|
|
/*
|
|
* 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/math64.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/smp.h>
|
|
#include <linux/sysctl.h>
|
|
#include <linux/cpu.h>
|
|
#include <linux/syscalls.h>
|
|
#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 or update dirty limit 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
|
|
*/
|
|
static 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
|
|
*/
|
|
static 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
|
|
*/
|
|
static int vm_highmem_is_dirtyable;
|
|
|
|
/*
|
|
* The generator of dirty data starts writeback at this percentage
|
|
*/
|
|
static 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
|
|
*/
|
|
static 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 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;
|
|
bool freerun;
|
|
bool dirty_exceeded;
|
|
};
|
|
|
|
/*
|
|
* 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 = READ_ONCE(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;
|
|
min = div64_ul(min, tot_bw);
|
|
}
|
|
if (max < 100 * BDI_RATIO_SCALE) {
|
|
max *= this_bw;
|
|
max = div64_ul(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 effective 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
|
|
*
|
|
* Return: 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;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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
|
|
*
|
|
* Return: 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 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;
|
|
|
|
tsk = current;
|
|
if (rt_or_dl_task(tsk)) {
|
|
bg_thresh += bg_thresh / 4 + global_wb_domain.dirty_limit / 32;
|
|
thresh += thresh / 4 + global_wb_domain.dirty_limit / 32;
|
|
}
|
|
/*
|
|
* Dirty throttling logic assumes the limits in page units fit into
|
|
* 32-bits. This gives 16TB dirty limits max which is hopefully enough.
|
|
*/
|
|
if (thresh > UINT_MAX)
|
|
thresh = UINT_MAX;
|
|
/* This makes sure bg_thresh is within 32-bits as well */
|
|
if (bg_thresh >= thresh)
|
|
bg_thresh = thresh / 2;
|
|
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
|
|
*
|
|
* Return: 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 (rt_or_dl_task(tsk))
|
|
dirty += dirty / 4;
|
|
|
|
/*
|
|
* Dirty throttling logic assumes the limits in page units fit into
|
|
* 32-bits. This gives 16TB dirty limits max which is hopefully enough.
|
|
*/
|
|
return min_t(unsigned long, dirty, UINT_MAX);
|
|
}
|
|
|
|
/**
|
|
* node_dirty_ok - tells whether a node is within its dirty limits
|
|
* @pgdat: the node to check
|
|
*
|
|
* Return: %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_WRITEBACK);
|
|
|
|
return nr_pages <= limit;
|
|
}
|
|
|
|
#ifdef CONFIG_SYSCTL
|
|
static int dirty_background_ratio_handler(const struct ctl_table *table, int write,
|
|
void *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;
|
|
}
|
|
|
|
static int dirty_background_bytes_handler(const struct ctl_table *table, int write,
|
|
void *buffer, size_t *lenp, loff_t *ppos)
|
|
{
|
|
int ret;
|
|
unsigned long old_bytes = dirty_background_bytes;
|
|
|
|
ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
|
|
if (ret == 0 && write) {
|
|
if (DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE) >
|
|
UINT_MAX) {
|
|
dirty_background_bytes = old_bytes;
|
|
return -ERANGE;
|
|
}
|
|
dirty_background_ratio = 0;
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
static int dirty_ratio_handler(const struct ctl_table *table, int write, void *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;
|
|
}
|
|
|
|
static int dirty_bytes_handler(const struct ctl_table *table, int write,
|
|
void *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) {
|
|
if (DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE) > UINT_MAX) {
|
|
vm_dirty_bytes = old_bytes;
|
|
return -ERANGE;
|
|
}
|
|
writeback_set_ratelimit();
|
|
vm_dirty_ratio = 0;
|
|
}
|
|
return ret;
|
|
}
|
|
#endif
|
|
|
|
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_add(struct wb_domain *dom,
|
|
struct fprop_local_percpu *completions,
|
|
unsigned int max_prop_frac, long nr)
|
|
{
|
|
__fprop_add_percpu_max(&dom->completions, completions,
|
|
max_prop_frac, nr);
|
|
/* First event after period switching was turned off? */
|
|
if (unlikely(!dom->period_time)) {
|
|
/*
|
|
* We can race with other wb_domain_writeout_add 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 __folio_end_writeback().
|
|
*/
|
|
static inline void __wb_writeout_add(struct bdi_writeback *wb, long nr)
|
|
{
|
|
struct wb_domain *cgdom;
|
|
|
|
wb_stat_mod(wb, WB_WRITTEN, nr);
|
|
wb_domain_writeout_add(&global_wb_domain, &wb->completions,
|
|
wb->bdi->max_prop_frac, nr);
|
|
|
|
cgdom = mem_cgroup_wb_domain(wb);
|
|
if (cgdom)
|
|
wb_domain_writeout_add(cgdom, wb_memcg_completions(wb),
|
|
wb->bdi->max_prop_frac, nr);
|
|
}
|
|
|
|
void wb_writeout_inc(struct bdi_writeback *wb)
|
|
{
|
|
unsigned long flags;
|
|
|
|
local_irq_save(flags);
|
|
__wb_writeout_add(wb, 1);
|
|
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(struct timer_list *t)
|
|
{
|
|
struct wb_domain *dom = from_timer(dom, t, period_timer);
|
|
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);
|
|
|
|
timer_setup(&dom->period_timer, writeout_period, TIMER_DEFERRABLE);
|
|
|
|
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;
|
|
|
|
static int bdi_check_pages_limit(unsigned long pages)
|
|
{
|
|
unsigned long max_dirty_pages = global_dirtyable_memory();
|
|
|
|
if (pages > max_dirty_pages)
|
|
return -EINVAL;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static unsigned long bdi_ratio_from_pages(unsigned long pages)
|
|
{
|
|
unsigned long background_thresh;
|
|
unsigned long dirty_thresh;
|
|
unsigned long ratio;
|
|
|
|
global_dirty_limits(&background_thresh, &dirty_thresh);
|
|
ratio = div64_u64(pages * 100ULL * BDI_RATIO_SCALE, dirty_thresh);
|
|
|
|
return ratio;
|
|
}
|
|
|
|
static u64 bdi_get_bytes(unsigned int ratio)
|
|
{
|
|
unsigned long background_thresh;
|
|
unsigned long dirty_thresh;
|
|
u64 bytes;
|
|
|
|
global_dirty_limits(&background_thresh, &dirty_thresh);
|
|
bytes = (dirty_thresh * PAGE_SIZE * ratio) / BDI_RATIO_SCALE / 100;
|
|
|
|
return bytes;
|
|
}
|
|
|
|
static int __bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
|
|
{
|
|
unsigned int delta;
|
|
int ret = 0;
|
|
|
|
if (min_ratio > 100 * BDI_RATIO_SCALE)
|
|
return -EINVAL;
|
|
|
|
spin_lock_bh(&bdi_lock);
|
|
if (min_ratio > bdi->max_ratio) {
|
|
ret = -EINVAL;
|
|
} else {
|
|
if (min_ratio < bdi->min_ratio) {
|
|
delta = bdi->min_ratio - min_ratio;
|
|
bdi_min_ratio -= delta;
|
|
bdi->min_ratio = min_ratio;
|
|
} else {
|
|
delta = min_ratio - bdi->min_ratio;
|
|
if (bdi_min_ratio + delta < 100 * BDI_RATIO_SCALE) {
|
|
bdi_min_ratio += delta;
|
|
bdi->min_ratio = min_ratio;
|
|
} else {
|
|
ret = -EINVAL;
|
|
}
|
|
}
|
|
}
|
|
spin_unlock_bh(&bdi_lock);
|
|
|
|
return ret;
|
|
}
|
|
|
|
static int __bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio)
|
|
{
|
|
int ret = 0;
|
|
|
|
if (max_ratio > 100 * BDI_RATIO_SCALE)
|
|
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 * BDI_RATIO_SCALE);
|
|
}
|
|
spin_unlock_bh(&bdi_lock);
|
|
|
|
return ret;
|
|
}
|
|
|
|
int bdi_set_min_ratio_no_scale(struct backing_dev_info *bdi, unsigned int min_ratio)
|
|
{
|
|
return __bdi_set_min_ratio(bdi, min_ratio);
|
|
}
|
|
|
|
int bdi_set_max_ratio_no_scale(struct backing_dev_info *bdi, unsigned int max_ratio)
|
|
{
|
|
return __bdi_set_max_ratio(bdi, max_ratio);
|
|
}
|
|
|
|
int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
|
|
{
|
|
return __bdi_set_min_ratio(bdi, min_ratio * BDI_RATIO_SCALE);
|
|
}
|
|
|
|
int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio)
|
|
{
|
|
return __bdi_set_max_ratio(bdi, max_ratio * BDI_RATIO_SCALE);
|
|
}
|
|
EXPORT_SYMBOL(bdi_set_max_ratio);
|
|
|
|
u64 bdi_get_min_bytes(struct backing_dev_info *bdi)
|
|
{
|
|
return bdi_get_bytes(bdi->min_ratio);
|
|
}
|
|
|
|
int bdi_set_min_bytes(struct backing_dev_info *bdi, u64 min_bytes)
|
|
{
|
|
int ret;
|
|
unsigned long pages = min_bytes >> PAGE_SHIFT;
|
|
unsigned long min_ratio;
|
|
|
|
ret = bdi_check_pages_limit(pages);
|
|
if (ret)
|
|
return ret;
|
|
|
|
min_ratio = bdi_ratio_from_pages(pages);
|
|
return __bdi_set_min_ratio(bdi, min_ratio);
|
|
}
|
|
|
|
u64 bdi_get_max_bytes(struct backing_dev_info *bdi)
|
|
{
|
|
return bdi_get_bytes(bdi->max_ratio);
|
|
}
|
|
|
|
int bdi_set_max_bytes(struct backing_dev_info *bdi, u64 max_bytes)
|
|
{
|
|
int ret;
|
|
unsigned long pages = max_bytes >> PAGE_SHIFT;
|
|
unsigned long max_ratio;
|
|
|
|
ret = bdi_check_pages_limit(pages);
|
|
if (ret)
|
|
return ret;
|
|
|
|
max_ratio = bdi_ratio_from_pages(pages);
|
|
return __bdi_set_max_ratio(bdi, max_ratio);
|
|
}
|
|
|
|
int bdi_set_strict_limit(struct backing_dev_info *bdi, unsigned int strict_limit)
|
|
{
|
|
if (strict_limit > 1)
|
|
return -EINVAL;
|
|
|
|
spin_lock_bh(&bdi_lock);
|
|
if (strict_limit)
|
|
bdi->capabilities |= BDI_CAP_STRICTLIMIT;
|
|
else
|
|
bdi->capabilities &= ~BDI_CAP_STRICTLIMIT;
|
|
spin_unlock_bh(&bdi_lock);
|
|
|
|
return 0;
|
|
}
|
|
|
|
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);
|
|
}
|
|
|
|
static inline bool dtc_is_global(struct dirty_throttle_control *dtc)
|
|
{
|
|
return mdtc_gdtc(dtc) == NULL;
|
|
}
|
|
|
|
/*
|
|
* Dirty background will ignore pages being written as we're trying to
|
|
* decide whether to put more under writeback.
|
|
*/
|
|
static void domain_dirty_avail(struct dirty_throttle_control *dtc,
|
|
bool include_writeback)
|
|
{
|
|
if (dtc_is_global(dtc)) {
|
|
dtc->avail = global_dirtyable_memory();
|
|
dtc->dirty = global_node_page_state(NR_FILE_DIRTY);
|
|
if (include_writeback)
|
|
dtc->dirty += global_node_page_state(NR_WRITEBACK);
|
|
} else {
|
|
unsigned long filepages = 0, headroom = 0, writeback = 0;
|
|
|
|
mem_cgroup_wb_stats(dtc->wb, &filepages, &headroom, &dtc->dirty,
|
|
&writeback);
|
|
if (include_writeback)
|
|
dtc->dirty += writeback;
|
|
mdtc_calc_avail(dtc, filepages, headroom);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* __wb_calc_thresh - @wb's share of dirty threshold
|
|
* @dtc: dirty_throttle_context of interest
|
|
* @thresh: dirty throttling or dirty background threshold of wb_domain in @dtc
|
|
*
|
|
* Note that balance_dirty_pages() will only seriously take dirty throttling
|
|
* threshold 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.
|
|
*
|
|
* Return: @wb's dirty limit in pages. For dirty throttling limit, the term
|
|
* "dirty" in the context of dirty balancing includes all PG_dirty and
|
|
* PG_writeback pages.
|
|
*/
|
|
static unsigned long __wb_calc_thresh(struct dirty_throttle_control *dtc,
|
|
unsigned long thresh)
|
|
{
|
|
struct wb_domain *dom = dtc_dom(dtc);
|
|
struct bdi_writeback *wb = dtc->wb;
|
|
u64 wb_thresh;
|
|
u64 wb_max_thresh;
|
|
unsigned long numerator, denominator;
|
|
unsigned long wb_min_ratio, wb_max_ratio;
|
|
|
|
/*
|
|
* Calculate this wb's share of the thresh ratio.
|
|
*/
|
|
fprop_fraction_percpu(&dom->completions, dtc->wb_completions,
|
|
&numerator, &denominator);
|
|
|
|
wb_thresh = (thresh * (100 * BDI_RATIO_SCALE - bdi_min_ratio)) / (100 * BDI_RATIO_SCALE);
|
|
wb_thresh *= numerator;
|
|
wb_thresh = div64_ul(wb_thresh, denominator);
|
|
|
|
wb_min_max_ratio(wb, &wb_min_ratio, &wb_max_ratio);
|
|
|
|
wb_thresh += (thresh * wb_min_ratio) / (100 * BDI_RATIO_SCALE);
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
if (thresh > dtc->dirty) {
|
|
if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT))
|
|
wb_thresh = max(wb_thresh, (thresh - dtc->dirty) / 100);
|
|
else
|
|
wb_thresh = max(wb_thresh, (thresh - dtc->dirty) / 8);
|
|
}
|
|
|
|
wb_max_thresh = thresh * wb_max_ratio / (100 * BDI_RATIO_SCALE);
|
|
if (wb_thresh > wb_max_thresh)
|
|
wb_thresh = wb_max_thresh;
|
|
|
|
return wb_thresh;
|
|
}
|
|
|
|
unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh)
|
|
{
|
|
struct dirty_throttle_control gdtc = { GDTC_INIT(wb) };
|
|
|
|
domain_dirty_avail(&gdtc, true);
|
|
return __wb_calc_thresh(&gdtc, thresh);
|
|
}
|
|
|
|
unsigned long cgwb_calc_thresh(struct bdi_writeback *wb)
|
|
{
|
|
struct dirty_throttle_control gdtc = { GDTC_INIT_NO_WB };
|
|
struct dirty_throttle_control mdtc = { MDTC_INIT(wb, &gdtc) };
|
|
|
|
domain_dirty_avail(&gdtc, true);
|
|
domain_dirty_avail(&mdtc, true);
|
|
domain_dirty_limits(&mdtc);
|
|
|
|
return __wb_calc_thresh(&mdtc, mdtc.thresh);
|
|
}
|
|
|
|
/*
|
|
* 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 = READ_ONCE(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 >= 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;
|
|
/*
|
|
* 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 folio_redirty_for_writepage().
|
|
* Avoid underflowing @bw calculation.
|
|
*/
|
|
bw = written - min(written, wb->written_stamp);
|
|
bw *= HZ;
|
|
if (unlikely(elapsed > period)) {
|
|
bw = div64_ul(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;
|
|
WRITE_ONCE(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_dirty_limit(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".
|
|
*/
|
|
if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) {
|
|
dirty = dtc->wb_dirty;
|
|
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;
|
|
|
|
WRITE_ONCE(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,
|
|
bool update_ratelimit)
|
|
{
|
|
struct bdi_writeback *wb = gdtc->wb;
|
|
unsigned long now = jiffies;
|
|
unsigned long elapsed;
|
|
unsigned long dirtied;
|
|
unsigned long written;
|
|
|
|
spin_lock(&wb->list_lock);
|
|
|
|
/*
|
|
* Lockless checks for elapsed time are racy and delayed update after
|
|
* IO completion doesn't do it at all (to make sure written pages are
|
|
* accounted reasonably quickly). Make sure elapsed >= 1 to avoid
|
|
* division errors.
|
|
*/
|
|
elapsed = max(now - wb->bw_time_stamp, 1UL);
|
|
dirtied = percpu_counter_read(&wb->stat[WB_DIRTIED]);
|
|
written = percpu_counter_read(&wb->stat[WB_WRITTEN]);
|
|
|
|
if (update_ratelimit) {
|
|
domain_update_dirty_limit(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_dirty_limit(mdtc, now);
|
|
wb_update_dirty_ratelimit(mdtc, dirtied, elapsed);
|
|
}
|
|
}
|
|
wb_update_write_bandwidth(wb, elapsed, written);
|
|
|
|
wb->dirtied_stamp = dirtied;
|
|
wb->written_stamp = written;
|
|
WRITE_ONCE(wb->bw_time_stamp, now);
|
|
spin_unlock(&wb->list_lock);
|
|
}
|
|
|
|
void wb_update_bandwidth(struct bdi_writeback *wb)
|
|
{
|
|
struct dirty_throttle_control gdtc = { GDTC_INIT(wb) };
|
|
|
|
__wb_update_bandwidth(&gdtc, NULL, false);
|
|
}
|
|
|
|
/* Interval after which we consider wb idle and don't estimate bandwidth */
|
|
#define WB_BANDWIDTH_IDLE_JIF (HZ)
|
|
|
|
static void wb_bandwidth_estimate_start(struct bdi_writeback *wb)
|
|
{
|
|
unsigned long now = jiffies;
|
|
unsigned long elapsed = now - READ_ONCE(wb->bw_time_stamp);
|
|
|
|
if (elapsed > WB_BANDWIDTH_IDLE_JIF &&
|
|
!atomic_read(&wb->writeback_inodes)) {
|
|
spin_lock(&wb->list_lock);
|
|
wb->dirtied_stamp = wb_stat(wb, WB_DIRTIED);
|
|
wb->written_stamp = wb_stat(wb, WB_WRITTEN);
|
|
WRITE_ONCE(wb->bw_time_stamp, now);
|
|
spin_unlock(&wb->list_lock);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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 = READ_ONCE(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(READ_ONCE(wb->avg_write_bandwidth));
|
|
long lo = ilog2(READ_ONCE(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->thresh);
|
|
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_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);
|
|
}
|
|
}
|
|
|
|
static unsigned long domain_poll_intv(struct dirty_throttle_control *dtc,
|
|
bool strictlimit)
|
|
{
|
|
unsigned long dirty, thresh;
|
|
|
|
if (strictlimit) {
|
|
dirty = dtc->wb_dirty;
|
|
thresh = dtc->wb_thresh;
|
|
} else {
|
|
dirty = dtc->dirty;
|
|
thresh = dtc->thresh;
|
|
}
|
|
|
|
return dirty_poll_interval(dirty, 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.
|
|
*/
|
|
static void domain_dirty_freerun(struct dirty_throttle_control *dtc,
|
|
bool strictlimit)
|
|
{
|
|
unsigned long dirty, thresh, bg_thresh;
|
|
|
|
if (unlikely(strictlimit)) {
|
|
wb_dirty_limits(dtc);
|
|
dirty = dtc->wb_dirty;
|
|
thresh = dtc->wb_thresh;
|
|
bg_thresh = dtc->wb_bg_thresh;
|
|
} else {
|
|
dirty = dtc->dirty;
|
|
thresh = dtc->thresh;
|
|
bg_thresh = dtc->bg_thresh;
|
|
}
|
|
dtc->freerun = dirty <= dirty_freerun_ceiling(thresh, bg_thresh);
|
|
}
|
|
|
|
static void balance_domain_limits(struct dirty_throttle_control *dtc,
|
|
bool strictlimit)
|
|
{
|
|
domain_dirty_avail(dtc, true);
|
|
domain_dirty_limits(dtc);
|
|
domain_dirty_freerun(dtc, strictlimit);
|
|
}
|
|
|
|
static void wb_dirty_freerun(struct dirty_throttle_control *dtc,
|
|
bool strictlimit)
|
|
{
|
|
dtc->freerun = false;
|
|
|
|
/* was already handled in domain_dirty_freerun */
|
|
if (strictlimit)
|
|
return;
|
|
|
|
wb_dirty_limits(dtc);
|
|
/*
|
|
* LOCAL_THROTTLE tasks must not be throttled when below the per-wb
|
|
* freerun ceiling.
|
|
*/
|
|
if (!(current->flags & PF_LOCAL_THROTTLE))
|
|
return;
|
|
|
|
dtc->freerun = dtc->wb_dirty <
|
|
dirty_freerun_ceiling(dtc->wb_thresh, dtc->wb_bg_thresh);
|
|
}
|
|
|
|
static inline void wb_dirty_exceeded(struct dirty_throttle_control *dtc,
|
|
bool strictlimit)
|
|
{
|
|
dtc->dirty_exceeded = (dtc->wb_dirty > dtc->wb_thresh) &&
|
|
((dtc->dirty > dtc->thresh) || strictlimit);
|
|
}
|
|
|
|
/*
|
|
* The limits fields dirty_exceeded and pos_ratio won't be updated if wb is
|
|
* in freerun state. Please don't use these invalid fields in freerun case.
|
|
*/
|
|
static void balance_wb_limits(struct dirty_throttle_control *dtc,
|
|
bool strictlimit)
|
|
{
|
|
wb_dirty_freerun(dtc, strictlimit);
|
|
if (dtc->freerun)
|
|
return;
|
|
|
|
wb_dirty_exceeded(dtc, strictlimit);
|
|
wb_position_ratio(dtc);
|
|
}
|
|
|
|
/*
|
|
* 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 int balance_dirty_pages(struct bdi_writeback *wb,
|
|
unsigned long pages_dirtied, unsigned int flags)
|
|
{
|
|
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_dirty;
|
|
long period;
|
|
long pause;
|
|
long max_pause;
|
|
long min_pause;
|
|
int nr_dirtied_pause;
|
|
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;
|
|
int ret = 0;
|
|
|
|
for (;;) {
|
|
unsigned long now = jiffies;
|
|
|
|
nr_dirty = global_node_page_state(NR_FILE_DIRTY);
|
|
|
|
balance_domain_limits(gdtc, strictlimit);
|
|
if (mdtc) {
|
|
/*
|
|
* If @wb belongs to !root memcg, repeat the same
|
|
* basic calculations for the memcg domain.
|
|
*/
|
|
balance_domain_limits(mdtc, strictlimit);
|
|
}
|
|
|
|
/*
|
|
* 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 && nr_dirty > gdtc->bg_thresh &&
|
|
!writeback_in_progress(wb))
|
|
wb_start_background_writeback(wb);
|
|
|
|
/*
|
|
* If memcg domain is in effect, @dirty should be under
|
|
* both global and memcg freerun ceilings.
|
|
*/
|
|
if (gdtc->freerun && (!mdtc || mdtc->freerun)) {
|
|
unsigned long intv;
|
|
unsigned long m_intv;
|
|
|
|
free_running:
|
|
intv = domain_poll_intv(gdtc, strictlimit);
|
|
m_intv = ULONG_MAX;
|
|
|
|
current->dirty_paused_when = now;
|
|
current->nr_dirtied = 0;
|
|
if (mdtc)
|
|
m_intv = domain_poll_intv(mdtc, strictlimit);
|
|
current->nr_dirtied_pause = min(intv, m_intv);
|
|
break;
|
|
}
|
|
|
|
/* Start writeback even when in laptop mode */
|
|
if (unlikely(!writeback_in_progress(wb)))
|
|
wb_start_background_writeback(wb);
|
|
|
|
mem_cgroup_flush_foreign(wb);
|
|
|
|
/*
|
|
* Calculate global domain's pos_ratio and select the
|
|
* global dtc by default.
|
|
*/
|
|
balance_wb_limits(gdtc, strictlimit);
|
|
if (gdtc->freerun)
|
|
goto free_running;
|
|
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.
|
|
*/
|
|
balance_wb_limits(mdtc, strictlimit);
|
|
if (mdtc->freerun)
|
|
goto free_running;
|
|
if (mdtc->pos_ratio < gdtc->pos_ratio)
|
|
sdtc = mdtc;
|
|
}
|
|
|
|
wb->dirty_exceeded = gdtc->dirty_exceeded ||
|
|
(mdtc && mdtc->dirty_exceeded);
|
|
if (time_is_before_jiffies(READ_ONCE(wb->bw_time_stamp) +
|
|
BANDWIDTH_INTERVAL))
|
|
__wb_update_bandwidth(gdtc, mdtc, true);
|
|
|
|
/* throttle according to the chosen dtc */
|
|
dirty_ratelimit = READ_ONCE(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);
|
|
if (flags & BDP_ASYNC) {
|
|
ret = -EAGAIN;
|
|
break;
|
|
}
|
|
__set_current_state(TASK_KILLABLE);
|
|
bdi->last_bdp_sleep = jiffies;
|
|
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 unresponsive 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())
|
|
break;
|
|
|
|
if (fatal_signal_pending(current))
|
|
break;
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
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_flags - Balance dirty memory state.
|
|
* @mapping: address_space which was dirtied.
|
|
* @flags: BDP flags.
|
|
*
|
|
* 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.
|
|
*
|
|
* See balance_dirty_pages_ratelimited() for details.
|
|
*
|
|
* Return: If @flags contains BDP_ASYNC, it may return -EAGAIN to
|
|
* indicate that memory is out of balance and the caller must wait
|
|
* for I/O to complete. Otherwise, it will return 0 to indicate
|
|
* that either memory was already in balance, or it was able to sleep
|
|
* until the amount of dirty memory returned to balance.
|
|
*/
|
|
int balance_dirty_pages_ratelimited_flags(struct address_space *mapping,
|
|
unsigned int flags)
|
|
{
|
|
struct inode *inode = mapping->host;
|
|
struct backing_dev_info *bdi = inode_to_bdi(inode);
|
|
struct bdi_writeback *wb = NULL;
|
|
int ratelimit;
|
|
int ret = 0;
|
|
int *p;
|
|
|
|
if (!(bdi->capabilities & BDI_CAP_WRITEBACK))
|
|
return ret;
|
|
|
|
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))
|
|
ret = balance_dirty_pages(wb, current->nr_dirtied, flags);
|
|
|
|
wb_put(wb);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(balance_dirty_pages_ratelimited_flags);
|
|
|
|
/**
|
|
* 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.
|
|
*
|
|
* 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)
|
|
{
|
|
balance_dirty_pages_ratelimited_flags(mapping, 0);
|
|
}
|
|
EXPORT_SYMBOL(balance_dirty_pages_ratelimited);
|
|
|
|
/*
|
|
* Similar to wb_dirty_limits, wb_bg_dirty_limits also calculates dirty
|
|
* and thresh, but it's for background writeback.
|
|
*/
|
|
static void wb_bg_dirty_limits(struct dirty_throttle_control *dtc)
|
|
{
|
|
struct bdi_writeback *wb = dtc->wb;
|
|
|
|
dtc->wb_bg_thresh = __wb_calc_thresh(dtc, dtc->bg_thresh);
|
|
if (dtc->wb_bg_thresh < 2 * wb_stat_error())
|
|
dtc->wb_dirty = wb_stat_sum(wb, WB_RECLAIMABLE);
|
|
else
|
|
dtc->wb_dirty = wb_stat(wb, WB_RECLAIMABLE);
|
|
}
|
|
|
|
static bool domain_over_bg_thresh(struct dirty_throttle_control *dtc)
|
|
{
|
|
domain_dirty_avail(dtc, false);
|
|
domain_dirty_limits(dtc);
|
|
if (dtc->dirty > dtc->bg_thresh)
|
|
return true;
|
|
|
|
wb_bg_dirty_limits(dtc);
|
|
if (dtc->wb_dirty > dtc->wb_bg_thresh)
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
/**
|
|
* 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.
|
|
*
|
|
* Return: %true if writeback should continue.
|
|
*/
|
|
bool wb_over_bg_thresh(struct bdi_writeback *wb)
|
|
{
|
|
struct dirty_throttle_control gdtc = { GDTC_INIT(wb) };
|
|
struct dirty_throttle_control mdtc = { MDTC_INIT(wb, &gdtc) };
|
|
|
|
if (domain_over_bg_thresh(&gdtc))
|
|
return true;
|
|
|
|
if (mdtc_valid(&mdtc))
|
|
return domain_over_bg_thresh(&mdtc);
|
|
|
|
return false;
|
|
}
|
|
|
|
#ifdef CONFIG_SYSCTL
|
|
/*
|
|
* sysctl handler for /proc/sys/vm/dirty_writeback_centisecs
|
|
*/
|
|
static int dirty_writeback_centisecs_handler(const struct ctl_table *table, int write,
|
|
void *buffer, size_t *length, loff_t *ppos)
|
|
{
|
|
unsigned int old_interval = dirty_writeback_interval;
|
|
int ret;
|
|
|
|
ret = proc_dointvec(table, write, buffer, length, ppos);
|
|
|
|
/*
|
|
* Writing 0 to dirty_writeback_interval will disable periodic writeback
|
|
* and a different non-zero value will wakeup the writeback threads.
|
|
* wb_wakeup_delayed() would be more appropriate, but it's a pain to
|
|
* iterate over all bdis and wbs.
|
|
* The reason we do this is to make the change take effect immediately.
|
|
*/
|
|
if (!ret && write && dirty_writeback_interval &&
|
|
dirty_writeback_interval != old_interval)
|
|
wakeup_flusher_threads(WB_REASON_PERIODIC);
|
|
|
|
return ret;
|
|
}
|
|
#endif
|
|
|
|
void laptop_mode_timer_fn(struct timer_list *t)
|
|
{
|
|
struct backing_dev_info *backing_dev_info =
|
|
from_timer(backing_dev_info, t, laptop_mode_wb_timer);
|
|
|
|
wakeup_flusher_threads_bdi(backing_dev_info, WB_REASON_LAPTOP_TIMER);
|
|
}
|
|
|
|
/*
|
|
* 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();
|
|
}
|
|
|
|
/*
|
|
* 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.
|
|
*
|
|
* 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;
|
|
}
|
|
|
|
#ifdef CONFIG_SYSCTL
|
|
|
|
/* this is needed for the proc_doulongvec_minmax of vm_dirty_bytes */
|
|
static const unsigned long dirty_bytes_min = 2 * PAGE_SIZE;
|
|
|
|
static struct ctl_table vm_page_writeback_sysctls[] = {
|
|
{
|
|
.procname = "dirty_background_ratio",
|
|
.data = &dirty_background_ratio,
|
|
.maxlen = sizeof(dirty_background_ratio),
|
|
.mode = 0644,
|
|
.proc_handler = dirty_background_ratio_handler,
|
|
.extra1 = SYSCTL_ZERO,
|
|
.extra2 = SYSCTL_ONE_HUNDRED,
|
|
},
|
|
{
|
|
.procname = "dirty_background_bytes",
|
|
.data = &dirty_background_bytes,
|
|
.maxlen = sizeof(dirty_background_bytes),
|
|
.mode = 0644,
|
|
.proc_handler = dirty_background_bytes_handler,
|
|
.extra1 = SYSCTL_LONG_ONE,
|
|
},
|
|
{
|
|
.procname = "dirty_ratio",
|
|
.data = &vm_dirty_ratio,
|
|
.maxlen = sizeof(vm_dirty_ratio),
|
|
.mode = 0644,
|
|
.proc_handler = dirty_ratio_handler,
|
|
.extra1 = SYSCTL_ZERO,
|
|
.extra2 = SYSCTL_ONE_HUNDRED,
|
|
},
|
|
{
|
|
.procname = "dirty_bytes",
|
|
.data = &vm_dirty_bytes,
|
|
.maxlen = sizeof(vm_dirty_bytes),
|
|
.mode = 0644,
|
|
.proc_handler = dirty_bytes_handler,
|
|
.extra1 = (void *)&dirty_bytes_min,
|
|
},
|
|
{
|
|
.procname = "dirty_writeback_centisecs",
|
|
.data = &dirty_writeback_interval,
|
|
.maxlen = sizeof(dirty_writeback_interval),
|
|
.mode = 0644,
|
|
.proc_handler = dirty_writeback_centisecs_handler,
|
|
},
|
|
{
|
|
.procname = "dirty_expire_centisecs",
|
|
.data = &dirty_expire_interval,
|
|
.maxlen = sizeof(dirty_expire_interval),
|
|
.mode = 0644,
|
|
.proc_handler = proc_dointvec_minmax,
|
|
.extra1 = SYSCTL_ZERO,
|
|
},
|
|
#ifdef CONFIG_HIGHMEM
|
|
{
|
|
.procname = "highmem_is_dirtyable",
|
|
.data = &vm_highmem_is_dirtyable,
|
|
.maxlen = sizeof(vm_highmem_is_dirtyable),
|
|
.mode = 0644,
|
|
.proc_handler = proc_dointvec_minmax,
|
|
.extra1 = SYSCTL_ZERO,
|
|
.extra2 = SYSCTL_ONE,
|
|
},
|
|
#endif
|
|
{
|
|
.procname = "laptop_mode",
|
|
.data = &laptop_mode,
|
|
.maxlen = sizeof(laptop_mode),
|
|
.mode = 0644,
|
|
.proc_handler = proc_dointvec_jiffies,
|
|
},
|
|
};
|
|
#endif
|
|
|
|
/*
|
|
* 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.
|
|
*
|
|
* 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, 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);
|
|
#ifdef CONFIG_SYSCTL
|
|
register_sysctl_init("vm", vm_page_writeback_sysctls);
|
|
#endif
|
|
}
|
|
|
|
/**
|
|
* tag_pages_for_writeback - tag pages to be written by writeback
|
|
* @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 caller
|
|
* can then use the TOWRITE tag to identify pages eligible for writeback.
|
|
* This mechanism is used to avoid livelocking of writeback by a process
|
|
* steadily creating new dirty pages in the file (thus it is important for this
|
|
* function to be quick so that it can tag pages faster than a dirtying process
|
|
* can create them).
|
|
*/
|
|
void tag_pages_for_writeback(struct address_space *mapping,
|
|
pgoff_t start, pgoff_t end)
|
|
{
|
|
XA_STATE(xas, &mapping->i_pages, start);
|
|
unsigned int tagged = 0;
|
|
void *page;
|
|
|
|
xas_lock_irq(&xas);
|
|
xas_for_each_marked(&xas, page, end, PAGECACHE_TAG_DIRTY) {
|
|
xas_set_mark(&xas, PAGECACHE_TAG_TOWRITE);
|
|
if (++tagged % XA_CHECK_SCHED)
|
|
continue;
|
|
|
|
xas_pause(&xas);
|
|
xas_unlock_irq(&xas);
|
|
cond_resched();
|
|
xas_lock_irq(&xas);
|
|
}
|
|
xas_unlock_irq(&xas);
|
|
}
|
|
EXPORT_SYMBOL(tag_pages_for_writeback);
|
|
|
|
static bool folio_prepare_writeback(struct address_space *mapping,
|
|
struct writeback_control *wbc, struct folio *folio)
|
|
{
|
|
/*
|
|
* Folio truncated or invalidated. We can freely skip it then,
|
|
* even for data integrity operations: the folio has disappeared
|
|
* concurrently, so there could be no real expectation of this
|
|
* data integrity operation even if there is now a new, dirty
|
|
* folio at the same pagecache index.
|
|
*/
|
|
if (unlikely(folio->mapping != mapping))
|
|
return false;
|
|
|
|
/*
|
|
* Did somebody else write it for us?
|
|
*/
|
|
if (!folio_test_dirty(folio))
|
|
return false;
|
|
|
|
if (folio_test_writeback(folio)) {
|
|
if (wbc->sync_mode == WB_SYNC_NONE)
|
|
return false;
|
|
folio_wait_writeback(folio);
|
|
}
|
|
BUG_ON(folio_test_writeback(folio));
|
|
|
|
if (!folio_clear_dirty_for_io(folio))
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
static xa_mark_t wbc_to_tag(struct writeback_control *wbc)
|
|
{
|
|
if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
|
|
return PAGECACHE_TAG_TOWRITE;
|
|
return PAGECACHE_TAG_DIRTY;
|
|
}
|
|
|
|
static pgoff_t wbc_end(struct writeback_control *wbc)
|
|
{
|
|
if (wbc->range_cyclic)
|
|
return -1;
|
|
return wbc->range_end >> PAGE_SHIFT;
|
|
}
|
|
|
|
static struct folio *writeback_get_folio(struct address_space *mapping,
|
|
struct writeback_control *wbc)
|
|
{
|
|
struct folio *folio;
|
|
|
|
retry:
|
|
folio = folio_batch_next(&wbc->fbatch);
|
|
if (!folio) {
|
|
folio_batch_release(&wbc->fbatch);
|
|
cond_resched();
|
|
filemap_get_folios_tag(mapping, &wbc->index, wbc_end(wbc),
|
|
wbc_to_tag(wbc), &wbc->fbatch);
|
|
folio = folio_batch_next(&wbc->fbatch);
|
|
if (!folio)
|
|
return NULL;
|
|
}
|
|
|
|
folio_lock(folio);
|
|
if (unlikely(!folio_prepare_writeback(mapping, wbc, folio))) {
|
|
folio_unlock(folio);
|
|
goto retry;
|
|
}
|
|
|
|
trace_wbc_writepage(wbc, inode_to_bdi(mapping->host));
|
|
return folio;
|
|
}
|
|
|
|
/**
|
|
* writeback_iter - iterate folio of a mapping for writeback
|
|
* @mapping: address space structure to write
|
|
* @wbc: writeback context
|
|
* @folio: previously iterated folio (%NULL to start)
|
|
* @error: in-out pointer for writeback errors (see below)
|
|
*
|
|
* This function returns the next folio for the writeback operation described by
|
|
* @wbc on @mapping and should be called in a while loop in the ->writepages
|
|
* implementation.
|
|
*
|
|
* To start the writeback operation, %NULL is passed in the @folio argument, and
|
|
* for every subsequent iteration the folio returned previously should be passed
|
|
* back in.
|
|
*
|
|
* If there was an error in the per-folio writeback inside the writeback_iter()
|
|
* loop, @error should be set to the error value.
|
|
*
|
|
* Once the writeback described in @wbc has finished, this function will return
|
|
* %NULL and if there was an error in any iteration restore it to @error.
|
|
*
|
|
* Note: callers should not manually break out of the loop using break or goto
|
|
* but must keep calling writeback_iter() until it returns %NULL.
|
|
*
|
|
* Return: the folio to write or %NULL if the loop is done.
|
|
*/
|
|
struct folio *writeback_iter(struct address_space *mapping,
|
|
struct writeback_control *wbc, struct folio *folio, int *error)
|
|
{
|
|
if (!folio) {
|
|
folio_batch_init(&wbc->fbatch);
|
|
wbc->saved_err = *error = 0;
|
|
|
|
/*
|
|
* For range cyclic writeback we remember where we stopped so
|
|
* that we can continue where we stopped.
|
|
*
|
|
* For non-cyclic writeback we always start at the beginning of
|
|
* the passed in range.
|
|
*/
|
|
if (wbc->range_cyclic)
|
|
wbc->index = mapping->writeback_index;
|
|
else
|
|
wbc->index = wbc->range_start >> PAGE_SHIFT;
|
|
|
|
/*
|
|
* To avoid livelocks when other processes dirty new pages, we
|
|
* first tag pages which should be written back and only then
|
|
* start writing them.
|
|
*
|
|
* For data-integrity writeback we have to be careful so that we
|
|
* do not miss some pages (e.g., because some other process has
|
|
* cleared the 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 I/O).
|
|
*/
|
|
if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
|
|
tag_pages_for_writeback(mapping, wbc->index,
|
|
wbc_end(wbc));
|
|
} else {
|
|
wbc->nr_to_write -= folio_nr_pages(folio);
|
|
|
|
WARN_ON_ONCE(*error > 0);
|
|
|
|
/*
|
|
* For integrity writeback we have to keep going until we have
|
|
* written all the folios we tagged for writeback above, even if
|
|
* we run past wbc->nr_to_write or encounter errors.
|
|
* We stash away the first error we encounter in wbc->saved_err
|
|
* so that it can be retrieved when we're done. This is because
|
|
* the file system may still have state to clear for each folio.
|
|
*
|
|
* For background writeback we exit as soon as we run past
|
|
* wbc->nr_to_write or encounter the first error.
|
|
*/
|
|
if (wbc->sync_mode == WB_SYNC_ALL) {
|
|
if (*error && !wbc->saved_err)
|
|
wbc->saved_err = *error;
|
|
} else {
|
|
if (*error || wbc->nr_to_write <= 0)
|
|
goto done;
|
|
}
|
|
}
|
|
|
|
folio = writeback_get_folio(mapping, wbc);
|
|
if (!folio) {
|
|
/*
|
|
* To avoid deadlocks between range_cyclic writeback and callers
|
|
* that hold pages in PageWriteback to aggregate I/O until
|
|
* the writeback iteration finishes, we do not loop back to the
|
|
* start of the file. Doing so causes a page lock/page
|
|
* writeback access order inversion - we should only ever lock
|
|
* multiple pages in ascending page->index order, and looping
|
|
* back to the start of the file violates that rule and causes
|
|
* deadlocks.
|
|
*/
|
|
if (wbc->range_cyclic)
|
|
mapping->writeback_index = 0;
|
|
|
|
/*
|
|
* Return the first error we encountered (if there was any) to
|
|
* the caller.
|
|
*/
|
|
*error = wbc->saved_err;
|
|
}
|
|
return folio;
|
|
|
|
done:
|
|
if (wbc->range_cyclic)
|
|
mapping->writeback_index = folio_next_index(folio);
|
|
folio_batch_release(&wbc->fbatch);
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(writeback_iter);
|
|
|
|
/**
|
|
* 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
|
|
*
|
|
* Return: %0 on success, negative error code otherwise
|
|
*
|
|
* Note: please use writeback_iter() instead.
|
|
*/
|
|
int write_cache_pages(struct address_space *mapping,
|
|
struct writeback_control *wbc, writepage_t writepage,
|
|
void *data)
|
|
{
|
|
struct folio *folio = NULL;
|
|
int error;
|
|
|
|
while ((folio = writeback_iter(mapping, wbc, folio, &error))) {
|
|
error = writepage(folio, wbc, data);
|
|
if (error == AOP_WRITEPAGE_ACTIVATE) {
|
|
folio_unlock(folio);
|
|
error = 0;
|
|
}
|
|
}
|
|
|
|
return error;
|
|
}
|
|
EXPORT_SYMBOL(write_cache_pages);
|
|
|
|
static int writeback_use_writepage(struct address_space *mapping,
|
|
struct writeback_control *wbc)
|
|
{
|
|
struct folio *folio = NULL;
|
|
struct blk_plug plug;
|
|
int err;
|
|
|
|
blk_start_plug(&plug);
|
|
while ((folio = writeback_iter(mapping, wbc, folio, &err))) {
|
|
err = mapping->a_ops->writepage(&folio->page, wbc);
|
|
if (err == AOP_WRITEPAGE_ACTIVATE) {
|
|
folio_unlock(folio);
|
|
err = 0;
|
|
}
|
|
mapping_set_error(mapping, err);
|
|
}
|
|
blk_finish_plug(&plug);
|
|
|
|
return err;
|
|
}
|
|
|
|
int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
|
|
{
|
|
int ret;
|
|
struct bdi_writeback *wb;
|
|
|
|
if (wbc->nr_to_write <= 0)
|
|
return 0;
|
|
wb = inode_to_wb_wbc(mapping->host, wbc);
|
|
wb_bandwidth_estimate_start(wb);
|
|
while (1) {
|
|
if (mapping->a_ops->writepages) {
|
|
ret = mapping->a_ops->writepages(mapping, wbc);
|
|
} else if (mapping->a_ops->writepage) {
|
|
ret = writeback_use_writepage(mapping, wbc);
|
|
} else {
|
|
/* deal with chardevs and other special files */
|
|
ret = 0;
|
|
}
|
|
if (ret != -ENOMEM || wbc->sync_mode != WB_SYNC_ALL)
|
|
break;
|
|
|
|
/*
|
|
* Lacking an allocation context or the locality or writeback
|
|
* state of any of the inode's pages, throttle based on
|
|
* writeback activity on the local node. It's as good a
|
|
* guess as any.
|
|
*/
|
|
reclaim_throttle(NODE_DATA(numa_node_id()),
|
|
VMSCAN_THROTTLE_WRITEBACK);
|
|
}
|
|
/*
|
|
* Usually few pages are written by now from those we've just submitted
|
|
* but if there's constant writeback being submitted, this makes sure
|
|
* writeback bandwidth is updated once in a while.
|
|
*/
|
|
if (time_is_before_jiffies(READ_ONCE(wb->bw_time_stamp) +
|
|
BANDWIDTH_INTERVAL))
|
|
wb_update_bandwidth(wb);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* For address_spaces which do not use buffers nor write back.
|
|
*/
|
|
bool noop_dirty_folio(struct address_space *mapping, struct folio *folio)
|
|
{
|
|
if (!folio_test_dirty(folio))
|
|
return !folio_test_set_dirty(folio);
|
|
return false;
|
|
}
|
|
EXPORT_SYMBOL(noop_dirty_folio);
|
|
|
|
/*
|
|
* Helper function for set_page_dirty family.
|
|
*
|
|
* NOTE: This relies on being atomic wrt interrupts.
|
|
*/
|
|
static void folio_account_dirtied(struct folio *folio,
|
|
struct address_space *mapping)
|
|
{
|
|
struct inode *inode = mapping->host;
|
|
|
|
trace_writeback_dirty_folio(folio, mapping);
|
|
|
|
if (mapping_can_writeback(mapping)) {
|
|
struct bdi_writeback *wb;
|
|
long nr = folio_nr_pages(folio);
|
|
|
|
inode_attach_wb(inode, folio);
|
|
wb = inode_to_wb(inode);
|
|
|
|
__lruvec_stat_mod_folio(folio, NR_FILE_DIRTY, nr);
|
|
__zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, nr);
|
|
__node_stat_mod_folio(folio, NR_DIRTIED, nr);
|
|
wb_stat_mod(wb, WB_RECLAIMABLE, nr);
|
|
wb_stat_mod(wb, WB_DIRTIED, nr);
|
|
task_io_account_write(nr * PAGE_SIZE);
|
|
current->nr_dirtied += nr;
|
|
__this_cpu_add(bdp_ratelimits, nr);
|
|
|
|
mem_cgroup_track_foreign_dirty(folio, wb);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Helper function for deaccounting dirty page without writeback.
|
|
*
|
|
*/
|
|
void folio_account_cleaned(struct folio *folio, struct bdi_writeback *wb)
|
|
{
|
|
long nr = folio_nr_pages(folio);
|
|
|
|
lruvec_stat_mod_folio(folio, NR_FILE_DIRTY, -nr);
|
|
zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr);
|
|
wb_stat_mod(wb, WB_RECLAIMABLE, -nr);
|
|
task_io_account_cancelled_write(nr * PAGE_SIZE);
|
|
}
|
|
|
|
/*
|
|
* Mark the folio dirty, and set it dirty in the page cache.
|
|
*
|
|
* If warn is true, then emit a warning if the folio is not uptodate and has
|
|
* not been truncated.
|
|
*
|
|
* It is the caller's responsibility to prevent the folio from being truncated
|
|
* while this function is in progress, although it may have been truncated
|
|
* before this function is called. Most callers have the folio locked.
|
|
* A few have the folio blocked from truncation through other means (e.g.
|
|
* zap_vma_pages() has it mapped and is holding the page table lock).
|
|
* When called from mark_buffer_dirty(), the filesystem should hold a
|
|
* reference to the buffer_head that is being marked dirty, which causes
|
|
* try_to_free_buffers() to fail.
|
|
*/
|
|
void __folio_mark_dirty(struct folio *folio, struct address_space *mapping,
|
|
int warn)
|
|
{
|
|
unsigned long flags;
|
|
|
|
xa_lock_irqsave(&mapping->i_pages, flags);
|
|
if (folio->mapping) { /* Race with truncate? */
|
|
WARN_ON_ONCE(warn && !folio_test_uptodate(folio));
|
|
folio_account_dirtied(folio, mapping);
|
|
__xa_set_mark(&mapping->i_pages, folio_index(folio),
|
|
PAGECACHE_TAG_DIRTY);
|
|
}
|
|
xa_unlock_irqrestore(&mapping->i_pages, flags);
|
|
}
|
|
|
|
/**
|
|
* filemap_dirty_folio - Mark a folio dirty for filesystems which do not use buffer_heads.
|
|
* @mapping: Address space this folio belongs to.
|
|
* @folio: Folio to be marked as dirty.
|
|
*
|
|
* Filesystems which do not use buffer heads should call this function
|
|
* from their dirty_folio address space operation. It ignores the
|
|
* contents of folio_get_private(), so if the filesystem marks individual
|
|
* blocks as dirty, the filesystem should handle that itself.
|
|
*
|
|
* This is also sometimes used by filesystems which use buffer_heads when
|
|
* a single buffer is being dirtied: we want to set the folio dirty in
|
|
* that case, but not all the buffers. This is a "bottom-up" dirtying,
|
|
* whereas block_dirty_folio() is a "top-down" dirtying.
|
|
*
|
|
* The caller must ensure this doesn't race with truncation. Most will
|
|
* simply hold the folio lock, but e.g. zap_pte_range() calls with the
|
|
* folio mapped and the pte lock held, which also locks out truncation.
|
|
*/
|
|
bool filemap_dirty_folio(struct address_space *mapping, struct folio *folio)
|
|
{
|
|
if (folio_test_set_dirty(folio))
|
|
return false;
|
|
|
|
__folio_mark_dirty(folio, mapping, !folio_test_private(folio));
|
|
|
|
if (mapping->host) {
|
|
/* !PageAnon && !swapper_space */
|
|
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
|
|
}
|
|
return true;
|
|
}
|
|
EXPORT_SYMBOL(filemap_dirty_folio);
|
|
|
|
/**
|
|
* folio_redirty_for_writepage - Decline to write a dirty folio.
|
|
* @wbc: The writeback control.
|
|
* @folio: The folio.
|
|
*
|
|
* When a writepage implementation decides that it doesn't want to write
|
|
* @folio for some reason, it should call this function, unlock @folio and
|
|
* return 0.
|
|
*
|
|
* Return: True if we redirtied the folio. False if someone else dirtied
|
|
* it first.
|
|
*/
|
|
bool folio_redirty_for_writepage(struct writeback_control *wbc,
|
|
struct folio *folio)
|
|
{
|
|
struct address_space *mapping = folio->mapping;
|
|
long nr = folio_nr_pages(folio);
|
|
bool ret;
|
|
|
|
wbc->pages_skipped += nr;
|
|
ret = filemap_dirty_folio(mapping, folio);
|
|
if (mapping && mapping_can_writeback(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 -= nr;
|
|
node_stat_mod_folio(folio, NR_DIRTIED, -nr);
|
|
wb_stat_mod(wb, WB_DIRTIED, -nr);
|
|
unlocked_inode_to_wb_end(inode, &cookie);
|
|
}
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(folio_redirty_for_writepage);
|
|
|
|
/**
|
|
* folio_mark_dirty - Mark a folio as being modified.
|
|
* @folio: The folio.
|
|
*
|
|
* The folio may not be truncated while this function is running.
|
|
* Holding the folio lock is sufficient to prevent truncation, but some
|
|
* callers cannot acquire a sleeping lock. These callers instead hold
|
|
* the page table lock for a page table which contains at least one page
|
|
* in this folio. Truncation will block on the page table lock as it
|
|
* unmaps pages before removing the folio from its mapping.
|
|
*
|
|
* Return: True if the folio was newly dirtied, false if it was already dirty.
|
|
*/
|
|
bool folio_mark_dirty(struct folio *folio)
|
|
{
|
|
struct address_space *mapping = folio_mapping(folio);
|
|
|
|
if (likely(mapping)) {
|
|
/*
|
|
* readahead/folio_deactivate could remain
|
|
* PG_readahead/PG_reclaim due to race with folio_end_writeback
|
|
* About readahead, if the folio is written, the flags would be
|
|
* reset. So no problem.
|
|
* About folio_deactivate, if the folio is redirtied,
|
|
* the flag will be reset. So no problem. but if the
|
|
* folio is used by readahead it will confuse readahead
|
|
* and make it restart the size rampup process. But it's
|
|
* a trivial problem.
|
|
*/
|
|
if (folio_test_reclaim(folio))
|
|
folio_clear_reclaim(folio);
|
|
return mapping->a_ops->dirty_folio(mapping, folio);
|
|
}
|
|
|
|
return noop_dirty_folio(mapping, folio);
|
|
}
|
|
EXPORT_SYMBOL(folio_mark_dirty);
|
|
|
|
/*
|
|
* folio_mark_dirty() is racy if the caller has no reference against
|
|
* folio->mapping->host, and if the folio is unlocked. This is because another
|
|
* CPU could truncate the folio off the mapping and then free the mapping.
|
|
*
|
|
* Usually, the folio _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 folio should be locked before running folio_mark_dirty().
|
|
*/
|
|
bool folio_mark_dirty_lock(struct folio *folio)
|
|
{
|
|
bool ret;
|
|
|
|
folio_lock(folio);
|
|
ret = folio_mark_dirty(folio);
|
|
folio_unlock(folio);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(folio_mark_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 __folio_cancel_dirty(struct folio *folio)
|
|
{
|
|
struct address_space *mapping = folio_mapping(folio);
|
|
|
|
if (mapping_can_writeback(mapping)) {
|
|
struct inode *inode = mapping->host;
|
|
struct bdi_writeback *wb;
|
|
struct wb_lock_cookie cookie = {};
|
|
|
|
wb = unlocked_inode_to_wb_begin(inode, &cookie);
|
|
|
|
if (folio_test_clear_dirty(folio))
|
|
folio_account_cleaned(folio, wb);
|
|
|
|
unlocked_inode_to_wb_end(inode, &cookie);
|
|
} else {
|
|
folio_clear_dirty(folio);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(__folio_cancel_dirty);
|
|
|
|
/*
|
|
* Clear a folio's dirty flag, while caring for dirty memory accounting.
|
|
* Returns true if the folio was previously dirty.
|
|
*
|
|
* This is for preparing to put the folio under writeout. We leave
|
|
* the folio tagged as dirty in the xarray so that a concurrent
|
|
* write-for-sync can discover it via a PAGECACHE_TAG_DIRTY walk.
|
|
* The ->writepage implementation will run either folio_start_writeback()
|
|
* or folio_mark_dirty(), at which stage we bring the folio's dirty flag
|
|
* and xarray dirty tag back into sync.
|
|
*
|
|
* This incoherency between the folio's dirty flag and xarray tag is
|
|
* unfortunate, but it only exists while the folio is locked.
|
|
*/
|
|
bool folio_clear_dirty_for_io(struct folio *folio)
|
|
{
|
|
struct address_space *mapping = folio_mapping(folio);
|
|
bool ret = false;
|
|
|
|
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
|
|
|
|
if (mapping && mapping_can_writeback(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 folio dirty if it was
|
|
* dirty in a pagetable. Only to then
|
|
* (c) clean the folio 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 "folio_mark_dirty(folio)"
|
|
* 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 folio "master dirty bit"
|
|
* as a serialization point for all the different
|
|
* threads doing their things.
|
|
*/
|
|
if (folio_mkclean(folio))
|
|
folio_mark_dirty(folio);
|
|
/*
|
|
* We carefully synchronise fault handlers against
|
|
* installing a dirty pte and marking the folio dirty
|
|
* at this point. We do this by having them hold the
|
|
* page lock while dirtying the folio, and folios are
|
|
* always locked coming in here, so we get the desired
|
|
* exclusion.
|
|
*/
|
|
wb = unlocked_inode_to_wb_begin(inode, &cookie);
|
|
if (folio_test_clear_dirty(folio)) {
|
|
long nr = folio_nr_pages(folio);
|
|
lruvec_stat_mod_folio(folio, NR_FILE_DIRTY, -nr);
|
|
zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr);
|
|
wb_stat_mod(wb, WB_RECLAIMABLE, -nr);
|
|
ret = true;
|
|
}
|
|
unlocked_inode_to_wb_end(inode, &cookie);
|
|
return ret;
|
|
}
|
|
return folio_test_clear_dirty(folio);
|
|
}
|
|
EXPORT_SYMBOL(folio_clear_dirty_for_io);
|
|
|
|
static void wb_inode_writeback_start(struct bdi_writeback *wb)
|
|
{
|
|
atomic_inc(&wb->writeback_inodes);
|
|
}
|
|
|
|
static void wb_inode_writeback_end(struct bdi_writeback *wb)
|
|
{
|
|
unsigned long flags;
|
|
atomic_dec(&wb->writeback_inodes);
|
|
/*
|
|
* Make sure estimate of writeback throughput gets updated after
|
|
* writeback completed. We delay the update by BANDWIDTH_INTERVAL
|
|
* (which is the interval other bandwidth updates use for batching) so
|
|
* that if multiple inodes end writeback at a similar time, they get
|
|
* batched into one bandwidth update.
|
|
*/
|
|
spin_lock_irqsave(&wb->work_lock, flags);
|
|
if (test_bit(WB_registered, &wb->state))
|
|
queue_delayed_work(bdi_wq, &wb->bw_dwork, BANDWIDTH_INTERVAL);
|
|
spin_unlock_irqrestore(&wb->work_lock, flags);
|
|
}
|
|
|
|
bool __folio_end_writeback(struct folio *folio)
|
|
{
|
|
long nr = folio_nr_pages(folio);
|
|
struct address_space *mapping = folio_mapping(folio);
|
|
bool ret;
|
|
|
|
if (mapping && mapping_use_writeback_tags(mapping)) {
|
|
struct inode *inode = mapping->host;
|
|
struct backing_dev_info *bdi = inode_to_bdi(inode);
|
|
unsigned long flags;
|
|
|
|
xa_lock_irqsave(&mapping->i_pages, flags);
|
|
ret = folio_xor_flags_has_waiters(folio, 1 << PG_writeback);
|
|
__xa_clear_mark(&mapping->i_pages, folio_index(folio),
|
|
PAGECACHE_TAG_WRITEBACK);
|
|
if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT) {
|
|
struct bdi_writeback *wb = inode_to_wb(inode);
|
|
|
|
wb_stat_mod(wb, WB_WRITEBACK, -nr);
|
|
__wb_writeout_add(wb, nr);
|
|
if (!mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK))
|
|
wb_inode_writeback_end(wb);
|
|
}
|
|
|
|
if (mapping->host && !mapping_tagged(mapping,
|
|
PAGECACHE_TAG_WRITEBACK))
|
|
sb_clear_inode_writeback(mapping->host);
|
|
|
|
xa_unlock_irqrestore(&mapping->i_pages, flags);
|
|
} else {
|
|
ret = folio_xor_flags_has_waiters(folio, 1 << PG_writeback);
|
|
}
|
|
|
|
lruvec_stat_mod_folio(folio, NR_WRITEBACK, -nr);
|
|
zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr);
|
|
node_stat_mod_folio(folio, NR_WRITTEN, nr);
|
|
|
|
return ret;
|
|
}
|
|
|
|
void __folio_start_writeback(struct folio *folio, bool keep_write)
|
|
{
|
|
long nr = folio_nr_pages(folio);
|
|
struct address_space *mapping = folio_mapping(folio);
|
|
int access_ret;
|
|
|
|
VM_BUG_ON_FOLIO(folio_test_writeback(folio), folio);
|
|
|
|
if (mapping && mapping_use_writeback_tags(mapping)) {
|
|
XA_STATE(xas, &mapping->i_pages, folio_index(folio));
|
|
struct inode *inode = mapping->host;
|
|
struct backing_dev_info *bdi = inode_to_bdi(inode);
|
|
unsigned long flags;
|
|
bool on_wblist;
|
|
|
|
xas_lock_irqsave(&xas, flags);
|
|
xas_load(&xas);
|
|
folio_test_set_writeback(folio);
|
|
|
|
on_wblist = mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK);
|
|
|
|
xas_set_mark(&xas, PAGECACHE_TAG_WRITEBACK);
|
|
if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT) {
|
|
struct bdi_writeback *wb = inode_to_wb(inode);
|
|
|
|
wb_stat_mod(wb, WB_WRITEBACK, nr);
|
|
if (!on_wblist)
|
|
wb_inode_writeback_start(wb);
|
|
}
|
|
|
|
/*
|
|
* We can come through here when swapping anonymous
|
|
* folios, so we don't necessarily have an inode to
|
|
* track for sync.
|
|
*/
|
|
if (mapping->host && !on_wblist)
|
|
sb_mark_inode_writeback(mapping->host);
|
|
if (!folio_test_dirty(folio))
|
|
xas_clear_mark(&xas, PAGECACHE_TAG_DIRTY);
|
|
if (!keep_write)
|
|
xas_clear_mark(&xas, PAGECACHE_TAG_TOWRITE);
|
|
xas_unlock_irqrestore(&xas, flags);
|
|
} else {
|
|
folio_test_set_writeback(folio);
|
|
}
|
|
|
|
lruvec_stat_mod_folio(folio, NR_WRITEBACK, nr);
|
|
zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, nr);
|
|
|
|
access_ret = arch_make_folio_accessible(folio);
|
|
/*
|
|
* If writeback has been triggered on a page that cannot be made
|
|
* accessible, it is too late to recover here.
|
|
*/
|
|
VM_BUG_ON_FOLIO(access_ret != 0, folio);
|
|
}
|
|
EXPORT_SYMBOL(__folio_start_writeback);
|
|
|
|
/**
|
|
* folio_wait_writeback - Wait for a folio to finish writeback.
|
|
* @folio: The folio to wait for.
|
|
*
|
|
* If the folio is currently being written back to storage, wait for the
|
|
* I/O to complete.
|
|
*
|
|
* Context: Sleeps. Must be called in process context and with
|
|
* no spinlocks held. Caller should hold a reference on the folio.
|
|
* If the folio is not locked, writeback may start again after writeback
|
|
* has finished.
|
|
*/
|
|
void folio_wait_writeback(struct folio *folio)
|
|
{
|
|
while (folio_test_writeback(folio)) {
|
|
trace_folio_wait_writeback(folio, folio_mapping(folio));
|
|
folio_wait_bit(folio, PG_writeback);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL_GPL(folio_wait_writeback);
|
|
|
|
/**
|
|
* folio_wait_writeback_killable - Wait for a folio to finish writeback.
|
|
* @folio: The folio to wait for.
|
|
*
|
|
* If the folio is currently being written back to storage, wait for the
|
|
* I/O to complete or a fatal signal to arrive.
|
|
*
|
|
* Context: Sleeps. Must be called in process context and with
|
|
* no spinlocks held. Caller should hold a reference on the folio.
|
|
* If the folio is not locked, writeback may start again after writeback
|
|
* has finished.
|
|
* Return: 0 on success, -EINTR if we get a fatal signal while waiting.
|
|
*/
|
|
int folio_wait_writeback_killable(struct folio *folio)
|
|
{
|
|
while (folio_test_writeback(folio)) {
|
|
trace_folio_wait_writeback(folio, folio_mapping(folio));
|
|
if (folio_wait_bit_killable(folio, PG_writeback))
|
|
return -EINTR;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(folio_wait_writeback_killable);
|
|
|
|
/**
|
|
* folio_wait_stable() - wait for writeback to finish, if necessary.
|
|
* @folio: The folio to wait on.
|
|
*
|
|
* This function determines if the given folio is related to a backing
|
|
* device that requires folio contents to be held stable during writeback.
|
|
* If so, then it will wait for any pending writeback to complete.
|
|
*
|
|
* Context: Sleeps. Must be called in process context and with
|
|
* no spinlocks held. Caller should hold a reference on the folio.
|
|
* If the folio is not locked, writeback may start again after writeback
|
|
* has finished.
|
|
*/
|
|
void folio_wait_stable(struct folio *folio)
|
|
{
|
|
if (mapping_stable_writes(folio_mapping(folio)))
|
|
folio_wait_writeback(folio);
|
|
}
|
|
EXPORT_SYMBOL_GPL(folio_wait_stable);
|