forked from Minki/linux
0e175a1835
This creates a new 'reason' field in a wb_writeback_work structure, which unambiguously identifies who initiates writeback activity. A 'wb_reason' enumeration has been added to writeback.h, to enumerate the possible reasons. The 'writeback_work_class' and tracepoint event class and 'writeback_queue_io' tracepoints are updated to include the symbolic 'reason' in all trace events. And the 'writeback_inodes_sbXXX' family of routines has had a wb_stats parameter added to them, so callers can specify why writeback is being started. Acked-by: Jan Kara <jack@suse.cz> Signed-off-by: Curt Wohlgemuth <curtw@google.com> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
2007 lines
59 KiB
C
2007 lines
59 KiB
C
/*
|
|
* mm/page-writeback.c
|
|
*
|
|
* Copyright (C) 2002, Linus Torvalds.
|
|
* Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
|
|
*
|
|
* Contains functions related to writing back dirty pages at the
|
|
* address_space level.
|
|
*
|
|
* 10Apr2002 Andrew Morton
|
|
* Initial version
|
|
*/
|
|
|
|
#include <linux/kernel.h>
|
|
#include <linux/module.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/fs.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/swap.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/pagemap.h>
|
|
#include <linux/writeback.h>
|
|
#include <linux/init.h>
|
|
#include <linux/backing-dev.h>
|
|
#include <linux/task_io_accounting_ops.h>
|
|
#include <linux/blkdev.h>
|
|
#include <linux/mpage.h>
|
|
#include <linux/rmap.h>
|
|
#include <linux/percpu.h>
|
|
#include <linux/notifier.h>
|
|
#include <linux/smp.h>
|
|
#include <linux/sysctl.h>
|
|
#include <linux/cpu.h>
|
|
#include <linux/syscalls.h>
|
|
#include <linux/buffer_head.h>
|
|
#include <linux/pagevec.h>
|
|
#include <trace/events/writeback.h>
|
|
|
|
/*
|
|
* Sleep at most 200ms at a time in balance_dirty_pages().
|
|
*/
|
|
#define MAX_PAUSE max(HZ/5, 1)
|
|
|
|
/*
|
|
* Estimate write bandwidth at 200ms intervals.
|
|
*/
|
|
#define BANDWIDTH_INTERVAL max(HZ/5, 1)
|
|
|
|
#define RATELIMIT_CALC_SHIFT 10
|
|
|
|
/*
|
|
* After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited
|
|
* will look to see if it needs to force writeback or throttling.
|
|
*/
|
|
static long ratelimit_pages = 32;
|
|
|
|
/* The following parameters are exported via /proc/sys/vm */
|
|
|
|
/*
|
|
* Start background writeback (via writeback threads) at this percentage
|
|
*/
|
|
int dirty_background_ratio = 10;
|
|
|
|
/*
|
|
* dirty_background_bytes starts at 0 (disabled) so that it is a function of
|
|
* dirty_background_ratio * the amount of dirtyable memory
|
|
*/
|
|
unsigned long dirty_background_bytes;
|
|
|
|
/*
|
|
* free highmem will not be subtracted from the total free memory
|
|
* for calculating free ratios if vm_highmem_is_dirtyable is true
|
|
*/
|
|
int vm_highmem_is_dirtyable;
|
|
|
|
/*
|
|
* The generator of dirty data starts writeback at this percentage
|
|
*/
|
|
int vm_dirty_ratio = 20;
|
|
|
|
/*
|
|
* vm_dirty_bytes starts at 0 (disabled) so that it is a function of
|
|
* vm_dirty_ratio * the amount of dirtyable memory
|
|
*/
|
|
unsigned long vm_dirty_bytes;
|
|
|
|
/*
|
|
* The interval between `kupdate'-style writebacks
|
|
*/
|
|
unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */
|
|
|
|
/*
|
|
* The longest time for which data is allowed to remain dirty
|
|
*/
|
|
unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */
|
|
|
|
/*
|
|
* Flag that makes the machine dump writes/reads and block dirtyings.
|
|
*/
|
|
int block_dump;
|
|
|
|
/*
|
|
* Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies:
|
|
* a full sync is triggered after this time elapses without any disk activity.
|
|
*/
|
|
int laptop_mode;
|
|
|
|
EXPORT_SYMBOL(laptop_mode);
|
|
|
|
/* End of sysctl-exported parameters */
|
|
|
|
unsigned long global_dirty_limit;
|
|
|
|
/*
|
|
* Scale the writeback cache size proportional to the relative writeout speeds.
|
|
*
|
|
* We do this by keeping a floating proportion between BDIs, based on page
|
|
* writeback completions [end_page_writeback()]. Those devices that write out
|
|
* pages fastest will get the larger share, while the slower will get a smaller
|
|
* share.
|
|
*
|
|
* We use page writeout completions because we are interested in getting rid of
|
|
* dirty pages. Having them written out is the primary goal.
|
|
*
|
|
* We introduce a concept of time, a period over which we measure these events,
|
|
* because demand can/will vary over time. The length of this period itself is
|
|
* measured in page writeback completions.
|
|
*
|
|
*/
|
|
static struct prop_descriptor vm_completions;
|
|
static struct prop_descriptor vm_dirties;
|
|
|
|
/*
|
|
* couple the period to the dirty_ratio:
|
|
*
|
|
* period/2 ~ roundup_pow_of_two(dirty limit)
|
|
*/
|
|
static int calc_period_shift(void)
|
|
{
|
|
unsigned long dirty_total;
|
|
|
|
if (vm_dirty_bytes)
|
|
dirty_total = vm_dirty_bytes / PAGE_SIZE;
|
|
else
|
|
dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) /
|
|
100;
|
|
return 2 + ilog2(dirty_total - 1);
|
|
}
|
|
|
|
/*
|
|
* update the period when the dirty threshold changes.
|
|
*/
|
|
static void update_completion_period(void)
|
|
{
|
|
int shift = calc_period_shift();
|
|
prop_change_shift(&vm_completions, shift);
|
|
prop_change_shift(&vm_dirties, shift);
|
|
|
|
writeback_set_ratelimit();
|
|
}
|
|
|
|
int dirty_background_ratio_handler(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp,
|
|
loff_t *ppos)
|
|
{
|
|
int ret;
|
|
|
|
ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
|
|
if (ret == 0 && write)
|
|
dirty_background_bytes = 0;
|
|
return ret;
|
|
}
|
|
|
|
int dirty_background_bytes_handler(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp,
|
|
loff_t *ppos)
|
|
{
|
|
int ret;
|
|
|
|
ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
|
|
if (ret == 0 && write)
|
|
dirty_background_ratio = 0;
|
|
return ret;
|
|
}
|
|
|
|
int dirty_ratio_handler(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp,
|
|
loff_t *ppos)
|
|
{
|
|
int old_ratio = vm_dirty_ratio;
|
|
int ret;
|
|
|
|
ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
|
|
if (ret == 0 && write && vm_dirty_ratio != old_ratio) {
|
|
update_completion_period();
|
|
vm_dirty_bytes = 0;
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
|
|
int dirty_bytes_handler(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp,
|
|
loff_t *ppos)
|
|
{
|
|
unsigned long old_bytes = vm_dirty_bytes;
|
|
int ret;
|
|
|
|
ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
|
|
if (ret == 0 && write && vm_dirty_bytes != old_bytes) {
|
|
update_completion_period();
|
|
vm_dirty_ratio = 0;
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Increment the BDI's writeout completion count and the global writeout
|
|
* completion count. Called from test_clear_page_writeback().
|
|
*/
|
|
static inline void __bdi_writeout_inc(struct backing_dev_info *bdi)
|
|
{
|
|
__inc_bdi_stat(bdi, BDI_WRITTEN);
|
|
__prop_inc_percpu_max(&vm_completions, &bdi->completions,
|
|
bdi->max_prop_frac);
|
|
}
|
|
|
|
void bdi_writeout_inc(struct backing_dev_info *bdi)
|
|
{
|
|
unsigned long flags;
|
|
|
|
local_irq_save(flags);
|
|
__bdi_writeout_inc(bdi);
|
|
local_irq_restore(flags);
|
|
}
|
|
EXPORT_SYMBOL_GPL(bdi_writeout_inc);
|
|
|
|
void task_dirty_inc(struct task_struct *tsk)
|
|
{
|
|
prop_inc_single(&vm_dirties, &tsk->dirties);
|
|
}
|
|
|
|
/*
|
|
* Obtain an accurate fraction of the BDI's portion.
|
|
*/
|
|
static void bdi_writeout_fraction(struct backing_dev_info *bdi,
|
|
long *numerator, long *denominator)
|
|
{
|
|
prop_fraction_percpu(&vm_completions, &bdi->completions,
|
|
numerator, denominator);
|
|
}
|
|
|
|
/*
|
|
*
|
|
*/
|
|
static unsigned int bdi_min_ratio;
|
|
|
|
int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
|
|
{
|
|
int ret = 0;
|
|
|
|
spin_lock_bh(&bdi_lock);
|
|
if (min_ratio > bdi->max_ratio) {
|
|
ret = -EINVAL;
|
|
} else {
|
|
min_ratio -= bdi->min_ratio;
|
|
if (bdi_min_ratio + min_ratio < 100) {
|
|
bdi_min_ratio += min_ratio;
|
|
bdi->min_ratio += min_ratio;
|
|
} else {
|
|
ret = -EINVAL;
|
|
}
|
|
}
|
|
spin_unlock_bh(&bdi_lock);
|
|
|
|
return ret;
|
|
}
|
|
|
|
int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio)
|
|
{
|
|
int ret = 0;
|
|
|
|
if (max_ratio > 100)
|
|
return -EINVAL;
|
|
|
|
spin_lock_bh(&bdi_lock);
|
|
if (bdi->min_ratio > max_ratio) {
|
|
ret = -EINVAL;
|
|
} else {
|
|
bdi->max_ratio = max_ratio;
|
|
bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100;
|
|
}
|
|
spin_unlock_bh(&bdi_lock);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(bdi_set_max_ratio);
|
|
|
|
/*
|
|
* Work out the current dirty-memory clamping and background writeout
|
|
* thresholds.
|
|
*
|
|
* The main aim here is to lower them aggressively if there is a lot of mapped
|
|
* memory around. To avoid stressing page reclaim with lots of unreclaimable
|
|
* pages. It is better to clamp down on writers than to start swapping, and
|
|
* performing lots of scanning.
|
|
*
|
|
* We only allow 1/2 of the currently-unmapped memory to be dirtied.
|
|
*
|
|
* We don't permit the clamping level to fall below 5% - that is getting rather
|
|
* excessive.
|
|
*
|
|
* We make sure that the background writeout level is below the adjusted
|
|
* clamping level.
|
|
*/
|
|
|
|
static unsigned long highmem_dirtyable_memory(unsigned long total)
|
|
{
|
|
#ifdef CONFIG_HIGHMEM
|
|
int node;
|
|
unsigned long x = 0;
|
|
|
|
for_each_node_state(node, N_HIGH_MEMORY) {
|
|
struct zone *z =
|
|
&NODE_DATA(node)->node_zones[ZONE_HIGHMEM];
|
|
|
|
x += zone_page_state(z, NR_FREE_PAGES) +
|
|
zone_reclaimable_pages(z);
|
|
}
|
|
/*
|
|
* Make sure that the number of highmem pages is never larger
|
|
* than the number of the total dirtyable memory. This can only
|
|
* occur in very strange VM situations but we want to make sure
|
|
* that this does not occur.
|
|
*/
|
|
return min(x, total);
|
|
#else
|
|
return 0;
|
|
#endif
|
|
}
|
|
|
|
/**
|
|
* determine_dirtyable_memory - amount of memory that may be used
|
|
*
|
|
* Returns the numebr of pages that can currently be freed and used
|
|
* by the kernel for direct mappings.
|
|
*/
|
|
unsigned long determine_dirtyable_memory(void)
|
|
{
|
|
unsigned long x;
|
|
|
|
x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages();
|
|
|
|
if (!vm_highmem_is_dirtyable)
|
|
x -= highmem_dirtyable_memory(x);
|
|
|
|
return x + 1; /* Ensure that we never return 0 */
|
|
}
|
|
|
|
static unsigned long dirty_freerun_ceiling(unsigned long thresh,
|
|
unsigned long bg_thresh)
|
|
{
|
|
return (thresh + bg_thresh) / 2;
|
|
}
|
|
|
|
static unsigned long hard_dirty_limit(unsigned long thresh)
|
|
{
|
|
return max(thresh, global_dirty_limit);
|
|
}
|
|
|
|
/*
|
|
* global_dirty_limits - background-writeback and dirty-throttling thresholds
|
|
*
|
|
* Calculate the dirty thresholds based on sysctl parameters
|
|
* - vm.dirty_background_ratio or vm.dirty_background_bytes
|
|
* - vm.dirty_ratio or vm.dirty_bytes
|
|
* The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and
|
|
* real-time tasks.
|
|
*/
|
|
void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)
|
|
{
|
|
unsigned long background;
|
|
unsigned long dirty;
|
|
unsigned long uninitialized_var(available_memory);
|
|
struct task_struct *tsk;
|
|
|
|
if (!vm_dirty_bytes || !dirty_background_bytes)
|
|
available_memory = determine_dirtyable_memory();
|
|
|
|
if (vm_dirty_bytes)
|
|
dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
|
|
else
|
|
dirty = (vm_dirty_ratio * available_memory) / 100;
|
|
|
|
if (dirty_background_bytes)
|
|
background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
|
|
else
|
|
background = (dirty_background_ratio * available_memory) / 100;
|
|
|
|
if (background >= dirty)
|
|
background = dirty / 2;
|
|
tsk = current;
|
|
if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
|
|
background += background / 4;
|
|
dirty += dirty / 4;
|
|
}
|
|
*pbackground = background;
|
|
*pdirty = dirty;
|
|
trace_global_dirty_state(background, dirty);
|
|
}
|
|
|
|
/**
|
|
* bdi_dirty_limit - @bdi's share of dirty throttling threshold
|
|
* @bdi: the backing_dev_info to query
|
|
* @dirty: global dirty limit in pages
|
|
*
|
|
* Returns @bdi's dirty limit in pages. The term "dirty" in the context of
|
|
* dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages.
|
|
* And the "limit" in the name is not seriously taken as hard limit in
|
|
* balance_dirty_pages().
|
|
*
|
|
* 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 bdi'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.
|
|
*/
|
|
unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty)
|
|
{
|
|
u64 bdi_dirty;
|
|
long numerator, denominator;
|
|
|
|
/*
|
|
* Calculate this BDI's share of the dirty ratio.
|
|
*/
|
|
bdi_writeout_fraction(bdi, &numerator, &denominator);
|
|
|
|
bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
|
|
bdi_dirty *= numerator;
|
|
do_div(bdi_dirty, denominator);
|
|
|
|
bdi_dirty += (dirty * bdi->min_ratio) / 100;
|
|
if (bdi_dirty > (dirty * bdi->max_ratio) / 100)
|
|
bdi_dirty = dirty * bdi->max_ratio / 100;
|
|
|
|
return bdi_dirty;
|
|
}
|
|
|
|
/*
|
|
* Dirty position control.
|
|
*
|
|
* (o) global/bdi setpoints
|
|
*
|
|
* We want the dirty pages be balanced around the global/bdi 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 (bdi_dirty < bdi_setpoint) scale up pos_ratio
|
|
* if (bdi_dirty > bdi_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) bdi control line
|
|
*
|
|
* ^ pos_ratio
|
|
* |
|
|
* | *
|
|
* | *
|
|
* | *
|
|
* | *
|
|
* | * |<=========== span ============>|
|
|
* 1.0 .......................*
|
|
* | . *
|
|
* | . *
|
|
* | . *
|
|
* | . *
|
|
* | . *
|
|
* | . *
|
|
* | . *
|
|
* | . *
|
|
* | . *
|
|
* | . *
|
|
* | . *
|
|
* 1/4 ...............................................* * * * * * * * * * * *
|
|
* | . .
|
|
* | . .
|
|
* | . .
|
|
* 0 +----------------------.-------------------------------.------------->
|
|
* bdi_setpoint^ x_intercept^
|
|
*
|
|
* The bdi control line won't drop below pos_ratio=1/4, so that bdi_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 bdi_dirty may rush to many times higher than bdi_setpoint.
|
|
* - the bdi dirty thresh drops quickly due to change of JBOD workload
|
|
*/
|
|
static unsigned long bdi_position_ratio(struct backing_dev_info *bdi,
|
|
unsigned long thresh,
|
|
unsigned long bg_thresh,
|
|
unsigned long dirty,
|
|
unsigned long bdi_thresh,
|
|
unsigned long bdi_dirty)
|
|
{
|
|
unsigned long write_bw = bdi->avg_write_bandwidth;
|
|
unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh);
|
|
unsigned long limit = hard_dirty_limit(thresh);
|
|
unsigned long x_intercept;
|
|
unsigned long setpoint; /* dirty pages' target balance point */
|
|
unsigned long bdi_setpoint;
|
|
unsigned long span;
|
|
long long pos_ratio; /* for scaling up/down the rate limit */
|
|
long x;
|
|
|
|
if (unlikely(dirty >= limit))
|
|
return 0;
|
|
|
|
/*
|
|
* global setpoint
|
|
*
|
|
* 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
|
|
*/
|
|
setpoint = (freerun + limit) / 2;
|
|
x = div_s64((setpoint - dirty) << RATELIMIT_CALC_SHIFT,
|
|
limit - setpoint + 1);
|
|
pos_ratio = x;
|
|
pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT;
|
|
pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT;
|
|
pos_ratio += 1 << RATELIMIT_CALC_SHIFT;
|
|
|
|
/*
|
|
* We have computed basic pos_ratio above based on global situation. If
|
|
* the bdi is over/under its share of dirty pages, we want to scale
|
|
* pos_ratio further down/up. That is done by the following mechanism.
|
|
*/
|
|
|
|
/*
|
|
* bdi setpoint
|
|
*
|
|
* f(bdi_dirty) := 1.0 + k * (bdi_dirty - bdi_setpoint)
|
|
*
|
|
* x_intercept - bdi_dirty
|
|
* := --------------------------
|
|
* x_intercept - bdi_setpoint
|
|
*
|
|
* The main bdi control line is a linear function that subjects to
|
|
*
|
|
* (1) f(bdi_setpoint) = 1.0
|
|
* (2) k = - 1 / (8 * write_bw) (in single bdi case)
|
|
* or equally: x_intercept = bdi_setpoint + 8 * write_bw
|
|
*
|
|
* For single bdi case, the dirty pages are observed to fluctuate
|
|
* regularly within range
|
|
* [bdi_setpoint - write_bw/2, bdi_setpoint + write_bw/2]
|
|
* for various filesystems, where (2) can yield in a reasonable 12.5%
|
|
* fluctuation range for pos_ratio.
|
|
*
|
|
* For JBOD case, bdi_thresh (not bdi_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 bdi_thresh.
|
|
*/
|
|
if (unlikely(bdi_thresh > thresh))
|
|
bdi_thresh = thresh;
|
|
bdi_thresh = max(bdi_thresh, (limit - dirty) / 8);
|
|
/*
|
|
* scale global setpoint to bdi's:
|
|
* bdi_setpoint = setpoint * bdi_thresh / thresh
|
|
*/
|
|
x = div_u64((u64)bdi_thresh << 16, thresh + 1);
|
|
bdi_setpoint = setpoint * (u64)x >> 16;
|
|
/*
|
|
* Use span=(8*write_bw) in single bdi case as indicated by
|
|
* (thresh - bdi_thresh ~= 0) and transit to bdi_thresh in JBOD case.
|
|
*
|
|
* bdi_thresh thresh - bdi_thresh
|
|
* span = ---------- * (8 * write_bw) + ------------------- * bdi_thresh
|
|
* thresh thresh
|
|
*/
|
|
span = (thresh - bdi_thresh + 8 * write_bw) * (u64)x >> 16;
|
|
x_intercept = bdi_setpoint + span;
|
|
|
|
if (bdi_dirty < x_intercept - span / 4) {
|
|
pos_ratio = div_u64(pos_ratio * (x_intercept - bdi_dirty),
|
|
x_intercept - bdi_setpoint + 1);
|
|
} else
|
|
pos_ratio /= 4;
|
|
|
|
/*
|
|
* bdi 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 = bdi_thresh / 2;
|
|
if (bdi_dirty < x_intercept) {
|
|
if (bdi_dirty > x_intercept / 8)
|
|
pos_ratio = div_u64(pos_ratio * x_intercept, bdi_dirty);
|
|
else
|
|
pos_ratio *= 8;
|
|
}
|
|
|
|
return pos_ratio;
|
|
}
|
|
|
|
static void bdi_update_write_bandwidth(struct backing_dev_info *bdi,
|
|
unsigned long elapsed,
|
|
unsigned long written)
|
|
{
|
|
const unsigned long period = roundup_pow_of_two(3 * HZ);
|
|
unsigned long avg = bdi->avg_write_bandwidth;
|
|
unsigned long old = bdi->write_bandwidth;
|
|
u64 bw;
|
|
|
|
/*
|
|
* bw = written * HZ / elapsed
|
|
*
|
|
* bw * elapsed + write_bandwidth * (period - elapsed)
|
|
* write_bandwidth = ---------------------------------------------------
|
|
* period
|
|
*/
|
|
bw = written - bdi->written_stamp;
|
|
bw *= HZ;
|
|
if (unlikely(elapsed > period)) {
|
|
do_div(bw, elapsed);
|
|
avg = bw;
|
|
goto out;
|
|
}
|
|
bw += (u64)bdi->write_bandwidth * (period - elapsed);
|
|
bw >>= ilog2(period);
|
|
|
|
/*
|
|
* 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:
|
|
bdi->write_bandwidth = bw;
|
|
bdi->avg_write_bandwidth = avg;
|
|
}
|
|
|
|
/*
|
|
* The global dirtyable memory and dirty threshold could be suddenly knocked
|
|
* down by a large amount (eg. on the startup of KVM in a swapless system).
|
|
* This may throw the system into deep dirty exceeded state and throttle
|
|
* heavy/light dirtiers alike. To retain good responsiveness, maintain
|
|
* global_dirty_limit for tracking slowly down to the knocked down dirty
|
|
* threshold.
|
|
*/
|
|
static void update_dirty_limit(unsigned long thresh, unsigned long dirty)
|
|
{
|
|
unsigned long limit = global_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
|
|
* global_dirty_limit which is guaranteed to lie above the dirty pages.
|
|
*/
|
|
thresh = max(thresh, dirty);
|
|
if (limit > thresh) {
|
|
limit -= (limit - thresh) >> 5;
|
|
goto update;
|
|
}
|
|
return;
|
|
update:
|
|
global_dirty_limit = limit;
|
|
}
|
|
|
|
static void global_update_bandwidth(unsigned long thresh,
|
|
unsigned long dirty,
|
|
unsigned long now)
|
|
{
|
|
static DEFINE_SPINLOCK(dirty_lock);
|
|
static unsigned long update_time;
|
|
|
|
/*
|
|
* check locklessly first to optimize away locking for the most time
|
|
*/
|
|
if (time_before(now, update_time + BANDWIDTH_INTERVAL))
|
|
return;
|
|
|
|
spin_lock(&dirty_lock);
|
|
if (time_after_eq(now, update_time + BANDWIDTH_INTERVAL)) {
|
|
update_dirty_limit(thresh, dirty);
|
|
update_time = now;
|
|
}
|
|
spin_unlock(&dirty_lock);
|
|
}
|
|
|
|
/*
|
|
* Maintain bdi->dirty_ratelimit, the base dirty throttle rate.
|
|
*
|
|
* Normal bdi 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 bdi_update_dirty_ratelimit(struct backing_dev_info *bdi,
|
|
unsigned long thresh,
|
|
unsigned long bg_thresh,
|
|
unsigned long dirty,
|
|
unsigned long bdi_thresh,
|
|
unsigned long bdi_dirty,
|
|
unsigned long dirtied,
|
|
unsigned long elapsed)
|
|
{
|
|
unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh);
|
|
unsigned long limit = hard_dirty_limit(thresh);
|
|
unsigned long setpoint = (freerun + limit) / 2;
|
|
unsigned long write_bw = bdi->avg_write_bandwidth;
|
|
unsigned long dirty_ratelimit = bdi->dirty_ratelimit;
|
|
unsigned long dirty_rate;
|
|
unsigned long task_ratelimit;
|
|
unsigned long balanced_dirty_ratelimit;
|
|
unsigned long pos_ratio;
|
|
unsigned long step;
|
|
unsigned long x;
|
|
|
|
/*
|
|
* 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 - bdi->dirtied_stamp) * HZ / elapsed;
|
|
|
|
pos_ratio = bdi_position_ratio(bdi, thresh, bg_thresh, dirty,
|
|
bdi_thresh, bdi_dirty);
|
|
/*
|
|
* task_ratelimit reflects each dd's dirty rate for the past 200ms.
|
|
*/
|
|
task_ratelimit = (u64)dirty_ratelimit *
|
|
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 bdi'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);
|
|
|
|
/*
|
|
* We could safely do this and return immediately:
|
|
*
|
|
* bdi->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 sigular 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 sigular 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;
|
|
if (dirty < setpoint) {
|
|
x = min(bdi->balanced_dirty_ratelimit,
|
|
min(balanced_dirty_ratelimit, task_ratelimit));
|
|
if (dirty_ratelimit < x)
|
|
step = x - dirty_ratelimit;
|
|
} else {
|
|
x = max(bdi->balanced_dirty_ratelimit,
|
|
max(balanced_dirty_ratelimit, task_ratelimit));
|
|
if (dirty_ratelimit > x)
|
|
step = dirty_ratelimit - x;
|
|
}
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
step >>= dirty_ratelimit / (2 * step + 1);
|
|
/*
|
|
* Limit the tracking speed to avoid overshooting.
|
|
*/
|
|
step = (step + 7) / 8;
|
|
|
|
if (dirty_ratelimit < balanced_dirty_ratelimit)
|
|
dirty_ratelimit += step;
|
|
else
|
|
dirty_ratelimit -= step;
|
|
|
|
bdi->dirty_ratelimit = max(dirty_ratelimit, 1UL);
|
|
bdi->balanced_dirty_ratelimit = balanced_dirty_ratelimit;
|
|
|
|
trace_bdi_dirty_ratelimit(bdi, dirty_rate, task_ratelimit);
|
|
}
|
|
|
|
void __bdi_update_bandwidth(struct backing_dev_info *bdi,
|
|
unsigned long thresh,
|
|
unsigned long bg_thresh,
|
|
unsigned long dirty,
|
|
unsigned long bdi_thresh,
|
|
unsigned long bdi_dirty,
|
|
unsigned long start_time)
|
|
{
|
|
unsigned long now = jiffies;
|
|
unsigned long elapsed = now - bdi->bw_time_stamp;
|
|
unsigned long dirtied;
|
|
unsigned long written;
|
|
|
|
/*
|
|
* rate-limit, only update once every 200ms.
|
|
*/
|
|
if (elapsed < BANDWIDTH_INTERVAL)
|
|
return;
|
|
|
|
dirtied = percpu_counter_read(&bdi->bdi_stat[BDI_DIRTIED]);
|
|
written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]);
|
|
|
|
/*
|
|
* Skip quiet periods when disk bandwidth is under-utilized.
|
|
* (at least 1s idle time between two flusher runs)
|
|
*/
|
|
if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time))
|
|
goto snapshot;
|
|
|
|
if (thresh) {
|
|
global_update_bandwidth(thresh, dirty, now);
|
|
bdi_update_dirty_ratelimit(bdi, thresh, bg_thresh, dirty,
|
|
bdi_thresh, bdi_dirty,
|
|
dirtied, elapsed);
|
|
}
|
|
bdi_update_write_bandwidth(bdi, elapsed, written);
|
|
|
|
snapshot:
|
|
bdi->dirtied_stamp = dirtied;
|
|
bdi->written_stamp = written;
|
|
bdi->bw_time_stamp = now;
|
|
}
|
|
|
|
static void bdi_update_bandwidth(struct backing_dev_info *bdi,
|
|
unsigned long thresh,
|
|
unsigned long bg_thresh,
|
|
unsigned long dirty,
|
|
unsigned long bdi_thresh,
|
|
unsigned long bdi_dirty,
|
|
unsigned long start_time)
|
|
{
|
|
if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL))
|
|
return;
|
|
spin_lock(&bdi->wb.list_lock);
|
|
__bdi_update_bandwidth(bdi, thresh, bg_thresh, dirty,
|
|
bdi_thresh, bdi_dirty, start_time);
|
|
spin_unlock(&bdi->wb.list_lock);
|
|
}
|
|
|
|
/*
|
|
* After a task dirtied this many pages, balance_dirty_pages_ratelimited_nr()
|
|
* 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_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 bdi_max_pause(struct backing_dev_info *bdi,
|
|
unsigned long bdi_dirty)
|
|
{
|
|
unsigned long bw = bdi->avg_write_bandwidth;
|
|
unsigned long hi = ilog2(bw);
|
|
unsigned long lo = ilog2(bdi->dirty_ratelimit);
|
|
unsigned long t;
|
|
|
|
/* target for 20ms max pause on 1-dd case */
|
|
t = HZ / 50;
|
|
|
|
/*
|
|
* Scale up pause time for concurrent dirtiers in order to reduce CPU
|
|
* overheads.
|
|
*
|
|
* (N * 20ms) on 2^N concurrent tasks.
|
|
*/
|
|
if (hi > lo)
|
|
t += (hi - lo) * (20 * HZ) / 1024;
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
if (bdi_dirty)
|
|
t = min(t, bdi_dirty * HZ / (8 * bw + 1));
|
|
|
|
/*
|
|
* The pause time will be settled within range (max_pause/4, max_pause).
|
|
* Apply a minimal value of 4 to get a non-zero max_pause/4.
|
|
*/
|
|
return clamp_val(t, 4, MAX_PAUSE);
|
|
}
|
|
|
|
/*
|
|
* balance_dirty_pages() must be called by processes which are generating dirty
|
|
* data. It looks at the number of dirty pages in the machine and will force
|
|
* the caller to wait once crossing the (background_thresh + dirty_thresh) / 2.
|
|
* If we're over `background_thresh' then the writeback threads are woken to
|
|
* perform some writeout.
|
|
*/
|
|
static void balance_dirty_pages(struct address_space *mapping,
|
|
unsigned long pages_dirtied)
|
|
{
|
|
unsigned long nr_reclaimable; /* = file_dirty + unstable_nfs */
|
|
unsigned long bdi_reclaimable;
|
|
unsigned long nr_dirty; /* = file_dirty + writeback + unstable_nfs */
|
|
unsigned long bdi_dirty;
|
|
unsigned long freerun;
|
|
unsigned long background_thresh;
|
|
unsigned long dirty_thresh;
|
|
unsigned long bdi_thresh;
|
|
long pause = 0;
|
|
long uninitialized_var(max_pause);
|
|
bool dirty_exceeded = false;
|
|
unsigned long task_ratelimit;
|
|
unsigned long uninitialized_var(dirty_ratelimit);
|
|
unsigned long pos_ratio;
|
|
struct backing_dev_info *bdi = mapping->backing_dev_info;
|
|
unsigned long start_time = jiffies;
|
|
|
|
for (;;) {
|
|
/*
|
|
* Unstable writes are a feature of certain networked
|
|
* filesystems (i.e. NFS) in which data may have been
|
|
* written to the server's write cache, but has not yet
|
|
* been flushed to permanent storage.
|
|
*/
|
|
nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
|
|
global_page_state(NR_UNSTABLE_NFS);
|
|
nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK);
|
|
|
|
global_dirty_limits(&background_thresh, &dirty_thresh);
|
|
|
|
/*
|
|
* Throttle it only when the background writeback cannot
|
|
* catch-up. This avoids (excessively) small writeouts
|
|
* when the bdi limits are ramping up.
|
|
*/
|
|
freerun = dirty_freerun_ceiling(dirty_thresh,
|
|
background_thresh);
|
|
if (nr_dirty <= freerun)
|
|
break;
|
|
|
|
if (unlikely(!writeback_in_progress(bdi)))
|
|
bdi_start_background_writeback(bdi);
|
|
|
|
/*
|
|
* bdi_thresh is not treated as some limiting factor as
|
|
* dirty_thresh, due to reasons
|
|
* - in JBOD setup, bdi_thresh can fluctuate a lot
|
|
* - in a system with HDD and USB key, the USB key may somehow
|
|
* go into state (bdi_dirty >> bdi_thresh) either because
|
|
* bdi_dirty starts high, or because bdi_thresh drops low.
|
|
* In this case we don't want to hard throttle the USB key
|
|
* dirtiers for 100 seconds until bdi_dirty drops under
|
|
* bdi_thresh. Instead the auxiliary bdi control line in
|
|
* bdi_position_ratio() will let the dirtier task progress
|
|
* at some rate <= (write_bw / 2) for bringing down bdi_dirty.
|
|
*/
|
|
bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
|
|
|
|
/*
|
|
* In order to avoid the stacked BDI deadlock we need
|
|
* to ensure we accurately count the 'dirty' pages when
|
|
* the threshold is low.
|
|
*
|
|
* Otherwise it would be possible to get thresh+n pages
|
|
* reported dirty, even though there are thresh-m pages
|
|
* actually dirty; with m+n sitting in the percpu
|
|
* deltas.
|
|
*/
|
|
if (bdi_thresh < 2 * bdi_stat_error(bdi)) {
|
|
bdi_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE);
|
|
bdi_dirty = bdi_reclaimable +
|
|
bdi_stat_sum(bdi, BDI_WRITEBACK);
|
|
} else {
|
|
bdi_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
|
|
bdi_dirty = bdi_reclaimable +
|
|
bdi_stat(bdi, BDI_WRITEBACK);
|
|
}
|
|
|
|
dirty_exceeded = (bdi_dirty > bdi_thresh) ||
|
|
(nr_dirty > dirty_thresh);
|
|
if (dirty_exceeded && !bdi->dirty_exceeded)
|
|
bdi->dirty_exceeded = 1;
|
|
|
|
bdi_update_bandwidth(bdi, dirty_thresh, background_thresh,
|
|
nr_dirty, bdi_thresh, bdi_dirty,
|
|
start_time);
|
|
|
|
max_pause = bdi_max_pause(bdi, bdi_dirty);
|
|
|
|
dirty_ratelimit = bdi->dirty_ratelimit;
|
|
pos_ratio = bdi_position_ratio(bdi, dirty_thresh,
|
|
background_thresh, nr_dirty,
|
|
bdi_thresh, bdi_dirty);
|
|
if (unlikely(pos_ratio == 0)) {
|
|
pause = max_pause;
|
|
goto pause;
|
|
}
|
|
task_ratelimit = (u64)dirty_ratelimit *
|
|
pos_ratio >> RATELIMIT_CALC_SHIFT;
|
|
pause = (HZ * pages_dirtied) / (task_ratelimit | 1);
|
|
if (unlikely(pause <= 0)) {
|
|
trace_balance_dirty_pages(bdi,
|
|
dirty_thresh,
|
|
background_thresh,
|
|
nr_dirty,
|
|
bdi_thresh,
|
|
bdi_dirty,
|
|
dirty_ratelimit,
|
|
task_ratelimit,
|
|
pages_dirtied,
|
|
pause,
|
|
start_time);
|
|
pause = 1; /* avoid resetting nr_dirtied_pause below */
|
|
break;
|
|
}
|
|
pause = min(pause, max_pause);
|
|
|
|
pause:
|
|
trace_balance_dirty_pages(bdi,
|
|
dirty_thresh,
|
|
background_thresh,
|
|
nr_dirty,
|
|
bdi_thresh,
|
|
bdi_dirty,
|
|
dirty_ratelimit,
|
|
task_ratelimit,
|
|
pages_dirtied,
|
|
pause,
|
|
start_time);
|
|
__set_current_state(TASK_UNINTERRUPTIBLE);
|
|
io_schedule_timeout(pause);
|
|
|
|
dirty_thresh = hard_dirty_limit(dirty_thresh);
|
|
/*
|
|
* max-pause area. If dirty exceeded but still within this
|
|
* area, no need to sleep for more than 200ms: (a) 8 pages per
|
|
* 200ms is typically more than enough to curb heavy dirtiers;
|
|
* (b) the pause time limit makes the dirtiers more responsive.
|
|
*/
|
|
if (nr_dirty < dirty_thresh)
|
|
break;
|
|
}
|
|
|
|
if (!dirty_exceeded && bdi->dirty_exceeded)
|
|
bdi->dirty_exceeded = 0;
|
|
|
|
current->nr_dirtied = 0;
|
|
if (pause == 0) { /* in freerun area */
|
|
current->nr_dirtied_pause =
|
|
dirty_poll_interval(nr_dirty, dirty_thresh);
|
|
} else if (pause <= max_pause / 4 &&
|
|
pages_dirtied >= current->nr_dirtied_pause) {
|
|
current->nr_dirtied_pause = clamp_val(
|
|
dirty_ratelimit * (max_pause / 2) / HZ,
|
|
pages_dirtied + pages_dirtied / 8,
|
|
pages_dirtied * 4);
|
|
} else if (pause >= max_pause) {
|
|
current->nr_dirtied_pause = 1 | clamp_val(
|
|
dirty_ratelimit * (max_pause / 2) / HZ,
|
|
pages_dirtied / 4,
|
|
pages_dirtied - pages_dirtied / 8);
|
|
}
|
|
|
|
if (writeback_in_progress(bdi))
|
|
return;
|
|
|
|
/*
|
|
* In laptop mode, we wait until hitting the higher threshold before
|
|
* starting background writeout, and then write out all the way down
|
|
* to the lower threshold. So slow writers cause minimal disk activity.
|
|
*
|
|
* In normal mode, we start background writeout at the lower
|
|
* background_thresh, to keep the amount of dirty memory low.
|
|
*/
|
|
if (laptop_mode)
|
|
return;
|
|
|
|
if (nr_reclaimable > background_thresh)
|
|
bdi_start_background_writeback(bdi);
|
|
}
|
|
|
|
void set_page_dirty_balance(struct page *page, int page_mkwrite)
|
|
{
|
|
if (set_page_dirty(page) || page_mkwrite) {
|
|
struct address_space *mapping = page_mapping(page);
|
|
|
|
if (mapping)
|
|
balance_dirty_pages_ratelimited(mapping);
|
|
}
|
|
}
|
|
|
|
static DEFINE_PER_CPU(int, bdp_ratelimits);
|
|
|
|
/**
|
|
* balance_dirty_pages_ratelimited_nr - balance dirty memory state
|
|
* @mapping: address_space which was dirtied
|
|
* @nr_pages_dirtied: number of pages which the caller has just dirtied
|
|
*
|
|
* Processes which are dirtying memory should call in here once for each page
|
|
* which was newly dirtied. The function will periodically check the system's
|
|
* dirty state and will initiate writeback if needed.
|
|
*
|
|
* On really big machines, get_writeback_state is expensive, so try to avoid
|
|
* calling it too often (ratelimiting). But once we're over the dirty memory
|
|
* limit we decrease the ratelimiting by a lot, to prevent individual processes
|
|
* from overshooting the limit by (ratelimit_pages) each.
|
|
*/
|
|
void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
|
|
unsigned long nr_pages_dirtied)
|
|
{
|
|
struct backing_dev_info *bdi = mapping->backing_dev_info;
|
|
int ratelimit;
|
|
int *p;
|
|
|
|
if (!bdi_cap_account_dirty(bdi))
|
|
return;
|
|
|
|
ratelimit = current->nr_dirtied_pause;
|
|
if (bdi->dirty_exceeded)
|
|
ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10));
|
|
|
|
current->nr_dirtied += nr_pages_dirtied;
|
|
|
|
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 = &__get_cpu_var(bdp_ratelimits);
|
|
if (unlikely(current->nr_dirtied >= ratelimit))
|
|
*p = 0;
|
|
else {
|
|
*p += nr_pages_dirtied;
|
|
if (unlikely(*p >= ratelimit_pages)) {
|
|
*p = 0;
|
|
ratelimit = 0;
|
|
}
|
|
}
|
|
preempt_enable();
|
|
|
|
if (unlikely(current->nr_dirtied >= ratelimit))
|
|
balance_dirty_pages(mapping, current->nr_dirtied);
|
|
}
|
|
EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
|
|
|
|
void throttle_vm_writeout(gfp_t gfp_mask)
|
|
{
|
|
unsigned long background_thresh;
|
|
unsigned long dirty_thresh;
|
|
|
|
for ( ; ; ) {
|
|
global_dirty_limits(&background_thresh, &dirty_thresh);
|
|
|
|
/*
|
|
* Boost the allowable dirty threshold a bit for page
|
|
* allocators so they don't get DoS'ed by heavy writers
|
|
*/
|
|
dirty_thresh += dirty_thresh / 10; /* wheeee... */
|
|
|
|
if (global_page_state(NR_UNSTABLE_NFS) +
|
|
global_page_state(NR_WRITEBACK) <= dirty_thresh)
|
|
break;
|
|
congestion_wait(BLK_RW_ASYNC, HZ/10);
|
|
|
|
/*
|
|
* The caller might hold locks which can prevent IO completion
|
|
* or progress in the filesystem. So we cannot just sit here
|
|
* waiting for IO to complete.
|
|
*/
|
|
if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO))
|
|
break;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* sysctl handler for /proc/sys/vm/dirty_writeback_centisecs
|
|
*/
|
|
int dirty_writeback_centisecs_handler(ctl_table *table, int write,
|
|
void __user *buffer, size_t *length, loff_t *ppos)
|
|
{
|
|
proc_dointvec(table, write, buffer, length, ppos);
|
|
bdi_arm_supers_timer();
|
|
return 0;
|
|
}
|
|
|
|
#ifdef CONFIG_BLOCK
|
|
void laptop_mode_timer_fn(unsigned long data)
|
|
{
|
|
struct request_queue *q = (struct request_queue *)data;
|
|
int nr_pages = global_page_state(NR_FILE_DIRTY) +
|
|
global_page_state(NR_UNSTABLE_NFS);
|
|
|
|
/*
|
|
* We want to write everything out, not just down to the dirty
|
|
* threshold
|
|
*/
|
|
if (bdi_has_dirty_io(&q->backing_dev_info))
|
|
bdi_start_writeback(&q->backing_dev_info, nr_pages,
|
|
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();
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* If ratelimit_pages is too high then we can get into dirty-data overload
|
|
* if a large number of processes all perform writes at the same time.
|
|
* If it is too low then SMP machines will call the (expensive)
|
|
* get_writeback_state too often.
|
|
*
|
|
* Here we set ratelimit_pages to a level which ensures that when all CPUs are
|
|
* dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory
|
|
* thresholds.
|
|
*/
|
|
|
|
void writeback_set_ratelimit(void)
|
|
{
|
|
unsigned long background_thresh;
|
|
unsigned long dirty_thresh;
|
|
global_dirty_limits(&background_thresh, &dirty_thresh);
|
|
ratelimit_pages = dirty_thresh / (num_online_cpus() * 32);
|
|
if (ratelimit_pages < 16)
|
|
ratelimit_pages = 16;
|
|
}
|
|
|
|
static int __cpuinit
|
|
ratelimit_handler(struct notifier_block *self, unsigned long u, void *v)
|
|
{
|
|
writeback_set_ratelimit();
|
|
return NOTIFY_DONE;
|
|
}
|
|
|
|
static struct notifier_block __cpuinitdata ratelimit_nb = {
|
|
.notifier_call = ratelimit_handler,
|
|
.next = NULL,
|
|
};
|
|
|
|
/*
|
|
* Called early on to tune the page writeback dirty limits.
|
|
*
|
|
* We used to scale dirty pages according to how total memory
|
|
* related to pages that could be allocated for buffers (by
|
|
* comparing nr_free_buffer_pages() to vm_total_pages.
|
|
*
|
|
* However, that was when we used "dirty_ratio" to scale with
|
|
* all memory, and we don't do that any more. "dirty_ratio"
|
|
* is now applied to total non-HIGHPAGE memory (by subtracting
|
|
* totalhigh_pages from vm_total_pages), and as such we can't
|
|
* get into the old insane situation any more where we had
|
|
* large amounts of dirty pages compared to a small amount of
|
|
* non-HIGHMEM memory.
|
|
*
|
|
* But we might still want to scale the dirty_ratio by how
|
|
* much memory the box has..
|
|
*/
|
|
void __init page_writeback_init(void)
|
|
{
|
|
int shift;
|
|
|
|
writeback_set_ratelimit();
|
|
register_cpu_notifier(&ratelimit_nb);
|
|
|
|
shift = calc_period_shift();
|
|
prop_descriptor_init(&vm_completions, shift);
|
|
prop_descriptor_init(&vm_dirties, shift);
|
|
}
|
|
|
|
/**
|
|
* tag_pages_for_writeback - tag pages to be written by write_cache_pages
|
|
* @mapping: address space structure to write
|
|
* @start: starting page index
|
|
* @end: ending page index (inclusive)
|
|
*
|
|
* This function scans the page range from @start to @end (inclusive) and tags
|
|
* all pages that have DIRTY tag set with a special TOWRITE tag. The idea is
|
|
* that write_cache_pages (or whoever calls this function) will then use
|
|
* TOWRITE tag to identify pages eligible for writeback. This mechanism is
|
|
* used to avoid livelocking of writeback by a process steadily creating new
|
|
* dirty pages in the file (thus it is important for this function to be quick
|
|
* so that it can tag pages faster than a dirtying process can create them).
|
|
*/
|
|
/*
|
|
* We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency.
|
|
*/
|
|
void tag_pages_for_writeback(struct address_space *mapping,
|
|
pgoff_t start, pgoff_t end)
|
|
{
|
|
#define WRITEBACK_TAG_BATCH 4096
|
|
unsigned long tagged;
|
|
|
|
do {
|
|
spin_lock_irq(&mapping->tree_lock);
|
|
tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree,
|
|
&start, end, WRITEBACK_TAG_BATCH,
|
|
PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE);
|
|
spin_unlock_irq(&mapping->tree_lock);
|
|
WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH);
|
|
cond_resched();
|
|
/* We check 'start' to handle wrapping when end == ~0UL */
|
|
} while (tagged >= WRITEBACK_TAG_BATCH && start);
|
|
}
|
|
EXPORT_SYMBOL(tag_pages_for_writeback);
|
|
|
|
/**
|
|
* write_cache_pages - walk the list of dirty pages of the given address space and write all of them.
|
|
* @mapping: address space structure to write
|
|
* @wbc: subtract the number of written pages from *@wbc->nr_to_write
|
|
* @writepage: function called for each page
|
|
* @data: data passed to writepage function
|
|
*
|
|
* If a page is already under I/O, write_cache_pages() skips it, even
|
|
* if it's dirty. This is desirable behaviour for memory-cleaning writeback,
|
|
* but it is INCORRECT for data-integrity system calls such as fsync(). fsync()
|
|
* and msync() need to guarantee that all the data which was dirty at the time
|
|
* the call was made get new I/O started against them. If wbc->sync_mode is
|
|
* WB_SYNC_ALL then we were called for data integrity and we must wait for
|
|
* existing IO to complete.
|
|
*
|
|
* To avoid livelocks (when other process dirties new pages), we first tag
|
|
* pages which should be written back with TOWRITE tag and only then start
|
|
* writing them. For data-integrity sync we have to be careful so that we do
|
|
* not miss some pages (e.g., because some other process has cleared TOWRITE
|
|
* tag we set). The rule we follow is that TOWRITE tag can be cleared only
|
|
* by the process clearing the DIRTY tag (and submitting the page for IO).
|
|
*/
|
|
int write_cache_pages(struct address_space *mapping,
|
|
struct writeback_control *wbc, writepage_t writepage,
|
|
void *data)
|
|
{
|
|
int ret = 0;
|
|
int done = 0;
|
|
struct pagevec pvec;
|
|
int nr_pages;
|
|
pgoff_t uninitialized_var(writeback_index);
|
|
pgoff_t index;
|
|
pgoff_t end; /* Inclusive */
|
|
pgoff_t done_index;
|
|
int cycled;
|
|
int range_whole = 0;
|
|
int tag;
|
|
|
|
pagevec_init(&pvec, 0);
|
|
if (wbc->range_cyclic) {
|
|
writeback_index = mapping->writeback_index; /* prev offset */
|
|
index = writeback_index;
|
|
if (index == 0)
|
|
cycled = 1;
|
|
else
|
|
cycled = 0;
|
|
end = -1;
|
|
} else {
|
|
index = wbc->range_start >> PAGE_CACHE_SHIFT;
|
|
end = wbc->range_end >> PAGE_CACHE_SHIFT;
|
|
if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
|
|
range_whole = 1;
|
|
cycled = 1; /* ignore range_cyclic tests */
|
|
}
|
|
if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
|
|
tag = PAGECACHE_TAG_TOWRITE;
|
|
else
|
|
tag = PAGECACHE_TAG_DIRTY;
|
|
retry:
|
|
if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
|
|
tag_pages_for_writeback(mapping, index, end);
|
|
done_index = index;
|
|
while (!done && (index <= end)) {
|
|
int i;
|
|
|
|
nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag,
|
|
min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1);
|
|
if (nr_pages == 0)
|
|
break;
|
|
|
|
for (i = 0; i < nr_pages; i++) {
|
|
struct page *page = pvec.pages[i];
|
|
|
|
/*
|
|
* At this point, the page may be truncated or
|
|
* invalidated (changing page->mapping to NULL), or
|
|
* even swizzled back from swapper_space to tmpfs file
|
|
* mapping. However, page->index will not change
|
|
* because we have a reference on the page.
|
|
*/
|
|
if (page->index > end) {
|
|
/*
|
|
* can't be range_cyclic (1st pass) because
|
|
* end == -1 in that case.
|
|
*/
|
|
done = 1;
|
|
break;
|
|
}
|
|
|
|
done_index = page->index;
|
|
|
|
lock_page(page);
|
|
|
|
/*
|
|
* Page truncated or invalidated. We can freely skip it
|
|
* then, even for data integrity operations: the page
|
|
* has disappeared concurrently, so there could be no
|
|
* real expectation of this data interity operation
|
|
* even if there is now a new, dirty page at the same
|
|
* pagecache address.
|
|
*/
|
|
if (unlikely(page->mapping != mapping)) {
|
|
continue_unlock:
|
|
unlock_page(page);
|
|
continue;
|
|
}
|
|
|
|
if (!PageDirty(page)) {
|
|
/* someone wrote it for us */
|
|
goto continue_unlock;
|
|
}
|
|
|
|
if (PageWriteback(page)) {
|
|
if (wbc->sync_mode != WB_SYNC_NONE)
|
|
wait_on_page_writeback(page);
|
|
else
|
|
goto continue_unlock;
|
|
}
|
|
|
|
BUG_ON(PageWriteback(page));
|
|
if (!clear_page_dirty_for_io(page))
|
|
goto continue_unlock;
|
|
|
|
trace_wbc_writepage(wbc, mapping->backing_dev_info);
|
|
ret = (*writepage)(page, wbc, data);
|
|
if (unlikely(ret)) {
|
|
if (ret == AOP_WRITEPAGE_ACTIVATE) {
|
|
unlock_page(page);
|
|
ret = 0;
|
|
} else {
|
|
/*
|
|
* done_index is set past this page,
|
|
* so media errors will not choke
|
|
* background writeout for the entire
|
|
* file. This has consequences for
|
|
* range_cyclic semantics (ie. it may
|
|
* not be suitable for data integrity
|
|
* writeout).
|
|
*/
|
|
done_index = page->index + 1;
|
|
done = 1;
|
|
break;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* We stop writing back only if we are not doing
|
|
* integrity sync. In case of integrity sync we have to
|
|
* keep going until we have written all the pages
|
|
* we tagged for writeback prior to entering this loop.
|
|
*/
|
|
if (--wbc->nr_to_write <= 0 &&
|
|
wbc->sync_mode == WB_SYNC_NONE) {
|
|
done = 1;
|
|
break;
|
|
}
|
|
}
|
|
pagevec_release(&pvec);
|
|
cond_resched();
|
|
}
|
|
if (!cycled && !done) {
|
|
/*
|
|
* range_cyclic:
|
|
* We hit the last page and there is more work to be done: wrap
|
|
* back to the start of the file
|
|
*/
|
|
cycled = 1;
|
|
index = 0;
|
|
end = writeback_index - 1;
|
|
goto retry;
|
|
}
|
|
if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
|
|
mapping->writeback_index = done_index;
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(write_cache_pages);
|
|
|
|
/*
|
|
* Function used by generic_writepages to call the real writepage
|
|
* function and set the mapping flags on error
|
|
*/
|
|
static int __writepage(struct page *page, struct writeback_control *wbc,
|
|
void *data)
|
|
{
|
|
struct address_space *mapping = data;
|
|
int ret = mapping->a_ops->writepage(page, wbc);
|
|
mapping_set_error(mapping, ret);
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them.
|
|
* @mapping: address space structure to write
|
|
* @wbc: subtract the number of written pages from *@wbc->nr_to_write
|
|
*
|
|
* This is a library function, which implements the writepages()
|
|
* address_space_operation.
|
|
*/
|
|
int generic_writepages(struct address_space *mapping,
|
|
struct writeback_control *wbc)
|
|
{
|
|
struct blk_plug plug;
|
|
int ret;
|
|
|
|
/* deal with chardevs and other special file */
|
|
if (!mapping->a_ops->writepage)
|
|
return 0;
|
|
|
|
blk_start_plug(&plug);
|
|
ret = write_cache_pages(mapping, wbc, __writepage, mapping);
|
|
blk_finish_plug(&plug);
|
|
return ret;
|
|
}
|
|
|
|
EXPORT_SYMBOL(generic_writepages);
|
|
|
|
int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
|
|
{
|
|
int ret;
|
|
|
|
if (wbc->nr_to_write <= 0)
|
|
return 0;
|
|
if (mapping->a_ops->writepages)
|
|
ret = mapping->a_ops->writepages(mapping, wbc);
|
|
else
|
|
ret = generic_writepages(mapping, wbc);
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* write_one_page - write out a single page and optionally wait on I/O
|
|
* @page: the page to write
|
|
* @wait: if true, wait on writeout
|
|
*
|
|
* The page must be locked by the caller and will be unlocked upon return.
|
|
*
|
|
* write_one_page() returns a negative error code if I/O failed.
|
|
*/
|
|
int write_one_page(struct page *page, int wait)
|
|
{
|
|
struct address_space *mapping = page->mapping;
|
|
int ret = 0;
|
|
struct writeback_control wbc = {
|
|
.sync_mode = WB_SYNC_ALL,
|
|
.nr_to_write = 1,
|
|
};
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
|
|
if (wait)
|
|
wait_on_page_writeback(page);
|
|
|
|
if (clear_page_dirty_for_io(page)) {
|
|
page_cache_get(page);
|
|
ret = mapping->a_ops->writepage(page, &wbc);
|
|
if (ret == 0 && wait) {
|
|
wait_on_page_writeback(page);
|
|
if (PageError(page))
|
|
ret = -EIO;
|
|
}
|
|
page_cache_release(page);
|
|
} else {
|
|
unlock_page(page);
|
|
}
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(write_one_page);
|
|
|
|
/*
|
|
* For address_spaces which do not use buffers nor write back.
|
|
*/
|
|
int __set_page_dirty_no_writeback(struct page *page)
|
|
{
|
|
if (!PageDirty(page))
|
|
return !TestSetPageDirty(page);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Helper function for set_page_dirty family.
|
|
* NOTE: This relies on being atomic wrt interrupts.
|
|
*/
|
|
void account_page_dirtied(struct page *page, struct address_space *mapping)
|
|
{
|
|
if (mapping_cap_account_dirty(mapping)) {
|
|
__inc_zone_page_state(page, NR_FILE_DIRTY);
|
|
__inc_zone_page_state(page, NR_DIRTIED);
|
|
__inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
|
|
__inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED);
|
|
task_dirty_inc(current);
|
|
task_io_account_write(PAGE_CACHE_SIZE);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(account_page_dirtied);
|
|
|
|
/*
|
|
* Helper function for set_page_writeback family.
|
|
* NOTE: Unlike account_page_dirtied this does not rely on being atomic
|
|
* wrt interrupts.
|
|
*/
|
|
void account_page_writeback(struct page *page)
|
|
{
|
|
inc_zone_page_state(page, NR_WRITEBACK);
|
|
}
|
|
EXPORT_SYMBOL(account_page_writeback);
|
|
|
|
/*
|
|
* For address_spaces which do not use buffers. Just tag the page as dirty in
|
|
* its radix tree.
|
|
*
|
|
* This is also used when a single buffer is being dirtied: we want to set the
|
|
* page dirty in that case, but not all the buffers. This is a "bottom-up"
|
|
* dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying.
|
|
*
|
|
* Most callers have locked the page, which pins the address_space in memory.
|
|
* But zap_pte_range() does not lock the page, however in that case the
|
|
* mapping is pinned by the vma's ->vm_file reference.
|
|
*
|
|
* We take care to handle the case where the page was truncated from the
|
|
* mapping by re-checking page_mapping() inside tree_lock.
|
|
*/
|
|
int __set_page_dirty_nobuffers(struct page *page)
|
|
{
|
|
if (!TestSetPageDirty(page)) {
|
|
struct address_space *mapping = page_mapping(page);
|
|
struct address_space *mapping2;
|
|
|
|
if (!mapping)
|
|
return 1;
|
|
|
|
spin_lock_irq(&mapping->tree_lock);
|
|
mapping2 = page_mapping(page);
|
|
if (mapping2) { /* Race with truncate? */
|
|
BUG_ON(mapping2 != mapping);
|
|
WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page));
|
|
account_page_dirtied(page, mapping);
|
|
radix_tree_tag_set(&mapping->page_tree,
|
|
page_index(page), PAGECACHE_TAG_DIRTY);
|
|
}
|
|
spin_unlock_irq(&mapping->tree_lock);
|
|
if (mapping->host) {
|
|
/* !PageAnon && !swapper_space */
|
|
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
|
|
}
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(__set_page_dirty_nobuffers);
|
|
|
|
/*
|
|
* When a writepage implementation decides that it doesn't want to write this
|
|
* page for some reason, it should redirty the locked page via
|
|
* redirty_page_for_writepage() and it should then unlock the page and return 0
|
|
*/
|
|
int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
|
|
{
|
|
wbc->pages_skipped++;
|
|
return __set_page_dirty_nobuffers(page);
|
|
}
|
|
EXPORT_SYMBOL(redirty_page_for_writepage);
|
|
|
|
/*
|
|
* Dirty a page.
|
|
*
|
|
* For pages with a mapping this should be done under the page lock
|
|
* for the benefit of asynchronous memory errors who prefer a consistent
|
|
* dirty state. This rule can be broken in some special cases,
|
|
* but should be better not to.
|
|
*
|
|
* If the mapping doesn't provide a set_page_dirty a_op, then
|
|
* just fall through and assume that it wants buffer_heads.
|
|
*/
|
|
int set_page_dirty(struct page *page)
|
|
{
|
|
struct address_space *mapping = page_mapping(page);
|
|
|
|
if (likely(mapping)) {
|
|
int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
|
|
/*
|
|
* readahead/lru_deactivate_page could remain
|
|
* PG_readahead/PG_reclaim due to race with end_page_writeback
|
|
* About readahead, if the page is written, the flags would be
|
|
* reset. So no problem.
|
|
* About lru_deactivate_page, if the page is redirty, the flag
|
|
* will be reset. So no problem. but if the page is used by readahead
|
|
* it will confuse readahead and make it restart the size rampup
|
|
* process. But it's a trivial problem.
|
|
*/
|
|
ClearPageReclaim(page);
|
|
#ifdef CONFIG_BLOCK
|
|
if (!spd)
|
|
spd = __set_page_dirty_buffers;
|
|
#endif
|
|
return (*spd)(page);
|
|
}
|
|
if (!PageDirty(page)) {
|
|
if (!TestSetPageDirty(page))
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(set_page_dirty);
|
|
|
|
/*
|
|
* set_page_dirty() is racy if the caller has no reference against
|
|
* page->mapping->host, and if the page is unlocked. This is because another
|
|
* CPU could truncate the page off the mapping and then free the mapping.
|
|
*
|
|
* Usually, the page _is_ locked, or the caller is a user-space process which
|
|
* holds a reference on the inode by having an open file.
|
|
*
|
|
* In other cases, the page should be locked before running set_page_dirty().
|
|
*/
|
|
int set_page_dirty_lock(struct page *page)
|
|
{
|
|
int ret;
|
|
|
|
lock_page(page);
|
|
ret = set_page_dirty(page);
|
|
unlock_page(page);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(set_page_dirty_lock);
|
|
|
|
/*
|
|
* Clear a page's dirty flag, while caring for dirty memory accounting.
|
|
* Returns true if the page was previously dirty.
|
|
*
|
|
* This is for preparing to put the page under writeout. We leave the page
|
|
* tagged as dirty in the radix tree so that a concurrent write-for-sync
|
|
* can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage
|
|
* implementation will run either set_page_writeback() or set_page_dirty(),
|
|
* at which stage we bring the page's dirty flag and radix-tree dirty tag
|
|
* back into sync.
|
|
*
|
|
* This incoherency between the page's dirty flag and radix-tree tag is
|
|
* unfortunate, but it only exists while the page is locked.
|
|
*/
|
|
int clear_page_dirty_for_io(struct page *page)
|
|
{
|
|
struct address_space *mapping = page_mapping(page);
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
|
|
if (mapping && mapping_cap_account_dirty(mapping)) {
|
|
/*
|
|
* Yes, Virginia, this is indeed insane.
|
|
*
|
|
* We use this sequence to make sure that
|
|
* (a) we account for dirty stats properly
|
|
* (b) we tell the low-level filesystem to
|
|
* mark the whole page dirty if it was
|
|
* dirty in a pagetable. Only to then
|
|
* (c) clean the page again and return 1 to
|
|
* cause the writeback.
|
|
*
|
|
* This way we avoid all nasty races with the
|
|
* dirty bit in multiple places and clearing
|
|
* them concurrently from different threads.
|
|
*
|
|
* Note! Normally the "set_page_dirty(page)"
|
|
* has no effect on the actual dirty bit - since
|
|
* that will already usually be set. But we
|
|
* need the side effects, and it can help us
|
|
* avoid races.
|
|
*
|
|
* We basically use the page "master dirty bit"
|
|
* as a serialization point for all the different
|
|
* threads doing their things.
|
|
*/
|
|
if (page_mkclean(page))
|
|
set_page_dirty(page);
|
|
/*
|
|
* We carefully synchronise fault handlers against
|
|
* installing a dirty pte and marking the page dirty
|
|
* at this point. We do this by having them hold the
|
|
* page lock at some point after installing their
|
|
* pte, but before marking the page dirty.
|
|
* Pages are always locked coming in here, so we get
|
|
* the desired exclusion. See mm/memory.c:do_wp_page()
|
|
* for more comments.
|
|
*/
|
|
if (TestClearPageDirty(page)) {
|
|
dec_zone_page_state(page, NR_FILE_DIRTY);
|
|
dec_bdi_stat(mapping->backing_dev_info,
|
|
BDI_RECLAIMABLE);
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
return TestClearPageDirty(page);
|
|
}
|
|
EXPORT_SYMBOL(clear_page_dirty_for_io);
|
|
|
|
int test_clear_page_writeback(struct page *page)
|
|
{
|
|
struct address_space *mapping = page_mapping(page);
|
|
int ret;
|
|
|
|
if (mapping) {
|
|
struct backing_dev_info *bdi = mapping->backing_dev_info;
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&mapping->tree_lock, flags);
|
|
ret = TestClearPageWriteback(page);
|
|
if (ret) {
|
|
radix_tree_tag_clear(&mapping->page_tree,
|
|
page_index(page),
|
|
PAGECACHE_TAG_WRITEBACK);
|
|
if (bdi_cap_account_writeback(bdi)) {
|
|
__dec_bdi_stat(bdi, BDI_WRITEBACK);
|
|
__bdi_writeout_inc(bdi);
|
|
}
|
|
}
|
|
spin_unlock_irqrestore(&mapping->tree_lock, flags);
|
|
} else {
|
|
ret = TestClearPageWriteback(page);
|
|
}
|
|
if (ret) {
|
|
dec_zone_page_state(page, NR_WRITEBACK);
|
|
inc_zone_page_state(page, NR_WRITTEN);
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
int test_set_page_writeback(struct page *page)
|
|
{
|
|
struct address_space *mapping = page_mapping(page);
|
|
int ret;
|
|
|
|
if (mapping) {
|
|
struct backing_dev_info *bdi = mapping->backing_dev_info;
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&mapping->tree_lock, flags);
|
|
ret = TestSetPageWriteback(page);
|
|
if (!ret) {
|
|
radix_tree_tag_set(&mapping->page_tree,
|
|
page_index(page),
|
|
PAGECACHE_TAG_WRITEBACK);
|
|
if (bdi_cap_account_writeback(bdi))
|
|
__inc_bdi_stat(bdi, BDI_WRITEBACK);
|
|
}
|
|
if (!PageDirty(page))
|
|
radix_tree_tag_clear(&mapping->page_tree,
|
|
page_index(page),
|
|
PAGECACHE_TAG_DIRTY);
|
|
radix_tree_tag_clear(&mapping->page_tree,
|
|
page_index(page),
|
|
PAGECACHE_TAG_TOWRITE);
|
|
spin_unlock_irqrestore(&mapping->tree_lock, flags);
|
|
} else {
|
|
ret = TestSetPageWriteback(page);
|
|
}
|
|
if (!ret)
|
|
account_page_writeback(page);
|
|
return ret;
|
|
|
|
}
|
|
EXPORT_SYMBOL(test_set_page_writeback);
|
|
|
|
/*
|
|
* Return true if any of the pages in the mapping are marked with the
|
|
* passed tag.
|
|
*/
|
|
int mapping_tagged(struct address_space *mapping, int tag)
|
|
{
|
|
return radix_tree_tagged(&mapping->page_tree, tag);
|
|
}
|
|
EXPORT_SYMBOL(mapping_tagged);
|