* 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 akpm@zip.com.au
+ * 10Apr2002 Andrew Morton
* Initial version
*/
#include <linux/pagevec.h>
/*
- * The maximum number of pages to writeout in a single bdflush/kupdate
- * operation. We do this so we don't hold I_LOCK against an inode for
- * enormous amounts of time, which would block a userspace task which has
- * been forced to throttle against that inode. Also, the code reevaluates
- * the dirty each time it has written this many pages.
- */
-#define MAX_WRITEBACK_PAGES 1024
-
-/*
* 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;
-static int dirty_exceeded __cacheline_aligned_in_smp; /* Dirty mem may be over limit */
-
/*
* When balance_dirty_pages decides that the caller needs to perform some
* non-background writeback, this is how many pages it will attempt to write.
- * It should be somewhat larger than RATELIMIT_PAGES to ensure that reasonably
+ * It should be somewhat larger than dirtied pages to ensure that reasonably
* large amounts of I/O are submitted.
*/
-static inline long sync_writeback_pages(void)
+static inline long sync_writeback_pages(unsigned long dirtied)
{
- return ratelimit_pages + ratelimit_pages / 2;
+ if (dirtied < ratelimit_pages)
+ dirtied = ratelimit_pages;
+
+ return dirtied + dirtied / 2;
}
/* The following parameters are exported via /proc/sys/vm */
/*
- * Start background writeback (via pdflush) at this percentage
+ * Start background writeback (via writeback threads) at this percentage
*/
-int dirty_background_ratio = 5;
+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 = 10;
+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, in jiffies
+ * The interval between `kupdate'-style writebacks
*/
-int dirty_writeback_interval = 5 * HZ;
+unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */
/*
- * The longest number of jiffies for which data is allowed to remain dirty
+ * The longest time for which data is allowed to remain dirty
*/
-int dirty_expire_interval = 30 * HZ;
+unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */
/*
* Flag that makes the machine dump writes/reads and block dirtyings.
/* End of sysctl-exported parameters */
-static void background_writeout(unsigned long _min_pages);
+/*
+ * Scale the writeback cache size proportional to the relative writeout speeds.
+ *
+ * We do this by keeping a floating proportion between BDIs, based on page
+ * writeback completions [end_page_writeback()]. Those devices that write out
+ * pages fastest will get the larger share, while the slower will get a smaller
+ * share.
+ *
+ * We use page writeout completions because we are interested in getting rid of
+ * dirty pages. Having them written out is the primary goal.
+ *
+ * We introduce a concept of time, a period over which we measure these events,
+ * because demand can/will vary over time. The length of this period itself is
+ * measured in page writeback completions.
+ *
+ */
+static struct prop_descriptor vm_completions;
+static struct prop_descriptor vm_dirties;
+
+/*
+ * couple the period to the dirty_ratio:
+ *
+ * period/2 ~ roundup_pow_of_two(dirty limit)
+ */
+static int calc_period_shift(void)
+{
+ unsigned long dirty_total;
+
+ if (vm_dirty_bytes)
+ dirty_total = vm_dirty_bytes / PAGE_SIZE;
+ else
+ dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) /
+ 100;
+ return 2 + ilog2(dirty_total - 1);
+}
+
+/*
+ * update the period when the dirty threshold changes.
+ */
+static void update_completion_period(void)
+{
+ int shift = calc_period_shift();
+ prop_change_shift(&vm_completions, shift);
+ prop_change_shift(&vm_dirties, shift);
+}
+
+int dirty_background_ratio_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos)
+{
+ int ret;
+
+ ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+ if (ret == 0 && write)
+ dirty_background_bytes = 0;
+ return ret;
+}
+
+int dirty_background_bytes_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos)
+{
+ int ret;
+
+ ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
+ if (ret == 0 && write)
+ dirty_background_ratio = 0;
+ return ret;
+}
+
+int dirty_ratio_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos)
+{
+ int old_ratio = vm_dirty_ratio;
+ int ret;
+
+ ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+ if (ret == 0 && write && vm_dirty_ratio != old_ratio) {
+ update_completion_period();
+ vm_dirty_bytes = 0;
+ }
+ return ret;
+}
+
+
+int dirty_bytes_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos)
+{
+ unsigned long old_bytes = vm_dirty_bytes;
+ int ret;
+
+ ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
+ if (ret == 0 && write && vm_dirty_bytes != old_bytes) {
+ update_completion_period();
+ vm_dirty_ratio = 0;
+ }
+ return ret;
+}
+
+/*
+ * Increment the BDI's writeout completion count and the global writeout
+ * completion count. Called from test_clear_page_writeback().
+ */
+static inline void __bdi_writeout_inc(struct backing_dev_info *bdi)
+{
+ __prop_inc_percpu_max(&vm_completions, &bdi->completions,
+ bdi->max_prop_frac);
+}
+
+void bdi_writeout_inc(struct backing_dev_info *bdi)
+{
+ unsigned long flags;
+
+ local_irq_save(flags);
+ __bdi_writeout_inc(bdi);
+ local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(bdi_writeout_inc);
+
+void task_dirty_inc(struct task_struct *tsk)
+{
+ prop_inc_single(&vm_dirties, &tsk->dirties);
+}
+
+/*
+ * Obtain an accurate fraction of the BDI's portion.
+ */
+static void bdi_writeout_fraction(struct backing_dev_info *bdi,
+ long *numerator, long *denominator)
+{
+ if (bdi_cap_writeback_dirty(bdi)) {
+ prop_fraction_percpu(&vm_completions, &bdi->completions,
+ numerator, denominator);
+ } else {
+ *numerator = 0;
+ *denominator = 1;
+ }
+}
+
+/*
+ * Clip the earned share of dirty pages to that which is actually available.
+ * This avoids exceeding the total dirty_limit when the floating averages
+ * fluctuate too quickly.
+ */
+static void clip_bdi_dirty_limit(struct backing_dev_info *bdi,
+ unsigned long dirty, unsigned long *pbdi_dirty)
+{
+ unsigned long avail_dirty;
+
+ avail_dirty = global_page_state(NR_FILE_DIRTY) +
+ global_page_state(NR_WRITEBACK) +
+ global_page_state(NR_UNSTABLE_NFS) +
+ global_page_state(NR_WRITEBACK_TEMP);
+
+ if (avail_dirty < dirty)
+ avail_dirty = dirty - avail_dirty;
+ else
+ avail_dirty = 0;
+
+ avail_dirty += bdi_stat(bdi, BDI_RECLAIMABLE) +
+ bdi_stat(bdi, BDI_WRITEBACK);
+
+ *pbdi_dirty = min(*pbdi_dirty, avail_dirty);
+}
+
+static inline void task_dirties_fraction(struct task_struct *tsk,
+ long *numerator, long *denominator)
+{
+ prop_fraction_single(&vm_dirties, &tsk->dirties,
+ numerator, denominator);
+}
+
+/*
+ * scale the dirty limit
+ *
+ * task specific dirty limit:
+ *
+ * dirty -= (dirty/8) * p_{t}
+ */
+static void task_dirty_limit(struct task_struct *tsk, unsigned long *pdirty)
+{
+ long numerator, denominator;
+ unsigned long dirty = *pdirty;
+ u64 inv = dirty >> 3;
+
+ task_dirties_fraction(tsk, &numerator, &denominator);
+ inv *= numerator;
+ do_div(inv, denominator);
+
+ dirty -= inv;
+ if (dirty < *pdirty/2)
+ dirty = *pdirty/2;
+
+ *pdirty = dirty;
+}
+
+/*
+ *
+ */
+static unsigned int bdi_min_ratio;
+
+int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
+{
+ int ret = 0;
+
+ spin_lock_bh(&bdi_lock);
+ if (min_ratio > bdi->max_ratio) {
+ ret = -EINVAL;
+ } else {
+ min_ratio -= bdi->min_ratio;
+ if (bdi_min_ratio + min_ratio < 100) {
+ bdi_min_ratio += min_ratio;
+ bdi->min_ratio += min_ratio;
+ } else {
+ ret = -EINVAL;
+ }
+ }
+ spin_unlock_bh(&bdi_lock);
+
+ return ret;
+}
+
+int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio)
+{
+ int ret = 0;
+
+ if (max_ratio > 100)
+ return -EINVAL;
+
+ spin_lock_bh(&bdi_lock);
+ if (bdi->min_ratio > max_ratio) {
+ ret = -EINVAL;
+ } else {
+ bdi->max_ratio = max_ratio;
+ bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100;
+ }
+ spin_unlock_bh(&bdi_lock);
+
+ return ret;
+}
+EXPORT_SYMBOL(bdi_set_max_ratio);
/*
* Work out the current dirty-memory clamping and background writeout
int node;
unsigned long x = 0;
- for_each_online_node(node) {
+ 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_page_state(z, NR_INACTIVE)
- + zone_page_state(z, NR_ACTIVE);
+ x += zone_page_state(z, NR_FREE_PAGES) +
+ zone_reclaimable_pages(z);
}
/*
* Make sure that the number of highmem pages is never larger
#endif
}
-static unsigned long determine_dirtyable_memory(void)
+/**
+ * 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_page_state(NR_INACTIVE)
- + global_page_state(NR_ACTIVE);
- x -= highmem_dirtyable_memory(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 void
-get_dirty_limits(long *pbackground, long *pdirty,
- struct address_space *mapping)
+void
+get_dirty_limits(unsigned long *pbackground, unsigned long *pdirty,
+ unsigned long *pbdi_dirty, struct backing_dev_info *bdi)
{
- int background_ratio; /* Percentages */
- int dirty_ratio;
- int unmapped_ratio;
- long background;
- long dirty;
+ unsigned long background;
+ unsigned long dirty;
unsigned long available_memory = determine_dirtyable_memory();
struct task_struct *tsk;
- unmapped_ratio = 100 - ((global_page_state(NR_FILE_MAPPED) +
- global_page_state(NR_ANON_PAGES)) * 100) /
- available_memory;
-
- dirty_ratio = vm_dirty_ratio;
- if (dirty_ratio > unmapped_ratio / 2)
- dirty_ratio = unmapped_ratio / 2;
+ if (vm_dirty_bytes)
+ dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
+ else {
+ int dirty_ratio;
- if (dirty_ratio < 5)
- dirty_ratio = 5;
+ dirty_ratio = vm_dirty_ratio;
+ if (dirty_ratio < 5)
+ dirty_ratio = 5;
+ dirty = (dirty_ratio * available_memory) / 100;
+ }
- background_ratio = dirty_background_ratio;
- if (background_ratio >= dirty_ratio)
- background_ratio = dirty_ratio / 2;
+ if (dirty_background_bytes)
+ background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
+ else
+ background = (dirty_background_ratio * available_memory) / 100;
- background = (background_ratio * available_memory) / 100;
- dirty = (dirty_ratio * available_memory) / 100;
+ if (background >= dirty)
+ background = dirty / 2;
tsk = current;
if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
background += background / 4;
}
*pbackground = background;
*pdirty = dirty;
+
+ if (bdi) {
+ u64 bdi_dirty;
+ long numerator, denominator;
+
+ /*
+ * Calculate this BDI's share of the dirty ratio.
+ */
+ bdi_writeout_fraction(bdi, &numerator, &denominator);
+
+ bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
+ bdi_dirty *= numerator;
+ do_div(bdi_dirty, denominator);
+ bdi_dirty += (dirty * bdi->min_ratio) / 100;
+ if (bdi_dirty > (dirty * bdi->max_ratio) / 100)
+ bdi_dirty = dirty * bdi->max_ratio / 100;
+
+ *pbdi_dirty = bdi_dirty;
+ clip_bdi_dirty_limit(bdi, dirty, pbdi_dirty);
+ task_dirty_limit(current, pbdi_dirty);
+ }
}
/*
* balance_dirty_pages() must be called by processes which are generating dirty
* data. It looks at the number of dirty pages in the machine and will force
* the caller to perform writeback if the system is over `vm_dirty_ratio'.
- * If we're over `background_thresh' then pdflush is woken to perform some
- * writeout.
+ * 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)
+static void balance_dirty_pages(struct address_space *mapping,
+ unsigned long write_chunk)
{
- long nr_reclaimable;
- long background_thresh;
- long dirty_thresh;
+ long nr_reclaimable, bdi_nr_reclaimable;
+ long nr_writeback, bdi_nr_writeback;
+ unsigned long background_thresh;
+ unsigned long dirty_thresh;
+ unsigned long bdi_thresh;
unsigned long pages_written = 0;
- unsigned long write_chunk = sync_writeback_pages();
+ unsigned long pause = 1;
struct backing_dev_info *bdi = mapping->backing_dev_info;
.range_cyclic = 1,
};
- get_dirty_limits(&background_thresh, &dirty_thresh, mapping);
+ get_dirty_limits(&background_thresh, &dirty_thresh,
+ &bdi_thresh, bdi);
+
nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS);
- if (nr_reclaimable + global_page_state(NR_WRITEBACK) <=
- dirty_thresh)
- break;
+ nr_writeback = global_page_state(NR_WRITEBACK);
- if (!dirty_exceeded)
- dirty_exceeded = 1;
+ bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
+ bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
+
+ if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh)
+ break;
+
+ /*
+ * Throttle it only when the background writeback cannot
+ * catch-up. This avoids (excessively) small writeouts
+ * when the bdi limits are ramping up.
+ */
+ if (nr_reclaimable + nr_writeback <
+ (background_thresh + dirty_thresh) / 2)
+ break;
+
+ if (!bdi->dirty_exceeded)
+ bdi->dirty_exceeded = 1;
/* Note: nr_reclaimable denotes nr_dirty + nr_unstable.
* Unstable writes are a feature of certain networked
* filesystems (i.e. NFS) in which data may have been
* written to the server's write cache, but has not yet
* been flushed to permanent storage.
+ * Only move pages to writeback if this bdi is over its
+ * threshold otherwise wait until the disk writes catch
+ * up.
*/
- if (nr_reclaimable) {
- writeback_inodes(&wbc);
- get_dirty_limits(&background_thresh,
- &dirty_thresh, mapping);
- nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
- global_page_state(NR_UNSTABLE_NFS);
- if (nr_reclaimable +
- global_page_state(NR_WRITEBACK)
- <= dirty_thresh)
- break;
+ if (bdi_nr_reclaimable > bdi_thresh) {
+ writeback_inodes_wbc(&wbc);
pages_written += write_chunk - wbc.nr_to_write;
- if (pages_written >= write_chunk)
- break; /* We've done our duty */
+ get_dirty_limits(&background_thresh, &dirty_thresh,
+ &bdi_thresh, bdi);
}
- congestion_wait(WRITE, HZ/10);
+
+ /*
+ * In order to avoid the stacked BDI deadlock we need
+ * to ensure we accurately count the 'dirty' pages when
+ * the threshold is low.
+ *
+ * Otherwise it would be possible to get thresh+n pages
+ * reported dirty, even though there are thresh-m pages
+ * actually dirty; with m+n sitting in the percpu
+ * deltas.
+ */
+ if (bdi_thresh < 2*bdi_stat_error(bdi)) {
+ bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE);
+ bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK);
+ } else if (bdi_nr_reclaimable) {
+ bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
+ bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
+ }
+
+ if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh)
+ break;
+ if (pages_written >= write_chunk)
+ break; /* We've done our duty */
+
+ __set_current_state(TASK_INTERRUPTIBLE);
+ io_schedule_timeout(pause);
+
+ /*
+ * Increase the delay for each loop, up to our previous
+ * default of taking a 100ms nap.
+ */
+ pause <<= 1;
+ if (pause > HZ / 10)
+ pause = HZ / 10;
}
- if (nr_reclaimable + global_page_state(NR_WRITEBACK)
- <= dirty_thresh && dirty_exceeded)
- dirty_exceeded = 0;
+ if (bdi_nr_reclaimable + bdi_nr_writeback < bdi_thresh &&
+ bdi->dirty_exceeded)
+ bdi->dirty_exceeded = 0;
if (writeback_in_progress(bdi))
- return; /* pdflush is already working this queue */
+ return;
/*
* In laptop mode, we wait until hitting the higher threshold before
* background_thresh, to keep the amount of dirty memory low.
*/
if ((laptop_mode && pages_written) ||
- (!laptop_mode && (nr_reclaimable > background_thresh)))
- pdflush_operation(background_writeout, 0);
+ (!laptop_mode && ((global_page_state(NR_FILE_DIRTY)
+ + global_page_state(NR_UNSTABLE_NFS))
+ > background_thresh)))
+ bdi_start_writeback(bdi, NULL, 0);
}
void set_page_dirty_balance(struct page *page, int page_mkwrite)
}
}
+static DEFINE_PER_CPU(unsigned long, bdp_ratelimits) = 0;
+
/**
* balance_dirty_pages_ratelimited_nr - balance dirty memory state
* @mapping: address_space which was dirtied
void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
unsigned long nr_pages_dirtied)
{
- static DEFINE_PER_CPU(unsigned long, ratelimits) = 0;
unsigned long ratelimit;
unsigned long *p;
ratelimit = ratelimit_pages;
- if (dirty_exceeded)
+ if (mapping->backing_dev_info->dirty_exceeded)
ratelimit = 8;
/*
* tasks in balance_dirty_pages(). Period.
*/
preempt_disable();
- p = &__get_cpu_var(ratelimits);
+ p = &__get_cpu_var(bdp_ratelimits);
*p += nr_pages_dirtied;
if (unlikely(*p >= ratelimit)) {
+ ratelimit = sync_writeback_pages(*p);
*p = 0;
preempt_enable();
- balance_dirty_pages(mapping);
+ balance_dirty_pages(mapping, ratelimit);
return;
}
preempt_enable();
void throttle_vm_writeout(gfp_t gfp_mask)
{
- long background_thresh;
- long dirty_thresh;
-
- if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) {
- /*
- * 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.
- */
- congestion_wait(WRITE, HZ/10);
- return;
- }
+ unsigned long background_thresh;
+ unsigned long dirty_thresh;
for ( ; ; ) {
- get_dirty_limits(&background_thresh, &dirty_thresh, NULL);
+ get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL);
/*
* Boost the allowable dirty threshold a bit for page
if (global_page_state(NR_UNSTABLE_NFS) +
global_page_state(NR_WRITEBACK) <= dirty_thresh)
break;
- congestion_wait(WRITE, HZ/10);
- }
-}
+ congestion_wait(BLK_RW_ASYNC, HZ/10);
-/*
- * writeback at least _min_pages, and keep writing until the amount of dirty
- * memory is less than the background threshold, or until we're all clean.
- */
-static void background_writeout(unsigned long _min_pages)
-{
- long min_pages = _min_pages;
- struct writeback_control wbc = {
- .bdi = NULL,
- .sync_mode = WB_SYNC_NONE,
- .older_than_this = NULL,
- .nr_to_write = 0,
- .nonblocking = 1,
- .range_cyclic = 1,
- };
-
- for ( ; ; ) {
- long background_thresh;
- long dirty_thresh;
-
- get_dirty_limits(&background_thresh, &dirty_thresh, NULL);
- if (global_page_state(NR_FILE_DIRTY) +
- global_page_state(NR_UNSTABLE_NFS) < background_thresh
- && min_pages <= 0)
+ /*
+ * 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;
- wbc.encountered_congestion = 0;
- wbc.nr_to_write = MAX_WRITEBACK_PAGES;
- wbc.pages_skipped = 0;
- writeback_inodes(&wbc);
- min_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
- if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) {
- /* Wrote less than expected */
- congestion_wait(WRITE, HZ/10);
- if (!wbc.encountered_congestion)
- break;
- }
- }
-}
-
-/*
- * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
- * the whole world. Returns 0 if a pdflush thread was dispatched. Returns
- * -1 if all pdflush threads were busy.
- */
-int wakeup_pdflush(long nr_pages)
-{
- if (nr_pages == 0)
- nr_pages = global_page_state(NR_FILE_DIRTY) +
- global_page_state(NR_UNSTABLE_NFS);
- return pdflush_operation(background_writeout, nr_pages);
-}
-
-static void wb_timer_fn(unsigned long unused);
-static void laptop_timer_fn(unsigned long unused);
-
-static DEFINE_TIMER(wb_timer, wb_timer_fn, 0, 0);
-static DEFINE_TIMER(laptop_mode_wb_timer, laptop_timer_fn, 0, 0);
-
-/*
- * Periodic writeback of "old" data.
- *
- * Define "old": the first time one of an inode's pages is dirtied, we mark the
- * dirtying-time in the inode's address_space. So this periodic writeback code
- * just walks the superblock inode list, writing back any inodes which are
- * older than a specific point in time.
- *
- * Try to run once per dirty_writeback_interval. But if a writeback event
- * takes longer than a dirty_writeback_interval interval, then leave a
- * one-second gap.
- *
- * older_than_this takes precedence over nr_to_write. So we'll only write back
- * all dirty pages if they are all attached to "old" mappings.
- */
-static void wb_kupdate(unsigned long arg)
-{
- unsigned long oldest_jif;
- unsigned long start_jif;
- unsigned long next_jif;
- long nr_to_write;
- struct writeback_control wbc = {
- .bdi = NULL,
- .sync_mode = WB_SYNC_NONE,
- .older_than_this = &oldest_jif,
- .nr_to_write = 0,
- .nonblocking = 1,
- .for_kupdate = 1,
- .range_cyclic = 1,
- };
-
- sync_supers();
-
- oldest_jif = jiffies - dirty_expire_interval;
- start_jif = jiffies;
- next_jif = start_jif + dirty_writeback_interval;
- nr_to_write = global_page_state(NR_FILE_DIRTY) +
- global_page_state(NR_UNSTABLE_NFS) +
- (inodes_stat.nr_inodes - inodes_stat.nr_unused);
- while (nr_to_write > 0) {
- wbc.encountered_congestion = 0;
- wbc.nr_to_write = MAX_WRITEBACK_PAGES;
- writeback_inodes(&wbc);
- if (wbc.nr_to_write > 0) {
- if (wbc.encountered_congestion)
- congestion_wait(WRITE, HZ/10);
- else
- break; /* All the old data is written */
- }
- nr_to_write -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
- }
- if (time_before(next_jif, jiffies + HZ))
- next_jif = jiffies + HZ;
- if (dirty_writeback_interval)
- mod_timer(&wb_timer, next_jif);
+ }
}
/*
* sysctl handler for /proc/sys/vm/dirty_writeback_centisecs
*/
int dirty_writeback_centisecs_handler(ctl_table *table, int write,
- struct file *file, void __user *buffer, size_t *length, loff_t *ppos)
+ void __user *buffer, size_t *length, loff_t *ppos)
{
- proc_dointvec_userhz_jiffies(table, write, file, buffer, length, ppos);
- if (dirty_writeback_interval)
- mod_timer(&wb_timer, jiffies + dirty_writeback_interval);
- else
- del_timer(&wb_timer);
+ proc_dointvec(table, write, buffer, length, ppos);
+ bdi_arm_supers_timer();
return 0;
}
-static void wb_timer_fn(unsigned long unused)
+#ifdef CONFIG_BLOCK
+void laptop_mode_timer_fn(unsigned long data)
{
- if (pdflush_operation(wb_kupdate, 0) < 0)
- mod_timer(&wb_timer, jiffies + HZ); /* delay 1 second */
-}
+ struct request_queue *q = (struct request_queue *)data;
+ int nr_pages = global_page_state(NR_FILE_DIRTY) +
+ global_page_state(NR_UNSTABLE_NFS);
-static void laptop_flush(unsigned long unused)
-{
- sys_sync();
-}
+ /*
+ * We want to write everything out, not just down to the dirty
+ * threshold
+ */
-static void laptop_timer_fn(unsigned long unused)
-{
- pdflush_operation(laptop_flush, 0);
+ if (bdi_has_dirty_io(&q->backing_dev_info))
+ bdi_start_writeback(&q->backing_dev_info, NULL, nr_pages);
}
/*
* 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(void)
+void laptop_io_completion(struct backing_dev_info *info)
{
- mod_timer(&laptop_mode_wb_timer, jiffies + laptop_mode);
+ mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode);
}
/*
*/
void laptop_sync_completion(void)
{
- del_timer(&laptop_mode_wb_timer);
+ 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
*/
void __init page_writeback_init(void)
{
- mod_timer(&wb_timer, jiffies + dirty_writeback_interval);
+ 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);
}
/**
struct writeback_control *wbc, writepage_t writepage,
void *data)
{
- struct backing_dev_info *bdi = mapping->backing_dev_info;
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 */
- int scanned = 0;
+ pgoff_t done_index;
+ int cycled;
int range_whole = 0;
- if (wbc->nonblocking && bdi_write_congested(bdi)) {
- wbc->encountered_congestion = 1;
- return 0;
- }
-
pagevec_init(&pvec, 0);
if (wbc->range_cyclic) {
- index = mapping->writeback_index; /* Start from prev offset */
+ 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;
- scanned = 1;
+ cycled = 1; /* ignore range_cyclic tests */
+
+ /*
+ * If this is a data integrity sync, cap the writeback to the
+ * current end of file. Any extension to the file that occurs
+ * after this is a new write and we don't need to write those
+ * pages out to fulfil our data integrity requirements. If we
+ * try to write them out, we can get stuck in this scan until
+ * the concurrent writer stops adding dirty pages and extending
+ * EOF.
+ */
+ if (wbc->sync_mode == WB_SYNC_ALL &&
+ wbc->range_end == LLONG_MAX) {
+ end = i_size_read(mapping->host) >> PAGE_CACHE_SHIFT;
+ }
}
+
retry:
- while (!done && (index <= end) &&
- (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
- PAGECACHE_TAG_DIRTY,
- min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
- unsigned i;
+ done_index = index;
+ while (!done && (index <= end)) {
+ int i;
+
+ nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
+ PAGECACHE_TAG_DIRTY,
+ min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1);
+ if (nr_pages == 0)
+ break;
- scanned = 1;
for (i = 0; i < nr_pages; i++) {
struct page *page = pvec.pages[i];
/*
- * At this point we hold neither mapping->tree_lock nor
- * lock on the page itself: the page may be truncated or
- * invalidated (changing page->mapping to NULL), or even
- * swizzled back from swapper_space to tmpfs file
- * mapping
+ * At this point, the page may be truncated or
+ * invalidated (changing page->mapping to NULL), or
+ * even swizzled back from swapper_space to tmpfs file
+ * mapping. However, page->index will not change
+ * because we have a reference on the page.
*/
+ if (page->index > end) {
+ /*
+ * can't be range_cyclic (1st pass) because
+ * end == -1 in that case.
+ */
+ done = 1;
+ break;
+ }
+
+ done_index = page->index + 1;
+
lock_page(page);
+ /*
+ * Page truncated or invalidated. We can freely skip it
+ * then, even for data integrity operations: the page
+ * has disappeared concurrently, so there could be no
+ * real expectation of this data interity operation
+ * even if there is now a new, dirty page at the same
+ * pagecache address.
+ */
if (unlikely(page->mapping != mapping)) {
+continue_unlock:
unlock_page(page);
continue;
}
- if (!wbc->range_cyclic && page->index > end) {
- done = 1;
- unlock_page(page);
- continue;
+ if (!PageDirty(page)) {
+ /* someone wrote it for us */
+ goto continue_unlock;
}
- if (wbc->sync_mode != WB_SYNC_NONE)
- wait_on_page_writeback(page);
-
- if (PageWriteback(page) ||
- !clear_page_dirty_for_io(page)) {
- unlock_page(page);
- continue;
+ 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;
+
ret = (*writepage)(page, wbc, data);
+ if (unlikely(ret)) {
+ if (ret == AOP_WRITEPAGE_ACTIVATE) {
+ unlock_page(page);
+ ret = 0;
+ } else {
+ /*
+ * done_index is set past this page,
+ * so media errors will not choke
+ * background writeout for the entire
+ * file. This has consequences for
+ * range_cyclic semantics (ie. it may
+ * not be suitable for data integrity
+ * writeout).
+ */
+ done = 1;
+ break;
+ }
+ }
- if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE))
- unlock_page(page);
- if (ret || (--(wbc->nr_to_write) <= 0))
- done = 1;
- if (wbc->nonblocking && bdi_write_congested(bdi)) {
- wbc->encountered_congestion = 1;
- done = 1;
+ if (wbc->nr_to_write > 0) {
+ if (--wbc->nr_to_write == 0 &&
+ wbc->sync_mode == WB_SYNC_NONE) {
+ /*
+ * We stop writing back only if we are
+ * not doing integrity sync. In case of
+ * integrity sync we have to keep going
+ * because someone may be concurrently
+ * dirtying pages, and we might have
+ * synced a lot of newly appeared dirty
+ * pages, but have not synced all of the
+ * old dirty pages.
+ */
+ done = 1;
+ break;
+ }
}
}
pagevec_release(&pvec);
cond_resched();
}
- if (!scanned && !done) {
+ 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
*/
- scanned = 1;
+ cycled = 1;
index = 0;
+ end = writeback_index - 1;
goto retry;
}
if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
- mapping->writeback_index = index;
+ mapping->writeback_index = done_index;
+
return ret;
}
EXPORT_SYMBOL(write_cache_pages);
if (wbc->nr_to_write <= 0)
return 0;
- wbc->for_writepages = 1;
if (mapping->a_ops->writepages)
ret = mapping->a_ops->writepages(mapping, wbc);
else
ret = generic_writepages(mapping, wbc);
- wbc->for_writepages = 0;
return ret;
}
}
/*
+ * Helper function for set_page_dirty family.
+ * NOTE: This relies on being atomic wrt interrupts.
+ */
+void account_page_dirtied(struct page *page, struct address_space *mapping)
+{
+ if (mapping_cap_account_dirty(mapping)) {
+ __inc_zone_page_state(page, NR_FILE_DIRTY);
+ __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
+ task_dirty_inc(current);
+ task_io_account_write(PAGE_CACHE_SIZE);
+ }
+}
+
+/*
* For address_spaces which do not use buffers. Just tag the page as dirty in
* its radix tree.
*
* 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() insode tree_lock.
+ * mapping by re-checking page_mapping() inside tree_lock.
*/
int __set_page_dirty_nobuffers(struct page *page)
{
if (!mapping)
return 1;
- write_lock_irq(&mapping->tree_lock);
+ 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));
- if (mapping_cap_account_dirty(mapping)) {
- __inc_zone_page_state(page, NR_FILE_DIRTY);
- task_io_account_write(PAGE_CACHE_SIZE);
- }
+ account_page_dirtied(page, mapping);
radix_tree_tag_set(&mapping->page_tree,
page_index(page), PAGECACHE_TAG_DIRTY);
}
- write_unlock_irq(&mapping->tree_lock);
+ spin_unlock_irq(&mapping->tree_lock);
if (mapping->host) {
/* !PageAnon && !swapper_space */
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
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 fastcall set_page_dirty(struct page *page)
+int set_page_dirty(struct page *page)
{
struct address_space *mapping = page_mapping(page);
*/
if (TestClearPageDirty(page)) {
dec_zone_page_state(page, NR_FILE_DIRTY);
+ dec_bdi_stat(mapping->backing_dev_info,
+ BDI_RECLAIMABLE);
return 1;
}
return 0;
int ret;
if (mapping) {
+ struct backing_dev_info *bdi = mapping->backing_dev_info;
unsigned long flags;
- write_lock_irqsave(&mapping->tree_lock, flags);
+ spin_lock_irqsave(&mapping->tree_lock, flags);
ret = TestClearPageWriteback(page);
- if (ret)
+ if (ret) {
radix_tree_tag_clear(&mapping->page_tree,
page_index(page),
PAGECACHE_TAG_WRITEBACK);
- write_unlock_irqrestore(&mapping->tree_lock, flags);
+ 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);
}
int ret;
if (mapping) {
+ struct backing_dev_info *bdi = mapping->backing_dev_info;
unsigned long flags;
- write_lock_irqsave(&mapping->tree_lock, flags);
+ spin_lock_irqsave(&mapping->tree_lock, flags);
ret = TestSetPageWriteback(page);
- if (!ret)
+ 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);
- write_unlock_irqrestore(&mapping->tree_lock, flags);
+ spin_unlock_irqrestore(&mapping->tree_lock, flags);
} else {
ret = TestSetPageWriteback(page);
}
EXPORT_SYMBOL(test_set_page_writeback);
/*
- * Return true if any of the pages in the mapping are marged with the
+ * 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)
{
- unsigned long flags;
int ret;
-
- read_lock_irqsave(&mapping->tree_lock, flags);
+ rcu_read_lock();
ret = radix_tree_tagged(&mapping->page_tree, tag);
- read_unlock_irqrestore(&mapping->tree_lock, flags);
+ rcu_read_unlock();
return ret;
}
EXPORT_SYMBOL(mapping_tagged);
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff