1babe18385
Document global_dirty_limits() and bdi_dirty_limit(). Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Dave Chinner <david@fromorbit.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1391 lines
39 KiB
C
1391 lines
39 KiB
C
/*
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* mm/page-writeback.c
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*
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* Copyright (C) 2002, Linus Torvalds.
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* Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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*
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* Contains functions related to writing back dirty pages at the
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* address_space level.
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*
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* 10Apr2002 Andrew Morton
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* Initial version
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/spinlock.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/swap.h>
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#include <linux/slab.h>
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#include <linux/pagemap.h>
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#include <linux/writeback.h>
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#include <linux/init.h>
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#include <linux/backing-dev.h>
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#include <linux/task_io_accounting_ops.h>
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#include <linux/blkdev.h>
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#include <linux/mpage.h>
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#include <linux/rmap.h>
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#include <linux/percpu.h>
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#include <linux/notifier.h>
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#include <linux/smp.h>
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#include <linux/sysctl.h>
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#include <linux/cpu.h>
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#include <linux/syscalls.h>
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#include <linux/buffer_head.h>
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#include <linux/pagevec.h>
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#include <trace/events/writeback.h>
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/*
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* After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited
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* will look to see if it needs to force writeback or throttling.
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*/
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static long ratelimit_pages = 32;
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/*
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* When balance_dirty_pages decides that the caller needs to perform some
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* non-background writeback, this is how many pages it will attempt to write.
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* It should be somewhat larger than dirtied pages to ensure that reasonably
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* large amounts of I/O are submitted.
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*/
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static inline long sync_writeback_pages(unsigned long dirtied)
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{
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if (dirtied < ratelimit_pages)
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dirtied = ratelimit_pages;
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return dirtied + dirtied / 2;
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}
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/* The following parameters are exported via /proc/sys/vm */
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/*
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* Start background writeback (via writeback threads) at this percentage
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*/
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int dirty_background_ratio = 10;
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/*
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* dirty_background_bytes starts at 0 (disabled) so that it is a function of
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* dirty_background_ratio * the amount of dirtyable memory
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*/
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unsigned long dirty_background_bytes;
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/*
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* free highmem will not be subtracted from the total free memory
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* for calculating free ratios if vm_highmem_is_dirtyable is true
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*/
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int vm_highmem_is_dirtyable;
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/*
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* The generator of dirty data starts writeback at this percentage
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*/
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int vm_dirty_ratio = 20;
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/*
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* vm_dirty_bytes starts at 0 (disabled) so that it is a function of
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* vm_dirty_ratio * the amount of dirtyable memory
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*/
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unsigned long vm_dirty_bytes;
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/*
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* The interval between `kupdate'-style writebacks
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*/
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unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */
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/*
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* The longest time for which data is allowed to remain dirty
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*/
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unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */
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/*
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* Flag that makes the machine dump writes/reads and block dirtyings.
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*/
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int block_dump;
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/*
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* Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies:
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* a full sync is triggered after this time elapses without any disk activity.
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*/
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int laptop_mode;
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EXPORT_SYMBOL(laptop_mode);
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/* End of sysctl-exported parameters */
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/*
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* Scale the writeback cache size proportional to the relative writeout speeds.
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*
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* We do this by keeping a floating proportion between BDIs, based on page
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* writeback completions [end_page_writeback()]. Those devices that write out
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* pages fastest will get the larger share, while the slower will get a smaller
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* share.
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*
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* We use page writeout completions because we are interested in getting rid of
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* dirty pages. Having them written out is the primary goal.
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*
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* We introduce a concept of time, a period over which we measure these events,
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* because demand can/will vary over time. The length of this period itself is
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* measured in page writeback completions.
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*
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*/
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static struct prop_descriptor vm_completions;
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static struct prop_descriptor vm_dirties;
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/*
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* couple the period to the dirty_ratio:
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*
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* period/2 ~ roundup_pow_of_two(dirty limit)
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*/
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static int calc_period_shift(void)
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{
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unsigned long dirty_total;
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if (vm_dirty_bytes)
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dirty_total = vm_dirty_bytes / PAGE_SIZE;
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else
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dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) /
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100;
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return 2 + ilog2(dirty_total - 1);
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}
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/*
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* update the period when the dirty threshold changes.
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*/
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static void update_completion_period(void)
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{
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int shift = calc_period_shift();
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prop_change_shift(&vm_completions, shift);
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prop_change_shift(&vm_dirties, shift);
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}
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int dirty_background_ratio_handler(struct ctl_table *table, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos)
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{
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int ret;
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ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
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if (ret == 0 && write)
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dirty_background_bytes = 0;
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return ret;
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}
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int dirty_background_bytes_handler(struct ctl_table *table, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos)
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{
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int ret;
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ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
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if (ret == 0 && write)
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dirty_background_ratio = 0;
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return ret;
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}
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int dirty_ratio_handler(struct ctl_table *table, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos)
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{
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int old_ratio = vm_dirty_ratio;
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int ret;
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ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
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if (ret == 0 && write && vm_dirty_ratio != old_ratio) {
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update_completion_period();
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vm_dirty_bytes = 0;
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}
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return ret;
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}
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int dirty_bytes_handler(struct ctl_table *table, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos)
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{
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unsigned long old_bytes = vm_dirty_bytes;
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int ret;
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ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
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if (ret == 0 && write && vm_dirty_bytes != old_bytes) {
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update_completion_period();
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vm_dirty_ratio = 0;
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}
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return ret;
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}
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/*
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* Increment the BDI's writeout completion count and the global writeout
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* completion count. Called from test_clear_page_writeback().
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*/
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static inline void __bdi_writeout_inc(struct backing_dev_info *bdi)
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{
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__prop_inc_percpu_max(&vm_completions, &bdi->completions,
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bdi->max_prop_frac);
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}
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void bdi_writeout_inc(struct backing_dev_info *bdi)
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{
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unsigned long flags;
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local_irq_save(flags);
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__bdi_writeout_inc(bdi);
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local_irq_restore(flags);
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}
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EXPORT_SYMBOL_GPL(bdi_writeout_inc);
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void task_dirty_inc(struct task_struct *tsk)
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{
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prop_inc_single(&vm_dirties, &tsk->dirties);
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}
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/*
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* Obtain an accurate fraction of the BDI's portion.
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*/
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static void bdi_writeout_fraction(struct backing_dev_info *bdi,
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long *numerator, long *denominator)
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{
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if (bdi_cap_writeback_dirty(bdi)) {
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prop_fraction_percpu(&vm_completions, &bdi->completions,
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numerator, denominator);
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} else {
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*numerator = 0;
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*denominator = 1;
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}
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}
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static inline void task_dirties_fraction(struct task_struct *tsk,
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long *numerator, long *denominator)
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{
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prop_fraction_single(&vm_dirties, &tsk->dirties,
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numerator, denominator);
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}
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/*
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* task_dirty_limit - scale down dirty throttling threshold for one task
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*
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* task specific dirty limit:
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*
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* dirty -= (dirty/8) * p_{t}
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*
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* To protect light/slow dirtying tasks from heavier/fast ones, we start
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* throttling individual tasks before reaching the bdi dirty limit.
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* Relatively low thresholds will be allocated to heavy dirtiers. So when
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* dirty pages grow large, heavy dirtiers will be throttled first, which will
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* effectively curb the growth of dirty pages. Light dirtiers with high enough
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* dirty threshold may never get throttled.
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*/
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static unsigned long task_dirty_limit(struct task_struct *tsk,
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unsigned long bdi_dirty)
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{
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long numerator, denominator;
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unsigned long dirty = bdi_dirty;
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u64 inv = dirty >> 3;
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task_dirties_fraction(tsk, &numerator, &denominator);
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inv *= numerator;
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do_div(inv, denominator);
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dirty -= inv;
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return max(dirty, bdi_dirty/2);
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}
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/*
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*
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*/
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static unsigned int bdi_min_ratio;
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int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
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{
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int ret = 0;
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spin_lock_bh(&bdi_lock);
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if (min_ratio > bdi->max_ratio) {
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ret = -EINVAL;
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} else {
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min_ratio -= bdi->min_ratio;
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if (bdi_min_ratio + min_ratio < 100) {
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bdi_min_ratio += min_ratio;
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bdi->min_ratio += min_ratio;
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} else {
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ret = -EINVAL;
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}
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}
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spin_unlock_bh(&bdi_lock);
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return ret;
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}
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int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio)
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{
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int ret = 0;
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if (max_ratio > 100)
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return -EINVAL;
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spin_lock_bh(&bdi_lock);
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if (bdi->min_ratio > max_ratio) {
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ret = -EINVAL;
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} else {
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bdi->max_ratio = max_ratio;
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bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100;
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}
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spin_unlock_bh(&bdi_lock);
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return ret;
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}
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EXPORT_SYMBOL(bdi_set_max_ratio);
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/*
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* Work out the current dirty-memory clamping and background writeout
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* thresholds.
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*
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* The main aim here is to lower them aggressively if there is a lot of mapped
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* memory around. To avoid stressing page reclaim with lots of unreclaimable
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* pages. It is better to clamp down on writers than to start swapping, and
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* performing lots of scanning.
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*
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* We only allow 1/2 of the currently-unmapped memory to be dirtied.
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*
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* We don't permit the clamping level to fall below 5% - that is getting rather
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* excessive.
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*
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* We make sure that the background writeout level is below the adjusted
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* clamping level.
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*/
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static unsigned long highmem_dirtyable_memory(unsigned long total)
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{
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#ifdef CONFIG_HIGHMEM
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int node;
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unsigned long x = 0;
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for_each_node_state(node, N_HIGH_MEMORY) {
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struct zone *z =
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&NODE_DATA(node)->node_zones[ZONE_HIGHMEM];
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x += zone_page_state(z, NR_FREE_PAGES) +
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zone_reclaimable_pages(z);
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}
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/*
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* Make sure that the number of highmem pages is never larger
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* than the number of the total dirtyable memory. This can only
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* occur in very strange VM situations but we want to make sure
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* that this does not occur.
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*/
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return min(x, total);
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#else
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return 0;
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#endif
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}
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/**
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* determine_dirtyable_memory - amount of memory that may be used
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*
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* Returns the numebr of pages that can currently be freed and used
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* by the kernel for direct mappings.
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*/
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unsigned long determine_dirtyable_memory(void)
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{
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unsigned long x;
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x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages();
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if (!vm_highmem_is_dirtyable)
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x -= highmem_dirtyable_memory(x);
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return x + 1; /* Ensure that we never return 0 */
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}
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/**
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* global_dirty_limits - background-writeback and dirty-throttling thresholds
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*
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* Calculate the dirty thresholds based on sysctl parameters
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* - vm.dirty_background_ratio or vm.dirty_background_bytes
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* - vm.dirty_ratio or vm.dirty_bytes
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* The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and
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* runtime tasks.
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*/
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void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)
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{
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unsigned long background;
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unsigned long dirty;
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unsigned long available_memory = determine_dirtyable_memory();
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struct task_struct *tsk;
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if (vm_dirty_bytes)
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dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
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else {
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int dirty_ratio;
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dirty_ratio = vm_dirty_ratio;
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if (dirty_ratio < 5)
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dirty_ratio = 5;
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dirty = (dirty_ratio * available_memory) / 100;
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}
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if (dirty_background_bytes)
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background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
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else
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background = (dirty_background_ratio * available_memory) / 100;
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if (background >= dirty)
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background = dirty / 2;
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tsk = current;
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if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
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background += background / 4;
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dirty += dirty / 4;
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}
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*pbackground = background;
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*pdirty = dirty;
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}
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/**
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* bdi_dirty_limit - @bdi's share of dirty throttling threshold
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*
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* Allocate high/low dirty limits to fast/slow devices, in order to prevent
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* - starving fast devices
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* - piling up dirty pages (that will take long time to sync) on slow devices
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*
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* The bdi's share of dirty limit will be adapting to its throughput and
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* bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set.
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*/
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unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty)
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{
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u64 bdi_dirty;
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long numerator, denominator;
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/*
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* Calculate this BDI's share of the dirty ratio.
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*/
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bdi_writeout_fraction(bdi, &numerator, &denominator);
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bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
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bdi_dirty *= numerator;
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do_div(bdi_dirty, denominator);
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bdi_dirty += (dirty * bdi->min_ratio) / 100;
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if (bdi_dirty > (dirty * bdi->max_ratio) / 100)
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bdi_dirty = dirty * bdi->max_ratio / 100;
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return bdi_dirty;
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}
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/*
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* balance_dirty_pages() must be called by processes which are generating dirty
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* data. It looks at the number of dirty pages in the machine and will force
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* the caller to perform writeback if the system is over `vm_dirty_ratio'.
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* If we're over `background_thresh' then the writeback threads are woken to
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* perform some writeout.
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*/
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static void balance_dirty_pages(struct address_space *mapping,
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unsigned long write_chunk)
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{
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long nr_reclaimable, bdi_nr_reclaimable;
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long nr_writeback, bdi_nr_writeback;
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unsigned long background_thresh;
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unsigned long dirty_thresh;
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unsigned long bdi_thresh;
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unsigned long pages_written = 0;
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unsigned long pause = 1;
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bool dirty_exceeded = false;
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struct backing_dev_info *bdi = mapping->backing_dev_info;
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for (;;) {
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struct writeback_control wbc = {
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.sync_mode = WB_SYNC_NONE,
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.older_than_this = NULL,
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.nr_to_write = write_chunk,
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.range_cyclic = 1,
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};
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nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
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global_page_state(NR_UNSTABLE_NFS);
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nr_writeback = global_page_state(NR_WRITEBACK);
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global_dirty_limits(&background_thresh, &dirty_thresh);
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/*
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* Throttle it only when the background writeback cannot
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* catch-up. This avoids (excessively) small writeouts
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* when the bdi limits are ramping up.
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*/
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if (nr_reclaimable + nr_writeback <
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(background_thresh + dirty_thresh) / 2)
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break;
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bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
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bdi_thresh = task_dirty_limit(current, bdi_thresh);
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/*
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* In order to avoid the stacked BDI deadlock we need
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* to ensure we accurately count the 'dirty' pages when
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* the threshold is low.
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*
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* Otherwise it would be possible to get thresh+n pages
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|
* 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 {
|
|
bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
|
|
bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
|
|
}
|
|
|
|
/*
|
|
* The bdi thresh is somehow "soft" limit derived from the
|
|
* global "hard" limit. The former helps to prevent heavy IO
|
|
* bdi or process from holding back light ones; The latter is
|
|
* the last resort safeguard.
|
|
*/
|
|
dirty_exceeded =
|
|
(bdi_nr_reclaimable + bdi_nr_writeback >= bdi_thresh)
|
|
|| (nr_reclaimable + nr_writeback >= dirty_thresh);
|
|
|
|
if (!dirty_exceeded)
|
|
break;
|
|
|
|
if (!bdi->dirty_exceeded)
|
|
bdi->dirty_exceeded = 1;
|
|
|
|
/* Note: nr_reclaimable denotes nr_dirty + nr_unstable.
|
|
* Unstable writes are a feature of certain networked
|
|
* filesystems (i.e. NFS) in which data may have been
|
|
* written to the server's write cache, but has not yet
|
|
* been flushed to permanent storage.
|
|
* Only move pages to writeback if this bdi is over its
|
|
* threshold otherwise wait until the disk writes catch
|
|
* up.
|
|
*/
|
|
trace_wbc_balance_dirty_start(&wbc, bdi);
|
|
if (bdi_nr_reclaimable > bdi_thresh) {
|
|
writeback_inodes_wb(&bdi->wb, &wbc);
|
|
pages_written += write_chunk - wbc.nr_to_write;
|
|
trace_wbc_balance_dirty_written(&wbc, bdi);
|
|
if (pages_written >= write_chunk)
|
|
break; /* We've done our duty */
|
|
}
|
|
trace_wbc_balance_dirty_wait(&wbc, bdi);
|
|
__set_current_state(TASK_INTERRUPTIBLE);
|
|
io_schedule_timeout(pause);
|
|
|
|
/*
|
|
* Increase the delay for each loop, up to our previous
|
|
* default of taking a 100ms nap.
|
|
*/
|
|
pause <<= 1;
|
|
if (pause > HZ / 10)
|
|
pause = HZ / 10;
|
|
}
|
|
|
|
if (!dirty_exceeded && bdi->dirty_exceeded)
|
|
bdi->dirty_exceeded = 0;
|
|
|
|
if (writeback_in_progress(bdi))
|
|
return;
|
|
|
|
/*
|
|
* In laptop mode, we wait until hitting the higher threshold before
|
|
* starting background writeout, and then write out all the way down
|
|
* to the lower threshold. So slow writers cause minimal disk activity.
|
|
*
|
|
* In normal mode, we start background writeout at the lower
|
|
* background_thresh, to keep the amount of dirty memory low.
|
|
*/
|
|
if ((laptop_mode && pages_written) ||
|
|
(!laptop_mode && (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(unsigned long, bdp_ratelimits) = 0;
|
|
|
|
/**
|
|
* balance_dirty_pages_ratelimited_nr - balance dirty memory state
|
|
* @mapping: address_space which was dirtied
|
|
* @nr_pages_dirtied: number of pages which the caller has just dirtied
|
|
*
|
|
* Processes which are dirtying memory should call in here once for each page
|
|
* which was newly dirtied. The function will periodically check the system's
|
|
* dirty state and will initiate writeback if needed.
|
|
*
|
|
* On really big machines, get_writeback_state is expensive, so try to avoid
|
|
* calling it too often (ratelimiting). But once we're over the dirty memory
|
|
* limit we decrease the ratelimiting by a lot, to prevent individual processes
|
|
* from overshooting the limit by (ratelimit_pages) each.
|
|
*/
|
|
void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
|
|
unsigned long nr_pages_dirtied)
|
|
{
|
|
unsigned long ratelimit;
|
|
unsigned long *p;
|
|
|
|
ratelimit = ratelimit_pages;
|
|
if (mapping->backing_dev_info->dirty_exceeded)
|
|
ratelimit = 8;
|
|
|
|
/*
|
|
* Check the rate limiting. Also, we do not want to throttle real-time
|
|
* tasks in balance_dirty_pages(). Period.
|
|
*/
|
|
preempt_disable();
|
|
p = &__get_cpu_var(bdp_ratelimits);
|
|
*p += nr_pages_dirtied;
|
|
if (unlikely(*p >= ratelimit)) {
|
|
ratelimit = sync_writeback_pages(*p);
|
|
*p = 0;
|
|
preempt_enable();
|
|
balance_dirty_pages(mapping, ratelimit);
|
|
return;
|
|
}
|
|
preempt_enable();
|
|
}
|
|
EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
|
|
|
|
void throttle_vm_writeout(gfp_t gfp_mask)
|
|
{
|
|
unsigned long background_thresh;
|
|
unsigned long dirty_thresh;
|
|
|
|
for ( ; ; ) {
|
|
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);
|
|
}
|
|
|
|
/*
|
|
* We've spun up the disk and we're in laptop mode: schedule writeback
|
|
* of all dirty data a few seconds from now. If the flush is already scheduled
|
|
* then push it back - the user is still using the disk.
|
|
*/
|
|
void laptop_io_completion(struct backing_dev_info *info)
|
|
{
|
|
mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode);
|
|
}
|
|
|
|
/*
|
|
* We're in laptop mode and we've just synced. The sync's writes will have
|
|
* caused another writeback to be scheduled by laptop_io_completion.
|
|
* Nothing needs to be written back anymore, so we unschedule the writeback.
|
|
*/
|
|
void laptop_sync_completion(void)
|
|
{
|
|
struct backing_dev_info *bdi;
|
|
|
|
rcu_read_lock();
|
|
|
|
list_for_each_entry_rcu(bdi, &bdi_list, bdi_list)
|
|
del_timer(&bdi->laptop_mode_wb_timer);
|
|
|
|
rcu_read_unlock();
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* If ratelimit_pages is too high then we can get into dirty-data overload
|
|
* if a large number of processes all perform writes at the same time.
|
|
* If it is too low then SMP machines will call the (expensive)
|
|
* get_writeback_state too often.
|
|
*
|
|
* Here we set ratelimit_pages to a level which ensures that when all CPUs are
|
|
* dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory
|
|
* thresholds before writeback cuts in.
|
|
*
|
|
* But the limit should not be set too high. Because it also controls the
|
|
* amount of memory which the balance_dirty_pages() caller has to write back.
|
|
* If this is too large then the caller will block on the IO queue all the
|
|
* time. So limit it to four megabytes - the balance_dirty_pages() caller
|
|
* will write six megabyte chunks, max.
|
|
*/
|
|
|
|
void writeback_set_ratelimit(void)
|
|
{
|
|
ratelimit_pages = vm_total_pages / (num_online_cpus() * 32);
|
|
if (ratelimit_pages < 16)
|
|
ratelimit_pages = 16;
|
|
if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024)
|
|
ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE;
|
|
}
|
|
|
|
static int __cpuinit
|
|
ratelimit_handler(struct notifier_block *self, unsigned long u, void *v)
|
|
{
|
|
writeback_set_ratelimit();
|
|
return NOTIFY_DONE;
|
|
}
|
|
|
|
static struct notifier_block __cpuinitdata ratelimit_nb = {
|
|
.notifier_call = ratelimit_handler,
|
|
.next = NULL,
|
|
};
|
|
|
|
/*
|
|
* Called early on to tune the page writeback dirty limits.
|
|
*
|
|
* We used to scale dirty pages according to how total memory
|
|
* related to pages that could be allocated for buffers (by
|
|
* comparing nr_free_buffer_pages() to vm_total_pages.
|
|
*
|
|
* However, that was when we used "dirty_ratio" to scale with
|
|
* all memory, and we don't do that any more. "dirty_ratio"
|
|
* is now applied to total non-HIGHPAGE memory (by subtracting
|
|
* totalhigh_pages from vm_total_pages), and as such we can't
|
|
* get into the old insane situation any more where we had
|
|
* large amounts of dirty pages compared to a small amount of
|
|
* non-HIGHMEM memory.
|
|
*
|
|
* But we might still want to scale the dirty_ratio by how
|
|
* much memory the box has..
|
|
*/
|
|
void __init page_writeback_init(void)
|
|
{
|
|
int shift;
|
|
|
|
writeback_set_ratelimit();
|
|
register_cpu_notifier(&ratelimit_nb);
|
|
|
|
shift = calc_period_shift();
|
|
prop_descriptor_init(&vm_completions, shift);
|
|
prop_descriptor_init(&vm_dirties, shift);
|
|
}
|
|
|
|
/**
|
|
* tag_pages_for_writeback - tag pages to be written by write_cache_pages
|
|
* @mapping: address space structure to write
|
|
* @start: starting page index
|
|
* @end: ending page index (inclusive)
|
|
*
|
|
* This function scans the page range from @start to @end (inclusive) and tags
|
|
* all pages that have DIRTY tag set with a special TOWRITE tag. The idea is
|
|
* that write_cache_pages (or whoever calls this function) will then use
|
|
* TOWRITE tag to identify pages eligible for writeback. This mechanism is
|
|
* used to avoid livelocking of writeback by a process steadily creating new
|
|
* dirty pages in the file (thus it is important for this function to be quick
|
|
* so that it can tag pages faster than a dirtying process can create them).
|
|
*/
|
|
/*
|
|
* We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency.
|
|
*/
|
|
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();
|
|
} while (tagged >= WRITEBACK_TAG_BATCH);
|
|
}
|
|
EXPORT_SYMBOL(tag_pages_for_writeback);
|
|
|
|
/**
|
|
* write_cache_pages - walk the list of dirty pages of the given address space and write all of them.
|
|
* @mapping: address space structure to write
|
|
* @wbc: subtract the number of written pages from *@wbc->nr_to_write
|
|
* @writepage: function called for each page
|
|
* @data: data passed to writepage function
|
|
*
|
|
* If a page is already under I/O, write_cache_pages() skips it, even
|
|
* if it's dirty. This is desirable behaviour for memory-cleaning writeback,
|
|
* but it is INCORRECT for data-integrity system calls such as fsync(). fsync()
|
|
* and msync() need to guarantee that all the data which was dirty at the time
|
|
* the call was made get new I/O started against them. If wbc->sync_mode is
|
|
* WB_SYNC_ALL then we were called for data integrity and we must wait for
|
|
* existing IO to complete.
|
|
*
|
|
* To avoid livelocks (when other process dirties new pages), we first tag
|
|
* pages which should be written back with TOWRITE tag and only then start
|
|
* writing them. For data-integrity sync we have to be careful so that we do
|
|
* not miss some pages (e.g., because some other process has cleared TOWRITE
|
|
* tag we set). The rule we follow is that TOWRITE tag can be cleared only
|
|
* by the process clearing the DIRTY tag (and submitting the page for IO).
|
|
*/
|
|
int write_cache_pages(struct address_space *mapping,
|
|
struct writeback_control *wbc, writepage_t writepage,
|
|
void *data)
|
|
{
|
|
int ret = 0;
|
|
int done = 0;
|
|
struct pagevec pvec;
|
|
int nr_pages;
|
|
pgoff_t uninitialized_var(writeback_index);
|
|
pgoff_t index;
|
|
pgoff_t end; /* Inclusive */
|
|
pgoff_t done_index;
|
|
int cycled;
|
|
int range_whole = 0;
|
|
int tag;
|
|
|
|
pagevec_init(&pvec, 0);
|
|
if (wbc->range_cyclic) {
|
|
writeback_index = mapping->writeback_index; /* prev offset */
|
|
index = writeback_index;
|
|
if (index == 0)
|
|
cycled = 1;
|
|
else
|
|
cycled = 0;
|
|
end = -1;
|
|
} else {
|
|
index = wbc->range_start >> PAGE_CACHE_SHIFT;
|
|
end = wbc->range_end >> PAGE_CACHE_SHIFT;
|
|
if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
|
|
range_whole = 1;
|
|
cycled = 1; /* ignore range_cyclic tests */
|
|
}
|
|
if (wbc->sync_mode == WB_SYNC_ALL)
|
|
tag = PAGECACHE_TAG_TOWRITE;
|
|
else
|
|
tag = PAGECACHE_TAG_DIRTY;
|
|
retry:
|
|
if (wbc->sync_mode == WB_SYNC_ALL)
|
|
tag_pages_for_writeback(mapping, index, end);
|
|
done_index = index;
|
|
while (!done && (index <= end)) {
|
|
int i;
|
|
|
|
nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag,
|
|
min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1);
|
|
if (nr_pages == 0)
|
|
break;
|
|
|
|
for (i = 0; i < nr_pages; i++) {
|
|
struct page *page = pvec.pages[i];
|
|
|
|
/*
|
|
* At this point, the page may be truncated or
|
|
* invalidated (changing page->mapping to NULL), or
|
|
* even swizzled back from swapper_space to tmpfs file
|
|
* mapping. However, page->index will not change
|
|
* because we have a reference on the page.
|
|
*/
|
|
if (page->index > end) {
|
|
/*
|
|
* can't be range_cyclic (1st pass) because
|
|
* end == -1 in that case.
|
|
*/
|
|
done = 1;
|
|
break;
|
|
}
|
|
|
|
done_index = page->index + 1;
|
|
|
|
lock_page(page);
|
|
|
|
/*
|
|
* Page truncated or invalidated. We can freely skip it
|
|
* then, even for data integrity operations: the page
|
|
* has disappeared concurrently, so there could be no
|
|
* real expectation of this data interity operation
|
|
* even if there is now a new, dirty page at the same
|
|
* pagecache address.
|
|
*/
|
|
if (unlikely(page->mapping != mapping)) {
|
|
continue_unlock:
|
|
unlock_page(page);
|
|
continue;
|
|
}
|
|
|
|
if (!PageDirty(page)) {
|
|
/* someone wrote it for us */
|
|
goto continue_unlock;
|
|
}
|
|
|
|
if (PageWriteback(page)) {
|
|
if (wbc->sync_mode != WB_SYNC_NONE)
|
|
wait_on_page_writeback(page);
|
|
else
|
|
goto continue_unlock;
|
|
}
|
|
|
|
BUG_ON(PageWriteback(page));
|
|
if (!clear_page_dirty_for_io(page))
|
|
goto continue_unlock;
|
|
|
|
trace_wbc_writepage(wbc, mapping->backing_dev_info);
|
|
ret = (*writepage)(page, wbc, data);
|
|
if (unlikely(ret)) {
|
|
if (ret == AOP_WRITEPAGE_ACTIVATE) {
|
|
unlock_page(page);
|
|
ret = 0;
|
|
} else {
|
|
/*
|
|
* done_index is set past this page,
|
|
* so media errors will not choke
|
|
* background writeout for the entire
|
|
* file. This has consequences for
|
|
* range_cyclic semantics (ie. it may
|
|
* not be suitable for data integrity
|
|
* writeout).
|
|
*/
|
|
done = 1;
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (wbc->nr_to_write > 0) {
|
|
if (--wbc->nr_to_write == 0 &&
|
|
wbc->sync_mode == WB_SYNC_NONE) {
|
|
/*
|
|
* We stop writing back only if we are
|
|
* not doing integrity sync. In case of
|
|
* integrity sync we have to keep going
|
|
* because someone may be concurrently
|
|
* dirtying pages, and we might have
|
|
* synced a lot of newly appeared dirty
|
|
* pages, but have not synced all of the
|
|
* old dirty pages.
|
|
*/
|
|
done = 1;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
pagevec_release(&pvec);
|
|
cond_resched();
|
|
}
|
|
if (!cycled && !done) {
|
|
/*
|
|
* range_cyclic:
|
|
* We hit the last page and there is more work to be done: wrap
|
|
* back to the start of the file
|
|
*/
|
|
cycled = 1;
|
|
index = 0;
|
|
end = writeback_index - 1;
|
|
goto retry;
|
|
}
|
|
if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
|
|
mapping->writeback_index = done_index;
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(write_cache_pages);
|
|
|
|
/*
|
|
* Function used by generic_writepages to call the real writepage
|
|
* function and set the mapping flags on error
|
|
*/
|
|
static int __writepage(struct page *page, struct writeback_control *wbc,
|
|
void *data)
|
|
{
|
|
struct address_space *mapping = data;
|
|
int ret = mapping->a_ops->writepage(page, wbc);
|
|
mapping_set_error(mapping, ret);
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them.
|
|
* @mapping: address space structure to write
|
|
* @wbc: subtract the number of written pages from *@wbc->nr_to_write
|
|
*
|
|
* This is a library function, which implements the writepages()
|
|
* address_space_operation.
|
|
*/
|
|
int generic_writepages(struct address_space *mapping,
|
|
struct writeback_control *wbc)
|
|
{
|
|
/* deal with chardevs and other special file */
|
|
if (!mapping->a_ops->writepage)
|
|
return 0;
|
|
|
|
return write_cache_pages(mapping, wbc, __writepage, mapping);
|
|
}
|
|
|
|
EXPORT_SYMBOL(generic_writepages);
|
|
|
|
int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
|
|
{
|
|
int ret;
|
|
|
|
if (wbc->nr_to_write <= 0)
|
|
return 0;
|
|
if (mapping->a_ops->writepages)
|
|
ret = mapping->a_ops->writepages(mapping, wbc);
|
|
else
|
|
ret = generic_writepages(mapping, wbc);
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* write_one_page - write out a single page and optionally wait on I/O
|
|
* @page: the page to write
|
|
* @wait: if true, wait on writeout
|
|
*
|
|
* The page must be locked by the caller and will be unlocked upon return.
|
|
*
|
|
* write_one_page() returns a negative error code if I/O failed.
|
|
*/
|
|
int write_one_page(struct page *page, int wait)
|
|
{
|
|
struct address_space *mapping = page->mapping;
|
|
int ret = 0;
|
|
struct writeback_control wbc = {
|
|
.sync_mode = WB_SYNC_ALL,
|
|
.nr_to_write = 1,
|
|
};
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
|
|
if (wait)
|
|
wait_on_page_writeback(page);
|
|
|
|
if (clear_page_dirty_for_io(page)) {
|
|
page_cache_get(page);
|
|
ret = mapping->a_ops->writepage(page, &wbc);
|
|
if (ret == 0 && wait) {
|
|
wait_on_page_writeback(page);
|
|
if (PageError(page))
|
|
ret = -EIO;
|
|
}
|
|
page_cache_release(page);
|
|
} else {
|
|
unlock_page(page);
|
|
}
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(write_one_page);
|
|
|
|
/*
|
|
* For address_spaces which do not use buffers nor write back.
|
|
*/
|
|
int __set_page_dirty_no_writeback(struct page *page)
|
|
{
|
|
if (!PageDirty(page))
|
|
SetPageDirty(page);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Helper function for set_page_dirty family.
|
|
* NOTE: This relies on being atomic wrt interrupts.
|
|
*/
|
|
void account_page_dirtied(struct page *page, struct address_space *mapping)
|
|
{
|
|
if (mapping_cap_account_dirty(mapping)) {
|
|
__inc_zone_page_state(page, NR_FILE_DIRTY);
|
|
__inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
|
|
task_dirty_inc(current);
|
|
task_io_account_write(PAGE_CACHE_SIZE);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* For address_spaces which do not use buffers. Just tag the page as dirty in
|
|
* its radix tree.
|
|
*
|
|
* This is also used when a single buffer is being dirtied: we want to set the
|
|
* page dirty in that case, but not all the buffers. This is a "bottom-up"
|
|
* dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying.
|
|
*
|
|
* Most callers have locked the page, which pins the address_space in memory.
|
|
* But zap_pte_range() does not lock the page, however in that case the
|
|
* mapping is pinned by the vma's ->vm_file reference.
|
|
*
|
|
* We take care to handle the case where the page was truncated from the
|
|
* mapping by re-checking page_mapping() inside tree_lock.
|
|
*/
|
|
int __set_page_dirty_nobuffers(struct page *page)
|
|
{
|
|
if (!TestSetPageDirty(page)) {
|
|
struct address_space *mapping = page_mapping(page);
|
|
struct address_space *mapping2;
|
|
|
|
if (!mapping)
|
|
return 1;
|
|
|
|
spin_lock_irq(&mapping->tree_lock);
|
|
mapping2 = page_mapping(page);
|
|
if (mapping2) { /* Race with truncate? */
|
|
BUG_ON(mapping2 != mapping);
|
|
WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page));
|
|
account_page_dirtied(page, mapping);
|
|
radix_tree_tag_set(&mapping->page_tree,
|
|
page_index(page), PAGECACHE_TAG_DIRTY);
|
|
}
|
|
spin_unlock_irq(&mapping->tree_lock);
|
|
if (mapping->host) {
|
|
/* !PageAnon && !swapper_space */
|
|
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
|
|
}
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(__set_page_dirty_nobuffers);
|
|
|
|
/*
|
|
* When a writepage implementation decides that it doesn't want to write this
|
|
* page for some reason, it should redirty the locked page via
|
|
* redirty_page_for_writepage() and it should then unlock the page and return 0
|
|
*/
|
|
int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
|
|
{
|
|
wbc->pages_skipped++;
|
|
return __set_page_dirty_nobuffers(page);
|
|
}
|
|
EXPORT_SYMBOL(redirty_page_for_writepage);
|
|
|
|
/*
|
|
* Dirty a page.
|
|
*
|
|
* For pages with a mapping this should be done under the page lock
|
|
* for the benefit of asynchronous memory errors who prefer a consistent
|
|
* dirty state. This rule can be broken in some special cases,
|
|
* but should be better not to.
|
|
*
|
|
* If the mapping doesn't provide a set_page_dirty a_op, then
|
|
* just fall through and assume that it wants buffer_heads.
|
|
*/
|
|
int set_page_dirty(struct page *page)
|
|
{
|
|
struct address_space *mapping = page_mapping(page);
|
|
|
|
if (likely(mapping)) {
|
|
int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
|
|
#ifdef CONFIG_BLOCK
|
|
if (!spd)
|
|
spd = __set_page_dirty_buffers;
|
|
#endif
|
|
return (*spd)(page);
|
|
}
|
|
if (!PageDirty(page)) {
|
|
if (!TestSetPageDirty(page))
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(set_page_dirty);
|
|
|
|
/*
|
|
* set_page_dirty() is racy if the caller has no reference against
|
|
* page->mapping->host, and if the page is unlocked. This is because another
|
|
* CPU could truncate the page off the mapping and then free the mapping.
|
|
*
|
|
* Usually, the page _is_ locked, or the caller is a user-space process which
|
|
* holds a reference on the inode by having an open file.
|
|
*
|
|
* In other cases, the page should be locked before running set_page_dirty().
|
|
*/
|
|
int set_page_dirty_lock(struct page *page)
|
|
{
|
|
int ret;
|
|
|
|
lock_page_nosync(page);
|
|
ret = set_page_dirty(page);
|
|
unlock_page(page);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(set_page_dirty_lock);
|
|
|
|
/*
|
|
* Clear a page's dirty flag, while caring for dirty memory accounting.
|
|
* Returns true if the page was previously dirty.
|
|
*
|
|
* This is for preparing to put the page under writeout. We leave the page
|
|
* tagged as dirty in the radix tree so that a concurrent write-for-sync
|
|
* can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage
|
|
* implementation will run either set_page_writeback() or set_page_dirty(),
|
|
* at which stage we bring the page's dirty flag and radix-tree dirty tag
|
|
* back into sync.
|
|
*
|
|
* This incoherency between the page's dirty flag and radix-tree tag is
|
|
* unfortunate, but it only exists while the page is locked.
|
|
*/
|
|
int clear_page_dirty_for_io(struct page *page)
|
|
{
|
|
struct address_space *mapping = page_mapping(page);
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
|
|
ClearPageReclaim(page);
|
|
if (mapping && mapping_cap_account_dirty(mapping)) {
|
|
/*
|
|
* Yes, Virginia, this is indeed insane.
|
|
*
|
|
* We use this sequence to make sure that
|
|
* (a) we account for dirty stats properly
|
|
* (b) we tell the low-level filesystem to
|
|
* mark the whole page dirty if it was
|
|
* dirty in a pagetable. Only to then
|
|
* (c) clean the page again and return 1 to
|
|
* cause the writeback.
|
|
*
|
|
* This way we avoid all nasty races with the
|
|
* dirty bit in multiple places and clearing
|
|
* them concurrently from different threads.
|
|
*
|
|
* Note! Normally the "set_page_dirty(page)"
|
|
* has no effect on the actual dirty bit - since
|
|
* that will already usually be set. But we
|
|
* need the side effects, and it can help us
|
|
* avoid races.
|
|
*
|
|
* We basically use the page "master dirty bit"
|
|
* as a serialization point for all the different
|
|
* threads doing their things.
|
|
*/
|
|
if (page_mkclean(page))
|
|
set_page_dirty(page);
|
|
/*
|
|
* We carefully synchronise fault handlers against
|
|
* installing a dirty pte and marking the page dirty
|
|
* at this point. We do this by having them hold the
|
|
* page lock at some point after installing their
|
|
* pte, but before marking the page dirty.
|
|
* Pages are always locked coming in here, so we get
|
|
* the desired exclusion. See mm/memory.c:do_wp_page()
|
|
* for more comments.
|
|
*/
|
|
if (TestClearPageDirty(page)) {
|
|
dec_zone_page_state(page, NR_FILE_DIRTY);
|
|
dec_bdi_stat(mapping->backing_dev_info,
|
|
BDI_RECLAIMABLE);
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
return TestClearPageDirty(page);
|
|
}
|
|
EXPORT_SYMBOL(clear_page_dirty_for_io);
|
|
|
|
int test_clear_page_writeback(struct page *page)
|
|
{
|
|
struct address_space *mapping = page_mapping(page);
|
|
int ret;
|
|
|
|
if (mapping) {
|
|
struct backing_dev_info *bdi = mapping->backing_dev_info;
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&mapping->tree_lock, flags);
|
|
ret = TestClearPageWriteback(page);
|
|
if (ret) {
|
|
radix_tree_tag_clear(&mapping->page_tree,
|
|
page_index(page),
|
|
PAGECACHE_TAG_WRITEBACK);
|
|
if (bdi_cap_account_writeback(bdi)) {
|
|
__dec_bdi_stat(bdi, BDI_WRITEBACK);
|
|
__bdi_writeout_inc(bdi);
|
|
}
|
|
}
|
|
spin_unlock_irqrestore(&mapping->tree_lock, flags);
|
|
} else {
|
|
ret = TestClearPageWriteback(page);
|
|
}
|
|
if (ret)
|
|
dec_zone_page_state(page, NR_WRITEBACK);
|
|
return ret;
|
|
}
|
|
|
|
int test_set_page_writeback(struct page *page)
|
|
{
|
|
struct address_space *mapping = page_mapping(page);
|
|
int ret;
|
|
|
|
if (mapping) {
|
|
struct backing_dev_info *bdi = mapping->backing_dev_info;
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&mapping->tree_lock, flags);
|
|
ret = TestSetPageWriteback(page);
|
|
if (!ret) {
|
|
radix_tree_tag_set(&mapping->page_tree,
|
|
page_index(page),
|
|
PAGECACHE_TAG_WRITEBACK);
|
|
if (bdi_cap_account_writeback(bdi))
|
|
__inc_bdi_stat(bdi, BDI_WRITEBACK);
|
|
}
|
|
if (!PageDirty(page))
|
|
radix_tree_tag_clear(&mapping->page_tree,
|
|
page_index(page),
|
|
PAGECACHE_TAG_DIRTY);
|
|
radix_tree_tag_clear(&mapping->page_tree,
|
|
page_index(page),
|
|
PAGECACHE_TAG_TOWRITE);
|
|
spin_unlock_irqrestore(&mapping->tree_lock, flags);
|
|
} else {
|
|
ret = TestSetPageWriteback(page);
|
|
}
|
|
if (!ret)
|
|
inc_zone_page_state(page, NR_WRITEBACK);
|
|
return ret;
|
|
|
|
}
|
|
EXPORT_SYMBOL(test_set_page_writeback);
|
|
|
|
/*
|
|
* Return true if any of the pages in the mapping are marked with the
|
|
* passed tag.
|
|
*/
|
|
int mapping_tagged(struct address_space *mapping, int tag)
|
|
{
|
|
int ret;
|
|
rcu_read_lock();
|
|
ret = radix_tree_tagged(&mapping->page_tree, tag);
|
|
rcu_read_unlock();
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(mapping_tagged);
|