e98be2d599
The estimation value will start from 100MB/s and adapt to the real bandwidth in seconds. It tries to update the bandwidth only when disk is fully utilized. Any inactive period of more than one second will be skipped. The estimated bandwidth will be reflecting how fast the device can writeout when _fully utilized_, and won't drop to 0 when it goes idle. The value will remain constant at disk idle time. At busy write time, if not considering fluctuations, it will also remain high unless be knocked down by possible concurrent reads that compete for the disk time and bandwidth with async writes. The estimation is not done purely in the flusher because there is no guarantee for write_cache_pages() to return timely to update bandwidth. The bdi->avg_write_bandwidth smoothing is very effective for filtering out sudden spikes, however may be a little biased in long term. The overheads are low because the bdi bandwidth update only occurs at 200ms intervals. The 200ms update interval is suitable, because it's not possible to get the real bandwidth for the instance at all, due to large fluctuations. The NFS commits can be as large as seconds worth of data. One XFS completion may be as large as half second worth of data if we are going to increase the write chunk to half second worth of data. In ext4, fluctuations with time period of around 5 seconds is observed. And there is another pattern of irregular periods of up to 20 seconds on SSD tests. That's why we are not only doing the estimation at 200ms intervals, but also averaging them over a period of 3 seconds and then go further to do another level of smoothing in avg_write_bandwidth. CC: Li Shaohua <shaohua.li@intel.com> CC: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
1502 lines
42 KiB
C
1502 lines
42 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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* Estimate write bandwidth at 200ms intervals.
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*/
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#define BANDWIDTH_INTERVAL max(HZ/5, 1)
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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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__inc_bdi_stat(bdi, BDI_WRITTEN);
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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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prop_fraction_percpu(&vm_completions, &bdi->completions,
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numerator, denominator);
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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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/*
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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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* real-time 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 uninitialized_var(available_memory);
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struct task_struct *tsk;
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if (!vm_dirty_bytes || !dirty_background_bytes)
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available_memory = determine_dirtyable_memory();
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|
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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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dirty = (vm_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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|
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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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/**
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* bdi_dirty_limit - @bdi's share of dirty throttling threshold
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* @bdi: the backing_dev_info to query
|
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* @dirty: global dirty limit in pages
|
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*
|
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* Returns @bdi's dirty limit in pages. The term "dirty" in the context of
|
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* dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages.
|
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* And the "limit" in the name is not seriously taken as hard limit in
|
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* balance_dirty_pages().
|
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*
|
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* It allocates 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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unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty)
|
|
{
|
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u64 bdi_dirty;
|
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long numerator, denominator;
|
|
|
|
/*
|
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* Calculate this BDI's share of the dirty ratio.
|
|
*/
|
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bdi_writeout_fraction(bdi, &numerator, &denominator);
|
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|
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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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|
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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;
|
|
|
|
return bdi_dirty;
|
|
}
|
|
|
|
static void bdi_update_write_bandwidth(struct backing_dev_info *bdi,
|
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unsigned long elapsed,
|
|
unsigned long written)
|
|
{
|
|
const unsigned long period = roundup_pow_of_two(3 * HZ);
|
|
unsigned long avg = bdi->avg_write_bandwidth;
|
|
unsigned long old = bdi->write_bandwidth;
|
|
u64 bw;
|
|
|
|
/*
|
|
* bw = written * HZ / elapsed
|
|
*
|
|
* bw * elapsed + write_bandwidth * (period - elapsed)
|
|
* write_bandwidth = ---------------------------------------------------
|
|
* period
|
|
*/
|
|
bw = written - bdi->written_stamp;
|
|
bw *= HZ;
|
|
if (unlikely(elapsed > period)) {
|
|
do_div(bw, elapsed);
|
|
avg = bw;
|
|
goto out;
|
|
}
|
|
bw += (u64)bdi->write_bandwidth * (period - elapsed);
|
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bw >>= ilog2(period);
|
|
|
|
/*
|
|
* one more level of smoothing, for filtering out sudden spikes
|
|
*/
|
|
if (avg > old && old >= (unsigned long)bw)
|
|
avg -= (avg - old) >> 3;
|
|
|
|
if (avg < old && old <= (unsigned long)bw)
|
|
avg += (old - avg) >> 3;
|
|
|
|
out:
|
|
bdi->write_bandwidth = bw;
|
|
bdi->avg_write_bandwidth = avg;
|
|
}
|
|
|
|
void __bdi_update_bandwidth(struct backing_dev_info *bdi,
|
|
unsigned long start_time)
|
|
{
|
|
unsigned long now = jiffies;
|
|
unsigned long elapsed = now - bdi->bw_time_stamp;
|
|
unsigned long written;
|
|
|
|
/*
|
|
* rate-limit, only update once every 200ms.
|
|
*/
|
|
if (elapsed < BANDWIDTH_INTERVAL)
|
|
return;
|
|
|
|
written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]);
|
|
|
|
/*
|
|
* Skip quiet periods when disk bandwidth is under-utilized.
|
|
* (at least 1s idle time between two flusher runs)
|
|
*/
|
|
if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time))
|
|
goto snapshot;
|
|
|
|
bdi_update_write_bandwidth(bdi, elapsed, written);
|
|
|
|
snapshot:
|
|
bdi->written_stamp = written;
|
|
bdi->bw_time_stamp = now;
|
|
}
|
|
|
|
static void bdi_update_bandwidth(struct backing_dev_info *bdi,
|
|
unsigned long start_time)
|
|
{
|
|
if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL))
|
|
return;
|
|
spin_lock(&bdi->wb.list_lock);
|
|
__bdi_update_bandwidth(bdi, start_time);
|
|
spin_unlock(&bdi->wb.list_lock);
|
|
}
|
|
|
|
/*
|
|
* 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 the writeback threads are woken to
|
|
* perform some writeout.
|
|
*/
|
|
static void balance_dirty_pages(struct address_space *mapping,
|
|
unsigned long write_chunk)
|
|
{
|
|
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 pause = 1;
|
|
bool dirty_exceeded = false;
|
|
struct backing_dev_info *bdi = mapping->backing_dev_info;
|
|
unsigned long start_time = jiffies;
|
|
|
|
for (;;) {
|
|
nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
|
|
global_page_state(NR_UNSTABLE_NFS);
|
|
nr_writeback = global_page_state(NR_WRITEBACK);
|
|
|
|
global_dirty_limits(&background_thresh, &dirty_thresh);
|
|
|
|
/*
|
|
* Throttle it only when the background writeback cannot
|
|
* catch-up. This avoids (excessively) small writeouts
|
|
* when the bdi limits are ramping up.
|
|
*/
|
|
if (nr_reclaimable + nr_writeback <=
|
|
(background_thresh + dirty_thresh) / 2)
|
|
break;
|
|
|
|
bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
|
|
bdi_thresh = task_dirty_limit(current, bdi_thresh);
|
|
|
|
/*
|
|
* In order to avoid the stacked BDI deadlock we need
|
|
* to ensure we accurately count the 'dirty' pages when
|
|
* the threshold is low.
|
|
*
|
|
* Otherwise it would be possible to get thresh+n pages
|
|
* reported dirty, even though there are thresh-m pages
|
|
* actually dirty; with m+n sitting in the percpu
|
|
* deltas.
|
|
*/
|
|
if (bdi_thresh < 2*bdi_stat_error(bdi)) {
|
|
bdi_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;
|
|
|
|
bdi_update_bandwidth(bdi, start_time);
|
|
|
|
/* 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_balance_dirty_start(bdi);
|
|
if (bdi_nr_reclaimable > bdi_thresh) {
|
|
pages_written += writeback_inodes_wb(&bdi->wb,
|
|
write_chunk);
|
|
trace_balance_dirty_written(bdi, pages_written);
|
|
if (pages_written >= write_chunk)
|
|
break; /* We've done our duty */
|
|
}
|
|
__set_current_state(TASK_UNINTERRUPTIBLE);
|
|
io_schedule_timeout(pause);
|
|
trace_balance_dirty_wait(bdi);
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
struct backing_dev_info *bdi = mapping->backing_dev_info;
|
|
unsigned long ratelimit;
|
|
unsigned long *p;
|
|
|
|
if (!bdi_cap_account_dirty(bdi))
|
|
return;
|
|
|
|
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();
|
|
/* We check 'start' to handle wrapping when end == ~0UL */
|
|
} while (tagged >= WRITEBACK_TAG_BATCH && start);
|
|
}
|
|
EXPORT_SYMBOL(tag_pages_for_writeback);
|
|
|
|
/**
|
|
* write_cache_pages - walk the list of dirty pages of the given address space and write all of them.
|
|
* @mapping: address space structure to write
|
|
* @wbc: subtract the number of written pages from *@wbc->nr_to_write
|
|
* @writepage: function called for each page
|
|
* @data: data passed to writepage function
|
|
*
|
|
* If a page is already under I/O, write_cache_pages() skips it, even
|
|
* if it's dirty. This is desirable behaviour for memory-cleaning writeback,
|
|
* but it is INCORRECT for data-integrity system calls such as fsync(). fsync()
|
|
* and msync() need to guarantee that all the data which was dirty at the time
|
|
* the call was made get new I/O started against them. If wbc->sync_mode is
|
|
* WB_SYNC_ALL then we were called for data integrity and we must wait for
|
|
* existing IO to complete.
|
|
*
|
|
* To avoid livelocks (when other process dirties new pages), we first tag
|
|
* pages which should be written back with TOWRITE tag and only then start
|
|
* writing them. For data-integrity sync we have to be careful so that we do
|
|
* not miss some pages (e.g., because some other process has cleared TOWRITE
|
|
* tag we set). The rule we follow is that TOWRITE tag can be cleared only
|
|
* by the process clearing the DIRTY tag (and submitting the page for IO).
|
|
*/
|
|
int write_cache_pages(struct address_space *mapping,
|
|
struct writeback_control *wbc, writepage_t writepage,
|
|
void *data)
|
|
{
|
|
int ret = 0;
|
|
int done = 0;
|
|
struct pagevec pvec;
|
|
int nr_pages;
|
|
pgoff_t uninitialized_var(writeback_index);
|
|
pgoff_t index;
|
|
pgoff_t end; /* Inclusive */
|
|
pgoff_t done_index;
|
|
int cycled;
|
|
int range_whole = 0;
|
|
int tag;
|
|
|
|
pagevec_init(&pvec, 0);
|
|
if (wbc->range_cyclic) {
|
|
writeback_index = mapping->writeback_index; /* prev offset */
|
|
index = writeback_index;
|
|
if (index == 0)
|
|
cycled = 1;
|
|
else
|
|
cycled = 0;
|
|
end = -1;
|
|
} else {
|
|
index = wbc->range_start >> PAGE_CACHE_SHIFT;
|
|
end = wbc->range_end >> PAGE_CACHE_SHIFT;
|
|
if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
|
|
range_whole = 1;
|
|
cycled = 1; /* ignore range_cyclic tests */
|
|
}
|
|
if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
|
|
tag = PAGECACHE_TAG_TOWRITE;
|
|
else
|
|
tag = PAGECACHE_TAG_DIRTY;
|
|
retry:
|
|
if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
|
|
tag_pages_for_writeback(mapping, index, end);
|
|
done_index = index;
|
|
while (!done && (index <= end)) {
|
|
int i;
|
|
|
|
nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag,
|
|
min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1);
|
|
if (nr_pages == 0)
|
|
break;
|
|
|
|
for (i = 0; i < nr_pages; i++) {
|
|
struct page *page = pvec.pages[i];
|
|
|
|
/*
|
|
* At this point, the page may be truncated or
|
|
* invalidated (changing page->mapping to NULL), or
|
|
* even swizzled back from swapper_space to tmpfs file
|
|
* mapping. However, page->index will not change
|
|
* because we have a reference on the page.
|
|
*/
|
|
if (page->index > end) {
|
|
/*
|
|
* can't be range_cyclic (1st pass) because
|
|
* end == -1 in that case.
|
|
*/
|
|
done = 1;
|
|
break;
|
|
}
|
|
|
|
done_index = page->index;
|
|
|
|
lock_page(page);
|
|
|
|
/*
|
|
* Page truncated or invalidated. We can freely skip it
|
|
* then, even for data integrity operations: the page
|
|
* has disappeared concurrently, so there could be no
|
|
* real expectation of this data interity operation
|
|
* even if there is now a new, dirty page at the same
|
|
* pagecache address.
|
|
*/
|
|
if (unlikely(page->mapping != mapping)) {
|
|
continue_unlock:
|
|
unlock_page(page);
|
|
continue;
|
|
}
|
|
|
|
if (!PageDirty(page)) {
|
|
/* someone wrote it for us */
|
|
goto continue_unlock;
|
|
}
|
|
|
|
if (PageWriteback(page)) {
|
|
if (wbc->sync_mode != WB_SYNC_NONE)
|
|
wait_on_page_writeback(page);
|
|
else
|
|
goto continue_unlock;
|
|
}
|
|
|
|
BUG_ON(PageWriteback(page));
|
|
if (!clear_page_dirty_for_io(page))
|
|
goto continue_unlock;
|
|
|
|
trace_wbc_writepage(wbc, mapping->backing_dev_info);
|
|
ret = (*writepage)(page, wbc, data);
|
|
if (unlikely(ret)) {
|
|
if (ret == AOP_WRITEPAGE_ACTIVATE) {
|
|
unlock_page(page);
|
|
ret = 0;
|
|
} else {
|
|
/*
|
|
* done_index is set past this page,
|
|
* so media errors will not choke
|
|
* background writeout for the entire
|
|
* file. This has consequences for
|
|
* range_cyclic semantics (ie. it may
|
|
* not be suitable for data integrity
|
|
* writeout).
|
|
*/
|
|
done_index = page->index + 1;
|
|
done = 1;
|
|
break;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* We stop writing back only if we are not doing
|
|
* integrity sync. In case of integrity sync we have to
|
|
* keep going until we have written all the pages
|
|
* we tagged for writeback prior to entering this loop.
|
|
*/
|
|
if (--wbc->nr_to_write <= 0 &&
|
|
wbc->sync_mode == WB_SYNC_NONE) {
|
|
done = 1;
|
|
break;
|
|
}
|
|
}
|
|
pagevec_release(&pvec);
|
|
cond_resched();
|
|
}
|
|
if (!cycled && !done) {
|
|
/*
|
|
* range_cyclic:
|
|
* We hit the last page and there is more work to be done: wrap
|
|
* back to the start of the file
|
|
*/
|
|
cycled = 1;
|
|
index = 0;
|
|
end = writeback_index - 1;
|
|
goto retry;
|
|
}
|
|
if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
|
|
mapping->writeback_index = done_index;
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(write_cache_pages);
|
|
|
|
/*
|
|
* Function used by generic_writepages to call the real writepage
|
|
* function and set the mapping flags on error
|
|
*/
|
|
static int __writepage(struct page *page, struct writeback_control *wbc,
|
|
void *data)
|
|
{
|
|
struct address_space *mapping = data;
|
|
int ret = mapping->a_ops->writepage(page, wbc);
|
|
mapping_set_error(mapping, ret);
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them.
|
|
* @mapping: address space structure to write
|
|
* @wbc: subtract the number of written pages from *@wbc->nr_to_write
|
|
*
|
|
* This is a library function, which implements the writepages()
|
|
* address_space_operation.
|
|
*/
|
|
int generic_writepages(struct address_space *mapping,
|
|
struct writeback_control *wbc)
|
|
{
|
|
struct blk_plug plug;
|
|
int ret;
|
|
|
|
/* deal with chardevs and other special file */
|
|
if (!mapping->a_ops->writepage)
|
|
return 0;
|
|
|
|
blk_start_plug(&plug);
|
|
ret = write_cache_pages(mapping, wbc, __writepage, mapping);
|
|
blk_finish_plug(&plug);
|
|
return ret;
|
|
}
|
|
|
|
EXPORT_SYMBOL(generic_writepages);
|
|
|
|
int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
|
|
{
|
|
int ret;
|
|
|
|
if (wbc->nr_to_write <= 0)
|
|
return 0;
|
|
if (mapping->a_ops->writepages)
|
|
ret = mapping->a_ops->writepages(mapping, wbc);
|
|
else
|
|
ret = generic_writepages(mapping, wbc);
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* write_one_page - write out a single page and optionally wait on I/O
|
|
* @page: the page to write
|
|
* @wait: if true, wait on writeout
|
|
*
|
|
* The page must be locked by the caller and will be unlocked upon return.
|
|
*
|
|
* write_one_page() returns a negative error code if I/O failed.
|
|
*/
|
|
int write_one_page(struct page *page, int wait)
|
|
{
|
|
struct address_space *mapping = page->mapping;
|
|
int ret = 0;
|
|
struct writeback_control wbc = {
|
|
.sync_mode = WB_SYNC_ALL,
|
|
.nr_to_write = 1,
|
|
};
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
|
|
if (wait)
|
|
wait_on_page_writeback(page);
|
|
|
|
if (clear_page_dirty_for_io(page)) {
|
|
page_cache_get(page);
|
|
ret = mapping->a_ops->writepage(page, &wbc);
|
|
if (ret == 0 && wait) {
|
|
wait_on_page_writeback(page);
|
|
if (PageError(page))
|
|
ret = -EIO;
|
|
}
|
|
page_cache_release(page);
|
|
} else {
|
|
unlock_page(page);
|
|
}
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(write_one_page);
|
|
|
|
/*
|
|
* For address_spaces which do not use buffers nor write back.
|
|
*/
|
|
int __set_page_dirty_no_writeback(struct page *page)
|
|
{
|
|
if (!PageDirty(page))
|
|
return !TestSetPageDirty(page);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Helper function for set_page_dirty family.
|
|
* NOTE: This relies on being atomic wrt interrupts.
|
|
*/
|
|
void account_page_dirtied(struct page *page, struct address_space *mapping)
|
|
{
|
|
if (mapping_cap_account_dirty(mapping)) {
|
|
__inc_zone_page_state(page, NR_FILE_DIRTY);
|
|
__inc_zone_page_state(page, NR_DIRTIED);
|
|
__inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
|
|
task_dirty_inc(current);
|
|
task_io_account_write(PAGE_CACHE_SIZE);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(account_page_dirtied);
|
|
|
|
/*
|
|
* Helper function for set_page_writeback family.
|
|
* NOTE: Unlike account_page_dirtied this does not rely on being atomic
|
|
* wrt interrupts.
|
|
*/
|
|
void account_page_writeback(struct page *page)
|
|
{
|
|
inc_zone_page_state(page, NR_WRITEBACK);
|
|
inc_zone_page_state(page, NR_WRITTEN);
|
|
}
|
|
EXPORT_SYMBOL(account_page_writeback);
|
|
|
|
/*
|
|
* For address_spaces which do not use buffers. Just tag the page as dirty in
|
|
* its radix tree.
|
|
*
|
|
* This is also used when a single buffer is being dirtied: we want to set the
|
|
* page dirty in that case, but not all the buffers. This is a "bottom-up"
|
|
* dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying.
|
|
*
|
|
* Most callers have locked the page, which pins the address_space in memory.
|
|
* But zap_pte_range() does not lock the page, however in that case the
|
|
* mapping is pinned by the vma's ->vm_file reference.
|
|
*
|
|
* We take care to handle the case where the page was truncated from the
|
|
* mapping by re-checking page_mapping() inside tree_lock.
|
|
*/
|
|
int __set_page_dirty_nobuffers(struct page *page)
|
|
{
|
|
if (!TestSetPageDirty(page)) {
|
|
struct address_space *mapping = page_mapping(page);
|
|
struct address_space *mapping2;
|
|
|
|
if (!mapping)
|
|
return 1;
|
|
|
|
spin_lock_irq(&mapping->tree_lock);
|
|
mapping2 = page_mapping(page);
|
|
if (mapping2) { /* Race with truncate? */
|
|
BUG_ON(mapping2 != mapping);
|
|
WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page));
|
|
account_page_dirtied(page, mapping);
|
|
radix_tree_tag_set(&mapping->page_tree,
|
|
page_index(page), PAGECACHE_TAG_DIRTY);
|
|
}
|
|
spin_unlock_irq(&mapping->tree_lock);
|
|
if (mapping->host) {
|
|
/* !PageAnon && !swapper_space */
|
|
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
|
|
}
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(__set_page_dirty_nobuffers);
|
|
|
|
/*
|
|
* When a writepage implementation decides that it doesn't want to write this
|
|
* page for some reason, it should redirty the locked page via
|
|
* redirty_page_for_writepage() and it should then unlock the page and return 0
|
|
*/
|
|
int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
|
|
{
|
|
wbc->pages_skipped++;
|
|
return __set_page_dirty_nobuffers(page);
|
|
}
|
|
EXPORT_SYMBOL(redirty_page_for_writepage);
|
|
|
|
/*
|
|
* Dirty a page.
|
|
*
|
|
* For pages with a mapping this should be done under the page lock
|
|
* for the benefit of asynchronous memory errors who prefer a consistent
|
|
* dirty state. This rule can be broken in some special cases,
|
|
* but should be better not to.
|
|
*
|
|
* If the mapping doesn't provide a set_page_dirty a_op, then
|
|
* just fall through and assume that it wants buffer_heads.
|
|
*/
|
|
int set_page_dirty(struct page *page)
|
|
{
|
|
struct address_space *mapping = page_mapping(page);
|
|
|
|
if (likely(mapping)) {
|
|
int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
|
|
/*
|
|
* readahead/lru_deactivate_page could remain
|
|
* PG_readahead/PG_reclaim due to race with end_page_writeback
|
|
* About readahead, if the page is written, the flags would be
|
|
* reset. So no problem.
|
|
* About lru_deactivate_page, if the page is redirty, the flag
|
|
* will be reset. So no problem. but if the page is used by readahead
|
|
* it will confuse readahead and make it restart the size rampup
|
|
* process. But it's a trivial problem.
|
|
*/
|
|
ClearPageReclaim(page);
|
|
#ifdef CONFIG_BLOCK
|
|
if (!spd)
|
|
spd = __set_page_dirty_buffers;
|
|
#endif
|
|
return (*spd)(page);
|
|
}
|
|
if (!PageDirty(page)) {
|
|
if (!TestSetPageDirty(page))
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(set_page_dirty);
|
|
|
|
/*
|
|
* set_page_dirty() is racy if the caller has no reference against
|
|
* page->mapping->host, and if the page is unlocked. This is because another
|
|
* CPU could truncate the page off the mapping and then free the mapping.
|
|
*
|
|
* Usually, the page _is_ locked, or the caller is a user-space process which
|
|
* holds a reference on the inode by having an open file.
|
|
*
|
|
* In other cases, the page should be locked before running set_page_dirty().
|
|
*/
|
|
int set_page_dirty_lock(struct page *page)
|
|
{
|
|
int ret;
|
|
|
|
lock_page(page);
|
|
ret = set_page_dirty(page);
|
|
unlock_page(page);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(set_page_dirty_lock);
|
|
|
|
/*
|
|
* Clear a page's dirty flag, while caring for dirty memory accounting.
|
|
* Returns true if the page was previously dirty.
|
|
*
|
|
* This is for preparing to put the page under writeout. We leave the page
|
|
* tagged as dirty in the radix tree so that a concurrent write-for-sync
|
|
* can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage
|
|
* implementation will run either set_page_writeback() or set_page_dirty(),
|
|
* at which stage we bring the page's dirty flag and radix-tree dirty tag
|
|
* back into sync.
|
|
*
|
|
* This incoherency between the page's dirty flag and radix-tree tag is
|
|
* unfortunate, but it only exists while the page is locked.
|
|
*/
|
|
int clear_page_dirty_for_io(struct page *page)
|
|
{
|
|
struct address_space *mapping = page_mapping(page);
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
|
|
if (mapping && mapping_cap_account_dirty(mapping)) {
|
|
/*
|
|
* Yes, Virginia, this is indeed insane.
|
|
*
|
|
* We use this sequence to make sure that
|
|
* (a) we account for dirty stats properly
|
|
* (b) we tell the low-level filesystem to
|
|
* mark the whole page dirty if it was
|
|
* dirty in a pagetable. Only to then
|
|
* (c) clean the page again and return 1 to
|
|
* cause the writeback.
|
|
*
|
|
* This way we avoid all nasty races with the
|
|
* dirty bit in multiple places and clearing
|
|
* them concurrently from different threads.
|
|
*
|
|
* Note! Normally the "set_page_dirty(page)"
|
|
* has no effect on the actual dirty bit - since
|
|
* that will already usually be set. But we
|
|
* need the side effects, and it can help us
|
|
* avoid races.
|
|
*
|
|
* We basically use the page "master dirty bit"
|
|
* as a serialization point for all the different
|
|
* threads doing their things.
|
|
*/
|
|
if (page_mkclean(page))
|
|
set_page_dirty(page);
|
|
/*
|
|
* We carefully synchronise fault handlers against
|
|
* installing a dirty pte and marking the page dirty
|
|
* at this point. We do this by having them hold the
|
|
* page lock at some point after installing their
|
|
* pte, but before marking the page dirty.
|
|
* Pages are always locked coming in here, so we get
|
|
* the desired exclusion. See mm/memory.c:do_wp_page()
|
|
* for more comments.
|
|
*/
|
|
if (TestClearPageDirty(page)) {
|
|
dec_zone_page_state(page, NR_FILE_DIRTY);
|
|
dec_bdi_stat(mapping->backing_dev_info,
|
|
BDI_RECLAIMABLE);
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
return TestClearPageDirty(page);
|
|
}
|
|
EXPORT_SYMBOL(clear_page_dirty_for_io);
|
|
|
|
int test_clear_page_writeback(struct page *page)
|
|
{
|
|
struct address_space *mapping = page_mapping(page);
|
|
int ret;
|
|
|
|
if (mapping) {
|
|
struct backing_dev_info *bdi = mapping->backing_dev_info;
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&mapping->tree_lock, flags);
|
|
ret = TestClearPageWriteback(page);
|
|
if (ret) {
|
|
radix_tree_tag_clear(&mapping->page_tree,
|
|
page_index(page),
|
|
PAGECACHE_TAG_WRITEBACK);
|
|
if (bdi_cap_account_writeback(bdi)) {
|
|
__dec_bdi_stat(bdi, BDI_WRITEBACK);
|
|
__bdi_writeout_inc(bdi);
|
|
}
|
|
}
|
|
spin_unlock_irqrestore(&mapping->tree_lock, flags);
|
|
} else {
|
|
ret = TestClearPageWriteback(page);
|
|
}
|
|
if (ret)
|
|
dec_zone_page_state(page, NR_WRITEBACK);
|
|
return ret;
|
|
}
|
|
|
|
int test_set_page_writeback(struct page *page)
|
|
{
|
|
struct address_space *mapping = page_mapping(page);
|
|
int ret;
|
|
|
|
if (mapping) {
|
|
struct backing_dev_info *bdi = mapping->backing_dev_info;
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&mapping->tree_lock, flags);
|
|
ret = TestSetPageWriteback(page);
|
|
if (!ret) {
|
|
radix_tree_tag_set(&mapping->page_tree,
|
|
page_index(page),
|
|
PAGECACHE_TAG_WRITEBACK);
|
|
if (bdi_cap_account_writeback(bdi))
|
|
__inc_bdi_stat(bdi, BDI_WRITEBACK);
|
|
}
|
|
if (!PageDirty(page))
|
|
radix_tree_tag_clear(&mapping->page_tree,
|
|
page_index(page),
|
|
PAGECACHE_TAG_DIRTY);
|
|
radix_tree_tag_clear(&mapping->page_tree,
|
|
page_index(page),
|
|
PAGECACHE_TAG_TOWRITE);
|
|
spin_unlock_irqrestore(&mapping->tree_lock, flags);
|
|
} else {
|
|
ret = TestSetPageWriteback(page);
|
|
}
|
|
if (!ret)
|
|
account_page_writeback(page);
|
|
return ret;
|
|
|
|
}
|
|
EXPORT_SYMBOL(test_set_page_writeback);
|
|
|
|
/*
|
|
* Return true if any of the pages in the mapping are marked with the
|
|
* passed tag.
|
|
*/
|
|
int mapping_tagged(struct address_space *mapping, int tag)
|
|
{
|
|
int ret;
|
|
rcu_read_lock();
|
|
ret = radix_tree_tagged(&mapping->page_tree, tag);
|
|
rcu_read_unlock();
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(mapping_tagged);
|