| /* |
| * mm/page-writeback.c. |
| * |
| * Copyright (C) 2002, Linus Torvalds. |
| * |
| * Contains functions related to writing back dirty pages at the |
| * address_space level. |
| * |
| * 10Apr2002 akpm@zip.com.au |
| * Initial version |
| */ |
| |
| #include <linux/kernel.h> |
| #include <linux/module.h> |
| #include <linux/spinlock.h> |
| #include <linux/fs.h> |
| #include <linux/mm.h> |
| #include <linux/swap.h> |
| #include <linux/slab.h> |
| #include <linux/pagemap.h> |
| #include <linux/writeback.h> |
| #include <linux/init.h> |
| #include <linux/backing-dev.h> |
| #include <linux/blkdev.h> |
| #include <linux/mpage.h> |
| #include <linux/percpu.h> |
| #include <linux/notifier.h> |
| #include <linux/smp.h> |
| #include <linux/sysctl.h> |
| #include <linux/cpu.h> |
| #include <linux/syscalls.h> |
| |
| /* |
| * The maximum number of pages to writeout in a single bdflush/kupdate |
| * operation. We do this so we don't hold I_LOCK against an inode for |
| * enormous amounts of time, which would block a userspace task which has |
| * been forced to throttle against that inode. Also, the code reevaluates |
| * the dirty each time it has written this many pages. |
| */ |
| #define MAX_WRITEBACK_PAGES 1024 |
| |
| /* |
| * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited |
| * will look to see if it needs to force writeback or throttling. |
| */ |
| static long ratelimit_pages = 32; |
| |
| static long total_pages; /* The total number of pages in the machine. */ |
| static int dirty_exceeded __cacheline_aligned_in_smp; /* Dirty mem may be over limit */ |
| |
| /* |
| * When balance_dirty_pages decides that the caller needs to perform some |
| * non-background writeback, this is how many pages it will attempt to write. |
| * It should be somewhat larger than RATELIMIT_PAGES to ensure that reasonably |
| * large amounts of I/O are submitted. |
| */ |
| static inline long sync_writeback_pages(void) |
| { |
| return ratelimit_pages + ratelimit_pages / 2; |
| } |
| |
| /* The following parameters are exported via /proc/sys/vm */ |
| |
| /* |
| * Start background writeback (via pdflush) at this percentage |
| */ |
| int dirty_background_ratio = 10; |
| |
| /* |
| * The generator of dirty data starts writeback at this percentage |
| */ |
| int vm_dirty_ratio = 40; |
| |
| /* |
| * The interval between `kupdate'-style writebacks, in jiffies |
| */ |
| int dirty_writeback_interval = 5 * HZ; |
| |
| /* |
| * The longest number of jiffies for which data is allowed to remain dirty |
| */ |
| int dirty_expire_interval = 30 * HZ; |
| |
| /* |
| * Flag that makes the machine dump writes/reads and block dirtyings. |
| */ |
| int block_dump; |
| |
| /* |
| * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies: |
| * a full sync is triggered after this time elapses without any disk activity. |
| */ |
| int laptop_mode; |
| |
| EXPORT_SYMBOL(laptop_mode); |
| |
| /* End of sysctl-exported parameters */ |
| |
| |
| static void background_writeout(unsigned long _min_pages); |
| |
| struct writeback_state |
| { |
| unsigned long nr_dirty; |
| unsigned long nr_unstable; |
| unsigned long nr_mapped; |
| unsigned long nr_writeback; |
| }; |
| |
| static void get_writeback_state(struct writeback_state *wbs) |
| { |
| wbs->nr_dirty = global_page_state(NR_FILE_DIRTY); |
| wbs->nr_unstable = read_page_state(nr_unstable); |
| wbs->nr_mapped = global_page_state(NR_FILE_MAPPED) + |
| global_page_state(NR_ANON_PAGES); |
| wbs->nr_writeback = global_page_state(NR_WRITEBACK); |
| } |
| |
| /* |
| * Work out the current dirty-memory clamping and background writeout |
| * thresholds. |
| * |
| * The main aim here is to lower them aggressively if there is a lot of mapped |
| * memory around. To avoid stressing page reclaim with lots of unreclaimable |
| * pages. It is better to clamp down on writers than to start swapping, and |
| * performing lots of scanning. |
| * |
| * We only allow 1/2 of the currently-unmapped memory to be dirtied. |
| * |
| * We don't permit the clamping level to fall below 5% - that is getting rather |
| * excessive. |
| * |
| * We make sure that the background writeout level is below the adjusted |
| * clamping level. |
| */ |
| static void |
| get_dirty_limits(struct writeback_state *wbs, long *pbackground, long *pdirty, |
| struct address_space *mapping) |
| { |
| int background_ratio; /* Percentages */ |
| int dirty_ratio; |
| int unmapped_ratio; |
| long background; |
| long dirty; |
| unsigned long available_memory = total_pages; |
| struct task_struct *tsk; |
| |
| get_writeback_state(wbs); |
| |
| #ifdef CONFIG_HIGHMEM |
| /* |
| * If this mapping can only allocate from low memory, |
| * we exclude high memory from our count. |
| */ |
| if (mapping && !(mapping_gfp_mask(mapping) & __GFP_HIGHMEM)) |
| available_memory -= totalhigh_pages; |
| #endif |
| |
| |
| unmapped_ratio = 100 - (wbs->nr_mapped * 100) / total_pages; |
| |
| dirty_ratio = vm_dirty_ratio; |
| if (dirty_ratio > unmapped_ratio / 2) |
| dirty_ratio = unmapped_ratio / 2; |
| |
| if (dirty_ratio < 5) |
| dirty_ratio = 5; |
| |
| background_ratio = dirty_background_ratio; |
| if (background_ratio >= dirty_ratio) |
| background_ratio = dirty_ratio / 2; |
| |
| background = (background_ratio * available_memory) / 100; |
| dirty = (dirty_ratio * available_memory) / 100; |
| tsk = current; |
| if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { |
| background += background / 4; |
| dirty += dirty / 4; |
| } |
| *pbackground = background; |
| *pdirty = dirty; |
| } |
| |
| /* |
| * balance_dirty_pages() must be called by processes which are generating dirty |
| * data. It looks at the number of dirty pages in the machine and will force |
| * the caller to perform writeback if the system is over `vm_dirty_ratio'. |
| * If we're over `background_thresh' then pdflush is woken to perform some |
| * writeout. |
| */ |
| static void balance_dirty_pages(struct address_space *mapping) |
| { |
| struct writeback_state wbs; |
| long nr_reclaimable; |
| long background_thresh; |
| long dirty_thresh; |
| unsigned long pages_written = 0; |
| unsigned long write_chunk = sync_writeback_pages(); |
| |
| struct backing_dev_info *bdi = mapping->backing_dev_info; |
| |
| for (;;) { |
| struct writeback_control wbc = { |
| .bdi = bdi, |
| .sync_mode = WB_SYNC_NONE, |
| .older_than_this = NULL, |
| .nr_to_write = write_chunk, |
| .range_cyclic = 1, |
| }; |
| |
| get_dirty_limits(&wbs, &background_thresh, |
| &dirty_thresh, mapping); |
| nr_reclaimable = wbs.nr_dirty + wbs.nr_unstable; |
| if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh) |
| break; |
| |
| if (!dirty_exceeded) |
| 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. |
| */ |
| if (nr_reclaimable) { |
| writeback_inodes(&wbc); |
| get_dirty_limits(&wbs, &background_thresh, |
| &dirty_thresh, mapping); |
| nr_reclaimable = wbs.nr_dirty + wbs.nr_unstable; |
| if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh) |
| break; |
| pages_written += write_chunk - wbc.nr_to_write; |
| if (pages_written >= write_chunk) |
| break; /* We've done our duty */ |
| } |
| blk_congestion_wait(WRITE, HZ/10); |
| } |
| |
| if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh && dirty_exceeded) |
| dirty_exceeded = 0; |
| |
| if (writeback_in_progress(bdi)) |
| return; /* pdflush is already working this queue */ |
| |
| /* |
| * 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))) |
| pdflush_operation(background_writeout, 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) |
| { |
| static DEFINE_PER_CPU(unsigned long, ratelimits) = 0; |
| unsigned long ratelimit; |
| unsigned long *p; |
| |
| ratelimit = ratelimit_pages; |
| if (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(ratelimits); |
| *p += nr_pages_dirtied; |
| if (unlikely(*p >= ratelimit)) { |
| *p = 0; |
| preempt_enable(); |
| balance_dirty_pages(mapping); |
| return; |
| } |
| preempt_enable(); |
| } |
| EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr); |
| |
| void throttle_vm_writeout(void) |
| { |
| struct writeback_state wbs; |
| long background_thresh; |
| long dirty_thresh; |
| |
| for ( ; ; ) { |
| get_dirty_limits(&wbs, &background_thresh, &dirty_thresh, NULL); |
| |
| /* |
| * 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 (wbs.nr_unstable + wbs.nr_writeback <= dirty_thresh) |
| break; |
| blk_congestion_wait(WRITE, HZ/10); |
| } |
| } |
| |
| |
| /* |
| * writeback at least _min_pages, and keep writing until the amount of dirty |
| * memory is less than the background threshold, or until we're all clean. |
| */ |
| static void background_writeout(unsigned long _min_pages) |
| { |
| long min_pages = _min_pages; |
| struct writeback_control wbc = { |
| .bdi = NULL, |
| .sync_mode = WB_SYNC_NONE, |
| .older_than_this = NULL, |
| .nr_to_write = 0, |
| .nonblocking = 1, |
| .range_cyclic = 1, |
| }; |
| |
| for ( ; ; ) { |
| struct writeback_state wbs; |
| long background_thresh; |
| long dirty_thresh; |
| |
| get_dirty_limits(&wbs, &background_thresh, &dirty_thresh, NULL); |
| if (wbs.nr_dirty + wbs.nr_unstable < background_thresh |
| && min_pages <= 0) |
| break; |
| wbc.encountered_congestion = 0; |
| wbc.nr_to_write = MAX_WRITEBACK_PAGES; |
| wbc.pages_skipped = 0; |
| writeback_inodes(&wbc); |
| min_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write; |
| if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) { |
| /* Wrote less than expected */ |
| blk_congestion_wait(WRITE, HZ/10); |
| if (!wbc.encountered_congestion) |
| break; |
| } |
| } |
| } |
| |
| /* |
| * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back |
| * the whole world. Returns 0 if a pdflush thread was dispatched. Returns |
| * -1 if all pdflush threads were busy. |
| */ |
| int wakeup_pdflush(long nr_pages) |
| { |
| if (nr_pages == 0) { |
| struct writeback_state wbs; |
| |
| get_writeback_state(&wbs); |
| nr_pages = wbs.nr_dirty + wbs.nr_unstable; |
| } |
| return pdflush_operation(background_writeout, nr_pages); |
| } |
| |
| static void wb_timer_fn(unsigned long unused); |
| static void laptop_timer_fn(unsigned long unused); |
| |
| static DEFINE_TIMER(wb_timer, wb_timer_fn, 0, 0); |
| static DEFINE_TIMER(laptop_mode_wb_timer, laptop_timer_fn, 0, 0); |
| |
| /* |
| * Periodic writeback of "old" data. |
| * |
| * Define "old": the first time one of an inode's pages is dirtied, we mark the |
| * dirtying-time in the inode's address_space. So this periodic writeback code |
| * just walks the superblock inode list, writing back any inodes which are |
| * older than a specific point in time. |
| * |
| * Try to run once per dirty_writeback_interval. But if a writeback event |
| * takes longer than a dirty_writeback_interval interval, then leave a |
| * one-second gap. |
| * |
| * older_than_this takes precedence over nr_to_write. So we'll only write back |
| * all dirty pages if they are all attached to "old" mappings. |
| */ |
| static void wb_kupdate(unsigned long arg) |
| { |
| unsigned long oldest_jif; |
| unsigned long start_jif; |
| unsigned long next_jif; |
| long nr_to_write; |
| struct writeback_state wbs; |
| struct writeback_control wbc = { |
| .bdi = NULL, |
| .sync_mode = WB_SYNC_NONE, |
| .older_than_this = &oldest_jif, |
| .nr_to_write = 0, |
| .nonblocking = 1, |
| .for_kupdate = 1, |
| .range_cyclic = 1, |
| }; |
| |
| sync_supers(); |
| |
| get_writeback_state(&wbs); |
| oldest_jif = jiffies - dirty_expire_interval; |
| start_jif = jiffies; |
| next_jif = start_jif + dirty_writeback_interval; |
| nr_to_write = wbs.nr_dirty + wbs.nr_unstable + |
| (inodes_stat.nr_inodes - inodes_stat.nr_unused); |
| while (nr_to_write > 0) { |
| wbc.encountered_congestion = 0; |
| wbc.nr_to_write = MAX_WRITEBACK_PAGES; |
| writeback_inodes(&wbc); |
| if (wbc.nr_to_write > 0) { |
| if (wbc.encountered_congestion) |
| blk_congestion_wait(WRITE, HZ/10); |
| else |
| break; /* All the old data is written */ |
| } |
| nr_to_write -= MAX_WRITEBACK_PAGES - wbc.nr_to_write; |
| } |
| if (time_before(next_jif, jiffies + HZ)) |
| next_jif = jiffies + HZ; |
| if (dirty_writeback_interval) |
| mod_timer(&wb_timer, next_jif); |
| } |
| |
| /* |
| * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs |
| */ |
| int dirty_writeback_centisecs_handler(ctl_table *table, int write, |
| struct file *file, void __user *buffer, size_t *length, loff_t *ppos) |
| { |
| proc_dointvec_userhz_jiffies(table, write, file, buffer, length, ppos); |
| if (dirty_writeback_interval) { |
| mod_timer(&wb_timer, |
| jiffies + dirty_writeback_interval); |
| } else { |
| del_timer(&wb_timer); |
| } |
| return 0; |
| } |
| |
| static void wb_timer_fn(unsigned long unused) |
| { |
| if (pdflush_operation(wb_kupdate, 0) < 0) |
| mod_timer(&wb_timer, jiffies + HZ); /* delay 1 second */ |
| } |
| |
| static void laptop_flush(unsigned long unused) |
| { |
| sys_sync(); |
| } |
| |
| static void laptop_timer_fn(unsigned long unused) |
| { |
| pdflush_operation(laptop_flush, 0); |
| } |
| |
| /* |
| * 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(void) |
| { |
| mod_timer(&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) |
| { |
| del_timer(&laptop_mode_wb_timer); |
| } |
| |
| /* |
| * 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. |
| */ |
| |
| static void set_ratelimit(void) |
| { |
| ratelimit_pages = 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) |
| { |
| set_ratelimit(); |
| return 0; |
| } |
| |
| static struct notifier_block __cpuinitdata ratelimit_nb = { |
| .notifier_call = ratelimit_handler, |
| .next = NULL, |
| }; |
| |
| /* |
| * If the machine has a large highmem:lowmem ratio then scale back the default |
| * dirty memory thresholds: allowing too much dirty highmem pins an excessive |
| * number of buffer_heads. |
| */ |
| void __init page_writeback_init(void) |
| { |
| long buffer_pages = nr_free_buffer_pages(); |
| long correction; |
| |
| total_pages = nr_free_pagecache_pages(); |
| |
| correction = (100 * 4 * buffer_pages) / total_pages; |
| |
| if (correction < 100) { |
| dirty_background_ratio *= correction; |
| dirty_background_ratio /= 100; |
| vm_dirty_ratio *= correction; |
| vm_dirty_ratio /= 100; |
| |
| if (dirty_background_ratio <= 0) |
| dirty_background_ratio = 1; |
| if (vm_dirty_ratio <= 0) |
| vm_dirty_ratio = 1; |
| } |
| mod_timer(&wb_timer, jiffies + dirty_writeback_interval); |
| set_ratelimit(); |
| register_cpu_notifier(&ratelimit_nb); |
| } |
| |
| int do_writepages(struct address_space *mapping, struct writeback_control *wbc) |
| { |
| int ret; |
| |
| if (wbc->nr_to_write <= 0) |
| return 0; |
| wbc->for_writepages = 1; |
| if (mapping->a_ops->writepages) |
| ret = mapping->a_ops->writepages(mapping, wbc); |
| else |
| ret = generic_writepages(mapping, wbc); |
| wbc->for_writepages = 0; |
| return ret; |
| } |
| |
| /** |
| * 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. 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() insode 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) { |
| write_lock_irq(&mapping->tree_lock); |
| mapping2 = page_mapping(page); |
| if (mapping2) { /* Race with truncate? */ |
| BUG_ON(mapping2 != mapping); |
| if (mapping_cap_account_dirty(mapping)) |
| __inc_zone_page_state(page, |
| NR_FILE_DIRTY); |
| radix_tree_tag_set(&mapping->page_tree, |
| page_index(page), PAGECACHE_TAG_DIRTY); |
| } |
| write_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); |
| |
| /* |
| * If the mapping doesn't provide a set_page_dirty a_op, then |
| * just fall through and assume that it wants buffer_heads. |
| */ |
| int fastcall set_page_dirty(struct page *page) |
| { |
| struct address_space *mapping = page_mapping(page); |
| |
| if (likely(mapping)) { |
| int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; |
| if (spd) |
| return (*spd)(page); |
| return __set_page_dirty_buffers(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. |
| */ |
| int test_clear_page_dirty(struct page *page) |
| { |
| struct address_space *mapping = page_mapping(page); |
| unsigned long flags; |
| |
| if (mapping) { |
| write_lock_irqsave(&mapping->tree_lock, flags); |
| if (TestClearPageDirty(page)) { |
| radix_tree_tag_clear(&mapping->page_tree, |
| page_index(page), |
| PAGECACHE_TAG_DIRTY); |
| if (mapping_cap_account_dirty(mapping)) |
| __dec_zone_page_state(page, NR_FILE_DIRTY); |
| write_unlock_irqrestore(&mapping->tree_lock, flags); |
| return 1; |
| } |
| write_unlock_irqrestore(&mapping->tree_lock, flags); |
| return 0; |
| } |
| return TestClearPageDirty(page); |
| } |
| EXPORT_SYMBOL(test_clear_page_dirty); |
| |
| /* |
| * 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); |
| |
| if (mapping) { |
| if (TestClearPageDirty(page)) { |
| if (mapping_cap_account_dirty(mapping)) |
| dec_zone_page_state(page, NR_FILE_DIRTY); |
| 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) { |
| unsigned long flags; |
| |
| write_lock_irqsave(&mapping->tree_lock, flags); |
| ret = TestClearPageWriteback(page); |
| if (ret) |
| radix_tree_tag_clear(&mapping->page_tree, |
| page_index(page), |
| PAGECACHE_TAG_WRITEBACK); |
| write_unlock_irqrestore(&mapping->tree_lock, flags); |
| } else { |
| ret = TestClearPageWriteback(page); |
| } |
| return ret; |
| } |
| |
| int test_set_page_writeback(struct page *page) |
| { |
| struct address_space *mapping = page_mapping(page); |
| int ret; |
| |
| if (mapping) { |
| unsigned long flags; |
| |
| write_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 (!PageDirty(page)) |
| radix_tree_tag_clear(&mapping->page_tree, |
| page_index(page), |
| PAGECACHE_TAG_DIRTY); |
| write_unlock_irqrestore(&mapping->tree_lock, flags); |
| } else { |
| ret = TestSetPageWriteback(page); |
| } |
| return ret; |
| |
| } |
| EXPORT_SYMBOL(test_set_page_writeback); |
| |
| /* |
| * Return true if any of the pages in the mapping are marged with the |
| * passed tag. |
| */ |
| int mapping_tagged(struct address_space *mapping, int tag) |
| { |
| unsigned long flags; |
| int ret; |
| |
| read_lock_irqsave(&mapping->tree_lock, flags); |
| ret = radix_tree_tagged(&mapping->page_tree, tag); |
| read_unlock_irqrestore(&mapping->tree_lock, flags); |
| return ret; |
| } |
| EXPORT_SYMBOL(mapping_tagged); |