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Diffstat (limited to 'mm/page-writeback.c')
| -rw-r--r-- | mm/page-writeback.c | 819 |
1 files changed, 819 insertions, 0 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c new file mode 100644 index 000000000000..6ddd6a29c73b --- /dev/null +++ b/mm/page-writeback.c @@ -0,0 +1,819 @@ +/* + * 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; /* 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 centiseconds + * (hundredths of a second) + */ +int dirty_writeback_centisecs = 5 * 100; + +/* + * The longest number of centiseconds for which data is allowed to remain dirty + */ +int dirty_expire_centisecs = 30 * 100; + +/* + * Flag that makes the machine dump writes/reads and block dirtyings. + */ +int block_dump; + +/* + * Flag that puts the machine in "laptop mode". + */ +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 = read_page_state(nr_dirty); + wbs->nr_unstable = read_page_state(nr_unstable); + wbs->nr_mapped = read_page_state(nr_mapped); + wbs->nr_writeback = read_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, + }; + + 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; + + 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 = 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 - balance dirty memory state + * @mapping - address_space which was 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(struct address_space *mapping) +{ + static DEFINE_PER_CPU(int, ratelimits) = 0; + long ratelimit; + + 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. + */ + if (get_cpu_var(ratelimits)++ >= ratelimit) { + __get_cpu_var(ratelimits) = 0; + put_cpu_var(ratelimits); + balance_dirty_pages(mapping); + return; + } + put_cpu_var(ratelimits); +} +EXPORT_SYMBOL(balance_dirty_pages_ratelimited); + +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, + }; + + 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_bdflush(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 struct timer_list wb_timer = + TIMER_INITIALIZER(wb_timer_fn, 0, 0); +static struct timer_list laptop_mode_wb_timer = + TIMER_INITIALIZER(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_centisecs. But if a writeback event + * takes longer than a dirty_writeback_centisecs 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, + }; + + sync_supers(); + + get_writeback_state(&wbs); + oldest_jif = jiffies - (dirty_expire_centisecs * HZ) / 100; + start_jif = jiffies; + next_jif = start_jif + (dirty_writeback_centisecs * HZ) / 100; + 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_centisecs) + 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(table, write, file, buffer, length, ppos); + if (dirty_writeback_centisecs) { + mod_timer(&wb_timer, + jiffies + (dirty_writeback_centisecs * HZ) / 100); + } 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 * HZ); +} + +/* + * 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 +ratelimit_handler(struct notifier_block *self, unsigned long u, void *v) +{ + set_ratelimit(); + return 0; +} + +static struct notifier_block 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_centisecs * HZ) / 100); + set_ratelimit(); + register_cpu_notifier(&ratelimit_nb); +} + +int do_writepages(struct address_space *mapping, struct writeback_control *wbc) +{ + if (wbc->nr_to_write <= 0) + return 0; + if (mapping->a_ops->writepages) + return mapping->a_ops->writepages(mapping, wbc); + return generic_writepages(mapping, wbc); +} + +/** + * 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) +{ + int ret = 0; + + 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_page_state(nr_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 ret; +} +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)) + SetPageDirty(page); + 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); + write_unlock_irqrestore(&mapping->tree_lock, flags); + if (mapping_cap_account_dirty(mapping)) + dec_page_state(nr_dirty); + 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_page_state(nr_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); |