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Diffstat (limited to 'fs/fs-writeback.c')
| -rw-r--r-- | fs/fs-writeback.c | 1398 |
1 files changed, 1398 insertions, 0 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c new file mode 100644 index 00000000..42a853ee --- /dev/null +++ b/fs/fs-writeback.c @@ -0,0 +1,1398 @@ +/* + * fs/fs-writeback.c + * + * Copyright (C) 2002, Linus Torvalds. + * + * Contains all the functions related to writing back and waiting + * upon dirty inodes against superblocks, and writing back dirty + * pages against inodes. ie: data writeback. Writeout of the + * inode itself is not handled here. + * + * 10Apr2002 Andrew Morton + * Split out of fs/inode.c + * Additions for address_space-based writeback + */ + +#include <linux/kernel.h> +#include <linux/export.h> +#include <linux/spinlock.h> +#include <linux/slab.h> +#include <linux/sched.h> +#include <linux/fs.h> +#include <linux/mm.h> +#include <linux/pagemap.h> +#include <linux/kthread.h> +#include <linux/freezer.h> +#include <linux/writeback.h> +#include <linux/blkdev.h> +#include <linux/backing-dev.h> +#include <linux/tracepoint.h> +#include "internal.h" + +/* + * 4MB minimal write chunk size + */ +#define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_CACHE_SHIFT - 10)) + +/* + * Passed into wb_writeback(), essentially a subset of writeback_control + */ +struct wb_writeback_work { + long nr_pages; + struct super_block *sb; + unsigned long *older_than_this; + enum writeback_sync_modes sync_mode; + unsigned int tagged_writepages:1; + unsigned int for_kupdate:1; + unsigned int range_cyclic:1; + unsigned int for_background:1; + enum wb_reason reason; /* why was writeback initiated? */ + + struct list_head list; /* pending work list */ + struct completion *done; /* set if the caller waits */ +}; + +/* + * We don't actually have pdflush, but this one is exported though /proc... + */ +int nr_pdflush_threads; + +/** + * writeback_in_progress - determine whether there is writeback in progress + * @bdi: the device's backing_dev_info structure. + * + * Determine whether there is writeback waiting to be handled against a + * backing device. + */ +int writeback_in_progress(struct backing_dev_info *bdi) +{ + return test_bit(BDI_writeback_running, &bdi->state); +} + +static inline struct backing_dev_info *inode_to_bdi(struct inode *inode) +{ + struct super_block *sb = inode->i_sb; + + if (strcmp(sb->s_type->name, "bdev") == 0) + return inode->i_mapping->backing_dev_info; + + return sb->s_bdi; +} + +static inline struct inode *wb_inode(struct list_head *head) +{ + return list_entry(head, struct inode, i_wb_list); +} + +/* + * Include the creation of the trace points after defining the + * wb_writeback_work structure and inline functions so that the definition + * remains local to this file. + */ +#define CREATE_TRACE_POINTS +#include <trace/events/writeback.h> + +/* Wakeup flusher thread or forker thread to fork it. Requires bdi->wb_lock. */ +static void bdi_wakeup_flusher(struct backing_dev_info *bdi) +{ + if (bdi->wb.task) { + wake_up_process(bdi->wb.task); + } else { + /* + * The bdi thread isn't there, wake up the forker thread which + * will create and run it. + */ + wake_up_process(default_backing_dev_info.wb.task); + } +} + +static void bdi_queue_work(struct backing_dev_info *bdi, + struct wb_writeback_work *work) +{ + trace_writeback_queue(bdi, work); + + spin_lock_bh(&bdi->wb_lock); + list_add_tail(&work->list, &bdi->work_list); + if (!bdi->wb.task) + trace_writeback_nothread(bdi, work); + bdi_wakeup_flusher(bdi); + spin_unlock_bh(&bdi->wb_lock); +} + +static void +__bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages, + bool range_cyclic, enum wb_reason reason) +{ + struct wb_writeback_work *work; + + /* + * This is WB_SYNC_NONE writeback, so if allocation fails just + * wakeup the thread for old dirty data writeback + */ + work = kzalloc(sizeof(*work), GFP_ATOMIC); + if (!work) { + if (bdi->wb.task) { + trace_writeback_nowork(bdi); + wake_up_process(bdi->wb.task); + } + return; + } + + work->sync_mode = WB_SYNC_NONE; + work->nr_pages = nr_pages; + work->range_cyclic = range_cyclic; + work->reason = reason; + + bdi_queue_work(bdi, work); +} + +/** + * bdi_start_writeback - start writeback + * @bdi: the backing device to write from + * @nr_pages: the number of pages to write + * @reason: reason why some writeback work was initiated + * + * Description: + * This does WB_SYNC_NONE opportunistic writeback. The IO is only + * started when this function returns, we make no guarantees on + * completion. Caller need not hold sb s_umount semaphore. + * + */ +void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages, + enum wb_reason reason) +{ + __bdi_start_writeback(bdi, nr_pages, true, reason); +} + +/** + * bdi_start_background_writeback - start background writeback + * @bdi: the backing device to write from + * + * Description: + * This makes sure WB_SYNC_NONE background writeback happens. When + * this function returns, it is only guaranteed that for given BDI + * some IO is happening if we are over background dirty threshold. + * Caller need not hold sb s_umount semaphore. + */ +void bdi_start_background_writeback(struct backing_dev_info *bdi) +{ + /* + * We just wake up the flusher thread. It will perform background + * writeback as soon as there is no other work to do. + */ + trace_writeback_wake_background(bdi); + spin_lock_bh(&bdi->wb_lock); + bdi_wakeup_flusher(bdi); + spin_unlock_bh(&bdi->wb_lock); +} + +/* + * Remove the inode from the writeback list it is on. + */ +void inode_wb_list_del(struct inode *inode) +{ + struct backing_dev_info *bdi = inode_to_bdi(inode); + + spin_lock(&bdi->wb.list_lock); + list_del_init(&inode->i_wb_list); + spin_unlock(&bdi->wb.list_lock); +} + +/* + * Redirty an inode: set its when-it-was dirtied timestamp and move it to the + * furthest end of its superblock's dirty-inode list. + * + * Before stamping the inode's ->dirtied_when, we check to see whether it is + * already the most-recently-dirtied inode on the b_dirty list. If that is + * the case then the inode must have been redirtied while it was being written + * out and we don't reset its dirtied_when. + */ +static void redirty_tail(struct inode *inode, struct bdi_writeback *wb) +{ + assert_spin_locked(&wb->list_lock); + if (!list_empty(&wb->b_dirty)) { + struct inode *tail; + + tail = wb_inode(wb->b_dirty.next); + if (time_before(inode->dirtied_when, tail->dirtied_when)) + inode->dirtied_when = jiffies; + } + list_move(&inode->i_wb_list, &wb->b_dirty); +} + +/* + * requeue inode for re-scanning after bdi->b_io list is exhausted. + */ +static void requeue_io(struct inode *inode, struct bdi_writeback *wb) +{ + assert_spin_locked(&wb->list_lock); + list_move(&inode->i_wb_list, &wb->b_more_io); +} + +static void inode_sync_complete(struct inode *inode) +{ + /* + * Prevent speculative execution through + * spin_unlock(&wb->list_lock); + */ + + smp_mb(); + wake_up_bit(&inode->i_state, __I_SYNC); +} + +static bool inode_dirtied_after(struct inode *inode, unsigned long t) +{ + bool ret = time_after(inode->dirtied_when, t); +#ifndef CONFIG_64BIT + /* + * For inodes being constantly redirtied, dirtied_when can get stuck. + * It _appears_ to be in the future, but is actually in distant past. + * This test is necessary to prevent such wrapped-around relative times + * from permanently stopping the whole bdi writeback. + */ + ret = ret && time_before_eq(inode->dirtied_when, jiffies); +#endif + return ret; +} + +/* + * Move expired (dirtied after work->older_than_this) dirty inodes from + * @delaying_queue to @dispatch_queue. + */ +static int move_expired_inodes(struct list_head *delaying_queue, + struct list_head *dispatch_queue, + struct wb_writeback_work *work) +{ + LIST_HEAD(tmp); + struct list_head *pos, *node; + struct super_block *sb = NULL; + struct inode *inode; + int do_sb_sort = 0; + int moved = 0; + + while (!list_empty(delaying_queue)) { + inode = wb_inode(delaying_queue->prev); + if (work->older_than_this && + inode_dirtied_after(inode, *work->older_than_this)) + break; + if (sb && sb != inode->i_sb) + do_sb_sort = 1; + sb = inode->i_sb; + list_move(&inode->i_wb_list, &tmp); + moved++; + } + + /* just one sb in list, splice to dispatch_queue and we're done */ + if (!do_sb_sort) { + list_splice(&tmp, dispatch_queue); + goto out; + } + + /* Move inodes from one superblock together */ + while (!list_empty(&tmp)) { + sb = wb_inode(tmp.prev)->i_sb; + list_for_each_prev_safe(pos, node, &tmp) { + inode = wb_inode(pos); + if (inode->i_sb == sb) + list_move(&inode->i_wb_list, dispatch_queue); + } + } +out: + return moved; +} + +/* + * Queue all expired dirty inodes for io, eldest first. + * Before + * newly dirtied b_dirty b_io b_more_io + * =============> gf edc BA + * After + * newly dirtied b_dirty b_io b_more_io + * =============> g fBAedc + * | + * +--> dequeue for IO + */ +static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work) +{ + int moved; + assert_spin_locked(&wb->list_lock); + list_splice_init(&wb->b_more_io, &wb->b_io); + moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, work); + trace_writeback_queue_io(wb, work, moved); +} + +static int write_inode(struct inode *inode, struct writeback_control *wbc) +{ + if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) + return inode->i_sb->s_op->write_inode(inode, wbc); + return 0; +} + +/* + * Wait for writeback on an inode to complete. + */ +static void inode_wait_for_writeback(struct inode *inode, + struct bdi_writeback *wb) +{ + DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC); + wait_queue_head_t *wqh; + + wqh = bit_waitqueue(&inode->i_state, __I_SYNC); + while (inode->i_state & I_SYNC) { + spin_unlock(&inode->i_lock); + spin_unlock(&wb->list_lock); + __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE); + spin_lock(&wb->list_lock); + spin_lock(&inode->i_lock); + } +} + +/* + * Write out an inode's dirty pages. Called under wb->list_lock and + * inode->i_lock. Either the caller has an active reference on the inode or + * the inode has I_WILL_FREE set. + * + * If `wait' is set, wait on the writeout. + * + * The whole writeout design is quite complex and fragile. We want to avoid + * starvation of particular inodes when others are being redirtied, prevent + * livelocks, etc. + */ +static int +writeback_single_inode(struct inode *inode, struct bdi_writeback *wb, + struct writeback_control *wbc) +{ + struct address_space *mapping = inode->i_mapping; + long nr_to_write = wbc->nr_to_write; + unsigned dirty; + int ret; + + assert_spin_locked(&wb->list_lock); + assert_spin_locked(&inode->i_lock); + + if (!atomic_read(&inode->i_count)) + WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING))); + else + WARN_ON(inode->i_state & I_WILL_FREE); + + if (inode->i_state & I_SYNC) { + /* + * If this inode is locked for writeback and we are not doing + * writeback-for-data-integrity, move it to b_more_io so that + * writeback can proceed with the other inodes on s_io. + * + * We'll have another go at writing back this inode when we + * completed a full scan of b_io. + */ + if (wbc->sync_mode != WB_SYNC_ALL) { + requeue_io(inode, wb); + trace_writeback_single_inode_requeue(inode, wbc, + nr_to_write); + return 0; + } + + /* + * It's a data-integrity sync. We must wait. + */ + inode_wait_for_writeback(inode, wb); + } + + BUG_ON(inode->i_state & I_SYNC); + + /* Set I_SYNC, reset I_DIRTY_PAGES */ + inode->i_state |= I_SYNC; + inode->i_state &= ~I_DIRTY_PAGES; + spin_unlock(&inode->i_lock); + spin_unlock(&wb->list_lock); + + ret = do_writepages(mapping, wbc); + + /* + * Make sure to wait on the data before writing out the metadata. + * This is important for filesystems that modify metadata on data + * I/O completion. + */ + if (wbc->sync_mode == WB_SYNC_ALL) { + int err = filemap_fdatawait(mapping); + if (ret == 0) + ret = err; + } + + /* + * Some filesystems may redirty the inode during the writeback + * due to delalloc, clear dirty metadata flags right before + * write_inode() + */ + spin_lock(&inode->i_lock); + dirty = inode->i_state & I_DIRTY; + inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC); + spin_unlock(&inode->i_lock); + /* Don't write the inode if only I_DIRTY_PAGES was set */ + if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) { + int err = write_inode(inode, wbc); + if (ret == 0) + ret = err; + } + + spin_lock(&wb->list_lock); + spin_lock(&inode->i_lock); + inode->i_state &= ~I_SYNC; + if (!(inode->i_state & I_FREEING)) { + /* + * Sync livelock prevention. Each inode is tagged and synced in + * one shot. If still dirty, it will be redirty_tail()'ed below. + * Update the dirty time to prevent enqueue and sync it again. + */ + if ((inode->i_state & I_DIRTY) && + (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)) + inode->dirtied_when = jiffies; + + if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) { + /* + * We didn't write back all the pages. nfs_writepages() + * sometimes bales out without doing anything. + */ + inode->i_state |= I_DIRTY_PAGES; + if (wbc->nr_to_write <= 0) { + /* + * slice used up: queue for next turn + */ + requeue_io(inode, wb); + } else { + /* + * Writeback blocked by something other than + * congestion. Delay the inode for some time to + * avoid spinning on the CPU (100% iowait) + * retrying writeback of the dirty page/inode + * that cannot be performed immediately. + */ + redirty_tail(inode, wb); + } + } else if (inode->i_state & I_DIRTY) { + /* + * Filesystems can dirty the inode during writeback + * operations, such as delayed allocation during + * submission or metadata updates after data IO + * completion. + */ + redirty_tail(inode, wb); + } else { + /* + * The inode is clean. At this point we either have + * a reference to the inode or it's on it's way out. + * No need to add it back to the LRU. + */ + list_del_init(&inode->i_wb_list); + } + } + inode_sync_complete(inode); + trace_writeback_single_inode(inode, wbc, nr_to_write); + return ret; +} + +static long writeback_chunk_size(struct backing_dev_info *bdi, + struct wb_writeback_work *work) +{ + long pages; + + /* + * WB_SYNC_ALL mode does livelock avoidance by syncing dirty + * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX + * here avoids calling into writeback_inodes_wb() more than once. + * + * The intended call sequence for WB_SYNC_ALL writeback is: + * + * wb_writeback() + * writeback_sb_inodes() <== called only once + * write_cache_pages() <== called once for each inode + * (quickly) tag currently dirty pages + * (maybe slowly) sync all tagged pages + */ + if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages) + pages = LONG_MAX; + else { + pages = min(bdi->avg_write_bandwidth / 2, + global_dirty_limit / DIRTY_SCOPE); + pages = min(pages, work->nr_pages); + pages = round_down(pages + MIN_WRITEBACK_PAGES, + MIN_WRITEBACK_PAGES); + } + + return pages; +} + +/* + * Write a portion of b_io inodes which belong to @sb. + * + * If @only_this_sb is true, then find and write all such + * inodes. Otherwise write only ones which go sequentially + * in reverse order. + * + * Return the number of pages and/or inodes written. + */ +static long writeback_sb_inodes(struct super_block *sb, + struct bdi_writeback *wb, + struct wb_writeback_work *work) +{ + struct writeback_control wbc = { + .sync_mode = work->sync_mode, + .tagged_writepages = work->tagged_writepages, + .for_kupdate = work->for_kupdate, + .for_background = work->for_background, + .range_cyclic = work->range_cyclic, + .range_start = 0, + .range_end = LLONG_MAX, + }; + unsigned long start_time = jiffies; + long write_chunk; + long wrote = 0; /* count both pages and inodes */ + + while (!list_empty(&wb->b_io)) { + struct inode *inode = wb_inode(wb->b_io.prev); + + if (inode->i_sb != sb) { + if (work->sb) { + /* + * We only want to write back data for this + * superblock, move all inodes not belonging + * to it back onto the dirty list. + */ + redirty_tail(inode, wb); + continue; + } + + /* + * The inode belongs to a different superblock. + * Bounce back to the caller to unpin this and + * pin the next superblock. + */ + break; + } + + /* + * Don't bother with new inodes or inodes beeing freed, first + * kind does not need peridic writeout yet, and for the latter + * kind writeout is handled by the freer. + */ + spin_lock(&inode->i_lock); + if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) { + spin_unlock(&inode->i_lock); + redirty_tail(inode, wb); + continue; + } + __iget(inode); + write_chunk = writeback_chunk_size(wb->bdi, work); + wbc.nr_to_write = write_chunk; + wbc.pages_skipped = 0; + + writeback_single_inode(inode, wb, &wbc); + + work->nr_pages -= write_chunk - wbc.nr_to_write; + wrote += write_chunk - wbc.nr_to_write; + if (!(inode->i_state & I_DIRTY)) + wrote++; + if (wbc.pages_skipped) { + /* + * writeback is not making progress due to locked + * buffers. Skip this inode for now. + */ + redirty_tail(inode, wb); + } + spin_unlock(&inode->i_lock); + spin_unlock(&wb->list_lock); + iput(inode); + cond_resched(); + spin_lock(&wb->list_lock); + /* + * bail out to wb_writeback() often enough to check + * background threshold and other termination conditions. + */ + if (wrote) { + if (time_is_before_jiffies(start_time + HZ / 10UL)) + break; + if (work->nr_pages <= 0) + break; + } + } + return wrote; +} + +static long __writeback_inodes_wb(struct bdi_writeback *wb, + struct wb_writeback_work *work) +{ + unsigned long start_time = jiffies; + long wrote = 0; + + while (!list_empty(&wb->b_io)) { + struct inode *inode = wb_inode(wb->b_io.prev); + struct super_block *sb = inode->i_sb; + + if (!grab_super_passive(sb)) { + /* + * grab_super_passive() may fail consistently due to + * s_umount being grabbed by someone else. Don't use + * requeue_io() to avoid busy retrying the inode/sb. + */ + redirty_tail(inode, wb); + continue; + } + wrote += writeback_sb_inodes(sb, wb, work); + drop_super(sb); + + /* refer to the same tests at the end of writeback_sb_inodes */ + if (wrote) { + if (time_is_before_jiffies(start_time + HZ / 10UL)) + break; + if (work->nr_pages <= 0) + break; + } + } + /* Leave any unwritten inodes on b_io */ + return wrote; +} + +long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages, + enum wb_reason reason) +{ + struct wb_writeback_work work = { + .nr_pages = nr_pages, + .sync_mode = WB_SYNC_NONE, + .range_cyclic = 1, + .reason = reason, + }; + + spin_lock(&wb->list_lock); + if (list_empty(&wb->b_io)) + queue_io(wb, &work); + __writeback_inodes_wb(wb, &work); + spin_unlock(&wb->list_lock); + + return nr_pages - work.nr_pages; +} + +static bool over_bground_thresh(struct backing_dev_info *bdi) +{ + unsigned long background_thresh, dirty_thresh; + + global_dirty_limits(&background_thresh, &dirty_thresh); + + if (global_page_state(NR_FILE_DIRTY) + + global_page_state(NR_UNSTABLE_NFS) > background_thresh) + return true; + + if (bdi_stat(bdi, BDI_RECLAIMABLE) > + bdi_dirty_limit(bdi, background_thresh)) + return true; + + return false; +} + +/* + * Called under wb->list_lock. If there are multiple wb per bdi, + * only the flusher working on the first wb should do it. + */ +static void wb_update_bandwidth(struct bdi_writeback *wb, + unsigned long start_time) +{ + __bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time); +} + +/* + * Explicit flushing or 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 long wb_writeback(struct bdi_writeback *wb, + struct wb_writeback_work *work) +{ + unsigned long wb_start = jiffies; + long nr_pages = work->nr_pages; + unsigned long oldest_jif; + struct inode *inode; + long progress; + + oldest_jif = jiffies; + work->older_than_this = &oldest_jif; + + spin_lock(&wb->list_lock); + for (;;) { + /* + * Stop writeback when nr_pages has been consumed + */ + if (work->nr_pages <= 0) + break; + + /* + * Background writeout and kupdate-style writeback may + * run forever. Stop them if there is other work to do + * so that e.g. sync can proceed. They'll be restarted + * after the other works are all done. + */ + if ((work->for_background || work->for_kupdate) && + !list_empty(&wb->bdi->work_list)) + break; + + /* + * For background writeout, stop when we are below the + * background dirty threshold + */ + if (work->for_background && !over_bground_thresh(wb->bdi)) + break; + + /* + * Kupdate and background works are special and we want to + * include all inodes that need writing. Livelock avoidance is + * handled by these works yielding to any other work so we are + * safe. + */ + if (work->for_kupdate) { + oldest_jif = jiffies - + msecs_to_jiffies(dirty_expire_interval * 10); + } else if (work->for_background) + oldest_jif = jiffies; + + trace_writeback_start(wb->bdi, work); + if (list_empty(&wb->b_io)) + queue_io(wb, work); + if (work->sb) + progress = writeback_sb_inodes(work->sb, wb, work); + else + progress = __writeback_inodes_wb(wb, work); + trace_writeback_written(wb->bdi, work); + + wb_update_bandwidth(wb, wb_start); + + /* + * Did we write something? Try for more + * + * Dirty inodes are moved to b_io for writeback in batches. + * The completion of the current batch does not necessarily + * mean the overall work is done. So we keep looping as long + * as made some progress on cleaning pages or inodes. + */ + if (progress) + continue; + /* + * No more inodes for IO, bail + */ + if (list_empty(&wb->b_more_io)) + break; + /* + * Nothing written. Wait for some inode to + * become available for writeback. Otherwise + * we'll just busyloop. + */ + if (!list_empty(&wb->b_more_io)) { + trace_writeback_wait(wb->bdi, work); + inode = wb_inode(wb->b_more_io.prev); + spin_lock(&inode->i_lock); + inode_wait_for_writeback(inode, wb); + spin_unlock(&inode->i_lock); + } + } + spin_unlock(&wb->list_lock); + + return nr_pages - work->nr_pages; +} + +/* + * Return the next wb_writeback_work struct that hasn't been processed yet. + */ +static struct wb_writeback_work * +get_next_work_item(struct backing_dev_info *bdi) +{ + struct wb_writeback_work *work = NULL; + + spin_lock_bh(&bdi->wb_lock); + if (!list_empty(&bdi->work_list)) { + work = list_entry(bdi->work_list.next, + struct wb_writeback_work, list); + list_del_init(&work->list); + } + spin_unlock_bh(&bdi->wb_lock); + return work; +} + +/* + * Add in the number of potentially dirty inodes, because each inode + * write can dirty pagecache in the underlying blockdev. + */ +static unsigned long get_nr_dirty_pages(void) +{ + return global_page_state(NR_FILE_DIRTY) + + global_page_state(NR_UNSTABLE_NFS) + + get_nr_dirty_inodes(); +} + +static long wb_check_background_flush(struct bdi_writeback *wb) +{ + if (over_bground_thresh(wb->bdi)) { + + struct wb_writeback_work work = { + .nr_pages = LONG_MAX, + .sync_mode = WB_SYNC_NONE, + .for_background = 1, + .range_cyclic = 1, + .reason = WB_REASON_BACKGROUND, + }; + + return wb_writeback(wb, &work); + } + + return 0; +} + +static long wb_check_old_data_flush(struct bdi_writeback *wb) +{ + unsigned long expired; + long nr_pages; + + /* + * When set to zero, disable periodic writeback + */ + if (!dirty_writeback_interval) + return 0; + + expired = wb->last_old_flush + + msecs_to_jiffies(dirty_writeback_interval * 10); + if (time_before(jiffies, expired)) + return 0; + + wb->last_old_flush = jiffies; + nr_pages = get_nr_dirty_pages(); + + if (nr_pages) { + struct wb_writeback_work work = { + .nr_pages = nr_pages, + .sync_mode = WB_SYNC_NONE, + .for_kupdate = 1, + .range_cyclic = 1, + .reason = WB_REASON_PERIODIC, + }; + + return wb_writeback(wb, &work); + } + + return 0; +} + +/* + * Retrieve work items and do the writeback they describe + */ +long wb_do_writeback(struct bdi_writeback *wb, int force_wait) +{ + struct backing_dev_info *bdi = wb->bdi; + struct wb_writeback_work *work; + long wrote = 0; + + set_bit(BDI_writeback_running, &wb->bdi->state); + while ((work = get_next_work_item(bdi)) != NULL) { + /* + * Override sync mode, in case we must wait for completion + * because this thread is exiting now. + */ + if (force_wait) + work->sync_mode = WB_SYNC_ALL; + + trace_writeback_exec(bdi, work); + + wrote += wb_writeback(wb, work); + + /* + * Notify the caller of completion if this is a synchronous + * work item, otherwise just free it. + */ + if (work->done) + complete(work->done); + else + kfree(work); + } + + /* + * Check for periodic writeback, kupdated() style + */ + wrote += wb_check_old_data_flush(wb); + wrote += wb_check_background_flush(wb); + clear_bit(BDI_writeback_running, &wb->bdi->state); + + return wrote; +} + +/* + * Handle writeback of dirty data for the device backed by this bdi. Also + * wakes up periodically and does kupdated style flushing. + */ +int bdi_writeback_thread(void *data) +{ + struct bdi_writeback *wb = data; + struct backing_dev_info *bdi = wb->bdi; + long pages_written; + + current->flags |= PF_SWAPWRITE; + set_freezable(); + wb->last_active = jiffies; + + /* + * Our parent may run at a different priority, just set us to normal + */ + set_user_nice(current, 0); + + trace_writeback_thread_start(bdi); + + while (!kthread_freezable_should_stop(NULL)) { + /* + * Remove own delayed wake-up timer, since we are already awake + * and we'll take care of the preriodic write-back. + */ + del_timer(&wb->wakeup_timer); + + pages_written = wb_do_writeback(wb, 0); + + trace_writeback_pages_written(pages_written); + + if (pages_written) + wb->last_active = jiffies; + + set_current_state(TASK_INTERRUPTIBLE); + if (!list_empty(&bdi->work_list) || kthread_should_stop()) { + __set_current_state(TASK_RUNNING); + continue; + } + + if (wb_has_dirty_io(wb) && dirty_writeback_interval) + schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10)); + else { + /* + * We have nothing to do, so can go sleep without any + * timeout and save power. When a work is queued or + * something is made dirty - we will be woken up. + */ + schedule(); + } + } + + /* Flush any work that raced with us exiting */ + if (!list_empty(&bdi->work_list)) + wb_do_writeback(wb, 1); + + trace_writeback_thread_stop(bdi); + return 0; +} + + +/* + * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back + * the whole world. + */ +void wakeup_flusher_threads(long nr_pages, enum wb_reason reason) +{ + struct backing_dev_info *bdi; + + if (!nr_pages) { + nr_pages = global_page_state(NR_FILE_DIRTY) + + global_page_state(NR_UNSTABLE_NFS); + } + + rcu_read_lock(); + list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) { + if (!bdi_has_dirty_io(bdi)) + continue; + __bdi_start_writeback(bdi, nr_pages, false, reason); + } + rcu_read_unlock(); +} + +static noinline void block_dump___mark_inode_dirty(struct inode *inode) +{ + if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) { + struct dentry *dentry; + const char *name = "?"; + + dentry = d_find_alias(inode); + if (dentry) { + spin_lock(&dentry->d_lock); + name = (const char *) dentry->d_name.name; + } + printk(KERN_DEBUG + "%s(%d): dirtied inode %lu (%s) on %s\n", + current->comm, task_pid_nr(current), inode->i_ino, + name, inode->i_sb->s_id); + if (dentry) { + spin_unlock(&dentry->d_lock); + dput(dentry); + } + } +} + +/** + * __mark_inode_dirty - internal function + * @inode: inode to mark + * @flags: what kind of dirty (i.e. I_DIRTY_SYNC) + * Mark an inode as dirty. Callers should use mark_inode_dirty or + * mark_inode_dirty_sync. + * + * Put the inode on the super block's dirty list. + * + * CAREFUL! We mark it dirty unconditionally, but move it onto the + * dirty list only if it is hashed or if it refers to a blockdev. + * If it was not hashed, it will never be added to the dirty list + * even if it is later hashed, as it will have been marked dirty already. + * + * In short, make sure you hash any inodes _before_ you start marking + * them dirty. + * + * Note that for blockdevs, inode->dirtied_when represents the dirtying time of + * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of + * the kernel-internal blockdev inode represents the dirtying time of the + * blockdev's pages. This is why for I_DIRTY_PAGES we always use + * page->mapping->host, so the page-dirtying time is recorded in the internal + * blockdev inode. + */ +void __mark_inode_dirty(struct inode *inode, int flags) +{ + struct super_block *sb = inode->i_sb; + struct backing_dev_info *bdi = NULL; + + /* + * Don't do this for I_DIRTY_PAGES - that doesn't actually + * dirty the inode itself + */ + if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) { + if (sb->s_op->dirty_inode) + sb->s_op->dirty_inode(inode, flags); + } + + /* + * make sure that changes are seen by all cpus before we test i_state + * -- mikulas + */ + smp_mb(); + + /* avoid the locking if we can */ + if ((inode->i_state & flags) == flags) + return; + + if (unlikely(block_dump > 1)) + block_dump___mark_inode_dirty(inode); + + spin_lock(&inode->i_lock); + if ((inode->i_state & flags) != flags) { + const int was_dirty = inode->i_state & I_DIRTY; + + inode->i_state |= flags; + + /* + * If the inode is being synced, just update its dirty state. + * The unlocker will place the inode on the appropriate + * superblock list, based upon its state. + */ + if (inode->i_state & I_SYNC) + goto out_unlock_inode; + + /* + * Only add valid (hashed) inodes to the superblock's + * dirty list. Add blockdev inodes as well. + */ + if (!S_ISBLK(inode->i_mode)) { + if (inode_unhashed(inode)) + goto out_unlock_inode; + } + if (inode->i_state & I_FREEING) + goto out_unlock_inode; + + /* + * If the inode was already on b_dirty/b_io/b_more_io, don't + * reposition it (that would break b_dirty time-ordering). + */ + if (!was_dirty) { + bool wakeup_bdi = false; + bdi = inode_to_bdi(inode); + + if (bdi_cap_writeback_dirty(bdi)) { + WARN(!test_bit(BDI_registered, &bdi->state), + "bdi-%s not registered\n", bdi->name); + + /* + * If this is the first dirty inode for this + * bdi, we have to wake-up the corresponding + * bdi thread to make sure background + * write-back happens later. + */ + if (!wb_has_dirty_io(&bdi->wb)) + wakeup_bdi = true; + } + + spin_unlock(&inode->i_lock); + spin_lock(&bdi->wb.list_lock); + inode->dirtied_when = jiffies; + list_move(&inode->i_wb_list, &bdi->wb.b_dirty); + spin_unlock(&bdi->wb.list_lock); + + if (wakeup_bdi) + bdi_wakeup_thread_delayed(bdi); + return; + } + } +out_unlock_inode: + spin_unlock(&inode->i_lock); + +} +EXPORT_SYMBOL(__mark_inode_dirty); + +static void wait_sb_inodes(struct super_block *sb) +{ + struct inode *inode, *old_inode = NULL; + + /* + * We need to be protected against the filesystem going from + * r/o to r/w or vice versa. + */ + WARN_ON(!rwsem_is_locked(&sb->s_umount)); + + spin_lock(&inode_sb_list_lock); + + /* + * Data integrity sync. Must wait for all pages under writeback, + * because there may have been pages dirtied before our sync + * call, but which had writeout started before we write it out. + * In which case, the inode may not be on the dirty list, but + * we still have to wait for that writeout. + */ + list_for_each_entry(inode, &sb->s_inodes, i_sb_list) { + struct address_space *mapping = inode->i_mapping; + + spin_lock(&inode->i_lock); + if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) || + (mapping->nrpages == 0)) { + spin_unlock(&inode->i_lock); + continue; + } + __iget(inode); + spin_unlock(&inode->i_lock); + spin_unlock(&inode_sb_list_lock); + + /* + * We hold a reference to 'inode' so it couldn't have been + * removed from s_inodes list while we dropped the + * inode_sb_list_lock. We cannot iput the inode now as we can + * be holding the last reference and we cannot iput it under + * inode_sb_list_lock. So we keep the reference and iput it + * later. + */ + iput(old_inode); + old_inode = inode; + + filemap_fdatawait(mapping); + + cond_resched(); + + spin_lock(&inode_sb_list_lock); + } + spin_unlock(&inode_sb_list_lock); + iput(old_inode); +} + +/** + * writeback_inodes_sb_nr - writeback dirty inodes from given super_block + * @sb: the superblock + * @nr: the number of pages to write + * @reason: reason why some writeback work initiated + * + * Start writeback on some inodes on this super_block. No guarantees are made + * on how many (if any) will be written, and this function does not wait + * for IO completion of submitted IO. + */ +void writeback_inodes_sb_nr(struct super_block *sb, + unsigned long nr, + enum wb_reason reason) +{ + DECLARE_COMPLETION_ONSTACK(done); + struct wb_writeback_work work = { + .sb = sb, + .sync_mode = WB_SYNC_NONE, + .tagged_writepages = 1, + .done = &done, + .nr_pages = nr, + .reason = reason, + }; + + WARN_ON(!rwsem_is_locked(&sb->s_umount)); + bdi_queue_work(sb->s_bdi, &work); + wait_for_completion(&done); +} +EXPORT_SYMBOL(writeback_inodes_sb_nr); + +/** + * writeback_inodes_sb - writeback dirty inodes from given super_block + * @sb: the superblock + * @reason: reason why some writeback work was initiated + * + * Start writeback on some inodes on this super_block. No guarantees are made + * on how many (if any) will be written, and this function does not wait + * for IO completion of submitted IO. + */ +void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason) +{ + return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason); +} +EXPORT_SYMBOL(writeback_inodes_sb); + +/** + * writeback_inodes_sb_if_idle - start writeback if none underway + * @sb: the superblock + * @reason: reason why some writeback work was initiated + * + * Invoke writeback_inodes_sb if no writeback is currently underway. + * Returns 1 if writeback was started, 0 if not. + */ +int writeback_inodes_sb_if_idle(struct super_block *sb, enum wb_reason reason) +{ + if (!writeback_in_progress(sb->s_bdi)) { + down_read(&sb->s_umount); + writeback_inodes_sb(sb, reason); + up_read(&sb->s_umount); + return 1; + } else + return 0; +} +EXPORT_SYMBOL(writeback_inodes_sb_if_idle); + +/** + * writeback_inodes_sb_nr_if_idle - start writeback if none underway + * @sb: the superblock + * @nr: the number of pages to write + * @reason: reason why some writeback work was initiated + * + * Invoke writeback_inodes_sb if no writeback is currently underway. + * Returns 1 if writeback was started, 0 if not. + */ +int writeback_inodes_sb_nr_if_idle(struct super_block *sb, + unsigned long nr, + enum wb_reason reason) +{ + if (!writeback_in_progress(sb->s_bdi)) { + down_read(&sb->s_umount); + writeback_inodes_sb_nr(sb, nr, reason); + up_read(&sb->s_umount); + return 1; + } else + return 0; +} +EXPORT_SYMBOL(writeback_inodes_sb_nr_if_idle); + +/** + * sync_inodes_sb - sync sb inode pages + * @sb: the superblock + * + * This function writes and waits on any dirty inode belonging to this + * super_block. + */ +void sync_inodes_sb(struct super_block *sb) +{ + DECLARE_COMPLETION_ONSTACK(done); + struct wb_writeback_work work = { + .sb = sb, + .sync_mode = WB_SYNC_ALL, + .nr_pages = LONG_MAX, + .range_cyclic = 0, + .done = &done, + .reason = WB_REASON_SYNC, + }; + + WARN_ON(!rwsem_is_locked(&sb->s_umount)); + + bdi_queue_work(sb->s_bdi, &work); + wait_for_completion(&done); + + wait_sb_inodes(sb); +} +EXPORT_SYMBOL(sync_inodes_sb); + +/** + * write_inode_now - write an inode to disk + * @inode: inode to write to disk + * @sync: whether the write should be synchronous or not + * + * This function commits an inode to disk immediately if it is dirty. This is + * primarily needed by knfsd. + * + * The caller must either have a ref on the inode or must have set I_WILL_FREE. + */ +int write_inode_now(struct inode *inode, int sync) +{ + struct bdi_writeback *wb = &inode_to_bdi(inode)->wb; + int ret; + struct writeback_control wbc = { + .nr_to_write = LONG_MAX, + .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE, + .range_start = 0, + .range_end = LLONG_MAX, + }; + + if (!mapping_cap_writeback_dirty(inode->i_mapping)) + wbc.nr_to_write = 0; + + might_sleep(); + spin_lock(&wb->list_lock); + spin_lock(&inode->i_lock); + ret = writeback_single_inode(inode, wb, &wbc); + spin_unlock(&inode->i_lock); + spin_unlock(&wb->list_lock); + return ret; +} +EXPORT_SYMBOL(write_inode_now); + +/** + * sync_inode - write an inode and its pages to disk. + * @inode: the inode to sync + * @wbc: controls the writeback mode + * + * sync_inode() will write an inode and its pages to disk. It will also + * correctly update the inode on its superblock's dirty inode lists and will + * update inode->i_state. + * + * The caller must have a ref on the inode. + */ +int sync_inode(struct inode *inode, struct writeback_control *wbc) +{ + struct bdi_writeback *wb = &inode_to_bdi(inode)->wb; + int ret; + + spin_lock(&wb->list_lock); + spin_lock(&inode->i_lock); + ret = writeback_single_inode(inode, wb, wbc); + spin_unlock(&inode->i_lock); + spin_unlock(&wb->list_lock); + return ret; +} +EXPORT_SYMBOL(sync_inode); + +/** + * sync_inode_metadata - write an inode to disk + * @inode: the inode to sync + * @wait: wait for I/O to complete. + * + * Write an inode to disk and adjust its dirty state after completion. + * + * Note: only writes the actual inode, no associated data or other metadata. + */ +int sync_inode_metadata(struct inode *inode, int wait) +{ + struct writeback_control wbc = { + .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE, + .nr_to_write = 0, /* metadata-only */ + }; + + return sync_inode(inode, &wbc); +} +EXPORT_SYMBOL(sync_inode_metadata); |