+#define inode_to_bdi(inode) ((inode)->i_mapping->backing_dev_info)
+
+/*
+ * We don't actually have pdflush, but this one is exported though /proc...
+ */
+int nr_pdflush_threads;
+
+/*
+ * Passed into wb_writeback(), essentially a subset of writeback_control
+ */
+struct wb_writeback_args {
+ long nr_pages;
+ struct super_block *sb;
+ enum writeback_sync_modes sync_mode;
+ int for_kupdate:1;
+ int range_cyclic:1;
+ int for_background:1;
+};
+
+/*
+ * Work items for the bdi_writeback threads
+ */
+struct bdi_work {
+ struct list_head list; /* pending work list */
+ struct rcu_head rcu_head; /* for RCU free/clear of work */
+
+ unsigned long seen; /* threads that have seen this work */
+ atomic_t pending; /* number of threads still to do work */
+
+ struct wb_writeback_args args; /* writeback arguments */
+
+ unsigned long state; /* flag bits, see WS_* */
+};
+
+enum {
+ WS_USED_B = 0,
+ WS_ONSTACK_B,
+};
+
+#define WS_USED (1 << WS_USED_B)
+#define WS_ONSTACK (1 << WS_ONSTACK_B)
+
+static inline bool bdi_work_on_stack(struct bdi_work *work)
+{
+ return test_bit(WS_ONSTACK_B, &work->state);
+}
+
+static inline void bdi_work_init(struct bdi_work *work,
+ struct wb_writeback_args *args)
+{
+ INIT_RCU_HEAD(&work->rcu_head);
+ work->args = *args;
+ work->state = WS_USED;
+}
+
+/**
+ * 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 !list_empty(&bdi->work_list);
+}
+
+static void bdi_work_clear(struct bdi_work *work)
+{
+ clear_bit(WS_USED_B, &work->state);
+ smp_mb__after_clear_bit();
+ /*
+ * work can have disappeared at this point. bit waitq functions
+ * should be able to tolerate this, provided bdi_sched_wait does
+ * not dereference it's pointer argument.
+ */
+ wake_up_bit(&work->state, WS_USED_B);
+}
+
+static void bdi_work_free(struct rcu_head *head)
+{
+ struct bdi_work *work = container_of(head, struct bdi_work, rcu_head);
+
+ if (!bdi_work_on_stack(work))
+ kfree(work);
+ else
+ bdi_work_clear(work);
+}
+
+static void wb_work_complete(struct bdi_work *work)
+{
+ const enum writeback_sync_modes sync_mode = work->args.sync_mode;
+ int onstack = bdi_work_on_stack(work);
+
+ /*
+ * For allocated work, we can clear the done/seen bit right here.
+ * For on-stack work, we need to postpone both the clear and free
+ * to after the RCU grace period, since the stack could be invalidated
+ * as soon as bdi_work_clear() has done the wakeup.
+ */
+ if (!onstack)
+ bdi_work_clear(work);
+ if (sync_mode == WB_SYNC_NONE || onstack)
+ call_rcu(&work->rcu_head, bdi_work_free);
+}
+
+static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work)
+{
+ /*
+ * The caller has retrieved the work arguments from this work,
+ * drop our reference. If this is the last ref, delete and free it
+ */
+ if (atomic_dec_and_test(&work->pending)) {
+ struct backing_dev_info *bdi = wb->bdi;
+
+ spin_lock(&bdi->wb_lock);
+ list_del_rcu(&work->list);
+ spin_unlock(&bdi->wb_lock);
+
+ wb_work_complete(work);
+ }
+}
+
+static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
+{
+ work->seen = bdi->wb_mask;
+ BUG_ON(!work->seen);
+ atomic_set(&work->pending, bdi->wb_cnt);
+ BUG_ON(!bdi->wb_cnt);
+
+ /*
+ * list_add_tail_rcu() contains the necessary barriers to
+ * make sure the above stores are seen before the item is
+ * noticed on the list
+ */
+ spin_lock(&bdi->wb_lock);
+ list_add_tail_rcu(&work->list, &bdi->work_list);
+ spin_unlock(&bdi->wb_lock);
+
+ /*
+ * If the default thread isn't there, make sure we add it. When
+ * it gets created and wakes up, we'll run this work.
+ */
+ if (unlikely(list_empty_careful(&bdi->wb_list)))
+ wake_up_process(default_backing_dev_info.wb.task);
+ else {
+ struct bdi_writeback *wb = &bdi->wb;
+
+ if (wb->task)
+ wake_up_process(wb->task);
+ }
+}
+
+/*
+ * Used for on-stack allocated work items. The caller needs to wait until
+ * the wb threads have acked the work before it's safe to continue.
+ */
+static void bdi_wait_on_work_clear(struct bdi_work *work)
+{
+ wait_on_bit(&work->state, WS_USED_B, bdi_sched_wait,
+ TASK_UNINTERRUPTIBLE);
+}
+
+static void bdi_alloc_queue_work(struct backing_dev_info *bdi,
+ struct wb_writeback_args *args)
+{
+ struct bdi_work *work;
+
+ /*
+ * This is WB_SYNC_NONE writeback, so if allocation fails just
+ * wakeup the thread for old dirty data writeback
+ */
+ work = kmalloc(sizeof(*work), GFP_ATOMIC);
+ if (work) {
+ bdi_work_init(work, args);
+ bdi_queue_work(bdi, work);
+ } else {
+ struct bdi_writeback *wb = &bdi->wb;
+
+ if (wb->task)
+ wake_up_process(wb->task);
+ }
+}
+
+/**
+ * bdi_sync_writeback - start and wait for writeback
+ * @bdi: the backing device to write from
+ * @sb: write inodes from this super_block
+ *
+ * Description:
+ * This does WB_SYNC_ALL data integrity writeback and waits for the
+ * IO to complete. Callers must hold the sb s_umount semaphore for
+ * reading, to avoid having the super disappear before we are done.
+ */
+static void bdi_sync_writeback(struct backing_dev_info *bdi,
+ struct super_block *sb)
+{
+ struct wb_writeback_args args = {
+ .sb = sb,
+ .sync_mode = WB_SYNC_ALL,
+ .nr_pages = LONG_MAX,
+ .range_cyclic = 0,
+ };
+ struct bdi_work work;
+
+ bdi_work_init(&work, &args);
+ work.state |= WS_ONSTACK;
+
+ bdi_queue_work(bdi, &work);
+ bdi_wait_on_work_clear(&work);
+}
+
+/**
+ * bdi_start_writeback - start writeback
+ * @bdi: the backing device to write from
+ * @sb: write inodes from this super_block
+ * @nr_pages: the number of pages to write
+ *
+ * Description:
+ * This does WB_SYNC_NONE opportunistic writeback. The IO is only
+ * started when this function returns, we make no guarentees on
+ * completion. Caller need not hold sb s_umount semaphore.
+ *
+ */
+void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
+ long nr_pages)
+{
+ struct wb_writeback_args args = {
+ .sb = sb,
+ .sync_mode = WB_SYNC_NONE,
+ .nr_pages = nr_pages,
+ .range_cyclic = 1,
+ };
+
+ /*
+ * We treat @nr_pages=0 as the special case to do background writeback,
+ * ie. to sync pages until the background dirty threshold is reached.
+ */
+ if (!nr_pages) {
+ args.nr_pages = LONG_MAX;
+ args.for_background = 1;
+ }
+
+ bdi_alloc_queue_work(bdi, &args);
+}
+
+/*
+ * 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 = &inode_to_bdi(inode)->wb;
+
+ if (!list_empty(&wb->b_dirty)) {
+ struct inode *tail;
+
+ tail = list_entry(wb->b_dirty.next, struct inode, i_list);
+ if (time_before(inode->dirtied_when, tail->dirtied_when))
+ inode->dirtied_when = jiffies;
+ }
+ list_move(&inode->i_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 = &inode_to_bdi(inode)->wb;
+
+ list_move(&inode->i_list, &wb->b_more_io);
+}
+
+static void inode_sync_complete(struct inode *inode)
+{
+ /*
+ * Prevent speculative execution through spin_unlock(&inode_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 dirty inodes from @delaying_queue to @dispatch_queue.
+ */
+static void move_expired_inodes(struct list_head *delaying_queue,
+ struct list_head *dispatch_queue,
+ unsigned long *older_than_this)
+{
+ LIST_HEAD(tmp);
+ struct list_head *pos, *node;
+ struct super_block *sb = NULL;
+ struct inode *inode;
+ int do_sb_sort = 0;
+
+ while (!list_empty(delaying_queue)) {
+ inode = list_entry(delaying_queue->prev, struct inode, i_list);
+ if (older_than_this &&
+ inode_dirtied_after(inode, *older_than_this))
+ break;
+ if (sb && sb != inode->i_sb)
+ do_sb_sort = 1;
+ sb = inode->i_sb;
+ list_move(&inode->i_list, &tmp);
+ }
+
+ /* just one sb in list, splice to dispatch_queue and we're done */
+ if (!do_sb_sort) {
+ list_splice(&tmp, dispatch_queue);
+ return;
+ }
+
+ /* Move inodes from one superblock together */
+ while (!list_empty(&tmp)) {
+ inode = list_entry(tmp.prev, struct inode, i_list);
+ sb = inode->i_sb;
+ list_for_each_prev_safe(pos, node, &tmp) {
+ inode = list_entry(pos, struct inode, i_list);
+ if (inode->i_sb == sb)
+ list_move(&inode->i_list, dispatch_queue);
+ }
+ }
+}
+
+/*
+ * Queue all expired dirty inodes for io, eldest first.
+ */
+static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
+{
+ list_splice_init(&wb->b_more_io, wb->b_io.prev);
+ move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);
+}
+
+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)
+{
+ DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
+ wait_queue_head_t *wqh;
+
+ wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
+ do {
+ spin_unlock(&inode_lock);
+ __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
+ spin_lock(&inode_lock);
+ } while (inode->i_state & I_SYNC);
+}
+
+/*
+ * Write out an inode's dirty pages. Called under inode_lock. Either the
+ * caller has ref on the inode (either via __iget or via syscall against an fd)
+ * or the inode has I_WILL_FREE set (via generic_forget_inode)
+ *
+ * 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.
+ *
+ * Called under inode_lock.
+ */
+static int
+writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
+{
+ struct address_space *mapping = inode->i_mapping;
+ unsigned dirty;
+ int ret;
+
+ 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);
+ return 0;
+ }
+
+ /*
+ * It's a data-integrity sync. We must wait.
+ */
+ inode_wait_for_writeback(inode);
+ }
+
+ BUG_ON(inode->i_state & I_SYNC);
+
+ /* Set I_SYNC, reset I_DIRTY */
+ dirty = inode->i_state & I_DIRTY;
+ inode->i_state |= I_SYNC;
+ inode->i_state &= ~I_DIRTY;
+
+ spin_unlock(&inode_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;
+ }
+
+ /* 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(&inode_lock);
+ inode->i_state &= ~I_SYNC;
+ if (!(inode->i_state & (I_FREEING | I_CLEAR))) {
+ if ((inode->i_state & I_DIRTY_PAGES) && wbc->for_kupdate) {
+ /*
+ * More pages get dirtied by a fast dirtier.
+ */
+ goto select_queue;
+ } else if (inode->i_state & I_DIRTY) {
+ /*
+ * At least XFS will redirty the inode during the
+ * writeback (delalloc) and on io completion (isize).
+ */
+ redirty_tail(inode);
+ } else if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
+ /*
+ * We didn't write back all the pages. nfs_writepages()
+ * sometimes bales out without doing anything. Redirty
+ * the inode; Move it from b_io onto b_more_io/b_dirty.
+ */
+ /*
+ * akpm: if the caller was the kupdate function we put
+ * this inode at the head of b_dirty so it gets first
+ * consideration. Otherwise, move it to the tail, for
+ * the reasons described there. I'm not really sure
+ * how much sense this makes. Presumably I had a good
+ * reasons for doing it this way, and I'd rather not
+ * muck with it at present.
+ */
+ if (wbc->for_kupdate) {
+ /*
+ * For the kupdate function we move the inode
+ * to b_more_io so it will get more writeout as
+ * soon as the queue becomes uncongested.
+ */
+ inode->i_state |= I_DIRTY_PAGES;
+select_queue:
+ if (wbc->nr_to_write <= 0) {
+ /*
+ * slice used up: queue for next turn
+ */
+ requeue_io(inode);
+ } else {
+ /*
+ * somehow blocked: retry later
+ */
+ redirty_tail(inode);
+ }
+ } else {
+ /*
+ * Otherwise fully redirty the inode so that
+ * other inodes on this superblock will get some
+ * writeout. Otherwise heavy writing to one
+ * file would indefinitely suspend writeout of
+ * all the other files.
+ */
+ inode->i_state |= I_DIRTY_PAGES;
+ redirty_tail(inode);
+ }
+ } else if (atomic_read(&inode->i_count)) {
+ /*
+ * The inode is clean, inuse
+ */
+ list_move(&inode->i_list, &inode_in_use);
+ } else {
+ /*
+ * The inode is clean, unused
+ */
+ list_move(&inode->i_list, &inode_unused);
+ }
+ }
+ inode_sync_complete(inode);
+ return ret;
+}
+
+static void unpin_sb_for_writeback(struct super_block *sb)
+{
+ up_read(&sb->s_umount);
+ put_super(sb);
+}
+
+enum sb_pin_state {
+ SB_PINNED,
+ SB_NOT_PINNED,
+ SB_PIN_FAILED
+};
+
+/*
+ * For WB_SYNC_NONE writeback, the caller does not have the sb pinned
+ * before calling writeback. So make sure that we do pin it, so it doesn't
+ * go away while we are writing inodes from it.
+ */
+static enum sb_pin_state pin_sb_for_writeback(struct writeback_control *wbc,
+ struct super_block *sb)
+{
+ /*
+ * Caller must already hold the ref for this
+ */
+ if (wbc->sync_mode == WB_SYNC_ALL) {
+ WARN_ON(!rwsem_is_locked(&sb->s_umount));
+ return SB_NOT_PINNED;
+ }
+ spin_lock(&sb_lock);
+ sb->s_count++;
+ if (down_read_trylock(&sb->s_umount)) {
+ if (sb->s_root) {
+ spin_unlock(&sb_lock);
+ return SB_PINNED;
+ }
+ /*
+ * umounted, drop rwsem again and fall through to failure
+ */
+ up_read(&sb->s_umount);
+ }
+ sb->s_count--;
+ spin_unlock(&sb_lock);
+ return SB_PIN_FAILED;
+}
+
+/*
+ * Write a portion of b_io inodes which belong to @sb.
+ * If @wbc->sb != NULL, then find and write all such
+ * inodes. Otherwise write only ones which go sequentially
+ * in reverse order.
+ * Return 1, if the caller writeback routine should be
+ * interrupted. Otherwise return 0.
+ */
+static int writeback_sb_inodes(struct super_block *sb,
+ struct bdi_writeback *wb,
+ struct writeback_control *wbc)
+{
+ while (!list_empty(&wb->b_io)) {
+ long pages_skipped;
+ struct inode *inode = list_entry(wb->b_io.prev,
+ struct inode, i_list);
+ if (wbc->sb && sb != inode->i_sb) {
+ /* super block given and doesn't
+ match, skip this inode */
+ redirty_tail(inode);
+ continue;
+ }
+ if (sb != inode->i_sb)
+ /* finish with this superblock */
+ return 0;
+ if (inode->i_state & (I_NEW | I_WILL_FREE)) {
+ requeue_io(inode);
+ continue;
+ }
+ /*
+ * Was this inode dirtied after sync_sb_inodes was called?
+ * This keeps sync from extra jobs and livelock.
+ */
+ if (inode_dirtied_after(inode, wbc->wb_start))
+ return 1;
+
+ BUG_ON(inode->i_state & (I_FREEING | I_CLEAR));
+ __iget(inode);
+ pages_skipped = wbc->pages_skipped;
+ writeback_single_inode(inode, wbc);
+ if (wbc->pages_skipped != pages_skipped) {
+ /*
+ * writeback is not making progress due to locked
+ * buffers. Skip this inode for now.
+ */
+ redirty_tail(inode);
+ }
+ spin_unlock(&inode_lock);
+ iput(inode);
+ cond_resched();
+ spin_lock(&inode_lock);
+ if (wbc->nr_to_write <= 0) {
+ wbc->more_io = 1;
+ return 1;
+ }
+ if (!list_empty(&wb->b_more_io))
+ wbc->more_io = 1;
+ }
+ /* b_io is empty */
+ return 1;
+}
+
+static void writeback_inodes_wb(struct bdi_writeback *wb,
+ struct writeback_control *wbc)
+{
+ int ret = 0;
+
+ wbc->wb_start = jiffies; /* livelock avoidance */
+ spin_lock(&inode_lock);
+ if (!wbc->for_kupdate || list_empty(&wb->b_io))
+ queue_io(wb, wbc->older_than_this);
+
+ while (!list_empty(&wb->b_io)) {
+ struct inode *inode = list_entry(wb->b_io.prev,
+ struct inode, i_list);
+ struct super_block *sb = inode->i_sb;
+ enum sb_pin_state state;
+
+ if (wbc->sb && sb != wbc->sb) {
+ /* super block given and doesn't
+ match, skip this inode */
+ redirty_tail(inode);
+ continue;
+ }
+ state = pin_sb_for_writeback(wbc, sb);
+
+ if (state == SB_PIN_FAILED) {
+ requeue_io(inode);
+ continue;
+ }
+ ret = writeback_sb_inodes(sb, wb, wbc);
+
+ if (state == SB_PINNED)
+ unpin_sb_for_writeback(sb);
+ if (ret)
+ break;
+ }
+ spin_unlock(&inode_lock);
+ /* Leave any unwritten inodes on b_io */
+}
+
+void writeback_inodes_wbc(struct writeback_control *wbc)
+{
+ struct backing_dev_info *bdi = wbc->bdi;
+
+ writeback_inodes_wb(&bdi->wb, wbc);
+}
+
+/*
+ * The maximum number of pages to writeout in a single bdi flush/kupdate
+ * operation. We do this so we don't hold I_SYNC 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
+
+static inline bool over_bground_thresh(void)
+{
+ unsigned long background_thresh, dirty_thresh;
+
+ get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL);
+
+ return (global_page_state(NR_FILE_DIRTY) +
+ global_page_state(NR_UNSTABLE_NFS) >= background_thresh);
+}
+
+/*
+ * 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_args *args)
+{
+ struct writeback_control wbc = {
+ .bdi = wb->bdi,
+ .sb = args->sb,
+ .sync_mode = args->sync_mode,
+ .older_than_this = NULL,
+ .for_kupdate = args->for_kupdate,
+ .for_background = args->for_background,
+ .range_cyclic = args->range_cyclic,
+ };
+ unsigned long oldest_jif;
+ long wrote = 0;
+ struct inode *inode;
+
+ if (wbc.for_kupdate) {
+ wbc.older_than_this = &oldest_jif;
+ oldest_jif = jiffies -
+ msecs_to_jiffies(dirty_expire_interval * 10);
+ }
+ if (!wbc.range_cyclic) {
+ wbc.range_start = 0;
+ wbc.range_end = LLONG_MAX;
+ }
+
+ for (;;) {
+ /*
+ * Stop writeback when nr_pages has been consumed
+ */
+ if (args->nr_pages <= 0)
+ break;
+
+ /*
+ * For background writeout, stop when we are below the
+ * background dirty threshold
+ */
+ if (args->for_background && !over_bground_thresh())
+ break;
+
+ wbc.more_io = 0;
+ wbc.nr_to_write = MAX_WRITEBACK_PAGES;
+ wbc.pages_skipped = 0;
+ writeback_inodes_wb(wb, &wbc);
+ args->nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
+ wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;
+
+ /*
+ * If we consumed everything, see if we have more
+ */
+ if (wbc.nr_to_write <= 0)
+ continue;
+ /*
+ * Didn't write everything and we don't have more IO, bail
+ */
+ if (!wbc.more_io)
+ break;
+ /*
+ * Did we write something? Try for more
+ */
+ if (wbc.nr_to_write < MAX_WRITEBACK_PAGES)
+ continue;
+ /*
+ * Nothing written. Wait for some inode to
+ * become available for writeback. Otherwise
+ * we'll just busyloop.
+ */
+ spin_lock(&inode_lock);
+ if (!list_empty(&wb->b_more_io)) {
+ inode = list_entry(wb->b_more_io.prev,
+ struct inode, i_list);
+ inode_wait_for_writeback(inode);
+ }
+ spin_unlock(&inode_lock);
+ }
+
+ return wrote;
+}
+
+/*
+ * Return the next bdi_work struct that hasn't been processed by this
+ * wb thread yet. ->seen is initially set for each thread that exists
+ * for this device, when a thread first notices a piece of work it
+ * clears its bit. Depending on writeback type, the thread will notify
+ * completion on either receiving the work (WB_SYNC_NONE) or after
+ * it is done (WB_SYNC_ALL).
+ */
+static struct bdi_work *get_next_work_item(struct backing_dev_info *bdi,
+ struct bdi_writeback *wb)
+{
+ struct bdi_work *work, *ret = NULL;
+
+ rcu_read_lock();
+
+ list_for_each_entry_rcu(work, &bdi->work_list, list) {
+ if (!test_bit(wb->nr, &work->seen))
+ continue;
+ clear_bit(wb->nr, &work->seen);
+
+ ret = work;
+ break;
+ }
+
+ rcu_read_unlock();
+ return ret;
+}
+
+static long wb_check_old_data_flush(struct bdi_writeback *wb)
+{
+ unsigned long expired;
+ long nr_pages;
+
+ 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 = global_page_state(NR_FILE_DIRTY) +
+ global_page_state(NR_UNSTABLE_NFS) +
+ (inodes_stat.nr_inodes - inodes_stat.nr_unused);
+
+ if (nr_pages) {
+ struct wb_writeback_args args = {
+ .nr_pages = nr_pages,
+ .sync_mode = WB_SYNC_NONE,
+ .for_kupdate = 1,
+ .range_cyclic = 1,
+ };
+
+ return wb_writeback(wb, &args);
+ }
+
+ 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 bdi_work *work;
+ long wrote = 0;
+
+ while ((work = get_next_work_item(bdi, wb)) != NULL) {
+ struct wb_writeback_args args = work->args;
+
+ /*
+ * Override sync mode, in case we must wait for completion
+ */
+ if (force_wait)
+ work->args.sync_mode = args.sync_mode = WB_SYNC_ALL;
+
+ /*
+ * If this isn't a data integrity operation, just notify
+ * that we have seen this work and we are now starting it.
+ */
+ if (args.sync_mode == WB_SYNC_NONE)
+ wb_clear_pending(wb, work);
+
+ wrote += wb_writeback(wb, &args);
+
+ /*
+ * This is a data integrity writeback, so only do the
+ * notification when we have completed the work.
+ */
+ if (args.sync_mode == WB_SYNC_ALL)
+ wb_clear_pending(wb, work);
+ }
+
+ /*
+ * Check for periodic writeback, kupdated() style
+ */
+ wrote += wb_check_old_data_flush(wb);
+
+ 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_task(struct bdi_writeback *wb)
+{
+ unsigned long last_active = jiffies;
+ unsigned long wait_jiffies = -1UL;
+ long pages_written;
+
+ while (!kthread_should_stop()) {
+ pages_written = wb_do_writeback(wb, 0);
+
+ if (pages_written)
+ last_active = jiffies;
+ else if (wait_jiffies != -1UL) {
+ unsigned long max_idle;
+
+ /*
+ * Longest period of inactivity that we tolerate. If we
+ * see dirty data again later, the task will get
+ * recreated automatically.
+ */
+ max_idle = max(5UL * 60 * HZ, wait_jiffies);
+ if (time_after(jiffies, max_idle + last_active))
+ break;
+ }
+
+ wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
+ schedule_timeout_interruptible(wait_jiffies);
+ try_to_freeze();
+ }
+
+ return 0;
+}
+
+/*
+ * Schedule writeback for all backing devices. This does WB_SYNC_NONE
+ * writeback, for integrity writeback see bdi_sync_writeback().
+ */
+static void bdi_writeback_all(struct super_block *sb, long nr_pages)
+{
+ struct wb_writeback_args args = {
+ .sb = sb,
+ .nr_pages = nr_pages,
+ .sync_mode = WB_SYNC_NONE,
+ };
+ struct backing_dev_info *bdi;
+
+ rcu_read_lock();
+
+ list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
+ if (!bdi_has_dirty_io(bdi))
+ continue;
+
+ bdi_alloc_queue_work(bdi, &args);
+ }
+
+ rcu_read_unlock();
+}
+
+/*
+ * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
+ * the whole world.
+ */
+void wakeup_flusher_threads(long nr_pages)
+{
+ if (nr_pages == 0)
+ nr_pages = global_page_state(NR_FILE_DIRTY) +
+ global_page_state(NR_UNSTABLE_NFS);
+ bdi_writeback_all(NULL, nr_pages);
+}
+
+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);
+ }
+ }
+}