zte's code,first commit
Change-Id: I9a04da59e459a9bc0d67f101f700d9d7dc8d681b
diff --git a/ap/os/linux/linux-3.4.x/fs/fs-writeback.c b/ap/os/linux/linux-3.4.x/fs/fs-writeback.c
new file mode 100644
index 0000000..6ba6b1f
--- /dev/null
+++ b/ap/os/linux/linux-3.4.x/fs/fs-writeback.c
@@ -0,0 +1,1421 @@
+/*
+ * 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 */
+ unsigned int nr_writeback;
+ unsigned int nr_free;
+ unsigned int nr_pagecache;
+};
+
+/*
+ * 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);
+}
+EXPORT_SYMBOL(writeback_in_progress);
+
+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;
+ work->nr_writeback = global_page_state(NR_WRITEBACK);
+ work->nr_free = global_page_state(NR_FREE_PAGES);
+ work->nr_pagecache = global_page_state(NR_FILE_PAGES);
+
+ 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;
+ 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;
+
+ /*
+ * Paired with smp_mb() in __mark_inode_dirty(). This allows
+ * __mark_inode_dirty() to test i_state without grabbing i_lock -
+ * either they see the I_DIRTY bits cleared or we see the dirtied
+ * inode.
+ *
+ * I_DIRTY_PAGES is always cleared together above even if @mapping
+ * still has dirty pages. The flag is reinstated after smp_mb() if
+ * necessary. This guarantees that either __mark_inode_dirty()
+ * sees clear I_DIRTY_PAGES or we see PAGECACHE_TAG_DIRTY.
+ */
+ smp_mb();
+
+ if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
+ inode->i_state |= I_DIRTY_PAGES;
+
+ 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.
+ */
+ 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);
+ }
+
+ /*
+ * Paired with smp_mb() in __writeback_single_inode() for the
+ * following lockless i_state test. See there for details.
+ */
+ smp_mb();
+
+ 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);