- 根目录:
- fs
- fs-writeback.c
/*
* 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/module.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/writeback.h>
#include <linux/blkdev.h>
#include <linux/backing-dev.h>
#include <linux/buffer_head.h>
#include <linux/tracepoint.h>
#include "internal.h"
/*
* Passed into wb_writeback(), essentially a subset of writeback_control
*/
struct wb_writeback_work {
long nr_pages;
struct super_block *sb;
enum writeback_sync_modes sync_mode;
unsigned int for_kupdate:1;
unsigned int range_cyclic:1;
unsigned int for_background:1;
struct list_head list; /* pending work list */
struct completion *done; /* set if the caller waits */
};
/*
* Include the creation of the trace points after defining the
* wb_writeback_work structure so that the definition remains local to this
* file.
*/
#define CREATE_TRACE_POINTS
#include <trace/events/writeback.h>
/*
* 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);
}
/* 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)
{
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;
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
*
* 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)
{
__bdi_start_writeback(bdi, nr_pages, true);
}
/**
* 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)
{
spin_lock(&inode_wb_list_lock);
list_del_init(&inode->i_wb_list);
spin_unlock(&inode_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 = &inode_to_bdi(inode)->wb;
assert_spin_locked(&inode_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 = &inode_to_bdi(inode)->wb;
assert_spin_locked(&inode_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(&inode_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 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 = wb_inode(delaying_queue->prev);
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_wb_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)) {
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);
}
}
}
/*
* 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, unsigned long *older_than_this)
{
assert_spin_locked(&inode_wb_list_lock);
list_splice_init(&wb->b_more_io, &wb->b_io);
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);
while (inode->i_state & I_SYNC) {
spin_unlock(&inode->i_lock);
spin_unlock(&inode_wb_list_lock);
__wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
spin_lock(&inode_wb_list_lock);
spin_lock(&inode->i_lock);
}
}
/*
* Write out an inode's dirty pages. Called under inode_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 writeback_control *wbc)
{
struct address_space *mapping = inode->i_mapping;
unsigned dirty;
int ret;
assert_spin_locked(&inode_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);
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_PAGES */
inode->i_state |= I_SYNC;
inode->i_state &= ~I_DIRTY_PAGES;
spin_unlock(&inode->i_lock);
spin_unlock(&inode_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(&inode_wb_list_lock);
spin_lock(&inode->i_lock);
inode->i_state &= ~I_SYNC;
if (!(inode->i_state & I_FREEING)) {
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);
} 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);
}
} 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);
} 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);
return ret;
}
/*
* For background 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 bool pin_sb_for_writeback(struct super_block *sb)
{
spin_lock(&sb_lock);
if (list_empty(&sb->s_instances)) {
spin_unlock(&sb_lock);
return false;
}
sb->s_count++;
spin_unlock(&sb_lock);
if (down_read_trylock(&sb->s_umount)) {
if (sb->s_root)
return true;
up_read(&sb->s_umount);
}
put_super(sb);
return false;
}
/*
* 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 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, bool only_this_sb)
{
while (!list_empty(&wb->b_io)) {
long pages_skipped;
struct inode *inode = wb_inode(wb->b_io.prev);
if (inode->i_sb != sb) {
if (only_this_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);
continue;
}
/*
* The inode belongs to a different superblock.
* Bounce back to the caller to unpin this and
* pin the next superblock.
*/
return 0;
}
/*
* 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);
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)) {
spin_unlock(&inode->i_lock);
return 1;
}
__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->i_lock);
spin_unlock(&inode_wb_list_lock);
iput(inode);
cond_resched();
spin_lock(&inode_wb_list_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;
}
void writeback_inodes_wb(struct bdi_writeback *wb,
struct writeback_control *wbc)
{
int ret = 0;
if (!wbc->wb_start)
wbc->wb_start = jiffies; /* livelock avoidance */
spin_lock(&inode_wb_list_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 = wb_inode(wb->b_io.prev);
struct super_block *sb = inode->i_sb;
if (!pin_sb_for_writeback(sb)) {
requeue_io(inode);
continue;
}
ret = writeback_sb_inodes(sb, wb, wbc, false);
drop_super(sb);
if (ret)
break;
}
spin_unlock(&inode_wb_list_lock);
/* Leave any unwritten inodes on b_io */
}
static void __writeback_inodes_sb(struct super_block *sb,
struct bdi_writeback *wb, struct writeback_control *wbc)
{
WARN_ON(!rwsem_is_locked(&sb->s_umount));
spin_lock(&inode_wb_list_lock);
if (!wbc->for_kupdate || list_empty(&wb->b_io))
queue_io(wb, wbc->older_than_this);
writeback_sb_inodes(sb, wb, wbc, true);
spin_unlock(&inode_wb_list_lock);
}
/*
* 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;
global_dirty_limits(&background_thresh, &dirty_thresh);
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_work *work)
{
struct writeback_control wbc = {
.sync_mode = work->sync_mode,
.older_than_this = NULL,
.for_kupdate = work->for_kupdate,
.for_background = work->for_background,
.range_cyclic = work->range_cyclic,
};
unsigned long oldest_jif;
long wrote = 0;
long write_chunk;
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;
}
/*
* 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_inodes_sb() <== called only once
* write_cache_pages() <== called once for each inode
* (quickly) tag currently dirty pages
* (maybe slowly) sync all tagged pages
*/
if (wbc.sync_mode == WB_SYNC_NONE)
write_chunk = MAX_WRITEBACK_PAGES;
else
write_chunk = LONG_MAX;
wbc.wb_start = jiffies; /* livelock avoidance */
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())
break;
wbc.more_io = 0;
wbc.nr_to_write = write_chunk;
wbc.pages_skipped = 0;
trace_wbc_writeback_start(&wbc, wb->bdi);
if (work->sb)
__writeback_inodes_sb(work->sb, wb, &wbc);
else
writeback_inodes_wb(wb, &wbc);
trace_wbc_writeback_written(&wbc, wb->bdi);
work->nr_pages -= write_chunk - wbc.nr_to_write;
wrote += write_chunk - 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 < write_chunk)
continue;
/*
* Nothing written. Wait for some inode to
* become available for writeback. Otherwise
* we'll just busyloop.
*/
spin_lock(&inode_wb_list_lock);
if (!list_empty(&wb->b_more_io)) {
inode = wb_inode(wb->b_more_io.prev);
trace_wbc_writeback_wait(&wbc, wb->bdi);
spin_lock(&inode->i_lock);
inode_wait_for_writeback(inode);
spin_unlock(&inode->i_lock);
}
spin_unlock(&inode_wb_list_lock);
}
return wrote;
}
/*
* 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()) {
struct wb_writeback_work work = {
.nr_pages = LONG_MAX,
.sync_mode = WB_SYNC_NONE,
.for_background = 1,
.range_cyclic = 1,
};
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,
};
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_should_stop()) {
/*
* 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();
}
try_to_freeze();
}
/* 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)
{
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);
}
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.
*
* This function *must* be atomic for the I_DIRTY_PAGES case -
* set_page_dirty() is called under spinlock in several places.
*
* 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);
}
/*
* 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(&inode_wb_list_lock);
inode->dirtied_when = jiffies;
list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
spin_unlock(&inode_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);
/*
* Write out a superblock's list of dirty inodes. A wait will be performed
* upon no inodes, all inodes or the final one, depending upon sync_mode.
*
* If older_than_this is non-NULL, then only write out inodes which
* had their first dirtying at a time earlier than *older_than_this.
*
* If `bdi' is non-zero then we're being asked to writeback a specific queue.
* This function assumes that the blockdev superblock's inodes are backed by
* a variety of queues, so all inodes are searched. For other superblocks,
* assume that all inodes are backed by the same queue.
*
* The inodes to be written are parked on bdi->b_io. They are moved back onto
* bdi->b_dirty as they are selected for writing. This way, none can be missed
* on the writer throttling path, and we get decent balancing between many
* throttled threads: we don't want them all piling up on inode_sync_wait.
*/
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
*
* 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)
{
DECLARE_COMPLETION_ONSTACK(done);
struct wb_writeback_work work = {
.sb = sb,
.sync_mode = WB_SYNC_NONE,
.done = &done,
.nr_pages = nr,
};
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
*
* 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)
{
return writeback_inodes_sb_nr(sb, get_nr_dirty_pages());
}
EXPORT_SYMBOL(writeback_inodes_sb);
/**
* writeback_inodes_sb_if_idle - start writeback if none underway
* @sb: the superblock
*
* 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)
{
if (!writeback_in_progress(sb->s_bdi)) {
down_read(&sb->s_umount);
writeback_inodes_sb(sb);
up_read(&sb->s_umount);
return 1;
} else
return 0;
}
EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
/**
* writeback_inodes_sb_if_idle - start writeback if none underway
* @sb: the superblock
* @nr: the number of pages to write
*
* 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)
{
if (!writeback_in_progress(sb->s_bdi)) {
down_read(&sb->s_umount);
writeback_inodes_sb_nr(sb, nr);
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,
};
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)
{
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(&inode_wb_list_lock);
spin_lock(&inode->i_lock);
ret = writeback_single_inode(inode, &wbc);
spin_unlock(&inode->i_lock);
spin_unlock(&inode_wb_list_lock);
if (sync)
inode_sync_wait(inode);
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)
{
int ret;
spin_lock(&inode_wb_list_lock);
spin_lock(&inode->i_lock);
ret = writeback_single_inode(inode, wbc);
spin_unlock(&inode->i_lock);
spin_unlock(&inode_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);