linux/fs/fs-writeback.c
Linus Torvalds 2f4084209a Merge branch 'for-linus' of git://git.kernel.dk/linux-2.6-block
* 'for-linus' of git://git.kernel.dk/linux-2.6-block: (34 commits)
  cfq-iosched: Fix the incorrect timeslice accounting with forced_dispatch
  loop: Update mtime when writing using aops
  block: expose the statistics in blkio.time and blkio.sectors for the root cgroup
  backing-dev: Handle class_create() failure
  Block: Fix block/elevator.c elevator_get() off-by-one error
  drbd: lc_element_by_index() never returns NULL
  cciss: unlock on error path
  cfq-iosched: Do not merge queues of BE and IDLE classes
  cfq-iosched: Add additional blktrace log messages in CFQ for easier debugging
  i2o: Remove the dangerous kobj_to_i2o_device macro
  block: remove 16 bytes of padding from struct request on 64bits
  cfq-iosched: fix a kbuild regression
  block: make CONFIG_BLK_CGROUP visible
  Remove GENHD_FL_DRIVERFS
  block: Export max number of segments and max segment size in sysfs
  block: Finalize conversion of block limits functions
  block: Fix overrun in lcm() and move it to lib
  vfs: improve writeback_inodes_wb()
  paride: fix off-by-one test
  drbd: fix al-to-on-disk-bitmap for 4k logical_block_size
  ...
2010-04-09 11:50:29 -07:00

1292 lines
34 KiB
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 "internal.h"
#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);
}
}
}
/**
* __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;
/*
* 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))
block_dump___mark_inode_dirty(inode);
spin_lock(&inode_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;
/*
* Only add valid (hashed) inodes to the superblock's
* dirty list. Add blockdev inodes as well.
*/
if (!S_ISBLK(inode->i_mode)) {
if (hlist_unhashed(&inode->i_hash))
goto out;
}
if (inode->i_state & (I_FREEING|I_CLEAR))
goto out;
/*
* 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) {
struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
struct backing_dev_info *bdi = wb->bdi;
if (bdi_cap_writeback_dirty(bdi) &&
!test_bit(BDI_registered, &bdi->state)) {
WARN_ON(1);
printk(KERN_ERR "bdi-%s not registered\n",
bdi->name);
}
inode->dirtied_when = jiffies;
list_move(&inode->i_list, &wb->b_dirty);
}
}
out:
spin_unlock(&inode_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_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;
if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE|I_NEW))
continue;
mapping = inode->i_mapping;
if (mapping->nrpages == 0)
continue;
__iget(inode);
spin_unlock(&inode_lock);
/*
* We hold a reference to 'inode' so it couldn't have
* been removed from s_inodes list while we dropped the
* inode_lock. We cannot iput the inode now as we can
* be holding the last reference and we cannot iput it
* under inode_lock. So we keep the reference and iput
* it later.
*/
iput(old_inode);
old_inode = inode;
filemap_fdatawait(mapping);
cond_resched();
spin_lock(&inode_lock);
}
spin_unlock(&inode_lock);
iput(old_inode);
}
/**
* 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. The number of pages submitted is
* returned.
*/
void writeback_inodes_sb(struct super_block *sb)
{
unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
long nr_to_write;
nr_to_write = nr_dirty + nr_unstable +
(inodes_stat.nr_inodes - inodes_stat.nr_unused);
bdi_start_writeback(sb->s_bdi, sb, nr_to_write);
}
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)) {
writeback_inodes_sb(sb);
return 1;
} else
return 0;
}
EXPORT_SYMBOL(writeback_inodes_sb_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. The number of pages synced is returned.
*/
void sync_inodes_sb(struct super_block *sb)
{
bdi_sync_writeback(sb->s_bdi, sb);
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_lock);
ret = writeback_single_inode(inode, &wbc);
spin_unlock(&inode_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_lock);
ret = writeback_single_inode(inode, wbc);
spin_unlock(&inode_lock);
return ret;
}
EXPORT_SYMBOL(sync_inode);