linux/fs/fs-writeback.c
Jens Axboe 500b067c5e writeback: check for registered bdi in flusher add and inode dirty
Also a debugging aid. We want to catch dirty inodes being added to
backing devices that don't do writeback.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-09-11 09:20:26 +02:00

1299 lines
33 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/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;
/*
* Work items for the bdi_writeback threads
*/
struct bdi_work {
struct list_head list;
struct list_head wait_list;
struct rcu_head rcu_head;
unsigned long seen;
atomic_t pending;
struct super_block *sb;
unsigned long nr_pages;
enum writeback_sync_modes sync_mode;
unsigned long state;
};
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 writeback_control *wbc)
{
INIT_RCU_HEAD(&work->rcu_head);
work->sb = wbc->sb;
work->nr_pages = wbc->nr_to_write;
work->sync_mode = wbc->sync_mode;
work->state = WS_USED;
}
static inline void bdi_work_init_on_stack(struct bdi_work *work,
struct writeback_control *wbc)
{
bdi_work_init(work, wbc);
work->state |= WS_ONSTACK;
}
/**
* 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();
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->sync_mode;
/*
* 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 (!bdi_work_on_stack(work))
bdi_work_clear(work);
if (sync_mode == WB_SYNC_NONE || bdi_work_on_stack(work))
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)
{
if (work) {
work->seen = bdi->wb_mask;
BUG_ON(!work->seen);
atomic_set(&work->pending, bdi->wb_cnt);
BUG_ON(!bdi->wb_cnt);
/*
* Make sure stores are seen before it appears on the list
*/
smp_mb();
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 we failed allocating the bdi work item, wake up the wb
* thread always. As a safety precaution, it'll flush out
* everything
*/
if (!wb_has_dirty_io(wb)) {
if (work)
wb_clear_pending(wb, work);
} else 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 struct bdi_work *bdi_alloc_work(struct writeback_control *wbc)
{
struct bdi_work *work;
work = kmalloc(sizeof(*work), GFP_ATOMIC);
if (work)
bdi_work_init(work, wbc);
return work;
}
void bdi_start_writeback(struct writeback_control *wbc)
{
const bool must_wait = wbc->sync_mode == WB_SYNC_ALL;
struct bdi_work work_stack, *work = NULL;
if (!must_wait)
work = bdi_alloc_work(wbc);
if (!work) {
work = &work_stack;
bdi_work_init_on_stack(work, wbc);
}
bdi_queue_work(wbc->bdi, work);
/*
* If the sync mode is WB_SYNC_ALL, block waiting for the work to
* complete. If not, we only need to wait for the work to be started,
* if we allocated it on-stack. We use the same mechanism, if the
* wait bit is set in the bdi_work struct, then threads will not
* clear pending until after they are done.
*
* Note that work == &work_stack if must_wait is true, so we don't
* need to do call_rcu() here ever, since the completion path will
* have done that for us.
*/
if (must_wait || work == &work_stack) {
bdi_wait_on_work_clear(work);
if (work != &work_stack)
call_rcu(&work->rcu_head, bdi_work_free);
}
}
/*
* 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 pdflush 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)
{
while (!list_empty(delaying_queue)) {
struct inode *inode = list_entry(delaying_queue->prev,
struct inode, i_list);
if (older_than_this &&
inode_dirtied_after(inode, *older_than_this))
break;
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, int sync)
{
if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
return inode->i_sb->s_op->write_inode(inode, sync);
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;
int wait = wbc->sync_mode == WB_SYNC_ALL;
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 (!wait) {
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);
/* 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, wait);
if (ret == 0)
ret = err;
}
if (wait) {
int err = filemap_fdatawait(mapping);
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) &&
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;
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 (inode->i_state & I_DIRTY) {
/*
* Someone redirtied the inode while were writing back
* the 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;
}
/*
* 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.
*
* Returns 0 if the super was successfully pinned (or pinning wasn't needed),
* 1 if we failed.
*/
static int pin_sb_for_writeback(struct writeback_control *wbc,
struct inode *inode)
{
struct super_block *sb = inode->i_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 0;
}
spin_lock(&sb_lock);
sb->s_count++;
if (down_read_trylock(&sb->s_umount)) {
if (sb->s_root) {
spin_unlock(&sb_lock);
return 0;
}
/*
* umounted, drop rwsem again and fall through to failure
*/
up_read(&sb->s_umount);
}
sb->s_count--;
spin_unlock(&sb_lock);
return 1;
}
static void unpin_sb_for_writeback(struct writeback_control *wbc,
struct inode *inode)
{
struct super_block *sb = inode->i_sb;
if (wbc->sync_mode == WB_SYNC_ALL)
return;
up_read(&sb->s_umount);
put_super(sb);
}
static void writeback_inodes_wb(struct bdi_writeback *wb,
struct writeback_control *wbc)
{
struct super_block *sb = wbc->sb;
const int is_blkdev_sb = sb_is_blkdev_sb(sb);
const unsigned long 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);
long pages_skipped;
/*
* super block given and doesn't match, skip this inode
*/
if (sb && sb != inode->i_sb) {
redirty_tail(inode);
continue;
}
if (!bdi_cap_writeback_dirty(wb->bdi)) {
redirty_tail(inode);
if (is_blkdev_sb) {
/*
* Dirty memory-backed blockdev: the ramdisk
* driver does this. Skip just this inode
*/
continue;
}
/*
* Dirty memory-backed inode against a filesystem other
* than the kernel-internal bdev filesystem. Skip the
* entire superblock.
*/
break;
}
if (inode->i_state & (I_NEW | I_WILL_FREE)) {
requeue_io(inode);
continue;
}
if (wbc->nonblocking && bdi_write_congested(wb->bdi)) {
wbc->encountered_congestion = 1;
if (!is_blkdev_sb)
break; /* Skip a congested fs */
requeue_io(inode);
continue; /* Skip a congested blockdev */
}
/*
* Was this inode dirtied after sync_sb_inodes was called?
* This keeps sync from extra jobs and livelock.
*/
if (inode_dirtied_after(inode, start))
break;
if (pin_sb_for_writeback(wbc, inode)) {
requeue_io(inode);
continue;
}
BUG_ON(inode->i_state & (I_FREEING | I_CLEAR));
__iget(inode);
pages_skipped = wbc->pages_skipped;
writeback_single_inode(inode, wbc);
unpin_sb_for_writeback(wbc, inode);
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;
break;
}
if (!list_empty(&wb->b_more_io))
wbc->more_io = 1;
}
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, long nr_pages,
struct super_block *sb,
enum writeback_sync_modes sync_mode, int for_kupdate)
{
struct writeback_control wbc = {
.bdi = wb->bdi,
.sb = sb,
.sync_mode = sync_mode,
.older_than_this = NULL,
.for_kupdate = for_kupdate,
.range_cyclic = 1,
};
unsigned long oldest_jif;
long wrote = 0;
if (wbc.for_kupdate) {
wbc.older_than_this = &oldest_jif;
oldest_jif = jiffies -
msecs_to_jiffies(dirty_expire_interval * 10);
}
for (;;) {
/*
* Don't flush anything for non-integrity writeback where
* no nr_pages was given
*/
if (!for_kupdate && nr_pages <= 0 && sync_mode == WB_SYNC_NONE)
break;
/*
* If no specific pages were given and this is just a
* periodic background writeout and we are below the
* background dirty threshold, don't do anything
*/
if (for_kupdate && nr_pages <= 0 && !over_bground_thresh())
break;
wbc.more_io = 0;
wbc.encountered_congestion = 0;
wbc.nr_to_write = MAX_WRITEBACK_PAGES;
wbc.pages_skipped = 0;
writeback_inodes_wb(wb, &wbc);
nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;
/*
* If we ran out of stuff to write, bail unless more_io got set
*/
if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) {
if (wbc.more_io && !wbc.for_kupdate)
continue;
break;
}
}
return wrote;
}
/*
* Return the next bdi_work struct that hasn't been processed by this
* wb thread yet
*/
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_and_clear_bit(wb->nr, &work->seen))
continue;
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)
return wb_writeback(wb, nr_pages, NULL, WB_SYNC_NONE, 1);
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 nr_pages, wrote = 0;
while ((work = get_next_work_item(bdi, wb)) != NULL) {
enum writeback_sync_modes sync_mode;
nr_pages = work->nr_pages;
/*
* Override sync mode, in case we must wait for completion
*/
if (force_wait)
work->sync_mode = sync_mode = WB_SYNC_ALL;
else
sync_mode = work->sync_mode;
/*
* If this isn't a data integrity operation, just notify
* that we have seen this work and we are now starting it.
*/
if (sync_mode == WB_SYNC_NONE)
wb_clear_pending(wb, work);
wrote += wb_writeback(wb, nr_pages, work->sb, sync_mode, 0);
/*
* This is a data integrity writeback, so only do the
* notification when we have completed the work.
*/
if (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);
set_current_state(TASK_INTERRUPTIBLE);
schedule_timeout(wait_jiffies);
try_to_freeze();
}
return 0;
}
/*
* Schedule writeback for all backing devices. Expensive! If this is a data
* integrity operation, writeback will be complete when this returns. If
* we are simply called for WB_SYNC_NONE, then writeback will merely be
* scheduled to run.
*/
static void bdi_writeback_all(struct writeback_control *wbc)
{
const bool must_wait = wbc->sync_mode == WB_SYNC_ALL;
struct backing_dev_info *bdi;
struct bdi_work *work;
LIST_HEAD(list);
restart:
spin_lock(&bdi_lock);
list_for_each_entry(bdi, &bdi_list, bdi_list) {
struct bdi_work *work;
if (!bdi_has_dirty_io(bdi))
continue;
/*
* If work allocation fails, do the writes inline. We drop
* the lock and restart the list writeout. This should be OK,
* since this happens rarely and because the writeout should
* eventually make more free memory available.
*/
work = bdi_alloc_work(wbc);
if (!work) {
struct writeback_control __wbc;
/*
* Not a data integrity writeout, just continue
*/
if (!must_wait)
continue;
spin_unlock(&bdi_lock);
__wbc = *wbc;
__wbc.bdi = bdi;
writeback_inodes_wbc(&__wbc);
goto restart;
}
if (must_wait)
list_add_tail(&work->wait_list, &list);
bdi_queue_work(bdi, work);
}
spin_unlock(&bdi_lock);
/*
* If this is for WB_SYNC_ALL, wait for pending work to complete
* before returning.
*/
while (!list_empty(&list)) {
work = list_entry(list.next, struct bdi_work, wait_list);
list_del(&work->wait_list);
bdi_wait_on_work_clear(work);
call_rcu(&work->rcu_head, bdi_work_free);
}
}
/*
* Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
* the whole world.
*/
void wakeup_flusher_threads(long nr_pages)
{
struct writeback_control wbc = {
.sync_mode = WB_SYNC_NONE,
.older_than_this = NULL,
.range_cyclic = 1,
};
if (nr_pages == 0)
nr_pages = global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS);
wbc.nr_to_write = nr_pages;
bdi_writeback_all(&wbc);
}
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 we're a pdlfush thread, then implement pdflush collision avoidance
* against the entire list.
*
* 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 writeback_control *wbc)
{
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(&wbc->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, &wbc->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.
*/
long writeback_inodes_sb(struct super_block *sb)
{
struct writeback_control wbc = {
.sb = sb,
.sync_mode = WB_SYNC_NONE,
.range_start = 0,
.range_end = LLONG_MAX,
};
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);
wbc.nr_to_write = nr_to_write;
bdi_writeback_all(&wbc);
return nr_to_write - wbc.nr_to_write;
}
EXPORT_SYMBOL(writeback_inodes_sb);
/**
* 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.
*/
long sync_inodes_sb(struct super_block *sb)
{
struct writeback_control wbc = {
.sb = sb,
.sync_mode = WB_SYNC_ALL,
.range_start = 0,
.range_end = LLONG_MAX,
};
long nr_to_write = LONG_MAX; /* doesn't actually matter */
wbc.nr_to_write = nr_to_write;
bdi_writeback_all(&wbc);
wait_sb_inodes(&wbc);
return nr_to_write - wbc.nr_to_write;
}
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);
/**
* generic_osync_inode - flush all dirty data for a given inode to disk
* @inode: inode to write
* @mapping: the address_space that should be flushed
* @what: what to write and wait upon
*
* This can be called by file_write functions for files which have the
* O_SYNC flag set, to flush dirty writes to disk.
*
* @what is a bitmask, specifying which part of the inode's data should be
* written and waited upon.
*
* OSYNC_DATA: i_mapping's dirty data
* OSYNC_METADATA: the buffers at i_mapping->private_list
* OSYNC_INODE: the inode itself
*/
int generic_osync_inode(struct inode *inode, struct address_space *mapping, int what)
{
int err = 0;
int need_write_inode_now = 0;
int err2;
if (what & OSYNC_DATA)
err = filemap_fdatawrite(mapping);
if (what & (OSYNC_METADATA|OSYNC_DATA)) {
err2 = sync_mapping_buffers(mapping);
if (!err)
err = err2;
}
if (what & OSYNC_DATA) {
err2 = filemap_fdatawait(mapping);
if (!err)
err = err2;
}
spin_lock(&inode_lock);
if ((inode->i_state & I_DIRTY) &&
((what & OSYNC_INODE) || (inode->i_state & I_DIRTY_DATASYNC)))
need_write_inode_now = 1;
spin_unlock(&inode_lock);
if (need_write_inode_now) {
err2 = write_inode_now(inode, 1);
if (!err)
err = err2;
}
else
inode_sync_wait(inode);
return err;
}
EXPORT_SYMBOL(generic_osync_inode);