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Date: Wed, 20 May 2009 13:34:30 +0200
From: Jan Kara <jack@...e.cz>
To: Jens Axboe <jens.axboe@...cle.com>
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
chris.mason@...cle.com, david@...morbit.com, hch@...radead.org,
akpm@...ux-foundation.org, jack@...e.cz,
yanmin_zhang@...ux.intel.com
Subject: Re: [PATCH 04/11] writeback: separate the flushing state/task from
the bdi
On Mon 18-05-09 14:19:45, Jens Axboe wrote:
> Add a struct bdi_writeback for tracking and handling dirty IO. This
> is in preparation for adding > 1 flusher task per bdi.
Some changes (IMO the most complicated ones ;) in this patch set seem to
be just reordering / cleanup of changes which happened in patch #2. Could
you maybe move it there. Commented below...
>
> Signed-off-by: Jens Axboe <jens.axboe@...cle.com>
> ---
> fs/fs-writeback.c | 140 +++++++++++++++++-----------
> include/linux/backing-dev.h | 42 +++++----
> mm/backing-dev.c | 218 ++++++++++++++++++++++++++++--------------
> 3 files changed, 256 insertions(+), 144 deletions(-)
>
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index 8a25d14..50e21e8 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -46,9 +46,11 @@ int nr_pdflush_threads;
> * unless they implement their own. Which is somewhat inefficient, as this
> * may prevent concurrent writeback against multiple devices.
> */
> -static int writeback_acquire(struct backing_dev_info *bdi)
> +static int writeback_acquire(struct bdi_writeback *wb)
> {
> - return !test_and_set_bit(BDI_pdflush, &bdi->state);
> + struct backing_dev_info *bdi = wb->bdi;
> +
> + return !test_and_set_bit(wb->nr, &bdi->wb_active);
> }
>
> /**
> @@ -59,19 +61,38 @@ static int writeback_acquire(struct backing_dev_info *bdi)
> */
> int writeback_in_progress(struct backing_dev_info *bdi)
> {
> - return test_bit(BDI_pdflush, &bdi->state);
> + return bdi->wb_active != 0;
> }
>
> /**
> * writeback_release - relinquish exclusive writeback access against a device.
> * @bdi: the device's backing_dev_info structure
> */
> -static void writeback_release(struct backing_dev_info *bdi)
> +static void writeback_release(struct bdi_writeback *wb)
> {
> - WARN_ON_ONCE(!writeback_in_progress(bdi));
> - bdi->wb_arg.nr_pages = 0;
> - bdi->wb_arg.sb = NULL;
> - clear_bit(BDI_pdflush, &bdi->state);
> + struct backing_dev_info *bdi = wb->bdi;
> +
> + wb->nr_pages = 0;
> + wb->sb = NULL;
> + clear_bit(wb->nr, &bdi->wb_active);
> +}
> +
> +static void wb_start_writeback(struct bdi_writeback *wb, struct super_block *sb,
> + long nr_pages)
> +{
> + if (!wb_has_dirty_io(wb))
> + return;
> +
> + if (writeback_acquire(wb)) {
> + wb->nr_pages = nr_pages;
> + wb->sb = sb;
> +
> + /*
> + * make above store seen before the task is woken
> + */
> + smp_mb();
> + wake_up(&wb->wait);
> + }
> }
>
> int bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
> @@ -81,21 +102,12 @@ int bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
> * This only happens the first time someone kicks this bdi, so put
> * it out-of-line.
> */
> - if (unlikely(!bdi->task)) {
> + if (unlikely(!bdi->wb.task)) {
> bdi_add_default_flusher_task(bdi);
> return 1;
> }
>
> - if (writeback_acquire(bdi)) {
> - bdi->wb_arg.nr_pages = nr_pages;
> - bdi->wb_arg.sb = sb;
> - /*
> - * make above store seen before the task is woken
> - */
> - smp_mb();
> - wake_up(&bdi->wait);
> - }
> -
> + wb_start_writeback(&bdi->wb, sb, nr_pages);
> return 0;
> }
>
> @@ -123,12 +135,12 @@ int bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
> * 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 void bdi_kupdated(struct backing_dev_info *bdi)
> +static void wb_kupdated(struct bdi_writeback *wb)
> {
> unsigned long oldest_jif;
> long nr_to_write;
> struct writeback_control wbc = {
> - .bdi = bdi,
> + .bdi = wb->bdi,
> .sync_mode = WB_SYNC_NONE,
> .older_than_this = &oldest_jif,
> .nr_to_write = 0,
> @@ -155,15 +167,19 @@ static void bdi_kupdated(struct backing_dev_info *bdi)
> }
> }
>
> -static void bdi_pdflush(struct backing_dev_info *bdi)
> +static void generic_sync_wb_inodes(struct bdi_writeback *wb,
> + struct super_block *sb,
> + struct writeback_control *wbc);
> +
> +static void wb_writeback(struct bdi_writeback *wb)
> {
> struct writeback_control wbc = {
> - .bdi = bdi,
> + .bdi = wb->bdi,
> .sync_mode = WB_SYNC_NONE,
> .older_than_this = NULL,
> .range_cyclic = 1,
> };
> - long nr_pages = bdi->wb_arg.nr_pages;
> + long nr_pages = wb->nr_pages;
>
> for (;;) {
> unsigned long background_thresh, dirty_thresh;
> @@ -177,7 +193,7 @@ static void bdi_pdflush(struct backing_dev_info *bdi)
> wbc.encountered_congestion = 0;
> wbc.nr_to_write = MAX_WRITEBACK_PAGES;
> wbc.pages_skipped = 0;
> - generic_sync_bdi_inodes(bdi->wb_arg.sb, &wbc);
> + generic_sync_wb_inodes(wb, wb->sb, &wbc);
> nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
> /*
> * If we ran out of stuff to write, bail unless more_io got set
> @@ -194,13 +210,13 @@ static void bdi_pdflush(struct backing_dev_info *bdi)
> * 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 backing_dev_info *bdi)
> +int bdi_writeback_task(struct bdi_writeback *wb)
> {
> while (!kthread_should_stop()) {
> unsigned long wait_jiffies;
> DEFINE_WAIT(wait);
>
> - prepare_to_wait(&bdi->wait, &wait, TASK_INTERRUPTIBLE);
> + prepare_to_wait(&wb->wait, &wait, TASK_INTERRUPTIBLE);
> wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
> schedule_timeout(wait_jiffies);
> try_to_freeze();
> @@ -219,13 +235,13 @@ int bdi_writeback_task(struct backing_dev_info *bdi)
> * pdflush style writeout.
> *
> */
> - if (writeback_acquire(bdi))
> - bdi_kupdated(bdi);
> + if (writeback_acquire(wb))
> + wb_kupdated(wb);
> else
> - bdi_pdflush(bdi);
> + wb_writeback(wb);
>
> - writeback_release(bdi);
> - finish_wait(&bdi->wait, &wait);
> + writeback_release(wb);
> + finish_wait(&wb->wait, &wait);
> }
>
> return 0;
> @@ -248,6 +264,14 @@ restart:
> rcu_read_unlock();
> }
>
> +/*
> + * We have only a single wb per bdi, so just return that.
> + */
> +static inline struct bdi_writeback *inode_get_wb(struct inode *inode)
> +{
> + return &inode_to_bdi(inode)->wb;
> +}
> +
> /**
> * __mark_inode_dirty - internal function
> * @inode: inode to mark
> @@ -346,9 +370,10 @@ void __mark_inode_dirty(struct inode *inode, int flags)
> * reposition it (that would break b_dirty time-ordering).
> */
> if (!was_dirty) {
> + struct bdi_writeback *wb = inode_get_wb(inode);
> +
> inode->dirtied_when = jiffies;
> - list_move(&inode->i_list,
> - &inode_to_bdi(inode)->b_dirty);
> + list_move(&inode->i_list, &wb->b_dirty);
> }
> }
> out:
> @@ -375,16 +400,16 @@ static int write_inode(struct inode *inode, int sync)
> */
> static void redirty_tail(struct inode *inode)
> {
> - struct backing_dev_info *bdi = inode_to_bdi(inode);
> + struct bdi_writeback *wb = inode_get_wb(inode);
>
> - if (!list_empty(&bdi->b_dirty)) {
> + if (!list_empty(&wb->b_dirty)) {
> struct inode *tail;
>
> - tail = list_entry(bdi->b_dirty.next, struct inode, i_list);
> + 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, &bdi->b_dirty);
> + list_move(&inode->i_list, &wb->b_dirty);
> }
>
> /*
> @@ -392,7 +417,9 @@ static void redirty_tail(struct inode *inode)
> */
> static void requeue_io(struct inode *inode)
> {
> - list_move(&inode->i_list, &inode_to_bdi(inode)->b_more_io);
> + struct bdi_writeback *wb = inode_get_wb(inode);
> +
> + list_move(&inode->i_list, &wb->b_more_io);
> }
>
> static void inode_sync_complete(struct inode *inode)
> @@ -439,11 +466,10 @@ static void move_expired_inodes(struct list_head *delaying_queue,
> /*
> * Queue all expired dirty inodes for io, eldest first.
> */
> -static void queue_io(struct backing_dev_info *bdi,
> - unsigned long *older_than_this)
> +static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
> {
> - list_splice_init(&bdi->b_more_io, bdi->b_io.prev);
> - move_expired_inodes(&bdi->b_dirty, &bdi->b_io, 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);
> }
>
> /*
> @@ -604,20 +630,20 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
> return __sync_single_inode(inode, wbc);
> }
>
> -void generic_sync_bdi_inodes(struct super_block *sb,
> - struct writeback_control *wbc)
> +static void generic_sync_wb_inodes(struct bdi_writeback *wb,
> + struct super_block *sb,
> + struct writeback_control *wbc)
> {
> const int is_blkdev_sb = sb_is_blkdev_sb(sb);
> - struct backing_dev_info *bdi = wbc->bdi;
> const unsigned long start = jiffies; /* livelock avoidance */
>
> spin_lock(&inode_lock);
>
> - if (!wbc->for_kupdate || list_empty(&bdi->b_io))
> - queue_io(bdi, wbc->older_than_this);
> + if (!wbc->for_kupdate || list_empty(&wb->b_io))
> + queue_io(wb, wbc->older_than_this);
>
> - while (!list_empty(&bdi->b_io)) {
> - struct inode *inode = list_entry(bdi->b_io.prev,
> + while (!list_empty(&wb->b_io)) {
> + struct inode *inode = list_entry(wb->b_io.prev,
> struct inode, i_list);
> long pages_skipped;
>
> @@ -629,7 +655,7 @@ void generic_sync_bdi_inodes(struct super_block *sb,
> continue;
> }
>
> - if (!bdi_cap_writeback_dirty(bdi)) {
> + if (!bdi_cap_writeback_dirty(wb->bdi)) {
> redirty_tail(inode);
> if (is_blkdev_sb) {
> /*
> @@ -651,7 +677,7 @@ void generic_sync_bdi_inodes(struct super_block *sb,
> continue;
> }
>
> - if (wbc->nonblocking && bdi_write_congested(bdi)) {
> + if (wbc->nonblocking && bdi_write_congested(wb->bdi)) {
> wbc->encountered_congestion = 1;
> if (!is_blkdev_sb)
> break; /* Skip a congested fs */
> @@ -685,7 +711,7 @@ void generic_sync_bdi_inodes(struct super_block *sb,
> wbc->more_io = 1;
> break;
> }
> - if (!list_empty(&bdi->b_more_io))
> + if (!list_empty(&wb->b_more_io))
> wbc->more_io = 1;
> }
>
> @@ -693,6 +719,14 @@ void generic_sync_bdi_inodes(struct super_block *sb,
> /* Leave any unwritten inodes on b_io */
> }
>
> +void generic_sync_bdi_inodes(struct super_block *sb,
> + struct writeback_control *wbc)
> +{
> + struct backing_dev_info *bdi = wbc->bdi;
> +
> + generic_sync_wb_inodes(&bdi->wb, sb, wbc);
> +}
> +
> /*
> * 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.
> diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
> index a848eea..a0c70f1 100644
> --- a/include/linux/backing-dev.h
> +++ b/include/linux/backing-dev.h
> @@ -23,8 +23,8 @@ struct dentry;
> * Bits in backing_dev_info.state
> */
> enum bdi_state {
> - BDI_pdflush, /* A pdflush thread is working this device */
> BDI_pending, /* On its way to being activated */
> + BDI_wb_alloc, /* Default embedded wb allocated */
> BDI_async_congested, /* The async (write) queue is getting full */
> BDI_sync_congested, /* The sync queue is getting full */
> BDI_unused, /* Available bits start here */
> @@ -40,15 +40,23 @@ enum bdi_stat_item {
>
> #define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
>
> -struct bdi_writeback_arg {
> - unsigned long nr_pages;
> - struct super_block *sb;
> +struct bdi_writeback {
> + struct backing_dev_info *bdi; /* our parent bdi */
> + unsigned int nr;
> +
> + struct task_struct *task; /* writeback task */
> + wait_queue_head_t wait;
> + struct list_head b_dirty; /* dirty inodes */
> + struct list_head b_io; /* parked for writeback */
> + struct list_head b_more_io; /* parked for more writeback */
> +
> + unsigned long nr_pages;
> + struct super_block *sb;
> };
>
> struct backing_dev_info {
> - struct list_head bdi_list;
> struct rcu_head rcu_head;
> -
> + struct list_head bdi_list;
> unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
> unsigned long state; /* Always use atomic bitops on this */
> unsigned int capabilities; /* Device capabilities */
> @@ -65,14 +73,11 @@ struct backing_dev_info {
> unsigned int min_ratio;
> unsigned int max_ratio, max_prop_frac;
>
> - struct device *dev;
> + struct bdi_writeback wb; /* default writeback info for this bdi */
> + unsigned long wb_active; /* bitmap of active tasks */
> + unsigned long wb_mask; /* number of registered tasks */
>
> - struct task_struct *task; /* writeback task */
> - wait_queue_head_t wait;
> - struct bdi_writeback_arg wb_arg; /* protected by BDI_pdflush */
> - struct list_head b_dirty; /* dirty inodes */
> - struct list_head b_io; /* parked for writeback */
> - struct list_head b_more_io; /* parked for more writeback */
> + struct device *dev;
>
> #ifdef CONFIG_DEBUG_FS
> struct dentry *debug_dir;
> @@ -89,18 +94,19 @@ int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
> void bdi_unregister(struct backing_dev_info *bdi);
> int bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
> long nr_pages);
> -int bdi_writeback_task(struct backing_dev_info *bdi);
> +int bdi_writeback_task(struct bdi_writeback *wb);
> void bdi_writeback_all(struct super_block *sb, long nr_pages);
> void bdi_add_default_flusher_task(struct backing_dev_info *bdi);
> +int bdi_has_dirty_io(struct backing_dev_info *bdi);
>
> extern spinlock_t bdi_lock;
> extern struct list_head bdi_list;
>
> -static inline int bdi_has_dirty_io(struct backing_dev_info *bdi)
> +static inline int wb_has_dirty_io(struct bdi_writeback *wb)
> {
> - return !list_empty(&bdi->b_dirty) ||
> - !list_empty(&bdi->b_io) ||
> - !list_empty(&bdi->b_more_io);
> + return !list_empty(&wb->b_dirty) ||
> + !list_empty(&wb->b_io) ||
> + !list_empty(&wb->b_more_io);
> }
>
> static inline void __add_bdi_stat(struct backing_dev_info *bdi,
> diff --git a/mm/backing-dev.c b/mm/backing-dev.c
> index c759449..677a8c6 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -199,17 +199,59 @@ static int __init default_bdi_init(void)
> }
> subsys_initcall(default_bdi_init);
>
> +static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
> +{
> + memset(wb, 0, sizeof(*wb));
> +
> + wb->bdi = bdi;
> + init_waitqueue_head(&wb->wait);
> + INIT_LIST_HEAD(&wb->b_dirty);
> + INIT_LIST_HEAD(&wb->b_io);
> + INIT_LIST_HEAD(&wb->b_more_io);
> +}
> +
> +static void bdi_flush_io(struct backing_dev_info *bdi)
> +{
> + struct writeback_control wbc = {
> + .bdi = bdi,
> + .sync_mode = WB_SYNC_NONE,
> + .older_than_this = NULL,
> + .range_cyclic = 1,
> + .nr_to_write = 1024,
> + };
> +
> + generic_sync_bdi_inodes(NULL, &wbc);
> +}
> +
> +static int wb_assign_nr(struct backing_dev_info *bdi, struct bdi_writeback *wb)
> +{
> + set_bit(0, &bdi->wb_mask);
> + wb->nr = 0;
> + return 0;
> +}
> +
> +static void bdi_put_wb(struct backing_dev_info *bdi, struct bdi_writeback *wb)
> +{
> + clear_bit(wb->nr, &bdi->wb_mask);
> + clear_bit(BDI_wb_alloc, &bdi->state);
> +}
> +
> +static struct bdi_writeback *bdi_new_wb(struct backing_dev_info *bdi)
> +{
> + struct bdi_writeback *wb;
> +
> + set_bit(BDI_wb_alloc, &bdi->state);
> + wb = &bdi->wb;
> + wb_assign_nr(bdi, wb);
> + return wb;
> +}
> +
> static int bdi_start_fn(void *ptr)
> {
> - struct backing_dev_info *bdi = ptr;
> + struct bdi_writeback *wb = ptr;
> + struct backing_dev_info *bdi = wb->bdi;
> struct task_struct *tsk = current;
> -
> - /*
> - * Add us to the active bdi_list
> - */
> - spin_lock_bh(&bdi_lock);
> - list_add_rcu(&bdi->bdi_list, &bdi_list);
> - spin_unlock_bh(&bdi_lock);
> + int ret;
>
> tsk->flags |= PF_FLUSHER | PF_SWAPWRITE;
> set_freezable();
> @@ -225,77 +267,81 @@ static int bdi_start_fn(void *ptr)
> clear_bit(BDI_pending, &bdi->state);
> wake_up_bit(&bdi->state, BDI_pending);
>
> - return bdi_writeback_task(bdi);
> + ret = bdi_writeback_task(wb);
> +
> + bdi_put_wb(bdi, wb);
> + return ret;
> +}
> +
> +int bdi_has_dirty_io(struct backing_dev_info *bdi)
> +{
> + return wb_has_dirty_io(&bdi->wb);
> }
>
> static int bdi_forker_task(void *ptr)
> {
> - struct backing_dev_info *bdi, *me = ptr;
> + struct bdi_writeback *me = ptr;
>
> for (;;) {
> + struct backing_dev_info *bdi;
> + struct bdi_writeback *wb;
> DEFINE_WAIT(wait);
>
> /*
> * Should never trigger on the default bdi
> */
> - WARN_ON(bdi_has_dirty_io(me));
> + if (wb_has_dirty_io(me)) {
> + bdi_flush_io(me->bdi);
> + WARN_ON(1);
> + }
>
> prepare_to_wait(&me->wait, &wait, TASK_INTERRUPTIBLE);
> +
> smp_mb();
> if (list_empty(&bdi_pending_list))
> schedule();
> - else {
> +
> + finish_wait(&me->wait, &wait);
> repeat:
> - bdi = NULL;
> + bdi = NULL;
> + spin_lock_bh(&bdi_lock);
> + if (!list_empty(&bdi_pending_list)) {
> + bdi = list_entry(bdi_pending_list.next,
> + struct backing_dev_info, bdi_list);
> + list_del_init(&bdi->bdi_list);
> + }
> + spin_unlock_bh(&bdi_lock);
>
> - spin_lock_bh(&bdi_lock);
> - if (!list_empty(&bdi_pending_list)) {
> - bdi = list_entry(bdi_pending_list.next,
> - struct backing_dev_info,
> - bdi_list);
> - list_del_init(&bdi->bdi_list);
> - }
> - spin_unlock_bh(&bdi_lock);
> + if (!bdi)
> + continue;
>
> - /*
> - * If no bdi or bdi already got setup, continue
> - */
> - if (!bdi || bdi->task)
> - continue;
> + wb = bdi_new_wb(bdi);
> + if (!wb)
> + goto readd_flush;
>
> - bdi->task = kthread_run(bdi_start_fn, bdi, "bdi-%s",
> + wb->task = kthread_run(bdi_start_fn, wb, "bdi-%s",
> dev_name(bdi->dev));
> + /*
> + * If task creation fails, then readd the bdi to
> + * the pending list and force writeout of the bdi
> + * from this forker thread. That will free some memory
> + * and we can try again.
> + */
> + if (!wb->task) {
> + bdi_put_wb(bdi, wb);
> +readd_flush:
> /*
> - * If task creation fails, then readd the bdi to
> - * the pending list and force writeout of the bdi
> - * from this forker thread. That will free some memory
> - * and we can try again.
> + * Add this 'bdi' to the back, so we get
> + * a chance to flush other bdi's to free
> + * memory.
> */
> - if (!bdi->task) {
> - struct writeback_control wbc = {
> - .bdi = bdi,
> - .sync_mode = WB_SYNC_NONE,
> - .older_than_this = NULL,
> - .range_cyclic = 1,
> - };
> -
> - /*
> - * Add this 'bdi' to the back, so we get
> - * a chance to flush other bdi's to free
> - * memory.
> - */
> - spin_lock_bh(&bdi_lock);
> - list_add_tail(&bdi->bdi_list,
> - &bdi_pending_list);
> - spin_unlock_bh(&bdi_lock);
> -
> - wbc.nr_to_write = 1024;
> - generic_sync_bdi_inodes(NULL, &wbc);
> - goto repeat;
> - }
> - }
> + spin_lock_bh(&bdi_lock);
> + list_add_tail(&bdi->bdi_list, &bdi_pending_list);
> + spin_unlock_bh(&bdi_lock);
>
> - finish_wait(&me->wait, &wait);
> + bdi_flush_io(bdi);
> + goto repeat;
> + }
> }
Quite a lot of changes in this function (and creation of bdi_flush_io())
are just cleanups of patch #2 so it would be nice to move them there...
>
> return 0;
> @@ -318,11 +364,21 @@ static void bdi_add_to_pending(struct rcu_head *head)
> list_add_tail(&bdi->bdi_list, &bdi_pending_list);
> spin_unlock(&bdi_lock);
>
> - wake_up(&default_backing_dev_info.wait);
> + wake_up(&default_backing_dev_info.wb.wait);
> }
>
> +/*
> + * Add a new flusher task that gets created for any bdi
> + * that has dirty data pending writeout
> + */
> void bdi_add_default_flusher_task(struct backing_dev_info *bdi)
> {
> + if (!bdi_cap_writeback_dirty(bdi))
> + return;
> +
> + /*
> + * Someone already marked this pending for task creation
> + */
> if (test_and_set_bit(BDI_pending, &bdi->state))
> return;
>
> @@ -363,9 +419,18 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
> * on-demand when they need it.
> */
> if (bdi_cap_flush_forker(bdi)) {
> - bdi->task = kthread_run(bdi_forker_task, bdi, "bdi-%s",
> + struct bdi_writeback *wb;
> +
> + wb = bdi_new_wb(bdi);
> + if (!wb) {
> + ret = -ENOMEM;
> + goto exit;
> + }
> +
> + wb->task = kthread_run(bdi_forker_task, wb, "bdi-%s",
> dev_name(dev));
> - if (!bdi->task) {
> + if (!wb->task) {
> + bdi_put_wb(bdi, wb);
> ret = -ENOMEM;
> goto exit;
> }
> @@ -395,34 +460,44 @@ static int sched_wait(void *word)
> return 0;
> }
>
> +/*
> + * Remove bdi from global list and shutdown any threads we have running
> + */
> static void bdi_wb_shutdown(struct backing_dev_info *bdi)
> {
> + if (!bdi_cap_writeback_dirty(bdi))
> + return;
> +
> /*
> * If setup is pending, wait for that to complete first
> + * Make sure nobody finds us on the bdi_list anymore
> */
> wait_on_bit(&bdi->state, BDI_pending, sched_wait, TASK_UNINTERRUPTIBLE);
>
> + /*
> + * Make sure nobody finds us on the bdi_list anymore
> + */
> spin_lock_bh(&bdi_lock);
> list_del_rcu(&bdi->bdi_list);
> spin_unlock_bh(&bdi_lock);
>
> /*
> - * In case the bdi is freed right after unregister, we need to
> - * make sure any RCU sections have exited
> + * Now make sure that anybody who is currently looking at us from
> + * the bdi_list iteration have exited.
> */
> synchronize_rcu();
> +
> + /*
> + * Finally, kill the kernel thread
> + */
> + kthread_stop(bdi->wb.task);
> }
>
> void bdi_unregister(struct backing_dev_info *bdi)
> {
> if (bdi->dev) {
> - if (!bdi_cap_flush_forker(bdi)) {
> + if (!bdi_cap_flush_forker(bdi))
> bdi_wb_shutdown(bdi);
> - if (bdi->task) {
> - kthread_stop(bdi->task);
> - bdi->task = NULL;
> - }
> - }
> bdi_debug_unregister(bdi);
> device_unregister(bdi->dev);
> bdi->dev = NULL;
This whole chunk is just a cleanup of patch #2, isn't it? Maybe move
there?
> @@ -440,11 +515,10 @@ int bdi_init(struct backing_dev_info *bdi)
> bdi->min_ratio = 0;
> bdi->max_ratio = 100;
> bdi->max_prop_frac = PROP_FRAC_BASE;
> - init_waitqueue_head(&bdi->wait);
> INIT_LIST_HEAD(&bdi->bdi_list);
> - INIT_LIST_HEAD(&bdi->b_io);
> - INIT_LIST_HEAD(&bdi->b_dirty);
> - INIT_LIST_HEAD(&bdi->b_more_io);
> + bdi->wb_mask = bdi->wb_active = 0;
> +
> + bdi_wb_init(&bdi->wb, bdi);
>
> for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
> err = percpu_counter_init(&bdi->bdi_stat[i], 0);
> @@ -469,9 +543,7 @@ void bdi_destroy(struct backing_dev_info *bdi)
> {
> int i;
>
> - WARN_ON(!list_empty(&bdi->b_dirty));
> - WARN_ON(!list_empty(&bdi->b_io));
> - WARN_ON(!list_empty(&bdi->b_more_io));
> + WARN_ON(bdi_has_dirty_io(bdi));
>
> bdi_unregister(bdi);
>
Honza
--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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