Re: [PATCH 5/7] writeback: inline allocation failure handling in bdi_alloc_queue_work()

Jan Kara
2009-09-14T13:13:42Z

On Mon 14-09-09 11:36:32, Jens Axboe wrote:
> This gets rid of work == NULL in bdi_queue_work() and puts the
> OOM handling where it belongs.
Looks good.

Acked-by: Jan Kara <jack@suse.cz>

Honza
>
> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
> ---
> fs/fs-writeback.c | 55 +++++++++++++++++++++++++++-------------------------
> 1 files changed, 29 insertions(+), 26 deletions(-)
>
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index d7592c7..5cd8b3b 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -139,21 +139,19 @@ static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *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);
> + 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();
> + /*
> + * 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);
> - }
> + 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
> @@ -165,14 +163,12 @@ static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
> 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
> + * End work now if this wb has no dirty IO pending. Otherwise
> + * wakeup the handling thread
> */
> - if (!wb_has_dirty_io(wb)) {
> - if (work)
> - wb_clear_pending(wb, work);
> - } else if (wb->task)
> + if (!wb_has_dirty_io(wb))
> + wb_clear_pending(wb, work);
> + else if (wb->task)
> wake_up_process(wb->task);
> }
> }
> @@ -192,11 +188,20 @@ static void bdi_alloc_queue_work(struct backing_dev_info *bdi,
> {
> 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)
> + if (work) {
> bdi_work_init(work, wbc);
> + bdi_queue_work(bdi, work);
> + } else {
> + struct bdi_writeback *wb = &bdi->wb;
>
> - bdi_queue_work(bdi, work);
> + if (wb->task)
> + wake_up_process(wb->task);
> + }
> }
>
> void bdi_start_writeback(struct writeback_control *wbc)
> @@ -852,10 +857,8 @@ static void bdi_writeback_all(struct writeback_control *wbc)
> rcu_read_lock();
>
> list_for_each_entry(bdi, &bdi_list, bdi_list) {
> - if (!bdi_has_dirty_io(bdi))
> - continue;
> -
> - bdi_alloc_queue_work(bdi, wbc);
> + if (bdi_has_dirty_io(bdi))
> + bdi_alloc_queue_work(bdi, wbc);
> }
>
> rcu_read_unlock();
> --
> 1.6.4.1.207.g68ea
>
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR