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SubjectRe: [PATCH 3/7] writeback: only use bdi_writeback_all() for WB_SYNC_NONE writeout
On Mon 14-09-09 11:36:30, Jens Axboe wrote:
> Data integrity writeback must use bdi_start_writeback() and ensure
> that wbc->sb and wbc->bdi are set.
This patch looks good.
Acked-by: Jan Kara <jack@suse.cz>

Honza

>
> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
> ---
> fs/fs-writeback.c | 69 ++++++++++------------------------------------------
> 1 files changed, 14 insertions(+), 55 deletions(-)
>
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index 1873fd0..5d4bd1c 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -187,7 +187,8 @@ static void bdi_wait_on_work_clear(struct bdi_work *work)
> TASK_UNINTERRUPTIBLE);
> }
>
> -static struct bdi_work *bdi_alloc_work(struct writeback_control *wbc)
> +static void bdi_alloc_queue_work(struct backing_dev_info *bdi,
> + struct writeback_control *wbc)
> {
> struct bdi_work *work;
>
> @@ -195,7 +196,7 @@ static struct bdi_work *bdi_alloc_work(struct writeback_control *wbc)
> if (work)
> bdi_work_init(work, wbc);
>
> - return work;
> + bdi_queue_work(bdi, work);
> }
>
> void bdi_start_writeback(struct writeback_control *wbc)
> @@ -205,11 +206,9 @@ void bdi_start_writeback(struct writeback_control *wbc)
> * bdi_queue_work() will wake up the thread and flush old data. This
> * should ensure some amount of progress in freeing memory.
> */
> - if (wbc->sync_mode != WB_SYNC_ALL) {
> - struct bdi_work *w = bdi_alloc_work(wbc);
> -
> - bdi_queue_work(wbc->bdi, w);
> - } else {
> + if (wbc->sync_mode != WB_SYNC_ALL)
> + bdi_alloc_queue_work(wbc->bdi, wbc);
> + else {
> struct bdi_work work;
>
> bdi_work_init(&work, wbc);
> @@ -840,67 +839,26 @@ int bdi_writeback_task(struct bdi_writeback *wb)
> }
>
> /*
> - * 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.
> + * Schedule writeback for all backing devices. Can only be used for
> + * WB_SYNC_NONE writeback, WB_SYNC_ALL should use bdi_start_writeback()
> + * and pass in the superblock.
> */
> 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:
> + WARN_ON(wbc->sync_mode == WB_SYNC_ALL);
> +
> 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);
> + bdi_alloc_queue_work(bdi, wbc);
> }
>
> 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);
> - }
> }
>
> /*
> @@ -1157,6 +1115,7 @@ long sync_inodes_sb(struct super_block *sb)
> {
> struct writeback_control wbc = {
> .sb = sb,
> + .bdi = sb->s_bdi,
> .sync_mode = WB_SYNC_ALL,
> .range_start = 0,
> .range_end = LLONG_MAX,
> @@ -1164,7 +1123,7 @@ long sync_inodes_sb(struct super_block *sb)
> long nr_to_write = LONG_MAX; /* doesn't actually matter */
>
> wbc.nr_to_write = nr_to_write;
> - bdi_writeback_all(&wbc);
> + bdi_start_writeback(&wbc);
> wait_sb_inodes(&wbc);
> return nr_to_write - wbc.nr_to_write;
> }
> --
> 1.6.4.1.207.g68ea
>
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR


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