Hello,
(cc'ing Jan)
On Mon, Mar 14, 2016 at 05:09:00PM +0100, Michal Hocko wrote:
> On Sun 13-03-16 23:22:23, Tetsuo Handa wrote:
> [...]
>
> I am not familiar with the writeback code so I might be missing
> something essential here but why are we even queueing more and more
> work without checking there has been enough already scheduled or in
> progress.
>
> Something as simple as:
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index 6915c950e6e8..aa52e23ac280 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -887,7 +887,7 @@ void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
> {
> struct wb_writeback_work *work;
>
> - if (!wb_has_dirty_io(wb))
> + if (!wb_has_dirty_io(wb) || writeback_in_progress(wb))
> return;
I'm not sure this would be safe. It shouldn't harm correctness as
wb_start_writeback() isn't used in sync case but this might change
flush behavior in various ways. Dropping GFP_ATOMIC as suggested by
Tetsuo is likely better.
Thanks.
--
tejun
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