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Date: Mon, 9 Oct 2017 13:03:32 +0200 From: Jan Kara <jack@...e.cz> To: Yafang Shao <laoar.shao@...il.com> Cc: Jan Kara <jack@...e.cz>, Andrew Morton <akpm@...ux-foundation.org>, mhocko@...e.com, Johannes Weiner <hannes@...xchg.org>, vdavydov.dev@...il.com, jlayton@...hat.com, nborisov@...e.com, Theodore Ts'o <tytso@....edu>, mawilcox@...rosoft.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org, axboe@...nel.dk Subject: Re: [PATCH] mm/page-writeback.c: fix bug caused by disable periodic writeback On Mon 09-10-17 18:44:23, Yafang Shao wrote: > 2017-10-09 17:56 GMT+08:00 Jan Kara <jack@...e.cz>: > > On Sat 07-10-17 06:58:04, Yafang Shao wrote: > >> After disable periodic writeback by writing 0 to > >> dirty_writeback_centisecs, the handler wb_workfn() will not be > >> entered again until the dirty background limit reaches or > >> sync syscall is executed or no enough free memory available or > >> vmscan is triggered. > >> So the periodic writeback can't be enabled by writing a non-zero > >> value to dirty_writeback_centisecs > >> As it can be disabled by sysctl, it should be able to enable by > >> sysctl as well. > >> > >> Signed-off-by: Yafang Shao <laoar.shao@...il.com> > >> --- > >> mm/page-writeback.c | 8 +++++++- > >> 1 file changed, 7 insertions(+), 1 deletion(-) > >> > >> diff --git a/mm/page-writeback.c b/mm/page-writeback.c > >> index 0b9c5cb..e202f37 100644 > >> --- a/mm/page-writeback.c > >> +++ b/mm/page-writeback.c > >> @@ -1972,7 +1972,13 @@ bool wb_over_bg_thresh(struct bdi_writeback *wb) > >> int dirty_writeback_centisecs_handler(struct ctl_table *table, int write, > >> void __user *buffer, size_t *length, loff_t *ppos) > >> { > >> - proc_dointvec(table, write, buffer, length, ppos); > >> + unsigned int old_interval = dirty_writeback_interval; > >> + int ret; > >> + > >> + ret = proc_dointvec(table, write, buffer, length, ppos); > >> + if (!ret && !old_interval && dirty_writeback_interval) > >> + wakeup_flusher_threads(0, WB_REASON_PERIODIC); > >> + > > > > I agree it is good to schedule some writeback. However Jens has some > > changes queued in linux-block tree in this area so your change won't apply. > > So please base your changes on his tree. > > > > Do you mean this tree > git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git ? > > I have checked his tree and find nothing need to change on my patch. Yes, I mean that tree. Check the wb_start_all branch. Honza -- Jan Kara <jack@...e.com> SUSE Labs, CR
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