From: Yafang Shao Date: Sat, 14 Oct 2017 08:38:27 +0000 (+0800) Subject: mm/page-writeback.c: make changes of dirty_writeback_centisecs take effect immediately X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=515c24c13c7ff1262cdb40fe631c6391e99c0996;p=openwrt%2Fstaging%2Fblogic.git mm/page-writeback.c: make changes of dirty_writeback_centisecs take effect immediately This patch is the followup of the prvious patch: [writeback: schedule periodic writeback with sysctl]. There's another issue to fix. For example, - When the tunable was set to one hour and is reset to one second, the new setting will not take effect for up to one hour. Kicking the flusher threads immediately fixes it. Cc: Jens Axboe Cc: Jan Kara Cc: Andrew Morton Signed-off-by: Yafang Shao Signed-off-by: Jens Axboe --- diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 622a18c114ca..c518c845f202 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -1976,7 +1976,16 @@ int dirty_writeback_centisecs_handler(struct ctl_table *table, int write, int ret; ret = proc_dointvec(table, write, buffer, length, ppos); - if (!ret && !old_interval && dirty_writeback_interval) + + /* + * Writing 0 to dirty_writeback_interval will disable periodic writeback + * and a different non-zero value will wakeup the writeback threads. + * wb_wakeup_delayed() would be more appropriate, but it's a pain to + * iterate over all bdis and wbs. + * The reason we do this is to make the change take effect immediately. + */ + if (!ret && write && dirty_writeback_interval && + dirty_writeback_interval != old_interval) wakeup_flusher_threads(WB_REASON_PERIODIC); return ret;