From mboxrd@z Thu Jan 1 00:00:00 1970 From: He YunLei Subject: Re: [PATCH] f2fs: avoid hungtask problem caused by losing wake_up Date: Tue, 23 Feb 2016 15:02:40 +0800 Message-ID: <56CC0410.50103@huawei.com> References: <1456200476-9811-1-git-send-email-heyunlei@huawei.com> <009501d16dfd$52a518c0$f7ef4a40$@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from sog-mx-2.v43.ch3.sourceforge.com ([172.29.43.192] helo=mx.sourceforge.net) by sfs-ml-2.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1aY70D-0002Oe-Ug for linux-f2fs-devel@lists.sourceforge.net; Tue, 23 Feb 2016 07:03:21 +0000 Received: from szxga02-in.huawei.com ([119.145.14.65]) by sog-mx-2.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1aY70A-0005Ny-Nc for linux-f2fs-devel@lists.sourceforge.net; Tue, 23 Feb 2016 07:03:21 +0000 In-Reply-To: <009501d16dfd$52a518c0$f7ef4a40$@samsung.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net To: Chao Yu , jaegeuk@kernel.org, linux-f2fs-devel@lists.sourceforge.net Cc: 'Biao He' On 2016/2/23 13:44, Chao Yu wrote: > Hi Yunlei, Hi Chao, > >> -----Original Message----- >> From: Yunlei He [mailto:heyunlei@huawei.com] >> Sent: Tuesday, February 23, 2016 12:08 PM >> To: chao2.yu@samsung.com; jaegeuk@kernel.org; linux-f2fs-devel@lists.sourceforge.net >> Cc: bintian.wang@huawei.com; Yunlei He; Biao He >> Subject: [f2fs-dev] [PATCH] f2fs: avoid hungtask problem caused by losing wake_up >> >> The D state of wait_on_all_pages_writeback should be waken by >> function f2fs_write_end_io when all writeback pages have been >> succesfully written to device. It's possible that wake_up comes >> between get_pages and io_schedule. Maybe in this case it will >> lost wake_up and still in D state even if all pages have been >> write back to device, and finally, the whole system will be into >> the hungtask state. > > I haven't encountered such issue so far, do you suffer this in real > world? > yes, I have encounter it, the whole file system is blocked at function wait_on_all_pages_writeback beyond 120s when write cp, and no error reported by storage device driver. >> >> if (!get_pages(sbi, F2FS_WRITEBACK)) >> break; >> <--------- wake_up > > wake_up will put all tasks linked in sbi->cp_wait on run-queue, so > here it should be save to call io_schedule, after being rescheduled, > it will get the chance to check above condition to break out. > > Thanks, Here, we just doubt something weird may cause wait_on_all_pages_writeback could not be waken. Wake_up trigger only one time by last bio's end_io function, if the thread happen to miss it, the thread will be in D state forever. So we change the code to make wait_on_all_pages_writeback awaken periodically, then check the condition. > >> io_schedule(); >> >> Signed-off-by: Yunlei He >> Signed-off-by: Biao He >> --- >> fs/f2fs/checkpoint.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c >> index 2bac8a1..f55355d 100644 >> --- a/fs/f2fs/checkpoint.c >> +++ b/fs/f2fs/checkpoint.c >> @@ -920,7 +920,7 @@ static void wait_on_all_pages_writeback(struct f2fs_sb_info *sbi) >> if (!get_pages(sbi, F2FS_WRITEBACK)) >> break; >> >> - io_schedule(); >> + io_schedule_timeout(5*HZ); >> } >> finish_wait(&sbi->cp_wait, &wait); >> } >> -- >> 1.9.1 > > > > . > ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=272487151&iu=/4140