Hi Yunlei, > -----Original Message----- > From: He YunLei [mailto:heyun...@huawei.com] > Sent: Tuesday, February 23, 2016 3:03 PM > To: Chao Yu; jaeg...@kernel.org; linux-f2fs-devel@lists.sourceforge.net > Cc: bintian.w...@huawei.com; 'Biao He' > Subject: Re: [f2fs-dev] [PATCH] f2fs: avoid hungtask problem caused by losing > wake_up > > On 2016/2/23 13:44, Chao Yu wrote: > > Hi Yunlei, > Hi Chao, > > > >> -----Original Message----- > >> From: Yunlei He [mailto:heyun...@huawei.com] > >> Sent: Tuesday, February 23, 2016 12:08 PM > >> To: chao2...@samsung.com; jaeg...@kernel.org; > >> linux-f2fs-devel@lists.sourceforge.net > >> Cc: bintian.w...@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.
Could this reproducible? If it could, could you please share the details. And did this occur in a huge size f2fs image? > >> > >> 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. Got it. The patch can fix issue that checkpointer will wait forever in case of write_end_io was failed to call wake_up for some reason. But I doubt more that the reason we are stuck is there are remained pages cached in bio buffer without being submitted. To make sure, maybe in wait_on_all_pages_writeback we could add print info to see whether sbi->write_io[].bio is valid or not. Thanks, > > > > >> io_schedule(); > >> > >> Signed-off-by: Yunlei He <heyun...@huawei.com> > >> Signed-off-by: Biao He <hebi...@huawei.com> > >> --- > >> 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 _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
