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. >> >> 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 <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
