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Date: Mon, 21 Dec 2009 00:31:08 +0100 From: Petr Titěra <petr@...era.eu> To: john stultz <johnstul@...ibm.com> CC: linux-kernel@...r.kernel.org Subject: Re: Wrong atime on recent kernels Petr Titěra napsal(a): > john stultz napsal(a): >> On Thu, 2009-12-17 at 12:04 +0100, Petr TitĂ�ďż˝ra wrote: >>> john stultz napsal(a): >>>> On Wed, 2009-12-16 at 21:55 +0100, Petr TitĂ�ďż˝ra wrote: >>>>> john stultz napsal(a): >>>>>> 2009/12/14 Petr TitĂ�ďż˝ra <petr@...era.eu>: >>>>>>> Hello, >>>>>>> >>>>>>> I see some strange file modification times recently. It seems to me >>>>>>> that in some situations, kernel allows to set nanoseconds part >>>>>>> of file >>>>>>> access, modification or change time to 100000000 ns. Problem >>>>>>> seems to be in >>>>>>> some generic part of kernel because I see it on several different >>>>>>> filesysytems (ext4 and nilf2). These is I've got during my >>>>>>> testing on kernel >>>>>>> 2.6.32-tip-08309-gad8e75a. >>>>>>> >>>>>>> File: `./Documentation/dvb/contributors.txt' >>>>>>> Size: 3035 Blocks: 8 IO Block: 4096 regular file >>>>>>> Device: fe04h/65028d Inode: 818 Links: 1 >>>>>>> Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) >>>>>>> Access: 2009-12-14 10:29:04.1000000000 +0100 >>>>>>> Modify: 2009-12-14 10:29:04.1000000000 +0100 >>>>>>> Change: 2009-12-14 10:29:04.1000000000 +0100 >>>>>>> >>>>>>> See that all times of that file ends with 1e6 nanoseconds. >>>>> I did not test reverting this patch yet, because I did not find >>>>> reliable way how to reproduce these strange modify times. But as I >>>>> read your description. Would it be possible that if there would be >>>>> bug >>>>> in your patch i would be observer on mostly quiet system? I'm asking >>>>> because full day of testing of the system under load did not produce >>>>> any result, but then when I tried to run "find / | xargs stat" on >>>>> idle >>>>> system I've got several new instances of wrong access time >>>>> (filesystem >>>>> is mounted without noatime) >>>> Another quick question: >>>> >>>> What is the normal behavior you see when this issue is not cropping >>>> up? >>>> >>>> Do you normally see all 0's in the ns field? Or do you expect to >>>> see an >>>> actual ns value? >>>> >>> Sorry to reply again. Previous message did not get to list: >>> >>> I see values which seems to be ns times there. My root filesystem is >>> ext4 too (recently I do not remeber if I formated it from scratch >>> when I reinstalled that system) but I see this happen on other >>> filesystems too >>> >>> Root filesystem (ext4 may be converted from ext3) >>> >>> File: `/etc/sysconfig' >>> Size: 4096 Blocks: 8 IO Block: 4096 directory >>> Device: fe00h/65024d Inode: 65282 Links: 7 >>> Access: (0755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) >>> Access: 2009-12-16 21:14:00.172000000 +0100 >>> Modify: 2009-12-12 11:01:48.1000000000 +0100 >>> Change: 2009-12-12 11:01:48.1000000000 +0100 >>> File: `/etc/sysconfig/prelink' >>> Size: 1459 Blocks: 8 IO Block: 4096 regular file >>> Device: fe00h/65024d Inode: 22706 Links: 1 >>> Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) >>> Access: 2009-12-14 10:27:46.912000002 +0100 >>> Modify: 2004-11-23 11:43:08.000000000 +0100 >>> Change: 2009-12-08 22:57:24.656000002 +0100 >>> File: `/etc/sysconfig/i18n' >>> Size: 47 Blocks: 8 IO Block: 4096 regular file >>> Device: fe00h/65024d Inode: 48962 Links: 1 >>> Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) >>> Access: 2010-08-27 18:07:21.500013018 +0200 >>> Modify: 2009-06-22 23:33:43.113581313 +0200 >>> Change: 2009-06-22 23:58:39.936318201 +0200 >> >> So I'm not reproducing this with 2.6.33-rc1 on a fresh ext4 partition on >> x68_64. >> >> File: `virt' >> Size: 4096 Blocks: 8 IO Block: 4096 directory >> Device: 804h/2052d Inode: 1868440 Links: 3 >> Access: (0755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) >> Access: 2009-12-17 21:22:44.692710730 -0500 >> Modify: 2009-12-17 20:14:40.000000000 -0500 >> Change: 2009-12-17 21:20:21.001915208 -0500 >> File: `vmlinux' >> Size: 21122497 Blocks: 24136 IO Block: 4096 regular file >> Device: 804h/2052d Inode: 1874435 Links: 1 >> Access: (0755/-rwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) >> Access: 2009-12-17 21:22:05.381691121 -0500 >> Modify: 2009-12-17 21:22:05.376691754 -0500 >> Change: 2009-12-17 21:22:05.376691754 -0500 >> File: `vmlinux.o' >> Size: 16701780 Blocks: 32624 IO Block: 4096 regular file >> Device: 804h/2052d Inode: 1874418 Links: 1 >> Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) >> Access: 2009-12-17 21:22:01.138228732 -0500 >> Modify: 2009-12-17 21:22:01.131229619 -0500 >> Change: 2009-12-17 21:22:01.131229619 -0500 >> >> >> Let me know if you find anything that helps narrow this down. >> > Hello, > > I know its far fetched, but is there something what is preventing > xtime.tv_nsec to be exactly 999999999 near the end of update_wall_time > in kernel/time/timekeeping.c? > > Petr > Just to follow up. I'm asking because I see a lot of files with access and/or modify times near the top of thousanth of second (see `/etc/sysconfig/prelink' in my example) and I thing that addition of 1 to xtime.tv_nsec ath the end of update_wall_time can 'owerflow' to whole second. Petr > >> thanks >> -john >> >> >> > > -- > To unsubscribe from this list: send the line "unsubscribe > linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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