Date: Sun, 22 Feb 2009 13:00:52 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Carl <k0802647@telus.net> Cc: freebsd-fs@freebsd.org Subject: Re: UFS2 and/or sparse file bug causing copy process to land in 'D'' state? Message-ID: <20090222110052.GH41617@deviant.kiev.zoral.com.ua> In-Reply-To: <49A10626.8060705@telus.net> References: <49A10626.8060705@telus.net>
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[-- Attachment #1 --] On Sun, Feb 22, 2009 at 12:00:38AM -0800, Carl wrote: > I've come across what I'm thinking may be a bug in the context of > FreeBSD 7.0 with a pair of gmirrored drives and gjournaled partitions > when copying a large number of files into a file-backed memory device. > > The consequence of this problem is that a process enters the 'D' state > (process in disk) indefinitely, cannot be killed, and the system cannot > be shutdown. The only solution is to cold reboot the system, which is a > really big problem for remote systems. This is happening to me > intermittently with the standard tar-tar pipeline form of copying, but > has happened with the rsync 3.0.4 port as well. > > I would appreciate it if some of you would see if you can repeat this > problem. Here is a sequence of tcsh shell commands which manifest the > problem (on occasion but not every time), which I will refer to as the > "truncate sequence" (depends on fully populated /usr/src tree as data set): > > # truncate -s 671088640 target > # mdconfig -f target -S 512 -y 255 -x 63 -u 7 > # bsdlabel -w /dev/md7 auto > # newfs -O2 -m 0 -o space /dev/md7a > # mount /dev/md7a /media > # tar -cvf - -C /usr/src . | tar -xvpof - -C /media > # umount /media ; mdconfig -d -u 7 ; rm target > > An alternate version has yet to fail for me and involves replacing the > first line with this one: > > # dd if=/dev/zero of=target bs=1M count=640 > > I'll call that the "dd sequence". Here is an ordered series of tests I > just completed: > > a) Repeated truncate sequence 7 times - 1st, 5th, and 7th failed. > b) Repeated dd sequence 7 times - no failures. > c) Repeated truncate sequence 6 time - no failures. > d) Used following sequence to ensure all disk caches flushed: > > # dd if=/dev/random of=target bs=1M count=4096 > # dd if=target of=/dev/null bs=1M > # rm target > > e) Repeated truncate sequence 4 times - no failures. > f) Performed orderly reboot. > g) Repeated truncate sequence 2 times - 2nd failed. > h) Performed orderly reboot. > i) Repeated dd sequence 7 times - no failures. > > All failures involve the second tar in the pipeline hanging in the 'D' > state. In each case I do a cold reboot before proceeding with the next test. > > It's tempting to speculate that a bug exists in code related to handling > sparse files specifically, but perhaps it just raises the probability of > tripping a bug that would eventually manifest in the dd sequence as > well. OTOH, I don't know how to rule out a physical disk or disk > firmware problem. > > This problem has occurred with different data sets and different sized > memory disks, but only with the source and destination filesystems being > UFS2. I have done similar sequences with EXT2 and FAT16 destinations > with no failures thus far, but the memory disks and data sets were > smaller so it's conceivable that probability worked against me. > > I should note that the drives are Seagate ST31000340AS Barracudas, but > both drives have been upgraded to firmware version SD1A and are > therefore supposedly free of the infamous little horror Seagate > inflicted on so many of us. smartctl tells me that both disks still have > a raw value of 0 for Reallocated_Sector_Ct and both pass the "short" > self test. Please, see http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kerneldebug-deadlocks.html for instructions on how to gather the required information to diagnose the issue. [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iEYEARECAAYFAkmhMGMACgkQC3+MBN1Mb4iqVACePL6IH3cjmuxS/fBbA662oa6o 1oMAnjiIFXx8lUDtxWyr9TdEWDfnF5xf =7grU -----END PGP SIGNATURE-----help
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