Date: Thu, 10 Sep 2009 12:13:29 +0300 From: Jaakko Heinonen <jh@saunalahti.fi> To: Mel Flynn <mel.flynn+fbsd.current@mailing.thruhere.net> Cc: freebsd-current@freebsd.org, Pawel Jakub Dawidek <pjd@freebsd.org>, Jeff Blank <jfb@mr-happy.com> Subject: Re: 8.0-BETA4 panic: ffs_sync: rofs mod Message-ID: <20090910091329.GA2726@a91-153-125-115.elisa-laajakaista.fi> In-Reply-To: <200909090902.34055.mel.flynn%2Bfbsd.current@mailing.thruhere.net> References: <20090908202553.GA1368@mr-happy.com> <20090908235731.GG1539@garage.freebsd.pl> <20090909005504.GA12660@mr-happy.com> <200909090902.34055.mel.flynn%2Bfbsd.current@mailing.thruhere.net>
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On 2009-09-09, Mel Flynn wrote: > This problem has also been seen on -questions [1] and I forgot to follow > up after time issues. According to the poster it's easy to reproduce: > - have a mountpoint in /etc/fstab with ro options > - unmount the mountpoint > - remount using -o rw This has been also reported as PR kern/133614. I have tried to reproduce the problem earlier but I didn't succeed until now. Here's how to reproduce it: 1. Have mountd(8) running 2. # mdconfig -a -t vnode -f ufsimg 3. # mount -o ro,rw /dev/md0 /mnt 4. # touch /mnt/foo && sync This is what's going on: Initial nmount() is done with "ro" and "rw" options. The mount point will have "ro", "rw" and "noro" string mount options after nmount(). MNT_RDONLY flag is not set. Then mountd(8) calls nmount() with "update" and "export" string options. This results FFS code to re-mount the file system as read-only because the "ro" string option is active for the mount point. ffs_mount() sets MNT_RDONLY and FFS fs_ronly flags. MNT_RDONLY gets later cleared in vfs_domount() because vfs_export() fails with ENOENT but the fs_ronly flag stays enabled. The most obvious problem seems to be that both "ro" and "rw" options are allowed to enter to mount point options concurrently. I don't have yet a fix to propose. -- Jaakko
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