Date: Mon, 14 Sep 2009 03:02:02 +0200 From: Mel Flynn <mel.flynn+fbsd.current@mailing.thruhere.net> To: freebsd-current@freebsd.org Cc: Jaakko Heinonen <jh@saunalahti.fi>, Pawel Jakub Dawidek <pjd@freebsd.org>, Jeff Blank <jfb@mr-happy.com> Subject: Re: 8.0-BETA4 panic: ffs_sync: rofs mod Message-ID: <200909140302.03003.mel.flynn%2Bfbsd.current@mailing.thruhere.net> In-Reply-To: <20090910091329.GA2726@a91-153-125-115.elisa-laajakaista.fi> References: <20090908202553.GA1368@mr-happy.com> <200909090902.34055.mel.flynn%2Bfbsd.current@mailing.thruhere.net> <20090910091329.GA2726@a91-153-125-115.elisa-laajakaista.fi>
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On Thursday 10 September 2009 11:13:29 Jaakko Heinonen wrote: > 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. Why does mountd(8) call nmount with update? As I read the above, any command line overrides done through umount/mount will be negated by having mountd running. That's a bit surprising. -- Mel
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