Date: Fri, 30 Sep 2016 14:39:06 +0000 From: Priyadarshan <bsd@bontempi.net> To: "Dean E. Weimer" <dweimer@dweimer.net>, FreeBSD Stable <freebsd-stable@freebsd.org> Cc: owner-freebsd-stable@freebsd.org Subject: Re: File Name Too Long? Message-ID: <1475246346.1079471.741974313.29D6C2CB@webmail.messagingengine.com> In-Reply-To: <c522f5de02a7e101be4c7e1b1ed85b70@dweimer.net> References: <974bc572bedda786fdc18a41085952c1@dweimer.net> <c522f5de02a7e101be4c7e1b1ed85b70@dweimer.net>
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On Fri, 30 Sep 2016, at 14:34, Dean E. Weimer wrote: > On 2016-09-29 9:32 am, Dean E. Weimer wrote: > > I discovered, unfortunately by deleting a jail by accident, that my > > backup process isn't working. At least it was only the operating > > system part of the jail, I still have all the data so I just need to > > reinstall the operating system. While the ports are in the process of > > building I started to investigate the cause, because the backup logs > > report everything was fine. > > > > I have a custom pre-backup script I wrote that takes snapshots of my > > ZFS datasets, and then mounts those under /mnt/backup with nullfs > > mount points to the .zfs/snapshot/.. directories then I back them up > > rather than the live file system, allowing me to stop some services > > that don't restore from a running state correctly and then restart > > after the snapshot so downtime is only a couple of minutes instead of > > full length of backups. > > > > It appeared to be running perfectly, without errors, but apparently > > the script isn't reporting some nullfs mount failures, so why are the > > failing, turns out it thinks the file name is too long? but looking at > > the mount(2) man page it states this: > > > > [ENAMETOOLONG] A component of a pathname exceeded 255 characters, > > or > > the entire length of a path name exceeded 1023 > > characters. > > > > I can see that at some point under this, I may reach that 1023 limit, > > but what of the total 71 characters in this path has a problem? > > > > /jails/unifi/ROOT/.zfs/snapshot/11.0-RELEASE-r306379-2016.09.28--bsnap > > > > root@freebsd:/jails/unifi/ROOT/.zfs/snapshot # ls > > ls: 11.0-RELEASE-r306379-2016.09.28--bsnap: File name too long > > > > I thought, maybe its a ZFS specific error, and ran across this: > > http://lists.freebsd.org/pipermail/freebsd-fs/2010-March/007964.html > > > > [..snip..] > > From looking at the code, I think you hitting this limit: > > > > /* > > * Be ultra-paranoid about making sure the type and fspath > > * variables will fit in our mp buffers, including the > > * terminating NUL. > > */ > > if (strlen(fstype) >= MFSNAMELEN || strlen(fspath) >= MNAMELEN) > > return (ENAMETOOLONG); > > > > in vfs_domount() or vfs_donmount(). > > > > This is FreeBSD limit caused by statfs structure: > > > > /* > > * filesystem statistics > > */ > > [...] > > #define MNAMELEN 88 /* size of on/from name bufs */ > > [...] > > struct statfs { > > [...] > > char f_mntfromname[MNAMELEN];/* mounted filesystem */ > > char f_mntonname[MNAMELEN]; /* directory on which mounted */ > > }; > > > > When you list .zfs/snapshot/ directory (especially with -l option) ZFS > > mounts snapshots on lookup and this is this mount that fails. > > [..snip..] > > > > I can seemingly due anything else with the snapshot, clone, send, > > receive its just that I am unable to access the files on it through > > .zfs/snapshot/.. > > > > I am trying to find what the limit is here from this, because this one > > here works. > > > > /jails/webmail/usr-local-subversion/.zfs/snapshot/usr-local-subversion--bsnap > > > > its longer in total length than most of the ones that are failing. > > > > /jails/unifi/ROOT/.zfs/snapshot/11.0-RELEASE-r306379-2016.09.28--bsnap > > > > So it appears that its in the name, and not the mount point. > > > > this one works as well, which is my ZFS boot environment on the main > > system > > zraid/ROOT/11.0-RELEASE-r306379-2016.09.28 > > snapshot is /.zfs/snapshot/11.0-RELEASE-r306379-2016.09.28--bsnap > > > > So its not just the last component of the zfs dataset name, which is > > in this case the same. > > > > I am trying to wrap my head around this and find where the limit is so > > I can adjust my naming conventions used and actually get backups of > > all of my data. Turns out all of my jail operating system paths aren't > > being backed up, fortunately at least all of the data file systems for > > the jails are. > > I found a solution, I was naming the snapshots with the dataset name, > which I think was causing the issue. > > The following didn't seem to long to be an issue > /jails/unifi/ROOT/.zfs/snapshot/11.0-RELEASE-r306379-2016.09.28--bsnap > > But apparently the snapshot name was > zraid/jails/unifi/11.0-RELEASE-r306379-2016.09.28@11.0-RELEASE-r306379-2016.09.28--bsnap > > Still not sure how it adds up to too long, both full paths together > aren't over 255, at 160, but apparently something else is added in > there. I was able to easily modify my backup script to not include the > last part of the dataset in the snapshot name and simply use -bsnap-, as > the name. it appears to avoid all the issues, and my backups from last > night include all the files. > > /jails/unifi/ROOT/.zfs/snapshot/-bsnap- > zraid/jails/unifi/11.0-RELEASE-r306379-2016.09.28@-bsnap- > > The total path now only adds up to 98, I haven't done any testing yet to > find out where the limit is hit, The longest combination of these I had > last night would have added up to 135, and that worked > > -- > Thanks, > Dean E. Weimer > http://www.dweimer.net/ This may be related: http://iocage.readthedocs.io/en/latest/known-issues.html#character-mount-path-limitation Priyadarshan
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