Date: Fri, 30 Sep 2016 09:34:47 -0500 From: "Dean E. Weimer" <dweimer@dweimer.net> To: FreeBSD Stable <freebsd-stable@freebsd.org> Cc: owner-freebsd-stable@freebsd.org Subject: Re: File Name Too Long? Message-ID: <c522f5de02a7e101be4c7e1b1ed85b70@dweimer.net> In-Reply-To: <974bc572bedda786fdc18a41085952c1@dweimer.net> References: <974bc572bedda786fdc18a41085952c1@dweimer.net>
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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/
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