Fix MNAMELEN or reimplement struct statfs

[mdf at FreeBSD.org]

On Sat, Jun 8, 2013 at 3:52 PM, Dirk Engling <erdgeist at erdgeist.org> wrote:

> The arbitrary value
>
> #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 */
> };
>
> currently bites us when trying to use poudriere with errors like
>
> 'mount: tmpfs: File name too long'
>
>
> /poudriere/data/build/91_RELEASE_amd64-REALLY-REALLY-LONG-JAILNAME/ref/wrkdirs
>
> The topic has been discussed several times since 2004 and has been
> postponed each time, the last time when it hit zfs users:
>
> http://lists.freebsd.org/pipermail/freebsd-fs/2010-March/007974.html
>
> So I'd like to point to the calendar, it's 2013 already and there's
> still a static arbitrary (and way too low) limit in one of the core
> areas of the vfs code.
>
> So I'd like to bump the issue and propose either making f_mntfromname a
> dynamic allocation or just increase MNAMELEN, using 10.0 as water shed.
>

Gleb Kurtsou did this along with the ino64 GSoC project.  Unfortunately,
 both he and I hit ENOTIME due to the job that pays the bills and it's
never made it back to the main repository.

IIRC, though, the only reason for doing it with 64-bit ino_t is that he'd
already finished changing the stat/dirent ABI so what was one more.  I
think he went with 1024 bytes, which also necessitated not allocating
statfs on the stack for the kernel.

Cheers,
matthew