svn commit: r318736 - in head: cddl/lib/libzfs contrib/compiler-rt/lib/sanitizer_common contrib/openbsm/libbsm include lib/libarchive lib/libc/gen lib/libc/include lib/libc/sys lib/libkvm lib/libmi...

[Konstantin Belousov]

On Tue, Mar 12, 2019 at 03:58:31PM -0600, Alan Somers wrote:
> On Tue, May 23, 2017 at 3:29 AM Konstantin Belousov <kib at freebsd.org> wrote:
> >
> > Author: kib
> > Date: Tue May 23 09:29:05 2017
> > New Revision: 318736
> > URL: https://svnweb.freebsd.org/changeset/base/318736
> >
> > Log:
> >   Commit the 64-bit inode project.
> >
> >   Extend the ino_t, dev_t, nlink_t types to 64-bit ints.  Modify
> >   struct dirent layout to add d_off, increase the size of d_fileno
> >   to 64-bits, increase the size of d_namlen to 16-bits, and change
> >   the required alignment.  Increase struct statfs f_mntfromname[] and
> >   f_mntonname[] array length MNAMELEN to 1024.
> >
> >   ABI breakage is mitigated by providing compatibility using versioned
> >   symbols, ingenious use of the existing padding in structures, and
> >   by employing other tricks.  Unfortunately, not everything can be
> >   fixed, especially outside the base system.  For instance, third-party
> >   APIs which pass struct stat around are broken in backward and
> >   forward incompatible ways.
> >
> >   Kinfo sysctl MIBs ABI is changed in backward-compatible way, but
> >   there is no general mechanism to handle other sysctl MIBS which
> >   return structures where the layout has changed. It was considered
> >   that the breakage is either in the management interfaces, where we
> >   usually allow ABI slip, or is not important.
> >
> >   Struct xvnode changed layout, no compat shims are provided.
> >
> >   For struct xtty, dev_t tty device member was reduced to uint32_t.
> >   It was decided that keeping ABI compat in this case is more useful
> >   than reporting 64-bit dev_t, for the sake of pstat.
> >
> >   Update note: strictly follow the instructions in UPDATING.  Build
> >   and install the new kernel with COMPAT_FREEBSD11 option enabled,
> >   then reboot, and only then install new world.
> >
> >   Credits: The 64-bit inode project, also known as ino64, started life
> >   many years ago as a project by Gleb Kurtsou (gleb).  Kirk McKusick
> >   (mckusick) then picked up and updated the patch, and acted as a
> >   flag-waver.  Feedback, suggestions, and discussions were carried
> >   by Ed Maste (emaste), John Baldwin (jhb), Jilles Tjoelker (jilles),
> >   and Rick Macklem (rmacklem).  Kris Moore (kris) performed an initial
> >   ports investigation followed by an exp-run by Antoine Brodin (antoine).
> >   Essential and all-embracing testing was done by Peter Holm (pho).
> >   The heavy lifting of coordinating all these efforts and bringing the
> >   project to completion were done by Konstantin Belousov (kib).
> >
> >   Sponsored by: The FreeBSD Foundation (emaste, kib)
> >   Differential revision:        https://reviews.freebsd.org/D10439
> 
> What's the purpose of the new dirent.d_off field?  I can't find any
> code that uses it.
It is supposed to help NFS server.  They are supposed to provide directly the
cookies for nfs readdir call. But it is not required, and corresponding
code was not committed to FreeBSD fs/nfs yet.

> I'm wondering if the fuse(4) module should set it
> in order to work properly over NFS, or something.

No, it is not strictly required.  OTOH, there is userspace implementation
of NFS server which seems to make use of it when available.  This is why
r340431 was done.