[PATCH 0/8] reexport lock fixes v2

J. Bruce Fields
2021-08-16T14:01:40Z

The following fix up some problems that can cause crashes or silently
broken lock guarantees in the reexport case.

Not fixed:
- Attempts to reclaim locks after a reboot of the reexport
server will fail. This at least seems like an improvement
over the current situation, which is that they'll succeed even
in cases where they shouldn't. Complete support for reboot
recovery is a bigger job.

- NFSv4.1+ lock nofications don't work. So, clients have to
poll as they do with NFSv4.0, which is suboptimal, but correct
(and an improvement over the current situation, which is a
kernel oops).

So what we have at this point is a suboptimal lock implementation that
doesn't support lock recovery.

Another alternative might be to turn off file locking entirely in the
re-export case. I'd rather take the incremental improvement and fix the
oopses.

Changes since v1:
- Use ENOGRACE instead of returning NFS-specific error from vfs lock
method.
- Take write opens for write locks in the NLM case (as we always
have in the NFSv4 case).
- Don't block NLM threads waiting for blocking locks.

With those changes I'm passing connecthon tests for NFSv3-4.2 reexports
of an NFSv4.0 filesystem.

--b.

J. Bruce Fields (8):
lockd: lockd server-side shouldn't set fl_ops
nlm: minor nlm_lookup_file argument change
nlm: minor refactoring
lockd: update nlm_lookup_file reexport comment
Keep read and write fds with each nlm_file
nfs: don't atempt blocking locks on nfs reexports
lockd: don't attempt blocking locks on nfs reexports
nfs: don't allow reexport reclaims

fs/lockd/svc4proc.c | 6 +-
fs/lockd/svclock.c | 80 +++++++++++++----------
fs/lockd/svcproc.c | 6 +-
fs/lockd/svcsubs.c | 125 +++++++++++++++++++++++++-----------
fs/nfs/export.c | 2 +-
fs/nfs/file.c | 3 +
fs/nfsd/lockd.c | 8 ++-
fs/nfsd/nfs4state.c | 11 +++-
fs/nfsd/nfsproc.c | 1 +
include/linux/errno.h | 1 +
include/linux/exportfs.h | 2 +
include/linux/fs.h | 1 +
include/linux/lockd/bind.h | 3 +-
include/linux/lockd/lockd.h | 13 ++--
14 files changed, 177 insertions(+), 85 deletions(-)

--
2.31.1