From: Christian Brauner Date: Wed, 12 Nov 2025 08:38:46 +0000 (+0100) Subject: Merge patch series "vfs: recall-only directory delegations for knfsd" X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=76c63ff12e067e1ff77b19a83c24774899ed01fc;p=thirdparty%2Flinux.git Merge patch series "vfs: recall-only directory delegations for knfsd" Jeff Layton says: At the fall NFS Bakeathon last week, the NFS client and server maintainers had a discussion about how to merge support for directory delegations. We decided to start with just merging support for simple, recallable-only directory delegation support, for a number of reasons: 1/ RFC8881 has some gaps in coverage that we are hoping to have addressed in RFC8881bis. In particular, it's written such that CB_NOTIFY callbacks require directory position information. That will be hard to do properly under Linux, so we're planning to extend the spec to allow that information to be omitted. 2/ client-side support for CB_NOTIFY still lags a bit. The client side is tricky, as it involves heuristics about when to request a delegation. 3/ we have some early indication that simple, recallable-only delegations can help performance in some cases. Anna mentioned seeing a multi-minute speedup in xfstests runs with them enabled. This needs more investigation, but it's promising and seems like enough justification to merge support. This patchset is quite similar to the set I initially posted back in early 2024. We've merged some GET_DIR_DELEGATION handling patches since then, but the VFS layer support is basically the same. One thing that I want to make clear is that with this patchset, userspace can request a read lease on a directory that will be recalled on conflicting accesses. I saw no reason to prevent this, and I think it may be something useful for applications like Samba. As always, users can disable leases altogether via the fs.leases-enable sysctl if this is an issue, but I wanted to point this out in case anyone sees footguns here. * patches from https://patch.msgid.link/20251111-dir-deleg-ro-v6-0-52f3feebb2f2@kernel.org: vfs: expose delegation support to userland nfsd: wire up GET_DIR_DELEGATION handling nfsd: allow DELEGRETURN on directories nfsd: allow filecache to hold S_IFDIR files filelock: lift the ban on directory leases in generic_setlease vfs: make vfs_symlink break delegations on parent dir vfs: make vfs_mknod break delegations on parent directory vfs: make vfs_create break delegations on parent directory vfs: clean up argument list for vfs_create() vfs: break parent dir delegations in open(..., O_CREAT) codepath vfs: allow rmdir to wait for delegation break on parent vfs: allow mkdir to wait for delegation break on parent vfs: add try_break_deleg calls for parents to vfs_{link,rename,unlink} filelock: push the S_ISREG check down to ->setlease handlers filelock: add struct delegated_inode filelock: rework the __break_lease API to use flags filelock: make lease_alloc() take a flags argument Link: https://patch.msgid.link/20251111-dir-deleg-ro-v6-0-52f3feebb2f2@kernel.org Signed-off-by: Christian Brauner --- 76c63ff12e067e1ff77b19a83c24774899ed01fc