Re: [PATCH v3 0/5] sysctl: add typed field descriptors

[Alexey Gladkov <legion@kernel.org>]

On Sat, Sep 26, 2026 at 06:22:07PM +0200, Alexey Gladkov wrote:
> Hi,
> 
> Some sysctl users copy an otherwise static ctl_table for each namespace or
> device, then replace data and limit pointers before registration. Besides
> the per-instance allocation, these fixups often depend on table indices:
> reordering an entry without updating the fixup can silently bind it to the
> wrong data or limits.
> 
> This series lets such users describe a table once with static, read-only
> sysctl_field entries. Each field names a data type and an offset into an
> object selected by a sysctl_context at registration time. The offset
> helpers check the member type at build time. Limits and custom handlers
> remain optional properties of a field; the field type does not encode a
> choice of handler or whether limits are present. A subsystem that needs
> more than a namespace can embed sysctl_context in its own registration
> context.
> 
> The sysctl core keeps the context with the table header and materializes
> a ctl_table entry when an existing handler, permission check or BPF hook
> needs one. Legacy ctl_table registrations retain their own path, and
> subsystems can convert tables independently. The IPC, mqueue and ucount
> conversions here remove table copies without changing their backing data.
> 
> Changes since v2:
> 
> - Drop sysctl_uint_vals, as requested by Joel. Existing limit constants
>   suffice for these conversions.
> - Drop the *_MINMAX field types. A field's type now describes its data,
>   while optional min/max pointers supply bounds to the selected handler.
> - Keep __register_sysctl_table() and __register_sysctl_fields() as separate
>   registration paths, sharing only allocation and tree insertion helpers.
> - Address the sashiko findings: avoid calling mode_fn under sysctl_lock,
>   validate the effective maxlen against the context object, and reject
>   NO_DATA fields paired with standard handlers that require data.
> 
> This is the first part of the conversion. Network sysctls and other
> subsystem-specific users will follow in separate series for review by
> their maintainers.
> 
> 
> Alexey Gladkov (5):
>   proc: sysctl: address table entries by index
>   sysctl: add typed field descriptors
>   sysctl: ipc: use typed fields for IPC namespace sysctls
>   sysctl: mq: use typed fields for IPC namespace sysctls
>   sysctl: use typed fields for ucount limits

Gentle reminder about the patchset.

>  fs/proc/inode.c        |   2 +-
>  fs/proc/internal.h     |   2 +-
>  fs/proc/proc_sysctl.c  | 681 +++++++++++++++++++++++++++++------------
>  include/linux/sysctl.h | 138 ++++++++-
>  ipc/ipc_sysctl.c       | 189 +++++-------
>  ipc/mq_sysctl.c        | 104 +++----
>  kernel/ucount.c        |  64 ++--
>  7 files changed, 772 insertions(+), 408 deletions(-)
> 
> 
> base-commit: 587858367581b9c55c3690f4e63382ad622719d4
> -- 
> 2.55.0
> 

-- 
Rgrds, legion