.. _Miscellaneous Notes:

===================
Miscellaneous Notes
===================

Remove superfluous "__" type functions
======================================

* There is presedent here https://lore.kernel.org/all/20220607011647.24105-7-kch@nvidia.com/
* There is no layering violation in sysctl as there is only one layer!
* Usually there is additional logic in the function before calling __function.
  Not the case in sysctl
* Are these layers here because they look good? It is not clear why we have the
  layers here.
* Biggest change is that __do_proc_dointvec becomes non-static

Delete the *conv_param structures
=================================

* The \*data parameter is passed around throughout all kernel/sysctl.c
* Only 3 out of the 8 converter functions (\*_conv) use the data: These
  functions do not have table as their argument; We don't have access to
  ->extra{1,2}
    - proc_dointvec_minmax_conv
    - proc_douintvec_minmax_conv
    - do_proc_dointvec_ms_jiffies_minmax_conv
* This data is only used to signify min and max values for special cases
* In **all** the cases where \*data is used, it came from table->extra{1,2}

[PATCH v4] sysctl: expose sysctl_check_table for unit testing and use it
========================================================================
* its in V4
* Put it in sysctl-testing on 21 Feb 25
* `sysctl_check_table for unit testing discussion`_
* Review latest version

* 20241224171124.3676538-1-jsperbeck@google.com
* Remove the tests from kunit and move it to lib/test_sysctl.c

.. _sysctl_check_table for unit testing discussion:
   https://lore.kernel.org/20250121213354.3775644-1-jsperbeck@google.com

[PATCH v2 0/6] Fixes multiple sysctl bound checks
=================================================

* core/{iwcm,ucma}.c are upstreamed through the `rdma tree`_
* drivers/scsi/scsi_sysctl.c upstreamed through the scsi-stating tree
* fs/lockd/svc.c applied commit id 8e6d33ea0159b39d670b7986324bd6135ee9d5f7

* Sent reviews
  - Asked to see if the patches can move into mainline through other
    subsystems
  - asked to change coda_timeout to unsinged int.

* When a ctl_table->data is unsigned int* and uses a proc_dointvec as its
  proc_handler on a write, data silently gets cast from unsigned int* into
  singed int* (kernel/sysctl.c (__do_proc_dointvec) [i = (int *) tbl_data])
  and from unsinged long into singed int (kernel/sysctl.c (proc_dointvec_conv)
  [WRITE_ONCE(*valp, *lvalp)] )

* The issue in 3b3376f222e3 ("sysctl.c: fix underflow value setting risk in vm_table")
  was that the extra1 value was getting ignored because it was calling
  proc_dointvec. replacing with proc_dointvec_minmax properly forwards the
  extra1 value.
  What is happening in this series is not the same because no extra{1,2}
  values where set in any of the places touched by this series.
  The extra{1,2} variables are ignored when proc_dointvec is used as a
  proc_handler. Values of NULL, NULL are passed to conv and data arguments
  (this is where extra{1,2} should be forwared).

* hpet_max_freq -> unsigned int
  default_backlog -> unsinged int
  max_backlog -> unsigned int
  scsi_logging_level -> unsigned int
  nsm_local_state -> unsigned int
  nfs_idmap_cache_timeout -> unsigned int
  coda_timeout -> **unsigned long**

.. _rdma tree: https://web.git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git/commit/?h=wip/leon-for-next&id=f33cd9b3fd03a791296ab37550ffd26213a90c4e

[PATCH v2] drop_caches: re-enable message after disabling
=========================================================
* 20250216100514.3948-1-rwchen404@gmail.com
* Sent Luis' fix to the list
* Currently in sysctl-next.
* Will wait till after the merge window to push this
* posted a V2 with a toggle solution. Was not well received.

.. code-block:: diff

  diff --git i/fs/drop_caches.c w/fs/drop_caches.c
  index d45ef541d848..501b9f690445 100644
  --- i/fs/drop_caches.c
  +++ w/fs/drop_caches.c
  @@ -73,7 +73,7 @@ int drop_caches_sysctl_handler(const struct ctl_table *table, int write,
                                  current->comm, task_pid_nr(current),
                                  sysctl_drop_caches);
                  }
  -               stfu |= sysctl_drop_caches & 4;
  +               stfu = sysctl_drop_caches & 4;
          }
          return 0;
   }

Macro to generate bidirectional converters
==========================================

.. code-block:: diff
      sysctl: Use GEN_PROC_TYPE_CONV to generate bidirectional converters

      Add GEN_PROC_TYPE_CONV to generate bidirectional converter
      functions for sysctl operations. The macro takes suffix, type,
      user-to-kernel and kernel-to-user converter functions, and range check
      parameters to create do_proc_*_conv functions that call the appropriate
      proc_*_conv function.

      This is a preparation commit; the macro will be used as the converter
      functions get created.

      Signed-off-by: Joel Granados <joel.granados@kernel.org>

  #define ARG_ bool *n,
  #define ARG_u
  #define VAR_ n,
  #define VAR_u
  #define GEN_PROC_TYPE_CONV(S, Q, T, u2k_conv, k2u_conv, R)        \
  int do_proc_##Q##T##_conv##S(ARG_##Q ulong *u_ptr, Q##T * k_ptr,  \
    int dir, const struct ctl_table *tbl)                           \
  {                                                                 \
    return proc_##Q##T##_conv(VAR_##Q u_ptr, k_ptr, dir, tbl, R,    \
      u2k_conv, k2u_conv);                                          \
  }