[PATCH v4 0/2] fs, audit: Avoid excessive dput/dget in audit_context setup and reset paths

 v4:
  - Add ack and review tags
  - Simplify put_fs_pwd_pool() in patch 1 as suggested by Paul Moore

 v3:
  - https://lore.kernel.org/lkml/[email protected]/

When the audit subsystem is enabled, it can do a lot of get_fs_pwd()
calls to get references to fs->pwd and then releasing those references
back with path_put() later. That may cause a lot of spinlock contention
on a single pwd's dentry lock because of the constant changes to the
reference count when there are many processes on the same working
directory actively doing open/close system calls. This can cause
noticeable performance regresssion when compared with the case where
the audit subsystem is turned off especially on systems with a lot of
CPUs which is becoming more common these days.

This patch series aim to avoid this type of performance regression caused
by audit by adding a new set of fs_struct helpers to reduce unncessary
path_get() and path_put() calls and the audit code is modified to use
these new helpers.

Waiman Long (2):
  fs: Add a pool of extra fs->pwd references to fs_struct
  audit: Use the new {get,put}_fs_pwd_pool() APIs to get/put pwd
    references

 fs/fs_struct.c            | 26 +++++++++++++++++++++-----
 fs/namespace.c            |  8 ++++++++
 include/linux/fs_struct.h | 28 +++++++++++++++++++++++++++-
 kernel/auditsc.c          |  7 +++++--
 4 files changed, 61 insertions(+), 8 deletions(-)

-- 
2.53.0