[PATCH 0/2] avoid prepare_creds in faccessat when possible

From: Mateusz Guzik
Date: Mon Mar 09 2015 - 16:36:01 EST

Sometimes faccessat needs to modify current thread's credentials, but
calls prepare_creds unconditionally.

However, typically resulting credentials are identical to original ones
and in that case newcredentials are unnecessary. We can detect this before
allocating anything.

This patch series adds a helper which allows comparing capability sets and
modifies faccessat to use it.

Mateusz Guzik (2):
CAPABILITIES: add cap_isequal helper
fs: avoid unnecessary prepare_creds in faccessat

fs/open.c | 53 ++++++++++++++++++++++++++++++----------------
include/linux/capability.h | 10 +++++++++
2 files changed, 45 insertions(+), 18 deletions(-)


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