Hi, Here is a pair of patches for making the persistent ring buffer freeable. These were splitted from another series for improving persistent ring buffer [1].
[1] https://lore.kernel.org/all/173920222697.826592.3726270716809214055.stgit@devnote2/ Anyway, this series allows us to release the memory for the persistent ring buffer if it is not used anymore without changing kernel cmdline and reboot. This allows us to enable the persistent ring buffer by default boot, but disable it according to the user setting after boot and recycle the memory for the persistent ring buffer. This is important for the secure system which signs kernel cmdline with the kernel image, because user can not change the cmdline easily (usually, it is not possible unless changing kernel image.) Thus, to use the persistent ring buffer, we need to enable it by default on such system. However, in that case, some amount of memory is locked by the persistent ring buffer even if it is not used by user setting. This feature is useful for such case, because if user setting is disabled the persistent tracing, we can release the persistent ring buffer to free page pool. Thank you, --- Masami Hiramatsu (Google) (2): mm/memblock: Add reserved memory release function tracing: Freeable reserved ring buffer include/linux/mm.h | 1 + kernel/trace/trace.c | 13 ++++++++- kernel/trace/trace.h | 1 + mm/memblock.c | 72 ++++++++++++++++++++++++++++++++++++++++++-------- 4 files changed, 74 insertions(+), 13 deletions(-) -- Masami Hiramatsu (Google) <mhira...@kernel.org>
