Re: [PATCH] [8/16] HWPOISON: Use bitmask/action code for try_to_unmap behaviour

Nick Piggin
2009-06-09T09:57:32Z

On Wed, Jun 03, 2009 at 08:46:41PM +0200, Andi Kleen wrote:
>
> try_to_unmap currently has multiple modi (migration, munlock, normal unmap)
> which are selected by magic flag variables. The logic is not very straight
> forward, because each of these flag change multiple behaviours (e.g.
> migration turns off aging, not only sets up migration ptes etc.)
> Also the different flags interact in magic ways.
>
> A later patch in this series adds another mode to try_to_unmap, so
> this becomes quickly unmanageable.
>
> Replace the different flags with a action code (migration, munlock, munmap)
> and some additional flags as modifiers (ignore mlock, ignore aging).
> This makes the logic more straight forward and allows easier extension
> to new behaviours. Change all the caller to declare what they want to
> do.
>
> This patch is supposed to be a nop in behaviour. If anyone can prove
> it is not that would be a bug.
>
> Cc: Lee.Schermerhorn@hp.com
> Cc: npiggin@suse.de
>
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
>
> ---
> include/linux/rmap.h | 14 +++++++++++++-
> mm/migrate.c | 2 +-
> mm/rmap.c | 40 ++++++++++++++++++++++------------------
> mm/vmscan.c | 2 +-
> 4 files changed, 37 insertions(+), 21 deletions(-)
>
> Index: linux/include/linux/rmap.h
> ===================================================================
> --- linux.orig/include/linux/rmap.h 2009-06-03 19:36:23.000000000 +0200
> +++ linux/include/linux/rmap.h 2009-06-03 20:39:50.000000000 +0200
> @@ -84,7 +84,19 @@
> * Called from mm/vmscan.c to handle paging out
> */
> int page_referenced(struct page *, int is_locked, struct mem_cgroup *cnt);
> -int try_to_unmap(struct page *, int ignore_refs);
> +
> +enum ttu_flags {
> + TTU_UNMAP = 0, /* unmap mode */
> + TTU_MIGRATION = 1, /* migration mode */
> + TTU_MUNLOCK = 2, /* munlock mode */
> + TTU_ACTION_MASK = 0xff,
> +
> + TTU_IGNORE_MLOCK = (1 << 8), /* ignore mlock */
> + TTU_IGNORE_ACCESS = (1 << 9), /* don't age */
> +};
> +#define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)

I still think this is nasty and should work like Gfp flags.