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SubjectRe: [PATCH 2/6] mm: differentiate unmap for vmscan from other unmap.
On Fri, 27 Jun 2014, Jérôme Glisse wrote:

> From: Jérôme Glisse <jglisse@redhat.com>
>
> New code will need to be able to differentiate between a regular unmap and
> an unmap trigger by vmscan in which case we want to be as quick as possible.
>
> Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
> ---
> include/linux/rmap.h | 15 ++++++++-------
> mm/memory-failure.c | 2 +-
> mm/vmscan.c | 4 ++--
> 3 files changed, 11 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/rmap.h b/include/linux/rmap.h
> index be57450..eddbc07 100644
> --- a/include/linux/rmap.h
> +++ b/include/linux/rmap.h
> @@ -72,13 +72,14 @@ struct anon_vma_chain {
> };
>
> enum ttu_flags {
> - TTU_UNMAP = 1, /* unmap mode */
> - TTU_MIGRATION = 2, /* migration mode */
> - TTU_MUNLOCK = 4, /* munlock mode */
> -
> - TTU_IGNORE_MLOCK = (1 << 8), /* ignore mlock */
> - TTU_IGNORE_ACCESS = (1 << 9), /* don't age */
> - TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
> + TTU_VMSCAN = 1, /* unmap for vmscan */
> + TTU_POISON = 2, /* unmap for poison */
> + TTU_MIGRATION = 4, /* migration mode */
> + TTU_MUNLOCK = 8, /* munlock mode */
> +
> + TTU_IGNORE_MLOCK = (1 << 9), /* ignore mlock */
> + TTU_IGNORE_ACCESS = (1 << 10), /* don't age */
> + TTU_IGNORE_HWPOISON = (1 << 11),/* corrupted page is recoverable */

Unless there is a deeper purpose that I am overlooking, I think it would
be better to leave the _MLOCK, _ACCESS, and _HWPOISON at their original
values. I just can't quite see why they would need to start at bit 9
instead of bit 8...

> };
>
> #ifdef CONFIG_MMU
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index a7a89eb..ba176c4 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -887,7 +887,7 @@ static int page_action(struct page_state *ps, struct page *p,
> static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
> int trapno, int flags, struct page **hpagep)
> {
> - enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
> + enum ttu_flags ttu = TTU_POISON | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
> struct address_space *mapping;
> LIST_HEAD(tokill);
> int ret;
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 6d24fd6..5a7d286 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1163,7 +1163,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone,
> }
>
> ret = shrink_page_list(&clean_pages, zone, &sc,
> - TTU_UNMAP|TTU_IGNORE_ACCESS,
> + TTU_VMSCAN|TTU_IGNORE_ACCESS,
> &dummy1, &dummy2, &dummy3, &dummy4, &dummy5, true);
> list_splice(&clean_pages, page_list);
> mod_zone_page_state(zone, NR_ISOLATED_FILE, -ret);
> @@ -1518,7 +1518,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
> if (nr_taken == 0)
> return 0;
>
> - nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP,
> + nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_VMSCAN,
> &nr_dirty, &nr_unqueued_dirty, &nr_congested,
> &nr_writeback, &nr_immediate,
> false);
> --
> 1.9.0
>
> --
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>

Other than that, looks good.

Reviewed-by: John Hubbard <jhubbard@nvidia.com>

thanks,
John H.
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