On Mon, 2017-07-24 at 13:18 +0800, Huang, Ying wrote:
> From: Huang Ying <ying.huang@intel.com>
> 
> The normal swap slot reclaiming can be done when the swap count
> reaches SWAP_HAS_CACHE.  But for the swap slot which is backing a
> THP,
> all swap slots backing one THP must be reclaimed together, because
> the
> swap slot may be used again when the THP is swapped out again later.
> So the swap slots backing one THP can be reclaimed together when the
> swap count for all swap slots for the THP reached SWAP_HAS_CACHE.  In
> the patch, the functions to check whether the swap count for all swap
> slots backing one THP reached SWAP_HAS_CACHE are implemented and used
> when checking whether a swap slot can be reclaimed.
> 
> To make it easier to determine whether a swap slot is backing a THP,
> a
> new swap cluster flag named CLUSTER_FLAG_HUGE is added to mark a swap
> cluster which is backing a THP (Transparent Huge Page).  Because THP
> swap in as a whole isn't supported now.  After deleting the THP from
> the swap cache (for example, swapping out finished), the
> CLUSTER_FLAG_HUGE flag will be cleared.  So that, the normal pages
> inside THP can be swapped in individually.
> 
> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Shaohua Li <shli@kernel.org>
> Cc: Rik van Riel <riel@redhat.com>
> 
Acked-by: Rik van Riel <riel@redhat.com>

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