From: Huang Ying <ying.huang@xxxxxxxxx>
CONFIG_THP_SWAP should depend on CONFIG_SWAP, because it's
unreasonable to optimize swapping for THP (Transparent Huge Page)
without basic swapping support.
In original code, when CONFIG_SWAP=n and CONFIG_THP_SWAP=y,
split_swap_cluster() will not be built because it is in swapfile.c,
but it will be called in huge_memory.c. This doesn't trigger a build
error in practice because the call site is enclosed by
PageSwapCache(), which is defined to be constant 0 when CONFIG_SWAP=n.
But this is fragile and should be fixed.
The comments are fixed too to reflect the latest progress.
Fixes: 38d8b4e6bdc8 ("mm, THP, swap: delay splitting THP during swap out")
Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Reviewed-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Shaohua Li <shli@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Zi Yan <zi.yan@xxxxxxxxxxxxxx>
Cc: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
---
mm/Kconfig | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/mm/Kconfig b/mm/Kconfig
index b78e7cd4e9fe..97114c94239c 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -419,10 +419,11 @@ config ARCH_WANTS_THP_SWAP
config THP_SWAP
def_bool y
- depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP
+ depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP
help
Swap transparent huge pages in one piece, without splitting.
- XXX: For now this only does clustered swap space allocation.
+ XXX: For now, swap cluster backing transparent huge page
+ will be split after swapout.
For selection by architectures with reasonable THP sizes.
--
2.16.4
