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mm, swap: make CONFIG_THP_SWAP depend on CONFIG_SWAP 

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.

Link: http://lkml.kernel.org/r/20180713021228.439-1-ying.huang@intel.com
Fixes: 38d8b4e6bd ("mm, THP, swap: delay splitting THP during swap out")
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shaohua Li <shli@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Huang Ying 2018-08-17 15:49:41 -07:00 committed by Linus Torvalds
parent 2a3cb8baef
commit 14fef28414
1 changed files with 3 additions and 2 deletions
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mm/Kconfig
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@ -419,10 +419,11 @@ config ARCH_WANTS_THP_SWAP
config THP_SWAP config THP_SWAP
def_bool y def_bool y
depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP
help help
Swap transparent huge pages in one piece, without splitting. 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. For selection by architectures with reasonable THP sizes.