UPSTREAM: mm: swap: skip slot cache on freeing for mTHP

Currently when we are freeing mTHP folios from swap cache, we free then
one by one and put each entry into swap slot cache.  Slot cache is
designed to reduce the overhead by batching the freeing, but mTHP swap
entries are already continuous so they can be batch freed without it
already, it saves litle overhead, or even increase overhead for larger
mTHP.

What's more, mTHP entries could stay in swap cache for a while.
Contiguous swap entry is an rather rare resource so releasing them
directly can help improve mTHP allocation success rate when under
pressure.

Link: https://lkml.kernel.org/r/20240730-swap-allocator-v5-5-cb9c148b9297@kernel.org


Change-Id: Id7b2c1ccb820f23c417757a70412c16b55b10a9d
Signed-off-by: Kairui Song <kasong@tencent.com>
Reported-by: Barry Song <21cnbao@gmail.com>
Acked-by: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 650975d2)
Bug: 313807618
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>