mm/shmem, swap: bugfix and improvement of mTHP swap in

> _**请尽量提供详细的信息，如缺乏必要的定位信息，则缺陷不会被定位**_

Patch series "mm/shmem, swap: bugfix and improvement of mTHP swap in", v5.

The current mTHP swapin path have several problems.  It may potentially
hang, may cause redundant faults due to false positive swap cache lookup,
and it will involve at least 4 Xarray tree walks (get order, get order
again, confirm swap, insert folio).  And for !CONFIG_TRANSPARENT_HUGEPAGE
builds, it will performs some mTHP related checks.

This series fixes all of the mentioned issues, and the code should be more
robust and prepared for the swap table series.  Now tree walks is reduced
to twice (get order & confirm, insert folio), !CONFIG_TRANSPARENT_HUGEPAGE
build overhead is also minimized, and comes with a sanity check now.

The performance is slightly better after this series, sequential swap in
of 24G data from ZRAM, using transparent_hugepage_tmpfs=always (24 samples
each):

Before:         Avg: 10.67s,  stddev: 0.04
After patch 1:  Avg: 10.49s,  stddev: 0.04
After patch 2:  Avg: 10.42s,  stddev: 0.05
After patch 3:  Avg: 10.45s,  stddev: 0.05
After patch 4:  Avg: 10.49s,  stddev: 0.04
After patch 5:  Avg: 9.67s,   stddev: 0.03
After patch 6:  Avg: 9.67s,   stddev: 0.04
After patch 7:  Avg: 9.68s,   stddev: 0.05
After patch 8:  Avg: 9.66s,   stddev: 0.04

Several patches improve the performance by a little, which is about ~10%
faster in total.

Build kernel test showed very slightly improvement, testing with make -j48
with defconfig in a 768M memcg also using ZRAM as swap, and
transparent_hugepage_tmpfs=always (6 test runs):

Before:         avg: 3353.66s, stddev: 33.73
After patch 1:  avg: 3354.19s, stddev: 42.54
After patch 2:  avg: 3364.16s, stddev: 52.74
After patch 3:  avg: 3355.73s, stddev: 36.17
After patch 4:  avg: 3352.78s, stddev: 39.80
After patch 5:  avg: 3355.19s, stddev: 50.78
After patch 6:  avg: 3333.63s, stddev: 32.50
After patch 7:  avg: 3297.70s, stddev: 38.93
After patch 8:  avg: 3302.35s, stddev: 50.61

**二、缺陷分析结构反馈**
影响性分析说明：

缺陷严重等级:(Critical/High/Moderate/Low)

缺陷根因说明:

受影响版本排查(受影响/不受影响):
openEuler-20.03-LTS-SP4
openEuler-22.03-LTS-SP3
openEuler-22.03-LTS-SP4
openEuler-24.03-LTS
openEuler-24.03-LTS-SP1
openEuler-24.03-LTS-SP2

修复是否涉及abi变化(是/否):
openEuler-20.03-LTS-SP4
openEuler-22.03-LTS-SP3
openEuler-22.03-LTS-SP4
openEuler-24.03-LTS
openEuler-24.03-LTS-SP1
openEuler-24.03-LTS-SP2

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GVPopenEuler/kernel

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