GFS2 is slower at performing direct I/O initial writes after upgrading from RHEL 8.3 to RHEL 8.4

Issue

• A filesystem benchmark utility (e.g., IOzone) shows a roughly 57% performance reduction for initial writes via direct I/O after upgrading from a RHEL 8.3 kernel to a RHEL 8.4 kernel.
• Example IOzone output:

=======================================================================================================================
Mon 11 Jan 2021 08:40:45 AM EST

 KERNEL                     gfs2
----------                  ====
1 - 4.18.0-240.el8.x86_64
2 - 4.18.0-270.el8.x86_64

                         ALL  INIT   RE             RE   RANDOM RANDOM BACKWD  RECRE STRIDE  F      FRE     F      FRE
 TEST          KERNEL    IOS  WRITE  WRITE   READ   READ   READ  WRITE   READ  WRITE   READ  WRITE  WRITE   READ   READ
-----------------------------------------------------------------------------------------------------------------------
InCache          1      2730   1100   1729   5047   4290   4230   1205   4316   3398   4391   1033   1597   4968   4233 
InCache          2      2727   1102   1714   5109   4177   4291   1209   4365   3401   4433   1019   1588   5020   4128 
                           .      .      .      .      .      .      .      .      .      .      .      .      .      . 

DirectIO         1       217    178    202    267    271    194    198    234    219    207 
DirectIO         2       195     76    200    254    266    193    197    234    219    205 
                       -10.0  -57.3      .      .      .      .      .      .      .      . 

OutOfCache       1       462    308    300    802    758    143    135    493   5539    255    310    303    810    766 
OutOfCache       2       463    308    301    813    750    145    136    500   5528    260    305    300    811    755 
                           .      .      .      .      .      .      .      .      .      .      .      .      .      . 

InCacheMMAP      1      2817    622   1083   7319   7573   7030    780   7430    992   7378 
InCacheMMAP      2      2720    612   1035   7072   7425   6881    750   6957    947   7189 
                           .      .      .      .      .      .      .   -6.4      .      . 

InCacheFsync     1      1395    267    287   5076   4304   4244    202   4355   1757   4411    258    283   4996   4248 
InCacheFsync     2      1385    265    284   5093   4178   4271    200   4356   1745   4425    255    282   5014   4125 
                           .      .      .      .      .      .      .      .      .      .      .      .      .      .