default or selected kernelversion does not have config value CONFIG_NFS_DIRECTIO.
Result is shown for kernelversion 5.19-rc1
Allow direct I/O on NFS files
configname: CONFIG_NFS_DIRECTIO
Linux Kernel Configuration
└─>File systems
└─>Network File Systems
└─>Allow direct I/O on NFS files
In linux kernel since version 2.6.20 (release Date: 2007-02-04)
This option enables applications to perform uncached I/O on files
in NFS file systems using the O_DIRECT open() flag. When O_DIRECT
is set for a file, its data is not cached in the system's page
cache. Data is moved to and from user-level application buffers
directly. Unlike local disk-based file systems, NFS O_DIRECT has
no alignment restrictions.
Unless your program is designed to use O_DIRECT properly, you are
much better off allowing the NFS client to manage data caching for
you. Misusing O_DIRECT can cause poor server performance or network
storms. This kernel build option defaults OFF to avoid exposing
system administrators unwittingly to a potentially hazardous
feature.
For more details on NFS O_DIRECT, see fs/nfs/direct.c.
If unsure, say N. This reduces the size of the NFS client, and
causes open() to return EINVAL if a file residing in NFS is
opened with the O_DIRECT flag.
in NFS file systems using the O_DIRECT open() flag. When O_DIRECT
is set for a file, its data is not cached in the system's page
cache. Data is moved to and from user-level application buffers
directly. Unlike local disk-based file systems, NFS O_DIRECT has
no alignment restrictions.
Unless your program is designed to use O_DIRECT properly, you are
much better off allowing the NFS client to manage data caching for
you. Misusing O_DIRECT can cause poor server performance or network
storms. This kernel build option defaults OFF to avoid exposing
system administrators unwittingly to a potentially hazardous
feature.
For more details on NFS O_DIRECT, see fs/nfs/direct.c.
If unsure, say N. This reduces the size of the NFS client, and
causes open() to return EINVAL if a file residing in NFS is
opened with the O_DIRECT flag.