-config NFS_DIRECTIO
- bool "Allow direct I/O on NFS files"
- depends on NFS_FS
- help
- 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.
-