BugId 4629536

Problem Summary: Using the forcedirectio mount option and the mmap(2) function concurrently might cause data corruption and system hangs or panics.

Workaround: Observe the following restrictions.

• Do not remount a file system with the directio mount option added at remount time.

• Do not set the directio mount option on a single file by using the directio ioctl.

If there is a need to use directio, mount the whole file system with directio options.