On Sat, Jun 17, 2017 at 01:59:47PM -0600, Jens Axboe wrote:

Add four flags for the pwritev2(2) system call, allowing an application
to give the kernel a hint about what on-media life times can be
expected from a given write.

The intent is for these values to be relative to each other, no
absolute meaning should be attached to these flag names.

Set aside 3 bits in the iocb flags structure to carry this information
over from the pwritev2 RWF_WRITE_LIFE_* flags.

What is the strong use case for the per-I/O flags?  I'd much rather
stick to fcntl only for now if we can.