On 06/19/2017 08:56 AM, Jens Axboe wrote: > On 06/19/2017 12:27 AM, Christoph Hellwig wrote: >> 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. > > Fine, I guess I should just have dusted off the 2 year old patchset, > as that was _exactly_ what that did. Actually, one good use case is O_DIRECT on a block device. Since I'm not a huge fan of having per-call hints that is only useful for a single case, how about we add the hints to the struct file as well? For buffered IO, just grab it from the inode. If we have a file available, then that overrides the per-inode setting. -- Jens Axboe
