On Wed 23-10-19 12:27:29, Mike Christie wrote:

On 10/23/2019 02:11 AM, Michal Hocko wrote:

quoted

On Wed 23-10-19 07:43:44, Dave Chinner wrote:

quoted

On Tue, Oct 22, 2019 at 06:33:10PM +0200, Michal Hocko wrote:

Thanks for more clarifiation regarding PF_LESS_THROTTLE.

[...]

quoted

quoted

PF_IO_FLUSHER would mean that the user
context is a part of the IO path and therefore there are certain reclaim
recursion restrictions.

If PF_IO_FLUSHER just maps to PF_LESS_THROTTLE|PF_MEMALLOC_NOIO,
then I'm not sure we need a new definition. Maybe that's the ptrace
flag name, but in the kernel we don't need a PF_IO_FLUSHER process
flag...

Yes, the internal implementation would do something like that. I was
more interested in the user space visible API at this stage. Something
generic enough because exporting MEMALLOC flags is just a bad idea IMHO
(especially PF_MEMALLOC).

Do you mean we would do something like:

prctl()
....
case PF_SET_IO_FLUSHER:
        current->flags |= PF_MEMALLOC_NOIO;
....

yes, along with PF_LESS_THROTTLE.

-- 
Michal Hocko
SUSE Labs