On 01/23/2018 12:35 AM, Matthew Wilcox wrote: > On Mon, Jan 22, 2018 at 08:28:54PM -0700, Jens Axboe wrote: >> On 1/22/18 8:18 PM, Goldwyn Rodrigues wrote: >>>> that their application was "already broken". I'd hate for a kernel >>>> upgrade to break them. >>>> >>>> I do wish we could make the change, and maybe we can. But it probably >>>> needs some safe guard proc entry to toggle the behavior, something we >>>> can drop in a few years when we're confident it won't break real >>>> applications. >>> >>> Assuming we call it /proc/sys/fs/dio_short_writes(better names/paths?), >>> should it be enabled or disabled by default? >> >> I'd enable it by default, if not, you are never going to be able to >> remove it because you'll have no confidence that anyone actually flipped >> the switch and ran with it enabled. The point of having it there and on >> by default would be that if something does break, people have the option >> of turning it off and restoring the previous behavior, without having to >> change the kernel. > > I think it's an opt-in prctl that's something like PRCTL_SHORT_WRITES_ALLOWED. > I cannot decide where to stick this bit in the task_struct. current->flags/PF_* does not seem right. Don't want to start a new fs_flags field. Suggestions? -- Goldwyn
