On Mon 23-04-18 20:25:15, Mikulas Patocka wrote: > > > On Mon, 23 Apr 2018, Michal Hocko wrote: > > > On Mon 23-04-18 10:06:08, Mikulas Patocka wrote: > > > > > > > He didn't want to fix vmalloc(GFP_NOIO) > > > > > > > > I don't remember that conversation, so I don't know whether I agree with > > > > his reasoning or not. But we are supposed to be moving away from GFP_NOIO > > > > towards marking regions with memalloc_noio_save() / restore. If you do > > > > that, you won't need vmalloc(GFP_NOIO). > > > > > > He said the same thing a year ago. And there was small progress. 6 out of > > > 27 __vmalloc calls were converted to memalloc_noio_save in a year - 5 in > > > infiniband and 1 in btrfs. (the whole discussion is here > > > http://lkml.iu.edu/hypermail/linux/kernel/1706.3/04681.html ) > > > > Well this is not that easy. It requires a cooperation from maintainers. > > I can only do as much. I've posted patches in the past and actively > > bringing up this topic at LSFMM last two years... > > You're right - but you have chosen the uneasy path. Yes. > Fixing __vmalloc code > is easy and it doesn't require cooperation with maintainers. But it is a hack against the intention of the scope api. It also alows maintainers to not care about their broken code. > > > He refuses 15-line patch to fix GFP_NOIO bug because he believes that in 4 > > > years, the kernel will be refactored and GFP_NOIO will be eliminated. Why > > > does he have veto over this part of the code? I'd much rather argue with > > > people who have constructive comments about fixing bugs than with him. > > > > I didn't NACK the patch AFAIR. I've said it is not a good idea longterm. > > I would be much more willing to change my mind if you would back your > > patch by a real bug report. Hacks are acceptable when we have a real > > issue in hands. But if we want to fix potential issue then better make > > it properly. > > Developers should fix bugs in advance, not to wait until a crash hapens, > is analyzed and reported. I agree. But are those existing users broken in the first place? I have seen so many GFP_NOFS abuses that I would dare to guess that most of those vmalloc NOFS abusers can be simply turned into GFP_KERNEL. Maybe that is the reason we haven't heard any complains in years. -- Michal Hocko SUSE Labs
