On Thu 18-07-24 20:43:53, Barry Song wrote: > On Thu, Jul 18, 2024 at 8:32 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > On Thu 18-07-24 20:18:02, Barry Song wrote: > > > So the purpose is making sure the semantics - NOFAIL means no failure > > > and we don't need to check ret. If we can't really succeed, it should throw > > > a BUG to stop any potential exploits. > > > > This would require to panic consistently on failure in all allocator > > path that can bail out. E.g. page allocator on GFP_NOWAIT|GFP_NOFAIL > > req. not sure how many more. > > Right, this GFP_NOFAIL issue seems quite messy. However, at least vmalloc > will retry by itself, even if alloc_pages might have failed with > GFP_NOWAIT | GFP_NOFAIL. > > But isn't that the definition of __GFP_NOFAIL? > > * %__GFP_NOFAIL: The VM implementation _must_ retry infinitely: the caller > * cannot handle allocation failures. The allocation could block > * indefinitely but will never return with failure. Testing for > * failure is pointless." > > So I believe any code that doesn't retry and ends up returning NULL should be > fixed. Yes, those shouldn't really fail. NOWAIT|NOFAIL was something that should never happen and I really hope it doesn't. Others should really retry but it's been some time since I've checked the last time. These overflow checks were added without any acks by MM people... -- Michal Hocko SUSE Labs
