On Thu 02-04-20 16:10:29, Huang, Ying wrote: > Michal Hocko <mhocko@xxxxxxxxxx> writes: > > > On Thu 02-04-20 15:03:23, Huang, Ying wrote: [...] > >> > Could you explain why do we need this WARN_ON? I haven't really checked > >> > the swap support for THP but cannot we have normal swap pmd entries? > >> > >> I have some patches to add the swap pmd entry support, but they haven't > >> been merged yet. > >> > >> Similar checks are for all THP migration code paths, so I follow the > >> same style. > > > > I haven't checked other migration code paths but what is the reason to > > add the warning here? Even if this shouldn't happen, smaps is perfectly > > fine to ignore that situation, no? > > Yes. smaps itself is perfectly fine to ignore it. I think this is used > to find bugs in other code paths such as THP migration related. Please do not add new warnings without a good an strong reasons. As a matter of fact there are people running with panic_on_warn and each warning is fatal for them. Please also note that this is a user trigable path and that requires even more care. -- Michal Hocko SUSE Labs
