Re: [PATCH v3 5/6] mm/gup: migrate pinned pages out of movable zone

[Pavel Tatashin]

> I guess revert what we did (unpin) and return an error. The interesting question is what can make migration/isolation fail

OK. I will make the necessary changes. Let's handle errors properly.
Whatever the cause for the error, we will know it when it happens, and
when error is returned. I think I will add a 10-time retry instead of
the infinite retry that we currently have. The 10-times retry we
currently have during the hot-remove path.

>
> a) out of memory: smells like a zone setup issue. Failures are acceptable I guess.
>
> b) short term pinnings: process dying - not relevant I guess. Other cases? (Fork?)
>
> c) ?
>
> Once we clarified that, we actually know how likely it will be to return an error (and making vfio pinnings fail etc).