On Fri, 21 Oct 2022 18:16:23 +0800 Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> wrote: > When THP migration, if THPs are split and all subpages are migrated successfully > , the migrate_pages() will still return the number of THP that were not migrated. > That will confuse the callers of migrate_pages(), for example, which will make > the longterm pinning failed though all pages are migrated successfully. > > Thus we should return 0 to indicate all pages are migrated in this case. > This had me puzzled for a while. I think this wording is clearer? : During THP migration, if THPs are not migrated but they are split and all : subpages are migrated successfully, migrate_pages() will still return the : number of THP pages that were not migrated. This will confuse the callers : of migrate_pages(). For example, the longterm pinning will failed though : all pages are migrated successfully. : : Thus we should return 0 to indicate that all pages are migrated in this : case. This is a fairly longstanding problem? No Fixes: we can identify? Did you consider the desirability of a -stable backport?
