mm: fix bad rss-counter if remap_file_pages raced migration
Fix some "Bad rss-counter state" reports on exit, arising from the interaction between page migration and remap_file_pages(): zap_pte() must count a migration entry when zapping it. And yes, it is possible (though very unusual) to find an anon page or swap entry in a VM_SHARED nonlinear mapping: coming from that horrid get_user_pages(write, force) case which COWs even in a shared mapping. Signed-off-by: Hugh Dickins <hughd@google.com> Tested-by: Sasha Levin sasha.levin@oracle.com> Tested-by: Dave Jones davej@redhat.com> Cc: Cyrill Gorcunov <gorcunov@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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