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David Hildenbrand (Arm)
88692f0c33
Pages that BPF arena code maps are allocated through bpf_map_alloc_pages(), which does not allocate folios but pages. In the future, pages will not have a mapcount, only folios will. Converting the code to use folios and rely on folio_mapped() sounds like the wrong approach. Should BPF arena code allocate folios and use folio_mapped() here? But likely we would not want to use folios here longterm, as we don't really need folio information. Hard to tell. But in the meantime, we can simply use the page refcount instead, as a heuristic whether the page might be mapped to user space and we would want to try zapping it, so we can get rid of page_mapped(). Page allocation will give us a page with a refcount of 1. Any user space mapping adds a page reference. While there can be references from other subsystems (e.g., GUP), in the common case for this test here relying on the page count is good enough. Link: https://lore.kernel.org/[email protected] Signed-off-by: David Hildenbrand (Arm) <[email protected]> Reviewed-by: Matthew Wilcox (Oracle) <[email protected]> Cc: Alexei Starovoitov <[email protected]> Cc: Andrii Nakryiko <[email protected]> Cc: Eduard Zingerman <[email protected]> Cc: Harry Yoo <[email protected]> Cc: Jann Horn <[email protected]> Cc: Jiri Olsa <[email protected]> Cc: John Paul Adrian Glaubitz <[email protected]> Cc: Kumar Kartikeya Dwivedi <[email protected]> Cc: Liam R. Howlett <[email protected]> Cc: Lorenzo Stoakes <[email protected]> Cc: Martin KaFai Lau <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Mike Rapoport <[email protected]> Cc: Rich Felker <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Song Liu <[email protected]> Cc: Suren Baghdasaryan <[email protected]> Cc: Vlastimil Babka <[email protected]> Cc: Yonghong Song <[email protected]> Cc: Yoshinori Sato <[email protected]> Signed-off-by: Andrew Morton <[email protected]>