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We discussed if that is really the right approach for quite a while now, but digging deeper into a bug report on arm turned out that this is actually horrible broken right now. The reason for this is that vmf_insert_mixed_prot() always tries to grab a reference to the underlaying page on architectures without ARCH_HAS_PTE_SPECIAL and as far as I can see also enabled GUP. So nuke using VM_MIXEDMAP here and use VM_PFNMAP instead. Also make sure to reject mappings without VM_SHARED. v2: reject COW mappings, merge function with only caller v3: adjust comment as suggested by Thomas Signed-off-by: Christian König <christian.koenig@amd.com> Bugs: https://gitlab.freedesktop.org/drm/amd/-/issues/1606#note_936174 Link: https://patchwork.freedesktop.org/patch/msgid/20210607135830.8574-1-christian.koenig@amd.com Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>