On Wed, Sep 29, 2021 at 05:49:36PM -0600, Logan Gunthorpe wrote: > Some of this seems out of date. Pretty sure the pages are not refcounted > with vmf_insert_mixed() and vmf_insert_mixed() is currently the only way > to use VM_MIXEDMAP mappings. Hum. vmf_insert_mixed() boils down to insert_pfn() which always sets the special bit, so vm_normal_page() returns NULL and thus the pages are not freed during zap. So, if the pages are always special and not refcounted all the docs seem really out of date - or rather they describe the situation without the special bit, I think. Why would DAX want to do this in the first place?? This means the address space zap is much more important that just speeding up destruction, it is essential for correctness since the PTEs are not holding refcounts naturally... Sigh. Jason
