> Commit e1fb4a086495 ("dax: remove VM_MIXEDMAP for fsdax and device dax")
> prevented fsdax and device-dax from setting VM_MIXEDMAP, as DAX no longer
> relies on it to direct core mm paths.
>
> The fuse DAX implementation, added later, copied the old pattern and still
> sets it.
>
> Fuse DAX maps pages the same way fsdax does, via dax_iomap_fault() and
> ultimately vmf_insert_page_mkwrite() and vmf_insert_folio_pmd(), which
> insert ordinary refcounted pages and so do not require VM_MIXEDMAP.
>
> Setting it only serves to mark the mapping as kernel-owned, making fuse DAX
> the sole DAX implementation whose mappings are unmergeable, cannot be
> mlock()'d, eagerly copy page tables on fork and reject MADV_DOFORK and
> MADV_DODUMP.
>
> It also requires vma_is_special_huge() in mm/huge_memory.c to carve DAX out
> of its kernel-owned check explicitly.
>
> There is no reason for fuse DAX to keep on using this flag so drop it.
>
> Signed-off-by: Lorenzo Stoakes (ARM) <[email protected]>
Sashiko has reviewed this patch and found no issues. It looks great!
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Sashiko AI review ยท
https://sashiko.dev/#/patchset/20260914-b4-mmap-prepare-vma-flag-sanify-v2-0-7d9781ed5...@kernel.org?part=38
