> Introduce vma[_flags]_is_mm_backed() for the purposes of identifying > mappings which are mm-managed and whose contents were placed there by core > mm's own fault path - rather than a custom ->fault handler - and which core > mm has not reserved the right to discard. > > Mappings not managed by core mm do not fall into this category, as they are > populated by their owner, and nor of course does memory-mapped I/O. > > We exclude fixed mappings as these have a layout core mm cannot assume > ordinary fault semantics over. > > hugetlb mappings are fixed mappings, but core mm owns them entirely, so > they are explicitly carved out as mm-backed, as the MADV_DODUMP check > already does. > > Droppable mappings are excluded as core mm has promised it may discard them > at any time. > > Use this functionality to update the madvise MADV_DODUMP check to test for > this rather than open-coding it. > > This replaces the VM_SPECIAL check which means it no longer checks for > VMA_IO_BIT, however this is safe as we have established the invariant that > mm-managed mappings may not set VMA_IO_BIT, so we implicitly include > these. > > No functional change intended. > > Acked-by: Zi Yan <[email protected]> > Signed-off-by: Lorenzo Stoakes (ARM) <[email protected]>
Sashiko has reviewed this patch and found no issues. It looks great! -- Sashiko AI review ยท https://sashiko.dev/#/patchset/20261003-b4-mmap-prepare-vma-flag-sanify-v4-0-a1f052500...@kernel.org?part=30
