Re: [PATCH 30/39] mm/vma: introduce vma[_flags]_is_persistent()
From: sashiko-bot@kernel.org
Date: 2026-09-08 20:47:02
Also in:
bpf, dri-devel, kvm, kvmarm, linux-perf-users, linux-s390, linux-scsi, selinux
Introduce vma[_flags]_is_persistent() for the purposes of identifying mappings that are persistent in the sense that bytes to the mapping stay there, and bytes read from the mapping are the same unless changed by actions taken by userland. Kernel-owned mappings do not fall into this category, as their owner may change the contents without the user having initiated it, and nor of course does memory-mapped I/O. We exclude fixed mappings as these are singled out as being unmergeable and so cannot be guaranteed to persist user data. hugetlb mappings are fixed mappings, but their contents are entirely the user's, so they are explicitly carved out as persistent, as the MADV_DODUMP check already does. It excludes droppable mappings, which by their nature are ephemeral. Use this functionality to update the madvise MADV_DODUMP check to test for persistence rather than open-coding this. 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 only kernel-owned mappings may set VMA_IO_BIT, so we implicitly include these. No functional change intended. Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Sashiko has reviewed this patch and found no issues. It looks great! -- Sashiko AI review · https://sashiko.dev/#/patchset/20260908-b4-mmap-prepare-vma-flag-sanify-v1-0-dacf19cce22b@kernel.org?part=30