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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Mon Oct 26, 2026 at 7:17 PM EDT, David Hildenbrand (Arm) wrote: > copy_huge_pud() copies device-DAX entries without taking a folio referenc= e > or updating mapcounts and the child's RSS. > > For example, MADV_GUARD_INSTALL sets VM_MAYBE_GUARD on a device-DAX VMA, > forcing copy_page_range() to traverse the whole VMA on fork. Any remainin= g > huge PUDs are then copied without accounting for the new mappings. > Unmapping them in the child decrements accounting that was never added. > > Use vm_normal_page_pud() to identify refcounted mappings. Take a folio > reference and add the child's PUD rmap and RSS accounting before installi= ng > the copied entry. Pass src and dst VMAs consistently instead of src and > dst MM. Move the TODO. > > Fixes: aed877c2b4257 ("device/dax: properly refcount device dax pages whe= n mapping") > Cc: stable@vger.kernel.org > Signed-off-by: David Hildenbrand (Arm) > --- > include/linux/huge_mm.h | 5 ++--- > mm/huge_memory.c | 27 +++++++++++++++++++-------- > mm/memory.c | 4 +--- > 3 files changed, 22 insertions(+), 14 deletions(-) > Reviewed-by: Zi Yan --=20 Best Regards, Yan, Zi