diff options
| author | David Hildenbrand (Arm) <david@kernel.org> | 2026-10-31 10:39:40 +0100 |
|---|---|---|
| committer | David Hildenbrand (Arm) <david@kernel.org> | 2026-11-02 11:21:29 +0100 |
| commit | d90bdc02e36ec08d8248ebc6cdc52e12043eb28c (patch) | |
| tree | cf0c0930da12e115340b3ad83a19daea23bc5218 /include | |
| parent | f09171b67ea06a7fe425db33e8b74a92de1426b9 (diff) | |
mm/huge_memory: properly handle refcounted PUD mappings on fork
copy_huge_pud() copies device-DAX entries without taking a folio reference
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 remaining
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 installing
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 when mapping")
Cc: stable@vger.kernel.org
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Tested-by: Muhammad Usama Anjum <usama.anjum@arm.com>
Link: https://patch.msgid.link/20261031-fixes_core-v3-11-d6437171ecc3@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/huge_mm.h | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index c745f7ad2298..fac05120ab77 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -12,9 +12,8 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma); bool huge_pmd_set_accessed(struct vm_fault *vmf); -int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm, - pud_t *dst_pud, pud_t *src_pud, unsigned long addr, - struct vm_area_struct *vma); +int copy_huge_pud(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, + pud_t *dst_pud, pud_t *src_pud, unsigned long addr); #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud); |