| Date | Fri, 27 Jan 2023 11:40:53 -0800 | Subject | [PATCH v2 16/33] mm/mmap: write-lock VMA before shrinking or expanding it | From | Suren Baghdasaryan <> |
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vma_expand and vma_shrink change VMA boundaries. Expansion might also result in freeing of an adjacent VMA. Write-lock affected VMAs to prevent concurrent page faults.
Signed-off-by: Suren Baghdasaryan <surenb@google.com> --- mm/mmap.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/mm/mmap.c b/mm/mmap.c index 6fff76334177..60038c24d836 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -674,6 +674,9 @@ int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma, ret = dup_anon_vma(vma, next); if (ret) return ret; + + /* Lock the VMA before removing it */ + vma_start_write(next); } init_multi_vma_prep(&vp, vma, NULL, remove_next ? next : NULL, NULL); @@ -686,6 +689,7 @@ int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma, if (vma_iter_prealloc(vmi)) goto nomem; + vma_start_write(vma); vma_adjust_trans_huge(vma, start, end, 0); /* VMA iterator points to previous, so set to start if necessary */ if (vma_iter_addr(vmi) != start) @@ -725,6 +729,7 @@ int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma, if (vma_iter_prealloc(vmi)) return -ENOMEM; + vma_start_write(vma); init_vma_prep(&vp, vma); vma_adjust_trans_huge(vma, start, end, 0); vma_prepare(&vp); -- 2.39.1
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