Commit 04241ffe authored by Liam R. Howlett's avatar Liam R. Howlett Committed by Andrew Morton
Browse files

mm/mmap: introduce dup_vma_anon() helper 

Create a helper for duplicating the anon vma when adjusting the vma.  This
simplifies the logic of __vma_adjust().

Link: https://lkml.kernel.org/r/20230120162650.984577-47-Liam.Howlett@oracle.com


Signed-off-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent cf51e86d

mm/mmap.c

+40 −34
Original line number Diff line number Diff line
@@ -617,6 +617,29 @@ static inline void vma_complete(struct vma_prepare *vp, 
		uprobe_mmap(vp->insert);

}



/*

 * dup_anon_vma() - Helper function to duplicate anon_vma

 * @dst: The destination VMA

 * @src: The source VMA

 *

 * Returns: 0 on success.

 */

static inline int dup_anon_vma(struct vm_area_struct *dst,

			       struct vm_area_struct *src)

{

	/*

	 * Easily overlooked: when mprotect shifts the boundary, make sure the

	 * expanding vma has anon_vma set if the shrinking vma had, to cover any

	 * anon pages imported.

	 */

	if (src->anon_vma && !dst->anon_vma) {

		dst->anon_vma = src->anon_vma;

		return anon_vma_clone(dst, src);

	}



	return 0;

}



/*

 * vma_expand - Expand an existing VMA

 *
@@ -642,15 +665,12 @@ int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma, 
	struct vma_prepare vp;



	if (next && (vma != next) && (end == next->vm_end)) {

		remove_next = true;

		if (next->anon_vma && !vma->anon_vma) {

			int error;

		int ret;



			vma->anon_vma = next->anon_vma;

			error = anon_vma_clone(vma, next);

			if (error)

				return error;

		}

		remove_next = true;

		ret = dup_anon_vma(vma, next);

		if (ret)

			return ret;

	}



	init_multi_vma_prep(&vp, vma, NULL, remove_next ? next : NULL, NULL);
@@ -739,10 +759,11 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma, 
	struct file *file = vma->vm_file;

	bool vma_changed = false;

	long adjust_next = 0;

	struct vm_area_struct *exporter = NULL, *importer = NULL;

	struct vma_prepare vma_prep;



	if (next) {

		int error = 0;



		if (end >= next->vm_end) {

			/*

			 * vma expands, overlapping all the next, and
@@ -777,15 +798,14 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma, 
					   end != remove2->vm_end);

			}



			exporter = next;

			importer = vma;



			/*

			 * If next doesn't have anon_vma, import from vma after

			 * next, if the vma overlaps with it.

			 */

			if (remove2 != NULL && !next->anon_vma)

				exporter = remove2;

			if (remove != NULL && !next->anon_vma)

				error = dup_anon_vma(vma, remove2);

			else

				error = dup_anon_vma(vma, remove);



		} else if (end > next->vm_start) {

			/*
@@ -793,9 +813,8 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma, 
			 * mprotect case 5 shifting the boundary up.

			 */

			adjust_next = (end - next->vm_start);

			exporter = next;

			importer = vma;

			VM_WARN_ON(expand != importer);

			VM_WARN_ON(expand != vma);

			error = dup_anon_vma(vma, next);

		} else if (end < vma->vm_end) {

			/*

			 * vma shrinks, and !insert tells it's not
@@ -803,25 +822,12 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma, 
			 * mprotect case 4 shifting the boundary down.

			 */

			adjust_next = -(vma->vm_end - end);

			exporter = vma;

			importer = next;

			VM_WARN_ON(expand != importer);

			VM_WARN_ON(expand != next);

			error = dup_anon_vma(next, vma);

		}



		/*

		 * Easily overlooked: when mprotect shifts the boundary,

		 * make sure the expanding vma has anon_vma set if the

		 * shrinking vma had, to cover any anon pages imported.

		 */

		if (exporter && exporter->anon_vma && !importer->anon_vma) {

			int error;



			importer->anon_vma = exporter->anon_vma;

			error = anon_vma_clone(importer, exporter);

		if (error)

			return error;

	}

	}



	if (vma_iter_prealloc(vmi))

		return -ENOMEM;