Commit 00cd00a6 authored by Lorenzo Stoakes's avatar Lorenzo Stoakes Committed by Andrew Morton
Browse files

mm/mmap/vma_merge: fold curr, next assignment logic 

Use find_vma_intersection() and vma_lookup() to both simplify the logic
and to fold the end == next->vm_start condition into one block.

This groups all of the simple range checks together and establishes the
invariant that, if prev, curr or next are non-NULL then their positions
are as expected.

This has no functional impact.

Link: https://lkml.kernel.org/r/c6d960641b4ba58fa6ad3d07bf68c27d847963c8.1679516210.git.lstoakes@gmail.com


Signed-off-by: default avatarLorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: default avatarVlastimil Babka <vbabka@suse.cz>
Reviewed-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Vernon Yang <vernon2gm@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent fcfccd91

mm/mmap.c

+11 −13
Original line number Diff line number Diff line
@@ -917,15 +917,14 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, 
	if (vm_flags & VM_SPECIAL)

		return NULL;



	curr = find_vma(mm, prev ? prev->vm_end : 0);

	if (curr && curr->vm_end == end)		/* cases 6, 7, 8 */

		next = find_vma(mm, curr->vm_end);

	else

		next = curr;

	/* Does the input range span an existing VMA? (cases 5 - 8) */

	curr = find_vma_intersection(mm, prev ? prev->vm_end : 0, end);



	/* In cases 1 - 4 there's no CCCC vma */

	if (curr && end <= curr->vm_start)

		curr = NULL;

	if (!curr ||			/* cases 1 - 4 */

	    end == curr->vm_end)	/* cases 6 - 8, adjacent VMA */

		next = vma_lookup(mm, end);

	else

		next = NULL;		/* case 5 */



	/* verify some invariant that must be enforced by the caller */

	VM_WARN_ON(prev && addr <= prev->vm_start);
@@ -946,8 +945,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, 
		}

	}

	/* Can we merge the successor? */

	if (next && end == next->vm_start &&

			mpol_equal(policy, vma_policy(next)) &&

	if (next && mpol_equal(policy, vma_policy(next)) &&

	    can_vma_merge_before(next, vm_flags,

				 anon_vma, file, pgoff+pglen,

				 vm_userfaultfd_ctx, anon_name)) {