[merged mm-stable] mm-vma-the-pgoff-is-correct-if-can_merge_right.patch removed from -mm tree

[merged mm-stable] mm-vma-the-pgoff-is-correct-if-can_merge_right.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/vma: the pgoff is correct if can_merge_right
has been removed from the -mm tree.  Its filename was
     mm-vma-the-pgoff-is-correct-if-can_merge_right.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Wei Yang <richard.weiyang@gmail.com>
Subject: mm/vma: the pgoff is correct if can_merge_right
Date: Thu, 24 Oct 2024 09:33:47 +0000

By this point can_vma_merge_right() must have returned true, which implies
can_vma_merge_before() also returned true, which already asserts that the
pgoff is as expected for a merge with the following VMA, thus this
assignment is redundant.

Below is a more detail explanation.

Current definition of can_vma_merge_right() is:

	static bool can_vma_merge_right(struct vma_merge_struct *vmg,
					bool can_merge_left)
	{
		if (!vmg->next || vmg->end != vmg->next->vm_start ||
		    !can_vma_merge_before(vmg))
			return false;
		...
	}

And:

	static bool can_vma_merge_before(struct vma_merge_struct *vmg)
	{
		pgoff_t pglen = PHYS_PFN(vmg->end - vmg->start);
	...
			if (vmg->next->vm_pgoff == vmg->pgoff + pglen)
				return true;
	...
	}

Which implies vmg->pgoff == vmg->next->vm_pgoff - pglen.

None of these values are changed between the check and prior assignment,
so this was an entirely redundant assignment.


[akpm@linux-foundation.org: remove now-unused local]
[lorenzo.stoakes@oracle.com: rephrase the changelog]
Link: https://lkml.kernel.org/r/20241024093347.18057-1-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Jann Horn <jannh@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vma.c |    3 ---
 1 file changed, 3 deletions(-)

--- a/mm/vma.c~mm-vma-the-pgoff-is-correct-if-can_merge_right
+++ a/mm/vma.c
@@ -962,9 +962,7 @@ struct vm_area_struct *vma_merge_new_ran
 {
 	struct vm_area_struct *prev = vmg->prev;
 	struct vm_area_struct *next = vmg->next;
-	unsigned long start = vmg->start;
 	unsigned long end = vmg->end;
-	pgoff_t pglen = PHYS_PFN(end - start);
 	bool can_merge_left, can_merge_right;
 	bool just_expand = vmg->merge_flags & VMG_FLAG_JUST_EXPAND;
 
@@ -986,7 +984,6 @@ struct vm_area_struct *vma_merge_new_ran
 	if (can_merge_right) {
 		vmg->end = next->vm_end;
 		vmg->vma = next;
-		vmg->pgoff = next->vm_pgoff - pglen;
 	}
 
 	/* If we can merge with the previous VMA, adjust vmg accordingly. */
_

Patches currently in -mm which might be from richard.weiyang@gmail.com are

mm-mlock-set-the-correct-prev-on-failure.patch
maple_tree-print-empty-for-an-empty-tree-on-mt_dump.patch
maple_tree-the-return-value-of-mas_root_expand-is-not-used.patch
maple_tree-not-necessary-to-check-index-last-again.patch
maple_tree-refine-mas_store_root-on-storing-null.patch
maple_tree-add-a-test-checking-storing-null.patch