Re: [PATCH 6.12.y] mm/vma: reset VMA iterator on commit_merge() OOM failure

[Sasha Levin <sashal@kernel.org>]

[ Sasha's backport helper bot ]

Hi,

Summary of potential issues:
⚠️ Found matching upstream commit but patch is missing proper reference to it

Found matching upstream commit: 0cf4b1687a187ba9247c71721d8b064634eda1f7

Status in newer kernel trees:
6.15.y | Present (different SHA1: b07a09cf2a1c)

Note: The patch differs from the upstream commit:
---
1:  0cf4b1687a187 ! 1:  2e6afa970267d mm/vma: reset VMA iterator on commit_merge() OOM failure
    @@ Commit message
         Cc: Jann Horn <jannh@google.com>
         Cc: <stable@vger.kernel.org>
         Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    +    (cherry picked from commit 0cf4b1687a187ba9247c71721d8b064634eda1f7)
    +    Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
     
      ## mm/vma.c ##
    -@@ mm/vma.c: static __must_check struct vm_area_struct *vma_merge_existing_range(
    - 		err = dup_anon_vma(next, middle, &anon_dup);
    +@@ mm/vma.c: static struct vm_area_struct *vma_merge_existing_range(struct vma_merge_struct *
    + 		err = dup_anon_vma(next, vma, &anon_dup);
      	}
      
     -	if (err)
    -+	if (err || commit_merge(vmg))
    - 		goto abort;
    - 
    --	err = commit_merge(vmg);
    --	if (err) {
    --		VM_WARN_ON(err != -ENOMEM);
    +-		goto abort;
     -
    + 	/*
    + 	 * In nearly all cases, we expand vmg->vma. There is one exception -
    + 	 * merge_right where we partially span the VMA. In this case we shrink
    +@@ mm/vma.c: static struct vm_area_struct *vma_merge_existing_range(struct vma_merge_struct *
    + 	 */
    + 	expanded = !merge_right || merge_will_delete_vma;
    + 
    +-	if (commit_merge(vmg, adjust,
    +-			 merge_will_delete_vma ? vma : NULL,
    +-			 merge_will_delete_next ? next : NULL,
    +-			 adj_start, expanded)) {
     -		if (anon_dup)
     -			unlink_anon_vmas(anon_dup);
     -
    @@ mm/vma.c: static __must_check struct vm_area_struct *vma_merge_existing_range(
     -			vmg->state = VMA_MERGE_ERROR_NOMEM;
     -		return NULL;
     -	}
    --
    - 	khugepaged_enter_vma(vmg->target, vmg->flags);
    - 	vmg->state = VMA_MERGE_SUCCESS;
    - 	return vmg->target;
    -@@ mm/vma.c: static __must_check struct vm_area_struct *vma_merge_existing_range(
    ++	if (err || commit_merge(vmg, adjust,
    ++			merge_will_delete_vma ? vma : NULL,
    ++			merge_will_delete_next ? next : NULL,
    ++			adj_start, expanded))
    ++		goto abort;
    + 
    + 	res = merge_left ? prev : next;
    + 	khugepaged_enter_vma(res, vmg->flags);
    +@@ mm/vma.c: static struct vm_area_struct *vma_merge_existing_range(struct vma_merge_struct *
      	vma_iter_set(vmg->vmi, start);
      	vma_iter_load(vmg->vmi);
      
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.12.y       |  Success    |  Success   |