Re: [PATCH v1] mm/mempolicy: fix migrate_to_node() assuming there is at least one VMA in a MM

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On 22.11.24 07:19, Andrew Morton wrote:
On Wed, 20 Nov 2024 15:27:46 -0500 "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx> wrote:

I hate the extra check because syzbot can cause this as this should
basically never happen in real life, but it seems we have to add it.

So..

--- a/mm/mempolicy.c~mm-mempolicy-fix-migrate_to_node-assuming-there-is-at-least-one-vma-in-a-mm-fix
+++ a/mm/mempolicy.c
@@ -1080,7 +1080,7 @@ static long migrate_to_node(struct mm_st
mmap_read_lock(mm);
  	vma = find_vma(mm, 0);
-	if (!vma) {
+	if (unlikely(!vma)) {
  		mmap_read_unlock(mm);
  		return 0;
  	}
_

?

Why not, at least for documentation purposes. Because I don't think this is any fast-path we really care about, so expect the runtime effects to be mostly negligible. Thanks!

--
Cheers,

David / dhildenb





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