On 3/3/26 05:15, Matthew Wilcox wrote:

> On Tue, Mar 03, 2026 at 10:52:51AM +0800, liying3@sungrowpower.com wrote:

>> Hi Andrew,

>> I found that a fix is required for this submission in branch 6.6.

>> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a13b2b9b0b0b04612c7d81e3b3dfb485c5f7abc3

> Agreed, although your email should more properly have been directed to

> David and possibly Greg. Are you going to submit a patch to fix this,

> or do you prefer that somebody else does it?

>> Regarding the difference between branches 6.6 and 6.12, in branch 6.6, mmap_read_lock() and mmap_read_unlock() are called outside the migrate_to_node() function.

>> Therefore, mmap_read_unlock(mm) should not be invoked inside migrate_to_node(); otherwise, it would result in a double unlock of the mm.

>> diff --git a/mm/mempolicy.c b/mm/mempolicy.c

>> index 54f1b78d1b2c0f..94c74c594d102a 100644

>> --- a/mm/mempolicy.c

>> +++ b/mm/mempolicy.c

>> @@ -1071,6 +1071,10 @@ static long migrate_to_node(struct mm_struct *mm, int source, int dest,

>> VM_BUG_ON(!(flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)));

>> vma = find_vma(mm, 0);

>> + if (unlikely(!vma)) {

>> + mmap_read_unlock(mm); // this line should be deleted

>> + return 0;

>> + }

Right, that unlock must go. Let me know if I should prepare a fix.

Cheers,

David