On Mon, Feb 20, 2023 at 11:57:59AM -0800, Hugh Dickins wrote:

On Mon, 20 Feb 2023, Michael Roth wrote:

quoted

From: Hugh Dickins <hughd@google.com>

No.

quoted

When the address is backed by a memfd, the code to split the page does
nothing more than remove the PMD from the page tables. So immediately
install a PTE to ensure that any other pages in that 2MB region are
brought back as in 4K pages.

Signed-off-by: Hugh Dickins <hughd@google.com>

No.  Suggested-by would be okay.

quoted

Cc: Hugh Dickins <hughd@google.com>

Thanks.  I'm really sorry to be such a jobsworth,
and have nothing more constructive to say than I did before in
https://lore.kernel.org/linux-mm/7f2228c4-1586-2934-7b92-1a9d23b6046@google.com/ (local)
(please re-read), but adding a Signed-off-by where none was given is wrong;
and I'm not ever going to comprehend enough of the context to give it.

Hi Hugh,

Sorry for the mix-up, I'd intended to remove this patch before submitting. I'll
make sure to remove it from future postings.

Best of luck for the series,

Thank you!

-Mike

Hugh

quoted

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Michael Roth <redacted>
---
 mm/memory.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/memory.c b/mm/memory.c
index e68da7e403c6..33c9020ba1f8 100644
--- a/mm/memory.c
+++ b/mm/memory.c

@@ -4999,6 +4999,11 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
 static int handle_split_page_fault(struct vm_fault *vmf)
 {
 	__split_huge_pmd(vmf->vma, vmf->pmd, vmf->address, false, NULL);
+	/*
+	 * Install a PTE immediately to ensure that any other pages in
+	 * this 2MB region are brought back in as 4K pages.
+	 */
+	__pte_alloc(vmf->vma->vm_mm, vmf->pmd);
 	return 0;
 }
 

-- 
2.25.1