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Subject[PATCH RFC v7 21/64] x86/fault: fix handle_split_page_fault() to work with memfd backed pages
Date
From: Hugh Dickins <hughd@google.com>

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>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
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
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