diff mbox series

[RFC,v1,3/4] thp: fix huge page zapping for special PMDs

Message ID DB7PR02MB3979BC324920A783BD5BB721BB5A0@DB7PR02MB3979.eurprd02.prod.outlook.com (mailing list archive)
State New, archived
Headers show
Series [RFC,v1,1/4] mm/remote_mapping: mirror a process address space | expand

Commit Message

Mircea CIRJALIU - MELIU Dec. 11, 2019, 9:29 a.m. UTC 
When calling zap_vma_ptes() on VM_PFNMAP VMAs involving huge mappings,
pmd_page() will return an invalid page, causing trouble. Use instead
vm_normal_page_pmd() and test for returned page like zap_pte_range().

Signed-off-by: Mircea Cirjaliu <mcirjaliu@bitdefender.com>
---
 mm/huge_memory.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Comments

Kirill A . Shutemov Dec. 11, 2019, 3:54 p.m. UTC | #1 
On Wed, Dec 11, 2019 at 09:29:20AM +0000, Mircea CIRJALIU - MELIU wrote:
> When calling zap_vma_ptes() on VM_PFNMAP VMAs involving huge mappings,

Do we have such VMAs?
Mircea CIRJALIU - MELIU Dec. 11, 2019, 5:08 p.m. UTC | #2 
> On Wed, Dec 11, 2019 at 09:29:20AM +0000, Mircea CIRJALIU - MELIU wrote:
> > When calling zap_vma_ptes() on VM_PFNMAP VMAs involving huge
> mappings,
> 
> Do we have such VMAs?

I have such VMAs in the remote mapping feature.
Any reason why these VMAs are dangerous?

> 
> --
>  Kirill A. Shutemov
> 
> ________________________
> This email was scanned by Bitdefender
diff mbox series

Patch

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 41a0fbd..92ce487 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1804,7 +1804,11 @@  int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 		int flush_needed = 1;
 
 		if (pmd_present(orig_pmd)) {
-			page = pmd_page(orig_pmd);
+			page = vm_normal_page_pmd(vma, addr, orig_pmd);
+			if (unlikely(!page)) {
+				spin_unlock(ptl);
+				return 1;
+			}
 			page_remove_rmap(page, true);
 			VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
 			VM_BUG_ON_PAGE(!PageHead(page), page);