diff mbox series

[v2,07/10] mm/hugetlb: Make follow_hugetlb_page() safe to pmd unshare

Message ID 20221207203034.650899-8-peterx@redhat.com
State New
Headers
Series [v2,01/10] mm/hugetlb: Let vma_offset_start() to return start |

Commit Message

Peter Xu Dec. 7, 2022, 8:30 p.m. UTC 
  Since follow_hugetlb_page() walks the pgtable, it needs the vma lock
to make sure the pgtable page will not be freed concurrently.

Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 mm/hugetlb.c | 7 +++++++
 1 file changed, 7 insertions(+)

Comments

John Hubbard Dec. 7, 2022, 11:25 p.m. UTC | #1 
On 12/7/22 12:30, Peter Xu wrote:
> Since follow_hugetlb_page() walks the pgtable, it needs the vma lock
> to make sure the pgtable page will not be freed concurrently.
> 
> Acked-by: David Hildenbrand <david@redhat.com>
> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>   mm/hugetlb.c | 7 +++++++
>   1 file changed, 7 insertions(+)

Reviewed-by: John Hubbard <jhubbard@nvidia.com>


thanks,
diff mbox series

Patch

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3fbbd599d015..f42399522805 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6284,6 +6284,7 @@  long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 			break;
 		}
 
+		hugetlb_vma_lock_read(vma);
 		/*
 		 * Some archs (sparc64, sh*) have multiple pte_ts to
 		 * each hugepage.  We have to make sure we get the
@@ -6308,6 +6309,7 @@  long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 		    !hugetlbfs_pagecache_present(h, vma, vaddr)) {
 			if (pte)
 				spin_unlock(ptl);
+			hugetlb_vma_unlock_read(vma);
 			remainder = 0;
 			break;
 		}
@@ -6329,6 +6331,8 @@  long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 
 			if (pte)
 				spin_unlock(ptl);
+			hugetlb_vma_unlock_read(vma);
+
 			if (flags & FOLL_WRITE)
 				fault_flags |= FAULT_FLAG_WRITE;
 			else if (unshare)
@@ -6388,6 +6392,7 @@  long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 			remainder -= pages_per_huge_page(h);
 			i += pages_per_huge_page(h);
 			spin_unlock(ptl);
+			hugetlb_vma_unlock_read(vma);
 			continue;
 		}
 
@@ -6415,6 +6420,7 @@  long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 			if (WARN_ON_ONCE(!try_grab_folio(pages[i], refs,
 							 flags))) {
 				spin_unlock(ptl);
+				hugetlb_vma_unlock_read(vma);
 				remainder = 0;
 				err = -ENOMEM;
 				break;
@@ -6426,6 +6432,7 @@  long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 		i += refs;
 
 		spin_unlock(ptl);
+		hugetlb_vma_unlock_read(vma);
 	}
 	*nr_pages = remainder;
 	/*