The quilt patch titled
Subject: mm/page_vma_mapped: pte_offset_map_nolock() not pte_lockptr()
has been removed from the -mm tree. Its filename was
mm-page_vma_mapped-pte_offset_map_nolock-not-pte_lockptr.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm/page_vma_mapped: pte_offset_map_nolock() not pte_lockptr()
Date: Thu, 8 Jun 2023 18:15:43 -0700 (PDT)
map_pte() use pte_offset_map_nolock(), to make sure of the ptl belonging
to pte, even if pmd entry is then changed racily: page_vma_mapped_walk()
use that instead of getting pte_lockptr() later, or restart if map_pte()
found no page table.
Link: https://lkml.kernel.org/r/cba186e0-5ed7-e81b-6cd-dade4c33c248@xxxxxxxxxx
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: SeongJae Park <sj@xxxxxxxxxx>
Cc: Song Liu <song@xxxxxxxxxx>
Cc: Steven Price <steven.price@xxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Zack Rusin <zackr@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_vma_mapped.c | 28 ++++++++++++++++++++++------
1 file changed, 22 insertions(+), 6 deletions(-)
--- a/mm/page_vma_mapped.c~mm-page_vma_mapped-pte_offset_map_nolock-not-pte_lockptr
+++ a/mm/page_vma_mapped.c
@@ -13,16 +13,28 @@ static inline bool not_found(struct page
return false;
}
-static bool map_pte(struct page_vma_mapped_walk *pvmw)
+static bool map_pte(struct page_vma_mapped_walk *pvmw, spinlock_t **ptlp)
{
if (pvmw->flags & PVMW_SYNC) {
/* Use the stricter lookup */
pvmw->pte = pte_offset_map_lock(pvmw->vma->vm_mm, pvmw->pmd,
pvmw->address, &pvmw->ptl);
- return true;
+ *ptlp = pvmw->ptl;
+ return !!pvmw->pte;
}
- pvmw->pte = pte_offset_map(pvmw->pmd, pvmw->address);
+ /*
+ * It is important to return the ptl corresponding to pte,
+ * in case *pvmw->pmd changes underneath us; so we need to
+ * return it even when choosing not to lock, in case caller
+ * proceeds to loop over next ptes, and finds a match later.
+ * Though, in most cases, page lock already protects this.
+ */
+ pvmw->pte = pte_offset_map_nolock(pvmw->vma->vm_mm, pvmw->pmd,
+ pvmw->address, ptlp);
+ if (!pvmw->pte)
+ return false;
+
if (pvmw->flags & PVMW_MIGRATION) {
if (!is_swap_pte(*pvmw->pte))
return false;
@@ -51,7 +63,7 @@ static bool map_pte(struct page_vma_mapp
} else if (!pte_present(*pvmw->pte)) {
return false;
}
- pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd);
+ pvmw->ptl = *ptlp;
spin_lock(pvmw->ptl);
return true;
}
@@ -156,6 +168,7 @@ bool page_vma_mapped_walk(struct page_vm
struct vm_area_struct *vma = pvmw->vma;
struct mm_struct *mm = vma->vm_mm;
unsigned long end;
+ spinlock_t *ptl;
pgd_t *pgd;
p4d_t *p4d;
pud_t *pud;
@@ -257,8 +270,11 @@ restart:
step_forward(pvmw, PMD_SIZE);
continue;
}
- if (!map_pte(pvmw))
+ if (!map_pte(pvmw, &ptl)) {
+ if (!pvmw->pte)
+ goto restart;
goto next_pte;
+ }
this_pte:
if (check_pte(pvmw))
return true;
@@ -281,7 +297,7 @@ next_pte:
} while (pte_none(*pvmw->pte));
if (!pvmw->ptl) {
- pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
+ pvmw->ptl = ptl;
spin_lock(pvmw->ptl);
}
goto this_pte;
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
