The quilt patch titled
Subject: mm/pagewalk: walk_pte_range() allow for pte_offset_map()
has been removed from the -mm tree. Its filename was
mm-pagewalk-walk_pte_range-allow-for-pte_offset_map.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/pagewalk: walk_pte_range() allow for pte_offset_map()
Date: Thu, 8 Jun 2023 18:18:49 -0700 (PDT)
walk_pte_range() has a no_vma option to serve walk_page_range_novma(). I
don't know of any problem, but it looks safer to check for init_mm, and
use pte_offset_kernel() rather than pte_offset_map() in that case:
pte_offset_map()'s pmdval validation is intended for userspace.
Allow for its pte_offset_map() or pte_offset_map_lock() to fail, and retry
with ACTION_AGAIN if so. Add a second check for ACTION_AGAIN in
walk_pmd_range(), to catch it after return from walk_pte_range().
Remove the pmd_trans_unstable() check after split_huge_pmd() in
walk_pmd_range(): walk_pte_range() now handles those cases safely (and
they must fail powerpc's is_hugepd() check).
Link: https://lkml.kernel.org/r/3eba6f0-2b-fb66-6bb6-2ee8533e221@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/pagewalk.c | 33 +++++++++++++++++++++++----------
1 file changed, 23 insertions(+), 10 deletions(-)
--- a/mm/pagewalk.c~mm-pagewalk-walk_pte_range-allow-for-pte_offset_map
+++ a/mm/pagewalk.c
@@ -46,15 +46,27 @@ static int walk_pte_range(pmd_t *pmd, un
spinlock_t *ptl;
if (walk->no_vma) {
- pte = pte_offset_map(pmd, addr);
- err = walk_pte_range_inner(pte, addr, end, walk);
- pte_unmap(pte);
+ /*
+ * pte_offset_map() might apply user-specific validation.
+ */
+ if (walk->mm == &init_mm)
+ pte = pte_offset_kernel(pmd, addr);
+ else
+ pte = pte_offset_map(pmd, addr);
+ if (pte) {
+ err = walk_pte_range_inner(pte, addr, end, walk);
+ if (walk->mm != &init_mm)
+ pte_unmap(pte);
+ }
} else {
pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
- err = walk_pte_range_inner(pte, addr, end, walk);
- pte_unmap_unlock(pte, ptl);
+ if (pte) {
+ err = walk_pte_range_inner(pte, addr, end, walk);
+ pte_unmap_unlock(pte, ptl);
+ }
}
-
+ if (!pte)
+ walk->action = ACTION_AGAIN;
return err;
}
@@ -141,11 +153,8 @@ again:
!(ops->pte_entry))
continue;
- if (walk->vma) {
+ if (walk->vma)
split_huge_pmd(walk->vma, pmd, addr);
- if (pmd_trans_unstable(pmd))
- goto again;
- }
if (is_hugepd(__hugepd(pmd_val(*pmd))))
err = walk_hugepd_range((hugepd_t *)pmd, addr, next, walk, PMD_SHIFT);
@@ -153,6 +162,10 @@ again:
err = walk_pte_range(pmd, addr, next, walk);
if (err)
break;
+
+ if (walk->action == ACTION_AGAIN)
+ goto again;
+
} while (pmd++, addr = next, addr != end);
return err;
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
