The patch titled
Subject: mm: page_vma_mapped_walk: map_pte() use pte_offset_map_rw_nolock()
has been added to the -mm mm-unstable branch. Its filename is
mm-page_vma_mapped_walk-map_pte-use-pte_offset_map_rw_nolock.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-page_vma_mapped_walk-map_pte-use-pte_offset_map_rw_nolock.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Subject: mm: page_vma_mapped_walk: map_pte() use pte_offset_map_rw_nolock()
Date: Thu, 26 Sep 2024 14:46:23 +0800
In the caller of map_pte(), we may modify the pvmw->pte after acquiring
the pvmw->ptl, so convert it to using pte_offset_map_rw_nolock(). At this
time, the pte_same() check is not performed after the pvmw->ptl held, so
we should get pmdval and do pmd_same() check to ensure the stability of
pvmw->pmd.
Link: https://lkml.kernel.org/r/2620a48f34c9f19864ab0169cdbf253d31a8fcaa.1727332572.git.zhengqi.arch@xxxxxxxxxxxxx
Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Reviewed-by: Muchun Song <muchun.song@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_vma_mapped.c | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)
--- a/mm/page_vma_mapped.c~mm-page_vma_mapped_walk-map_pte-use-pte_offset_map_rw_nolock
+++ a/mm/page_vma_mapped.c
@@ -13,7 +13,8 @@ static inline bool not_found(struct page
return false;
}
-static bool map_pte(struct page_vma_mapped_walk *pvmw, spinlock_t **ptlp)
+static bool map_pte(struct page_vma_mapped_walk *pvmw, pmd_t *pmdvalp,
+ spinlock_t **ptlp)
{
pte_t ptent;
@@ -25,6 +26,7 @@ static bool map_pte(struct page_vma_mapp
return !!pvmw->pte;
}
+again:
/*
* It is important to return the ptl corresponding to pte,
* in case *pvmw->pmd changes underneath us; so we need to
@@ -32,8 +34,8 @@ static bool map_pte(struct page_vma_mapp
* 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);
+ pvmw->pte = pte_offset_map_rw_nolock(pvmw->vma->vm_mm, pvmw->pmd,
+ pvmw->address, pmdvalp, ptlp);
if (!pvmw->pte)
return false;
@@ -67,8 +69,13 @@ static bool map_pte(struct page_vma_mapp
} else if (!pte_present(ptent)) {
return false;
}
+ spin_lock(*ptlp);
+ if (unlikely(!pmd_same(*pmdvalp, pmdp_get_lockless(pvmw->pmd)))) {
+ pte_unmap_unlock(pvmw->pte, *ptlp);
+ goto again;
+ }
pvmw->ptl = *ptlp;
- spin_lock(pvmw->ptl);
+
return true;
}
@@ -278,7 +285,7 @@ restart:
step_forward(pvmw, PMD_SIZE);
continue;
}
- if (!map_pte(pvmw, &ptl)) {
+ if (!map_pte(pvmw, &pmde, &ptl)) {
if (!pvmw->pte)
goto restart;
goto next_pte;
@@ -305,8 +312,13 @@ next_pte:
} while (pte_none(ptep_get(pvmw->pte)));
if (!pvmw->ptl) {
+ spin_lock(ptl);
+ if (unlikely(!pmd_same(pmde, pmdp_get_lockless(pvmw->pmd)))) {
+ pte_unmap_unlock(pvmw->pte, ptl);
+ pvmw->pte = NULL;
+ goto restart;
+ }
pvmw->ptl = ptl;
- spin_lock(pvmw->ptl);
}
goto this_pte;
} while (pvmw->address < end);
_
Patches currently in -mm which might be from zhengqi.arch@xxxxxxxxxxxxx are
mm-pgtable-introduce-pte_offset_map_rorw_nolock.patch
powerpc-assert_pte_locked-use-pte_offset_map_ro_nolock.patch
mm-filemap-filemap_fault_recheck_pte_none-use-pte_offset_map_ro_nolock.patch
mm-khugepaged-__collapse_huge_page_swapin-use-pte_offset_map_ro_nolock.patch
arm-adjust_pte-use-pte_offset_map_rw_nolock.patch
mm-handle_pte_fault-use-pte_offset_map_rw_nolock.patch
mm-khugepaged-collapse_pte_mapped_thp-use-pte_offset_map_rw_nolock.patch
mm-copy_pte_range-use-pte_offset_map_rw_nolock.patch
mm-mremap-move_ptes-use-pte_offset_map_rw_nolock.patch
mm-page_vma_mapped_walk-map_pte-use-pte_offset_map_rw_nolock.patch
mm-userfaultfd-move_pages_pte-use-pte_offset_map_rw_nolock.patch
mm-multi-gen-lru-walk_pte_range-use-pte_offset_map_rw_nolock.patch
mm-pgtable-remove-pte_offset_map_nolock.patch
