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Date: Fri, 4 Mar 2022 17:34:09 +0800
From: Miaohe Lin <linmiaohe@...wei.com>
To: <akpm@...ux-foundation.org>
CC: <mike.kravetz@...cle.com>, <shy828301@...il.com>,
<willy@...radead.org>, <ying.huang@...el.com>, <ziy@...dia.com>,
<minchan@...nel.org>, <apopple@...dia.com>,
<ave.hansen@...ux.intel.com>, <o451686892@...il.com>,
<almasrymina@...gle.com>, <jhubbard@...dia.com>,
<rcampbell@...dia.com>, <peterx@...hat.com>,
<naoya.horiguchi@....com>, <mhocko@...e.com>, <riel@...hat.com>,
<linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
<linmiaohe@...wei.com>
Subject: [PATCH 16/16] mm/migration: fix potential pte_unmap on an not mapped pte
__migration_entry_wait and migration_entry_wait_on_locked assume pte is
always mapped from caller. But this is not the case when it's called from
migration_entry_wait_huge and follow_huge_pmd. And a parameter unmap to
indicate whether pte needs to be unmapped to fix this issue.
Fixes: 30dad30922cc ("mm: migration: add migrate_entry_wait_huge()")
Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
include/linux/migrate.h | 2 +-
include/linux/swapops.h | 4 ++--
mm/filemap.c | 10 +++++-----
mm/hugetlb.c | 2 +-
mm/migrate.c | 14 ++++++++------
5 files changed, 17 insertions(+), 15 deletions(-)
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 66a34eae8cb6..3ef4ff699bef 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -41,7 +41,7 @@ extern int migrate_huge_page_move_mapping(struct address_space *mapping,
extern int migrate_page_move_mapping(struct address_space *mapping,
struct page *newpage, struct page *page, int extra_count);
void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep,
- spinlock_t *ptl);
+ spinlock_t *ptl, bool unmap);
void folio_migrate_flags(struct folio *newfolio, struct folio *folio);
void folio_migrate_copy(struct folio *newfolio, struct folio *folio);
int folio_migrate_mapping(struct address_space *mapping,
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index d356ab4047f7..d66556875d7d 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -213,7 +213,7 @@ static inline swp_entry_t make_writable_migration_entry(pgoff_t offset)
}
extern void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
- spinlock_t *ptl);
+ spinlock_t *ptl, bool unmap);
extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
unsigned long address);
extern void migration_entry_wait_huge(struct vm_area_struct *vma,
@@ -235,7 +235,7 @@ static inline int is_migration_entry(swp_entry_t swp)
}
static inline void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
- spinlock_t *ptl) { }
+ spinlock_t *ptl, bool unmap) { }
static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
unsigned long address) { }
static inline void migration_entry_wait_huge(struct vm_area_struct *vma,
diff --git a/mm/filemap.c b/mm/filemap.c
index 8f7e6088ee2a..18c353d52aae 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1389,6 +1389,7 @@ static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
* @ptep: mapped pte pointer. Will return with the ptep unmapped. Only required
* for pte entries, pass NULL for pmd entries.
* @ptl: already locked ptl. This function will drop the lock.
+ * @unmap: indicating whether ptep need to be unmapped.
*
* Wait for a migration entry referencing the given page to be removed. This is
* equivalent to put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE) except
@@ -1402,7 +1403,7 @@ static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
* there.
*/
void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep,
- spinlock_t *ptl)
+ spinlock_t *ptl, bool unmap)
{
struct wait_page_queue wait_page;
wait_queue_entry_t *wait = &wait_page.wait;
@@ -1439,10 +1440,9 @@ void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep,
* a valid reference to the page, and it must take the ptl to remove the
* migration entry. So the page is valid until the ptl is dropped.
*/
- if (ptep)
- pte_unmap_unlock(ptep, ptl);
- else
- spin_unlock(ptl);
+ spin_unlock(ptl);
+ if (unmap && ptep)
+ pte_unmap(ptep);
for (;;) {
unsigned int flags;
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 07668781c246..8088128c25db 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6713,7 +6713,7 @@ follow_huge_pmd(struct mm_struct *mm, unsigned long address,
} else {
if (is_hugetlb_entry_migration(pte)) {
spin_unlock(ptl);
- __migration_entry_wait(mm, (pte_t *)pmd, ptl);
+ __migration_entry_wait(mm, (pte_t *)pmd, ptl, false);
goto retry;
}
/*
diff --git a/mm/migrate.c b/mm/migrate.c
index 98a968e6f465..5519261f54fe 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -281,7 +281,7 @@ void remove_migration_ptes(struct folio *src, struct folio *dst, bool locked)
* When we return from this function the fault will be retried.
*/
void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
- spinlock_t *ptl)
+ spinlock_t *ptl, bool unmap)
{
pte_t pte;
swp_entry_t entry;
@@ -295,10 +295,12 @@ void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
if (!is_migration_entry(entry))
goto out;
- migration_entry_wait_on_locked(entry, ptep, ptl);
+ migration_entry_wait_on_locked(entry, ptep, ptl, unmap);
return;
out:
- pte_unmap_unlock(ptep, ptl);
+ spin_unlock(ptl);
+ if (unmap)
+ pte_unmap(ptep);
}
void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
@@ -306,14 +308,14 @@ void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
{
spinlock_t *ptl = pte_lockptr(mm, pmd);
pte_t *ptep = pte_offset_map(pmd, address);
- __migration_entry_wait(mm, ptep, ptl);
+ __migration_entry_wait(mm, ptep, ptl, true);
}
void migration_entry_wait_huge(struct vm_area_struct *vma,
struct mm_struct *mm, pte_t *pte)
{
spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);
- __migration_entry_wait(mm, pte, ptl);
+ __migration_entry_wait(mm, pte, ptl, false);
}
#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
@@ -324,7 +326,7 @@ void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
ptl = pmd_lock(mm, pmd);
if (!is_pmd_migration_entry(*pmd))
goto unlock;
- migration_entry_wait_on_locked(pmd_to_swp_entry(*pmd), NULL, ptl);
+ migration_entry_wait_on_locked(pmd_to_swp_entry(*pmd), NULL, ptl, false);
return;
unlock:
spin_unlock(ptl);
--
2.23.0
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