[PATCH v3 01/13] mm/pgtable: add rcu_read_lock() and rcu_read_unlock()s

From: Hugh Dickins
Date: Wed Jul 12 2023 - 00:31:03 EST


Before putting them to use (several commits later), add rcu_read_lock()
to pte_offset_map(), and rcu_read_unlock() to pte_unmap(). Make this a
separate commit, since it risks exposing imbalances: prior commits have
fixed all the known imbalances, but we may find some have been missed.

Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
---
include/linux/pgtable.h | 4 ++--
mm/pgtable-generic.c | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 5063b482e34f..5134edcec668 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -99,7 +99,7 @@ static inline pte_t *pte_offset_kernel(pmd_t *pmd, unsigned long address)
((pte_t *)kmap_local_page(pmd_page(*(pmd))) + pte_index((address)))
#define pte_unmap(pte) do { \
kunmap_local((pte)); \
- /* rcu_read_unlock() to be added later */ \
+ rcu_read_unlock(); \
} while (0)
#else
static inline pte_t *__pte_map(pmd_t *pmd, unsigned long address)
@@ -108,7 +108,7 @@ static inline pte_t *__pte_map(pmd_t *pmd, unsigned long address)
}
static inline void pte_unmap(pte_t *pte)
{
- /* rcu_read_unlock() to be added later */
+ rcu_read_unlock();
}
#endif

diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index 4d454953046f..400e5a045848 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -236,7 +236,7 @@ pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp)
{
pmd_t pmdval;

- /* rcu_read_lock() to be added later */
+ rcu_read_lock();
pmdval = pmdp_get_lockless(pmd);
if (pmdvalp)
*pmdvalp = pmdval;
@@ -250,7 +250,7 @@ pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp)
}
return __pte_map(&pmdval, addr);
nomap:
- /* rcu_read_unlock() to be added later */
+ rcu_read_unlock();
return NULL;
}

--
2.35.3