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Subject[PATCH v6 09/12] mmap locking API: add mmap_assert_locked() and mmap_assert_write_locked()
From
Add new APIs to assert that mmap_sem is held.

Using this instead of rwsem_is_locked and lockdep_assert_held[_write]
makes the assertions more tolerant of future changes to the lock type.

Signed-off-by: Michel Lespinasse <walken@google.com>
---
arch/x86/events/core.c | 2 +-
fs/userfaultfd.c | 6 +++---
include/linux/mmap_lock.h | 14 ++++++++++++++
mm/gup.c | 2 +-
mm/hmm.c | 2 +-
mm/memory.c | 2 +-
mm/mmu_notifier.c | 6 +++---
mm/pagewalk.c | 6 +++---
mm/util.c | 2 +-
9 files changed, 28 insertions(+), 14 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index a619763e96e1..66559ac4f89e 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2182,7 +2182,7 @@ static void x86_pmu_event_mapped(struct perf_event *event, struct mm_struct *mm)
* For now, this can't happen because all callers hold mmap_sem
* for write. If this changes, we'll need a different solution.
*/
- lockdep_assert_held_write(&mm->mmap_sem);
+ mmap_assert_write_locked(mm);

if (atomic_inc_return(&mm->context.perf_rdpmc_allowed) == 1)
on_each_cpu_mask(mm_cpumask(mm), refresh_pce, NULL, 1);
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 9c645eee1a59..12b492409040 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -234,7 +234,7 @@ static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
pte_t *ptep, pte;
bool ret = true;

- VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
+ mmap_assert_locked(mm);

ptep = huge_pte_offset(mm, address, vma_mmu_pagesize(vma));

@@ -286,7 +286,7 @@ static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx,
pte_t *pte;
bool ret = true;

- VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
+ mmap_assert_locked(mm);

pgd = pgd_offset(mm, address);
if (!pgd_present(*pgd))
@@ -405,7 +405,7 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
* Coredumping runs without mmap_sem so we can only check that
* the mmap_sem is held, if PF_DUMPCORE was not set.
*/
- WARN_ON_ONCE(!rwsem_is_locked(&mm->mmap_sem));
+ mmap_assert_locked(mm);

ctx = vmf->vma->vm_userfaultfd_ctx.ctx;
if (!ctx)
diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h
index acac1bf5ecd2..43ef914e6468 100644
--- a/include/linux/mmap_lock.h
+++ b/include/linux/mmap_lock.h
@@ -1,6 +1,8 @@
#ifndef _LINUX_MMAP_LOCK_H
#define _LINUX_MMAP_LOCK_H

+#include <linux/mmdebug.h>
+
#define MMAP_LOCK_INITIALIZER(name) \
.mmap_sem = __RWSEM_INITIALIZER((name).mmap_sem),

@@ -73,4 +75,16 @@ static inline void mmap_read_unlock_non_owner(struct mm_struct *mm)
up_read_non_owner(&mm->mmap_sem);
}

+static inline void mmap_assert_locked(struct mm_struct *mm)
+{
+ lockdep_assert_held(&mm->mmap_sem);
+ VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
+}
+
+static inline void mmap_assert_write_locked(struct mm_struct *mm)
+{
+ lockdep_assert_held_write(&mm->mmap_sem);
+ VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
+}
+
#endif /* _LINUX_MMAP_LOCK_H */
diff --git a/mm/gup.c b/mm/gup.c
index 631285295950..c1c0b37d0e8f 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1405,7 +1405,7 @@ long populate_vma_page_range(struct vm_area_struct *vma,
VM_BUG_ON(end & ~PAGE_MASK);
VM_BUG_ON_VMA(start < vma->vm_start, vma);
VM_BUG_ON_VMA(end > vma->vm_end, vma);
- VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
+ mmap_assert_locked(mm);

gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
if (vma->vm_flags & VM_LOCKONFAULT)
diff --git a/mm/hmm.c b/mm/hmm.c
index 280585833adf..660a4bcf932a 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -581,7 +581,7 @@ long hmm_range_fault(struct hmm_range *range)
struct mm_struct *mm = range->notifier->mm;
int ret;

- lockdep_assert_held(&mm->mmap_sem);
+ mmap_assert_locked(mm);

do {
/* If range is no longer valid force retry. */
diff --git a/mm/memory.c b/mm/memory.c
index e6dd3309c5a3..20f98ea8968e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1214,7 +1214,7 @@ static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
next = pud_addr_end(addr, end);
if (pud_trans_huge(*pud) || pud_devmap(*pud)) {
if (next - addr != HPAGE_PUD_SIZE) {
- VM_BUG_ON_VMA(!rwsem_is_locked(&tlb->mm->mmap_sem), vma);
+ mmap_assert_locked(tlb->mm);
split_huge_pud(vma, pud, addr);
} else if (zap_huge_pud(tlb, vma, pud, addr))
goto next;
diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index cfd0a03bf5cc..24eb9d1ed0a7 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -609,7 +609,7 @@ int __mmu_notifier_register(struct mmu_notifier *subscription,
struct mmu_notifier_subscriptions *subscriptions = NULL;
int ret;

- lockdep_assert_held_write(&mm->mmap_sem);
+ mmap_assert_write_locked(mm);
BUG_ON(atomic_read(&mm->mm_users) <= 0);

if (IS_ENABLED(CONFIG_LOCKDEP)) {
@@ -761,7 +761,7 @@ struct mmu_notifier *mmu_notifier_get_locked(const struct mmu_notifier_ops *ops,
struct mmu_notifier *subscription;
int ret;

- lockdep_assert_held_write(&mm->mmap_sem);
+ mmap_assert_write_locked(mm);

if (mm->notifier_subscriptions) {
subscription = find_get_mmu_notifier(mm, ops);
@@ -1006,7 +1006,7 @@ int mmu_interval_notifier_insert_locked(
mm->notifier_subscriptions;
int ret;

- lockdep_assert_held_write(&mm->mmap_sem);
+ mmap_assert_write_locked(mm);

if (!subscriptions || !subscriptions->has_itree) {
ret = __mmu_notifier_register(NULL, mm);
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 928df1638c30..3b452aa05cd0 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -395,7 +395,7 @@ int walk_page_range(struct mm_struct *mm, unsigned long start,
if (!walk.mm)
return -EINVAL;

- lockdep_assert_held(&walk.mm->mmap_sem);
+ mmap_assert_locked(walk.mm);

vma = find_vma(walk.mm, start);
do {
@@ -453,7 +453,7 @@ int walk_page_range_novma(struct mm_struct *mm, unsigned long start,
if (start >= end || !walk.mm)
return -EINVAL;

- lockdep_assert_held(&walk.mm->mmap_sem);
+ mmap_assert_locked(walk.mm);

return __walk_page_range(start, end, &walk);
}
@@ -472,7 +472,7 @@ int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
if (!walk.mm)
return -EINVAL;

- lockdep_assert_held(&walk.mm->mmap_sem);
+ mmap_assert_locked(walk.mm);

err = walk_page_test(vma->vm_start, vma->vm_end, &walk);
if (err > 0)
diff --git a/mm/util.c b/mm/util.c
index ea2e15b21446..e7cf9c815f5a 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -437,7 +437,7 @@ int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
unsigned long locked_vm, limit;
int ret = 0;

- lockdep_assert_held_write(&mm->mmap_sem);
+ mmap_assert_write_locked(mm);

locked_vm = mm->locked_vm;
if (inc) {
--
2.26.2.761.g0e0b3e54be-goog
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