[PATCH v3 10/10] mmap locking API: rename mmap_sem to mmap_lock

Michel Lespinasse
2020-03-27T22:51:36Z

Rename the mmap_sem field to mmap_lock. Any new uses of this lock
should now go through the new mmap locking api. The mmap_lock is
still implemented as a rwsem, though this could change in the future.

Signed-off-by: Michel Lespinasse <walken@google.com>
---
arch/ia64/mm/fault.c | 4 ++--
arch/x86/events/core.c | 4 ++--
arch/x86/kernel/tboot.c | 2 +-
arch/x86/mm/fault.c | 2 +-
drivers/firmware/efi/efi.c | 2 +-
drivers/gpu/drm/etnaviv/etnaviv_gem.c | 2 +-
fs/userfaultfd.c | 6 +++---
include/linux/mm_types.h | 2 +-
include/linux/mmap_lock.h | 28 +++++++++++++--------------
mm/gup.c | 2 +-
mm/hmm.c | 2 +-
mm/init-mm.c | 2 +-
mm/memory.c | 4 ++--
mm/mmap.c | 4 ++--
mm/mmu_notifier.c | 18 ++++++++---------
mm/pagewalk.c | 15 +++++++-------
mm/util.c | 4 ++--
17 files changed, 52 insertions(+), 51 deletions(-)

diff --git a/arch/ia64/mm/fault.c b/arch/ia64/mm/fault.c
index b423f0a970e4..70c7c7909cc5 100644
--- a/arch/ia64/mm/fault.c
+++ b/arch/ia64/mm/fault.c
@@ -70,8 +70,8 @@ ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *re
mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
| (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT));

- /* mmap_sem is performance critical.... */
- prefetchw(&mm->mmap_sem);
+ /* mmap_lock is performance critical.... */
+ prefetchw(&mm->mmap_lock);

/*
* If we're in an interrupt or have no user context, we must not take the fault..
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 3bb738f5a472..ad21924c575e 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2179,10 +2179,10 @@ static void x86_pmu_event_mapped(struct perf_event *event, struct mm_struct *mm)
* userspace with CR4.PCE clear while another task is still
* doing on_each_cpu_mask() to propagate CR4.PCE.
*
- * For now, this can't happen because all callers hold mmap_sem
+ * For now, this can't happen because all callers hold mmap_lock
* for write. If this changes, we'll need a different solution.
*/
- lockdep_assert_held_write(&mm->mmap_sem);
+ lockdep_assert_held_write(&mm->mmap_lock);

if (atomic_inc_return(&mm->context.perf_rdpmc_allowed) == 1)
on_each_cpu_mask(mm_cpumask(mm), refresh_pce, NULL, 1);
diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
index 4b79335624b1..4792e8778b28 100644
--- a/arch/x86/kernel/tboot.c
+++ b/arch/x86/kernel/tboot.c
@@ -90,7 +90,7 @@ static struct mm_struct tboot_mm = {
.pgd = swapper_pg_dir,
.mm_users = ATOMIC_INIT(2),
.mm_count = ATOMIC_INIT(1),
- .mmap_sem = MMAP_LOCK_INITIALIZER(init_mm.mmap_sem),
+ .mmap_lock = MMAP_LOCK_INITIALIZER(init_mm.mmap_lock),
.page_table_lock = __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock),
.mmlist = LIST_HEAD_INIT(init_mm.mmlist),
};
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 5bb97d2a7d3b..98d413e6fbb2 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1526,7 +1526,7 @@ dotraplinkage void
do_page_fault(struct pt_regs *regs, unsigned long hw_error_code,
unsigned long address)
{
- prefetchw(&current->mm->mmap_sem);
+ prefetchw(&current->mm->mmap_lock);
trace_page_fault_entries(regs, hw_error_code, address);

if (unlikely(kmmio_fault(regs, address)))
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 5bdfe698cd7f..d38e0e85eb0d 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -60,7 +60,7 @@ struct mm_struct efi_mm = {
.mm_rb = RB_ROOT,
.mm_users = ATOMIC_INIT(2),
.mm_count = ATOMIC_INIT(1),
- .mmap_sem = MMAP_LOCK_INITIALIZER(efi_mm.mmap_sem),
+ .mmap_lock = MMAP_LOCK_INITIALIZER(efi_mm.mmap_lock),
.page_table_lock = __SPIN_LOCK_UNLOCKED(efi_mm.page_table_lock),
.mmlist = LIST_HEAD_INIT(efi_mm.mmlist),
.cpu_bitmap = { [BITS_TO_LONGS(NR_CPUS)] = 0},
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
index 6adea180d629..3470482d95bc 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
@@ -661,7 +661,7 @@ static int etnaviv_gem_userptr_get_pages(struct etnaviv_gem_object *etnaviv_obj)
struct etnaviv_gem_userptr *userptr = &etnaviv_obj->userptr;
int ret, pinned = 0, npages = etnaviv_obj->base.size >> PAGE_SHIFT;

- might_lock_read(&current->mm->mmap_sem);
+ might_lock_read(&current->mm->mmap_lock);

if (userptr->mm != current->mm)
return -EPERM;
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index ad1ce223ee6a..faea442c8fed 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;

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

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;

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

pgd = pgd_offset(mm, address);
if (!pgd_present(*pgd))
@@ -376,7 +376,7 @@ 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.
*/
- lockdep_assert_held(&mm->mmap_sem);
+ lockdep_assert_held(&mm->mmap_lock);

ctx = vmf->vma->vm_userfaultfd_ctx.ctx;
if (!ctx)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index c28911c3afa8..a168d13b5c44 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -431,7 +431,7 @@ struct mm_struct {
spinlock_t page_table_lock; /* Protects page tables and some
* counters
*/
- struct rw_semaphore mmap_sem;
+ struct rw_semaphore mmap_lock;

struct list_head mmlist; /* List of maybe swapped mm's. These
* are globally strung together off
diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h
index 25a8a5458b84..8670d4ceaba9 100644
--- a/include/linux/mmap_lock.h
+++ b/include/linux/mmap_lock.h
@@ -5,73 +5,73 @@

static inline void mmap_init_lock(struct mm_struct *mm)
{
- init_rwsem(&mm->mmap_sem);
+ init_rwsem(&mm->mmap_lock);
}

static inline void mmap_write_lock(struct mm_struct *mm)
{
- down_write(&mm->mmap_sem);
+ down_write(&mm->mmap_lock);
}

static inline void mmap_write_lock_nested(struct mm_struct *mm, int subclass)
{
- down_write_nested(&mm->mmap_sem, subclass);
+ down_write_nested(&mm->mmap_lock, subclass);
}

static inline int mmap_write_lock_killable(struct mm_struct *mm)
{
- return down_write_killable(&mm->mmap_sem);
+ return down_write_killable(&mm->mmap_lock);
}

static inline bool mmap_write_trylock(struct mm_struct *mm)
{
- return down_write_trylock(&mm->mmap_sem) != 0;
+ return down_write_trylock(&mm->mmap_lock) != 0;
}

static inline void mmap_write_unlock(struct mm_struct *mm)
{
- up_write(&mm->mmap_sem);
+ up_write(&mm->mmap_lock);
}

/* Pairs with mmap_write_lock_nested() */
static inline void mmap_write_unlock_nested(struct mm_struct *mm)
{
- up_write(&mm->mmap_sem);
+ up_write(&mm->mmap_lock);
}

static inline void mmap_downgrade_write_lock(struct mm_struct *mm)
{
- downgrade_write(&mm->mmap_sem);
+ downgrade_write(&mm->mmap_lock);
}

static inline void mmap_read_lock(struct mm_struct *mm)
{
- down_read(&mm->mmap_sem);
+ down_read(&mm->mmap_lock);
}

static inline int mmap_read_lock_killable(struct mm_struct *mm)
{
- return down_read_killable(&mm->mmap_sem);
+ return down_read_killable(&mm->mmap_lock);
}

static inline bool mmap_read_trylock(struct mm_struct *mm)
{
- return down_read_trylock(&mm->mmap_sem) != 0;
+ return down_read_trylock(&mm->mmap_lock) != 0;
}

static inline void mmap_read_unlock(struct mm_struct *mm)
{
- up_read(&mm->mmap_sem);
+ up_read(&mm->mmap_lock);
}

static inline void mmap_read_release(struct mm_struct *mm, unsigned long ip)
{
- rwsem_release(&mm->mmap_sem.dep_map, ip);
+ rwsem_release(&mm->mmap_lock.dep_map, ip);
}

static inline void mmap_read_unlock_non_owner(struct mm_struct *mm)
{
- up_read_non_owner(&mm->mmap_sem);
+ up_read_non_owner(&mm->mmap_lock);
}

#endif /* _LINUX_MMAP_LOCK_H */
diff --git a/mm/gup.c b/mm/gup.c
index 1e225eba4787..9c90d5e04897 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1154,7 +1154,7 @@ 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);
- lockdep_assert_held(&mm->mmap_sem);
+ lockdep_assert_held(&mm->mmap_lock);

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 72e5a6d9a417..4d736a710910 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -681,7 +681,7 @@ long hmm_range_fault(struct hmm_range *range, unsigned int flags)
struct mm_struct *mm = range->notifier->mm;
int ret;

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

do {
/* If range is no longer valid force retry. */
diff --git a/mm/init-mm.c b/mm/init-mm.c
index 3c128bd6a30c..2b16924419b4 100644
--- a/mm/init-mm.c
+++ b/mm/init-mm.c
@@ -31,7 +31,7 @@ struct mm_struct init_mm = {
.pgd = swapper_pg_dir,
.mm_users = ATOMIC_INIT(2),
.mm_count = ATOMIC_INIT(1),
- .mmap_sem = MMAP_LOCK_INITIALIZER(init_mm.mmap_sem),
+ .mmap_lock = MMAP_LOCK_INITIALIZER(init_mm.mmap_lock),
.page_table_lock = __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock),
.arg_lock = __SPIN_LOCK_UNLOCKED(init_mm.arg_lock),
.mmlist = LIST_HEAD_INIT(init_mm.mmlist),
diff --git a/mm/memory.c b/mm/memory.c
index 4c125f0a1df9..afb86afc5832 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1202,7 +1202,7 @@ 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) {
- lockdep_assert_held(&tlb->mm->mmap_sem);
+ lockdep_assert_held(&tlb->mm->mmap_lock);
split_huge_pud(vma, pud, addr);
} else if (zap_huge_pud(tlb, vma, pud, addr))
goto next;
@@ -4648,7 +4648,7 @@ void __might_fault(const char *file, int line)
__might_sleep(file, line, 0);
#if defined(CONFIG_DEBUG_ATOMIC_SLEEP)
if (current->mm)
- might_lock_read(&current->mm->mmap_sem);
+ might_lock_read(&current->mm->mmap_lock);
#endif
}
EXPORT_SYMBOL(__might_fault);
diff --git a/mm/mmap.c b/mm/mmap.c
index ba51ff516ec0..c81db16c8c23 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3450,7 +3450,7 @@ static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
* The LSB of head.next can't change from under us
* because we hold the mm_all_locks_mutex.
*/
- down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_sem);
+ down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_lock);
/*
* We can safely modify head.next after taking the
* anon_vma->root->rwsem. If some other vma in this mm shares
@@ -3480,7 +3480,7 @@ static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
*/
if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
BUG();
- down_write_nest_lock(&mapping->i_mmap_rwsem, &mm->mmap_sem);
+ down_write_nest_lock(&mapping->i_mmap_rwsem, &mm->mmap_lock);
}
}

diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index cfd0a03bf5cc..6717278d6d49 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -599,7 +599,7 @@ void __mmu_notifier_invalidate_range(struct mm_struct *mm,
}

/*
- * Same as mmu_notifier_register but here the caller must hold the mmap_sem in
+ * Same as mmu_notifier_register but here the caller must hold the mmap_lock in
* write mode. A NULL mn signals the notifier is being registered for itree
* mode.
*/
@@ -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);
+ lockdep_assert_held_write(&mm->mmap_lock);
BUG_ON(atomic_read(&mm->mm_users) <= 0);

if (IS_ENABLED(CONFIG_LOCKDEP)) {
@@ -623,7 +623,7 @@ int __mmu_notifier_register(struct mmu_notifier *subscription,
/*
* kmalloc cannot be called under mm_take_all_locks(), but we
* know that mm->notifier_subscriptions can't change while we
- * hold the write side of the mmap_sem.
+ * hold the write side of the mmap_lock.
*/
subscriptions = kzalloc(
sizeof(struct mmu_notifier_subscriptions), GFP_KERNEL);
@@ -655,7 +655,7 @@ int __mmu_notifier_register(struct mmu_notifier *subscription,
* readers. acquire can only be used while holding the mmgrab or
* mmget, and is safe because once created the
* mmu_notifier_subscriptions is not freed until the mm is destroyed.
- * As above, users holding the mmap_sem or one of the
+ * As above, users holding the mmap_lock or one of the
* mm_take_all_locks() do not need to use acquire semantics.
*/
if (subscriptions)
@@ -689,7 +689,7 @@ EXPORT_SYMBOL_GPL(__mmu_notifier_register);
* @mn: The notifier to attach
* @mm: The mm to attach the notifier to
*
- * Must not hold mmap_sem nor any other VM related lock when calling
+ * Must not hold mmap_lock nor any other VM related lock when calling
* this registration function. Must also ensure mm_users can't go down
* to zero while this runs to avoid races with mmu_notifier_release,
* so mm has to be current->mm or the mm should be pinned safely such
@@ -750,7 +750,7 @@ find_get_mmu_notifier(struct mm_struct *mm, const struct mmu_notifier_ops *ops)
* are the same.
*
* Each call to mmu_notifier_get() must be paired with a call to
- * mmu_notifier_put(). The caller must hold the write side of mm->mmap_sem.
+ * mmu_notifier_put(). The caller must hold the write side of mm->mmap_lock.
*
* While the caller has a mmu_notifier get the mm pointer will remain valid,
* and can be converted to an active mm pointer via mmget_not_zero().
@@ -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);
+ lockdep_assert_held_write(&mm->mmap_lock);

if (mm->notifier_subscriptions) {
subscription = find_get_mmu_notifier(mm, ops);
@@ -983,7 +983,7 @@ int mmu_interval_notifier_insert(struct mmu_interval_notifier *interval_sub,
struct mmu_notifier_subscriptions *subscriptions;
int ret;

- might_lock(&mm->mmap_sem);
+ might_lock(&mm->mmap_lock);

subscriptions = smp_load_acquire(&mm->notifier_subscriptions);
if (!subscriptions || !subscriptions->has_itree) {
@@ -1006,7 +1006,7 @@ int mmu_interval_notifier_insert_locked(
mm->notifier_subscriptions;
int ret;

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

if (!subscriptions || !subscriptions->has_itree) {
ret = __mmu_notifier_register(NULL, mm);
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 928df1638c30..d669a3146c0f 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -373,8 +373,9 @@ static int __walk_page_range(unsigned long start, unsigned long end,
* caller-specific data to callbacks, @private should be helpful.
*
* Locking:
- * Callers of walk_page_range() and walk_page_vma() should hold @mm->mmap_sem,
- * because these function traverse vma list and/or access to vma's data.
+ * Callers of walk_page_range() and walk_page_vma() should hold
+ * @mm->mmap_lock, because these function traverse the vma list
+ * and/or access the vma's data.
*/
int walk_page_range(struct mm_struct *mm, unsigned long start,
unsigned long end, const struct mm_walk_ops *ops,
@@ -395,7 +396,7 @@ int walk_page_range(struct mm_struct *mm, unsigned long start,
if (!walk.mm)
return -EINVAL;

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

vma = find_vma(walk.mm, start);
do {
@@ -453,7 +454,7 @@ 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);
+ lockdep_assert_held(&walk.mm->mmap_lock);

return __walk_page_range(start, end, &walk);
}
@@ -472,7 +473,7 @@ 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);
+ lockdep_assert_held(&walk.mm->mmap_lock);

err = walk_page_test(vma->vm_start, vma->vm_end, &walk);
if (err > 0)
@@ -498,11 +499,11 @@ int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
* Also see walk_page_range() for additional information.
*
* Locking:
- * This function can't require that the struct mm_struct::mmap_sem is held,
+ * This function can't require that the struct mm_struct::mmap_lock is held,
* since @mapping may be mapped by multiple processes. Instead
* @mapping->i_mmap_rwsem must be held. This might have implications in the
* callbacks, and it's up tho the caller to ensure that the
- * struct mm_struct::mmap_sem is not needed.
+ * struct mm_struct::mmap_lock is not needed.
*
* Also this means that a caller can't rely on the struct
* vm_area_struct::vm_flags to be constant across a call,
diff --git a/mm/util.c b/mm/util.c
index ea2e15b21446..56c562f7ad19 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -425,7 +425,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
* @bypass_rlim: %true if checking RLIMIT_MEMLOCK should be skipped
*
* Assumes @task and @mm are valid (i.e. at least one reference on each), and
- * that mmap_sem is held as writer.
+ * that mmap_lock is held as writer.
*
* Return:
* * 0 on success
@@ -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);
+ lockdep_assert_held_write(&mm->mmap_lock);

locked_vm = mm->locked_vm;
if (inc) {
--
2.26.0.rc2.310.g2932bb562d-goog