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    SubjectRe: [PATCH v5.5 10/10] mmap locking API: rename mmap_sem to mmap_lock
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    Le 24/04/2020 à 03:39, Michel Lespinasse a écrit :
    > 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/mm/fault.c | 2 +-
    > drivers/gpu/drm/etnaviv/etnaviv_gem.c | 2 +-
    > include/linux/mm_types.h | 2 +-
    > include/linux/mmap_lock.h | 38 +++++++++++++--------------
    > mm/memory.c | 2 +-
    > mm/mmap.c | 4 +--
    > mm/mmu_notifier.c | 2 +-
    > 8 files changed, 28 insertions(+), 28 deletions(-)
    >
    > diff --git a/arch/ia64/mm/fault.c b/arch/ia64/mm/fault.c
    > index 693f00b117e1..9b95050c2048 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/mm/fault.c b/arch/x86/mm/fault.c
    > index 181f66b9049f..35f530f9dfc0 100644
    > --- a/arch/x86/mm/fault.c
    > +++ b/arch/x86/mm/fault.c
    > @@ -1522,7 +1522,7 @@ 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/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
    > index dc9ef302f517..701f3995f621 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);

    Why not a mm_might_lock_read() new API to hide the mmap_lock, and add it to the
    previous patch?

    >
    > if (userptr->mm != current->mm)
    > return -EPERM;
    > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
    > index 4aba6c0c2ba8..d13b90399c16 100644
    > --- a/include/linux/mm_types.h
    > +++ b/include/linux/mm_types.h
    > @@ -436,7 +436,7 @@ 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 5bf7cee5d93b..9dc632add390 100644
    > --- a/include/linux/mmap_lock.h
    > +++ b/include/linux/mmap_lock.h
    > @@ -4,67 +4,67 @@
    > #include <linux/mmdebug.h>
    >
    > #define MMAP_LOCK_INITIALIZER(name) \
    > - .mmap_sem = __RWSEM_INITIALIZER(name.mmap_sem),
    > + .mmap_lock = __RWSEM_INITIALIZER(name.mmap_lock),
    >
    > 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);
    > }
    >
    > static inline void mmap_write_downgrade(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 bool mmap_read_trylock_non_owner(struct mm_struct *mm)
    > {
    > - if (down_read_trylock(&mm->mmap_sem)) {
    > - rwsem_release(&mm->mmap_sem.dep_map, _RET_IP_);
    > + if (down_read_trylock(&mm->mmap_lock)) {
    > + rwsem_release(&mm->mmap_lock.dep_map, _RET_IP_);
    > return true;
    > }
    > return false;
    > @@ -72,19 +72,19 @@ static inline bool mmap_read_trylock_non_owner(struct mm_struct *mm)
    >
    > 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);
    > }
    >
    > static inline void mmap_assert_locked(struct mm_struct *mm)
    > {
    > - VM_BUG_ON_MM(!lockdep_is_held_type(&mm->mmap_sem, -1), mm);
    > - VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
    > + VM_BUG_ON_MM(!lockdep_is_held_type(&mm->mmap_lock, -1), mm);
    > + VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm);
    > }
    >
    > static inline void mmap_assert_write_locked(struct mm_struct *mm)
    > {
    > - VM_BUG_ON_MM(!lockdep_is_held_type(&mm->mmap_sem, 0), mm);
    > - VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
    > + VM_BUG_ON_MM(!lockdep_is_held_type(&mm->mmap_lock, 0), mm);
    > + VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm);
    > }
    >
    > #endif /* _LINUX_MMAP_LOCK_H */
    > diff --git a/mm/memory.c b/mm/memory.c
    > index 20f98ea8968e..c2963e7affa9 100644
    > --- a/mm/memory.c
    > +++ b/mm/memory.c
    > @@ -4811,7 +4811,7 @@ 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 2f4ffccc5972..80a47031d5db 100644
    > --- a/mm/mmap.c
    > +++ b/mm/mmap.c
    > @@ -3474,7 +3474,7 @@ 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
    > @@ -3504,7 +3504,7 @@ 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 24eb9d1ed0a7..2f348b6c9c9a 100644
    > --- a/mm/mmu_notifier.c
    > +++ b/mm/mmu_notifier.c
    > @@ -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);

    Same here with a new mm_might_lock()?

    >
    > subscriptions = smp_load_acquire(&mm->notifier_subscriptions);
    > if (!subscriptions || !subscriptions->has_itree) {
    >

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