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Date: Mon, 18 May 2020 15:45:22 +0200
From: Laurent Dufour <ldufour@...ux.ibm.com>
To: Michel Lespinasse <walken@...gle.com>,
Matthew Wilcox <willy@...radead.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
linux-mm <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>,
Peter Zijlstra <peterz@...radead.org>,
Vlastimil Babka <vbabka@...e.cz>,
Liam Howlett <Liam.Howlett@...cle.com>,
Jerome Glisse <jglisse@...hat.com>,
Davidlohr Bueso <dave@...olabs.net>,
David Rientjes <rientjes@...gle.com>,
Hugh Dickins <hughd@...gle.com>, Ying Han <yinghan@...gle.com>,
Jason Gunthorpe <jgg@...pe.ca>,
Daniel Jordan <daniel.m.jordan@...cle.com>
Subject: Re: [PATCH v5.5 10/10] mmap locking API: rename mmap_sem to mmap_lock
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@...gle.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(¤t->mm->mmap_sem);
> + prefetchw(¤t->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(¤t->mm->mmap_sem);
> + might_lock_read(¤t->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(¤t->mm->mmap_sem);
> + might_lock_read(¤t->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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