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5e31275cc9
Introduce per-VMA locking. The lock implementation relies on a per-vma
and per-mm sequence counters to note exclusive locking:
- read lock - (implemented by vma_start_read) requires the vma
(vm_lock_seq) and mm (mm_lock_seq) sequence counters to differ.
If they match then there must be a vma exclusive lock held somewhere.
- read unlock - (implemented by vma_end_read) is a trivial vma->lock
unlock.
- write lock - (vma_start_write) requires the mmap_lock to be held
exclusively and the current mm counter is assigned to the vma counter.
This will allow multiple vmas to be locked under a single mmap_lock
write lock (e.g. during vma merging). The vma counter is modified
under exclusive vma lock.
- write unlock - (vma_end_write_all) is a batch release of all vma
locks held. It doesn't pair with a specific vma_start_write! It is
done before exclusive mmap_lock is released by incrementing mm
sequence counter (mm_lock_seq).
- write downgrade - if the mmap_lock is downgraded to the read lock, all
vma write locks are released as well (effectivelly same as write
unlock).
Link: https://lkml.kernel.org/r/20230227173632.3292573-13-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
184 lines
4.6 KiB
C
184 lines
4.6 KiB
C
#ifndef _LINUX_MMAP_LOCK_H
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#define _LINUX_MMAP_LOCK_H
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#include <linux/lockdep.h>
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#include <linux/mm_types.h>
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#include <linux/mmdebug.h>
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#include <linux/rwsem.h>
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#include <linux/tracepoint-defs.h>
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#include <linux/types.h>
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#define MMAP_LOCK_INITIALIZER(name) \
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.mmap_lock = __RWSEM_INITIALIZER((name).mmap_lock),
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DECLARE_TRACEPOINT(mmap_lock_start_locking);
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DECLARE_TRACEPOINT(mmap_lock_acquire_returned);
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DECLARE_TRACEPOINT(mmap_lock_released);
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#ifdef CONFIG_TRACING
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void __mmap_lock_do_trace_start_locking(struct mm_struct *mm, bool write);
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void __mmap_lock_do_trace_acquire_returned(struct mm_struct *mm, bool write,
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bool success);
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void __mmap_lock_do_trace_released(struct mm_struct *mm, bool write);
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static inline void __mmap_lock_trace_start_locking(struct mm_struct *mm,
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bool write)
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{
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if (tracepoint_enabled(mmap_lock_start_locking))
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__mmap_lock_do_trace_start_locking(mm, write);
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}
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static inline void __mmap_lock_trace_acquire_returned(struct mm_struct *mm,
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bool write, bool success)
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{
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if (tracepoint_enabled(mmap_lock_acquire_returned))
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__mmap_lock_do_trace_acquire_returned(mm, write, success);
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}
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static inline void __mmap_lock_trace_released(struct mm_struct *mm, bool write)
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{
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if (tracepoint_enabled(mmap_lock_released))
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__mmap_lock_do_trace_released(mm, write);
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}
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#else /* !CONFIG_TRACING */
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static inline void __mmap_lock_trace_start_locking(struct mm_struct *mm,
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bool write)
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{
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}
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static inline void __mmap_lock_trace_acquire_returned(struct mm_struct *mm,
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bool write, bool success)
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{
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}
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static inline void __mmap_lock_trace_released(struct mm_struct *mm, bool write)
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{
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}
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#endif /* CONFIG_TRACING */
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static inline void mmap_assert_locked(struct mm_struct *mm)
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{
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lockdep_assert_held(&mm->mmap_lock);
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VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm);
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}
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static inline void mmap_assert_write_locked(struct mm_struct *mm)
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{
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lockdep_assert_held_write(&mm->mmap_lock);
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VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm);
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}
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#ifdef CONFIG_PER_VMA_LOCK
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static inline void vma_end_write_all(struct mm_struct *mm)
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{
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mmap_assert_write_locked(mm);
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/* No races during update due to exclusive mmap_lock being held */
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WRITE_ONCE(mm->mm_lock_seq, mm->mm_lock_seq + 1);
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}
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#else
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static inline void vma_end_write_all(struct mm_struct *mm) {}
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#endif
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static inline void mmap_init_lock(struct mm_struct *mm)
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{
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init_rwsem(&mm->mmap_lock);
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}
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static inline void mmap_write_lock(struct mm_struct *mm)
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{
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__mmap_lock_trace_start_locking(mm, true);
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down_write(&mm->mmap_lock);
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__mmap_lock_trace_acquire_returned(mm, true, true);
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}
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static inline void mmap_write_lock_nested(struct mm_struct *mm, int subclass)
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{
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__mmap_lock_trace_start_locking(mm, true);
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down_write_nested(&mm->mmap_lock, subclass);
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__mmap_lock_trace_acquire_returned(mm, true, true);
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}
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static inline int mmap_write_lock_killable(struct mm_struct *mm)
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{
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int ret;
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__mmap_lock_trace_start_locking(mm, true);
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ret = down_write_killable(&mm->mmap_lock);
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__mmap_lock_trace_acquire_returned(mm, true, ret == 0);
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return ret;
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}
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static inline bool mmap_write_trylock(struct mm_struct *mm)
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{
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bool ret;
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__mmap_lock_trace_start_locking(mm, true);
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ret = down_write_trylock(&mm->mmap_lock) != 0;
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__mmap_lock_trace_acquire_returned(mm, true, ret);
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return ret;
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}
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static inline void mmap_write_unlock(struct mm_struct *mm)
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{
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__mmap_lock_trace_released(mm, true);
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vma_end_write_all(mm);
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up_write(&mm->mmap_lock);
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}
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static inline void mmap_write_downgrade(struct mm_struct *mm)
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{
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__mmap_lock_trace_acquire_returned(mm, false, true);
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vma_end_write_all(mm);
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downgrade_write(&mm->mmap_lock);
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}
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static inline void mmap_read_lock(struct mm_struct *mm)
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{
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__mmap_lock_trace_start_locking(mm, false);
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down_read(&mm->mmap_lock);
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__mmap_lock_trace_acquire_returned(mm, false, true);
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}
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static inline int mmap_read_lock_killable(struct mm_struct *mm)
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{
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int ret;
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__mmap_lock_trace_start_locking(mm, false);
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ret = down_read_killable(&mm->mmap_lock);
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__mmap_lock_trace_acquire_returned(mm, false, ret == 0);
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return ret;
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}
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static inline bool mmap_read_trylock(struct mm_struct *mm)
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{
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bool ret;
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__mmap_lock_trace_start_locking(mm, false);
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ret = down_read_trylock(&mm->mmap_lock) != 0;
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__mmap_lock_trace_acquire_returned(mm, false, ret);
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return ret;
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}
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static inline void mmap_read_unlock(struct mm_struct *mm)
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{
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__mmap_lock_trace_released(mm, false);
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up_read(&mm->mmap_lock);
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}
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static inline void mmap_read_unlock_non_owner(struct mm_struct *mm)
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{
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__mmap_lock_trace_released(mm, false);
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up_read_non_owner(&mm->mmap_lock);
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}
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static inline int mmap_lock_is_contended(struct mm_struct *mm)
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{
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return rwsem_is_contended(&mm->mmap_lock);
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}
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#endif /* _LINUX_MMAP_LOCK_H */
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