diff options
| -rw-r--r-- | include/linux/mm.h | 5 | ||||
| -rw-r--r-- | include/linux/mmap_lock.h | 8 | ||||
| -rw-r--r-- | mm/mmap.c | 7 |
3 files changed, 19 insertions, 1 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 84988d4ff8fb..93eb291181f7 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -691,6 +691,11 @@ static bool __is_vma_write_locked(struct vm_area_struct *vma, int *mm_lock_seq) return (vma->vm_lock_seq == *mm_lock_seq); } +/* + * Begin writing to a VMA. + * Exclude concurrent readers under the per-VMA lock until the currently + * write-locked mmap_lock is dropped or downgraded. + */ static inline void vma_start_write(struct vm_area_struct *vma) { int mm_lock_seq; diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h index a5c63b6d7d46..8d38dcb6d044 100644 --- a/include/linux/mmap_lock.h +++ b/include/linux/mmap_lock.h @@ -73,6 +73,14 @@ static inline void mmap_assert_write_locked(struct mm_struct *mm) } #ifdef CONFIG_PER_VMA_LOCK +/* + * Drop all currently-held per-VMA locks. + * This is called from the mmap_lock implementation directly before releasing + * a write-locked mmap_lock (or downgrading it to read-locked). + * This should normally NOT be called manually from other places. + * If you want to call this manually anyway, keep in mind that this will release + * *all* VMA write locks, including ones from further up the stack. + */ static inline void vma_end_write_all(struct mm_struct *mm) { mmap_assert_write_locked(mm); diff --git a/mm/mmap.c b/mm/mmap.c index 7bd1caa09ddd..4a9466b76648 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -3642,6 +3642,12 @@ int mm_take_all_locks(struct mm_struct *mm) mutex_lock(&mm_all_locks_mutex); + /* + * vma_start_write() does not have a complement in mm_drop_all_locks() + * because vma_start_write() is always asymmetrical; it marks a VMA as + * being written to until mmap_write_unlock() or mmap_write_downgrade() + * is reached. + */ mas_for_each(&mas, vma, ULONG_MAX) { if (signal_pending(current)) goto out_unlock; @@ -3738,7 +3744,6 @@ void mm_drop_all_locks(struct mm_struct *mm) if (vma->vm_file && vma->vm_file->f_mapping) vm_unlock_mapping(vma->vm_file->f_mapping); } - vma_end_write_all(mm); mutex_unlock(&mm_all_locks_mutex); } |