On Wed, Oct 01, 2014 at 10:56:35AM +0200, Andrea Arcangeli wrote:
> +static inline long __get_user_pages_locked(struct task_struct *tsk,
> + struct mm_struct *mm,
> + unsigned long start,
> + unsigned long nr_pages,
> + int write, int force,
> + struct page **pages,
> + struct vm_area_struct **vmas,
> + int *locked,
> + bool notify_drop)
> +{
> + if (notify_drop && lock_dropped && *locked) {
> + /*
> + * We must let the caller know we temporarily dropped the lock
> + * and so the critical section protected by it was lost.
> + */
> + up_read(&mm->mmap_sem);
> + *locked = 0;
> + }
> + return pages_done;
> +}
> +long get_user_pages_locked(struct task_struct *tsk, struct mm_struct *mm,
> + unsigned long start, unsigned long nr_pages,
> + int write, int force, struct page **pages,
> + int *locked)
> +{
> + return __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
> + pages, NULL, locked, true);
> +}
> +long get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
> + unsigned long start, unsigned long nr_pages,
> + int write, int force, struct page **pages)
> +{
> + long ret;
> + int locked = 1;
> + down_read(&mm->mmap_sem);
> + ret = __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
> + pages, NULL, &locked, false);
> + if (locked)
> + up_read(&mm->mmap_sem);
> + return ret;
> +}
> long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
> unsigned long start, unsigned long nr_pages, int write,
> int force, struct page **pages, struct vm_area_struct **vmas)
> {
> + return __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
> + pages, vmas, NULL, false);
> }
I'm wondering about that notify_drop parameter, what's the added
benefit? If you look at these 3 callers we can do away with it, since in
the second called where we have locked but !notify_drop we seem to do
the exact same thing afterwards anyway.
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