On Wed, 24 May 2023 11:47:28 +1000
Alistair Popple <apopple@xxxxxxxxxx> wrote:
It is actually commit 4e15a073a168 ("Revert "mm, mmu_notifier:
annotate mmu notifiers with blockable invalidate callbacks"")'s problem.
It tries to revert commit 5ff7091f5a2c but forgets to get back this
piece of comment.
It would be better to have a Fixes tag in the commit message.
> The .invalidate_range() callback is called by
> mmu_notifier_invalidate_range() which is often called while holding
> the ptl spin-lock. Therefore any implementations of this callback must
> not sleep. This was originally documented when the call back was added
> in commit 0f0a327fa12c ("mmu_notifier: add the callback for
> mmu_notifier_invalidate_range()") but appears to have been
> inadvertently removed by commit 5ff7091f5a2c ("mm, mmu_notifier:
> annotate mmu notifiers with blockable invalidate callbacks").
>
> Restore the comment to make it clear that .invalidate_range()
> callbacks may not sleep.
>
> Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>
> ---
> include/linux/mmu_notifier.h | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
> index 64a3e05..447d757 100644
> --- a/include/linux/mmu_notifier.h
> +++ b/include/linux/mmu_notifier.h
> @@ -200,6 +200,9 @@ struct mmu_notifier_ops {
> * external TLB range needs to be flushed. For more in depth
> * discussion on this see Documentation/mm/mmu_notifier.rst
> *
> + * The invalidate_range() function is called under the ptl
> + * spin-lock and not allowed to sleep.
> + *
> * Note that this function might be called with just a sub-range
> * of what was passed to invalidate_range_start()/end(), if
> * called between those functions.
>
> base-commit: 44c026a73be8038f03dbdeef028b642880cf1511
