linux-kernel - Re: [PATCH] mm: document mmu_notifier_invalidate_range_start

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Message-ID: <87bkdz58jq.fsf@nvdebian.thelocal>
Date:   Tue, 19 Sep 2023 10:08:06 +1000
From:   Alistair Popple <apopple@...dia.com>
To:     Jann Horn <jannh@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Jason Gunthorpe <jgg@...pe.ca>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH] mm: document
 mmu_notifier_invalidate_range_start_nonblock()


Looks good, thanks.

Reviewed-by: Alistair Popple <apopple@...dia.com>

Jann Horn <jannh@...gle.com> writes:

> Document what mmu_notifier_invalidate_range_start_nonblock() is for.
> Also add a __must_check annotation to signal that callers must bail out if
> a notifier vetoes the operation.
>
> Signed-off-by: Jann Horn <jannh@...gle.com>
> ---
>  include/linux/mmu_notifier.h | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
> index 6e3c857606f1..f349e08a9dfe 100644
> --- a/include/linux/mmu_notifier.h
> +++ b/include/linux/mmu_notifier.h
> @@ -459,7 +459,14 @@ mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)
>  	lock_map_release(&__mmu_notifier_invalidate_range_start_map);
>  }
>  
> -static inline int
> +/*
> + * This version of mmu_notifier_invalidate_range_start() avoids blocking, but it
> + * can return an error if a notifier can't proceed without blocking, in which
> + * case you're not allowed to modify PTEs in the specified range.
> + *
> + * This is mainly intended for OOM handling.
> + */
> +static inline int __must_check
>  mmu_notifier_invalidate_range_start_nonblock(struct mmu_notifier_range *range)
>  {
>  	int ret = 0;
>
> base-commit: 6704c78e2963a5682b4ac3c0e609d36f2405cf17