Re: [PATCH v7 3/7] mm: check fatal signal pending of target process

[Vlastimil Babka <vbabka@suse.cz>]

On 3/2/20 8:36 PM, Minchan Kim wrote:
> Bail out to prevent unnecessary CPU overhead if target process has
> pending fatal signal during (MADV_COLD|MADV_PAGEOUT) operation.
> 
> Reviewed-by: Suren Baghdasaryan <surenb@google.com>
> Signed-off-by: Minchan Kim <minchan@kernel.org>

Reviewed-by: Vlastimil Babka <vbabka@suse.cz>

Nit below:

> ---
>  mm/madvise.c | 29 +++++++++++++++++++++--------
>  1 file changed, 21 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 349473fc6683..6543f2bfc3d8 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -36,6 +36,7 @@
>  struct madvise_walk_private {
>  	struct mmu_gather *tlb;
>  	bool pageout;
> +	struct task_struct *target_task;
>  };
>  
>  /*
> @@ -316,6 +317,10 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
>  	if (fatal_signal_pending(current))
>  		return -EINTR;
>  
> +	if (private->target_task &&
> +			fatal_signal_pending(private->target_task))
> +		return -EINTR;

With madvise(2) private->target_task will be current, thus current will be
tested twice. Not wrong, but maybe add a "private->target_task != current"
condition?