Re: [PATCH v3 hmm 05/11] mm/hmm: Remove duplicate condition test before wait_event_timeout

[Ira Weiny <ira.weiny@intel.com>]

On Fri, Jun 07, 2019 at 10:31:07AM -0300, Jason Gunthorpe wrote:
> The wait_event_timeout macro already tests the condition as its first
> action, so there is no reason to open code another version of this, all
> that does is skip the might_sleep() debugging in common cases, which is
> not helpful.
> 
> Further, based on prior patches, we can now simplify the required condition
> test:
>  - If range is valid memory then so is range->hmm
>  - If hmm_release() has run then range->valid is set to false
>    at the same time as dead, so no reason to check both.
>  - A valid hmm has a valid hmm->mm.
> 
> Allowing the return value of wait_event_timeout() (along with its internal
> barriers) to compute the result of the function.
> 
> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

Reviewed-by: Ira Weiny <ira.weiny@intel.com>

> ---
> v3
> - Simplify the wait_event_timeout to not check valid
> ---
>  include/linux/hmm.h | 13 ++-----------
>  1 file changed, 2 insertions(+), 11 deletions(-)
> 
> diff --git a/include/linux/hmm.h b/include/linux/hmm.h
> index 1d97b6d62c5bcf..26e7c477490c4e 100644
> --- a/include/linux/hmm.h
> +++ b/include/linux/hmm.h
> @@ -209,17 +209,8 @@ static inline unsigned long hmm_range_page_size(const struct hmm_range *range)
>  static inline bool hmm_range_wait_until_valid(struct hmm_range *range,
>  					      unsigned long timeout)
>  {
> -	/* Check if mm is dead ? */
> -	if (range->hmm == NULL || range->hmm->dead || range->hmm->mm == NULL) {
> -		range->valid = false;
> -		return false;
> -	}
> -	if (range->valid)
> -		return true;
> -	wait_event_timeout(range->hmm->wq, range->valid || range->hmm->dead,
> -			   msecs_to_jiffies(timeout));
> -	/* Return current valid status just in case we get lucky */
> -	return range->valid;
> +	return wait_event_timeout(range->hmm->wq, range->valid,
> +				  msecs_to_jiffies(timeout)) != 0;
>  }
>  
>  /*
> -- 
> 2.21.0
> 
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