linux-kernel - Re: [PATCH 1/4] lib/rhashtable: simplify bucket_table

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Message-ID: <87sh5fbbma.fsf@notabene.neil.brown.name>
Date:   Fri, 22 Jun 2018 16:04:29 +1000
From:   NeilBrown <neilb@...e.com>
To:     Davidlohr Bueso <dave@...olabs.net>, akpm@...ux-foundation.org,
        torvalds@...ux-foundation.org
Cc:     tgraf@...g.ch, herbert@...dor.apana.org.au,
        manfred@...orfullife.com, mhocko@...nel.org,
        guillaume.knispel@...ersonicimagine.com, linux-api@...r.kernel.org,
        linux-kernel@...r.kernel.org, dave@...olabs.net,
        Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 1/4] lib/rhashtable: simplify bucket_table_alloc()

On Thu, Jun 21 2018, Davidlohr Bueso wrote:

> As of ce91f6ee5 (mm: kvmalloc does not fallback to vmalloc for incompatible gfp flag),
> we can simplify the caller and trust kvzalloc() to just do the right thing.

Hi,
 it isn't clear to me that this is true.
 With this change we lose __GFP_NOWARN and __GFP_NORETRY.
 I doubt the NORETRY is particularly important as this is if it
 isn't GFP_KERNEL, then it is GFP_ATOMIC which doesn't retry anyway.
 However I cannot see why this patch won't result in warnings when the
 kzalloc() fails.
 What am I missing?

Thanks,
NeilBrown


>
> Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
> ---
>  lib/rhashtable.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/lib/rhashtable.c b/lib/rhashtable.c
> index 9427b5766134..26c9cd8a985a 100644
> --- a/lib/rhashtable.c
> +++ b/lib/rhashtable.c
> @@ -175,10 +175,7 @@ static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
>  	int i;
>  
>  	size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
> -	if (gfp != GFP_KERNEL)
> -		tbl = kzalloc(size, gfp | __GFP_NOWARN | __GFP_NORETRY);
> -	else
> -		tbl = kvzalloc(size, gfp);
> +	tbl = kvzalloc(size, gfp);
>  
>  	size = nbuckets;
>  
> -- 
> 2.16.4

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