linux-kernel - Re: [PATCH v2 1/4] lib/rhashtable: simplify bucket_table

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Message-ID: <20180625091314.GG28965@dhcp22.suse.cz>
Date:   Mon, 25 Jun 2018 11:13:14 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
        tgraf@...g.ch, herbert@...dor.apana.org.au,
        manfred@...orfullife.com, guillaume.knispel@...ersonicimagine.com,
        linux-api@...r.kernel.org, linux-kernel@...r.kernel.org,
        Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH v2 1/4] lib/rhashtable: simplify bucket_table_alloc()

On Fri 22-06-18 11:15:40, Davidlohr Bueso wrote:
> As of ce91f6ee5b3 (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. For the
> case of the GFP_ATOMIC context, we can drop the __GFP_NORETRY flag for obvious reasons,
> and for the __GFP_NOWARN case, however, it is changed such that the caller passes the
> flag instead of making bucket_table_alloc() handle it.
> 
> This slightly changes the gfp flags passed on to nested_table_alloc() as it will now
> also use GFP_ATOMIC | __GFP_NOWARN. However, I consider this a positive consequence
> as for the same reasons we want nowarn semantics in bucket_table_alloc().
> 
> Signed-off-by: Davidlohr Bueso <dbueso@...e.de>

Acked-by: Michal Hocko <mhocko@...e.com>

> ---
> 
> v2:
> - Changes based on Neil's concerns about keeping nowarn flag.
> - Better changelog.
> 
> 
> lib/rhashtable.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/rhashtable.c b/lib/rhashtable.c
> index 9427b5766134..083f871491a1 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;
> 
> @@ -459,7 +456,7 @@ static int rhashtable_insert_rehash(struct rhashtable *ht,
> 
> 	err = -ENOMEM;
> 
> -	new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC);
> +	new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC | __GFP_NOWARN);
> 	if (new_tbl == NULL)
> 		goto fail;
> 
> -- 
> 2.16.4

-- 
Michal Hocko
SUSE Labs