linux-kernel - Re: [PATCH 8/9] bcache: use kvmalloc

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Message-ID: <28e7a4de-6940-5626-d382-1381640d58f0@suse.cz>
Date:   Mon, 30 Jan 2017 17:47:31 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Michal Hocko <mhocko@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     David Rientjes <rientjes@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Johannes Weiner <hannes@...xchg.org>,
        Al Viro <viro@...iv.linux.org.uk>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>,
        Kent Overstreet <kent.overstreet@...il.com>
Subject: Re: [PATCH 8/9] bcache: use kvmalloc

On 01/30/2017 10:49 AM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@...e.com>
>
> bcache_device_init uses kmalloc for small requests and vmalloc for those
> which are larger than 64 pages. This alone is a strange criterion.
> Moreover kmalloc can fallback to vmalloc on the failure. Let's simply
> use kvmalloc instead as it knows how to handle the fallback properly

I don't see why separate patch, some of the conversions in 5/9 were quite 
similar (except comparing with PAGE_SIZE, not 64*PAGE_SIZE), but nevermind.

> Cc: Kent Overstreet <kent.overstreet@...il.com>
> Signed-off-by: Michal Hocko <mhocko@...e.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  drivers/md/bcache/super.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> index 3a19cbc8b230..4cb6b88a1465 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -767,16 +767,12 @@ static int bcache_device_init(struct bcache_device *d, unsigned block_size,
>  	}
>
>  	n = d->nr_stripes * sizeof(atomic_t);
> -	d->stripe_sectors_dirty = n < PAGE_SIZE << 6
> -		? kzalloc(n, GFP_KERNEL)
> -		: vzalloc(n);
> +	d->stripe_sectors_dirty = kvzalloc(n, GFP_KERNEL);
>  	if (!d->stripe_sectors_dirty)
>  		return -ENOMEM;
>
>  	n = BITS_TO_LONGS(d->nr_stripes) * sizeof(unsigned long);
> -	d->full_dirty_stripes = n < PAGE_SIZE << 6
> -		? kzalloc(n, GFP_KERNEL)
> -		: vzalloc(n);
> +	d->full_dirty_stripes = kvzalloc(n, GFP_KERNEL);
>  	if (!d->full_dirty_stripes)
>  		return -ENOMEM;
>
>