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

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Date:   Mon, 30 Jan 2017 18:25:35 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        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>,
        Kent Overstreet <kent.overstreet@...il.com>
Subject: Re: [PATCH 8/9] bcache: use kvmalloc

On Mon 30-01-17 17:47:31, Vlastimil Babka wrote:
> 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.

I just found it later so I kept it separate. It can be folded to 5/9 if
that makes more sense.
 
> > Cc: Kent Overstreet <kent.overstreet@...il.com>
> > Signed-off-by: Michal Hocko <mhocko@...e.com>
> 
> Acked-by: Vlastimil Babka <vbabka@...e.cz>

Thanks!

> > ---
> >  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;
> > 
> > 

-- 
Michal Hocko
SUSE Labs