linux-kernel - Re: [PATCH] mm: introduce kv[mz]alloc helpers

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Message-ID: <20170106151034.GR5556@dhcp22.suse.cz>
Date:   Fri, 6 Jan 2017 16:10:35 +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>, kvm@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-security-module@...r.kernel.org, linux-ext4@...r.kernel.org,
        Joe Perches <joe@...ches.com>,
        Anatoly Stepanov <astepanov@...udlinux.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Theodore Ts'o <tytso@....edu>,
        Andreas Dilger <adilger@...ger.ca>
Subject: Re: [PATCH] mm: introduce kv[mz]alloc helpers

On Fri 06-01-17 15:36:04, Vlastimil Babka wrote:
> On 01/04/2017 03:20 PM, Michal Hocko wrote:
> > diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
> > index 2ff499680cc6..0a5cc1237afe 100644
> > --- a/net/netfilter/x_tables.c
> > +++ b/net/netfilter/x_tables.c
> > @@ -712,17 +712,8 @@ EXPORT_SYMBOL(xt_check_entry_offsets);
> >   */
> >  unsigned int *xt_alloc_entry_offsets(unsigned int size)
> >  {
> > -	unsigned int *off;
> > +	return kvmalloc(size * sizeof(unsigned int), GFP_KERNEL);;
> >  
> > -	off = kcalloc(size, sizeof(unsigned int), GFP_KERNEL | __GFP_NOWARN);
> > -
> > -	if (off)
> > -		return off;
> > -
> > -	if (size < (SIZE_MAX / sizeof(unsigned int)))
> > -		off = vmalloc(size * sizeof(unsigned int));
> > -
> > -	return off;
> 
> This one seems to have tried hard to avoid the multiplication overflow
> by using kcalloc() and doing the size check before vmalloc(), so I
> wonder if it's safe to just remove the checks completely?

Tetsuo has already pointed that out and it is fixed in my loacal
version.
 
> >  }
> >  EXPORT_SYMBOL(xt_alloc_entry_offsets);
> >  
> > diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
> > index 86309a3156a5..5678eff40f61 100644
> > --- a/net/sched/sch_fq.c
> > +++ b/net/sched/sch_fq.c
> > @@ -624,16 +624,6 @@ static void fq_rehash(struct fq_sched_data *q,
> >  	q->stat_gc_flows += fcnt;
> >  }
> >  
> > -static void *fq_alloc_node(size_t sz, int node)
> > -{
> > -	void *ptr;
> > -
> > -	ptr = kmalloc_node(sz, GFP_KERNEL | __GFP_REPEAT | __GFP_NOWARN, node);
> 
> Another patch 3 material?

I will just drop this part for now. c3bd85495aef6 doesn't say a word about why
it needs __GFP_REPEAT. I will ask Eric.
 
> > -	if (!ptr)
> > -		ptr = vmalloc_node(sz, node);
> > -	return ptr;
> > -}
> > -
> >  static void fq_free(void *addr)
> >  {
> >  	kvfree(addr);
> > @@ -650,7 +640,7 @@ static int fq_resize(struct Qdisc *sch, u32 log)
> >  		return 0;
> >  
> >  	/* If XPS was setup, we can allocate memory on right NUMA node */
> > -	array = fq_alloc_node(sizeof(struct rb_root) << log,
> > +	array = kvmalloc_node(sizeof(struct rb_root) << log, GFP_KERNEL,
> >  			      netdev_queue_numa_node_read(sch->dev_queue));
> >  	if (!array)
> >  		return -ENOMEM;
> 
> With that fixed,
> 
> Acked-by: Vlastimil Babka <vbabka@...e.cz>

Thanks!

-- 
Michal Hocko
SUSE Labs