linux-kernel - Re: [PATCH 4/4] kmemcheck v4

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Date:	Thu, 14 Feb 2008 21:31:30 +0100
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	"Pekka Enberg" <penberg@...helsinki.fi>
Cc:	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"Daniel Walker" <dwalker@...sta.com>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Richard Knutsson" <ricknu-0@...dent.ltu.se>,
	"Andi Kleen" <andi@...stfloor.org>,
	"Christoph Lameter" <clameter@....com>
Subject: Re: [PATCH 4/4] kmemcheck v4

On 2/14/08, Pekka Enberg <penberg@...helsinki.fi> wrote:
> Hi,
>
>
>  Vegard Nossum wrote:
>  > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
>  > index 412672a..7bdb37f 100644
>  > --- a/include/linux/skbuff.h
>  > +++ b/include/linux/skbuff.h
>  > @@ -1294,7 +1294,11 @@ static inline void __skb_queue_purge(struct
>  > sk_buff_head *list)
>  >  static inline struct sk_buff *__dev_alloc_skb(unsigned int length,
>  >                            gfp_t gfp_mask)
>  >  {
>  > -    struct sk_buff *skb = alloc_skb(length + NET_SKB_PAD, gfp_mask);
>  > +    struct sk_buff *skb;
>  > +#ifdef CONFIG_KMEMCHECK
>  > +    gfp_mask |= __GFP_ZERO;
>  > +#endif
>
>
> Use __GFP_NOTRACK here (no need to wrap it in CONFIG_KMEMCHECK either).
>
>  > +    skb = alloc_skb(length + NET_SKB_PAD, gfp_mask);
>
> >      if (likely(skb))
>  >          skb_reserve(skb, NET_SKB_PAD);
>  >      return skb;
>
>
> > diff --git a/init/do_mounts.c b/init/do_mounts.c
>  > index f865731..87b1b0f 100644
>  > --- a/init/do_mounts.c
>  > +++ b/init/do_mounts.c
>  > @@ -201,9 +201,13 @@ static int __init do_mount_root(char *name, char
>  > *fs, int flags, void *data)
>  >      return 0;
>  >  }
>  >
>  > +#if PAGE_SIZE < PATH_MAX
>  > +# error increase the fs_names allocation size here
>  > +#endif
>  > +
>  >  void __init mount_block_root(char *name, int flags)
>  >  {
>  > -    char *fs_names = __getname();
>  > +    char *fs_names = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
>  >      char *p;
>  >  #ifdef CONFIG_BLOCK
>  >      char b[BDEVNAME_SIZE];
>  > @@ -251,7 +255,7 @@ retry:
>  >  #endif
>  >      panic("VFS: Unable to mount root fs on %s", b);
>  >  out:
>  > -    putname(fs_names);
>  > +    free_pages((unsigned long)fs_names, 1);
>
>
> As discussed before, I don't think kmemcheck should be complaining about
>  this (even though this is a potential bug). Have you tried with the
>  current patches to see if it still triggers? Could have been one of the
>  kmemcheck bugs, no?
>
>
>  > @@ -255,6 +258,9 @@ struct sk_buff *__netdev_alloc_skb(struct net_device
>  > *dev,
>  >      int node = dev->dev.parent ? dev_to_node(dev->dev.parent) : -1;
>  >      struct sk_buff *skb;
>  >
>  > +#ifdef CONFIG_KMEMCHECK
>  > +    gfp_mask |= __GFP_ZERO;
>  > +#endif
>
>
> __GFP_NOTRACK here
>
>
>                         Pekka
>

Will fix those, thanks!


Vegard
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