Re: Fwd: [PATCH] Pageset Localization V2

[shobhit dayal <shobhit@calsoftinc.com>]

The goal here is to replace the head of a existing list pointed to by
'list' with a new head pointed to by 'nlist'. 
First there is a memcpy that copies the contents of list to nlist then
this macro is called.
The macro makes sure that if the old head was empty then INIT_LIST_HEAD
the 'nlist', if not then make sure that the nodes before and after the
head now correclty point to nlist instead of list.

regards
shobhit


> ---------- Forwarded message ----------
> From: Christoph Hellwig <hch@infradead.org>
> Date: Wed, 30 Mar 2005 12:14:39 +0100
> Subject: Re: [PATCH] Pageset Localization V2
> To: Christoph Lameter <christoph@lameter.com>
> Cc: Manfred Spraul <manfred@colorfullife.com>, Andrew Morton
> <akpm@osdl.org>, linux-kernel@vger.kernel.org,
> linux-ia64@vger.kernel.org, linux-mm@kvack.org, shai@scalex86.org
> 
> 
> > +#define MAKE_LIST(list, nlist)  \
> > +     do {    \
> > +             if(list_empty(&list))      \
> > +                     INIT_LIST_HEAD(nlist);          \
> > +             else {  nlist->next->prev = nlist;      \
> > +                     nlist->prev->next = nlist;      \
> > +             }                                       \
> > +     }while(0)
> 
> This is horrible.  Where are the nlist pointers supposed to point to?
> What's so magic you need the INIT_LIST_HEAD only conditionally?
> 
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