Re: [PATCH 7/9] mm: split page table lock

[Hugh Dickins]

On Sun, 23 Oct 2005, Andrew Morton wrote:
> Hugh Dickins <hugh@xxxxxxxxxxx> wrote:
> >  + * When freeing, reset page->mapping so free_pages_check won't complain.
> >  + */
> >  +#define __pte_lockptr(page)	((spinlock_t *)&((page)->private))
> >  +#define pte_lock_init(_page)	do {					\
> >  +	BUILD_BUG_ON((size_t)(__pte_lockptr((struct page *)0) + 1) >	\
> >  +						sizeof(struct page));	\
> >  +	spin_lock_init(__pte_lockptr(_page));				\
> >  +} while (0)
> >  +#define pte_lock_deinit(page)	((page)->mapping = NULL)
> >  +#define pte_lockptr(mm, pmd)	({(void)(mm); __pte_lockptr(pmd_page(*(pmd)));})
> >  +#else
> 
> Why does pte_lock_deinit() zap ->mapping?  That doesn't seem to have
> anything to do with anything?

Nick had wondered the same originally, so I did add the comment above.
Bring it down to immediately above the deinit line if you prefer.

Hugh
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