Nick Piggin wrote:
>
> --- linux-2.6.orig/mm/vmscan.c
> +++ linux-2.6/mm/vmscan.c
> @@ -380,6 +380,8 @@ int remove_mapping(struct address_space
> if (!mapping)
> return 0; /* truncate got there first */
>
> + SetPageNoNewRefs(page);
> + smp_wmb();
> write_lock_irq(&mapping->tree_lock);
>
Is it enough?
PG_nonewrefs could be already set by another add_to_page_cache()/remove_mapping(),
and it will be cleared when we take ->tree_lock. For example:
CPU_0 CPU_1 CPU_3
add_to_page_cache:
SetPageNoNewRefs();
write_lock_irq(->tree_lock);
...
write_unlock_irq(->tree_lock);
remove_mapping:
SetPageNoNewRefs();
ClearPageNoNewRefs();
write_lock_irq(->tree_lock);
check page_count()
page_cache_get_speculative:
increment page_count()
no PG_nonewrefs => return
Oleg.
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