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SubjectRe: Race in shrink_cache
Daniel Phillips wrote:
>
> Hi Marcelo,
>
> This looks really suspicious, vmscan.c#435:
>
> spin_unlock(&pagemap_lru_lock);
> if (put_page_testzero(page))
> __free_pages_ok(page, 0);
> /* avoid to free a locked page */
> page_cache_get(page);
>
> /* whoops, double free coming */
>
> I suggest you bump the page count before releasing the lru lock. The race
> shown above may not in fact be possible, but the current code is fragile.
>

That's OK. The page has a ref because of nonzero ->buffers And it
is locked, which pins page->buffers.
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