Re: [PATCH] crypto/async_pq: use __free_page() instead of put_page()

[Vlastimil Babka]

On 02/29/2016 10:33 AM, Arnd Bergmann wrote:
> The addition of tracepoints to the page reference tracking had an
> unfortunate side-effect in at least one driver that calls put_page
> from its exit function, resulting in a link error:
> 
> `.exit.text' referenced in section `__jump_table' of crypto/built-in.o: defined in discarded section `.exit.text' of crypto/built-in.o
> 
> From a cursory look at that this driver, it seems that it may be
> doing the wrong thing here anyway, as the page gets allocated
> using 'alloc_page()', and should be freed using '__free_page()'
> rather than 'put_page()'.
> 
> With this patch, I no longer get any other build errors from the
> page_ref patch, so hopefully we can assume that it's always wrong
> to call any of those functions from __exit code, and that no other
> driver does it.

Hopefully that's true. If any such driver was leaking references to
those pages, so the put_page() didn't actually result in freeing, the
explicit __free_page should catch this via built-in checks.

> Fixes: 0f80830dd044 ("mm/page_ref: add tracepoint to track down page reference manipulation")

Since it's in mmotm which is quilt-based, the commit hash from -next is
not stable.

> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

> ---
>  crypto/async_tx/async_pq.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/crypto/async_tx/async_pq.c b/crypto/async_tx/async_pq.c
> index c0748bbd4c08..08b3ac68952b 100644
> --- a/crypto/async_tx/async_pq.c
> +++ b/crypto/async_tx/async_pq.c
> @@ -444,7 +444,7 @@ static int __init async_pq_init(void)
>  
>  static void __exit async_pq_exit(void)
>  {
> -	put_page(pq_scribble_page);
> +	__free_page(pq_scribble_page);
>  }
>  
>  module_init(async_pq_init);
>