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mlx4: fix race accessing page->_count 

This is illegal to use atomic_set(&page->_count, ...) even if we 'own'
the page. Other entities in the kernel need to use get_page_unless_zero()
to get a reference to the page before testing page properties, so we could
loose a refcount increment.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2014-10-10 04:48:17 -07:00 committed by David S. Miller
parent ec91698360
commit 98226208c8
1 changed files with 3 additions and 3 deletions
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6
drivers/net/ethernet/mellanox/mlx4/en_rx.c
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@ -76,10 +76,10 @@ static int mlx4_alloc_pages(struct mlx4_en_priv *priv,
page_alloc->dma = dma;
page_alloc->page_offset = frag_info->frag_align;
/* Not doing get_page() for each frag is a big win
* on asymetric workloads.
* on asymetric workloads. Note we can not use atomic_set().
*/
atomic_set(&page->_count,
page_alloc->page_size / frag_info->frag_stride);
atomic_add(page_alloc->page_size / frag_info->frag_stride - 1,
&page->_count);
return 0;
}