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Commit ec916983 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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ixgbe: fix race accessing page->_count 



This is illegal to use atomic_set(&page->_count, 2) 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: default avatarEric Dumazet <edumazet@google.com>
Acked-by: default avatarJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 00cd5adb

drivers/net/ethernet/intel/ixgbe/ixgbe_main.c

+3 −5
Original line number Diff line number Diff line
@@ -1865,12 +1865,10 @@ static bool ixgbe_add_rx_frag(struct ixgbe_ring *rx_ring, 
	/* flip page offset to other buffer */

	rx_buffer->page_offset ^= truesize;



	/*

	 * since we are the only owner of the page and we need to

	 * increment it, just set the value to 2 in order to avoid

	 * an unecessary locked operation

	/* Even if we own the page, we are not allowed to use atomic_set()

	 * This would break get_page_unless_zero() users.

	 */

	atomic_set(&page->_count, 2);

	atomic_inc(&page->_count);

#else

	/* move offset up to the next cache line */

	rx_buffer->page_offset += truesize;