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authorEric Dumazet <edumazet@google.com>2014-10-10 04:48:15 -0700
committerDavid S. Miller <davem@davemloft.net>2014-10-10 15:37:28 -0400
commit00cd5adb0313f540aa58672d14e764d164586a43 (patch)
treebdeeb422a5a8627d6da8a42499aeec2340cef437
parent42b0270b40e2ad692ef59e28233202ee6f293e1e (diff)
igb: 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: Eric Dumazet <edumazet@google.com> Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--drivers/net/ethernet/intel/igb/igb_main.c7
1 files changed, 3 insertions, 4 deletions
diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index ae59c0b108c5..a21b14495ebd 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -6545,11 +6545,10 @@ static bool igb_can_reuse_rx_page(struct igb_rx_buffer *rx_buffer,
/* flip page offset to other buffer */
rx_buffer->page_offset ^= IGB_RX_BUFSZ;
- /* 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 unnecessary 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;