4.9-stable review patch. If anyone has any objections, please let me know.
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From: Jakub Kicinski jakub.kicinski@netronome.com
[ Upstream commit 07300f774fec9519663a597987a4083225588be4 ]
After device is stopped we reset the rings by moving all free buffers to positions [0, cnt - 2], and clear the position cnt - 1 in the ring. We then proceed to clear the read/write pointers. This means that if we try to reset the ring again the code will assume that the next to fill buffer is at position 0 and swap it with cnt - 1. Since we previously cleared position cnt - 1 it will lead to leaking the first buffer and leaving ring in a bad state.
This scenario can only happen if FW communication fails, in which case the ring will never be used again, so the fact it's in a bad state will not be noticed. Buffer leak is the only problem. Don't try to move buffers in the ring if the read/write pointers indicate the ring was never used or have already been reset.
nfp_net_clear_config_and_disable() is now fully idempotent.
Found by code inspection, FW communication failures are very rare, and reconfiguring a live device is not common either, so it's unlikely anyone has ever noticed the leak.
Signed-off-by: Jakub Kicinski jakub.kicinski@netronome.com Reviewed-by: Dirk van der Merwe dirk.vandermerwe@netronome.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/ethernet/netronome/nfp/nfp_net_common.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c +++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c @@ -990,7 +990,7 @@ static void nfp_net_tx_complete(struct n * @nn: NFP Net device * @tx_ring: TX ring structure * - * Assumes that the device is stopped + * Assumes that the device is stopped, must be idempotent. */ static void nfp_net_tx_ring_reset(struct nfp_net *nn, struct nfp_net_tx_ring *tx_ring) @@ -1144,13 +1144,18 @@ static void nfp_net_rx_give_one(struct n * nfp_net_rx_ring_reset() - Reflect in SW state of freelist after disable * @rx_ring: RX ring structure * - * Warning: Do *not* call if ring buffers were never put on the FW freelist - * (i.e. device was not enabled)! + * Assumes that the device is stopped, must be idempotent. */ static void nfp_net_rx_ring_reset(struct nfp_net_rx_ring *rx_ring) { unsigned int wr_idx, last_idx;
+ /* wr_p == rd_p means ring was never fed FL bufs. RX rings are always + * kept at cnt - 1 FL bufs. + */ + if (rx_ring->wr_p == 0 && rx_ring->rd_p == 0) + return; + /* Move the empty entry to the end of the list */ wr_idx = rx_ring->wr_p % rx_ring->cnt; last_idx = rx_ring->cnt - 1; @@ -1919,6 +1924,8 @@ static void nfp_net_vec_clear_ring_data( /** * nfp_net_clear_config_and_disable() - Clear control BAR and disable NFP * @nn: NFP Net device to reconfigure + * + * Warning: must be fully idempotent. */ static void nfp_net_clear_config_and_disable(struct nfp_net *nn) {