[PATCH net 2/4] sfc: take correct lock in ef100_reset()

[Edward Cree]

When downing and upping the ef100 filter table, we need to take a write
 lock on efx->filter_sem, not just a read lock, because we may kfree()
 the table pointers.
Without this, resets cause a WARN_ON from efx_rwsem_assert_write_locked().

Fixes: a9dc3d5612ce ("sfc_ef100: RX filter table management and related 
gubbins")
Signed-off-by: Edward Cree <ec...@solarflare.com>
---
 drivers/net/ethernet/sfc/ef100_nic.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/sfc/ef100_nic.c 
b/drivers/net/ethernet/sfc/ef100_nic.c
index b8a7e9ed7913..19fe86b3b316 100644
--- a/drivers/net/ethernet/sfc/ef100_nic.c
+++ b/drivers/net/ethernet/sfc/ef100_nic.c
@@ -431,18 +431,18 @@ static int ef100_reset(struct efx_nic *efx, enum 
reset_type reset_type)
                /* A RESET_TYPE_ALL will cause filters to be removed, so we 
remove filters
                 * and reprobe after reset to avoid removing filters twice
                 */
-               down_read(&efx->filter_sem);
+               down_write(&efx->filter_sem);
                ef100_filter_table_down(efx);
-               up_read(&efx->filter_sem);
+               up_write(&efx->filter_sem);
                rc = efx_mcdi_reset(efx, reset_type);
                if (rc)
                        return rc;
 
                netif_device_attach(efx->net_dev);
 
-               down_read(&efx->filter_sem);
+               down_write(&efx->filter_sem);
                rc = ef100_filter_table_up(efx);
-               up_read(&efx->filter_sem);
+               up_write(&efx->filter_sem);
                if (rc)
                        return rc;