From: Edward Cree <ecree@solarflare.com>
Date: Tue, 18 Aug 2020 13:43:57 +0100
Subject: sfc: take correct lock in ef100_reset()
Patch-mainline: v5.9-rc2
Git-commit: 9cbbc451098ec1e9942886023203b2247dec94bd
References: jsc#SLE-16683

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 <ecree@solarflare.com>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/sfc/ef100_nic.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- 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 *e
 		/* 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;