skip tests if scsi_debug module is already loaded and in use

Several tests across block/, scsi/, dm/, md/, zbd/, nvme/ require
exclusive access to the scsi_debug module because they load, unload or
reconfigure it. When scsi_debug is loadable and already loaded by the
environment (e.g., by another driver or a previous setup), these tests
fail with:

  modprobe: FATAL: Module scsi_debug is in use.
  Unloading scsi_debug failed

  scsi_debug            327680  4

To prevent the failures, check if scsi_debug already loaded. If so, skip
the test cases which use scsi_debug. Instead of modifying common rc
files—which would overskip unrelated tests, add "_module_not_in_use
scsi_debug" call to the new helper function _have_loadable_scsi_debug()
and call it only for the tests that actually depend on exclusive access
to scsi_debug.

Also, when scsi_debug is built-in and already additional hosts are
created by the environment, the tests may break the hosts. To cover this
built-in scsi_debug scenario, check the number of added hosts in
_have_scsi_debug(). If the number of hosts is larger than 1, skip the
test cases.

Link: linux-blktests#218
Signed-off-by: Disha Goel <[email protected]>
[Shin'ichiro: improved commit message]
Signed-off-by: Shin'ichiro Kawasaki <[email protected]>

Author: disgoel

common/scsi_debug

@@ -4,12 +4,32 @@
 #
 # scsi_debug helper functions.
 
+SD_PARAM_PATH=/sys/module/scsi_debug/parameters
+SD_PSEUDO_PATH=/sys/bus/pseudo/drivers/scsi_debug
+
 _have_scsi_debug() {
 	_have_driver scsi_debug
+
+	if _module_file_exists scsi_debug; then
+		_have_loadable_scsi_debug
+		return $?
+	fi
+
+	if [[ -e "$SD_PSEUDO_PATH/add_host" ]] && \
+		[[ $(cat "$SD_PSEUDO_PATH/add_host") -gt 1 ]]; then
+			SKIP_REASONS+=("scsi_debug already has multiple hosts configured")
+		return 1
+	fi
 }
 
-SD_PARAM_PATH=/sys/module/scsi_debug/parameters
-SD_PSEUDO_PATH=/sys/bus/pseudo/drivers/scsi_debug
+_have_loadable_scsi_debug() {
+	_have_module scsi_debug || return 1
+
+	if ! _module_not_in_use scsi_debug; then
+		SKIP_REASONS+=("scsi_debug is already loaded before test")
+		return 1
+	fi
+}
 
 _scsi_debug_key_path() {
 	local key=${1}

tests/block/009

@@ -12,7 +12,7 @@
 DESCRIPTION="check page-cache coherency after BLKDISCARD"
 
 requires() {
-	_have_module scsi_debug
+	_have_loadable_scsi_debug
 	_have_program xfs_io
 }
 

tests/block/025

@@ -12,7 +12,7 @@
 DESCRIPTION="do a huge discard with 4k sector size"
 
 requires() {
-	_have_module scsi_debug
+	_have_loadable_scsi_debug
 }
 
 test() {

tests/block/028

@@ -12,7 +12,7 @@ DESCRIPTION="do I/O on scsi_debug with DIF/DIX enabled"
 DMESG_FILTER="sed -r 's/(guard tag error at sector|ref tag error at location)/blktests failure: \\1/'"
 
 requires() {
-	_have_module scsi_debug
+	_have_loadable_scsi_debug
 }
 
 test_pi() {

tests/block/032

@@ -14,7 +14,7 @@ QUICK=1
 
 requires() {
 	_have_xfs
-	_have_module scsi_debug
+	_have_loadable_scsi_debug
 }
 
 test() {

tests/loop/004

@@ -12,7 +12,7 @@ QUICK=1
 
 requires() {
 	_have_program xfs_io
-	_have_module scsi_debug
+	_have_loadable_scsi_debug
 	_have_src_program loblksize
 	_have_loop_set_block_size
 }

tests/md/002

@@ -12,7 +12,7 @@ DESCRIPTION="test md atomic writes"
 QUICK=1
 
 requires() {
-	_have_driver scsi_debug
+	_have_scsi_debug
 	_stacked_atomic_test_requires
 }
 

tests/scsi/007

@@ -12,7 +12,7 @@ DESCRIPTION="Trigger the SCSI error handler"
 QUICK=1
 
 requires() {
-	_have_module scsi_debug
+	_have_loadable_scsi_debug
 }
 
 start_tracing() {

tests/scsi/009

@@ -12,7 +12,7 @@ DESCRIPTION="test scsi atomic writes"
 QUICK=1
 
 requires() {
-	_have_driver scsi_debug
+	_have_scsi_debug
 	_have_xfs_io_atomic_write
 }
 

tests/zbd/008

@@ -13,7 +13,7 @@ DESCRIPTION="check no stale page cache after BLKZONERESET and data read race"
 TIMED=1
 
 requires() {
-	_have_module scsi_debug
+	_have_loadable_scsi_debug
 	_have_module_param scsi_debug zbc
 	_have_program xfs_io
 }