@@ -121,6 +121,10 @@ Preparing system for tests:
filesystem we can create. Setting this parameter will
skip the tests creating a filesystem less than
MIN_FSSIZE.
+ - Set MODPROBE_PATIENT_RM_TIMEOUT_SECONDS to specify the amount of
+ time we should try a patient module remove. The default is 50
+ seconds. Set this to "forever" and we'll wait forever until the
+ module is gone.
- or add a case to the switch in common/config assigning
these variables based on the hostname of your test
@@ -252,6 +252,37 @@ if [[ "$UDEV_SETTLE_PROG" == "" || ! -d /proc/net ]]; then
fi
export UDEV_SETTLE_PROG
+# Set MODPROBE_PATIENT_RM_TIMEOUT_SECONDS to "forever" if you want the patient
+# modprobe removal to run forever trying to remove a module.
+MODPROBE_REMOVE_PATIENT=""
+modprobe --help | grep -q -1 "remove-patiently"
+if [[ $? -ne 0 ]]; then
+ if [[ -z "$MODPROBE_PATIENT_RM_TIMEOUT_SECONDS" ]]; then
+ # We will open code our own implementation of patient module
+ # remover in fstests. Use a 50 second default.
+ export MODPROBE_PATIENT_RM_TIMEOUT_SECONDS="50"
+ fi
+else
+ MODPROBE_RM_PATIENT_TIMEOUT_ARGS=""
+ if [[ ! -z "$MODPROBE_PATIENT_RM_TIMEOUT_SECONDS" ]]; then
+ if [[ "$MODPROBE_PATIENT_RM_TIMEOUT_SECONDS" != "forever" ]]; then
+ MODPROBE_PATIENT_RM_TIMEOUT_MS="$((MODPROBE_PATIENT_RM_TIMEOUT_SECONDS * 1000))"
+ MODPROBE_RM_PATIENT_TIMEOUT_ARGS="-t $MODPROBE_PATIENT_RM_TIMEOUT_MS"
+ fi
+ else
+ # We export MODPROBE_PATIENT_RM_TIMEOUT_SECONDS here for parity
+ # with environments without support for modprobe -p, but we
+ # only really need it exported right now for environments which
+ # don't have support for modprobe -p to implement our own
+ # patient module removal support within fstests.
+ export MODPROBE_PATIENT_RM_TIMEOUT_SECONDS="50"
+ MODPROBE_PATIENT_RM_TIMEOUT_MS="$((MODPROBE_PATIENT_RM_TIMEOUT_SECONDS * 1000))"
+ MODPROBE_RM_PATIENT_TIMEOUT_ARGS="-t $MODPROBE_PATIENT_RM_TIMEOUT_MS"
+ fi
+ MODPROBE_REMOVE_PATIENT="modprobe -p $MODPROBE_RM_TIMEOUT_ARGS"
+fi
+export MODPROBE_REMOVE_PATIENT
+
export MKFS_XFS_PROG=$(type -P mkfs.xfs)
export MKFS_EXT4_PROG=$(type -P mkfs.ext4)
export MKFS_UDF_PROG=$(type -P mkudffs)
@@ -81,3 +81,111 @@ _get_fs_module_param()
{
cat /sys/module/${FSTYP}/parameters/${1} 2>/dev/null
}
+
+# checks the refcount and returns 0 if we can safely remove the module. rmmod
+# does this check for us, but we can use this to also iterate checking for this
+# refcount before we even try to remove the module. This is useful when using
+# debug test modules which take a while to quiesce.
+_patient_rmmod_check_refcnt()
+{
+ local module=$1
+ local refcnt=0
+
+ if [[ -f /sys/module/$module/refcnt ]]; then
+ refcnt=$(cat /sys/module/$module/refcnt 2>/dev/null)
+ if [[ $? -ne 0 || $refcnt -eq 0 ]]; then
+ return 0
+ fi
+ return 1
+ fi
+ return 0
+}
+
+# Patiently tries to wait to remove a module by ensuring first
+# the refcnt is 0 and then trying to persistently remove the module within
+# the time allowed. The timeout is configurable per test, just set
+# MODPROBE_PATIENT_RM_TIMEOUT_SECONDS prior to including this file.
+# If you want this to try forever just set MODPROBE_PATIENT_RM_TIMEOUT_SECONDS
+# to the special value of "forever". This applies to both cases where kmod
+# supports the patient module remover (modrobe -p) and where it does not.
+#
+# If your version of kmod supports modprobe -p, we instead use that
+# instead. Otherwise we have to implement a patient module remover
+# ourselves.
+_patient_rmmod()
+{
+ local module=$1
+ local max_tries_max=$MODPROBE_PATIENT_RM_TIMEOUT_SECONDS
+ local max_tries=0
+ local mod_ret=0
+ local refcnt_is_zero=0
+
+ if [[ ! -z $MODPROBE_REMOVE_PATIENT ]]; then
+ $MODPROBE_REMOVE_PATIENT $module
+ mod_ret=$?
+ if [[ $mod_ret -ne 0 ]]; then
+ echo "kmod patient module removal for $module timed out waiting for refcnt to become 0 using timeout of $max_tries_max returned $mod_ret"
+ fi
+ return $mod_ret
+ fi
+
+ max_tries=$max_tries_max
+
+ # We must use a string check as otherwise if max_tries is set to
+ # "forever" and we don't use a string check we can end up skipping
+ # entering this loop.
+ while [[ "$max_tries" != "0" ]]; do
+ _patient_rmmod_check_refcnt $module
+ if [[ $? -eq 0 ]]; then
+ refcnt_is_zero=1
+ break
+ fi
+ sleep 1
+ if [[ "$max_tries" == "forever" ]]; then
+ continue
+ fi
+ let max_tries=$max_tries-1
+ done
+
+ if [[ $refcnt_is_zero -ne 1 ]]; then
+ echo "custom patient module removal for $module timed out waiting for refcnt to become 0 using timeout of $max_tries_max"
+ return -1
+ fi
+
+ # If we ran out of time but our refcnt check confirms we had
+ # a refcnt of 0, just try to remove the module once.
+ if [[ "$max_tries" == "0" ]]; then
+ modprobe -r $module
+ return $?
+ fi
+
+ # If we have extra time left. Use the time left to now try to
+ # persistently remove the module. We do this because although through
+ # the above we found refcnt to be 0, removal can still fail since
+ # userspace can always race to bump the refcnt. An example is any
+ # blkdev_open() calls against a block device. These issues have been
+ # tracked and documented in the following bug reports, which justifies
+ # our need to do this in userspace:
+ # https://bugzilla.kernel.org/show_bug.cgi?id=212337
+ # https://bugzilla.kernel.org/show_bug.cgi?id=214015
+ while [[ $max_tries != 0 ]]; do
+ if [[ -d /sys/module/$module ]]; then
+ modprobe -r $module 2> /dev/null
+ mod_ret=$?
+ if [[ $mod_ret == 0 ]]; then
+ break;
+ fi
+ sleep 1
+ if [[ "$max_tries" == "forever" ]]; then
+ continue
+ fi
+ let max_tries=$max_tries-1
+ fi
+ done
+
+ if [[ $mod_ret -ne 0 ]]; then
+ echo "custom patient module removal for $module timed out trying to remove $module using timeout of $max_tries_max last try returned $mod_ret"
+ fi
+
+ return $mod_ret
+}
When we call rmmod it will fail if the refcnt is greater than 0. This is expected, however, if using test modules such as scsi_debug, userspace tests may expect that once userspace is done issuing out commands it can safely remove the module, and the module will be removed. This is not true for few reasons. First, a module might take a while to quiesce after its used. This varies module by module. For example, at least for scsi_debug there is one patch to help with this but that is not sufficient to address all the removal issues, it just helps quiesce the module faster. If something like LVM pvremove is used, as in the case of generic/108, it may take time before the module's refcnt goes to 0 even if DM_DEFERRED_REMOVE is *not* used and even if udevadm settle is used. Even *after* all this... the module refcnt is still very fickle. For example, any blkdev_open() against a block device will bump a module refcnt up and we have little control over stopping these sporadic userspace calls after a test. A failure on module removal then just becomes an inconvenience on false positives. This was first observed on scsi_debug [0]. Doug worked on a patch to help the driver quiesce [1]. Later the issue has been determined to be generic [2]. The only way to properly resolve these issues is with a patient module remover. The kernel used to support a wait for the delete_module() system call, however this was later deprecated into kmod with a 10 second userspace sleep. That 10 second sleep is long gone from kmod now though. I've posted patches now for a kmod patient module remover then [3], in light of the fact that this issue is generic and the only way to then properly deal with this is implementing a userspace patient module remover. Use the kmod patient module remover when supported, otherwise we open code our own solution inside fstests. We default to a timeout of 100 seconds. Each test can override the timeout by setting the variable MODPROBE_PATIENT_RM_TIMEOUT_SECONDS or setting it to "forever" if they wish for the patience to be infinite. This uses kmod's patient module remover if you have that feature, otherwise we open code a solution in fstests which is a simplified version of what has been proposed for kmod. [0] https://bugzilla.kernel.org/show_bug.cgi?id=212337 [1] https://lore.kernel.org/linux-scsi/20210508230745.27923-1-dgilbert@interlog.com/ [2] https://bugzilla.kernel.org/show_bug.cgi?id=214015 [3] https://lkml.kernel.org/r/20210810051602.3067384-1-mcgrof@kernel.org Signed-off-by: Luis Chamberlain <mcgrof@kernel.org> --- README | 4 ++ common/config | 31 +++++++++++++++ common/module | 108 ++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 143 insertions(+)