From 0f5d050ceaa31b2229102211d60c149f920df3aa Mon Sep 17 00:00:00 2001 From: Sebastian Ott Date: Tue, 12 Jul 2016 19:57:57 +0200 Subject: s390/cio: allow to reset channel measurement block Prior to commit 1bc6664bdfb949bc69a08113801e7d6acbf6bc3f a call to enable_cmf for a device for which channel measurement was already enabled resulted in a reset of the measurement data. What looked like bugs at the time (a 2nd allocation was triggered but failed, reset was called regardless of previous failures, and errors have not been reported to userspace) was actually something at least one userspace tool depended on. Restore that behavior in a sane way. Fixes: 1bc6664bdfb ("s390/cio: use device_lock during cmb activation") Cc: stable@vger.kernel.org #v4.4+ Signed-off-by: Sebastian Ott Reviewed-by: Cornelia Huck Reviewed-by: Peter Oberparleiter Signed-off-by: Martin Schwidefsky --- drivers/s390/cio/cmf.c | 29 ++++++++++++++++++++--------- 1 file changed, 20 insertions(+), 9 deletions(-) (limited to 'drivers/s390') diff --git a/drivers/s390/cio/cmf.c b/drivers/s390/cio/cmf.c index f18c83bacb09..268aa23afa01 100644 --- a/drivers/s390/cio/cmf.c +++ b/drivers/s390/cio/cmf.c @@ -756,6 +756,17 @@ static void reset_cmb(struct ccw_device *cdev) cmf_generic_reset(cdev); } +static int cmf_enabled(struct ccw_device *cdev) +{ + int enabled; + + spin_lock_irq(cdev->ccwlock); + enabled = !!cdev->private->cmb; + spin_unlock_irq(cdev->ccwlock); + + return enabled; +} + static struct attribute_group cmf_attr_group; static struct cmb_operations cmbops_basic = { @@ -1156,13 +1167,8 @@ static ssize_t cmb_enable_show(struct device *dev, char *buf) { struct ccw_device *cdev = to_ccwdev(dev); - int enabled; - spin_lock_irq(cdev->ccwlock); - enabled = !!cdev->private->cmb; - spin_unlock_irq(cdev->ccwlock); - - return sprintf(buf, "%d\n", enabled); + return sprintf(buf, "%d\n", cmf_enabled(cdev)); } static ssize_t cmb_enable_store(struct device *dev, @@ -1202,15 +1208,20 @@ int ccw_set_cmf(struct ccw_device *cdev, int enable) * @cdev: The ccw device to be enabled * * Returns %0 for success or a negative error value. - * + * Note: If this is called on a device for which channel measurement is already + * enabled a reset of the measurement data is triggered. * Context: * non-atomic */ int enable_cmf(struct ccw_device *cdev) { - int ret; + int ret = 0; device_lock(&cdev->dev); + if (cmf_enabled(cdev)) { + cmbops->reset(cdev); + goto out_unlock; + } get_device(&cdev->dev); ret = cmbops->alloc(cdev); if (ret) @@ -1229,7 +1240,7 @@ int enable_cmf(struct ccw_device *cdev) out: if (ret) put_device(&cdev->dev); - +out_unlock: device_unlock(&cdev->dev); return ret; } -- cgit v1.2.3