From: Jan Höppner hoeppner@linux.ibm.com
[ Upstream commit dd4b3c83b9efac10d48a94c61372119fc555a077 ]
The max data count (mdc) is an unsigned 16-bit integer value as per AR documentation and is received via ccw_device_get_mdc() for a specific path mask from the CIO layer. The function itself also always returns a positive mdc value or 0 in case mdc isn't supported or couldn't be determined.
Though, the comment for this function describes a negative return value to indicate failures.
As a result, the DASD device driver interprets the return value of ccw_device_get_mdc() incorrectly. The error case is essentially a dead code path.
To fix this behaviour, check explicitly for a return value of 0 and change the comment for ccw_device_get_mdc() accordingly.
This fix merely enables the error code path in the DASD functions get_fcx_max_data() and verify_fcx_max_data(). The actual functionality stays the same and is still correct.
Reviewed-by: Cornelia Huck cohuck@redhat.com Signed-off-by: Jan Höppner hoeppner@linux.ibm.com Acked-by: Peter Oberparleiter oberpar@linux.ibm.com Reviewed-by: Stefan Haberland sth@linux.ibm.com Signed-off-by: Stefan Haberland sth@linux.ibm.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/s390/block/dasd_eckd.c | 9 +++++---- drivers/s390/cio/device_ops.c | 2 +- 2 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/drivers/s390/block/dasd_eckd.c b/drivers/s390/block/dasd_eckd.c index c94184d080f8..f5622f4a2ecf 100644 --- a/drivers/s390/block/dasd_eckd.c +++ b/drivers/s390/block/dasd_eckd.c @@ -1128,7 +1128,8 @@ static u32 get_fcx_max_data(struct dasd_device *device) { struct dasd_eckd_private *private = device->private; int fcx_in_css, fcx_in_gneq, fcx_in_features; - int tpm, mdc; + unsigned int mdc; + int tpm;
if (dasd_nofcx) return 0; @@ -1142,7 +1143,7 @@ static u32 get_fcx_max_data(struct dasd_device *device) return 0;
mdc = ccw_device_get_mdc(device->cdev, 0); - if (mdc < 0) { + if (mdc == 0) { dev_warn(&device->cdev->dev, "Detecting the maximum supported data size for zHPF requests failed\n"); return 0; } else { @@ -1153,12 +1154,12 @@ static u32 get_fcx_max_data(struct dasd_device *device) static int verify_fcx_max_data(struct dasd_device *device, __u8 lpm) { struct dasd_eckd_private *private = device->private; - int mdc; + unsigned int mdc; u32 fcx_max_data;
if (private->fcx_max_data) { mdc = ccw_device_get_mdc(device->cdev, lpm); - if ((mdc < 0)) { + if (mdc == 0) { dev_warn(&device->cdev->dev, "Detecting the maximum data size for zHPF " "requests failed (rc=%d) for a new path %x\n", diff --git a/drivers/s390/cio/device_ops.c b/drivers/s390/cio/device_ops.c index 65841af15748..ccecf6b9504e 100644 --- a/drivers/s390/cio/device_ops.c +++ b/drivers/s390/cio/device_ops.c @@ -635,7 +635,7 @@ EXPORT_SYMBOL(ccw_device_tm_start_timeout); * @mask: mask of paths to use * * Return the number of 64K-bytes blocks all paths at least support - * for a transport command. Return values <= 0 indicate failures. + * for a transport command. Return value 0 indicates failure. */ int ccw_device_get_mdc(struct ccw_device *cdev, u8 mask) {