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s390/dasd/cio: Interpret ccw_device_get_mdc return value correctly 

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>
alistair/sunxi64-5.5-dsi
Jan Höppner 2019-12-19 09:43:50 +01:00 committed by Jens Axboe
parent b3c6a59975
commit dd4b3c83b9
2 changed files with 6 additions and 5 deletions
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9
drivers/s390/block/dasd_eckd.c
View File

@ -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",

2
drivers/s390/cio/device_ops.c
View File

@ -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)
{