s390/dasd: print copy pair message only for the correct error

s390/dasd: print copy pair message only for the correct error

The DASD driver has certain types of requests that might be rejected by
the storage server or z/VM because they are not supported. Since the
missing support of the command is not a real issue there is no user
visible kernel error message for this.

For copy pair setups  there is a specific error that IO is not allowed on
secondary devices. This error case is explicitly handled and an error
message is printed.

The code checking for the error did use a bitwise 'and' that is used to
check for specific bits. But in this case the whole sense byte has to
match.

This leads to the problem that the copy pair related error message is
erroneously printed for other error cases that are usually not reported.
This might heavily confuse users and lead to follow on actions that might
disrupt application processing.

Fix by checking the sense byte for the exact value and not single bits.

Cc: stable@vger.kernel.org # 6.1+
Fixes: 1fca631a1185 ("s390/dasd: suppress generic error messages for PPRC secondary devices")
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Reviewed-by: Jan Hoeppner <hoeppner@linux.ibm.com>
Link: https://lore.kernel.org/r/20230721193647.3889634-5-sth@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>