ca34cda73f
css_schedule_reprobe() function calls the evaluation for CSS_EVAL_UNREG which is specific to the idset of unregistered subchannels. This evaluation was introduced because, previously, if the underlying device become not-accessible, the subchannel was unregistered. But, in the recent changes in cio,with the commit '2297791c92d0 s390/cio: dont unregister subchannel from child-drivers', we no longer unregister the subchannels just because of a non-operational device. This allows to have subchannels without any operational device connected on it. So, a css_schedule_reprobe function on unregistered subchannel does not have any effect. Change this functionality to evaluate the subchannels which does not have a working path to the device. This could be due the erroneous device or due to the erraneous path. Evaluate based on the values of OPM and PAM&POM. Here we introduced a new idset function,to keep I/O subchannels in the idset when the last seen status indicates that the device has no working path. A device has no working path if all available paths have been tried without success.A failed I/O attempt on a path is indicated as a 0 bit value in the POM mask. By looking at the POM mask bit values of available paths (1 in PAM) that Linux is supposed to use (1 in vary mask OPM), we can identify a non-working device as a device where the bit-wise and of the PAM, POM and OPM mask return 0. css_schedule_reprobe() is being used by dasd-driver and chsc-cio component. dasd driver, when it detects a change in the pathgroup, invokes the re-evaluation of the subchannel. And chsc-cio component upon a CRW event, (resource accessibility event). In both the cases, it makes much better sense to re-evalute the subchannel with no-valid path. Signed-off-by: Vineeth Vijayan <vneethv@linux.ibm.com> Reported-by: Eric Farman <farman@linux.ibm.com> Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com> Tested-by: Eric Farman <farman@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.