pkg/subsystem/linux: adjust s390 subsystems

[dvyukov]

Feature request from Heiko Carstens:
https://groups.google.com/g/syzkaller/c/0A_vhmUTaos/m/Rs4uE3upAAAJ

However I would like to propose some changes:

- For the s390 subsystem only Alexander Gordeev is listed as maintainer
(recipient) in syzbot. It would be nice if you could add also Vasily Gorbik
and me:
- Vasily Gorbik <[[email protected]](https://groups.google.com/)>
- Heiko Carstens <[[email protected]](https://groups.google.com/)>

- Furthermore all of the above reports belong to the network SMC subsystem,
which is not s390 specific. Maintainers for SMC (net/smc/) are:
- Wenjia Zhang <[[email protected]](https://groups.google.com/)>
- Jan Karcher <[[email protected]](https://groups.google.com/)>

It might be helpful to add another SMC subsystem with Wenjia and Jan as
maintainers so that the reports reach the correct people.

[a-nogikh]

(it should probably be also duplicated to the email thread, but let's discuss it here first)

We list only one maintainer because of the current logic that merges several MAINTAINERS records into one. We intersect the lists of emails to avoid Cc'ing too many people in each report:

syzkaller/pkg/subsystem/linux/subsystems.go

Lines 233 to 244 in e282667

	// Now let's take the intersection of lists.
	counts := map[string]int{}
	var retList []string
	for _, list := range maintainerLists {
	list = unique(list)
	for _, email := range list {
	counts[email]++
	if counts[email] == len(maintainerLists) {
	retList = append(retList, email)
	}
	}
	}

E.g. for [email protected], there are different people in all related records:

S390 ARCHITECTURE
M:	Heiko Carstens <[email protected]>
M:	Vasily Gorbik <[email protected]>
M:	Alexander Gordeev <[email protected]>
R:	Christian Borntraeger <[email protected]>
R:	Sven Schnelle <[email protected]>
L:	[email protected]

S390 COMMON I/O LAYER
M:	Vineeth Vijayan <[email protected]>
M:	Peter Oberparleiter <[email protected]>
L:	[email protected]

It would be best if we could come up with a less strict yet generic rule to avoid hardcoding the right set of maintainers.

---

It might be helpful to add another SMC subsystem with Wenjia and Jan as
maintainers so that the reports reach the correct people.

That should be straightforward - we only need to add a record to

syzkaller/pkg/subsystem/linux/rules.go

Line 91 in e282667

extraSubsystems: map[string][]string{

[a-nogikh]

For s390, the code snippet from the comment above intersects the maintainer lists because of

S390 ARCHITECTURE
M:	Heiko Carstens <[email protected]>
M:	Vasily Gorbik <[email protected]>
M:	Alexander Gordeev <[email protected]>
R:	Christian Borntraeger <[email protected]>
R:	Sven Schnelle <[email protected]>
L:	[email protected]
S:	Supported
T:	git git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git
F:	Documentation/driver-api/s390-drivers.rst
F:	Documentation/arch/s390/
F:	arch/s390/
F:	drivers/s390/
F:	drivers/watchdog/diag288_wdt.c

S390 MM
M:	Alexander Gordeev <[email protected]>
M:	Gerald Schaefer <[email protected]>
L:	[email protected]
S:	Supported
T:	git git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git
F:	arch/s390/include/asm/pgtable.h
F:	arch/s390/mm

They both have the same T: git git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git value. We need another criteria that would determine that the former is better than the latter. Counting the number of files matched by the regexps could be a solution, but it will increase our computation time by a lot.

Or we just hard-code it for s390.