blkid: stop scanning on I/O error

Whenever we fail to read from a device it's pointless to
continue with probing; we should be failing immediately.
Otherwise the system will continue logging I/O errors.

This patch updates the probe functions to return the
negative error number on error and BLKID_PROBE_NONE
if not found.

[kzak@redhat.com: - fix s/return errno/return -errno/]

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Karel Zak <kzak@redhat.com>
blkid: convert superblocks to new calling convention

With the previous patch the scanning functions were
modified to return a differentiated return code.
To correctly abort scanning when an I/O error occurs
we need to differentiate between 'error' (= -1) and
'not found' (= 1) in the probe functions.
This patch updates all superblock scanning functions
to the new calling convention.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Karel Zak <kzak@redhat.com>
Merge branch 'fix-unshare-defines' of https://github.com/rudimeier/util-linux

* 'fix-unshare-defines' of https://github.com/rudimeier/util-linux:
  unshare: include libmount.h to provide missing MS_* defines
Merge remote-tracking branch 'github/master' into travis

* github/master:
  tests: try hard to create swaplabel's test image
  build-sys: libmount/python/__init__.py is always a dist file
  tests: return error if failures file not usable
  tests: write tests/failures to build- instead of srcdir
Merge branch 'fix-ipcs-q-fallback' into travis

* fix-ipcs-q-fallback:
  travis-ci: abort if make check fails
  ipcs: fix memleak in ipc_*_get_info functions
  ipcs: fix ipc_sem_get_info fallback case
  ipcs: fix ipc_shm_get_info fallback case
  ipcs: fix ipc_msg_get_info fallback case
  tests: add basic test case for ipcs -m -i n
  tests: add basic test case for ipcs -s -i n
  tests: add basic test case for ipcs -q -i n
  tests: quote generated arguments for ipcrm
  ipcs: cleanup jumplabel stlyes
Merge branch 'cfdisk-fix-typo' into travis

* cfdisk-fix-typo:
  cfdisk: fix typo (undeclared variable since b1f58330)
Merge branch 'fix-ppc-tests' into travis

* fix-ppc-tests:
  tests: fix utmpdump/ipv6tobin for bigendian
  tests: fix utmpdump/to-binary for bigendian
  tests: fix utmpdump/ipv6totxt for bigendian
  tests: fix utmpdump/to-text for bigendian
  tests: swaplabel needs to respect pagesize
travis-ci: add make distcheck
travis-ci: quick and dirty disable systemd stuff in make distcheck
tests, disable limits2 test
travis-ci: cat config.log
travis-ci: remove distcheck, add configure options
travis-ci: make install ...
travis-ci: increase git clone depth
travis-ci: install udev
travis-ci: install libmount-dev
travis-ci: --disable-use-tty-group