Subscribers to block-device uevents need to apply the same filter set
blockdev_list() uses over the bulk enumeration, one device at a time.
Pull the per-device body out as blockdev_list_one(), expose
blockdev_list_get_root_devnos() so callers can compute the IGNORE_ROOT
devnos once up-front, and introduce a 4-valued return code so callers
can distinguish:
MATCH_NO - fails a static filter (subsystem, ZRAM, IGNORE_ROOT,
REQUIRE_PARTITION_SCANNING, REQUIRE_LUKS)
MATCH_YES - fully matches
MATCH_FILTERED - passes static filters but fails a dynamic one
(IGNORE_EMPTY, IGNORE_READ_ONLY) - useful to surface
as "device just became invisible" transitions when
the kernel flips size/ro at runtime
MATCH_SKIPPED - soft error during filter evaluation; callers should
treat this like MATCH_FILTERED, but the distinct code
makes the soft failure visible rather than silently
swallowed inside blockdev_list_one()
*ret is initialized on every non-negative return (BLOCK_DEVICE_NULL for
MATCH_NO / MATCH_SKIPPED, fully populated for MATCH_YES / MATCH_FILTERED),
and untouched on negative return. blockdev_list() itself collapses
everything except MATCH_YES back into "skip", so existing callers see
no behavior change.
Let's not leak details from src/shared and src/libsystemd into
src/basic, even though you can't actually do anything useful with
just forward declarations from src/shared.
The sd-forward.h header is put in src/libsystemd/sd-common as we
don't have a directory for shared internal headers for libsystemd
yet.
Let's also rename forward.h to basic-forward.h to keep things
self-explanatory.
Block devices with removable media (e.g. SD card readers) indicate a
missing medium with a zero size. Optionally ignore such block devices
that carry no medium currently.
Various of our tools operate on block devices, and it's not always
obvious to know which block devices are actually appropriate for use.
Hence, let's add a helper that allows to list block devices, and
supports some limited filtering.
Lennart Poettering
Lennart Poettering
Daan De Meyer