Fixes the following build warning:
```
In file included from ../../../home/runner/work/systemd/systemd/src/basic/assert-util.h:4,
from ../../../home/runner/work/systemd/systemd/src/basic/forward.h:17,
from ../../../home/runner/work/systemd/systemd/src/basic/filesystems.h:4,
from src/basic/filesystem-sets.c:2:
src/basic/filesystem-sets.c: In function ‘fs_in_group’:
../../../home/runner/work/systemd/systemd/src/fundamental/assert-fundamental.h:76:9: warning: array subscript 42 is above array bounds of ‘const char[28]’ [-Warray-bounds=]
76 | log_assert_failed_unreachable(PROJECT_FILE, __LINE__, __func__)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/basic/filesystem-sets.c:559:18: note: in expansion of macro ‘assert_not_reached’
559 | default: assert_not_reached();
| ^~~~~~~~~~~~~~~~~~
```
Follow-up for aca4353ab2.
Similar to fc4a9c9ce6.
We want to check if the magic we got from statfs() is one of the magics listed
for one of the file systems in the given group. To do this, we'd iteratate over
the file system names, convert each name to an array of magics, and compare
those to the one we got. We were using gperf-generated lookup table for this,
so the string lookups were quick, but still this seems unnecessarily complex.
Let's just generate a simple lookup function, because we can:
$ src/basic/filesystem-sets.py fs-in-group
bool fs_in_group(const struct statfs *st, FilesystemGroups fs_group) {
switch (fs_group) {
case FILESYSTEM_SET_BASIC_API:
return F_TYPE_EQUAL(st->f_type, CGROUP2_SUPER_MAGIC)
|| F_TYPE_EQUAL(st->f_type, CGROUP_SUPER_MAGIC)
|| F_TYPE_EQUAL(st->f_type, DEVPTS_SUPER_MAGIC)
|| F_TYPE_EQUAL(st->f_type, MQUEUE_MAGIC)
|| F_TYPE_EQUAL(st->f_type, PROC_SUPER_MAGIC)
|| F_TYPE_EQUAL(st->f_type, SYSFS_MAGIC)
|| F_TYPE_EQUAL(st->f_type, TMPFS_MAGIC);
case FILESYSTEM_SET_ANONYMOUS:
return F_TYPE_EQUAL(st->f_type, ANON_INODE_FS_MAGIC)
|| F_TYPE_EQUAL(st->f_type, PIPEFS_MAGIC)
|| F_TYPE_EQUAL(st->f_type, SOCKFS_MAGIC);
...
We flatten the nested lookup of group=>fs=>magic into a single level.
The compiler can work its magic here to make the lookup quick.
Previously, the gperf table was the main "source of truth", and additional
information (e.g. which file system names are obsolete) was scattered in
various files. We would then parse the gperf file, using python, awk, grep, and
bash, and use the results in various ways. This is hard to understand and
maintain. Let's replace all of this with a single python script that generates
the requested outputs as appropriate.
$ diff -u <(git show @{u}:src/basic/filesystems-gperf.gperf) \
<(src/basic/filesystem-sets.py gperf)
shows that the outputs are the same except for comments.
Similarly, 'src/basic/filesystem-sets.py fs-type-to-string' and
'src/basic/filesystem-sets.py filesystem-sets' can be used to view
the generated code.
The check that the kernel doesn't define any new file system magics is
converted into a normal test. It doesn't seem necessary to fail the build
when that happens.
Luca Boccassi
Yu Watanabe
Zbigniew Jędrzejewski-Szmek