[LTP] [PATCH 1/2] configure: Fix build on kernel 6.14 headers

[Petr Vorel]

Hi all,

> Hi!
> Let's push this now, it's simple enough and fixes the CI.

I'm sorry, it did not fix the problem due the old problem of indirect include
<linux/mount.h> by <linux/fs.h> on Alpine v3.22 (the default Alpine version in
GitHub action), which uses 6.14.2 kernel headers:

    In file included from /usr/include/linux/fs.h:19,
                     from /usr/include/linux/btrfs.h:29,
                     from statmount02.c:23:
    /usr/include/linux/mount.h:155:8: error: redefinition of 'struct statmount'
      155 | struct statmount {
          |        ^~~~~~~~~
    In file included from statmount.h:12,
                     from statmount02.c:20:
    ../../../../include/lapi/mount.h:58:8: note: originally defined here
       58 | struct statmount {
          |        ^~~~~~~~~
    /usr/include/linux/mount.h:193:8: error: redefinition of 'struct mnt_id_req'
      193 | struct mnt_id_req {
          |        ^~~~~~~~~~
    ../../../../include/lapi/mount.h:49:8: note: originally defined here
       49 | struct mnt_id_req {
          |        ^~~~~~~~~~

But we still support old Leap 42 (glibc 2.22 based), which requires for
statmount04.c old fallbacks for <sys/mount.h> but also new mount API
defined in <linux/mount.h>, otherwise it fails:

    statmount03.c:62:4: error: 'MS_PRIVATE' undeclared here (not in a function)
      { MS_PRIVATE, TST_TO_STR_(MS_PRIVATE) },
        ^
    statmount03.c:63:4: error: 'MS_SHARED' undeclared here (not in a function)
      { MS_SHARED, TST_TO_STR_(MS_SHARED) },
        ^
    statmount03.c:64:4: error: 'MS_SLAVE' undeclared here (not in a function)
      { MS_SLAVE, TST_TO_STR_(MS_SLAVE) },
        ^
    In file included from ../../../../include/tst_test.h:185:0,
                     from statmount.h:11,
                     from statmount04.c:21:
    statmount04.c: In function 'setup':
    statmount03.c:65:4: error: 'MS_UNBINDABLE' undeclared here (not in a function)
      { MS_UNBINDABLE, TST_TO_STR_(MS_UNBINDABLE) },
        ^
    statmount04.c:57:35: error: 'MS_BIND' undeclared (first use in this function)
      SAFE_MOUNT(DIR_A, DIR_A, "none", MS_BIND, NULL);
                                       ^
    ../../../../include/tst_safe_macros.h:244:25: note: in definition of macro 'SAFE_MOUNT'
          (filesystemtype), (mountflags), (data))
                             ^
    In file included from ../../../../include/tst_test.h:185:0,
                     from statmount.h:11,
                     from statmount03.c:21:
    statmount03.c: In function 'run':
    statmount04.c:57:35: note: each undeclared identifier is reported only once for each function it appears in
      SAFE_MOUNT(DIR_A, DIR_A, "none", MS_BIND, NULL);
                                       ^
    ../../../../include/tst_safe_macros.h:244:25: note: in definition of macro 'SAFE_MOUNT'
          (filesystemtype), (mountflags), (data))
                             ^
    statmount03.c:74:35: error: 'MS_BIND' undeclared (first use in this function)
      SAFE_MOUNT(DIR_B, DIR_A, "none", MS_BIND, NULL);

I suppose we should have 2 or 3 lapi files:

1) lapi/mount.h
mount definitions (guarded by #ifndef) - the old ones from <sys/mount.h> e.g.
MS_REC, MS_PRIVATE and probably the new ones from <linux/mount.h>, e.g.
MNT_ID_REQ_SIZE_VER0. None of <sys/mount.h> <linux/mount.h> should be included
in it.

2) lapi/linux_mount.h
mount structs (nowadays vast majority if not all from <linux/mount.h> only).
This header can include <linux/mount.h> and lapi/mount.h.
That allows to have configure.ac to safely use <linux/mount.h> for detection.

3) lapi/sys_mount.h
Optional helper header which would include lapi/mount.h and <sys/mount.h>
(to keep the current approach that lapi headers include system headers so that
tests does not need to do it.

WDYT?

Kind regards,
Petr