linux-kernel - Re: [RESEND PATCH] selftests/overlayfs: fix compilation error in overlayfs

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Date: Tue, 27 Feb 2024 13:20:53 -0800
From: Andrei Vagin <avagin@...gle.com>
To: Shuah Khan <skhan@...uxfoundation.org>
Cc: Meng Li <li.meng@....com>, Huang Rui <ray.huang@....com>, linux-pm@...r.kernel.org, 
	Nathan Fontenot <nathan.fontenot@....com>, Deepak Sharma <deepak.sharma@....com>, 
	Alex Deucher <alexander.deucher@....com>, Mario Limonciello <mario.limonciello@....com>, 
	Perry Yuan <Perry.Yuan@....com>, Xiaojian Du <Xiaojian.Du@....com>, 
	Viresh Kumar <viresh.kumar@...aro.org>, Borislav Petkov <bp@...en8.de>, linux-kernel@...r.kernel.org, 
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>
Subject: Re: [RESEND PATCH] selftests/overlayfs: fix compilation error in overlayfs

On Tue, Feb 27, 2024 at 8:41 AM Shuah Khan <skhan@...uxfoundation.org> wrote:
>
> On 2/27/24 00:42, Meng Li wrote:
> > make -C tools/testing/selftests, compiling dev_in_maps fail.
> > In file included from dev_in_maps.c:10:
> > /usr/include/x86_64-linux-gnu/sys/mount.h:35:3: error: expected identifier before numeric constant
> >     35 |   MS_RDONLY = 1,                /* Mount read-only.  */
> >        |   ^~~~~~~~~
> >
> > That sys/mount.h has to be included before linux/mount.h.
> >
> > Signed-off-by: Meng Li <li.meng@....com>
> > ---
> >   tools/testing/selftests/filesystems/overlayfs/dev_in_maps.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
>
> I don't see this problem when I build it on my system when
> I run:
>
> make -C tools/testing/selftests
> or
> make -C tools/testing/selftests/filesystems/overlayfs
>
> Are you running this after doing headers_install?

It depends on libc headers. It can work with one libc and doesn't work
with another one. I have seen many times when linux headers conflicted
with libc headers. The only reliable way to avoid this sort of issues is
to include just one linux or libc header.

In this case, we can do something like this:

diff --git a/tools/testing/selftests/filesystems/overlayfs/dev_in_maps.c
b/tools/testing/selftests/filesystems/overlayfs/dev_in_maps.c
index e19ab0e85709..f1ba82e52192 100644
--- a/tools/testing/selftests/filesystems/overlayfs/dev_in_maps.c
+++ b/tools/testing/selftests/filesystems/overlayfs/dev_in_maps.c
@@ -10,7 +10,6 @@
 #include <linux/mount.h>
 #include <sys/syscall.h>
 #include <sys/stat.h>
-#include <sys/mount.h>
 #include <sys/mman.h>
 #include <sched.h>
 #include <fcntl.h>
@@ -40,6 +39,14 @@ static int sys_move_mount(int from_dfd, const char
*from_pathname,
        return syscall(__NR_move_mount, from_dfd, from_pathname,
to_dfd, to_pathname, flags);
 }

+static int sys_mount(const char *source, const char *target,
+                    const char *filesystemtype, unsigned long mountflags,
+                    const void *data)
+{
+       return syscall(__NR_mount, source, target, filesystemtype,
mountflags, data);
+}
+
+
 static long get_file_dev_and_inode(void *addr, struct statx *stx)
 {
        char buf[4096];
@@ -167,7 +174,7 @@ int main(int argc, char **argv)
                return 1;
        }

-       if (mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL) == -1) {
+       if (sys_mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL) == -1) {
                pr_perror("mount");
                return 1;
        }

Thanks,
Andrei