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SubjectRe: [PATCH] lib/fs: fix issue when {name, open}_to_handle_at() is not implemented
Hi,

> With commit d5e6ee0dac64b64e the usage of functions name_to_handle_at() and
> open_by_handle_at() are introduced. But these function are not available
> e.g. in uclibc-ng < 1.0.35. To have a backward compatibility check for the
> availability in the configure script and in case of absence do a direct
> syscall.

LGTM, thanks for implementing it.
I'd consider to check only one of the functions (very unlikely only one will be
supported).

> Signed-off-by: Heiko Thiery <heiko.thiery@gmail.com>
> ---
> configure | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> lib/fs.c | 25 ++++++++++++++++++++++++
> 2 files changed, 83 insertions(+)

> diff --git a/configure b/configure
> index 2c363d3b..f1be9977 100755
> --- a/configure
> +++ b/configure
> @@ -202,6 +202,58 @@ EOF
> rm -f $TMPDIR/setnstest.c $TMPDIR/setnstest
> }

> +check_name_to_handle_at()
> +{
> +
nit: empty line.
> + cat >$TMPDIR/name_to_handle_at_test.c <<EOF
It's interesting it does not require _GNU_SOURCE ? (IMHO this is normally
required for all glibc, musl, uclibc and binder):

#define _GNU_SOURCE
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <fcntl.h>
> +int main(int argc, char **argv)
> +{
> + struct file_handle *fhp;
> + int mount_id, flags, dirfd;
> + char *pathname;
> + name_to_handle_at(dirfd, pathname, fhp, &mount_id, flags);
> + return 0;
> +}
> +EOF
> +
> + if $CC -I$INCLUDE -o $TMPDIR/name_to_handle_at_test $TMPDIR/name_to_handle_at_test.c >/dev/null 2>&1; then
> + echo "IP_CONFIG_NAME_TO_HANDLE_AT:=y" >>$CONFIG
> + echo "yes"
> + echo "CFLAGS += -DHAVE_NAME_TO_HANDLE_AT" >>$CONFIG
> + else
> + echo "no"
> + fi
> + rm -f $TMPDIR/name_to_handle_at_test.c $TMPDIR/name_to_handle_at_test
> +}
> +
> +check_open_by_handle_at()
> +{
> +
nit: empty line.
> + cat >$TMPDIR/open_by_handle_at_test.c <<EOF
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <fcntl.h>
> +int main(int argc, char **argv)
> +{
> + struct file_handle *fhp;
> + int mount_fd;
> + open_by_handle_at(mount_fd, fhp, O_RDONLY);
> + return 0;
> +}
> +EOF
> + if $CC -I$INCLUDE -o $TMPDIR/open_by_handle_at_test $TMPDIR/open_by_handle_at_test.c >/dev/null 2>&1; then
> + echo "IP_CONFIG_OPEN_BY_HANDLE_AT:=y" >>$CONFIG
> + echo "yes"
> + echo "CFLAGS += -DHAVE_OPEN_BY_HANDLE_AT" >>$CONFIG
> + else
> + echo "no"
> + fi
> + rm -f $TMPDIR/open_by_handle_at_test.c $TMPDIR/open_by_handle_at_test
> +}
> +
> check_ipset()
> {
> cat >$TMPDIR/ipsettest.c <<EOF
> @@ -492,6 +544,12 @@ fi
> echo -n "libc has setns: "
> check_setns

> +echo -n "libc has name_to_handle_at: "
> +check_name_to_handle_at
> +
> +echo -n "libc has open_by_handle_at: "
> +check_open_by_handle_at
> +
> echo -n "SELinux support: "
> check_selinux

> diff --git a/lib/fs.c b/lib/fs.c
> index ee0b130b..c561d85b 100644
> --- a/lib/fs.c
> +++ b/lib/fs.c
> @@ -30,6 +30,31 @@
> /* if not already mounted cgroup2 is mounted here for iproute2's use */
> #define MNT_CGRP2_PATH "/var/run/cgroup2"

> +
> +#if (!defined HAVE_NAME_TO_HANDLE_AT && !defined HAVE_OPEN_BY_HANDLE_AT)
> +struct file_handle {
> + unsigned handle_bytes;
> + int handle_type;
> + unsigned char f_handle[];
> +};
> +#endif
> +
> +#ifndef HAVE_NAME_TO_HANDLE_AT
> +int name_to_handle_at(int dirfd, const char *pathname,
> + struct file_handle *handle, int *mount_id, int flags)
> +{
> + return syscall(name_to_handle_at, 5, dirfd, pathname, handle,
> + mount_id, flags);
> +}
> +#endif
> +
> +#ifndef HAVE_OPEN_BY_HANDLE_AT
> +int open_by_handle_at(int mount_fd, struct file_handle *handle, int flags)
> +{
> + return syscall(open_by_handle_at, 3, mount_fd, handle, flags);
> +}
> +#endif
> +
> /* return mount path of first occurrence of given fstype */
> static char *find_fs_mount(const char *fs_to_find)
> {

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