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authorKarel Zak <kzak@redhat.com>2025-11-19 13:01:02 +0100
committerKarel Zak <kzak@redhat.com>2025-11-20 11:25:22 +0100
commit5fc8401d09d791d132badd3029426407a8733dea (patch)
tree451d16a491a24770ae6e8dbcc1b4cb7caf2113f0
parent142eedfb247710db65f127e9738d5ffab7e27cae (diff)
downloadutil-linux-5fc8401d09d791d132badd3029426407a8733dea.tar.gz
mountpoint: use statmount() syscall on modern kernels
Improve mountpoint(1) to use the modern statmount() system call (available since Linux 6.8) instead of parsing /proc/self/mountinfo. - Works without /proc mounted on modern kernels - More efficient than parsing /proc/self/mountinfo - Better detection of bind mounts via statmount() - Graceful fallback maintains compatibility Addresses: https://github.com/util-linux/util-linux/issues/3806 Signed-off-by: Karel Zak <kzak@redhat.com>
Diffstat
-rw-r--r--sys-utils/mountpoint.1.adoc2
-rw-r--r--sys-utils/mountpoint.c108
2 files changed, 98 insertions, 12 deletions
diff --git a/sys-utils/mountpoint.1.adoc b/sys-utils/mountpoint.1.adoc
index bc8a2e9ed6..0e1252c72c 100644
--- a/sys-utils/mountpoint.1.adoc
+++ b/sys-utils/mountpoint.1.adoc
@@ -18,7 +18,7 @@ mountpoint - see if a directory or file is a mountpoint
== DESCRIPTION
-*mountpoint* checks whether the given _directory_ or _file_ is mentioned in the _/proc/self/mountinfo_ file.
+*mountpoint* checks whether the given _directory_ or _file_ is a mountpoint. On kernels that support the *statmount*(2) system call (Linux 6.8 and newer), it uses that interface. On older kernels, it falls back to reading _/proc/self/mountinfo_.
== OPTIONS
diff --git a/sys-utils/mountpoint.c b/sys-utils/mountpoint.c
index 6294a4c07a..8a114b5bb0 100644
--- a/sys-utils/mountpoint.c
+++ b/sys-utils/mountpoint.c
@@ -31,6 +31,7 @@
#include "c.h"
#include "closestream.h"
#include "pathnames.h"
+#include "mount-api-utils.h"
#define MOUNTPOINT_EXIT_NOMNT 32
@@ -44,13 +45,80 @@ struct mountpoint_control {
quiet;
};
+#ifdef HAVE_STATMOUNT_API
+/*
+ * dir_to_device_statmount - check if path is a mountpoint using statmount()
+ * @ctl: mountpoint control structure
+ *
+ * Returns: <0 on error, 0 if mountpoint, 1 if not a mountpoint
+ */
+static int dir_to_device_statmount(struct mountpoint_control *ctl)
+{
+ struct libmnt_fs *fs = NULL;
+ const char *mnt_target;
+ char *cn = NULL;
+ uint64_t id = 0;
+ int rc;
+
+ cn = mnt_resolve_path(ctl->path, NULL);
+
+ rc = mnt_id_from_path(cn ? cn : ctl->path, &id, NULL);
+ if (rc)
+ goto done;
+
+ fs = mnt_new_fs();
+ if (!fs) {
+ rc = -ENOMEM;
+ goto done;
+ }
+
+ mnt_fs_set_uniq_id(fs, id);
+
+ rc = mnt_fs_fetch_statmount(fs, STATMOUNT_MNT_POINT | STATMOUNT_SB_BASIC);
+ if (rc)
+ goto done;
+
+ mnt_target = mnt_fs_get_target(fs);
+ if (!mnt_target) {
+ rc = -EINVAL;
+ goto done;
+ }
+
+ if (strcmp(mnt_target, cn ? cn : ctl->path) != 0)
+ rc = 1; /* not a mountpoint */
+ else {
+ ctl->dev = mnt_fs_get_devno(fs);
+ rc = 0; /* is a mountpoint */
+ }
+done:
+ free(cn);
+ mnt_unref_fs(fs);
+ return rc;
+}
+#endif /* STATMOUNT_MNT_POINT */
+
+/*
+ * dir_to_device - check if path is a mountpoint
+ * @ctl: mountpoint control structure
+ *
+ * Returns: <0 on error, 0 if mountpoint, 1 if not a mountpoint
+ */
static int dir_to_device(struct mountpoint_control *ctl)
{
- struct libmnt_table *tb = mnt_new_table_from_file(_PATH_PROC_MOUNTINFO);
+ struct libmnt_table *tb;
struct libmnt_fs *fs;
struct libmnt_cache *cache;
- int rc = -1;
+ int rc;
+#ifdef HAVE_STATMOUNT_API
+ rc = dir_to_device_statmount(ctl);
+ if (rc >= 0)
+ return rc;
+#endif
+ /*
+ * Fallback for older kernels without statmount() support
+ */
+ tb = mnt_new_table_from_file(_PATH_PROC_MOUNTINFO);
if (!tb) {
/*
* Fallback. Traditional way to detect mountpoints. This way
@@ -66,16 +134,18 @@ static int dir_to_device(struct mountpoint_control *ctl)
free(cn);
if (len < 0 || (size_t) len >= sizeof(buf))
- return -1;
- if (stat(buf, &pst) !=0)
- return -1;
+ return -EINVAL;
+
+ rc = stat(buf, &pst);
+ if (rc)
+ return -errno;
if (ctl->st.st_dev != pst.st_dev || ctl->st.st_ino == pst.st_ino) {
ctl->dev = ctl->st.st_dev;
- return 0;
+ return 0; /* is a mountpoint */
}
- return -1;
+ return 1; /* not a mountpoint */
}
/* to canonicalize all necessary paths */
@@ -86,8 +156,9 @@ static int dir_to_device(struct mountpoint_control *ctl)
fs = mnt_table_find_target(tb, ctl->path, MNT_ITER_BACKWARD);
if (fs && mnt_fs_get_target(fs)) {
ctl->dev = mnt_fs_get_devno(fs);
- rc = 0;
- }
+ rc = 0; /* is a mountpoint */
+ } else
+ rc = 1; /* not a mountpoint */
mnt_unref_table(tb);
return rc;
@@ -129,7 +200,7 @@ static void __attribute__((__noreturn__)) usage(void)
int main(int argc, char **argv)
{
- int c;
+ int c, rc;
struct mountpoint_control ctl = { NULL };
enum {
@@ -196,11 +267,26 @@ int main(int argc, char **argv)
if (ctl.dev_devno)
return print_devno(&ctl) ? MOUNTPOINT_EXIT_NOMNT : EXIT_SUCCESS;
- if ((ctl.nofollow && S_ISLNK(ctl.st.st_mode)) || dir_to_device(&ctl)) {
+ if (ctl.nofollow && S_ISLNK(ctl.st.st_mode)) {
+ if (!ctl.quiet)
+ printf(_("%s is not a mountpoint\n"), ctl.path);
+ return MOUNTPOINT_EXIT_NOMNT;
+ }
+
+ rc = dir_to_device(&ctl);
+ if (rc < 0) {
+ if (!ctl.quiet) {
+ errno = -rc;
+ warn("%s", ctl.path);
+ }
+ return EXIT_FAILURE;
+ }
+ if (rc == 1) {
if (!ctl.quiet)
printf(_("%s is not a mountpoint\n"), ctl.path);
return MOUNTPOINT_EXIT_NOMNT;
}
+
if (ctl.fs_devno)
printf("%u:%u\n", major(ctl.dev), minor(ctl.dev));
else if (!ctl.quiet)
generated by cgit 1.2.3-korg (git 2.43.0) at 2025-12-05 19:53:01 +0000