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mount-util: add helper that can bind mount submounts of one dir to another

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This commit is contained in:
Lennart Poettering
2023-06-23 18:30:59 +02:00
parent 4a1dca795c
commit 1b618bf141
3 changed files with 137 additions and 4 deletions
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src/shared/mount-util.c
+62 -4
View File
@@ -1251,7 +1251,11 @@ static void sub_mount_drop(SubMount *s, size_t n) {
}
}
static int get_sub_mounts(const char *prefix, SubMount **ret_mounts, size_t *ret_n_mounts) {
static int get_sub_mounts(
const char *prefix,
bool clone_tree,
SubMount **ret_mounts,
size_t *ret_n_mounts) {
_cleanup_(mnt_free_tablep) struct libmnt_table *table = NULL;
_cleanup_(mnt_free_iterp) struct libmnt_iter *iter = NULL;
SubMount *mounts = NULL;
@@ -1301,12 +1305,15 @@ static int get_sub_mounts(const char *prefix, SubMount **ret_mounts, size_t *ret
continue;
}
mount_fd = open_tree(AT_FDCWD, path, OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC | AT_RECURSIVE);
if (clone_tree)
mount_fd = open_tree(AT_FDCWD, path, OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC | AT_RECURSIVE);
else
mount_fd = open(path, O_CLOEXEC|O_PATH);
if (mount_fd < 0) {
if (errno == ENOENT) /* The path may be hidden by another over-mount or already unmounted. */
continue;
return log_debug_errno(errno, "Failed to open tree of mounted filesystem '%s': %m", path);
return log_debug_errno(errno, "Failed to open subtree of mounted filesystem '%s': %m", path);
}
p = strdup(path);
@@ -1374,7 +1381,7 @@ int remount_and_move_sub_mounts(
return mount_nofollow_verbose(LOG_DEBUG, what, where, type, flags, options);
/* Get the list of sub-mounts and duplicate them. */
r = get_sub_mounts(where, &mounts, &n);
r = get_sub_mounts(where, /* clone_tree= */ true, &mounts, &n);
if (r < 0)
return r;
@@ -1390,6 +1397,57 @@ int remount_and_move_sub_mounts(
return move_sub_mounts(mounts, n);
}
int bind_mount_submounts(
const char *source,
const char *target) {
SubMount *mounts = NULL;
size_t n = 0;
int ret = 0, r;
/* Bind mounts all child mounts of 'source' to 'target'. Useful when setting up a new procfs instance
* with new mount options to copy the original submounts over. */
assert(source);
assert(target);
CLEANUP_ARRAY(mounts, n, sub_mount_array_free);
r = get_sub_mounts(source, /* clone_tree= */ false, &mounts, &n);
if (r < 0)
return r;
FOREACH_ARRAY(m, mounts, n) {
_cleanup_free_ char *t = NULL;
const char *suffix;
if (isempty(m->path))
continue;
assert_se(suffix = path_startswith(m->path, source));
t = path_join(target, suffix);
if (!t)
return -ENOMEM;
r = path_is_mount_point(t, NULL, 0);
if (r < 0) {
log_debug_errno(r, "Failed to detect if '%s' already is a mount point, ignoring: %m", t);
continue;
}
if (r > 0) {
log_debug("Not bind mounting '%s' from '%s' to '%s', since there's already a mountpoint.", suffix, source, target);
continue;
}
r = mount_follow_verbose(LOG_DEBUG, FORMAT_PROC_FD_PATH(m->mount_fd), t, NULL, MS_BIND|MS_REC, NULL);
if (r < 0 && ret == 0)
ret = r;
}
return ret;
}
int remount_sysfs(const char *where) {
return remount_and_move_sub_mounts("sysfs", where, "sysfs", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL);
}
src/shared/mount-util.h
+4
View File
@@ -132,6 +132,10 @@ int remount_and_move_sub_mounts(
const char *options);
int remount_sysfs(const char *where);
int bind_mount_submounts(
const char *source,
const char *target);
/* Creates a mount point (not parents) based on the source path or stat - ie, a file or a directory */
int make_mount_point_inode_from_stat(const struct stat *st, const char *dest, mode_t mode);
int make_mount_point_inode_from_path(const char *source, const char *dest, mode_t mode);
src/test/test-mount-util.c
+71
View File
@@ -568,6 +568,77 @@ TEST(fd_make_mount_point) {
}
}
TEST(bind_mount_submounts) {
_cleanup_(rmdir_and_freep) char *a = NULL, *b = NULL;
_cleanup_free_ char *x = NULL;
int r;
assert_se(mkdtemp_malloc(NULL, &a) >= 0);
r = mount_nofollow_verbose(LOG_INFO, "tmpfs", a, "tmpfs", 0, NULL);
if (r < 0 && ERRNO_IS_PRIVILEGE(r)) {
(void) log_tests_skipped("Skipping bind_mount_submounts() test, lacking privileges");
return;
}
assert_se(r >= 0);
assert_se(x = path_join(a, "foo"));
assert_se(touch(x) >= 0);
free(x);
assert_se(x = path_join(a, "x"));
assert_se(mkdir(x, 0755) >= 0);
assert_se(mount_nofollow_verbose(LOG_INFO, "tmpfs", x, "tmpfs", 0, NULL) >= 0);
free(x);
assert_se(x = path_join(a, "x/xx"));
assert_se(touch(x) >= 0);
free(x);
assert_se(x = path_join(a, "y"));
assert_se(mkdir(x, 0755) >= 0);
assert_se(mount_nofollow_verbose(LOG_INFO, "tmpfs", x, "tmpfs", 0, NULL) >= 0);
free(x);
assert_se(x = path_join(a, "y/yy"));
assert_se(touch(x) >= 0);
free(x);
assert_se(mkdtemp_malloc(NULL, &b) >= 0);
assert_se(mount_nofollow_verbose(LOG_INFO, "tmpfs", b, "tmpfs", 0, NULL) >= 0);
assert_se(x = path_join(b, "x"));
assert_se(mkdir(x, 0755) >= 0);
free(x);
assert_se(x = path_join(b, "y"));
assert_se(mkdir(x, 0755) >= 0);
free(x);
assert_se(bind_mount_submounts(a, b) >= 0);
assert_se(x = path_join(b, "foo"));
assert_se(access(x, F_OK) < 0 && errno == ENOENT);
free(x);
assert_se(x = path_join(b, "x/xx"));
assert_se(access(x, F_OK) >= 0);
free(x);
assert_se(x = path_join(b, "y/yy"));
assert_se(access(x, F_OK) >= 0);
free(x);
assert_se(x = path_join(b, "x"));
assert_se(path_is_mount_point(x, NULL, 0) > 0);
free(x);
assert_se(x = path_join(b, "y"));
assert_se(path_is_mount_point(x, NULL, 0) > 0);
assert_se(umount_recursive(a, 0) >= 0);
assert_se(umount_recursive(b, 0) >= 0);
}
static int intro(void) {
/* Create a dummy network interface for testing remount_sysfs(). */
(void) system("ip link add dummy-test-mnt type dummy");