From: Karel Zak <kzak@redhat.com>
Date: Mon, 22 Mar 2021 10:24:49 +0000 (+0100)
Subject: libmount: add mnt_table_over_fs()
X-Git-Tag: v2.37-rc1~53
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a6055682811bac0dc5c6219bfde03c53290ad142;p=thirdparty%2Futil-linux.git

libmount: add mnt_table_over_fs()

The function returns the first over-mount for specified filesystem.

Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/libmount/docs/libmount-sections.txt b/libmount/docs/libmount-sections.txt
index 911dc0a0f0..89b2b1e8ba 100644
--- a/libmount/docs/libmount-sections.txt
+++ b/libmount/docs/libmount-sections.txt
@@ -365,6 +365,7 @@ mnt_table_last_fs
 mnt_table_move_fs
 mnt_table_next_child_fs
 mnt_table_next_fs
+mnt_table_over_fs
 mnt_table_parse_dir
 mnt_table_parse_file
 mnt_table_parse_fstab
diff --git a/libmount/src/libmount.h.in b/libmount/src/libmount.h.in
index b7b278d0e3..2d4d044e95 100644
--- a/libmount/src/libmount.h.in
+++ b/libmount/src/libmount.h.in
@@ -570,6 +570,8 @@ extern int mnt_table_move_fs(struct libmnt_table *src, struct libmnt_table *dst,
 extern int mnt_table_remove_fs(struct libmnt_table *tb, struct libmnt_fs *fs);
 extern int mnt_table_first_fs(struct libmnt_table *tb, struct libmnt_fs **fs);
 extern int mnt_table_last_fs(struct libmnt_table *tb, struct libmnt_fs **fs);
+extern int mnt_table_over_fs(struct libmnt_table *tb, struct libmnt_fs *parent,
+                             struct libmnt_fs **child);
 extern int mnt_table_next_fs(struct libmnt_table *tb, struct libmnt_iter *itr,
 			     struct libmnt_fs **fs);
 extern int mnt_table_next_child_fs(struct libmnt_table *tb, struct libmnt_iter *itr,
diff --git a/libmount/src/libmount.sym b/libmount/src/libmount.sym
index e98e44b9c6..85e89ad020 100644
--- a/libmount/src/libmount.sym
+++ b/libmount/src/libmount.sym
@@ -359,4 +359,5 @@ MOUNT_2_35 {
 
 MOUNT_2_37 {
 	mnt_fs_get_vfs_options_all;
+	mnt_table_over_fs;
 } MOUNT_2_35;
diff --git a/libmount/src/tab.c b/libmount/src/tab.c
index e91254a712..465708f618 100644
--- a/libmount/src/tab.c
+++ b/libmount/src/tab.c
@@ -706,6 +706,55 @@ int mnt_table_next_child_fs(struct libmnt_table *tb, struct libmnt_iter *itr,
 	return 0;
 }
 
+/**
+ * mnt_table_over_fs:
+ * @tb: tab pointer
+ * @parent: pointer to parental FS
+ * @child: returns pointer to FS which over-mounting parent
+ *
+ * This function returns by @child the first filesystenm which is over-mounted
+ * on @parent. It means the mountpoint of @child is the same as for @parent and
+ * parent->id is the same as child->parent_id.
+ *
+ * Note that you need to call this function in loop until it returns 1 to get
+ * the highest filesystem.
+ *
+ * Example:
+ * <informalexample>
+ *   <programlisting>
+ *	while (mnt_table_over_fs(tb, cur, &over) == 0) {
+ *		printf("%s overmounted by %d\n", mnt_fs_get_target(cur), mnt_fs_get_id(over));
+ *		cur = over;
+ *	}
+ *   </programlisting>
+ * </informalexample>
+ *
+ * Returns: 0 on success, negative number in case of error or 1 at the end of list.
+ */
+int mnt_table_over_fs(struct libmnt_table *tb, struct libmnt_fs *parent,
+		      struct libmnt_fs **child)
+{
+	struct libmnt_iter itr;
+	int id;
+	const char *tgt;
+
+	if (!tb || !parent || !is_mountinfo(tb))
+		return -EINVAL;
+
+	mnt_reset_iter(&itr, MNT_ITER_FORWARD);
+	id = mnt_fs_get_id(parent);
+	tgt = mnt_fs_get_target(parent);
+
+	while (mnt_table_next_fs(tb, &itr, child) == 0) {
+		if (mnt_fs_get_parent_id(*child) == id &&
+		    mnt_fs_streq_target(*child, tgt) == 1)
+			return 0;
+	}
+
+	*child = NULL;
+	return 1;	/* nothing */
+}
+
 /**
  * mnt_table_next_fs:
  * @tb: tab pointer