libmount: add mnt_table_find_mountpoint()

This is more robust implementation of mnt_get_mountpoint() that does
not ignore bind mountpoints (mount --bind /mnt /mnt) as it does not
depend on st_dev numbers.

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

6 files changed, 83 insertions, 1 deletions

diff --git a/libmount/docs/libmount-sections.txt b/libmount/docs/libmount-sections.txt
index 3475630d7..2c3dab722 100644
--- a/libmount/docs/libmount-sections.txt
+++ b/libmount/docs/libmount-sections.txt
@@ -283,6 +283,7 @@ mnt_new_table_from_dir
 mnt_new_table_from_file
 mnt_table_add_fs
 mnt_table_find_devno
+mnt_table_find_mountpoint
 mnt_table_find_next_fs
 mnt_table_find_pair
 mnt_table_find_source
diff --git a/libmount/src/libmount.h.in b/libmount/src/libmount.h.in
index 739f5daee..1b5df82ac 100644
--- a/libmount/src/libmount.h.in
+++ b/libmount/src/libmount.h.in
@@ -462,6 +462,8 @@ extern int mnt_table_get_root_fs(struct libmnt_table *tb, struct libmnt_fs **roo
 extern int mnt_table_set_iter(struct libmnt_table *tb, struct libmnt_iter *itr,
 			      struct libmnt_fs *fs);
 
+extern struct libmnt_fs *mnt_table_find_mountpoint(struct libmnt_table *tb,
+				const char *path, int direction);
 extern struct libmnt_fs *mnt_table_find_target(struct libmnt_table *tb,
 				const char *path, int direction);
 extern struct libmnt_fs *mnt_table_find_srcpath(struct libmnt_table *tb,
diff --git a/libmount/src/libmount.sym b/libmount/src/libmount.sym
index 9fc0ee6b0..2ea483989 100644
--- a/libmount/src/libmount.sym
+++ b/libmount/src/libmount.sym
@@ -254,4 +254,5 @@ global:
 	mnt_fs_get_optional_fields;
 	mnt_fs_get_propagation;
 	mnt_context_find_umount_fs;
+	mnt_table_find_mountpoint;
 } MOUNT_2.22;
diff --git a/libmount/src/mountP.h b/libmount/src/mountP.h
index 1b4ba687b..065b815c1 100644
--- a/libmount/src/mountP.h
+++ b/libmount/src/mountP.h
@@ -132,6 +132,8 @@ extern int endswith(const char *s, const char *sx)
 extern int startswith(const char *s, const char *sx)
 			__attribute__((nonnull));
 
+extern char *stripoff_last_component(char *path);
+
 extern int is_file_empty(const char *name);
 
 extern int mkdir_p(const char *path, mode_t mode);
diff --git a/libmount/src/tab.c b/libmount/src/tab.c
index 5287da4a5..f70ed7de0 100644
--- a/libmount/src/tab.c
+++ b/libmount/src/tab.c
@@ -426,6 +426,51 @@ int mnt_table_set_iter(struct libmnt_table *tb, struct libmnt_iter *itr, struct
 }
 
 /**
+ * mnt_table_find_mountpoint:
+ * @tb: tab pointer
+ * @path: directory
+ * @direction: MNT_ITER_{FORWARD,BACKWARD}
+ *
+ * Same like mnt_get_mountpoint(), but this function does not rely on
+ * st_dev numbers.
+ *
+ * Returns: a tab entry or NULL.
+ */
+struct libmnt_fs *mnt_table_find_mountpoint(struct libmnt_table *tb,
+					    const char *path,
+					    int direction)
+{
+	char *mnt;
+
+	if (!tb || !path)
+		return NULL;
+
+	DBG(TAB, mnt_debug_h(tb, "lookup MOUNTPOINT: %s", path));
+
+	mnt = strdup(path);
+	if (!mnt)
+		return NULL;
+
+	do {
+		char *p;
+		struct libmnt_fs *fs;
+
+		fs = mnt_table_find_target(tb, mnt, direction);
+		if (fs) {
+			free(mnt);
+			return fs;
+		}
+
+		p = stripoff_last_component(mnt);
+		if (!p || !*p)
+			break;
+	} while (mnt && *(mnt + 1) != '\0');
+
+	free(mnt);
+	return mnt_table_find_target(tb, "/", direction);
+}
+
+/**
  * mnt_table_find_target:
  * @tb: tab pointer
  * @path: mountpoint directory
@@ -517,6 +562,8 @@ struct libmnt_fs *mnt_table_find_srcpath(struct libmnt_table *tb, const char *pa
 	const char *p;
 
 	assert(tb);
+	if (!tb || !path)
+		return NULL;
 
 	DBG(TAB, mnt_debug_h(tb, "lookup srcpath: %s", path));
 
@@ -1009,6 +1056,7 @@ done:
 }
 
 #ifdef TEST_PROGRAM
+#include "pathnames.h"
 
 static int parser_errcb(struct libmnt_table *tb, const char *filename, int line)
 {
@@ -1171,6 +1219,33 @@ done:
 	return rc;
 }
 
+int test_find_mountpoint(struct libmnt_test *ts, int argc, char *argv[])
+{
+	struct libmnt_table *tb;
+	struct libmnt_fs *fs;
+	struct libmnt_cache *mpc = NULL;
+	int rc = -1;
+
+	tb = mnt_new_table_from_file(_PATH_PROC_MOUNTINFO);
+	if (!tb)
+		return -1;
+	mpc = mnt_new_cache();
+	if (!mpc)
+		goto done;
+	mnt_table_set_cache(tb, mpc);
+
+	fs = mnt_table_find_mountpoint(tb, argv[1], MNT_ITER_BACKWARD);
+	if (!fs)
+		goto done;
+
+	mnt_fs_print_debug(fs, stdout);
+	rc = 0;
+done:
+	mnt_free_table(tb);
+	mnt_free_cache(mpc);
+	return rc;
+}
+
 static int test_is_mounted(struct libmnt_test *ts, int argc, char *argv[])
 {
 	struct libmnt_table *tb = NULL, *fstab = NULL;
@@ -1225,6 +1300,7 @@ int main(int argc, char *argv[])
 	{ "--find-forward",  test_find_fw, "<file> <source|target> <string>" },
 	{ "--find-backward", test_find_bw, "<file> <source|target> <string>" },
 	{ "--find-pair",     test_find_pair, "<file> <source> <target>" },
+	{ "--find-mountpoint", test_find_mountpoint, "<path>" },
 	{ "--copy-fs",       test_copy_fs, "<file>  copy root FS from the file" },
 	{ "--is-mounted",    test_is_mounted, "<fstab> check what from <file> are already mounted" },
 	{ NULL }
diff --git a/libmount/src/utils.c b/libmount/src/utils.c
index 1d4fd0e4b..5453789e3 100644
--- a/libmount/src/utils.c
+++ b/libmount/src/utils.c
@@ -94,7 +94,7 @@ static int fstype_cmp(const void *v1, const void *v2)
 
 /* returns basename and keeps dirname in the @path, if @path is "/" (root)
  * then returns empty string */
-static char *stripoff_last_component(char *path)
+char *stripoff_last_component(char *path)
 {
 	char *p = path ? strrchr(path, '/') : NULL;