From 52f19d9678208ff18a18eb3560ece4ac465115c8 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 20 Sep 2022 13:39:51 +0200
Subject: [PATCH] stat-util: add statx_mount_same() to check if two stax refer
 to the same mount

---
 src/basic/stat-util.c | 13 +++++++++++++
 src/basic/stat-util.h |  1 +
 2 files changed, 14 insertions(+)

diff --git a/src/basic/stat-util.c b/src/basic/stat-util.c
index cb6fe9ebdb6..51adaca9d07 100644
--- a/src/basic/stat-util.c
+++ b/src/basic/stat-util.c
@@ -373,6 +373,19 @@ bool statx_inode_same(const struct statx *a, const struct statx *b) {
                 a->stx_ino == b->stx_ino;
 }
 
+bool statx_mount_same(const struct new_statx *a, const struct new_statx *b) {
+        if (!a || !b)
+                return false;
+
+        /* if we have the mount ID, that's all we need */
+        if (FLAGS_SET(a->stx_mask, STATX_MNT_ID) && FLAGS_SET(b->stx_mask, STATX_MNT_ID))
+                return a->stx_mnt_id == b->stx_mnt_id;
+
+        /* Otherwise, major/minor of backing device must match */
+        return a->stx_dev_major == b->stx_dev_major &&
+                a->stx_dev_minor == b->stx_dev_minor;
+}
+
 int statx_fallback(int dfd, const char *path, int flags, unsigned mask, struct statx *sx) {
         static bool avoid_statx = false;
         struct stat st;
diff --git a/src/basic/stat-util.h b/src/basic/stat-util.h
index 4972af0c695..f9519d8cbde 100644
--- a/src/basic/stat-util.h
+++ b/src/basic/stat-util.h
@@ -74,6 +74,7 @@ bool stat_inode_same(const struct stat *a, const struct stat *b);
 bool stat_inode_unmodified(const struct stat *a, const struct stat *b);
 
 bool statx_inode_same(const struct statx *a, const struct statx *b);
+bool statx_mount_same(const struct new_statx *a, const struct new_statx *b);
 
 int statx_fallback(int dfd, const char *path, int flags, unsigned mask, struct statx *sx);