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-rw-r--r--fs/namespace.c29
1 files changed, 29 insertions, 0 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index e6c234b1a645..7a73383e8365 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1159,6 +1159,35 @@ struct vfsmount *mntget(struct vfsmount *mnt)
}
EXPORT_SYMBOL(mntget);
+/* path_is_mountpoint() - Check if path is a mount in the current
+ * namespace.
+ *
+ * d_mountpoint() can only be used reliably to establish if a dentry is
+ * not mounted in any namespace and that common case is handled inline.
+ * d_mountpoint() isn't aware of the possibility there may be multiple
+ * mounts using a given dentry in a different namespace. This function
+ * checks if the passed in path is a mountpoint rather than the dentry
+ * alone.
+ */
+bool path_is_mountpoint(const struct path *path)
+{
+ unsigned seq;
+ bool res;
+
+ if (!d_mountpoint(path->dentry))
+ return false;
+
+ rcu_read_lock();
+ do {
+ seq = read_seqbegin(&mount_lock);
+ res = __path_is_mountpoint(path);
+ } while (read_seqretry(&mount_lock, seq));
+ rcu_read_unlock();
+
+ return res;
+}
+EXPORT_SYMBOL(path_is_mountpoint);
+
struct vfsmount *mnt_clone_internal(struct path *path)
{
struct mount *p;