Better same file check for fsck

src/config.cpp

@@ -30,7 +30,7 @@
 #include <string.h>
 
 
-constexpr static const char CACHE_FILES_PROCESS_NAMES_DEFAULT[] =
+constexpr const char CACHE_FILES_PROCESS_NAMES_DEFAULT[] =
   "rtorrent|"
   "qbittorrent-nox";
 

src/fs_is_same_file.hpp

@@ -0,0 +1,62 @@
+/*
+  ISC License
+
+  Copyright (c) 2026, Antonio SJ Musumeci <[email protected]>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#pragma once
+
+#include "to_neg_errno.hpp"
+
+#include <string>
+
+#include <sys/stat.h>
+#include <unistd.h>
+
+
+namespace fs
+{
+  static
+  inline
+  int
+  is_same_file(const char *a_,
+               const char *b_)
+  {
+    int rv_a;
+    int rv_b;
+    struct stat st_a;
+    struct stat st_b;
+
+    rv_a = ::lstat(a_,&st_a);
+    rv_b = ::lstat(b_,&st_b);
+
+    if(rv_a < 0 || rv_b < 0)
+      return -errno;
+    if(st_a.st_dev != st_b.st_dev || st_a.st_ino != st_b.st_ino)
+      return 0;
+
+    return 1;
+  }
+
+  static
+  inline
+  int
+  is_same_file(const std::string &a_,
+               const std::string &b_)
+  {
+    return fs::is_same_file(a_.c_str(),
+                            b_.c_str());
+  }
+}

src/mergerfs_fsck.cpp

@@ -20,6 +20,7 @@
 
 #include "fs_close.hpp"
 #include "fs_copyfile.hpp"
+#include "fs_is_same_file.hpp"
 #include "fs_lchmod.hpp"
 #include "fs_lchown.hpp"
 #include "fs_lgetxattr.hpp"
@@ -246,10 +247,10 @@ _copy_files(const std::string &src_,
     {
       int rv;
 
-      // TODO: Additional protection to confirm not the literal same
-      // file. fs::is_same_file(src,dst);
       if(src_ == dst.path)
         continue;
+      if(fs::is_same_file(src_,dst.path) == 1)
+        continue;
 
       rv = fs::copyfile(src_,dst.path,{.cleanup_failure=false});
       if(rv < 0)