consider two files sharing the same inode identical

This gives a substantial speedup when comparing directory
structures with many hardlinked files, e.g. when using
rsnapshot for incremental backup.

ok stsp@ millert@

diff --git a/usr.bin/diff/diffreg.c b/usr.bin/diff/diffreg.c
index e834fd4..ae49b7f 100644 (file)
--- a/usr.bin/diff/diffreg.c
+++ b/usr.bin/diff/diffreg.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: diffreg.c,v 1.93 2019/06/28 13:35:00 deraadt Exp $    */
+/*     $OpenBSD: diffreg.c,v 1.94 2021/09/01 18:16:52 halex Exp $      */
 
 /*
  * Copyright (C) Caldera International Inc.  2001-2002.
@@ -429,6 +429,10 @@ files_differ(FILE *f1, FILE *f2, int flags)
        if ((flags & (D_EMPTY1|D_EMPTY2)) || stb1.st_size != stb2.st_size ||
            (stb1.st_mode & S_IFMT) != (stb2.st_mode & S_IFMT))
                return (1);
+
+       if (stb1.st_dev == stb2.st_dev && stb1.st_ino == stb2.st_ino)
+               return (0);
+
        for (;;) {
                i = fread(buf1, 1, sizeof(buf1), f1);
                j = fread(buf2, 1, sizeof(buf2), f2);