Rewrite using save-cwd.c and chdir to remove quadratic component of complexity.

Before, it processed O(n^2) directory name components via stat and mkdir.
Now it's O(n).  This makes mkdir -p a lot more efficient when creating
directories with very many components.  On a Linux 2.0.30 ext2fs filesystem
this command: mkdir -p `perl -e 'print "a/" x 500'`  now runs in 0.77 seconds
(user+sys).  Contrast that with the 9.5(!) seconds it took before.

diff --git a/lib/makepath.c b/lib/makepath.c
index 028e172af1253811b8050f1e31db5d3eb8a075b1..460129477b81bb3e210433a2721bb779d1e7ce60 100644 (file)
--- a/lib/makepath.c
+++ b/lib/makepath.c
@@ -1,5 +1,5 @@
 /* makepath.c -- Ensure that a directory path exists.
-   Copyright (C) 1990 Free Software Foundation, Inc.
+   Copyright (C) 1990, 1997 Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -28,7 +28,7 @@
 #  include <alloca.h>
 # else
 #  ifdef _AIX
- #pragma alloca
+ #  pragma alloca
 #  else
 char *alloca ();
 #  endif
@@ -76,9 +76,34 @@ typedef int uid_t;
 typedef int gid_t;
 #endif
 
+#include "save-cwd.h"
 #include "makepath.h"
-
-void error ();
+#include "error.h"
+
+void strip_trailing_slashes ();
+
+#define CLEANUP_CWD                                    \
+  do                                                   \
+    {                                                  \
+      /* We're done operating on basename_dir.         \
+        Restore working directory.  */                 \
+      if (saved_cwd)                                   \
+       {                                               \
+         int fail = restore_cwd (&cwd, NULL, NULL);    \
+         free_cwd (&cwd);                              \
+         if (fail)                                     \
+           return 1;                                   \
+       }                                               \
+    }                                                  \
+  while (0)
+
+#define CLEANUP                                                \
+  do                                                   \
+    {                                                  \
+      umask (oldmask);                                 \
+      CLEANUP_CWD;                                     \
+    }                                                  \
+  while (0)
 
 /* Ensure that the directory ARGPATH exists.
    Remove any trailing slashes from ARGPATH before calling this function.
@@ -120,17 +145,10 @@ make_path (argpath, mode, parent_mode, owner, group, preserve_existing,
      const char *verbose_fmt_string;
 #endif
 {
-  char *dirpath;               /* A copy we can scribble NULs on.  */
   struct stat stats;
   int retval = 0;
-  int oldmask = umask (0);
-
-  /* FIXME: move this alloca and strcpy into the if-block.
-     Set dirpath to argpath in the else-block.  */
-  dirpath = (char *) alloca (strlen (argpath) + 1);
-  strcpy (dirpath, argpath);
 
-  if (stat (dirpath, &stats))
+  if (stat (argpath, &stats))
     {
       char *slash;
       int tmp_mode;            /* Initial perms for leading dirs.  */
@@ -141,6 +159,19 @@ make_path (argpath, mode, parent_mode, owner, group, preserve_existing,
        struct ptr_list *next;
       };
       struct ptr_list *p, *leading_dirs = NULL;
+      int saved_cwd = 0;
+      struct saved_cwd cwd;
+      char *basename_dir;
+      int first_subdir = 1;
+      char *dirpath;
+
+      /* Temporarily relax umask in case it's overly restrictive.  */
+      int oldmask = umask (0);
+
+      /* Make a copy of ARGPATH that we can scribble NULs on.  */
+      dirpath = (char *) alloca (strlen (argpath) + 1);
+      strcpy (dirpath, argpath);
+      strip_trailing_slashes (dirpath);
 
       /* If leading directories shouldn't be writable or executable,
         or should have set[ug]id or sticky bits set and we are setting
@@ -159,17 +190,36 @@ make_path (argpath, mode, parent_mode, owner, group, preserve_existing,
        }
 
       slash = dirpath;
+
+      /* Skip over leading slashes.  */
       while (*slash == '/')
        slash++;
-      while ((slash = strchr (slash, '/')))
+
+      while (1)
        {
+         /* slash points to the leftmost unprocessed component of dirpath.  */
+         basename_dir = slash;
+
+         slash = strchr (slash, '/');
+         if (slash == NULL)
+           break;
+
+         if (first_subdir)
+           {
+             first_subdir = 0;
+             saved_cwd = !save_cwd (&cwd);
+           }
+
+         if (!saved_cwd)
+           basename_dir = dirpath;
+
          *slash = '\0';
-         if (stat (dirpath, &stats))
+         if (stat (basename_dir, &stats))
            {
-             if (mkdir (dirpath, tmp_mode))
+             if (mkdir (basename_dir, tmp_mode))
                {
                  error (0, errno, "cannot create directory `%s'", dirpath);
-                 umask (oldmask);
+                 CLEANUP;
                  return 1;
                }
              else
@@ -178,15 +228,17 @@ make_path (argpath, mode, parent_mode, owner, group, preserve_existing,
                    error (0, 0, verbose_fmt_string, dirpath);
 
                  if (owner != (uid_t) -1 && group != (gid_t) -1
-                     && chown (dirpath, owner, group)
+                     && chown (basename_dir, owner, group)
 #if defined(AFS) && defined (EPERM)
                      && errno != EPERM
 #endif
                      )
                    {
                      error (0, errno, "%s", dirpath);
-                     retval = 1;
+                     CLEANUP;
+                     return 1;
                    }
+
                  if (re_protect)
                    {
                      struct ptr_list *new = (struct ptr_list *)
@@ -200,7 +252,14 @@ make_path (argpath, mode, parent_mode, owner, group, preserve_existing,
          else if (!S_ISDIR (stats.st_mode))
            {
              error (0, 0, "`%s' exists but is not a directory", dirpath);
-             umask (oldmask);
+             CLEANUP;
+             return 1;
+           }
+
+         if (saved_cwd && chdir (basename_dir) < 0)
+           {
+             error (0, errno, "cannot chdir to directory, %s", dirpath);
+             CLEANUP;
              return 1;
            }
 
@@ -212,40 +271,49 @@ make_path (argpath, mode, parent_mode, owner, group, preserve_existing,
            slash++;
        }
 
+      if (!saved_cwd)
+       basename_dir = dirpath;
+
       /* We're done making leading directories.
         Create the final component of the path.  */
 
       /* The path could end in "/." or contain "/..", so test
         if we really have to create the directory.  */
 
-      if (stat (dirpath, &stats) && mkdir (dirpath, mode))
+      if (stat (basename_dir, &stats) && mkdir (basename_dir, mode))
        {
          error (0, errno, "cannot create directory `%s'", dirpath);
-         umask (oldmask);
+         CLEANUP;
          return 1;
        }
+
+      /* Done creating directories.  Restore original umask.  */
+      umask (oldmask);
+
       if (verbose_fmt_string != NULL)
        error (0, 0, verbose_fmt_string, dirpath);
 
       if (owner != (uid_t) -1 && group != (gid_t) -1)
        {
-         if (chown (dirpath, owner, group)
+         if (chown (basename_dir, owner, group)
 #ifdef AFS
              && errno != EPERM
 #endif
              )
            {
-             error (0, errno, "%s", dirpath);
+             error (0, errno, "cannot chown %s", dirpath);
              retval = 1;
            }
          /* chown may have turned off some permission bits we wanted.  */
-         if ((mode & 07000) != 0 && chmod (dirpath, mode))
+         if ((mode & 07000) != 0 && chmod (basename_dir, mode))
            {
-             error (0, errno, "%s", dirpath);
+             error (0, errno, "cannot chmod %s", dirpath);
              retval = 1;
            }
        }
 
+      CLEANUP_CWD;
+
       /* If the mode for leading directories didn't include owner "wx"
         privileges, we have to reset their protections to the correct
         value.  */
@@ -263,10 +331,11 @@ make_path (argpath, mode, parent_mode, owner, group, preserve_existing,
     {
       /* We get here if the entire path already exists.  */
 
+      const char *dirpath = argpath;
+
       if (!S_ISDIR (stats.st_mode))
        {
          error (0, 0, "`%s' exists but is not a directory", dirpath);
-         umask (oldmask);
          return 1;
        }
 
@@ -296,6 +365,5 @@ make_path (argpath, mode, parent_mode, owner, group, preserve_existing,
        }
     }
 
-  umask (oldmask);
   return retval;
 }