src/port/pgmkdirp.c - master - githubmirror/postgres

src/port/pgmkdirp.c
169 строк5 KB
Tom Lane
Make pg_mkdir_p() tolerant of a concurrent directory creation.
19 июн 2026, 19:52
19 июн 2026, 19:52f25a07b
/*
 * This is adapted from FreeBSD's src/bin/mkdir/mkdir.c, which bears
 * the following copyright notice:
 *
 * Copyright (c) 1983, 1992, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *	  notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *	  notice, this list of conditions and the following disclaimer in the
 *	  documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *	  may be used to endorse or promote products derived from this software
 *	  without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "c.h"

#include <sys/stat.h>


/*
 * pg_mkdir_p --- create a directory and, if necessary, parent directories
 *
 * This is equivalent to "mkdir -p" except we don't complain if the target
 * directory already exists.
 *
 * We assume the path is in canonical form, i.e., uses / as the separator.
 *
 * omode is the file permissions bits for the target directory.  Note that any
 * parent directories that have to be created get permissions according to the
 * prevailing umask, but with u+wx forced on to ensure we can create there.
 * (We declare omode as int, not mode_t, to minimize dependencies for port.h.)
 *
 * Returns 0 on success, -1 (with errno set) on failure.
 *
 * Note that on failure, the path arg has been modified to show the particular
 * directory level we had problems with.
 */
int
pg_mkdir_p(char *path, int omode)
{
	mode_t		numask,
				oumask;
	int			last,
				retval;
	char	   *p;

	retval = 0;
	p = path;

#ifdef WIN32
	/* skip network and drive specifiers for win32 */
	if (strlen(p) >= 2)
	{
		if (p[0] == '/' && p[1] == '/')
		{
			/* network drive */
			p = strchr(p + 2, '/');
			if (p == NULL)
			{
				errno = EINVAL;
				return -1;
			}
		}
		else if (p[1] == ':' &&
				 ((p[0] >= 'a' && p[0] <= 'z') ||
				  (p[0] >= 'A' && p[0] <= 'Z')))
		{
			/* local drive */
			p += 2;
		}
	}
#endif

	/*
	 * POSIX 1003.2: For each dir operand that does not name an existing
	 * directory, effects equivalent to those caused by the following command
	 * shall occur:
	 *
	 * mkdir -p -m $(umask -S),u+wx $(dirname dir) && mkdir [-m mode] dir
	 *
	 * We change the user's umask and then restore it, instead of doing
	 * chmod's.  Note we assume umask() can't change errno.
	 */
	oumask = umask(0);
	numask = oumask & ~(S_IWUSR | S_IXUSR);
	(void) umask(numask);

	if (p[0] == '/')			/* Skip leading '/'. */
		++p;
	for (last = 0; !last; ++p)
	{
		if (p[0] == '\0')
			last = 1;
		else if (p[0] != '/')
			continue;
		*p = '\0';
		if (!last && p[1] == '\0')
			last = 1;

		if (last)
			(void) umask(oumask);

		if (mkdir(path, last ? omode : S_IRWXU | S_IRWXG | S_IRWXO) < 0)
		{
			/*
			 * If we got EEXIST because there's already a directory there,
			 * don't complain.
			 */
#ifndef WIN32
			int			save_errno = errno;
			struct stat sb;

			if (save_errno != EEXIST ||
				stat(path, &sb) != 0 ||
				!S_ISDIR(sb.st_mode))
			{
				/* Don't let stat replace mkdir's errno */
				errno = save_errno;
				retval = -1;
				break;
			}
#else							/* WIN32 */
			/*
			 * On Windows, stat() opens a handle and can transiently fail on a
			 * directory another process is concurrently creating.  Probe with
			 * a path-based attribute query instead: it requests only
			 * FILE_READ_ATTRIBUTES and is exempt from share-mode denial, so
			 * it reliably sees a concurrently-created directory.  We assume
			 * GetFileAttributes() won't change errno.
			 */
			DWORD		attr = GetFileAttributes(path);

			if (errno != EEXIST ||
				attr == INVALID_FILE_ATTRIBUTES ||
				!(attr & FILE_ATTRIBUTE_DIRECTORY))
			{
				retval = -1;
				break;
			}
#endif							/* WIN32 */
		}

		if (!last)
			*p = '/';
	}

	/* ensure we restored umask */
	(void) umask(oumask);

	return retval;
}