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r8746: replace opendir/readdir/telldir/seekdir/closedir on systems where they

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are broken (apparently all BSD systems). This breakage leads to unlink
on files in an open directory causing a later seekdir to miss
files. The bug happens due to a block boundary bug in the BSD libc
implementation of these calls.

This replacement code also fixes a severe memory usage problem with
telldir that can cause closedir() to take an arbitrary amount of time.

I have reported the bug in readdir to Greg Lehey (a FreeBSD maintainer)
(This used to be commit e1bf7c4279)
This commit is contained in:
Andrew Tridgell 2005-07-25 04:03:01 +00:00 committed by Gerald (Jerry) Carter
parent fc9ffba413
commit f92c000fc9
5 changed files with 277 additions and 1 deletions
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110
source4/build/tests/os2_delete.c Normal file
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@ -0,0 +1,110 @@
/*
test readdir/unlink pattern that OS/2 uses
tridge@samba.org July 2005
*/
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <unistd.h>
#include <sys/types.h>
#include <dirent.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#ifdef REPLACE_READDIR
#include "lib/replace/repdir/repdir.h"
#endif
#define NUM_FILES 700
#define READDIR_SIZE 100
#define DELETE_SIZE 4
#define TESTDIR "test.dir"
#define FAILED() (fprintf(stderr, "Failed at %s:%d - %s\n", __FUNCTION__, __LINE__, strerror(errno)), exit(1), 1)
#ifndef MIN
#define MIN(a,b) ((a)<(b)?(a):(b))
#endif
static void cleanup(void)
{
/* I'm a lazy bastard */
system("rm -rf " TESTDIR);
mkdir(TESTDIR, 0700) == 0 || FAILED();
}
static void create_files()
{
int i;
for (i=0;i<NUM_FILES;i++) {
char fname[40];
sprintf(fname, TESTDIR "/test%u.txt", i);
close(open(fname, O_CREAT|O_RDWR, 0600)) == 0 || FAILED();
}
}
static int os2_delete(DIR *d)
{
off_t offsets[READDIR_SIZE];
int i, j;
struct dirent *de;
char names[READDIR_SIZE][30];
/* scan, remembering offsets */
for (i=0, de=readdir(d);
de && i < READDIR_SIZE;
de=readdir(d), i++) {
offsets[i] = telldir(d);
strcpy(names[i], de->d_name);
}
if (i == 0) {
return 0;
}
/* delete the first few */
for (j=0; j<MIN(i, DELETE_SIZE); j++) {
char fname[40];
sprintf(fname, TESTDIR "/%s", names[j]);
unlink(fname) == 0 || FAILED();
}
/* seek to just after the deletion */
seekdir(d, offsets[j-1]);
/* return number deleted */
return j;
}
int main(void)
{
int total_deleted = 0;
DIR *d;
struct dirent *de;
cleanup();
create_files();
d = opendir(TESTDIR);
/* skip past . and .. */
de = readdir(d);
strcmp(de->d_name, ".") == 0 || FAILED();
de = readdir(d);
strcmp(de->d_name, "..") == 0 || FAILED();
while (1) {
int n = os2_delete(d);
if (n == 0) break;
total_deleted += n;
}
closedir(d);
printf("Deleted %d files of %d\n", total_deleted, NUM_FILES);
rmdir(TESTDIR) == 0 || FAILED();
return 0;
}

1
source4/configure.in
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@ -11,6 +11,7 @@ AC_CONFIG_HEADER(include/config.h)
sinclude(build/m4/env.m4)
sinclude(build/m4/rewrite.m4)
sinclude(lib/replace/win32/config.m4)
sinclude(lib/replace/repdir/config.m4)
sinclude(heimdal_build/config.m4)
sinclude(lib/popt/config.m4)
sinclude(lib/iconv.m4)

12
source4/lib/replace/config.mk
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@ -1,9 +1,19 @@
##############################
# Start SUBSYSTEM REPLACE_READDIR
[SUBSYSTEM::REPLACE_READDIR]
ADD_OBJ_FILES = \
lib/replace/repdir/repdir.o
NOPROTO = YES
# End SUBSYSTEM REPLACE_READDIR
##############################
##############################
# Start SUBSYSTEM LIBREPLACE
[SUBSYSTEM::LIBREPLACE]
INIT_OBJ_FILES = lib/replace/replace.o
ADD_OBJ_FILES = \
lib/replace/snprintf.o
REQUIRED_SUBSYSTEMS = REPLACE_READDIR
# End SUBSYSTEM LIBREPLACE
##############################

17
source4/lib/replace/repdir/config.m4 Normal file
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@ -0,0 +1,17 @@
AC_CACHE_CHECK([for broken readdir],samba_cv_HAVE_BROKEN_READDIR,[
AC_TRY_RUN([#include "${srcdir-.}/build/tests/os2_delete.c"],
samba_cv_HAVE_BROKEN_READDIR=no,samba_cv_HAVE_BROKEN_READDIR=yes)])
if test x"$samba_cv_HAVE_BROKEN_READDIR" = x"yes"; then
AC_CACHE_CHECK([for replacing readdir],samba_cv_REPLACE_READDIR,[
AC_TRY_RUN([
#include "${srcdir-.}/lib/replace/repdir/repdir.c"
#include "${srcdir-.}/build/tests/os2_delete.c"],
samba_cv_REPLACE_READDIR=yes,samba_cv_REPLACE_READDIR=no)])
fi
SMB_SUBSYSTEM_ENABLE(REPLACE_READDIR, NO)
if test x"$samba_cv_REPLACE_READDIR" = x"yes"; then
AC_DEFINE(REPLACE_READDIR,1,[replace readdir])
SMB_SUBSYSTEM_ENABLE(REPLACE_READDIR, YES)
fi

138
source4/lib/replace/repdir/repdir.c Normal file
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@ -0,0 +1,138 @@
/*
Unix SMB/CIFS implementation.
Copyright (C) Andrew Tridgell 2005
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
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/*
a replacement for opendir/readdir/telldir/seekdir/closedir for BSD systems
This is needed because the existing directory handling in FreeBSD
and OpenBSD (and possibly NetBSD) doesn't correctly handle unlink()
on files in a directory where telldir() has been used. On a block
boundary it will occasionally miss a file when seekdir() is used to
return to a position previously recorded with telldir().
This also fixes a severe performance and memory usage problem with
telldir() on BSD systems. Each call to telldir() in BSD adds an
entry to a linked list, and those entries are cleaned up on
closedir(). This means with a large directory closedir() can take an
arbitrary amount of time, causing network timeouts as millions of
telldir() entries are freed
Note! This replacement code is not portable. It relies on getdents()
always leaving the file descriptor at a seek offset that is a
multiple of DIR_BUF_SIZE. If the code detects that this doesn't
happen then it will abort(). It also does not handle directories
with offsets larger than can be stored in a long,
This code is available under other free software licenses as
well. Contact the author.
*/
#include <stdlib.h>
#include <sys/stat.h>
#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
#include <fcntl.h>
#include <dirent.h>
#define DIR_BUF_BITS 9
#define DIR_BUF_SIZE (1<<DIR_BUF_BITS)
struct dir_buf {
int fd;
int nbytes, ofs;
off_t seekpos;
char buf[DIR_BUF_SIZE];
};
DIR *opendir(const char *dname)
{
struct dir_buf *d;
d = malloc(sizeof(*d));
if (d == NULL) {
errno = ENOMEM;
return NULL;
}
d->fd = open(dname, O_RDONLY);
if (d->fd == -1) {
free(d);
return NULL;
}
d->ofs = 0;
d->seekpos = 0;
d->nbytes = 0;
return (DIR *)d;
}
struct dirent *readdir(DIR *dir)
{
struct dir_buf *d = (struct dir_buf *)dir;
struct dirent *de;
if (d->ofs >= d->nbytes) {
d->seekpos = lseek(d->fd, 0, SEEK_CUR);
d->nbytes = getdents(d->fd, d->buf, DIR_BUF_SIZE);
d->ofs = 0;
}
if (d->ofs >= d->nbytes) {
return NULL;
}
de = (struct dirent *)&d->buf[d->ofs];
d->ofs += de->d_reclen;
return de;
}
long telldir(DIR *dir)
{
struct dir_buf *d = (struct dir_buf *)dir;
if (d->ofs >= d->nbytes) {
d->seekpos = lseek(d->fd, 0, SEEK_CUR);
d->ofs = 0;
d->nbytes = 0;
}
/* this relies on seekpos always being a multiple of
DIR_BUF_SIZE. Is that always true on BSD systems? */
if (d->seekpos & (DIR_BUF_SIZE-1)) {
abort();
}
return d->seekpos + d->ofs;
}
void seekdir(DIR *dir, long ofs)
{
struct dir_buf *d = (struct dir_buf *)dir;
d->seekpos = lseek(d->fd, ofs & ~(DIR_BUF_SIZE-1), SEEK_SET);
d->nbytes = getdents(d->fd, d->buf, DIR_BUF_SIZE);
d->ofs = 0;
while (d->ofs < (ofs & (DIR_BUF_SIZE-1))) {
if (readdir(dir) == NULL) break;
}
}
int closedir(DIR *dir)
{
struct dir_buf *d = (struct dir_buf *)dir;
int r = close(d->fd);
if (r != 0) {
return r;
}
free(d);
return 0;
}