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authorAndrew Tridgell <tridge@samba.org>2005-07-25 04:03:01 +0000
committerGerald (Jerry) Carter <jerry@samba.org>2007-10-10 13:30:01 -0500
commitf92c000fc903803e1c2817dd407974ec44390593 (patch)
treed807a16484c93d45f463e5c23d1750a1c1ac5a08 /source4/lib/replace/repdir/repdir.c
parentfc9ffba41332b5755ede3683208ec989d30fdcd0 (diff)
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r8746: replace opendir/readdir/telldir/seekdir/closedir on systems where they
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 e1bf7c4279fbc03a52497d24cea375e75059cba1)
Diffstat (limited to 'source4/lib/replace/repdir/repdir.c')
-rw-r--r--source4/lib/replace/repdir/repdir.c138
1 files changed, 138 insertions, 0 deletions
diff --git a/source4/lib/replace/repdir/repdir.c b/source4/lib/replace/repdir/repdir.c
new file mode 100644
index 0000000000..9c81355c68
--- /dev/null
+++ b/source4/lib/replace/repdir/repdir.c
@@ -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;
+}
+