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- Committer: Bazaar Package Importer
- Author(s): Robert Collins
- Date: 2005-05-28 17:27:21 UTC
- Revision ID: james.westby@ubuntu.com-20050528172721-jj5vkjr77mx2awg7
Tags: upstream-0.4
Import upstream version 0.4
- files added:
- fl-cow
- test
added
removed
fl-cow/fl-cow.c
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/*
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* FL-COW by Davide Libenzi ( File Links Copy On Write )
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* Copyright (C) 2003 Davide Libenzi
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* Davide Libenzi <davidel@xmailserver.org>
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*
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*/
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#include <stdarg.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <sys/types.h>
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#include <sys/time.h>
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#include <sys/stat.h>
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#include <sys/uio.h>
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#include <sys/mman.h>
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#include <sys/file.h>
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#include <sys/ioctl.h>
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#include <stdio.h>
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#include <time.h>
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#include <errno.h>
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#include <dlfcn.h>
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#ifdef ENABLE_DEBUG
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#define DPRINTF(format, args...) fprintf(stderr, format, ## args)
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#else
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#define DPRINTF(format, args...)
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#endif
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#ifndef RTLD_NEXT
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#define RTLD_NEXT ((void *) -1L)
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#endif
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#define REAL_LIBC RTLD_NEXT
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#define FLCLOW_MAXPATH 512
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int open(const char *name, int flags, ...) __attribute__ ((weak, alias("__libc_open")));
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int __open(const char *name, int flags, ...) __attribute__ ((weak, alias("__libc_open")));
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int open64(const char *name, int flags, ...) __attribute__ ((weak, alias("__libc_open64")));
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int __open64(const char *name, int flags, ...) __attribute__ ((weak, alias("__libc_open64")));
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static int cow_name(const char *name) {
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int nlen, len;
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char const *home, *excld, *next;
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char fpath[FLCLOW_MAXPATH];
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nlen = strlen(name);
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if (*name != '/' && nlen < sizeof(fpath) - 1) {
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if (name[0] == '~' && name[1] == '/') {
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if ((home = getenv("HOME")) != NULL) {
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strncpy(fpath, home, sizeof(fpath) - 1);
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name += 2;
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nlen -= 2;
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} else
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fpath[0] = '\0';
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} else {
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if (!getcwd(fpath, sizeof(fpath) - 1 - nlen))
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fpath[0] = '\0';
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}
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if ((len = strlen(fpath)) + nlen + 2 < sizeof(fpath)) {
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if (len && fpath[len - 1] != '/')
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fpath[len++] = '/';
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memcpy(fpath + len, name, nlen + 1);
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name = fpath;
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nlen += len;
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}
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}
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for (excld = getenv("FLCOW_PATH"); excld;) {
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if (!(next = strchr(excld, ':')))
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len = strlen(excld);
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else
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len = next - excld;
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if (len && !strncmp(excld, name, len))
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return 1;
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excld = next ? next + 1: NULL;
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}
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return 0;
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}
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static int do_cow_name(const char *name, int (*open_proc)(const char *, int, mode_t)) {
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int nfd, sfd;
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void *addr;
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struct stat stb;
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char fpath[FLCLOW_MAXPATH];
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if ((sfd = open_proc(name, O_RDONLY, 0)) == -1)
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return -1;
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if (fstat(sfd, &stb)) {
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close(sfd);
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return -1;
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}
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snprintf(fpath, sizeof(fpath) - 1, "%s,,+++", name);
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if ((nfd = open_proc(fpath, O_CREAT | O_EXCL | O_WRONLY, stb.st_mode)) == -1) {
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close(sfd);
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return -1;
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}
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if ((addr = mmap(NULL, stb.st_size, PROT_READ, MAP_PRIVATE,
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sfd, 0)) == MAP_FAILED) {
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close(nfd);
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unlink(fpath);
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close(sfd);
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return -1;
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}
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if (write(nfd, addr, stb.st_size) != stb.st_size) {
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munmap(addr, stb.st_size);
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close(nfd);
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unlink(fpath);
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close(sfd);
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return -1;
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}
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munmap(addr, stb.st_size);
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close(sfd);
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fchown(nfd, stb.st_uid, stb.st_gid);
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close(nfd);
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if (unlink(name)) {
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unlink(fpath);
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return -1;
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}
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rename(fpath, name);
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return 0;
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}
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static int do_generic_open(const char *name, int flags, mode_t mode,
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int (*open_proc)(const char *, int, mode_t)) {
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struct stat stb;
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if ((flags & O_RDWR || flags & O_WRONLY) && cow_name(name) &&
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!stat(name, &stb) && S_ISREG(stb.st_mode) && stb.st_nlink > 1) {
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DPRINTF("COWing %s\n", name);
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if (do_cow_name(name, open_proc) < 0) {
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DPRINTF("COWing %s failed !\n", name);
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} else {
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DPRINTF("COWing %s succeed\n", name);
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}
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}
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return open_proc(name, flags, mode);
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}
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int __libc_open64(const char *name, int flags, ...) {
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static int (*func_open)(const char *, int, mode_t) = NULL;
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va_list args;
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mode_t mode;
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if (!func_open)
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func_open = (int (*)(const char *, int, mode_t)) dlsym(REAL_LIBC, "__libc_open64");
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va_start(args, flags);
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mode = va_arg(args, mode_t);
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va_end(args);
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DPRINTF("open64(%s, 0x%x, 0x%x)\n", name, flags, mode);
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return do_generic_open(name, flags, mode, func_open);
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}
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int __libc_open(const char *name, int flags, ...) {
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static int (*func_open)(const char *, int, mode_t) = NULL;
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va_list args;
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mode_t mode;
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if (!func_open)
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func_open = (int (*)(const char *, int, mode_t)) dlsym(REAL_LIBC, "__libc_open");
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va_start(args, flags);
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mode = va_arg(args, mode_t);
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va_end(args);
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DPRINTF("open(%s, 0x%x, 0x%x)\n", name, flags, mode);
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return do_generic_open(name, flags, mode, func_open);
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}
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