git/lockfile.c
Jeff King 57b235a4bc refactor signal handling for cleanup functions
The current code is very inconsistent about which signals
are caught for doing cleanup of temporary files and lock
files. Some callsites checked only SIGINT, while others
checked a variety of death-dealing signals.

This patch factors out those signals to a single function,
and then calls it everywhere. For some sites, that means
this is a simple clean up. For others, it is an improvement
in that they will now properly clean themselves up after a
larger variety of signals.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2009-01-21 22:46:53 -08:00

252 lines
5.4 KiB
C

/*
* Copyright (c) 2005, Junio C Hamano
*/
#include "cache.h"
#include "sigchain.h"
static struct lock_file *lock_file_list;
static const char *alternate_index_output;
static void remove_lock_file(void)
{
pid_t me = getpid();
while (lock_file_list) {
if (lock_file_list->owner == me &&
lock_file_list->filename[0]) {
if (lock_file_list->fd >= 0)
close(lock_file_list->fd);
unlink(lock_file_list->filename);
}
lock_file_list = lock_file_list->next;
}
}
static void remove_lock_file_on_signal(int signo)
{
remove_lock_file();
sigchain_pop(signo);
raise(signo);
}
/*
* p = absolute or relative path name
*
* Return a pointer into p showing the beginning of the last path name
* element. If p is empty or the root directory ("/"), just return p.
*/
static char *last_path_elm(char *p)
{
/* r starts pointing to null at the end of the string */
char *r = strchr(p, '\0');
if (r == p)
return p; /* just return empty string */
r--; /* back up to last non-null character */
/* back up past trailing slashes, if any */
while (r > p && *r == '/')
r--;
/*
* then go backwards until I hit a slash, or the beginning of
* the string
*/
while (r > p && *(r-1) != '/')
r--;
return r;
}
/* We allow "recursive" symbolic links. Only within reason, though */
#define MAXDEPTH 5
/*
* p = path that may be a symlink
* s = full size of p
*
* If p is a symlink, attempt to overwrite p with a path to the real
* file or directory (which may or may not exist), following a chain of
* symlinks if necessary. Otherwise, leave p unmodified.
*
* This is a best-effort routine. If an error occurs, p will either be
* left unmodified or will name a different symlink in a symlink chain
* that started with p's initial contents.
*
* Always returns p.
*/
static char *resolve_symlink(char *p, size_t s)
{
int depth = MAXDEPTH;
while (depth--) {
char link[PATH_MAX];
int link_len = readlink(p, link, sizeof(link));
if (link_len < 0) {
/* not a symlink anymore */
return p;
}
else if (link_len < sizeof(link))
/* readlink() never null-terminates */
link[link_len] = '\0';
else {
warning("%s: symlink too long", p);
return p;
}
if (is_absolute_path(link)) {
/* absolute path simply replaces p */
if (link_len < s)
strcpy(p, link);
else {
warning("%s: symlink too long", p);
return p;
}
} else {
/*
* link is a relative path, so I must replace the
* last element of p with it.
*/
char *r = (char*)last_path_elm(p);
if (r - p + link_len < s)
strcpy(r, link);
else {
warning("%s: symlink too long", p);
return p;
}
}
}
return p;
}
static int lock_file(struct lock_file *lk, const char *path, int flags)
{
if (strlen(path) >= sizeof(lk->filename))
return -1;
strcpy(lk->filename, path);
/*
* subtract 5 from size to make sure there's room for adding
* ".lock" for the lock file name
*/
if (!(flags & LOCK_NODEREF))
resolve_symlink(lk->filename, sizeof(lk->filename)-5);
strcat(lk->filename, ".lock");
lk->fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666);
if (0 <= lk->fd) {
if (!lock_file_list) {
sigchain_push_common(remove_lock_file_on_signal);
atexit(remove_lock_file);
}
lk->owner = getpid();
if (!lk->on_list) {
lk->next = lock_file_list;
lock_file_list = lk;
lk->on_list = 1;
}
if (adjust_shared_perm(lk->filename))
return error("cannot fix permission bits on %s",
lk->filename);
}
else
lk->filename[0] = 0;
return lk->fd;
}
int hold_lock_file_for_update(struct lock_file *lk, const char *path, int flags)
{
int fd = lock_file(lk, path, flags);
if (fd < 0 && (flags & LOCK_DIE_ON_ERROR))
die("unable to create '%s.lock': %s", path, strerror(errno));
return fd;
}
int hold_lock_file_for_append(struct lock_file *lk, const char *path, int flags)
{
int fd, orig_fd;
fd = lock_file(lk, path, flags);
if (fd < 0) {
if (flags & LOCK_DIE_ON_ERROR)
die("unable to create '%s.lock': %s", path, strerror(errno));
return fd;
}
orig_fd = open(path, O_RDONLY);
if (orig_fd < 0) {
if (errno != ENOENT) {
if (flags & LOCK_DIE_ON_ERROR)
die("cannot open '%s' for copying", path);
close(fd);
return error("cannot open '%s' for copying", path);
}
} else if (copy_fd(orig_fd, fd)) {
if (flags & LOCK_DIE_ON_ERROR)
exit(128);
close(fd);
return -1;
}
return fd;
}
int close_lock_file(struct lock_file *lk)
{
int fd = lk->fd;
lk->fd = -1;
return close(fd);
}
int commit_lock_file(struct lock_file *lk)
{
char result_file[PATH_MAX];
size_t i;
if (lk->fd >= 0 && close_lock_file(lk))
return -1;
strcpy(result_file, lk->filename);
i = strlen(result_file) - 5; /* .lock */
result_file[i] = 0;
if (rename(lk->filename, result_file))
return -1;
lk->filename[0] = 0;
return 0;
}
int hold_locked_index(struct lock_file *lk, int die_on_error)
{
return hold_lock_file_for_update(lk, get_index_file(),
die_on_error
? LOCK_DIE_ON_ERROR
: 0);
}
void set_alternate_index_output(const char *name)
{
alternate_index_output = name;
}
int commit_locked_index(struct lock_file *lk)
{
if (alternate_index_output) {
if (lk->fd >= 0 && close_lock_file(lk))
return -1;
if (rename(lk->filename, alternate_index_output))
return -1;
lk->filename[0] = 0;
return 0;
}
else
return commit_lock_file(lk);
}
void rollback_lock_file(struct lock_file *lk)
{
if (lk->filename[0]) {
if (lk->fd >= 0)
close(lk->fd);
unlink(lk->filename);
}
lk->filename[0] = 0;
}