git/lockfile.c
Junio C Hamano 19a249ba83 Merge branch 'rs/ref-transaction-0'
Early part of the "ref transaction" topic.

* rs/ref-transaction-0:
  refs.c: change ref_transaction_update() to do error checking and return status
  refs.c: remove the onerr argument to ref_transaction_commit
  update-ref: use err argument to get error from ref_transaction_commit
  refs.c: make update_ref_write update a strbuf on failure
  refs.c: make ref_update_reject_duplicates take a strbuf argument for errors
  refs.c: log_ref_write should try to return meaningful errno
  refs.c: make resolve_ref_unsafe set errno to something meaningful on error
  refs.c: commit_packed_refs to return a meaningful errno on failure
  refs.c: make remove_empty_directories always set errno to something sane
  refs.c: verify_lock should set errno to something meaningful
  refs.c: make sure log_ref_setup returns a meaningful errno
  refs.c: add an err argument to repack_without_refs
  lockfile.c: make lock_file return a meaningful errno on failurei
  lockfile.c: add a new public function unable_to_lock_message
  refs.c: add a strbuf argument to ref_transaction_commit for error logging
  refs.c: allow passing NULL to ref_transaction_free
  refs.c: constify the sha arguments for ref_transaction_create|delete|update
  refs.c: ref_transaction_commit should not free the transaction
  refs.c: remove ref_transaction_rollback
2014-07-21 11:18:37 -07:00

272 lines
6.1 KiB
C

/*
* Copyright (c) 2005, Junio C Hamano
*/
#include "cache.h"
#include "sigchain.h"
static struct lock_file *lock_file_list;
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_or_warn(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;
}
/* Make sure errno contains a meaningful value on error */
static int lock_file(struct lock_file *lk, const char *path, int flags)
{
/*
* subtract 5 from size to make sure there's room for adding
* ".lock" for the lock file name
*/
static const size_t max_path_len = sizeof(lk->filename) - 5;
if (strlen(path) >= max_path_len) {
errno = ENAMETOOLONG;
return -1;
}
strcpy(lk->filename, path);
if (!(flags & LOCK_NODEREF))
resolve_symlink(lk->filename, max_path_len);
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)) {
int save_errno = errno;
error("cannot fix permission bits on %s",
lk->filename);
errno = save_errno;
return -1;
}
}
else
lk->filename[0] = 0;
return lk->fd;
}
void unable_to_lock_message(const char *path, int err, struct strbuf *buf)
{
if (err == EEXIST) {
strbuf_addf(buf, "Unable to create '%s.lock': %s.\n\n"
"If no other git process is currently running, this probably means a\n"
"git process crashed in this repository earlier. Make sure no other git\n"
"process is running and remove the file manually to continue.",
absolute_path(path), strerror(err));
} else
strbuf_addf(buf, "Unable to create '%s.lock': %s",
absolute_path(path), strerror(err));
}
int unable_to_lock_error(const char *path, int err)
{
struct strbuf buf = STRBUF_INIT;
unable_to_lock_message(path, err, &buf);
error("%s", buf.buf);
strbuf_release(&buf);
return -1;
}
NORETURN void unable_to_lock_index_die(const char *path, int err)
{
struct strbuf buf = STRBUF_INIT;
unable_to_lock_message(path, err, &buf);
die("%s", buf.buf);
}
/* This should return a meaningful errno on failure */
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))
unable_to_lock_index_die(path, 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)
unable_to_lock_index_die(path, 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 rollback_lock_file(struct lock_file *lk)
{
if (lk->filename[0]) {
if (lk->fd >= 0)
close(lk->fd);
unlink_or_warn(lk->filename);
}
lk->filename[0] = 0;
}