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git/builtin/gc.c
Jeff King 076aa2cbda tempfile: auto-allocate tempfiles on heap 
The previous commit taught the tempfile code to give up
ownership over tempfiles that have been renamed or deleted.
That makes it possible to use a stack variable like this:

  struct tempfile t;

  create_tempfile(&t, ...);
  ...
  if (!err)
          rename_tempfile(&t, ...);
  else
          delete_tempfile(&t);

But doing it this way has a high potential for creating
memory errors. The tempfile we pass to create_tempfile()
ends up on a global linked list, and it's not safe for it to
go out of scope until we've called one of those two
deactivation functions.

Imagine that we add an early return from the function that
forgets to call delete_tempfile(). With a static or heap
tempfile variable, the worst case is that the tempfile hangs
around until the program exits (and some functions like
setup_shallow_temporary rely on this intentionally, creating
a tempfile and then leaving it for later cleanup).

But with a stack variable as above, this is a serious memory
error: the variable goes out of scope and may be filled with
garbage by the time the tempfile code looks at it.  Let's
see if we can make it harder to get this wrong.

Since many callers need to allocate arbitrary numbers of
tempfiles, we can't rely on static storage as a general
solution. So we need to turn to the heap. We could just ask
all callers to pass us a heap variable, but that puts the
burden on them to call free() at the right time.

Instead, let's have the tempfile code handle the heap
allocation _and_ the deallocation (when the tempfile is
deactivated and removed from the list).

This changes the return value of all of the creation
functions. For the cleanup functions (delete and rename),
we'll add one extra bit of safety: instead of taking a
tempfile pointer, we'll take a pointer-to-pointer and set it
to NULL after freeing the object. This makes it safe to
double-call functions like delete_tempfile(), as the second
call treats the NULL input as a noop. Several callsites
follow this pattern.

The resulting patch does have a fair bit of noise, as each
caller needs to be converted to handle:

  1. Storing a pointer instead of the struct itself.

  2. Passing the pointer instead of taking the struct
     address.

  3. Handling a "struct tempfile *" return instead of a file
     descriptor.

We could play games to make this less noisy. For example, by
defining the tempfile like this:

  struct tempfile {
	struct heap_allocated_part_of_tempfile {
                int fd;
                ...etc
        } *actual_data;
  }

Callers would continue to have a "struct tempfile", and it
would be "active" only when the inner pointer was non-NULL.
But that just makes things more awkward in the long run.
There aren't that many callers, so we can simply bite
the bullet and adjust all of them. And the compiler makes it
easy for us to find them all.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-09-06 17:19:54 +09:00

489 lines
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/*
* git gc builtin command
*
* Cleanup unreachable files and optimize the repository.
*
* Copyright (c) 2007 James Bowes
*
* Based on git-gc.sh, which is
*
* Copyright (c) 2006 Shawn O. Pearce
*/
#include "builtin.h"
#include "config.h"
#include "tempfile.h"
#include "lockfile.h"
#include "parse-options.h"
#include "run-command.h"
#include "sigchain.h"
#include "argv-array.h"
#include "commit.h"
#include "packfile.h"
#define FAILED_RUN "failed to run %s"
static const char * const builtin_gc_usage[] = {
N_("git gc [<options>]"),
NULL
};
static int pack_refs = 1;
static int prune_reflogs = 1;
static int aggressive_depth = 50;
static int aggressive_window = 250;
static int gc_auto_threshold = 6700;
static int gc_auto_pack_limit = 50;
static int detach_auto = 1;
static timestamp_t gc_log_expire_time;
static const char *gc_log_expire = "1.day.ago";
static const char *prune_expire = "2.weeks.ago";
static const char *prune_worktrees_expire = "3.months.ago";
static struct argv_array pack_refs_cmd = ARGV_ARRAY_INIT;
static struct argv_array reflog = ARGV_ARRAY_INIT;
static struct argv_array repack = ARGV_ARRAY_INIT;
static struct argv_array prune = ARGV_ARRAY_INIT;
static struct argv_array prune_worktrees = ARGV_ARRAY_INIT;
static struct argv_array rerere = ARGV_ARRAY_INIT;
static struct tempfile *pidfile;
static struct lock_file log_lock;
static struct string_list pack_garbage = STRING_LIST_INIT_DUP;
static void clean_pack_garbage(void)
{
int i;
for (i = 0; i < pack_garbage.nr; i++)
unlink_or_warn(pack_garbage.items[i].string);
string_list_clear(&pack_garbage, 0);
}
static void report_pack_garbage(unsigned seen_bits, const char *path)
{
if (seen_bits == PACKDIR_FILE_IDX)
string_list_append(&pack_garbage, path);
}
static void process_log_file(void)
{
struct stat st;
if (fstat(get_lock_file_fd(&log_lock), &st)) {
/*
* Perhaps there was an i/o error or another
* unlikely situation. Try to make a note of
* this in gc.log along with any existing
* messages.
*/
int saved_errno = errno;
fprintf(stderr, _("Failed to fstat %s: %s"),
get_tempfile_path(log_lock.tempfile),
strerror(saved_errno));
fflush(stderr);
commit_lock_file(&log_lock);
errno = saved_errno;
} else if (st.st_size) {
/* There was some error recorded in the lock file */
commit_lock_file(&log_lock);
} else {
/* No error, clean up any old gc.log */
unlink(git_path("gc.log"));
rollback_lock_file(&log_lock);
}
}
static void process_log_file_at_exit(void)
{
fflush(stderr);
process_log_file();
}
static void process_log_file_on_signal(int signo)
{
process_log_file();
sigchain_pop(signo);
raise(signo);
}
static void gc_config(void)
{
const char *value;
if (!git_config_get_value("gc.packrefs", &value)) {
if (value && !strcmp(value, "notbare"))
pack_refs = -1;
else
pack_refs = git_config_bool("gc.packrefs", value);
}
git_config_get_int("gc.aggressivewindow", &aggressive_window);
git_config_get_int("gc.aggressivedepth", &aggressive_depth);
git_config_get_int("gc.auto", &gc_auto_threshold);
git_config_get_int("gc.autopacklimit", &gc_auto_pack_limit);
git_config_get_bool("gc.autodetach", &detach_auto);
git_config_get_expiry("gc.pruneexpire", &prune_expire);
git_config_get_expiry("gc.worktreepruneexpire", &prune_worktrees_expire);
git_config_get_expiry("gc.logexpiry", &gc_log_expire);
git_config(git_default_config, NULL);
}
static int too_many_loose_objects(void)
{
/*
* Quickly check if a "gc" is needed, by estimating how
* many loose objects there are. Because SHA-1 is evenly
* distributed, we can check only one and get a reasonable
* estimate.
*/
DIR *dir;
struct dirent *ent;
int auto_threshold;
int num_loose = 0;
int needed = 0;
if (gc_auto_threshold <= 0)
return 0;
dir = opendir(git_path("objects/17"));
if (!dir)
return 0;
auto_threshold = DIV_ROUND_UP(gc_auto_threshold, 256);
while ((ent = readdir(dir)) != NULL) {
if (strspn(ent->d_name, "0123456789abcdef") != 38 ||
ent->d_name[38] != '\0')
continue;
if (++num_loose > auto_threshold) {
needed = 1;
break;
}
}
closedir(dir);
return needed;
}
static int too_many_packs(void)
{
struct packed_git *p;
int cnt;
if (gc_auto_pack_limit <= 0)
return 0;
prepare_packed_git();
for (cnt = 0, p = packed_git; p; p = p->next) {
if (!p->pack_local)
continue;
if (p->pack_keep)
continue;
/*
* Perhaps check the size of the pack and count only
* very small ones here?
*/
cnt++;
}
return gc_auto_pack_limit < cnt;
}
static void add_repack_all_option(void)
{
if (prune_expire && !strcmp(prune_expire, "now"))
argv_array_push(&repack, "-a");
else {
argv_array_push(&repack, "-A");
if (prune_expire)
argv_array_pushf(&repack, "--unpack-unreachable=%s", prune_expire);
}
}
static void add_repack_incremental_option(void)
{
argv_array_push(&repack, "--no-write-bitmap-index");
}
static int need_to_gc(void)
{
/*
* Setting gc.auto to 0 or negative can disable the
* automatic gc.
*/
if (gc_auto_threshold <= 0)
return 0;
/*
* If there are too many loose objects, but not too many
* packs, we run "repack -d -l". If there are too many packs,
* we run "repack -A -d -l". Otherwise we tell the caller
* there is no need.
*/
if (too_many_packs())
add_repack_all_option();
else if (too_many_loose_objects())
add_repack_incremental_option();
else
return 0;
if (run_hook_le(NULL, "pre-auto-gc", NULL))
return 0;
return 1;
}
/* return NULL on success, else hostname running the gc */
static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
{
static struct lock_file lock;
char my_host[HOST_NAME_MAX + 1];
struct strbuf sb = STRBUF_INIT;
struct stat st;
uintmax_t pid;
FILE *fp;
int fd;
char *pidfile_path;
if (is_tempfile_active(pidfile))
/* already locked */
return NULL;
if (xgethostname(my_host, sizeof(my_host)))
xsnprintf(my_host, sizeof(my_host), "unknown");
pidfile_path = git_pathdup("gc.pid");
fd = hold_lock_file_for_update(&lock, pidfile_path,
LOCK_DIE_ON_ERROR);
if (!force) {
static char locking_host[HOST_NAME_MAX + 1];
static char *scan_fmt;
int should_exit;
if (!scan_fmt)
scan_fmt = xstrfmt("%s %%%dc", "%"SCNuMAX, HOST_NAME_MAX);
fp = fopen(pidfile_path, "r");
memset(locking_host, 0, sizeof(locking_host));
should_exit =
fp != NULL &&
!fstat(fileno(fp), &st) &&
/*
* 12 hour limit is very generous as gc should
* never take that long. On the other hand we
* don't really need a strict limit here,
* running gc --auto one day late is not a big
* problem. --force can be used in manual gc
* after the user verifies that no gc is
* running.
*/
time(NULL) - st.st_mtime <= 12 * 3600 &&
fscanf(fp, scan_fmt, &pid, locking_host) == 2 &&
/* be gentle to concurrent "gc" on remote hosts */
(strcmp(locking_host, my_host) || !kill(pid, 0) || errno == EPERM);
if (fp != NULL)
fclose(fp);
if (should_exit) {
if (fd >= 0)
rollback_lock_file(&lock);
*ret_pid = pid;
free(pidfile_path);
return locking_host;
}
}
strbuf_addf(&sb, "%"PRIuMAX" %s",
(uintmax_t) getpid(), my_host);
write_in_full(fd, sb.buf, sb.len);
strbuf_release(&sb);
commit_lock_file(&lock);
pidfile = register_tempfile(pidfile_path);
free(pidfile_path);
return NULL;
}
static int report_last_gc_error(void)
{
struct strbuf sb = STRBUF_INIT;
int ret = 0;
struct stat st;
char *gc_log_path = git_pathdup("gc.log");
if (stat(gc_log_path, &st)) {
if (errno == ENOENT)
goto done;
ret = error_errno(_("Can't stat %s"), gc_log_path);
goto done;
}
if (st.st_mtime < gc_log_expire_time)
goto done;
ret = strbuf_read_file(&sb, gc_log_path, 0);
if (ret > 0)
ret = error(_("The last gc run reported the following. "
"Please correct the root cause\n"
"and remove %s.\n"
"Automatic cleanup will not be performed "
"until the file is removed.\n\n"
"%s"),
gc_log_path, sb.buf);
strbuf_release(&sb);
done:
free(gc_log_path);
return ret;
}
static int gc_before_repack(void)
{
if (pack_refs && run_command_v_opt(pack_refs_cmd.argv, RUN_GIT_CMD))
return error(FAILED_RUN, pack_refs_cmd.argv[0]);
if (prune_reflogs && run_command_v_opt(reflog.argv, RUN_GIT_CMD))
return error(FAILED_RUN, reflog.argv[0]);
pack_refs = 0;
prune_reflogs = 0;
return 0;
}
int cmd_gc(int argc, const char **argv, const char *prefix)
{
int aggressive = 0;
int auto_gc = 0;
int quiet = 0;
int force = 0;
const char *name;
pid_t pid;
int daemonized = 0;
struct option builtin_gc_options[] = {
OPT__QUIET(&quiet, N_("suppress progress reporting")),
{ OPTION_STRING, 0, "prune", &prune_expire, N_("date"),
N_("prune unreferenced objects"),
PARSE_OPT_OPTARG, NULL, (intptr_t)prune_expire },
OPT_BOOL(0, "aggressive", &aggressive, N_("be more thorough (increased runtime)")),
OPT_BOOL(0, "auto", &auto_gc, N_("enable auto-gc mode")),
OPT_BOOL(0, "force", &force, N_("force running gc even if there may be another gc running")),
OPT_END()
};
if (argc == 2 && !strcmp(argv[1], "-h"))
usage_with_options(builtin_gc_usage, builtin_gc_options);
argv_array_pushl(&pack_refs_cmd, "pack-refs", "--all", "--prune", NULL);
argv_array_pushl(&reflog, "reflog", "expire", "--all", NULL);
argv_array_pushl(&repack, "repack", "-d", "-l", NULL);
argv_array_pushl(&prune, "prune", "--expire", NULL);
argv_array_pushl(&prune_worktrees, "worktree", "prune", "--expire", NULL);
argv_array_pushl(&rerere, "rerere", "gc", NULL);
/* default expiry time, overwritten in gc_config */
gc_config();
if (parse_expiry_date(gc_log_expire, &gc_log_expire_time))
die(_("Failed to parse gc.logexpiry value %s"), gc_log_expire);
if (pack_refs < 0)
pack_refs = !is_bare_repository();
argc = parse_options(argc, argv, prefix, builtin_gc_options,
builtin_gc_usage, 0);
if (argc > 0)
usage_with_options(builtin_gc_usage, builtin_gc_options);
if (aggressive) {
argv_array_push(&repack, "-f");
if (aggressive_depth > 0)
argv_array_pushf(&repack, "--depth=%d", aggressive_depth);
if (aggressive_window > 0)
argv_array_pushf(&repack, "--window=%d", aggressive_window);
}
if (quiet)
argv_array_push(&repack, "-q");
if (auto_gc) {
/*
* Auto-gc should be least intrusive as possible.
*/
if (!need_to_gc())
return 0;
if (!quiet) {
if (detach_auto)
fprintf(stderr, _("Auto packing the repository in background for optimum performance.\n"));
else
fprintf(stderr, _("Auto packing the repository for optimum performance.\n"));
fprintf(stderr, _("See \"git help gc\" for manual housekeeping.\n"));
}
if (detach_auto) {
if (report_last_gc_error())
return -1;
if (lock_repo_for_gc(force, &pid))
return 0;
if (gc_before_repack())
return -1;
delete_tempfile(&pidfile);
/*
* failure to daemonize is ok, we'll continue
* in foreground
*/
daemonized = !daemonize();
}
} else
add_repack_all_option();
name = lock_repo_for_gc(force, &pid);
if (name) {
if (auto_gc)
return 0; /* be quiet on --auto */
die(_("gc is already running on machine '%s' pid %"PRIuMAX" (use --force if not)"),
name, (uintmax_t)pid);
}
if (daemonized) {
hold_lock_file_for_update(&log_lock,
git_path("gc.log"),
LOCK_DIE_ON_ERROR);
dup2(get_lock_file_fd(&log_lock), 2);
sigchain_push_common(process_log_file_on_signal);
atexit(process_log_file_at_exit);
}
if (gc_before_repack())
return -1;
if (!repository_format_precious_objects) {
if (run_command_v_opt(repack.argv, RUN_GIT_CMD))
return error(FAILED_RUN, repack.argv[0]);
if (prune_expire) {
argv_array_push(&prune, prune_expire);
if (quiet)
argv_array_push(&prune, "--no-progress");
if (run_command_v_opt(prune.argv, RUN_GIT_CMD))
return error(FAILED_RUN, prune.argv[0]);
}
}
if (prune_worktrees_expire) {
argv_array_push(&prune_worktrees, prune_worktrees_expire);
if (run_command_v_opt(prune_worktrees.argv, RUN_GIT_CMD))
return error(FAILED_RUN, prune_worktrees.argv[0]);
}
if (run_command_v_opt(rerere.argv, RUN_GIT_CMD))
return error(FAILED_RUN, rerere.argv[0]);
report_garbage = report_pack_garbage;
reprepare_packed_git();
if (pack_garbage.nr > 0)
clean_pack_garbage();
if (auto_gc && too_many_loose_objects())
warning(_("There are too many unreachable loose objects; "
"run 'git prune' to remove them."));
if (!daemonized)
unlink(git_path("gc.log"));
return 0;
}
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