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git/builtin/commit-graph.c
Taylor Blau f57a739691 midx: avoid opening multiple MIDXs when writing
Opening multiple instance of the same MIDX can lead to problems like two
separate packed_git structures which represent the same pack being added
to the repository's object store.

The above scenario can happen because prepare_midx_pack() checks if
`m->packs[pack_int_id]` is NULL in order to determine if a pack has been
opened and installed in the repository before. But a caller can
construct two copies of the same MIDX by calling get_multi_pack_index()
and load_multi_pack_index() since the former manipulates the
object store directly but the latter is a lower-level routine which
allocates a new MIDX for each call.

So if prepare_midx_pack() is called on multiple MIDXs with the same
pack_int_id, then that pack will be installed twice in the object
store's packed_git pointer.

This can lead to problems in, for e.g., the pack-bitmap code, which does
something like the following (in pack-bitmap.c:open_pack_bitmap()):

    struct bitmap_index *bitmap_git = ...;
    for (p = get_all_packs(r); p; p = p->next) {
      if (open_pack_bitmap_1(bitmap_git, p) == 0)
        ret = 0;
    }

which is a problem if two copies of the same pack exist in the
packed_git list because pack-bitmap.c:open_pack_bitmap_1() contains a
conditional like the following:

    if (bitmap_git->pack || bitmap_git->midx) {
      /* ignore extra bitmap file; we can only handle one */
      warning("ignoring extra bitmap file: %s", packfile->pack_name);
      close(fd);
      return -1;
    }

Avoid this scenario by not letting write_midx_internal() open a MIDX
that isn't also pointed at by the object store. So long as this is the
case, other routines should prefer to open MIDXs with
get_multi_pack_index() or reprepare_packed_git() instead of creating
instances on their own. Because get_multi_pack_index() returns
`r->object_store->multi_pack_index` if it is non-NULL, we'll only have
one instance of a MIDX open at one time, avoiding these problems.

To encourage this, drop the `struct multi_pack_index *` parameter from
`write_midx_internal()`, and rely instead on the `object_dir` to find
(or initialize) the correct MIDX instance.

Likewise, replace the call to `close_midx()` with
`close_object_store()`, since we're about to replace the MIDX with a new
one and should invalidate the object store's memory of any MIDX that
might have existed beforehand.

Note that this now forbids passing object directories that don't belong
to alternate repositories over `--object-dir`, since before we would
have happily opened a MIDX in any directory, but now restrict ourselves
to only those reachable by `r->objects->multi_pack_index` (and alternate
MIDXs that we can see by walking the `next` pointer).

As far as I can tell, supporting arbitrary directories with
`--object-dir` was a historical accident, since even the documentation
says `<alt>` when referring to the value passed to this option.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-09-01 13:56:43 -07:00

321 lines
9.0 KiB
C

#include "builtin.h"
#include "config.h"
#include "dir.h"
#include "lockfile.h"
#include "parse-options.h"
#include "repository.h"
#include "commit-graph.h"
#include "object-store.h"
#include "progress.h"
#include "tag.h"
static char const * const builtin_commit_graph_usage[] = {
N_("git commit-graph verify [--object-dir <objdir>] [--shallow] [--[no-]progress]"),
N_("git commit-graph write [--object-dir <objdir>] [--append] "
"[--split[=<strategy>]] [--reachable|--stdin-packs|--stdin-commits] "
"[--changed-paths] [--[no-]max-new-filters <n>] [--[no-]progress] "
"<split options>"),
NULL
};
static const char * const builtin_commit_graph_verify_usage[] = {
N_("git commit-graph verify [--object-dir <objdir>] [--shallow] [--[no-]progress]"),
NULL
};
static const char * const builtin_commit_graph_write_usage[] = {
N_("git commit-graph write [--object-dir <objdir>] [--append] "
"[--split[=<strategy>]] [--reachable|--stdin-packs|--stdin-commits] "
"[--changed-paths] [--[no-]max-new-filters <n>] [--[no-]progress] "
"<split options>"),
NULL
};
static struct opts_commit_graph {
const char *obj_dir;
int reachable;
int stdin_packs;
int stdin_commits;
int append;
int split;
int shallow;
int progress;
int enable_changed_paths;
} opts;
static int graph_verify(int argc, const char **argv)
{
struct commit_graph *graph = NULL;
struct object_directory *odb = NULL;
char *graph_name;
int open_ok;
int fd;
struct stat st;
int flags = 0;
static struct option builtin_commit_graph_verify_options[] = {
OPT_STRING(0, "object-dir", &opts.obj_dir,
N_("dir"),
N_("the object directory to store the graph")),
OPT_BOOL(0, "shallow", &opts.shallow,
N_("if the commit-graph is split, only verify the tip file")),
OPT_BOOL(0, "progress", &opts.progress, N_("force progress reporting")),
OPT_END(),
};
trace2_cmd_mode("verify");
opts.progress = isatty(2);
argc = parse_options(argc, argv, NULL,
builtin_commit_graph_verify_options,
builtin_commit_graph_verify_usage, 0);
if (!opts.obj_dir)
opts.obj_dir = get_object_directory();
if (opts.shallow)
flags |= COMMIT_GRAPH_VERIFY_SHALLOW;
if (opts.progress)
flags |= COMMIT_GRAPH_WRITE_PROGRESS;
odb = find_odb(the_repository, opts.obj_dir);
graph_name = get_commit_graph_filename(odb);
open_ok = open_commit_graph(graph_name, &fd, &st);
if (!open_ok && errno != ENOENT)
die_errno(_("Could not open commit-graph '%s'"), graph_name);
FREE_AND_NULL(graph_name);
if (open_ok)
graph = load_commit_graph_one_fd_st(the_repository, fd, &st, odb);
else
graph = read_commit_graph_one(the_repository, odb);
/* Return failure if open_ok predicted success */
if (!graph)
return !!open_ok;
UNLEAK(graph);
return verify_commit_graph(the_repository, graph, flags);
}
extern int read_replace_refs;
static struct commit_graph_opts write_opts;
static int write_option_parse_split(const struct option *opt, const char *arg,
int unset)
{
enum commit_graph_split_flags *flags = opt->value;
BUG_ON_OPT_NEG(unset);
opts.split = 1;
if (!arg)
return 0;
if (!strcmp(arg, "no-merge"))
*flags = COMMIT_GRAPH_SPLIT_MERGE_PROHIBITED;
else if (!strcmp(arg, "replace"))
*flags = COMMIT_GRAPH_SPLIT_REPLACE;
else
die(_("unrecognized --split argument, %s"), arg);
return 0;
}
static int read_one_commit(struct oidset *commits, struct progress *progress,
const char *hash)
{
struct object *result;
struct object_id oid;
const char *end;
if (parse_oid_hex(hash, &oid, &end))
return error(_("unexpected non-hex object ID: %s"), hash);
result = deref_tag(the_repository, parse_object(the_repository, &oid),
NULL, 0);
if (!result)
return error(_("invalid object: %s"), hash);
else if (object_as_type(result, OBJ_COMMIT, 1))
oidset_insert(commits, &result->oid);
display_progress(progress, oidset_size(commits));
return 0;
}
static int write_option_max_new_filters(const struct option *opt,
const char *arg,
int unset)
{
int *to = opt->value;
if (unset)
*to = -1;
else {
const char *s;
*to = strtol(arg, (char **)&s, 10);
if (*s)
return error(_("%s expects a numerical value"),
optname(opt, opt->flags));
}
return 0;
}
static int git_commit_graph_write_config(const char *var, const char *value,
void *cb)
{
if (!strcmp(var, "commitgraph.maxnewfilters"))
write_opts.max_new_filters = git_config_int(var, value);
/*
* No need to fall-back to 'git_default_config', since this was already
* called in 'cmd_commit_graph()'.
*/
return 0;
}
static int graph_write(int argc, const char **argv)
{
struct string_list pack_indexes = STRING_LIST_INIT_NODUP;
struct strbuf buf = STRBUF_INIT;
struct oidset commits = OIDSET_INIT;
struct object_directory *odb = NULL;
int result = 0;
enum commit_graph_write_flags flags = 0;
struct progress *progress = NULL;
static struct option builtin_commit_graph_write_options[] = {
OPT_STRING(0, "object-dir", &opts.obj_dir,
N_("dir"),
N_("the object directory to store the graph")),
OPT_BOOL(0, "reachable", &opts.reachable,
N_("start walk at all refs")),
OPT_BOOL(0, "stdin-packs", &opts.stdin_packs,
N_("scan pack-indexes listed by stdin for commits")),
OPT_BOOL(0, "stdin-commits", &opts.stdin_commits,
N_("start walk at commits listed by stdin")),
OPT_BOOL(0, "append", &opts.append,
N_("include all commits already in the commit-graph file")),
OPT_BOOL(0, "changed-paths", &opts.enable_changed_paths,
N_("enable computation for changed paths")),
OPT_BOOL(0, "progress", &opts.progress, N_("force progress reporting")),
OPT_CALLBACK_F(0, "split", &write_opts.split_flags, NULL,
N_("allow writing an incremental commit-graph file"),
PARSE_OPT_OPTARG | PARSE_OPT_NONEG,
write_option_parse_split),
OPT_INTEGER(0, "max-commits", &write_opts.max_commits,
N_("maximum number of commits in a non-base split commit-graph")),
OPT_INTEGER(0, "size-multiple", &write_opts.size_multiple,
N_("maximum ratio between two levels of a split commit-graph")),
OPT_EXPIRY_DATE(0, "expire-time", &write_opts.expire_time,
N_("only expire files older than a given date-time")),
OPT_CALLBACK_F(0, "max-new-filters", &write_opts.max_new_filters,
NULL, N_("maximum number of changed-path Bloom filters to compute"),
0, write_option_max_new_filters),
OPT_END(),
};
opts.progress = isatty(2);
opts.enable_changed_paths = -1;
write_opts.size_multiple = 2;
write_opts.max_commits = 0;
write_opts.expire_time = 0;
write_opts.max_new_filters = -1;
trace2_cmd_mode("write");
git_config(git_commit_graph_write_config, &opts);
argc = parse_options(argc, argv, NULL,
builtin_commit_graph_write_options,
builtin_commit_graph_write_usage, 0);
if (opts.reachable + opts.stdin_packs + opts.stdin_commits > 1)
die(_("use at most one of --reachable, --stdin-commits, or --stdin-packs"));
if (!opts.obj_dir)
opts.obj_dir = get_object_directory();
if (opts.append)
flags |= COMMIT_GRAPH_WRITE_APPEND;
if (opts.split)
flags |= COMMIT_GRAPH_WRITE_SPLIT;
if (opts.progress)
flags |= COMMIT_GRAPH_WRITE_PROGRESS;
if (!opts.enable_changed_paths)
flags |= COMMIT_GRAPH_NO_WRITE_BLOOM_FILTERS;
if (opts.enable_changed_paths == 1 ||
git_env_bool(GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS, 0))
flags |= COMMIT_GRAPH_WRITE_BLOOM_FILTERS;
read_replace_refs = 0;
odb = find_odb(the_repository, opts.obj_dir);
if (opts.reachable) {
if (write_commit_graph_reachable(odb, flags, &write_opts))
return 1;
return 0;
}
if (opts.stdin_packs) {
while (strbuf_getline(&buf, stdin) != EOF)
string_list_append(&pack_indexes,
strbuf_detach(&buf, NULL));
} else if (opts.stdin_commits) {
oidset_init(&commits, 0);
if (opts.progress)
progress = start_delayed_progress(
_("Collecting commits from input"), 0);
while (strbuf_getline(&buf, stdin) != EOF) {
if (read_one_commit(&commits, progress, buf.buf)) {
result = 1;
goto cleanup;
}
}
stop_progress(&progress);
}
if (write_commit_graph(odb,
opts.stdin_packs ? &pack_indexes : NULL,
opts.stdin_commits ? &commits : NULL,
flags,
&write_opts))
result = 1;
cleanup:
string_list_clear(&pack_indexes, 0);
strbuf_release(&buf);
return result;
}
int cmd_commit_graph(int argc, const char **argv, const char *prefix)
{
static struct option builtin_commit_graph_options[] = {
OPT_STRING(0, "object-dir", &opts.obj_dir,
N_("dir"),
N_("the object directory to store the graph")),
OPT_END(),
};
if (argc == 2 && !strcmp(argv[1], "-h"))
usage_with_options(builtin_commit_graph_usage,
builtin_commit_graph_options);
git_config(git_default_config, NULL);
argc = parse_options(argc, argv, prefix,
builtin_commit_graph_options,
builtin_commit_graph_usage,
PARSE_OPT_STOP_AT_NON_OPTION);
save_commit_buffer = 0;
if (argc > 0) {
if (!strcmp(argv[0], "verify"))
return graph_verify(argc, argv);
if (!strcmp(argv[0], "write"))
return graph_write(argc, argv);
}
usage_with_options(builtin_commit_graph_usage,
builtin_commit_graph_options);
}