git/bulk-checkin.c
Jeff King 7140414d8b bulk-checkin: zero-initialize hashfile_checkpoint
We declare a "struct hashfile_checkpoint" but only sometimes actually
call hashfile_checkpoint() on it. That makes it not immediately obvious
that it's valid when we later access its members.

In fact, the code is fine: we fill it in unconditionally in the while(1)
loop as long as "idx" is non-NULL. And then if "idx" is NULL, we exit
early from the function (because we're just computing the hash, not
actually writing), before we look at the struct.

However, this does seem to confuse gcc 9.2.1's -Wmaybe-uninitialized
when compiled with "-flto -O2" (probably because with LTO it can now
realize that our call to hashfile_truncate() does not set the members
either). Let's zero-initialize the struct to tell the compiler, as well
as any readers of the code, that all is well.

Reported-by: Stephan Beyer <s-beyer@gmx.net>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-09-06 11:03:39 -07:00

282 lines
7.3 KiB
C

/*
* Copyright (c) 2011, Google Inc.
*/
#include "cache.h"
#include "bulk-checkin.h"
#include "repository.h"
#include "csum-file.h"
#include "pack.h"
#include "strbuf.h"
#include "packfile.h"
#include "object-store.h"
static struct bulk_checkin_state {
unsigned plugged:1;
char *pack_tmp_name;
struct hashfile *f;
off_t offset;
struct pack_idx_option pack_idx_opts;
struct pack_idx_entry **written;
uint32_t alloc_written;
uint32_t nr_written;
} state;
static void finish_bulk_checkin(struct bulk_checkin_state *state)
{
struct object_id oid;
struct strbuf packname = STRBUF_INIT;
int i;
if (!state->f)
return;
if (state->nr_written == 0) {
close(state->f->fd);
unlink(state->pack_tmp_name);
goto clear_exit;
} else if (state->nr_written == 1) {
finalize_hashfile(state->f, oid.hash, CSUM_HASH_IN_STREAM | CSUM_FSYNC | CSUM_CLOSE);
} else {
int fd = finalize_hashfile(state->f, oid.hash, 0);
fixup_pack_header_footer(fd, oid.hash, state->pack_tmp_name,
state->nr_written, oid.hash,
state->offset);
close(fd);
}
strbuf_addf(&packname, "%s/pack/pack-", get_object_directory());
finish_tmp_packfile(&packname, state->pack_tmp_name,
state->written, state->nr_written,
&state->pack_idx_opts, oid.hash);
for (i = 0; i < state->nr_written; i++)
free(state->written[i]);
clear_exit:
free(state->written);
memset(state, 0, sizeof(*state));
strbuf_release(&packname);
/* Make objects we just wrote available to ourselves */
reprepare_packed_git(the_repository);
}
static int already_written(struct bulk_checkin_state *state, struct object_id *oid)
{
int i;
/* The object may already exist in the repository */
if (has_object_file(oid))
return 1;
/* Might want to keep the list sorted */
for (i = 0; i < state->nr_written; i++)
if (oideq(&state->written[i]->oid, oid))
return 1;
/* This is a new object we need to keep */
return 0;
}
/*
* Read the contents from fd for size bytes, streaming it to the
* packfile in state while updating the hash in ctx. Signal a failure
* by returning a negative value when the resulting pack would exceed
* the pack size limit and this is not the first object in the pack,
* so that the caller can discard what we wrote from the current pack
* by truncating it and opening a new one. The caller will then call
* us again after rewinding the input fd.
*
* The already_hashed_to pointer is kept untouched by the caller to
* make sure we do not hash the same byte when we are called
* again. This way, the caller does not have to checkpoint its hash
* status before calling us just in case we ask it to call us again
* with a new pack.
*/
static int stream_to_pack(struct bulk_checkin_state *state,
git_hash_ctx *ctx, off_t *already_hashed_to,
int fd, size_t size, enum object_type type,
const char *path, unsigned flags)
{
git_zstream s;
unsigned char obuf[16384];
unsigned hdrlen;
int status = Z_OK;
int write_object = (flags & HASH_WRITE_OBJECT);
off_t offset = 0;
git_deflate_init(&s, pack_compression_level);
hdrlen = encode_in_pack_object_header(obuf, sizeof(obuf), type, size);
s.next_out = obuf + hdrlen;
s.avail_out = sizeof(obuf) - hdrlen;
while (status != Z_STREAM_END) {
unsigned char ibuf[16384];
if (size && !s.avail_in) {
ssize_t rsize = size < sizeof(ibuf) ? size : sizeof(ibuf);
ssize_t read_result = read_in_full(fd, ibuf, rsize);
if (read_result < 0)
die_errno("failed to read from '%s'", path);
if (read_result != rsize)
die("failed to read %d bytes from '%s'",
(int)rsize, path);
offset += rsize;
if (*already_hashed_to < offset) {
size_t hsize = offset - *already_hashed_to;
if (rsize < hsize)
hsize = rsize;
if (hsize)
the_hash_algo->update_fn(ctx, ibuf, hsize);
*already_hashed_to = offset;
}
s.next_in = ibuf;
s.avail_in = rsize;
size -= rsize;
}
status = git_deflate(&s, size ? 0 : Z_FINISH);
if (!s.avail_out || status == Z_STREAM_END) {
if (write_object) {
size_t written = s.next_out - obuf;
/* would we bust the size limit? */
if (state->nr_written &&
pack_size_limit_cfg &&
pack_size_limit_cfg < state->offset + written) {
git_deflate_abort(&s);
return -1;
}
hashwrite(state->f, obuf, written);
state->offset += written;
}
s.next_out = obuf;
s.avail_out = sizeof(obuf);
}
switch (status) {
case Z_OK:
case Z_BUF_ERROR:
case Z_STREAM_END:
continue;
default:
die("unexpected deflate failure: %d", status);
}
}
git_deflate_end(&s);
return 0;
}
/* Lazily create backing packfile for the state */
static void prepare_to_stream(struct bulk_checkin_state *state,
unsigned flags)
{
if (!(flags & HASH_WRITE_OBJECT) || state->f)
return;
state->f = create_tmp_packfile(&state->pack_tmp_name);
reset_pack_idx_option(&state->pack_idx_opts);
/* Pretend we are going to write only one object */
state->offset = write_pack_header(state->f, 1);
if (!state->offset)
die_errno("unable to write pack header");
}
static int deflate_to_pack(struct bulk_checkin_state *state,
struct object_id *result_oid,
int fd, size_t size,
enum object_type type, const char *path,
unsigned flags)
{
off_t seekback, already_hashed_to;
git_hash_ctx ctx;
unsigned char obuf[16384];
unsigned header_len;
struct hashfile_checkpoint checkpoint = {0};
struct pack_idx_entry *idx = NULL;
seekback = lseek(fd, 0, SEEK_CUR);
if (seekback == (off_t) -1)
return error("cannot find the current offset");
header_len = xsnprintf((char *)obuf, sizeof(obuf), "%s %" PRIuMAX,
type_name(type), (uintmax_t)size) + 1;
the_hash_algo->init_fn(&ctx);
the_hash_algo->update_fn(&ctx, obuf, header_len);
/* Note: idx is non-NULL when we are writing */
if ((flags & HASH_WRITE_OBJECT) != 0)
idx = xcalloc(1, sizeof(*idx));
already_hashed_to = 0;
while (1) {
prepare_to_stream(state, flags);
if (idx) {
hashfile_checkpoint(state->f, &checkpoint);
idx->offset = state->offset;
crc32_begin(state->f);
}
if (!stream_to_pack(state, &ctx, &already_hashed_to,
fd, size, type, path, flags))
break;
/*
* Writing this object to the current pack will make
* it too big; we need to truncate it, start a new
* pack, and write into it.
*/
if (!idx)
BUG("should not happen");
hashfile_truncate(state->f, &checkpoint);
state->offset = checkpoint.offset;
finish_bulk_checkin(state);
if (lseek(fd, seekback, SEEK_SET) == (off_t) -1)
return error("cannot seek back");
}
the_hash_algo->final_fn(result_oid->hash, &ctx);
if (!idx)
return 0;
idx->crc32 = crc32_end(state->f);
if (already_written(state, result_oid)) {
hashfile_truncate(state->f, &checkpoint);
state->offset = checkpoint.offset;
free(idx);
} else {
oidcpy(&idx->oid, result_oid);
ALLOC_GROW(state->written,
state->nr_written + 1,
state->alloc_written);
state->written[state->nr_written++] = idx;
}
return 0;
}
int index_bulk_checkin(struct object_id *oid,
int fd, size_t size, enum object_type type,
const char *path, unsigned flags)
{
int status = deflate_to_pack(&state, oid, fd, size, type,
path, flags);
if (!state.plugged)
finish_bulk_checkin(&state);
return status;
}
void plug_bulk_checkin(void)
{
state.plugged = 1;
}
void unplug_bulk_checkin(void)
{
state.plugged = 0;
if (state.f)
finish_bulk_checkin(&state);
}