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git/pack-write.c

585 lines
16 KiB

#include "cache.h"
#include "pack.h"
#include "csum-file.h"
#include "remote.h"
#include "chunk-format.h"
#include "pack-mtimes.h"
#include "oidmap.h"
#include "chunk-format.h"
#include "pack-objects.h"
void reset_pack_idx_option(struct pack_idx_option *opts)
{
memset(opts, 0, sizeof(*opts));
opts->version = 2;
opts->off32_limit = 0x7fffffff;
}
static int sha1_compare(const void *_a, const void *_b)
{
struct pack_idx_entry *a = *(struct pack_idx_entry **)_a;
struct pack_idx_entry *b = *(struct pack_idx_entry **)_b;
return oidcmp(&a->oid, &b->oid);
}
static int cmp_uint32(const void *a_, const void *b_)
{
uint32_t a = *((uint32_t *)a_);
uint32_t b = *((uint32_t *)b_);
return (a < b) ? -1 : (a != b);
}
static int need_large_offset(off_t offset, const struct pack_idx_option *opts)
{
uint32_t ofsval;
if ((offset >> 31) || (opts->off32_limit < offset))
return 1;
if (!opts->anomaly_nr)
return 0;
ofsval = offset;
return !!bsearch(&ofsval, opts->anomaly, opts->anomaly_nr,
sizeof(ofsval), cmp_uint32);
}
/*
* The *sha1 contains the pack content SHA1 hash.
* The objects array passed in will be sorted by SHA1 on exit.
*/
const char *write_idx_file(const char *index_name, struct pack_idx_entry **objects,
int nr_objects, const struct pack_idx_option *opts,
pack-objects: name pack files after trailer hash Our current scheme for naming packfiles is to calculate the sha1 hash of the sorted list of objects contained in the packfile. This gives us a unique name, so we are reasonably sure that two packs with the same name will contain the same objects. It does not, however, tell us that two such packs have the exact same bytes. This makes things awkward if we repack the same set of objects. Due to run-to-run variations, the bytes may not be identical (e.g., changed zlib or git versions, different source object reuse due to new packs in the repository, or even different deltas due to races during a multi-threaded delta search). In theory, this could be helpful to a program that cares that the packfile contains a certain set of objects, but does not care about the particular representation. In practice, no part of git makes use of that, and in many cases it is potentially harmful. For example, if a dumb http client fetches the .idx file, it must be sure to get the exact .pack that matches it. Similarly, a partial transfer of a .pack file cannot be safely resumed, as the actual bytes may have changed. This could also affect a local client which opened the .idx and .pack files, closes the .pack file (due to memory or file descriptor limits), and then re-opens a changed packfile. In all of these cases, git can detect the problem, as we have the sha1 of the bytes themselves in the pack trailer (which we verify on transfer), and the .idx file references the trailer from the matching packfile. But it would be simpler and more efficient to actually get the correct bytes, rather than noticing the problem and having to restart the operation. This patch simply uses the pack trailer sha1 as the pack name. It should be similarly unique, but covers the exact representation of the objects. Other parts of git should not care, as the pack name is returned by pack-objects and is essentially opaque. One test needs to be updated, because it actually corrupts a pack and expects that re-packing the corrupted bytes will use the same name. It won't anymore, but we can easily just use the name that pack-objects hands back. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
9 years ago
const unsigned char *sha1)
{
struct hashfile *f;
struct pack_idx_entry **sorted_by_sha, **list, **last;
off_t last_obj_offset = 0;
int i, fd;
uint32_t index_version;
if (nr_objects) {
sorted_by_sha = objects;
list = sorted_by_sha;
last = sorted_by_sha + nr_objects;
for (i = 0; i < nr_objects; ++i) {
if (objects[i]->offset > last_obj_offset)
last_obj_offset = objects[i]->offset;
}
QSORT(sorted_by_sha, nr_objects, sha1_compare);
}
else
sorted_by_sha = list = last = NULL;
if (opts->flags & WRITE_IDX_VERIFY) {
assert(index_name);
f = hashfd_check(index_name);
} else {
if (!index_name) {
struct strbuf tmp_file = STRBUF_INIT;
fd = odb_mkstemp(&tmp_file, "pack/tmp_idx_XXXXXX");
index_name = strbuf_detach(&tmp_file, NULL);
} else {
unlink(index_name);
fd = xopen(index_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
}
f = hashfd(fd, index_name);
}
/* if last object's offset is >= 2^31 we should use index V2 */
index_version = need_large_offset(last_obj_offset, opts) ? 2 : opts->version;
/* index versions 2 and above need a header */
if (index_version >= 2) {
struct pack_idx_header hdr;
hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
hdr.idx_version = htonl(index_version);
hashwrite(f, &hdr, sizeof(hdr));
}
/*
* Write the first-level table (the list is sorted,
* but we use a 256-entry lookup to be able to avoid
* having to do eight extra binary search iterations).
*/
for (i = 0; i < 256; i++) {
struct pack_idx_entry **next = list;
while (next < last) {
struct pack_idx_entry *obj = *next;
if (obj->oid.hash[0] != i)
break;
next++;
}
hashwrite_be32(f, next - sorted_by_sha);
list = next;
}
/*
* Write the actual SHA1 entries..
*/
list = sorted_by_sha;
for (i = 0; i < nr_objects; i++) {
struct pack_idx_entry *obj = *list++;
if (index_version < 2)
hashwrite_be32(f, obj->offset);
hashwrite(f, obj->oid.hash, the_hash_algo->rawsz);
if ((opts->flags & WRITE_IDX_STRICT) &&
(i && oideq(&list[-2]->oid, &obj->oid)))
die("The same object %s appears twice in the pack",
oid_to_hex(&obj->oid));
}
if (index_version >= 2) {
unsigned int nr_large_offset = 0;
/* write the crc32 table */
list = sorted_by_sha;
for (i = 0; i < nr_objects; i++) {
struct pack_idx_entry *obj = *list++;
hashwrite_be32(f, obj->crc32);
}
/* write the 32-bit offset table */
list = sorted_by_sha;
for (i = 0; i < nr_objects; i++) {
struct pack_idx_entry *obj = *list++;
uint32_t offset;
offset = (need_large_offset(obj->offset, opts)
? (0x80000000 | nr_large_offset++)
: obj->offset);
hashwrite_be32(f, offset);
}
/* write the large offset table */
list = sorted_by_sha;
while (nr_large_offset) {
struct pack_idx_entry *obj = *list++;
uint64_t offset = obj->offset;
if (!need_large_offset(offset, opts))
continue;
hashwrite_be64(f, offset);
nr_large_offset--;
}
}
hashwrite(f, sha1, the_hash_algo->rawsz);
finalize_hashfile(f, NULL, FSYNC_COMPONENT_PACK_METADATA,
CSUM_HASH_IN_STREAM | CSUM_CLOSE |
((opts->flags & WRITE_IDX_VERIFY) ? 0 : CSUM_FSYNC));
return index_name;
}
static int pack_order_cmp(const void *va, const void *vb, void *ctx)
{
struct pack_idx_entry **objects = ctx;
off_t oa = objects[*(uint32_t*)va]->offset;
off_t ob = objects[*(uint32_t*)vb]->offset;
if (oa < ob)
return -1;
if (oa > ob)
return 1;
return 0;
}
static void write_rev_header(struct hashfile *f)
{
hashwrite_be32(f, RIDX_SIGNATURE);
hashwrite_be32(f, RIDX_VERSION);
hashwrite_be32(f, oid_version(the_hash_algo));
}
static void write_rev_index_positions(struct hashfile *f,
uint32_t *pack_order,
uint32_t nr_objects)
{
uint32_t i;
for (i = 0; i < nr_objects; i++)
hashwrite_be32(f, pack_order[i]);
}
static void write_rev_trailer(struct hashfile *f, const unsigned char *hash)
{
hashwrite(f, hash, the_hash_algo->rawsz);
}
const char *write_rev_file(const char *rev_name,
struct pack_idx_entry **objects,
uint32_t nr_objects,
const unsigned char *hash,
unsigned flags)
{
uint32_t *pack_order;
uint32_t i;
const char *ret;
if (!(flags & WRITE_REV) && !(flags & WRITE_REV_VERIFY))
return NULL;
ALLOC_ARRAY(pack_order, nr_objects);
for (i = 0; i < nr_objects; i++)
pack_order[i] = i;
QSORT_S(pack_order, nr_objects, pack_order_cmp, objects);
ret = write_rev_file_order(rev_name, pack_order, nr_objects, hash,
flags);
free(pack_order);
return ret;
}
const char *write_rev_file_order(const char *rev_name,
uint32_t *pack_order,
uint32_t nr_objects,
const unsigned char *hash,
unsigned flags)
{
struct hashfile *f;
int fd;
if ((flags & WRITE_REV) && (flags & WRITE_REV_VERIFY))
die(_("cannot both write and verify reverse index"));
if (flags & WRITE_REV) {
if (!rev_name) {
struct strbuf tmp_file = STRBUF_INIT;
fd = odb_mkstemp(&tmp_file, "pack/tmp_rev_XXXXXX");
rev_name = strbuf_detach(&tmp_file, NULL);
} else {
unlink(rev_name);
fd = xopen(rev_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
}
f = hashfd(fd, rev_name);
} else if (flags & WRITE_REV_VERIFY) {
struct stat statbuf;
if (stat(rev_name, &statbuf)) {
if (errno == ENOENT) {
/* .rev files are optional */
return NULL;
} else
die_errno(_("could not stat: %s"), rev_name);
}
f = hashfd_check(rev_name);
} else
return NULL;
write_rev_header(f);
write_rev_index_positions(f, pack_order, nr_objects);
write_rev_trailer(f, hash);
if (rev_name && adjust_shared_perm(rev_name) < 0)
die(_("failed to make %s readable"), rev_name);
finalize_hashfile(f, NULL, FSYNC_COMPONENT_PACK_METADATA,
CSUM_HASH_IN_STREAM | CSUM_CLOSE |
((flags & WRITE_IDX_VERIFY) ? 0 : CSUM_FSYNC));
return rev_name;
}
static void write_mtimes_header(struct hashfile *f)
{
hashwrite_be32(f, MTIMES_SIGNATURE);
hashwrite_be32(f, MTIMES_VERSION);
hashwrite_be32(f, oid_version(the_hash_algo));
}
/*
* Writes the object mtimes of "objects" for use in a .mtimes file.
* Note that objects must be in lexicographic (index) order, which is
* the expected ordering of these values in the .mtimes file.
*/
static void write_mtimes_objects(struct hashfile *f,
struct packing_data *to_pack,
struct pack_idx_entry **objects,
uint32_t nr_objects)
{
uint32_t i;
for (i = 0; i < nr_objects; i++) {
struct object_entry *e = (struct object_entry*)objects[i];
hashwrite_be32(f, oe_cruft_mtime(to_pack, e));
}
}
static void write_mtimes_trailer(struct hashfile *f, const unsigned char *hash)
{
hashwrite(f, hash, the_hash_algo->rawsz);
}
static const char *write_mtimes_file(struct packing_data *to_pack,
struct pack_idx_entry **objects,
uint32_t nr_objects,
const unsigned char *hash)
{
struct strbuf tmp_file = STRBUF_INIT;
const char *mtimes_name;
struct hashfile *f;
int fd;
if (!to_pack)
BUG("cannot call write_mtimes_file with NULL packing_data");
fd = odb_mkstemp(&tmp_file, "pack/tmp_mtimes_XXXXXX");
mtimes_name = strbuf_detach(&tmp_file, NULL);
f = hashfd(fd, mtimes_name);
write_mtimes_header(f);
write_mtimes_objects(f, to_pack, objects, nr_objects);
write_mtimes_trailer(f, hash);
if (adjust_shared_perm(mtimes_name) < 0)
die(_("failed to make %s readable"), mtimes_name);
finalize_hashfile(f, NULL, FSYNC_COMPONENT_PACK_METADATA,
CSUM_HASH_IN_STREAM | CSUM_CLOSE | CSUM_FSYNC);
return mtimes_name;
}
off_t write_pack_header(struct hashfile *f, uint32_t nr_entries)
{
struct pack_header hdr;
hdr.hdr_signature = htonl(PACK_SIGNATURE);
hdr.hdr_version = htonl(PACK_VERSION);
hdr.hdr_entries = htonl(nr_entries);
hashwrite(f, &hdr, sizeof(hdr));
return sizeof(hdr);
}
/*
* Update pack header with object_count and compute new SHA1 for pack data
* associated to pack_fd, and write that SHA1 at the end. That new SHA1
* is also returned in new_pack_sha1.
*
* If partial_pack_sha1 is non null, then the SHA1 of the existing pack
* (without the header update) is computed and validated against the
* one provided in partial_pack_sha1. The validation is performed at
* partial_pack_offset bytes in the pack file. The SHA1 of the remaining
* data (i.e. from partial_pack_offset to the end) is then computed and
* returned in partial_pack_sha1.
*
* Note that new_pack_sha1 is updated last, so both new_pack_sha1 and
* partial_pack_sha1 can refer to the same buffer if the caller is not
* interested in the resulting SHA1 of pack data above partial_pack_offset.
*/
void fixup_pack_header_footer(int pack_fd,
unsigned char *new_pack_hash,
const char *pack_name,
uint32_t object_count,
unsigned char *partial_pack_hash,
off_t partial_pack_offset)
{
int aligned_sz, buf_sz = 8 * 1024;
git_hash_ctx old_hash_ctx, new_hash_ctx;
struct pack_header hdr;
char *buf;
ssize_t read_result;
the_hash_algo->init_fn(&old_hash_ctx);
the_hash_algo->init_fn(&new_hash_ctx);
if (lseek(pack_fd, 0, SEEK_SET) != 0)
die_errno("Failed seeking to start of '%s'", pack_name);
read_result = read_in_full(pack_fd, &hdr, sizeof(hdr));
if (read_result < 0)
die_errno("Unable to reread header of '%s'", pack_name);
else if (read_result != sizeof(hdr))
die_errno("Unexpected short read for header of '%s'",
pack_name);
if (lseek(pack_fd, 0, SEEK_SET) != 0)
die_errno("Failed seeking to start of '%s'", pack_name);
the_hash_algo->update_fn(&old_hash_ctx, &hdr, sizeof(hdr));
hdr.hdr_entries = htonl(object_count);
the_hash_algo->update_fn(&new_hash_ctx, &hdr, sizeof(hdr));
write_or_die(pack_fd, &hdr, sizeof(hdr));
partial_pack_offset -= sizeof(hdr);
buf = xmalloc(buf_sz);
aligned_sz = buf_sz - sizeof(hdr);
for (;;) {
ssize_t m, n;
m = (partial_pack_hash && partial_pack_offset < aligned_sz) ?
partial_pack_offset : aligned_sz;
n = xread(pack_fd, buf, m);
if (!n)
break;
if (n < 0)
die_errno("Failed to checksum '%s'", pack_name);
the_hash_algo->update_fn(&new_hash_ctx, buf, n);
aligned_sz -= n;
if (!aligned_sz)
aligned_sz = buf_sz;
if (!partial_pack_hash)
continue;
the_hash_algo->update_fn(&old_hash_ctx, buf, n);
partial_pack_offset -= n;
if (partial_pack_offset == 0) {
unsigned char hash[GIT_MAX_RAWSZ];
the_hash_algo->final_fn(hash, &old_hash_ctx);
if (!hasheq(hash, partial_pack_hash))
die("Unexpected checksum for %s "
"(disk corruption?)", pack_name);
/*
* Now let's compute the SHA1 of the remainder of the
* pack, which also means making partial_pack_offset
* big enough not to matter anymore.
*/
the_hash_algo->init_fn(&old_hash_ctx);
partial_pack_offset = ~partial_pack_offset;
partial_pack_offset -= MSB(partial_pack_offset, 1);
}
}
free(buf);
if (partial_pack_hash)
the_hash_algo->final_fn(partial_pack_hash, &old_hash_ctx);
the_hash_algo->final_fn(new_pack_hash, &new_hash_ctx);
write_or_die(pack_fd, new_pack_hash, the_hash_algo->rawsz);
fsync_component_or_die(FSYNC_COMPONENT_PACK, pack_fd, pack_name);
}
char *index_pack_lockfile(int ip_out, int *is_well_formed)
{
char packname[GIT_MAX_HEXSZ + 6];
const int len = the_hash_algo->hexsz + 6;
/*
* The first thing we expect from index-pack's output
* is "pack\t%40s\n" or "keep\t%40s\n" (46 bytes) where
* %40s is the newly created pack SHA1 name. In the "keep"
* case, we need it to remove the corresponding .keep file
* later on. If we don't get that then tough luck with it.
*/
if (read_in_full(ip_out, packname, len) == len && packname[len-1] == '\n') {
const char *name;
if (is_well_formed)
*is_well_formed = 1;
packname[len-1] = 0;
if (skip_prefix(packname, "keep\t", &name))
return xstrfmt("%s/pack/pack-%s.keep",
get_object_directory(), name);
return NULL;
}
if (is_well_formed)
*is_well_formed = 0;
return NULL;
}
/*
* The per-object header is a pretty dense thing, which is
* - first byte: low four bits are "size", then three bits of "type",
* and the high bit is "size continues".
* - each byte afterwards: low seven bits are size continuation,
* with the high bit being "size continues"
*/
int encode_in_pack_object_header(unsigned char *hdr, int hdr_len,
enum object_type type, uintmax_t size)
{
int n = 1;
unsigned char c;
if (type < OBJ_COMMIT || type > OBJ_REF_DELTA)
die("bad type %d", type);
c = (type << 4) | (size & 15);
size >>= 4;
while (size) {
if (n == hdr_len)
die("object size is too enormous to format");
*hdr++ = c | 0x80;
c = size & 0x7f;
size >>= 7;
n++;
}
*hdr = c;
return n;
}
struct hashfile *create_tmp_packfile(char **pack_tmp_name)
{
struct strbuf tmpname = STRBUF_INIT;
int fd;
fd = odb_mkstemp(&tmpname, "pack/tmp_pack_XXXXXX");
*pack_tmp_name = strbuf_detach(&tmpname, NULL);
return hashfd(fd, *pack_tmp_name);
}
static void rename_tmp_packfile(struct strbuf *name_prefix, const char *source,
const char *ext)
{
size_t name_prefix_len = name_prefix->len;
strbuf_addstr(name_prefix, ext);
if (rename(source, name_prefix->buf))
die_errno("unable to rename temporary file to '%s'",
name_prefix->buf);
strbuf_setlen(name_prefix, name_prefix_len);
}
void rename_tmp_packfile_idx(struct strbuf *name_buffer,
char **idx_tmp_name)
{
rename_tmp_packfile(name_buffer, *idx_tmp_name, "idx");
}
void stage_tmp_packfiles(struct strbuf *name_buffer,
const char *pack_tmp_name,
struct pack_idx_entry **written_list,
uint32_t nr_written,
struct packing_data *to_pack,
struct pack_idx_option *pack_idx_opts,
unsigned char hash[],
char **idx_tmp_name)
{
const char *rev_tmp_name = NULL;
const char *mtimes_tmp_name = NULL;
if (adjust_shared_perm(pack_tmp_name))
die_errno("unable to make temporary pack file readable");
*idx_tmp_name = (char *)write_idx_file(NULL, written_list, nr_written,
pack_idx_opts, hash);
if (adjust_shared_perm(*idx_tmp_name))
die_errno("unable to make temporary index file readable");
rev_tmp_name = write_rev_file(NULL, written_list, nr_written, hash,
pack_idx_opts->flags);
if (pack_idx_opts->flags & WRITE_MTIMES) {
mtimes_tmp_name = write_mtimes_file(to_pack, written_list,
nr_written,
hash);
}