[PATCH 09/32] object-file: Update the loose object map when writing loose objects
- From
Eric W. Biederman <ebiederm@xmission.com>
- Date
- Sep 8, 2023, 23:10 UTC
- Message-ID
- <20230908231049.2035003-9-ebiederm@xmission.com>
- In-Reply-To
- <87sf7ol0z3.fsf@email.froward.int.ebiederm.org>
To implement SHA1 compatibility on SHA256 repositories the loose object map needs to be updated whenver a loose object is written. Updating the loose object map this way allows git to support the old hash algorithm in constant time.
The functions write_loose_object, and stream_loose_object are the only two functions that write to the loose object store.
Update stream_loose_object to compute the compatibiilty hash, update the loose object, and then call repo_add_loose_object_map to update the loose object map.
Update write_object_file_flags to convert the object into it's compatibility encoding, hash the compatibility encoding, write the object, and then update the loose object map.
Update force_object_loose to lookup the hash of the compatibility encoding, write the loose object, and then update the loose object map.
Update write_object_file_litterally to refuse to write any objects when a compatibility encoding is enabled. The problem is that write_object_file_literally is frequently used to write ill-formed objects. Especially when the type of those objects is changed there is by definition no possibile way to convert them, as no converstion has been defined.
Since a compatibilty encoding can not be found and a compatibility mapping can not be written the cleanest behavior is to simply disallow write_object_file_literraly from writing files.
Except that the loose objects are updated before the loose object map I have not done any analysis to see how robust this scheme is in the event of failure.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> --- object-file.c | 94 +++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 76 insertions(+), 18 deletions(-)
diff --git a/object-file.c b/object-file.c index 7f24f19b8a68..6a14b8875343 100644 --- a/object-file.c +++ b/object-file.c @@ -44,6 +44,7 @@ #include "setup.h" #include "submodule.h" #include "fsck.h" +#include "loose.h" /* The maximum size for an object header. */ #define MAX_HEADER_LEN 32 @@ -2035,9 +2036,12 @@ static int start_loose_object_common(struct strbuf *tmp_file, const char *filename, unsigned flags, git_zstream *stream, unsigned char *buf, size_t buflen, - git_hash_ctx *c, + git_hash_ctx *c, git_hash_ctx *compat_c, char *hdr, int hdrlen) { + struct repository *repo = the_repository; + const struct git_hash_algo *algo = repo->hash_algo; + const struct git_hash_algo *compat = repo->compat_hash_algo; int fd; fd = create_tmpfile(tmp_file, filename); @@ -2057,14 +2061,18 @@ static int start_loose_object_common(struct strbuf *tmp_file, git_deflate_init(stream, zlib_compression_level); stream->next_out = buf; stream->avail_out = buflen; - the_hash_algo->init_fn(c); + algo->init_fn(c); + if (compat && compat_c) + compat->init_fn(compat_c); /* Start to feed header to zlib stream */ stream->next_in = (unsigned char *)hdr; stream->avail_in = hdrlen; while (git_deflate(stream, 0) == Z_OK) ; /* nothing */ - the_hash_algo->update_fn(c, hdr, hdrlen); + algo->update_fn(c, hdr, hdrlen); + if (compat && compat_c) + compat->update_fn(compat_c, hdr, hdrlen); return fd; } @@ -2073,16 +2081,21 @@ static int start_loose_object_common(struct strbuf *tmp_file, * Common steps for the inner git_deflate() loop for writing loose * objects. Returns what git_deflate() returns. */ -static int write_loose_object_common(git_hash_ctx *c, +static int write_loose_object_common(git_hash_ctx *c, git_hash_ctx *compat_c, git_zstream *stream, const int flush, unsigned char *in0, const int fd, unsigned char *compressed, const size_t compressed_len) { + struct repository *repo = the_repository; + const struct git_hash_algo *algo = repo->hash_algo; + const struct git_hash_algo *compat = repo->compat_hash_algo; int ret; ret = git_deflate(stream, flush ? Z_FINISH : 0); - the_hash_algo->update_fn(c, in0, stream->next_in - in0); + algo->update_fn(c, in0, stream->next_in - in0); + if (compat && compat_c) + compat->update_fn(compat_c, in0, stream->next_in - in0); if (write_in_full(fd, compressed, stream->next_out - compressed) < 0) die_errno(_("unable to write loose object file")); stream->next_out = compressed; @@ -2097,15 +2110,21 @@ static int write_loose_object_common(git_hash_ctx *c, * - End the compression of zlib stream. * - Get the calculated oid to "oid". */ -static int end_loose_object_common(git_hash_ctx *c, git_zstream *stream, - struct object_id *oid) +static int end_loose_object_common(git_hash_ctx *c, git_hash_ctx *compat_c, + git_zstream *stream, struct object_id *oid, + struct object_id *compat_oid) { + struct repository *repo = the_repository; + const struct git_hash_algo *algo = repo->hash_algo; + const struct git_hash_algo *compat = repo->compat_hash_algo; int ret; ret = git_deflate_end_gently(stream); if (ret != Z_OK) return ret; - the_hash_algo->final_oid_fn(oid, c); + algo->final_oid_fn(oid, c); + if (compat && compat_c) + compat->final_oid_fn(compat_oid, compat_c); return Z_OK; } @@ -2129,7 +2148,7 @@ static int write_loose_object(const struct object_id *oid, char *hdr, fd = start_loose_object_common(&tmp_file, filename.buf, flags, &stream, compressed, sizeof(compressed), - &c, hdr, hdrlen); + &c, NULL, hdr, hdrlen); if (fd < 0) return -1; @@ -2139,14 +2158,14 @@ static int write_loose_object(const struct object_id *oid, char *hdr, do { unsigned char *in0 = stream.next_in; - ret = write_loose_object_common(&c, &stream, 1, in0, fd, + ret = write_loose_object_common(&c, NULL, &stream, 1, in0, fd, compressed, sizeof(compressed)); } while (ret == Z_OK); if (ret != Z_STREAM_END) die(_("unable to deflate new object %s (%d)"), oid_to_hex(oid), ret); - ret = end_loose_object_common(&c, &stream, ¶no_oid); + ret = end_loose_object_common(&c, NULL, &stream, ¶no_oid, NULL); if (ret != Z_OK) die(_("deflateEnd on object %s failed (%d)"), oid_to_hex(oid), ret); @@ -2191,10 +2210,12 @@ static int freshen_packed_object(const struct object_id *oid) int stream_loose_object(struct input_stream *in_stream, size_t len, struct object_id *oid) { + const struct git_hash_algo *compat = the_repository->compat_hash_algo; + struct object_id compat_oid; int fd, ret, err = 0, flush = 0; unsigned char compressed[4096]; git_zstream stream; - git_hash_ctx c; + git_hash_ctx c, compat_c; struct strbuf tmp_file = STRBUF_INIT; struct strbuf filename = STRBUF_INIT; int dirlen; @@ -2218,7 +2239,7 @@ int stream_loose_object(struct input_stream *in_stream, size_t len, */ fd = start_loose_object_common(&tmp_file, filename.buf, 0, &stream, compressed, sizeof(compressed), - &c, hdr, hdrlen); + &c, &compat_c, hdr, hdrlen); if (fd < 0) { err = -1; goto cleanup; @@ -2236,7 +2257,7 @@ int stream_loose_object(struct input_stream *in_stream, size_t len, if (in_stream->is_finished) flush = 1; } - ret = write_loose_object_common(&c, &stream, flush, in0, fd, + ret = write_loose_object_common(&c, &compat_c, &stream, flush, in0, fd, compressed, sizeof(compressed)); /* * Unlike write_loose_object(), we do not have the entire @@ -2259,7 +2280,7 @@ int stream_loose_object(struct input_stream *in_stream, size_t len, */ if (ret != Z_STREAM_END) die(_("unable to stream deflate new object (%d)"), ret); - ret = end_loose_object_common(&c, &stream, oid); + ret = end_loose_object_common(&c, &compat_c, &stream, oid, &compat_oid); if (ret != Z_OK) die(_("deflateEnd on stream object failed (%d)"), ret); close_loose_object(fd, tmp_file.buf); @@ -2286,6 +2307,8 @@ int stream_loose_object(struct input_stream *in_stream, size_t len, } err = finalize_object_file(tmp_file.buf, filename.buf); + if (!err && compat) + err = repo_add_loose_object_map(the_repository, oid, &compat_oid); cleanup: strbuf_release(&tmp_file); strbuf_release(&filename); @@ -2296,17 +2319,38 @@ int write_object_file_flags(const void *buf, unsigned long len, enum object_type type, struct object_id *oid, unsigned flags) { + struct repository *repo = the_repository; + const struct git_hash_algo *algo = repo->hash_algo; + const struct git_hash_algo *compat = repo->compat_hash_algo; + struct object_id compat_oid; char hdr[MAX_HEADER_LEN]; int hdrlen = sizeof(hdr); + /* Generate compat_oid */ + if (compat) { + if (type == OBJ_BLOB) + hash_object_file(compat, buf, len, type, &compat_oid); + else { + struct strbuf converted = STRBUF_INIT; + convert_object_file(&converted, algo, compat, + buf, len, type, 0); + hash_object_file(compat, converted.buf, converted.len, + type, &compat_oid); + strbuf_release(&converted); + } + } + /* Normally if we have it in the pack then we do not bother writing * it out into .git/objects/??/?{38} file. */ - write_object_file_prepare(the_hash_algo, buf, len, type, oid, hdr, - &hdrlen); + write_object_file_prepare(algo, buf, len, type, oid, hdr, &hdrlen); if (freshen_packed_object(oid) || freshen_loose_object(oid)) return 0; - return write_loose_object(oid, hdr, hdrlen, buf, len, 0, flags); + if (write_loose_object(oid, hdr, hdrlen, buf, len, 0, flags)) + return -1; + if (compat) + return repo_add_loose_object_map(repo, oid, &compat_oid); + return 0; } int write_object_file_literally(const void *buf, unsigned long len, @@ -2324,6 +2368,10 @@ int write_object_file_literally(const void *buf, unsigned long len, if (!(flags & HASH_WRITE_OBJECT)) goto cleanup; + else if (the_repository->compat_hash_algo) { + status = -1; + goto cleanup; + } if (freshen_packed_object(oid) || freshen_loose_object(oid)) goto cleanup; status = write_loose_object(oid, header, hdrlen, buf, len, 0, 0); @@ -2335,9 +2383,12 @@ int write_object_file_literally(const void *buf, unsigned long len, int force_object_loose(const struct object_id *oid, time_t mtime) { + struct repository *repo = the_repository; + const struct git_hash_algo *compat = repo->compat_hash_algo; void *buf; unsigned long len; struct object_info oi = OBJECT_INFO_INIT; + struct object_id compat_oid; enum object_type type; char hdr[MAX_HEADER_LEN]; int hdrlen; @@ -2350,8 +2401,15 @@ int force_object_loose(const struct object_id *oid, time_t mtime) oi.contentp = &buf; if (oid_object_info_extended(the_repository, oid, &oi, 0)) return error(_("cannot read object for %s"), oid_to_hex(oid)); + if (compat) { + if (repo_oid_to_algop(repo, oid, compat, &compat_oid)) + return error(_("cannot map object %s to %s"), + oid_to_hex(oid), compat->name); + } hdrlen = format_object_header(hdr, sizeof(hdr), type, len); ret = write_loose_object(oid, hdr, hdrlen, buf, len, mtime, 0); + if (!ret && compat) + ret = repo_add_loose_object_map(the_repository, oid, &compat_oid); free(buf); return ret;
-- 2.41.0