Any suggestions?
Han Xin <chiyutianyi@xxxxxxxxx> 于2021年10月9日周六 下午4:21写道：
>
> From: Han Xin <hanxin.hx@xxxxxxxxxxxxxxx>
>
> When calling "unpack_non_delta_entry()", will allocate full memory for
> the whole size of the unpacked object and write the buffer to loose file
> on disk. This may lead to OOM for the git-unpack-objects process when
> unpacking a very large object.
>
> In function "unpack_delta_entry()", will also allocate full memory to
> buffer the whole delta, but since there will be no delta for an object
> larger than "core.bigFileThreshold", this issue is moderate.
>
> To resolve the OOM issue in "git-unpack-objects", we can unpack large
> object to file in stream, and use the setting of "core.bigFileThreshold" as
> the threshold for large object.
>
> Reviewed-by: Jiang Xin <zhiyou.jx@xxxxxxxxxxxxxxx>
> Signed-off-by: Han Xin <hanxin.hx@xxxxxxxxxxxxxxx>
> ---
> builtin/unpack-objects.c | 41 +++++++-
> object-file.c | 149 +++++++++++++++++++++++++++---
> object-store.h | 9 ++
> t/t5590-receive-unpack-objects.sh | 92 ++++++++++++++++++
> 4 files changed, 279 insertions(+), 12 deletions(-)
> create mode 100755 t/t5590-receive-unpack-objects.sh
>
> diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c
> index 4a9466295b..8ac77e60a8 100644
> --- a/builtin/unpack-objects.c
> +++ b/builtin/unpack-objects.c
> @@ -320,11 +320,50 @@ static void added_object(unsigned nr, enum object_type type,
> }
> }
>
> +static void fill_stream(struct git_zstream *stream)
> +{
> + stream->next_in = fill(1);
> + stream->avail_in = len;
> +}
> +
> +static void use_stream(struct git_zstream *stream)
> +{
> + use(len - stream->avail_in);
> +}
> +
> +static void write_stream_blob(unsigned nr, unsigned long size)
> +{
> + struct git_zstream_reader reader;
> + struct object_id *oid = &obj_list[nr].oid;
> +
> + reader.fill = &fill_stream;
> + reader.use = &use_stream;
> +
> + if (write_stream_object_file(&reader, size, type_name(OBJ_BLOB),
> + oid, dry_run))
> + die("failed to write object in stream");
> + if (strict && !dry_run) {
> + struct blob *blob = lookup_blob(the_repository, oid);
> + if (blob)
> + blob->object.flags |= FLAG_WRITTEN;
> + else
> + die("invalid blob object from stream");
> + }
> + obj_list[nr].obj = NULL;
> +}
> +
> static void unpack_non_delta_entry(enum object_type type, unsigned long size,
> unsigned nr)
> {
> - void *buf = get_data(size);
> + void *buf;
> +
> + /* Write large blob in stream without allocating full buffer. */
> + if (type == OBJ_BLOB && size > big_file_threshold) {
> + write_stream_blob(nr, size);
> + return;
> + }
>
> + buf = get_data(size);
> if (!dry_run && buf)
> write_object(nr, type, buf, size);
> else
> diff --git a/object-file.c b/object-file.c
> index a8be899481..06c1693675 100644
> --- a/object-file.c
> +++ b/object-file.c
> @@ -1913,6 +1913,28 @@ static int create_tmpfile(struct strbuf *tmp, const char *filename)
> return fd;
> }
>
> +static int write_object_buffer(struct git_zstream *stream, git_hash_ctx *c,
> + int fd, unsigned char *compressed,
> + int compressed_len, const void *buf,
> + size_t len, int flush)
> +{
> + int ret;
> +
> + stream->next_in = (void *)buf;
> + stream->avail_in = len;
> + do {
> + unsigned char *in0 = stream->next_in;
> + ret = git_deflate(stream, flush);
> + the_hash_algo->update_fn(c, in0, stream->next_in - in0);
> + if (write_buffer(fd, compressed, stream->next_out - compressed) < 0)
> + die(_("unable to write loose object file"));
> + stream->next_out = compressed;
> + stream->avail_out = compressed_len;
> + } while (ret == Z_OK);
> +
> + return ret;
> +}
> +
> static int write_loose_object(const struct object_id *oid, char *hdr,
> int hdrlen, const void *buf, unsigned long len,
> time_t mtime)
> @@ -1949,17 +1971,9 @@ static int write_loose_object(const struct object_id *oid, char *hdr,
> the_hash_algo->update_fn(&c, hdr, hdrlen);
>
> /* Then the data itself.. */
> - stream.next_in = (void *)buf;
> - stream.avail_in = len;
> - do {
> - unsigned char *in0 = stream.next_in;
> - ret = git_deflate(&stream, Z_FINISH);
> - the_hash_algo->update_fn(&c, in0, stream.next_in - in0);
> - if (write_buffer(fd, compressed, stream.next_out - compressed) < 0)
> - die(_("unable to write loose object file"));
> - stream.next_out = compressed;
> - stream.avail_out = sizeof(compressed);
> - } while (ret == Z_OK);
> + ret = write_object_buffer(&stream, &c, fd, compressed,
> + sizeof(compressed), buf, len,
> + Z_FINISH);
>
> if (ret != Z_STREAM_END)
> die(_("unable to deflate new object %s (%d)"), oid_to_hex(oid),
> @@ -2020,6 +2034,119 @@ int write_object_file(const void *buf, unsigned long len, const char *type,
> return write_loose_object(oid, hdr, hdrlen, buf, len, 0);
> }
>
> +int write_stream_object_file(struct git_zstream_reader *reader,
> + unsigned long len, const char *type,
> + struct object_id *oid,
> + int dry_run)
> +{
> + git_zstream istream, ostream;
> + unsigned char buf[8192], compressed[4096];
> + char hdr[MAX_HEADER_LEN];
> + int istatus, ostatus, fd = 0, hdrlen, dirlen, flush = 0;
> + int ret = 0;
> + git_hash_ctx c;
> + struct strbuf tmp_file = STRBUF_INIT;
> + struct strbuf filename = STRBUF_INIT;
> +
> + /* Write tmpfile in objects dir, because oid is unknown */
> + if (!dry_run) {
> + strbuf_addstr(&filename, the_repository->objects->odb->path);
> + strbuf_addch(&filename, '/');
> + fd = create_tmpfile(&tmp_file, filename.buf);
> + if (fd < 0) {
> + if (errno == EACCES)
> + ret = error(_("insufficient permission for adding an object to repository database %s"),
> + get_object_directory());
> + else
> + ret = error_errno(_("unable to create temporary file"));
> + goto cleanup;
> + }
> + }
> +
> + memset(&istream, 0, sizeof(istream));
> + istream.next_out = buf;
> + istream.avail_out = sizeof(buf);
> + git_inflate_init(&istream);
> +
> + if (!dry_run) {
> + /* Set it up */
> + git_deflate_init(&ostream, zlib_compression_level);
> + ostream.next_out = compressed;
> + ostream.avail_out = sizeof(compressed);
> + the_hash_algo->init_fn(&c);
> +
> + /* First header */
> + hdrlen = xsnprintf(hdr, sizeof(hdr), "%s %" PRIuMAX, type,
> + (uintmax_t)len) + 1;
> + ostream.next_in = (unsigned char *)hdr;
> + ostream.avail_in = hdrlen;
> + while (git_deflate(&ostream, 0) == Z_OK)
> + ; /* nothing */
> + the_hash_algo->update_fn(&c, hdr, hdrlen);
> + }
> +
> + /* Then the data itself */
> + do {
> + unsigned char *last_out = istream.next_out;
> + reader->fill(&istream);
> + istatus = git_inflate(&istream, 0);
> + if (istatus == Z_STREAM_END)
> + flush = Z_FINISH;
> + reader->use(&istream);
> + if (!dry_run)
> + ostatus = write_object_buffer(&ostream, &c, fd, compressed,
> + sizeof(compressed), last_out,
> + istream.next_out - last_out,
> + flush);
> + istream.next_out = buf;
> + istream.avail_out = sizeof(buf);
> + } while (istatus == Z_OK);
> +
> + if (istream.total_out != len || istatus != Z_STREAM_END)
> + die( _("inflate returned %d"), istatus);
> + git_inflate_end(&istream);
> +
> + if (dry_run)
> + goto cleanup;
> +
> + if (ostatus != Z_STREAM_END)
> + die(_("unable to deflate new object (%d)"), ostatus);
> + ostatus = git_deflate_end_gently(&ostream);
> + if (ostatus != Z_OK)
> + die(_("deflateEnd on object failed (%d)"), ostatus);
> + the_hash_algo->final_fn(oid->hash, &c);
> + close_loose_object(fd);
> +
> + /* We get the oid now */
> + loose_object_path(the_repository, &filename, oid);
> +
> + dirlen = directory_size(filename.buf);
> + if (dirlen) {
> + struct strbuf dir = STRBUF_INIT;
> + /*
> + * Make sure the directory exists; note that the contents
> + * of the buffer are undefined after mkstemp returns an
> + * error, so we have to rewrite the whole buffer from
> + * scratch.
> + */
> + strbuf_add(&dir, filename.buf, dirlen - 1);
> + if (mkdir(dir.buf, 0777) && errno != EEXIST) {
> + unlink_or_warn(tmp_file.buf);
> + strbuf_release(&dir);
> + ret = -1;
> + goto cleanup;
> + }
> + strbuf_release(&dir);
> + }
> +
> + ret = finalize_object_file(tmp_file.buf, filename.buf);
> +
> +cleanup:
> + strbuf_release(&tmp_file);
> + strbuf_release(&filename);
> + return ret;
> +}
> +
> int hash_object_file_literally(const void *buf, unsigned long len,
> const char *type, struct object_id *oid,
> unsigned flags)
> diff --git a/object-store.h b/object-store.h
> index d24915ced1..12b113ef93 100644
> --- a/object-store.h
> +++ b/object-store.h
> @@ -33,6 +33,11 @@ struct object_directory {
> char *path;
> };
>
> +struct git_zstream_reader {
> + void (*fill)(struct git_zstream *);
> + void (*use)(struct git_zstream *);
> +};
> +
> KHASH_INIT(odb_path_map, const char * /* key: odb_path */,
> struct object_directory *, 1, fspathhash, fspatheq)
>
> @@ -225,6 +230,10 @@ int hash_object_file(const struct git_hash_algo *algo, const void *buf,
> int write_object_file(const void *buf, unsigned long len,
> const char *type, struct object_id *oid);
>
> +int write_stream_object_file(struct git_zstream_reader *reader,
> + unsigned long len, const char *type,
> + struct object_id *oid, int dry_run);
> +
> int hash_object_file_literally(const void *buf, unsigned long len,
> const char *type, struct object_id *oid,
> unsigned flags);
> diff --git a/t/t5590-receive-unpack-objects.sh b/t/t5590-receive-unpack-objects.sh
> new file mode 100755
> index 0000000000..7e63dfc0db
> --- /dev/null
> +++ b/t/t5590-receive-unpack-objects.sh
> @@ -0,0 +1,92 @@
> +#!/bin/sh
> +#
> +# Copyright (c) 2021 Han Xin
> +#
> +
> +test_description='Test unpack-objects when receive pack'
> +
> +GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
> +export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
> +
> +. ./test-lib.sh
> +
> +test_expect_success "create commit with big blobs (1.5 MB)" '
> + test-tool genrandom foo 1500000 >big-blob &&
> + test_commit --append foo big-blob &&
> + test-tool genrandom bar 1500000 >big-blob &&
> + test_commit --append bar big-blob &&
> + (
> + cd .git &&
> + find objects/?? -type f | sort
> + ) >expect &&
> + git repack -ad
> +'
> +
> +test_expect_success 'setup GIT_ALLOC_LIMIT to 1MB' '
> + GIT_ALLOC_LIMIT=1m &&
> + export GIT_ALLOC_LIMIT
> +'
> +
> +test_expect_success 'prepare dest repository' '
> + git init --bare dest.git &&
> + git -C dest.git config core.bigFileThreshold 2m &&
> + git -C dest.git config receive.unpacklimit 100
> +'
> +
> +test_expect_success 'fail to push: cannot allocate' '
> + test_must_fail git push dest.git HEAD 2>err &&
> + test_i18ngrep "remote: fatal: attempting to allocate" err &&
> + (
> + cd dest.git &&
> + find objects/?? -type f | sort
> + ) >actual &&
> + ! test_cmp expect actual
> +'
> +
> +test_expect_success 'set a lower bigfile threshold' '
> + git -C dest.git config core.bigFileThreshold 1m
> +'
> +
> +test_expect_success 'unpack big object in stream' '
> + git push dest.git HEAD &&
> + git -C dest.git fsck &&
> + (
> + cd dest.git &&
> + find objects/?? -type f | sort
> + ) >actual &&
> + test_cmp expect actual
> +'
> +
> +test_expect_success 'setup for unpack-objects dry-run test' '
> + PACK=$(echo main | git pack-objects --progress --revs test) &&
> + unset GIT_ALLOC_LIMIT &&
> + git init --bare unpack-test.git
> +'
> +
> +test_expect_success 'unpack-objects dry-run with large threshold' '
> + (
> + cd unpack-test.git &&
> + git config core.bigFileThreshold 2m &&
> + git unpack-objects -n <../test-$PACK.pack
> + ) &&
> + (
> + cd unpack-test.git &&
> + find objects/ -type f
> + ) >actual &&
> + test_must_be_empty actual
> +'
> +
> +test_expect_success 'unpack-objects dry-run with small threshold' '
> + (
> + cd unpack-test.git &&
> + git config core.bigFileThreshold 1m &&
> + git unpack-objects -n <../test-$PACK.pack
> + ) &&
> + (
> + cd unpack-test.git &&
> + find objects/ -type f
> + ) >actual &&
> + test_must_be_empty actual
> +'
> +
> +test_done
> --
> 2.33.0.1.g09a6bb964f.dirty
>
