Am 19.03.22 um 01:23 schrieb Ævar Arnfjörð Bjarmason:
> From: Han Xin <hanxin.hx@xxxxxxxxxxxxxxx>
>
> When writing a large blob using "write_loose_object()", we have to pass
> a buffer with the whole content of the blob, and this behavior will
> consume lots of memory and may cause OOM. We will introduce a stream
> version function ("stream_loose_object()") in later commit to resolve
> this issue.
>
> Before introducing that streaming function, do some refactoring on
> "write_loose_object()" to reuse code for both versions.
>
> Rewrite "write_loose_object()" as follows:
>
> 1. Figure out a path for the (temp) object file. This step is only
> used in "write_loose_object()".
>
> 2. Move common steps for starting to write loose objects into a new
> function "start_loose_object_common()".
>
> 3. Compress data.
>
> 4. Move common steps for ending zlib stream into a new function
> "end_loose_object_common()".
>
> 5. Close fd and finalize the object file.
>
> Helped-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
> Helped-by: Jiang Xin <zhiyou.jx@xxxxxxxxxxxxxxx>
> Signed-off-by: Han Xin <hanxin.hx@xxxxxxxxxxxxxxx>
> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
> ---
> object-file.c | 129 ++++++++++++++++++++++++++++++++++----------------
> 1 file changed, 89 insertions(+), 40 deletions(-)
>
> diff --git a/object-file.c b/object-file.c
> index 4c140eda6bf..4fcaf7a36ce 100644
> --- a/object-file.c
> +++ b/object-file.c
> @@ -1943,6 +1943,87 @@ static int create_tmpfile(struct strbuf *tmp, const char *filename)
> return fd;
> }
>
> +/**
> + * Common steps for loose object writers to start writing loose
> + * objects:
> + *
> + * - Create tmpfile for the loose object.
> + * - Setup zlib stream for compression.
> + * - Start to feed header to zlib stream.
> + *
> + * Returns a "fd", which should later be provided to
> + * end_loose_object_common().
> + */
> +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,
> + char *hdr, int hdrlen)
> +{
> + int fd;
> +
> + fd = create_tmpfile(tmp_file, filename);
> + if (fd < 0) {
> + if (flags & HASH_SILENT)
> + return -1;
> + else if (errno == EACCES)
> + return error(_("insufficient permission for adding "
> + "an object to repository database %s"),
> + get_object_directory());
> + else
> + return error_errno(
> + _("unable to create temporary file"));
> + }
> +
> + /* Setup zlib stream for compression */
> + git_deflate_init(stream, zlib_compression_level);
> + stream->next_out = buf;
> + stream->avail_out = buflen;
> + the_hash_algo->init_fn(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);
> +
> + return fd;
> +}
> +
> +/**
> + * Common steps for loose object writers to end writing loose objects:
> + *
> + * - End the compression of zlib stream.
> + * - Get the calculated oid to "parano_oid".
> + * - fsync() and close() the "fd"
> + */
> +static void end_loose_object_common(int fd, int ret, git_hash_ctx *c,
> + git_zstream *stream,
> + struct object_id *parano_oid,
> + const struct object_id *expected_oid,
> + const char *die_msg1_fmt,
> + const char *die_msg2_fmt)
> +{
> + if (ret != Z_STREAM_END)
> + die(_(die_msg1_fmt), ret, expected_oid);
> + ret = git_deflate_end_gently(stream);
> + if (ret != Z_OK)
> + die(_(die_msg2_fmt), ret, expected_oid);
stream_loose_object(), added in patch 5, passes NULL as expected_oid,
but these die() messages need a valid value. end_loose_object_common()
has more parameters than lines of code in its body. Inline it to allow
fully custom messages?
> + the_hash_algo->final_oid_fn(parano_oid, c);
> +
> + /*
> + * We already did a write_buffer() to the "fd", let's fsync()
> + * and close().
> + *
> + * We might still die() on a subsequent sanity check, but
> + * let's not add to that confusion by not flushing any
> + * outstanding writes to disk first.
> + */
> + close_loose_object(fd);
> +}
> +
> static int write_loose_object(const struct object_id *oid, char *hdr,
> int hdrlen, const void *buf, unsigned long len,
> time_t mtime, unsigned flags)
> @@ -1957,28 +2038,11 @@ static int write_loose_object(const struct object_id *oid, char *hdr,
>
> loose_object_path(the_repository, &filename, oid);
>
> - fd = create_tmpfile(&tmp_file, filename.buf);
> - if (fd < 0) {
> - if (flags & HASH_SILENT)
> - return -1;
> - else if (errno == EACCES)
> - return error(_("insufficient permission for adding an object to repository database %s"), get_object_directory());
> - else
> - return error_errno(_("unable to create temporary file"));
> - }
> -
> - /* Set it up */
> - git_deflate_init(&stream, zlib_compression_level);
> - stream.next_out = compressed;
> - stream.avail_out = sizeof(compressed);
> - the_hash_algo->init_fn(&c);
> -
> - /* First header.. */
> - 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);
> + fd = start_loose_object_common(&tmp_file, filename.buf, flags,
> + &stream, compressed, sizeof(compressed),
> + &c, hdr, hdrlen);
> + if (fd < 0)
> + return -1;
>
> /* Then the data itself.. */
> stream.next_in = (void *)buf;
> @@ -1993,24 +2057,9 @@ static int write_loose_object(const struct object_id *oid, char *hdr,
> stream.avail_out = 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 = git_deflate_end_gently(&stream);
> - if (ret != Z_OK)
> - die(_("deflateEnd on object %s failed (%d)"), oid_to_hex(oid),
> - ret);
> - the_hash_algo->final_oid_fn(¶no_oid, &c);
> -
> - /*
> - * We already did a write_buffer() to the "fd", let's fsync()
> - * and close().
> - *
> - * We might still die() on a subsequent sanity check, but
> - * let's not add to that confusion by not flushing any
> - * outstanding writes to disk first.
> - */
> - close_loose_object(fd);
> + end_loose_object_common(fd, ret, &c, &stream, ¶no_oid, oid,
> + N_("unable to deflate new object %s (%d)"),
> + N_("deflateEnd on object %s failed (%d)"));
>
> if (!oideq(oid, ¶no_oid))
> die(_("confused by unstable object source data for %s"),
