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From: Junio C Hamano <gitster@pobox.com>
To: Derrick Stolee <stolee@gmail.com>
Cc: git@vger.kernel.org, sbeller@google.com, pclouds@gmail.com,
	avarab@gmail.com, dstolee@microsoft.com
Subject: Re: [PATCH v3 06/24] multi-pack-index: load into memory
Date: Mon, 09 Jul 2018 12:08:14 -0700
Message-ID: <xmqq36wsdy75.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <20180706005321.124643-7-dstolee@microsoft.com>

Derrick Stolee <stolee@gmail.com> writes:

> +struct multi_pack_index *load_multi_pack_index(const char *object_dir)
> +{
> +	struct multi_pack_index *m = NULL;
> +	int fd;
> +	struct stat st;
> +	size_t midx_size;
> +	void *midx_map = NULL;
> +	uint32_t hash_version;
> +	char *midx_name = get_midx_filename(object_dir);
> +
> +	fd = git_open(midx_name);
> +
> +	if (fd < 0)
> +		goto cleanup_fail;
> +	if (fstat(fd, &st)) {
> +		error_errno(_("failed to read %s"), midx_name);
> +		goto cleanup_fail;
> +	}
> +
> +	midx_size = xsize_t(st.st_size);
> +
> +	if (midx_size < MIDX_MIN_SIZE) {
> +		close(fd);

With the use of "do things normally and jump to cleanup-fail label"
pattern, I think you do not want the close() here (unless you also
assign -1 to fd yourself, but that is a pointless workaround).
Another goto we see above after fstat() failure correctly omits it.

> +		error(_("multi-pack-index file %s is too small"), midx_name);
> +		goto cleanup_fail;
> +	}
> +
> +	FREE_AND_NULL(midx_name);

This correctly calls free-and-null not just free (otherwise we'd
break the cleanup-fail procedure below), which is good.

> +	midx_map = xmmap(NULL, midx_size, PROT_READ, MAP_PRIVATE, fd, 0);
> +
> +	m = xcalloc(1, sizeof(*m) + strlen(object_dir) + 1);
> +	strcpy(m->object_dir, object_dir);

Hmph, I thought we had FLEX_ALLOC_*() convenience functions exactly
for doing things like this more safely.

> +	m->fd = fd;
> +	m->data = midx_map;
> +	m->data_len = midx_size;
> +
> +	m->signature = get_be32(m->data);
> +	if (m->signature != MIDX_SIGNATURE) {
> +		error(_("multi-pack-index signature 0x%08x does not match signature 0x%08x"),
> +		      m->signature, MIDX_SIGNATURE);
> +		goto cleanup_fail;
> +	}
> +
> +	m->version = m->data[MIDX_BYTE_FILE_VERSION];
> +	if (m->version != MIDX_VERSION) {
> +		error(_("multi-pack-index version %d not recognized"),
> +		      m->version);
> +		goto cleanup_fail;
> +	}
> +
> +	hash_version = m->data[MIDX_BYTE_HASH_VERSION];
> +	if (hash_version != MIDX_HASH_VERSION) {
> +		error(_("hash version %u does not match"), hash_version);
> +		goto cleanup_fail;
> +	}
> +	m->hash_len = MIDX_HASH_LEN;
> +
> +	m->num_chunks = m->data[MIDX_BYTE_NUM_CHUNKS];
> +
> +	m->num_packs = get_be32(m->data + MIDX_BYTE_NUM_PACKS);
> +
> +	return m;

> +cleanup_fail:
> +	/* no need to check for NULL when freeing */

I wonder who the target reader of this comment is.  We certainly are
not in the business of C language newbies.

If this _were_ a commit that looked like this:

	-	if (ptr)
	-		free(ptr);
	+	/* no need to check for NULL when freeing */
	+	free(ptr);

then it might be more understandable, but it still is wrong (such a
comment does not help understanding the new code, which is the only
thing the people who read the comment sees, without knowing what was
there previously---it belongs to the commit log message as a rationale
to make that change).

> diff --git a/midx.h b/midx.h
> index dbdbe9f873..2d83dd9ec1 100644
> --- a/midx.h
> +++ b/midx.h
> @@ -1,6 +1,10 @@
>  #ifndef __MIDX_H__
>  #define __MIDX_H__
>  
> +struct multi_pack_index;

I actually was quite surprised that this struct is defined in
object-store.h and not here.  It feels the other way around.

The raw_object_store needs to know that such an in-core structure
might exist as an optional feature in an object store, but as an
optional feature, I suspect that it has a pointer to an instance of
multi_pack_index, instead of embedding the struct itself in it, so I
would have expected to see an "I am only telling you that there is a
struct with this name, but I am leaving it opaque as you do not have
any business looking inside the struct yourself.  You only need to
be aware of the type's existence and a pointer to it so that you can
call helpers that know what's inside and that should be sufficient
for your needs." decl like this in object-store.h and instead an
actual implementation in here.

  parent reply index

Thread overview: 192+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-07 14:03 [PATCH 00/23] Multi-pack-index (MIDX) Derrick Stolee
2018-06-07 14:03 ` [PATCH 01/23] midx: add design document Derrick Stolee
2018-06-11 19:04   ` Stefan Beller
2018-06-18 18:48     ` Derrick Stolee
2018-06-07 14:03 ` [PATCH 02/23] midx: add midx format details to pack-format.txt Derrick Stolee
2018-06-11 19:19   ` Stefan Beller
2018-06-18 19:01     ` Derrick Stolee
2018-06-18 19:41       ` Stefan Beller
2018-06-07 14:03 ` [PATCH 03/23] midx: add midx builtin Derrick Stolee
2018-06-07 17:20   ` Duy Nguyen
2018-06-18 19:23     ` Derrick Stolee
2018-06-11 21:02   ` Stefan Beller
2018-06-18 19:40     ` Derrick Stolee
2018-06-18 19:55       ` Stefan Beller
2018-06-18 19:58         ` Derrick Stolee
2018-06-07 14:03 ` [PATCH 04/23] midx: add 'write' subcommand and basic wiring Derrick Stolee
2018-06-07 17:27   ` Duy Nguyen
2018-06-07 14:03 ` [PATCH 05/23] midx: write header information to lockfile Derrick Stolee
2018-06-07 17:35   ` Duy Nguyen
2018-06-12 15:00   ` Duy Nguyen
2018-06-19 12:54     ` Derrick Stolee
2018-06-19 14:59       ` Duy Nguyen
2018-06-19 15:24         ` Derrick Stolee
2018-06-07 14:03 ` [PATCH 06/23] midx: struct midxed_git and 'read' subcommand Derrick Stolee
2018-06-07 17:54   ` Duy Nguyen
2018-06-20 13:13     ` Derrick Stolee
2018-06-07 18:31   ` Duy Nguyen
2018-06-20 13:33     ` Derrick Stolee
2018-06-20 15:07       ` Duy Nguyen
2018-06-20 16:39         ` Derrick Stolee
2018-06-07 14:03 ` [PATCH 07/23] midx: expand test data Derrick Stolee
2018-06-07 14:03 ` [PATCH 08/23] midx: read packfiles from pack directory Derrick Stolee
2018-06-07 18:03   ` Duy Nguyen
2018-06-20 16:33     ` [PATCH] packfile: generalize pack directory list Derrick Stolee
2018-06-07 14:03 ` [PATCH 09/23] midx: write pack names in chunk Derrick Stolee
2018-06-07 18:26   ` Duy Nguyen
2018-06-21 15:25     ` Derrick Stolee
2018-06-21 17:38       ` Junio C Hamano
2018-06-22 18:25         ` Derrick Stolee
2018-06-22 18:31           ` Junio C Hamano
2018-06-22 18:32             ` Derrick Stolee
2018-06-07 14:03 ` [PATCH 10/23] midx: write a lookup into the pack names chunk Derrick Stolee
2018-06-09 16:43   ` Duy Nguyen
2018-06-21 17:23     ` Derrick Stolee
2018-06-07 14:03 ` [PATCH 11/23] midx: sort and deduplicate objects from packfiles Derrick Stolee
2018-06-09 17:07   ` Duy Nguyen
2018-06-21 17:54     ` Derrick Stolee
2018-06-07 14:03 ` [PATCH 12/23] midx: write object ids in a chunk Derrick Stolee
2018-06-09 17:25   ` Duy Nguyen
2018-06-07 14:03 ` [PATCH 13/23] midx: write object id fanout chunk Derrick Stolee
2018-06-09 17:28   ` Duy Nguyen
2018-06-21 19:49     ` Derrick Stolee
2018-06-07 14:03 ` [PATCH 14/23] midx: write object offsets Derrick Stolee
2018-06-09 17:41   ` Duy Nguyen
2018-06-07 14:03 ` [PATCH 15/23] midx: create core.midx config setting Derrick Stolee
2018-06-07 14:03 ` [PATCH 16/23] midx: prepare midxed_git struct Derrick Stolee
2018-06-09 17:47   ` Duy Nguyen
2018-06-07 14:03 ` [PATCH 17/23] midx: read objects from multi-pack-index Derrick Stolee
2018-06-09 17:56   ` Duy Nguyen
2018-06-21 20:03     ` Derrick Stolee
2018-06-07 14:03 ` [PATCH 18/23] midx: use midx in abbreviation calculations Derrick Stolee
2018-06-09 18:01   ` Duy Nguyen
2018-06-22 18:38     ` Derrick Stolee
2018-06-07 14:03 ` [PATCH 19/23] midx: use existing midx when writing new one Derrick Stolee
2018-06-07 14:03 ` [PATCH 20/23] midx: use midx in approximate_object_count Derrick Stolee
2018-06-09 18:03   ` Duy Nguyen
2018-06-22 18:39     ` Derrick Stolee
2018-06-07 14:03 ` [PATCH 21/23] midx: prevent duplicate packfile loads Derrick Stolee
2018-06-09 18:05   ` Duy Nguyen
2018-06-07 14:03 ` [PATCH 22/23] midx: use midx to find ref-deltas Derrick Stolee
2018-06-07 14:03 ` [PATCH 23/23] midx: clear midx on repack Derrick Stolee
2018-06-09 18:13   ` Duy Nguyen
2018-06-22 18:44     ` Derrick Stolee
2018-06-07 14:06 ` [PATCH 00/23] Multi-pack-index (MIDX) Derrick Stolee
2018-06-07 14:45 ` Ævar Arnfjörð Bjarmason
2018-06-07 14:54   ` Derrick Stolee
2018-06-25 14:34 ` [PATCH v2 00/24] " Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 01/24] multi-pack-index: add design document Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 02/24] multi-pack-index: add format details Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 03/24] multi-pack-index: add builtin Derrick Stolee
2018-06-25 19:15     ` Junio C Hamano
2018-06-25 14:34   ` [PATCH v2 04/24] multi-pack-index: add 'write' verb Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 05/24] midx: write header information to lockfile Derrick Stolee
2018-06-25 19:19     ` Junio C Hamano
2018-07-05 19:13       ` Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 06/24] multi-pack-index: load into memory Derrick Stolee
2018-06-25 19:38     ` Junio C Hamano
2018-07-05 14:19       ` Derrick Stolee
2018-07-05 18:58         ` Eric Sunshine
2018-07-06 19:20           ` Junio C Hamano
2018-06-25 14:34   ` [PATCH v2 07/24] multi-pack-index: expand test data Derrick Stolee
2018-06-25 19:45     ` Junio C Hamano
2018-06-25 14:34   ` [PATCH v2 08/24] packfile: generalize pack directory list Derrick Stolee
2018-06-25 19:57     ` Junio C Hamano
2018-06-25 14:34   ` [PATCH v2 09/24] multi-pack-index: read packfile list Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 10/24] multi-pack-index: write pack names in chunk Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 11/24] midx: read pack names into array Derrick Stolee
2018-06-25 23:52     ` Eric Sunshine
2018-06-25 14:34   ` [PATCH v2 12/24] midx: sort and deduplicate objects from packfiles Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 13/24] midx: write object ids in a chunk Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 14/24] midx: write object id fanout chunk Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 15/24] midx: write object offsets Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 16/24] config: create core.multiPackIndex setting Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 17/24] midx: prepare midxed_git struct Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 18/24] midx: read objects from multi-pack-index Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 19/24] midx: use midx in abbreviation calculations Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 20/24] midx: use existing midx when writing new one Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 21/24] midx: use midx in approximate_object_count Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 22/24] midx: prevent duplicate packfile loads Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 23/24] packfile: skip loading index if in multi-pack-index Derrick Stolee
2018-06-25 14:34   ` [PATCH v2 24/24] midx: clear midx on repack Derrick Stolee
2018-07-06  0:52   ` [PATCH v3 00/24] Multi-pack-index (MIDX) Derrick Stolee
2018-07-06  0:52     ` [PATCH v3 01/24] multi-pack-index: add design document Derrick Stolee
2018-07-06  0:52     ` [PATCH v3 02/24] multi-pack-index: add format details Derrick Stolee
2018-07-06  0:53     ` [PATCH v3 03/24] multi-pack-index: add builtin Derrick Stolee
2018-07-06  3:54       ` Eric Sunshine
2018-07-06  0:53     ` [PATCH v3 04/24] multi-pack-index: add 'write' verb Derrick Stolee
2018-07-06  4:07       ` Eric Sunshine
2018-07-06  0:53     ` [PATCH v3 05/24] midx: write header information to lockfile Derrick Stolee
2018-07-06  0:53     ` [PATCH v3 06/24] multi-pack-index: load into memory Derrick Stolee
2018-07-06  4:19       ` Eric Sunshine
2018-07-06  5:18         ` Eric Sunshine
2018-07-09 19:08       ` Junio C Hamano [this message]
2018-07-12 16:06         ` Derrick Stolee
2018-07-06  0:53     ` [PATCH v3 07/24] multi-pack-index: expand test data Derrick Stolee
2018-07-06  4:36       ` Eric Sunshine
2018-07-06  5:20         ` Eric Sunshine
2018-07-12 14:10         ` Derrick Stolee
2018-07-12 18:02           ` Eric Sunshine
2018-07-12 18:06             ` Derrick Stolee
2018-07-06  0:53     ` [PATCH v3 08/24] packfile: generalize pack directory list Derrick Stolee
2018-07-06  0:53     ` [PATCH v3 09/24] multi-pack-index: read packfile list Derrick Stolee
2018-07-06  0:53     ` [PATCH v3 10/24] multi-pack-index: write pack names in chunk Derrick Stolee
2018-07-06  0:53     ` [PATCH v3 11/24] midx: read pack names into array Derrick Stolee
2018-07-06  4:58       ` Eric Sunshine
2018-07-06  0:53     ` [PATCH v3 12/24] midx: sort and deduplicate objects from packfiles Derrick Stolee
2018-07-06  0:53     ` [PATCH v3 13/24] midx: write object ids in a chunk Derrick Stolee
2018-07-06  5:04       ` Eric Sunshine
2018-07-06  0:53     ` [PATCH v3 14/24] midx: write object id fanout chunk Derrick Stolee
2018-07-06  0:53     ` [PATCH v3 15/24] midx: write object offsets Derrick Stolee
2018-07-06  5:27       ` Eric Sunshine
2018-07-12 16:33         ` Derrick Stolee
2018-07-06  0:53     ` [PATCH v3 16/24] config: create core.multiPackIndex setting Derrick Stolee
2018-07-06  5:39       ` Eric Sunshine
2018-07-12 13:19         ` Derrick Stolee
2018-07-12 16:30           ` Derrick Stolee
2018-07-11  9:48       ` SZEDER Gábor
2018-07-12 13:01         ` Derrick Stolee
2018-07-12 13:31           ` SZEDER Gábor
2018-07-12 15:40             ` Derrick Stolee
2018-07-12 17:29             ` Junio C Hamano
2018-07-06  0:53     ` [PATCH v3 17/24] midx: prepare midxed_git struct Derrick Stolee
2018-07-06  5:41       ` Eric Sunshine
2018-07-06  0:53     ` [PATCH v3 18/24] midx: read objects from multi-pack-index Derrick Stolee
2018-07-06  0:53     ` [PATCH v3 19/24] midx: use midx in abbreviation calculations Derrick Stolee
2018-07-06  0:53     ` [PATCH v3 20/24] midx: use existing midx when writing new one Derrick Stolee
2018-07-06  0:53     ` [PATCH v3 21/24] midx: use midx in approximate_object_count Derrick Stolee
2018-07-06  0:53     ` [PATCH v3 22/24] midx: prevent duplicate packfile loads Derrick Stolee
2018-07-06  0:53     ` [PATCH v3 23/24] packfile: skip loading index if in multi-pack-index Derrick Stolee
2018-07-06  0:53     ` [PATCH v3 24/24] midx: clear midx on repack Derrick Stolee
2018-07-06  5:52       ` Eric Sunshine
2018-07-12 19:39     ` [PATCH v4 00/23] Multi-pack-index (MIDX) Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 01/23] multi-pack-index: add design document Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 02/23] multi-pack-index: add format details Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 03/23] multi-pack-index: add builtin Derrick Stolee
2018-07-20 18:22         ` Junio C Hamano
2018-07-20 22:15           ` brian m. carlson
2018-07-20 22:28             ` Junio C Hamano
2018-07-12 19:39       ` [PATCH v4 04/23] multi-pack-index: add 'write' verb Derrick Stolee
2018-07-12 22:56         ` Eric Sunshine
2018-07-12 19:39       ` [PATCH v4 05/23] midx: write header information to lockfile Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 06/23] multi-pack-index: load into memory Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 07/23] t5319: expand test data Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 08/23] packfile: generalize pack directory list Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 09/23] multi-pack-index: read packfile list Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 10/23] multi-pack-index: write pack names in chunk Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 11/23] midx: read pack names into array Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 12/23] midx: sort and deduplicate objects from packfiles Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 13/23] midx: write object ids in a chunk Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 14/23] midx: write object id fanout chunk Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 15/23] midx: write object offsets Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 16/23] config: create core.multiPackIndex setting Derrick Stolee
2018-07-12 21:05         ` Junio C Hamano
2018-07-13  0:50           ` Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 17/23] midx: read objects from multi-pack-index Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 18/23] midx: use midx in abbreviation calculations Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 19/23] midx: use existing midx when writing new one Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 20/23] midx: use midx in approximate_object_count Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 21/23] midx: prevent duplicate packfile loads Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 22/23] packfile: skip loading index if in multi-pack-index Derrick Stolee
2018-07-12 19:39       ` [PATCH v4 23/23] midx: clear midx on repack Derrick Stolee
2018-07-12 21:11       ` [PATCH v4 00/23] Multi-pack-index (MIDX) Junio C Hamano

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