From patchwork Wed Jul 20 14:05:11 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Abhradeep Chakraborty X-Patchwork-Id: 12924034 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5E070C43334 for ; Wed, 20 Jul 2022 14:05:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231739AbiGTOFg (ORCPT ); Wed, 20 Jul 2022 10:05:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53252 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232137AbiGTOFY (ORCPT ); Wed, 20 Jul 2022 10:05:24 -0400 Received: from mail-wm1-x336.google.com (mail-wm1-x336.google.com [IPv6:2a00:1450:4864:20::336]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5D91614D36 for ; Wed, 20 Jul 2022 07:05:22 -0700 (PDT) Received: by mail-wm1-x336.google.com with SMTP id f24-20020a1cc918000000b003a30178c022so1417376wmb.3 for ; Wed, 20 Jul 2022 07:05:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=message-id:in-reply-to:references:from:date:subject:fcc :content-transfer-encoding:mime-version:to:cc; bh=LiFZMg7EZo4l1VELmshpace64NzkHeuYHqN/heEKhoY=; b=NT5otXjs7Ug7yTyeUUqvlHOLEa/AZGcpgjOYBXLROkcayu95rD3YdG119FzuvYDooq Dheo6l6OWhXh9gDdGPqHA+M/qftpKXun4gtlI90WKc6w4/dNXFgk2z3N06aWxcLDGV0a oju5bQWdVLTSRlmUhOcRaLH5TEJed/VbYsDZ2c/RkDLILjmjLlIHz4zC/Gcp+SX2Pu48 IGMRuNBdS77DCQu+5eUWmdNZeCPrxG1ZU5HCX7srWDxcQmevMfKXh0xWaU2k7/CiLYEe zLB2tHBYCc0hUQj3TwwwmAiWbVjmbJi+ss2GJ7WZ+IPm/WXKEK/PIAU8vnuIAIQkM8Gu OuAw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:in-reply-to:references:from:date :subject:fcc:content-transfer-encoding:mime-version:to:cc; bh=LiFZMg7EZo4l1VELmshpace64NzkHeuYHqN/heEKhoY=; b=Klz5DGLSniNi1Lap+Gug24YtmCM05cKYNGGPbqGFqmFPZR8beLw6E1+DBjOW53cEd4 G40UB6U+OzPNoBFr6alS6CtiadG6FH3jYAb9UxYmTCaOu8NcCAD1HMJOmDPFCln9vmB6 ecJsOY+S3as6vxP4jaZCN7ipFKkW9SVW4APJUw/1R5g0YeSswqERzyouBCYpCXEh+Qib Dvz6K1hh96lhC9gV3JXeO9MncyXb3itMl/EAaVfgBcXxd5cp1UY1LTc7V4Ncy04n0mSt BWWDA0jloUrr/ibuEYho1fjCDFWR+wlVHoResSXinJ9+DhWgvJ3TiGoEtGAKejkMUNuA Q3Kg== X-Gm-Message-State: AJIora/Oz25YxTBBHOfPzCe6QkomDMfIlOHwFiL9GJ5BSIcYI/GZFK2y 5J8qvJpFQ1i2Lv4AcBjJ8l6CaxqpstU= X-Google-Smtp-Source: AGRyM1urpM5o5kIn07JOhoXIdoEKoHYmV988Gzxi77g5HBFPjgQ5WPL8/VyLtkEcG2WDPph7rABb5Q== X-Received: by 2002:a05:600c:3ca2:b0:3a0:1825:2e6b with SMTP id bg34-20020a05600c3ca200b003a018252e6bmr3911583wmb.132.1658325920120; Wed, 20 Jul 2022 07:05:20 -0700 (PDT) Received: from [127.0.0.1] ([13.74.141.28]) by smtp.gmail.com with ESMTPSA id 8-20020a05600c024800b003a0375c4f73sm2598580wmj.44.2022.07.20.07.05.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Jul 2022 07:05:19 -0700 (PDT) Message-Id: In-Reply-To: References: Date: Wed, 20 Jul 2022 14:05:11 +0000 Subject: [PATCH v4 4/6] pack-bitmap: prepare to read lookup table extension Fcc: Sent MIME-Version: 1.0 To: git@vger.kernel.org Cc: Taylor Blau , Kaartic Sivaram , Derrick Stolee , Philip Oakley , Martin =?utf-8?b?w4VncmVu?= , Abhradeep Chakraborty , Abhradeep Chakraborty Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org From: Abhradeep Chakraborty From: Abhradeep Chakraborty Earlier change teaches Git to write bitmap lookup table. But Git does not know how to parse them. Teach Git to parse the existing bitmap lookup table. The older versions of Git are not affected by it. Those versions ignore the lookup table. Mentored-by: Taylor Blau Co-Mentored-by: Kaartic Sivaraam Signed-off-by: Abhradeep Chakraborty --- pack-bitmap.c | 278 ++++++++++++++++++++++++++++++++++++++-- pack-bitmap.h | 9 ++ t/t5310-pack-bitmaps.sh | 22 ++++ 3 files changed, 299 insertions(+), 10 deletions(-) diff --git a/pack-bitmap.c b/pack-bitmap.c index 36134222d7a..7c66d4379f5 100644 --- a/pack-bitmap.c +++ b/pack-bitmap.c @@ -82,6 +82,12 @@ struct bitmap_index { /* The checksum of the packfile or MIDX; points into map. */ const unsigned char *checksum; + /* + * If not NULL, this point into the commit table extension + * (within the memory mapped region `map`). + */ + unsigned char *table_lookup; + /* * Extended index. * @@ -185,6 +191,16 @@ static int load_bitmap_header(struct bitmap_index *index) index->hashes = (void *)(index_end - cache_size); index_end -= cache_size; } + + if (flags & BITMAP_OPT_LOOKUP_TABLE) { + size_t table_size = st_mult(ntohl(header->entry_count), + BITMAP_LOOKUP_TABLE_TRIPLET_WIDTH); + if (table_size > index_end - index->map - header_size) + return error(_("corrupted bitmap index file (too short to fit lookup table)")); + if (git_env_bool("GIT_TEST_READ_COMMIT_TABLE", 1)) + index->table_lookup = (void *)(index_end - table_size); + index_end -= table_size; + } } index->entry_count = ntohl(header->entry_count); @@ -211,11 +227,13 @@ static struct stored_bitmap *store_bitmap(struct bitmap_index *index, hash_pos = kh_put_oid_map(index->bitmaps, stored->oid, &ret); - /* a 0 return code means the insertion succeeded with no changes, - * because the SHA1 already existed on the map. this is bad, there - * shouldn't be duplicated commits in the index */ + /* + * A 0 return code means the insertion succeeded with no changes, + * because the SHA1 already existed on the map. This is bad, there + * shouldn't be duplicated commits in the index. + */ if (ret == 0) { - error("Duplicate entry in bitmap index: %s", oid_to_hex(oid)); + error(_("duplicate entry in bitmap index: %s"), oid_to_hex(oid)); return NULL; } @@ -470,7 +488,7 @@ static int load_bitmap(struct bitmap_index *bitmap_git) !(bitmap_git->tags = read_bitmap_1(bitmap_git))) goto failed; - if (load_bitmap_entries_v1(bitmap_git) < 0) + if (!bitmap_git->table_lookup && load_bitmap_entries_v1(bitmap_git) < 0) goto failed; return 0; @@ -557,13 +575,241 @@ struct include_data { struct bitmap *seen; }; +struct bitmap_lookup_table_triplet { + uint32_t commit_pos; + uint64_t offset; + uint32_t xor_row; +}; + +struct bitmap_lookup_table_xor_item { + struct object_id oid; + uint64_t offset; +}; + +/* + * Given a `triplet` struct pointer and pointer `p`, this + * function reads the triplet beginning at `p` into the struct. + * Note that this function assumes that there is enough memory + * left for filling the `triplet` struct from `p`. + */ +static int lookup_table_get_triplet_by_pointer(struct bitmap_lookup_table_triplet *triplet, + const unsigned char *p) +{ + if (!triplet) + return -1; + + triplet->commit_pos = get_be32(p); + p += sizeof(uint32_t); + triplet->offset = get_be64(p); + p += sizeof(uint64_t); + triplet->xor_row = get_be32(p); + return 0; +} + +/* + * This function gets the raw triplet from `row`'th row in the + * lookup table and fills that data to the `triplet`. + */ +static int lookup_table_get_triplet(struct bitmap_index *bitmap_git, + uint32_t pos, + struct bitmap_lookup_table_triplet *triplet) +{ + unsigned char *p = NULL; + if (pos >= bitmap_git->entry_count) + return error(_("corrupt bitmap lookup table: triplet position out of index")); + + p = bitmap_git->table_lookup + st_mult(pos, BITMAP_LOOKUP_TABLE_TRIPLET_WIDTH); + + return lookup_table_get_triplet_by_pointer(triplet, p); +} + +/* + * Searches for a matching triplet. `commit_pos` is a pointer + * to the wanted commit position value. `table_entry` points to + * a triplet in lookup table. The first 4 bytes of each + * triplet (pointed by `table_entry`) are compared with `*commit_pos`. + */ +static int triplet_cmp(const void *commit_pos, const void *table_entry) +{ + + uint32_t a = *(uint32_t *)commit_pos; + uint32_t b = get_be32(table_entry); + if (a > b) + return 1; + else if (a < b) + return -1; + + return 0; +} + +static uint32_t bsearch_pos(struct bitmap_index *bitmap_git, + struct object_id *oid, + uint32_t *result) +{ + int found; + + if (bitmap_is_midx(bitmap_git)) + found = bsearch_midx(oid, bitmap_git->midx, result); + else + found = bsearch_pack(oid, bitmap_git->pack, result); + + return found; +} + +/* + * `bsearch_triplet_by_pos` function searches for the raw triplet + * having commit position same as `commit_pos` and fills `triplet` + * object from the raw triplet. Returns 1 on success and 0 on + * failure. + */ +static int bsearch_triplet_by_pos(uint32_t commit_pos, + struct bitmap_index *bitmap_git, + struct bitmap_lookup_table_triplet *triplet) +{ + unsigned char *p = bsearch(&commit_pos, bitmap_git->table_lookup, bitmap_git->entry_count, + BITMAP_LOOKUP_TABLE_TRIPLET_WIDTH, triplet_cmp); + + if (!p) + return -1; + + return lookup_table_get_triplet_by_pointer(triplet, p); +} + +static struct stored_bitmap *lazy_bitmap_for_commit(struct bitmap_index *bitmap_git, + struct commit *commit) +{ + uint32_t commit_pos, xor_row; + uint64_t offset; + int flags, found; + struct bitmap_lookup_table_triplet triplet; + struct object_id *oid = &commit->object.oid; + struct ewah_bitmap *bitmap; + struct stored_bitmap *xor_bitmap = NULL; + const int bitmap_header_size = 6; + static struct bitmap_lookup_table_xor_item *xor_items = NULL; + static size_t xor_items_nr = 0, xor_items_alloc = 0; + static int is_corrupt = 0; + + if (is_corrupt) + return NULL; + + found = bsearch_pos(bitmap_git, oid, &commit_pos); + + if (!found) + return NULL; + + if (bsearch_triplet_by_pos(commit_pos, bitmap_git, &triplet) < 0) + return NULL; + + xor_items_nr = 0; + offset = triplet.offset; + xor_row = triplet.xor_row; + + if (xor_row != 0xffffffff) { + int xor_flags; + khiter_t hash_pos; + uint64_t offset_xor; + struct bitmap_lookup_table_xor_item *xor_item; + + while (xor_row != 0xffffffff) { + ALLOC_GROW(xor_items, xor_items_nr + 1, xor_items_alloc); + + if (xor_items_nr + 1 >= bitmap_git->entry_count) { + error(_("corrupt bitmap lookup table: xor chain exceed entry count")); + goto corrupt; + } + + if (lookup_table_get_triplet(bitmap_git, xor_row, &triplet) < 0) + goto corrupt; + + xor_item = &xor_items[xor_items_nr]; + xor_item->offset = triplet.offset; + + if (nth_bitmap_object_oid(bitmap_git, &xor_item->oid, triplet.commit_pos) < 0) { + error(_("corrupt bitmap lookup table: commit index %u out of range"), + triplet.commit_pos); + goto corrupt; + } + + hash_pos = kh_get_oid_map(bitmap_git->bitmaps, xor_item->oid); + + /* + * If desired bitmap is already stored, we don't need + * to iterate further. Because we know that bitmaps + * that are needed to be parsed to parse this bitmap + * has already been stored. So, assign this stored bitmap + * to the xor_bitmap. + */ + if (hash_pos < kh_end(bitmap_git->bitmaps) && + (xor_bitmap = kh_value(bitmap_git->bitmaps, hash_pos))) + break; + xor_items_nr++; + xor_row = triplet.xor_row; + } + + while (xor_items_nr) { + xor_item = &xor_items[xor_items_nr - 1]; + offset_xor = xor_item->offset; + + bitmap_git->map_pos = offset_xor; + if (bitmap_git->map_size - bitmap_git->map_pos < bitmap_header_size) { + error(_("corrupt ewah bitmap: truncated header for bitmap of commit \"%s\""), + oid_to_hex(&xor_item->oid)); + goto corrupt; + } + + bitmap_git->map_pos = bitmap_git->map_pos + sizeof(uint32_t) + sizeof(uint8_t); + xor_flags = read_u8(bitmap_git->map, &bitmap_git->map_pos); + bitmap = read_bitmap_1(bitmap_git); + + if (!bitmap) + goto corrupt; + + xor_bitmap = store_bitmap(bitmap_git, bitmap, &xor_item->oid, xor_bitmap, xor_flags); + xor_items_nr--; + } + } + + bitmap_git->map_pos = offset; + if (bitmap_git->map_size - bitmap_git->map_pos < bitmap_header_size) { + error(_("corrupt ewah bitmap: truncated header for bitmap of commit \"%s\""), + oid_to_hex(oid)); + goto corrupt; + } + + bitmap_git->map_pos = bitmap_git->map_pos + sizeof(uint32_t) + sizeof(uint8_t); + flags = read_u8(bitmap_git->map, &bitmap_git->map_pos); + bitmap = read_bitmap_1(bitmap_git); + + if (!bitmap) + goto corrupt; + + return store_bitmap(bitmap_git, bitmap, oid, xor_bitmap, flags); + +corrupt: + free(xor_items); + is_corrupt = 1; + return NULL; +} + struct ewah_bitmap *bitmap_for_commit(struct bitmap_index *bitmap_git, struct commit *commit) { khiter_t hash_pos = kh_get_oid_map(bitmap_git->bitmaps, commit->object.oid); - if (hash_pos >= kh_end(bitmap_git->bitmaps)) - return NULL; + if (hash_pos >= kh_end(bitmap_git->bitmaps)) { + struct stored_bitmap *bitmap = NULL; + if (!bitmap_git->table_lookup) + return NULL; + + trace2_region_enter("pack-bitmap", "reading_lookup_table", the_repository); + /* NEEDSWORK: cache misses aren't recorded */ + bitmap = lazy_bitmap_for_commit(bitmap_git, commit); + trace2_region_leave("pack-bitmap", "reading_lookup_table", the_repository); + if (!bitmap) + return NULL; + return lookup_stored_bitmap(bitmap); + } return lookup_stored_bitmap(kh_value(bitmap_git->bitmaps, hash_pos)); } @@ -1699,8 +1945,10 @@ void test_bitmap_walk(struct rev_info *revs) if (revs->pending.nr != 1) die("you must specify exactly one commit to test"); - fprintf(stderr, "Bitmap v%d test (%d entries loaded)\n", - bitmap_git->version, bitmap_git->entry_count); + fprintf(stderr, "Bitmap v%d test (%d entries%s)", + bitmap_git->version, + bitmap_git->entry_count, + bitmap_git->table_lookup ? "" : " loaded"); root = revs->pending.objects[0].item; bm = bitmap_for_commit(bitmap_git, (struct commit *)root); @@ -1753,13 +2001,23 @@ void test_bitmap_walk(struct rev_info *revs) int test_bitmap_commits(struct repository *r) { - struct bitmap_index *bitmap_git = prepare_bitmap_git(r); struct object_id oid; MAYBE_UNUSED void *value; + struct bitmap_index *bitmap_git = prepare_bitmap_git(r); + + /* + * As this function is only used to print bitmap selected + * commits, we don't have to read the commit table. + */ if (!bitmap_git) die("failed to load bitmap indexes"); + if (bitmap_git->table_lookup) { + if (load_bitmap_entries_v1(bitmap_git) < 0) + die(_("failed to load bitmap indexes")); + } + kh_foreach(bitmap_git->bitmaps, oid, value, { printf("%s\n", oid_to_hex(&oid)); }); diff --git a/pack-bitmap.h b/pack-bitmap.h index 67a9d0fc303..9278f71ac91 100644 --- a/pack-bitmap.h +++ b/pack-bitmap.h @@ -23,6 +23,15 @@ struct bitmap_disk_header { #define NEEDS_BITMAP (1u<<22) +/* + * The width in bytes of a single triplet in the lookup table + * extension: + * (commit_pos, offset, xor_row) + * + * whose fields ar 32-, 64-, 32- bits wide, respectively. + */ +#define BITMAP_LOOKUP_TABLE_TRIPLET_WIDTH (16) + enum pack_bitmap_opts { BITMAP_OPT_FULL_DAG = 0x1, BITMAP_OPT_HASH_CACHE = 0x4, diff --git a/t/t5310-pack-bitmaps.sh b/t/t5310-pack-bitmaps.sh index c0607172827..7e50f8e7653 100755 --- a/t/t5310-pack-bitmaps.sh +++ b/t/t5310-pack-bitmaps.sh @@ -258,6 +258,7 @@ test_bitmap_cases () { test_expect_success 'truncated bitmap fails gracefully (ewah)' ' test_config pack.writebitmaphashcache false && + test_config pack.writebitmaplookuptable false && git repack -ad && git rev-list --use-bitmap-index --count --all >expect && bitmap=$(ls .git/objects/pack/*.bitmap) && @@ -270,6 +271,7 @@ test_bitmap_cases () { ' test_expect_success 'truncated bitmap fails gracefully (cache)' ' + git config pack.writeBitmapLookupTable '"$writeLookupTable"' && git repack -ad && git rev-list --use-bitmap-index --count --all >expect && bitmap=$(ls .git/objects/pack/*.bitmap) && @@ -453,4 +455,24 @@ test_expect_success 'verify writing bitmap lookup table when enabled' ' grep "\"label\":\"writing_lookup_table\"" trace2 ' +test_expect_success 'lookup table is actually used to traverse objects' ' + git repack -adb && + GIT_TRACE2_EVENT="$(pwd)/trace3" \ + git rev-list --use-bitmap-index --count --all && + grep "\"label\":\"reading_lookup_table\"" trace3 +' + +test_expect_success 'truncated bitmap fails gracefully (lookup table)' ' + test_config pack.writebitmaphashcache false && + git repack -adb && + git rev-list --use-bitmap-index --count --all >expect && + bitmap=$(ls .git/objects/pack/*.bitmap) && + test_when_finished "rm -f $bitmap" && + test_copy_bytes 512 <$bitmap >$bitmap.tmp && + mv -f $bitmap.tmp $bitmap && + git rev-list --use-bitmap-index --count --all >actual 2>stderr && + test_cmp expect actual && + test_i18ngrep corrupted.bitmap.index stderr +' + test_done