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[104.178.186.189]) by smtp.gmail.com with ESMTPSA id z6sm10038982ilu.42.2022.01.25.14.41.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Jan 2022 14:41:18 -0800 (PST) Date: Tue, 25 Jan 2022 17:41:17 -0500 From: Taylor Blau To: git@vger.kernel.org Cc: gitster@pobox.com, jonathantanmy@google.com, stolee@gmail.com Subject: [PATCH v4 8/9] midx: read `RIDX` chunk when present Message-ID: <94563cf038722852d801bd0a8e744a569799f354.1643150456.git.me@ttaylorr.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org When a MIDX contains the new `RIDX` chunk, ensure that the reverse index is read from it instead of the on-disk .rev file. Since we need to encode the object order in the MIDX itself for correctness reasons, there is no point in storing the same data again outside of the MIDX. So, this patch stops writing separate .rev files, and reads it out of the MIDX itself. This is possible to do with relatively little new code, since the format of the RIDX chunk is identical to the data in the .rev file. In other words, we can implement this by pointing the `revindex_data` field at the reverse index chunk of the MIDX instead of the .rev file without any other changes. Note that we have two knobs that are adjusted for the new tests: GIT_TEST_MIDX_WRITE_REV and GIT_TEST_MIDX_READ_RIDX. The former controls whether the MIDX .rev is written at all, and the latter controls whether we read the MIDX's RIDX chunk. Both are necessary to ensure that the test added at the beginning of this series continues to work. This is because we always need to write the RIDX chunk in the MIDX in order to change its checksum, but we want to make sure reading the existing .rev file still works (since the RIDX chunk takes precedence by default). Arguably this isn't a very interesting mode to test, because the precedence rules mean that we'll always read the RIDX chunk over the .rev file. But it makes it impossible for a user to induce corruption in their repository by adjusting the test knobs (since if we had an either/or knob they could stop writing the RIDX chunk, allowing them to tweak the MIDX's object order without changing its checksum). Signed-off-by: Taylor Blau --- midx.c | 6 +++++- midx.h | 1 + pack-revindex.c | 17 +++++++++++++++++ t/lib-bitmap.sh | 4 ++-- t/t5326-multi-pack-bitmaps.sh | 6 ++++++ t/t5327-multi-pack-bitmaps-rev.sh | 23 +++++++++++++++++++++++ t/t7700-repack.sh | 4 ---- 7 files changed, 54 insertions(+), 7 deletions(-) create mode 100755 t/t5327-multi-pack-bitmaps-rev.sh diff --git a/midx.c b/midx.c index 0248c4577c..6e6cb0eb04 100644 --- a/midx.c +++ b/midx.c @@ -162,6 +162,9 @@ struct multi_pack_index *load_multi_pack_index(const char *object_dir, int local pair_chunk(cf, MIDX_CHUNKID_LARGEOFFSETS, &m->chunk_large_offsets); + if (git_env_bool("GIT_TEST_MIDX_READ_RIDX", 1)) + pair_chunk(cf, MIDX_CHUNKID_REVINDEX, &m->chunk_revindex); + m->num_objects = ntohl(m->chunk_oid_fanout[255]); CALLOC_ARRAY(m->pack_names, m->num_packs); @@ -1429,7 +1432,8 @@ static int write_midx_internal(const char *object_dir, finalize_hashfile(f, midx_hash, CSUM_FSYNC | CSUM_HASH_IN_STREAM); free_chunkfile(cf); - if (flags & MIDX_WRITE_REV_INDEX) + if (flags & MIDX_WRITE_REV_INDEX && + git_env_bool("GIT_TEST_MIDX_WRITE_REV", 0)) write_midx_reverse_index(midx_name.buf, midx_hash, &ctx); if (flags & MIDX_WRITE_BITMAP) { if (write_midx_bitmap(midx_name.buf, midx_hash, &ctx, diff --git a/midx.h b/midx.h index b7d79a515c..22e8e53288 100644 --- a/midx.h +++ b/midx.h @@ -36,6 +36,7 @@ struct multi_pack_index { const unsigned char *chunk_oid_lookup; const unsigned char *chunk_object_offsets; const unsigned char *chunk_large_offsets; + const unsigned char *chunk_revindex; const char **pack_names; struct packed_git **packs; diff --git a/pack-revindex.c b/pack-revindex.c index bd15ebad03..08dc160167 100644 --- a/pack-revindex.c +++ b/pack-revindex.c @@ -298,9 +298,26 @@ int load_midx_revindex(struct multi_pack_index *m) { struct strbuf revindex_name = STRBUF_INIT; int ret; + if (m->revindex_data) return 0; + if (m->chunk_revindex) { + /* + * If the MIDX `m` has a `RIDX` chunk, then use its contents for + * the reverse index instead of trying to load a separate `.rev` + * file. + * + * Note that we do *not* set `m->revindex_map` here, since we do + * not want to accidentally call munmap() in the middle of the + * MIDX. + */ + trace2_data_string("load_midx_revindex", the_repository, + "source", "midx"); + m->revindex_data = (const uint32_t *)m->chunk_revindex; + return 0; + } + trace2_data_string("load_midx_revindex", the_repository, "source", "rev"); diff --git a/t/lib-bitmap.sh b/t/lib-bitmap.sh index 253895c04e..a95537e759 100644 --- a/t/lib-bitmap.sh +++ b/t/lib-bitmap.sh @@ -290,7 +290,7 @@ test_rev_exists () { } midx_bitmap_core () { - rev_kind="${1:-rev}" + rev_kind="${1:-midx}" setup_bitmap_history @@ -434,7 +434,7 @@ midx_bitmap_core () { } midx_bitmap_partial_tests () { - rev_kind="${1:-rev}" + rev_kind="${1:-midx}" test_expect_success 'setup partial bitmaps' ' test_commit packed && diff --git a/t/t5326-multi-pack-bitmaps.sh b/t/t5326-multi-pack-bitmaps.sh index 100ac90d15..c0924074c4 100755 --- a/t/t5326-multi-pack-bitmaps.sh +++ b/t/t5326-multi-pack-bitmaps.sh @@ -9,6 +9,12 @@ test_description='exercise basic multi-pack bitmap functionality' GIT_TEST_MULTI_PACK_INDEX=0 GIT_TEST_MULTI_PACK_INDEX_WRITE_BITMAP=0 +# This test exercise multi-pack bitmap functionality where the object order is +# stored and read from a special chunk within the MIDX, so use the default +# behavior here. +sane_unset GIT_TEST_MIDX_WRITE_REV +sane_unset GIT_TEST_MIDX_READ_RIDX + midx_bitmap_core bitmap_reuse_tests() { diff --git a/t/t5327-multi-pack-bitmaps-rev.sh b/t/t5327-multi-pack-bitmaps-rev.sh new file mode 100755 index 0000000000..d30ba632c8 --- /dev/null +++ b/t/t5327-multi-pack-bitmaps-rev.sh @@ -0,0 +1,23 @@ +#!/bin/sh + +test_description='exercise basic multi-pack bitmap functionality (.rev files)' + +. ./test-lib.sh +. "${TEST_DIRECTORY}/lib-bitmap.sh" + +# We'll be writing our own midx and bitmaps, so avoid getting confused by the +# automatic ones. +GIT_TEST_MULTI_PACK_INDEX=0 +GIT_TEST_MULTI_PACK_INDEX_WRITE_BITMAP=0 + +# Unlike t5326, this test exercise multi-pack bitmap functionality where the +# object order is stored in a separate .rev file. +GIT_TEST_MIDX_WRITE_REV=1 +GIT_TEST_MIDX_READ_RIDX=0 +export GIT_TEST_MIDX_WRITE_REV +export GIT_TEST_MIDX_READ_RIDX + +midx_bitmap_core rev +midx_bitmap_partial_tests rev + +test_done diff --git a/t/t7700-repack.sh b/t/t7700-repack.sh index e489869dd9..5922fb5bdd 100755 --- a/t/t7700-repack.sh +++ b/t/t7700-repack.sh @@ -312,16 +312,13 @@ test_expect_success 'cleans up MIDX when appropriate' ' checksum=$(midx_checksum $objdir) && test_path_is_file $midx && test_path_is_file $midx-$checksum.bitmap && - test_path_is_file $midx-$checksum.rev && test_commit repack-3 && GIT_TEST_MULTI_PACK_INDEX=0 git repack -Adb --write-midx && test_path_is_file $midx && test_path_is_missing $midx-$checksum.bitmap && - test_path_is_missing $midx-$checksum.rev && test_path_is_file $midx-$(midx_checksum $objdir).bitmap && - test_path_is_file $midx-$(midx_checksum $objdir).rev && test_commit repack-4 && GIT_TEST_MULTI_PACK_INDEX=0 git repack -Adb && @@ -354,7 +351,6 @@ test_expect_success '--write-midx with preferred bitmap tips' ' test_line_count = 1 before && rm -fr $midx-$(midx_checksum $objdir).bitmap && - rm -fr $midx-$(midx_checksum $objdir).rev && rm -fr $midx && # instead of constructing the snapshot ourselves (c.f., the test -- 2.34.1.455.gd6eb6fd089