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[104.178.186.189]) by smtp.gmail.com with UTF8SMTPSA id 00721157ae682-70f8acd8bffsm281907b3.77.2025.05.28.15.58.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 May 2025 15:58:58 -0700 (PDT) Date: Wed, 28 May 2025 18:58:57 -0400 From: Taylor Blau To: git@vger.kernel.org Cc: Patrick Steinhardt , Jeff King , Junio C Hamano Subject: [PATCH v2 0/4] midx: improve prepare_midx_pack() ergonomics Message-ID: References: Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: This series has been updated to be based on v3 of ps/midx-negative-packfile-cache, which is 1f34bf3e08 (midx: stop repeatedly looking up nonexistent packfiles, 2025-05-28) at the time of writing. There are a couple of minor changes from last time, including: - using the new MIDX_PACK_ERROR macro instead of casting '-1' to a void pointer - converting some direct m->pack_names lookups (outside of midx.c and midx-write.c with one exception) to use a similar pattern to access the nth pack name As usual, a range-diff against v1 is below for convenience. Thanks again for your review! Taylor Blau (4): midx: access pack names through `nth_midxed_pack_name()` midx-write.c: guard against incremental MIDXs in want_included_pack() midx-write.c: extract inner loop from fill_packs_from_midx() midx: return a `packed_git` pointer from `prepare_midx_pack()` midx-write.c | 101 +++++++++++++++++++++----------------- midx.c | 88 +++++++++++++++++---------------- midx.h | 6 ++- pack-bitmap.c | 6 +-- t/helper/test-read-midx.c | 7 +-- 5 files changed, 116 insertions(+), 92 deletions(-) Range-diff against v1: 1: a7082dc7f0 < -: ---------- packfile: explain ordering of how we look up auxiliary pack files 2: 73fe0882ee < -: ---------- midx: stop repeatedly looking up nonexistent packfiles 3: ad7295b11b < -: ---------- pack-bitmap.c: fix broken warning() when missing MIDX'd pack 5: 5d97b706e1 ! 1: d3508d3cfb midx-write.c: simplify fill_packs_from_midx() @@ Metadata Author: Taylor Blau ## Commit message ## - midx-write.c: simplify fill_packs_from_midx() + midx: access pack names through `nth_midxed_pack_name()` - When enumerating packs within fill_packs_from_midx(), we open the pack's - index iff we are either writing a reverse index, have a preferred pack - (by name) or both. + Accessing a MIDX's 'pack_names' array is somewhat error-prone when + dealing with incremental MIDX chains, where the (global) pack_int_id for + some pack may differ from the containing layer's index for that pack. - Let's simplify this into a single case by setting the - MIDX_WRITE_REV_INDEX flag bit when we have a preferred_pack_name. This - is a little bit of a shortcut to reduce the line length in the loop - below. But it sets us up nicely to extract the inner loop of this - function out into its own function, where we will no longer have to pass - the preferred_pack_name. + Introduce `nth_midxed_pack_name()` in an effort to reduce a common + source of errors by discouraging external callers from accessing a + layer's `pack_names` array directly. Signed-off-by: Taylor Blau - ## midx-write.c ## -@@ midx-write.c: static int fill_packs_from_midx(struct write_midx_context *ctx, - { - struct multi_pack_index *m; + ## midx.c ## +@@ midx.c: struct packed_git *nth_midxed_pack(struct multi_pack_index *m, + return m->packs[local_pack_int_id]; + } -+ if (preferred_pack_name) { -+ /* -+ * If a preferred pack is specified, need to have -+ * packed_git's loaded to ensure the chosen preferred -+ * pack has a non-zero object count. -+ * -+ * Trick ourselves into thinking that we're writing a -+ * reverse index in this case in order to open up the -+ * pack index file. -+ */ -+ flags |= MIDX_WRITE_REV_INDEX; -+ } ++const char *nth_midxed_pack_name(struct multi_pack_index *m, ++ uint32_t pack_int_id) ++{ ++ uint32_t local_pack_int_id = midx_for_pack(&m, pack_int_id); ++ return m->pack_names[local_pack_int_id]; ++} + - for (m = ctx->m; m; m = m->base_midx) { - uint32_t i; + #define MIDX_CHUNK_BITMAPPED_PACKS_WIDTH (2 * sizeof(uint32_t)) -@@ midx-write.c: static int fill_packs_from_midx(struct write_midx_context *ctx, - * If generating a reverse index, need to have - * packed_git's loaded to compare their - * mtimes and object count. -- * -- * If a preferred pack is specified, need to -- * have packed_git's loaded to ensure the chosen -- * preferred pack has a non-zero object count. - */ -- if (flags & MIDX_WRITE_REV_INDEX || -- preferred_pack_name) { -+ if (flags & MIDX_WRITE_REV_INDEX) { - if (prepare_midx_pack(ctx->repo, m, - m->num_packs_in_base + i)) { - error(_("could not load pack")); + int nth_bitmapped_pack(struct repository *r, struct multi_pack_index *m, + + ## midx.h ## +@@ midx.h: struct multi_pack_index *load_multi_pack_index(struct repository *r, + int prepare_midx_pack(struct repository *r, struct multi_pack_index *m, uint32_t pack_int_id); + struct packed_git *nth_midxed_pack(struct multi_pack_index *m, + uint32_t pack_int_id); ++const char *nth_midxed_pack_name(struct multi_pack_index *m, ++ uint32_t pack_int_id); + int nth_bitmapped_pack(struct repository *r, struct multi_pack_index *m, + struct bitmapped_pack *bp, uint32_t pack_int_id); + int bsearch_one_midx(const struct object_id *oid, struct multi_pack_index *m, + + ## pack-bitmap.c ## +@@ pack-bitmap.c: static int open_midx_bitmap_1(struct bitmap_index *bitmap_git, + for (i = 0; i < bitmap_git->midx->num_packs + bitmap_git->midx->num_packs_in_base; i++) { + if (prepare_midx_pack(bitmap_repo(bitmap_git), bitmap_git->midx, i)) { + warning(_("could not open pack %s"), +- bitmap_git->midx->pack_names[i]); ++ nth_midxed_pack_name(bitmap_git->midx, i)); + goto cleanup; + } + } +@@ pack-bitmap.c: void reuse_partial_packfile_from_bitmap(struct bitmap_index *bitmap_git, + struct bitmapped_pack pack; + if (nth_bitmapped_pack(r, bitmap_git->midx, &pack, i) < 0) { + warning(_("unable to load pack: '%s', disabling pack-reuse"), +- bitmap_git->midx->pack_names[i]); ++ nth_midxed_pack_name(bitmap_git->midx, i)); + free(packs); + return; + } + + ## t/helper/test-read-midx.c ## +@@ t/helper/test-read-midx.c: static int read_midx_file(const char *object_dir, const char *checksum, + printf("\nnum_objects: %d\n", m->num_objects); + + printf("packs:\n"); +- for (i = 0; i < m->num_packs; i++) +- printf("%s\n", m->pack_names[i]); ++ for (i = m->num_packs_in_base; i < m->num_packs + m->num_packs_in_base; ++ i++) ++ printf("%s\n", nth_midxed_pack_name(m, i)); + + printf("object-dir: %s\n", m->object_dir); + +@@ t/helper/test-read-midx.c: static int read_midx_preferred_pack(const char *object_dir) + return 1; + } + +- printf("%s\n", midx->pack_names[preferred_pack]); ++ printf("%s\n", nth_midxed_pack_name(midx, preferred_pack)); + close_midx(midx); + return 0; + } 4: d2f9645aa1 ! 2: cf3ab81a08 midx-write.c: guard against incremental MIDXs in want_included_pack() @@ Commit message if (m->base_midx) die(_("cannot repack an incremental multi-pack-index")); - So want_included_pack() is OK becuase it will never encounter a + So want_included_pack() is OK because it will never encounter a situation where it has to chase backwards through the '->base_midx' pointer. But that is not immediately clear from reading the code, and is too fragile for my comfort. Make this more clear by adding an ASSERT() 6: a4080c12df ! 3: e54988bfea midx-write.c: extract inner loop from fill_packs_from_midx() @@ midx-write.c: static struct multi_pack_index *lookup_multi_pack_index(struct rep +static int fill_packs_from_midx_1(struct write_midx_context *ctx, + struct multi_pack_index *m, -+ uint32_t flags) ++ int prepare_packs) +{ + for (uint32_t i = 0; i < m->num_packs; i++) { -+ ALLOC_GROW(ctx->info, ctx->nr + 1, ctx->alloc); -+ + /* + * If generating a reverse index, need to have + * packed_git's loaded to compare their + * mtimes and object count. + */ -+ if (flags & MIDX_WRITE_REV_INDEX) { ++ if (prepare_packs) { + if (prepare_midx_pack(ctx->repo, m, + m->num_packs_in_base + i)) { + error(_("could not load pack")); @@ midx-write.c: static struct multi_pack_index *lookup_multi_pack_index(struct rep static int fill_packs_from_midx(struct write_midx_context *ctx, const char *preferred_pack_name, uint32_t flags) { -@@ midx-write.c: static int fill_packs_from_midx(struct write_midx_context *ctx, - } + struct multi_pack_index *m; ++ int prepare_packs; ++ ++ /* ++ * If generating a reverse index, need to have packed_git's ++ * loaded to compare their mtimes and object count. ++ */ ++ prepare_packs = !!(flags & MIDX_WRITE_REV_INDEX || preferred_pack_name); for (m = ctx->m; m; m = m->base_midx) { - uint32_t i; @@ midx-write.c: static int fill_packs_from_midx(struct write_midx_context *ctx, - * If generating a reverse index, need to have - * packed_git's loaded to compare their - * mtimes and object count. +- * +- * If a preferred pack is specified, need to +- * have packed_git's loaded to ensure the chosen +- * preferred pack has a non-zero object count. - */ -- if (flags & MIDX_WRITE_REV_INDEX) { +- if (flags & MIDX_WRITE_REV_INDEX || +- preferred_pack_name) { - if (prepare_midx_pack(ctx->repo, m, - m->num_packs_in_base + i)) { - error(_("could not load pack")); @@ midx-write.c: static int fill_packs_from_midx(struct write_midx_context *ctx, - m->pack_names[i], - m->num_packs_in_base + i); - } -+ int ret = fill_packs_from_midx_1(ctx, m, flags); ++ int ret = fill_packs_from_midx_1(ctx, m, prepare_packs); + if (ret) + return ret; } 7: 80699bb3ee ! 4: e3e21db673 midx: return a `packed_git` pointer from `prepare_midx_pack()` @@ Commit message ## midx-write.c ## @@ midx-write.c: static int fill_packs_from_midx_1(struct write_midx_context *ctx, - uint32_t flags) + int prepare_packs) { for (uint32_t i = 0; i < m->num_packs; i++) { +- /* +- * If generating a reverse index, need to have +- * packed_git's loaded to compare their +- * mtimes and object count. +- */ + struct packed_git *p = NULL; + - ALLOC_GROW(ctx->info, ctx->nr + 1, ctx->alloc); - - /* -@@ midx-write.c: static int fill_packs_from_midx_1(struct write_midx_context *ctx, - * mtimes and object count. - */ - if (flags & MIDX_WRITE_REV_INDEX) { ++ ALLOC_GROW(ctx->info, ctx->nr + 1, ctx->alloc); + if (prepare_packs) { - if (prepare_midx_pack(ctx->repo, m, - m->num_packs_in_base + i)) { + p = prepare_midx_pack(ctx->repo, m, @@ midx-write.c: static int fill_packs_from_midx_1(struct write_midx_context *ctx, } - fill_pack_info(&ctx->info[ctx->nr++], m->packs[i], -+ fill_pack_info(&ctx->info[ctx->nr++], p, - m->pack_names[i], +- m->pack_names[i], ++ fill_pack_info(&ctx->info[ctx->nr++], p, m->pack_names[i], m->num_packs_in_base + i); } + @@ midx-write.c: int expire_midx_packs(struct repository *r, const char *object_dir, unsigned fla _("Finding and deleting unreferenced packfiles"), m->num_packs); @@ midx.c: static uint32_t midx_for_pack(struct multi_pack_index **_m, + struct strbuf key = STRBUF_INIT; + struct packed_git *p; -- if (m->packs[pack_int_id] == (void *)(intptr_t)-1) +- if (m->packs[pack_int_id] == MIDX_PACK_ERROR) - return 1; - if (m->packs[pack_int_id]) - return 0; @@ midx.c: static uint32_t midx_for_pack(struct multi_pack_index **_m, + strbuf_release(&key); - if (!p) { -- m->packs[pack_int_id] = (void *)(intptr_t)-1; +- m->packs[pack_int_id] = MIDX_PACK_ERROR; - return 1; -+ m->packs[pack_pos] = p ? p : (void *)(intptr_t)-1; ++ m->packs[pack_pos] = p ? p : MIDX_PACK_ERROR; + if (p) + p->multi_pack_index = 1; } @@ midx.c: static uint32_t midx_for_pack(struct multi_pack_index **_m, - m->packs[pack_int_id] = p; - - return 0; -+ if (m->packs[pack_pos] == (void *)(intptr_t)-1) ++ if (m->packs[pack_pos] == MIDX_PACK_ERROR) + return NULL; + return m->packs[pack_pos]; } @@ midx.h: void get_split_midx_filename_ext(const struct git_hash_algo *hash_algo, + uint32_t pack_int_id); struct packed_git *nth_midxed_pack(struct multi_pack_index *m, uint32_t pack_int_id); - int nth_bitmapped_pack(struct repository *r, struct multi_pack_index *m, + const char *nth_midxed_pack_name(struct multi_pack_index *m, ## pack-bitmap.c ## @@ pack-bitmap.c: static int open_midx_bitmap_1(struct bitmap_index *bitmap_git, @@ pack-bitmap.c: static int open_midx_bitmap_1(struct bitmap_index *bitmap_git, - if (prepare_midx_pack(bitmap_repo(bitmap_git), bitmap_git->midx, i)) { + if (!prepare_midx_pack(bitmap_repo(bitmap_git), bitmap_git->midx, i)) { warning(_("could not open pack %s"), - bitmap_git->midx->pack_names[i - bitmap_git->midx->num_packs_in_base]); + nth_midxed_pack_name(bitmap_git->midx, i)); goto cleanup; base-commit: 1f34bf3e082741e053d25b76a0ffe31d9d967594 -- 2.49.0.640.ga4de40e6a8