From: Johannes Schindelin <johannes.schindelin@xxxxxx> When a split-index is in effect, the `$GIT_DIR/index` file needs to contain a "link" extension that contains all the information about the split-index, including the information about the shared index. However, in some cases Git needs to suppress writing that "link" extension (i.e. to fall back to writing a full index) even if the in-memory index structure _has_ a `split_index` configured. This is the case e.g. when "too many not shared" index entries exist. In such instances, the current code sets the `base_oid` field of said `split_index` structure to all-zero to indicate that `do_write_index()` should skip writing the "link" extension. This can lead to problems later on, when the in-memory index is still used to perform other operations and eventually wants to write a split-index, detects the presence of the `split_index` and reuses that, too (under the assumption that it has been initialized correctly and still has a non-null `base_oid`). Let's stop zeroing out the `base_oid` to indicate that the "link" extension should not be written. One might be tempted to simply call `discard_split_index()` instead, under the assumption that Git decided to write a non-split index and therefore the the `split_index` structure might no longer be wanted. However, that is not possible because that would release index entries in `split_index->base` that are likely to still be in use. Therefore we cannot do that. The next best thing we _can_ do is to introduce a flag, specifically indicating when the "link" extension should be skipped. So that's what we do here. Signed-off-by: Johannes Schindelin <johannes.schindelin@xxxxxx> --- read-cache.c | 37 ++++++++++++++++++++++-------------- t/t7527-builtin-fsmonitor.sh | 2 +- 2 files changed, 24 insertions(+), 15 deletions(-) diff --git a/read-cache.c b/read-cache.c index b09128b1884..8fcb2d54c05 100644 --- a/read-cache.c +++ b/read-cache.c @@ -2868,6 +2868,12 @@ static int record_ieot(void) return !git_config_get_index_threads(&val) && val != 1; } +enum strip_extensions { + WRITE_ALL_EXTENSIONS = 0, + STRIP_ALL_EXTENSIONS = 1, + STRIP_LINK_EXTENSION_ONLY = 2 +}; + /* * On success, `tempfile` is closed. If it is the temporary file * of a `struct lock_file`, we will therefore effectively perform @@ -2876,7 +2882,7 @@ static int record_ieot(void) * rely on it. */ static int do_write_index(struct index_state *istate, struct tempfile *tempfile, - int strip_extensions, unsigned flags) + enum strip_extensions strip_extensions, unsigned flags) { uint64_t start = getnanotime(); struct hashfile *f; @@ -3045,7 +3051,7 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile, return -1; } - if (!strip_extensions && istate->split_index && + if (strip_extensions == WRITE_ALL_EXTENSIONS && istate->split_index && !is_null_oid(&istate->split_index->base_oid)) { struct strbuf sb = STRBUF_INIT; @@ -3060,7 +3066,7 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile, if (err) return -1; } - if (!strip_extensions && !drop_cache_tree && istate->cache_tree) { + if (strip_extensions != STRIP_ALL_EXTENSIONS && !drop_cache_tree && istate->cache_tree) { struct strbuf sb = STRBUF_INIT; cache_tree_write(&sb, istate->cache_tree); @@ -3070,7 +3076,7 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile, if (err) return -1; } - if (!strip_extensions && istate->resolve_undo) { + if (strip_extensions != STRIP_ALL_EXTENSIONS && istate->resolve_undo) { struct strbuf sb = STRBUF_INIT; resolve_undo_write(&sb, istate->resolve_undo); @@ -3081,7 +3087,7 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile, if (err) return -1; } - if (!strip_extensions && istate->untracked) { + if (strip_extensions != STRIP_ALL_EXTENSIONS && istate->untracked) { struct strbuf sb = STRBUF_INIT; write_untracked_extension(&sb, istate->untracked); @@ -3092,7 +3098,7 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile, if (err) return -1; } - if (!strip_extensions && istate->fsmonitor_last_update) { + if (strip_extensions != STRIP_ALL_EXTENSIONS && istate->fsmonitor_last_update) { struct strbuf sb = STRBUF_INIT; write_fsmonitor_extension(&sb, istate); @@ -3166,8 +3172,14 @@ static int commit_locked_index(struct lock_file *lk) return commit_lock_file(lk); } +/* + * Write the Git index into a `.lock` file + * + * If `strip_link_extension` is non-zero, avoid writing any "link" extension + * (used by the split-index feature). + */ static int do_write_locked_index(struct index_state *istate, struct lock_file *lock, - unsigned flags) + unsigned flags, int strip_link_extension) { int ret; int was_full = istate->sparse_index == INDEX_EXPANDED; @@ -3185,7 +3197,7 @@ static int do_write_locked_index(struct index_state *istate, struct lock_file *l */ trace2_region_enter_printf("index", "do_write_index", the_repository, "%s", get_lock_file_path(lock)); - ret = do_write_index(istate, lock->tempfile, 0, flags); + ret = do_write_index(istate, lock->tempfile, strip_link_extension ? STRIP_LINK_EXTENSION_ONLY : 0, flags); trace2_region_leave_printf("index", "do_write_index", the_repository, "%s", get_lock_file_path(lock)); @@ -3214,7 +3226,7 @@ static int write_split_index(struct index_state *istate, { int ret; prepare_to_write_split_index(istate); - ret = do_write_locked_index(istate, lock, flags); + ret = do_write_locked_index(istate, lock, flags, 0); finish_writing_split_index(istate); return ret; } @@ -3366,9 +3378,7 @@ int write_locked_index(struct index_state *istate, struct lock_file *lock, if ((!si && !test_split_index_env) || alternate_index_output || (istate->cache_changed & ~EXTMASK)) { - if (si) - oidclr(&si->base_oid); - ret = do_write_locked_index(istate, lock, flags); + ret = do_write_locked_index(istate, lock, flags, 1); goto out; } @@ -3394,8 +3404,7 @@ int write_locked_index(struct index_state *istate, struct lock_file *lock, /* Same initial permissions as the main .git/index file */ temp = mks_tempfile_sm(git_path("sharedindex_XXXXXX"), 0, 0666); if (!temp) { - oidclr(&si->base_oid); - ret = do_write_locked_index(istate, lock, flags); + ret = do_write_locked_index(istate, lock, flags, 1); goto out; } ret = write_shared_index(istate, &temp, flags); diff --git a/t/t7527-builtin-fsmonitor.sh b/t/t7527-builtin-fsmonitor.sh index cbafdd69602..9fab9a2ab38 100755 --- a/t/t7527-builtin-fsmonitor.sh +++ b/t/t7527-builtin-fsmonitor.sh @@ -1003,7 +1003,7 @@ test_expect_success !UNICODE_COMPOSITION_SENSITIVE 'Unicode nfc/nfd' ' egrep "^event: nfd/d_${utf8_nfc}/?$" ./unicode.trace ' -test_expect_failure 'split-index and FSMonitor work well together' ' +test_expect_success 'split-index and FSMonitor work well together' ' git init split-index && test_when_finished "git -C \"$PWD/split-index\" \ fsmonitor--daemon stop" && -- gitgitgadget