From: Johannes Schindelin <johannes.schindelin@xxxxxx> Without this bug fix, t7519's four "status doesn't detect unreported modifications" test cases would fail occasionally (and, oddly enough, *a lot* more frequently on Windows). The reason is that these test cases intentionally use the side effect of `git status` to re-write the index if any updates were detected: they first clean the worktree, run `git status` to update the index as well as show the output to the casual reader, then make the worktree dirty again and expect no changes to reported if running with a mocked fsmonitor hook. The problem with this strategy was that the index was written during said `git status` on the clean worktree for the *wrong* reason: not because the index was marked as changed (it wasn't), but because the recorded mtimes were racy with the index' own mtime. As the mtime granularity on Windows is 100 nanoseconds (see e.g. https://docs.microsoft.com/en-us/windows/desktop/SysInfo/file-times), the mtimes of the files are often enough *not* racy with the index', so that that `git status` call currently does not always update the index (including the fsmonitor extension), causing the test case to fail. The obvious fix: if we change *any* index entry's `CE_FSMONITOR_VALID` flag, we should also mark the index as changed. That will cause the index to be written upon `git status`, *including* an updated fsmonitor extension. Side note: Even though the reader might think that the t7519 issue should be *much* more prevalent on Linux, given that the ext4 filesystem (that seems to be used by every Linux distribution) stores mtimes in nanosecond precision. However, ext4 uses `current_kernel_time()` (see https://unix.stackexchange.com/questions/11599#comment762968_11599; it is *amazingly* hard to find any proper source of information about such ext4 questions) whose accuracy seems to depend on many factors but is safely worse than the 100-nanosecond granularity of NTFS (again, it is *horribly* hard to find anything remotely authoritative about this question). So it seems that the racy index condition that hid the bug fixed by this patch simply is a lot more likely on Linux than on Windows. But not impossible ;-) Signed-off-by: Johannes Schindelin <johannes.schindelin@xxxxxx> --- diff-lib.c | 2 +- fsmonitor.h | 5 +++-- preload-index.c | 2 +- read-cache.c | 4 ++-- 4 files changed, 7 insertions(+), 6 deletions(-) diff --git a/diff-lib.c b/diff-lib.c index a838c219ec..61812f48c2 100644 --- a/diff-lib.c +++ b/diff-lib.c @@ -232,7 +232,7 @@ int run_diff_files(struct rev_info *revs, unsigned int option) if (!changed && !dirty_submodule) { ce_mark_uptodate(ce); - mark_fsmonitor_valid(ce); + mark_fsmonitor_valid(istate, ce); if (!revs->diffopt.flags.find_copies_harder) continue; } diff --git a/fsmonitor.h b/fsmonitor.h index 8489fa3244..739318ab6d 100644 --- a/fsmonitor.h +++ b/fsmonitor.h @@ -49,9 +49,10 @@ void refresh_fsmonitor(struct index_state *istate); * called any time the cache entry has been updated to reflect the * current state of the file on disk. */ -static inline void mark_fsmonitor_valid(struct cache_entry *ce) +static inline void mark_fsmonitor_valid(struct index_state *istate, struct cache_entry *ce) { - if (core_fsmonitor) { + if (core_fsmonitor && !(ce->ce_flags & CE_FSMONITOR_VALID)) { + istate->cache_changed = 1; ce->ce_flags |= CE_FSMONITOR_VALID; trace_printf_key(&trace_fsmonitor, "mark_fsmonitor_clean '%s'", ce->name); } diff --git a/preload-index.c b/preload-index.c index e73600ee78..ed6eaa4738 100644 --- a/preload-index.c +++ b/preload-index.c @@ -78,7 +78,7 @@ static void *preload_thread(void *_data) if (ie_match_stat(index, ce, &st, CE_MATCH_RACY_IS_DIRTY|CE_MATCH_IGNORE_FSMONITOR)) continue; ce_mark_uptodate(ce); - mark_fsmonitor_valid(ce); + mark_fsmonitor_valid(index, ce); } while (--nr > 0); if (p->progress) { struct progress_data *pd = p->progress; diff --git a/read-cache.c b/read-cache.c index d3b43ae3ba..32816763bd 100644 --- a/read-cache.c +++ b/read-cache.c @@ -204,7 +204,7 @@ void fill_stat_cache_info(struct index_state *istate, struct cache_entry *ce, st if (S_ISREG(st->st_mode)) { ce_mark_uptodate(ce); - mark_fsmonitor_valid(ce); + mark_fsmonitor_valid(istate, ce); } } @@ -1432,7 +1432,7 @@ static struct cache_entry *refresh_cache_ent(struct index_state *istate, */ if (!S_ISGITLINK(ce->ce_mode)) { ce_mark_uptodate(ce); - mark_fsmonitor_valid(ce); + mark_fsmonitor_valid(istate, ce); } return ce; } -- gitgitgadget
