| Message ID | 2f809499abadd83b81b3d38d0cad9a2fd08b5440.1593174637.git.gitgitgadget@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | More commit-graph/Bloom filter improvements | expand |
On Fri, Jun 26, 2020 at 12:30:29PM +0000, Derrick Stolee via GitGitGadget wrote: > From: Derrick Stolee <dstolee@microsoft.com> > > The get_bloom_filter() method is a bit complicated in some parts where > it does not need to be. In particular, it needs to return a NULL filter > only when compute_if_not_present is zero AND the filter data cannot be > loaded from a commit-graph file. This currently happens by accident > because the commit-graph does not load changed-path Bloom filters from > an existing commit-graph when writing a new one. This will change in a > later patch. > > Also clean up some style issues while we are here. > > Helped-by: René Scharfe <l.s.r@web.de> > Signed-off-by: Derrick Stolee <dstolee@microsoft.com> > --- > bloom.c | 14 ++++++-------- > 1 file changed, 6 insertions(+), 8 deletions(-) > > diff --git a/bloom.c b/bloom.c > index c38d1cff0c..2af5389795 100644 > --- a/bloom.c > +++ b/bloom.c > @@ -186,7 +186,7 @@ struct bloom_filter *get_bloom_filter(struct repository *r, > struct diff_options diffopt; > int max_changes = 512; > > - if (bloom_filters.slab_size == 0) > + if (!bloom_filters.slab_size) > return NULL; > > filter = bloom_filter_slab_at(&bloom_filters, c); > @@ -194,16 +194,14 @@ struct bloom_filter *get_bloom_filter(struct repository *r, > if (!filter->data) { > load_commit_graph_info(r, c); > if (c->graph_pos != COMMIT_NOT_FROM_GRAPH && > - r->objects->commit_graph->chunk_bloom_indexes) { > - if (load_bloom_filter_from_graph(r->objects->commit_graph, filter, c)) > - return filter; > - else > - return NULL; > - } > + r->objects->commit_graph->chunk_bloom_indexes) > + load_bloom_filter_from_graph(r->objects->commit_graph, filter, c); > } > > - if (filter->data || !compute_if_not_present) > + if (filter->data) > return filter; > + if (!compute_if_not_present) > + return NULL; Some callers of get_bloom_filter() invoke it with compute_if_not_present=0, but are not prepared to handle a NULL return value and dereference it right away: write_graph_chunk_bloom_indexes(): struct bloom_filter *filter = get_bloom_filter(ctx->r, *list, 0); cur_pos += filter->len; write_graph_chunk_bloom_data(): struct bloom_filter *filter = get_bloom_filter(ctx->r, *list, 0); display_progress(progress, ++i); hashwrite(f, filter->data, filter->len * sizeof(unsigned char)); I don't know whether this was an issue before, but I didn't really tried. Unfortunately, starting with this patch this causes segmentation faults basically in all real repositories I use for testing. expecting success of 9999.1 'test': for i in $(test_seq 1 513) do >file-$i || return 1 done && git add file-* && git commit -q -m one && git commit-graph write --reachable --changed-paths Segmentation fault not ok 1 - test Program received signal SIGSEGV, Segmentation fault. 0x0000000000515848 in write_graph_chunk_bloom_indexes (f=0x9fe650, ctx=0x9d2000) at commit-graph.c:1101 1101 cur_pos += filter->len; (gdb) print filter $1 = (struct bloom_filter *) 0x0 > repo_diff_setup(r, &diffopt); > diffopt.flags.recursive = 1; > -- > gitgitgadget >
On 6/27/2020 12:33 PM, SZEDER Gábor wrote: > On Fri, Jun 26, 2020 at 12:30:29PM +0000, Derrick Stolee via GitGitGadget wrote: >> From: Derrick Stolee <dstolee@microsoft.com> >> >> The get_bloom_filter() method is a bit complicated in some parts where >> it does not need to be. In particular, it needs to return a NULL filter >> only when compute_if_not_present is zero AND the filter data cannot be >> loaded from a commit-graph file. This currently happens by accident >> because the commit-graph does not load changed-path Bloom filters from >> an existing commit-graph when writing a new one. This will change in a >> later patch. >> >> Also clean up some style issues while we are here. >> >> Helped-by: René Scharfe <l.s.r@web.de> >> Signed-off-by: Derrick Stolee <dstolee@microsoft.com> >> --- >> bloom.c | 14 ++++++-------- >> 1 file changed, 6 insertions(+), 8 deletions(-) >> >> diff --git a/bloom.c b/bloom.c >> index c38d1cff0c..2af5389795 100644 >> --- a/bloom.c >> +++ b/bloom.c >> @@ -186,7 +186,7 @@ struct bloom_filter *get_bloom_filter(struct repository *r, >> struct diff_options diffopt; >> int max_changes = 512; >> >> - if (bloom_filters.slab_size == 0) >> + if (!bloom_filters.slab_size) >> return NULL; >> >> filter = bloom_filter_slab_at(&bloom_filters, c); >> @@ -194,16 +194,14 @@ struct bloom_filter *get_bloom_filter(struct repository *r, >> if (!filter->data) { >> load_commit_graph_info(r, c); >> if (c->graph_pos != COMMIT_NOT_FROM_GRAPH && >> - r->objects->commit_graph->chunk_bloom_indexes) { >> - if (load_bloom_filter_from_graph(r->objects->commit_graph, filter, c)) >> - return filter; >> - else >> - return NULL; >> - } >> + r->objects->commit_graph->chunk_bloom_indexes) >> + load_bloom_filter_from_graph(r->objects->commit_graph, filter, c); >> } >> >> - if (filter->data || !compute_if_not_present) >> + if (filter->data) >> return filter; >> + if (!compute_if_not_present) >> + return NULL; > > Some callers of get_bloom_filter() invoke it with > compute_if_not_present=0, but are not prepared to handle a NULL return > value and dereference it right away: > > write_graph_chunk_bloom_indexes(): > > struct bloom_filter *filter = get_bloom_filter(ctx->r, *list, 0); > cur_pos += filter->len; > > write_graph_chunk_bloom_data(): > > struct bloom_filter *filter = get_bloom_filter(ctx->r, *list, 0); > display_progress(progress, ++i); > hashwrite(f, filter->data, filter->len * sizeof(unsigned char)); In theory, these _should_ be safe, because we already computed the filters in an earlier step, right? We should have generated the filter and populated it in the slab. > I don't know whether this was an issue before, but I didn't really > tried. Unfortunately, starting with this patch this causes > segmentation faults basically in all real repositories I use for > testing. > > expecting success of 9999.1 'test': > for i in $(test_seq 1 513) > do > >file-$i || return 1 > done && > git add file-* && > git commit -q -m one && > > git commit-graph write --reachable --changed-paths > > Segmentation fault > not ok 1 - test However, you are demonstrating a failure that doesn't appear in our test suite. I was able to reproduce it. I can confirm that this patch causes a SIGSEGV when writing the commit-graph in the Git repository, too. So, what is wrong with my earlier assumption? There are two problems. The thing I notice is that an empty filter (no changes with respect to the first parent) will have NULL filter->data, so we are returning NULL instead of a correctly-empty filter (with len zero). But what you are hitting here is the max number of changes limit. That also returns a NULL filter, because we mark the filter as "TOO LARGE" to store. We store that as a zero-length filter. The following fixup corrects the bug and adds a test similar to yours, but with extra care around ensuring the revision walk still works appropriately for that large commit. In the next version, I will include more in the commit message about these side-effect changes, especially around the stats for zero-length filters. The trace2 message will no longer differentiate between zero-length filters and NULL filters. Thanks, -Stolee -- >8 -- From f9867adc5de8a072f41b91fd6cd87edfcc92e05e Mon Sep 17 00:00:00 2001 From: Derrick Stolee <dstolee@microsoft.com> Date: Mon, 29 Jun 2020 08:52:33 -0400 Subject: [PATCH] fixup! bloom: fix logic in get_bloom_filter() Signed-off-by: Derrick Stolee <dstolee@microsoft.com> --- commit-graph.c | 8 ++++++-- revision.c | 7 ------- t/t4216-log-bloom.sh | 24 ++++++++++++++++++++++-- 3 files changed, 28 insertions(+), 11 deletions(-) diff --git a/commit-graph.c b/commit-graph.c index a0766a86f5..6752916c1a 100644 --- a/commit-graph.c +++ b/commit-graph.c @@ -1108,7 +1108,8 @@ static int write_graph_chunk_bloom_indexes(struct hashfile *f, while (list < last) { struct bloom_filter *filter = get_bloom_filter(ctx->r, *list, 0); - cur_pos += filter->len; + size_t len = filter ? filter->len : 0; + cur_pos += len; display_progress(progress, ++i); hashwrite_be32(f, cur_pos); list++; @@ -1154,8 +1155,11 @@ static int write_graph_chunk_bloom_data(struct hashfile *f, while (list < last) { struct bloom_filter *filter = get_bloom_filter(ctx->r, *list, 0); + size_t len = filter ? filter->len : 0; display_progress(progress, ++i); - hashwrite(f, filter->data, filter->len * sizeof(unsigned char)); + + if (len) + hashwrite(f, filter->data, len * sizeof(unsigned char)); list++; } diff --git a/revision.c b/revision.c index b40bc5b51b..b9118001f9 100644 --- a/revision.c +++ b/revision.c @@ -633,7 +633,6 @@ static unsigned int count_bloom_filter_maybe; static unsigned int count_bloom_filter_definitely_not; static unsigned int count_bloom_filter_false_positive; static unsigned int count_bloom_filter_not_present; -static unsigned int count_bloom_filter_length_zero; static void trace2_bloom_filter_statistics_atexit(void) { @@ -641,7 +640,6 @@ static void trace2_bloom_filter_statistics_atexit(void) jw_object_begin(&jw, 0); jw_object_intmax(&jw, "filter_not_present", count_bloom_filter_not_present); - jw_object_intmax(&jw, "zero_length_filter", count_bloom_filter_length_zero); jw_object_intmax(&jw, "maybe", count_bloom_filter_maybe); jw_object_intmax(&jw, "definitely_not", count_bloom_filter_definitely_not); jw_object_intmax(&jw, "false_positive", count_bloom_filter_false_positive); @@ -765,11 +763,6 @@ static int check_maybe_different_in_bloom_filter(struct rev_info *revs, return -1; } - if (!filter->len) { - count_bloom_filter_length_zero++; - return -1; - } - for (j = 0; result && j < revs->bloom_keys_nr; j++) { result = bloom_filter_contains(filter, &revs->bloom_keys[j], diff --git a/t/t4216-log-bloom.sh b/t/t4216-log-bloom.sh index d7dd717347..4892364e74 100755 --- a/t/t4216-log-bloom.sh +++ b/t/t4216-log-bloom.sh @@ -60,7 +60,7 @@ setup () { test_bloom_filters_used () { log_args=$1 - bloom_trace_prefix="statistics:{\"filter_not_present\":0,\"zero_length_filter\":0,\"maybe\"" + bloom_trace_prefix="statistics:{\"filter_not_present\":0,\"maybe\"" setup "$log_args" && grep -q "$bloom_trace_prefix" "$TRASH_DIRECTORY/trace.perf" && test_cmp log_wo_bloom log_w_bloom && @@ -146,7 +146,7 @@ test_expect_success 'setup - add commit-graph to the chain with Bloom filters' ' test_bloom_filters_used_when_some_filters_are_missing () { log_args=$1 - bloom_trace_prefix="statistics:{\"filter_not_present\":3,\"zero_length_filter\":0,\"maybe\":6,\"definitely_not\":8" + bloom_trace_prefix="statistics:{\"filter_not_present\":3,\"maybe\":6,\"definitely_not\":8" setup "$log_args" && grep -q "$bloom_trace_prefix" "$TRASH_DIRECTORY/trace.perf" && test_cmp log_wo_bloom log_w_bloom @@ -171,4 +171,24 @@ test_expect_success 'persist filter settings' ' grep "{\"hash_version\":1,\"num_hashes\":9,\"bits_per_entry\":15}" trace2-auto.txt ' +test_expect_success 'correctly report changes over limit' ' + git init 513changes && + ( + cd 513changes && + for i in $(test_seq 1 513) + do + echo $i >file$i.txt || return 1 + done && + git add . && + git commit -m "files" && + git commit-graph write --reachable --changed-paths && + for i in $(test_seq 1 513) + do + git -c core.commitGraph=false log -- file$i.txt >expect && + git log -- file$i.txt >actual && + test_cmp expect actual || return 1 + done + ) +' + test_done \ No newline at end of file
diff --git a/bloom.c b/bloom.c index c38d1cff0c..2af5389795 100644 --- a/bloom.c +++ b/bloom.c @@ -186,7 +186,7 @@ struct bloom_filter *get_bloom_filter(struct repository *r, struct diff_options diffopt; int max_changes = 512; - if (bloom_filters.slab_size == 0) + if (!bloom_filters.slab_size) return NULL; filter = bloom_filter_slab_at(&bloom_filters, c); @@ -194,16 +194,14 @@ struct bloom_filter *get_bloom_filter(struct repository *r, if (!filter->data) { load_commit_graph_info(r, c); if (c->graph_pos != COMMIT_NOT_FROM_GRAPH && - r->objects->commit_graph->chunk_bloom_indexes) { - if (load_bloom_filter_from_graph(r->objects->commit_graph, filter, c)) - return filter; - else - return NULL; - } + r->objects->commit_graph->chunk_bloom_indexes) + load_bloom_filter_from_graph(r->objects->commit_graph, filter, c); } - if (filter->data || !compute_if_not_present) + if (filter->data) return filter; + if (!compute_if_not_present) + return NULL; repo_diff_setup(r, &diffopt); diffopt.flags.recursive = 1;