On Tue, Aug 11, 2020 at 11:18:30PM +0200, SZEDER Gábor wrote: > On Tue, Aug 11, 2020 at 04:51:19PM -0400, Taylor Blau wrote: > > Many places in the code often need a pointer to the commit-graph's > > 'struct bloom_filter_settings', in which case they often take the value > > from the top-most commit-graph. > > > > In the non-split case, this works as expected. In the split case, > > however, things get a little tricky. Not all layers in a chain of > > incremental commit-graphs are required to themselves have Bloom data, > > and so whether or not some part of the code uses Bloom filters depends > > entirely on whether or not the top-most level of the commit-graph chain > > has Bloom filters. > > > > This has been the behavior since Bloom filters were introduced, and has > > been codified into the tests since a759bfa9ee (t4216: add end to end > > tests for git log with Bloom filters, 2020-04-06). In fact, t4216.130 > > requires that Bloom filters are not used in exactly the case described > > earlier. > > > > There is no reason that this needs to be the case, since it is perfectly > > valid for commits in an earlier layer to have Bloom filters when commits > > in a newer layer do not. > > > > Since Bloom settings are guaranteed to be the same for any layer in a > > chain that has Bloom data, > > Is it? Where is that guaranteed? There is no mechanism whatsoever to customize these settings that is exposed to the user (except for the undocumented 'GIT_TEST' environment variables). > > it is sufficient to traverse the > > '->base_graph' pointer until either (1) a non-null 'struct > > bloom_filter_settings *' is found, or (2) until we are at the root of > > the commit-graph chain. > > > > Introduce a 'get_bloom_filter_settings()' function that does just this, > > and use it instead of purely dereferencing the top-most graph's > > '->bloom_filter_settings' pointer. > > > > While we're at it, add an additional test in t5324 to guard against code > > in the commit-graph writing machinery that doesn't correctly handle a > > NULL 'struct bloom_filter *'. > > > > Co-authored-by: Derrick Stolee <dstolee@xxxxxxxxxxxxx> > > Signed-off-by: Taylor Blau <me@xxxxxxxxxxxx> Thanks, Taylor
