A collision test is triggered in sha1_object(), whenever there is an object file in our repo. If our repo is a partial clone, then checking for this file existence does not lazy-fetch the object (if the object is missing and if there are one or more promisor remotes) when fetch_if_missing is set to 0. Though this global lets us control lazy-fetching in regions of code, it prevents multi-threading [1]. Hence, use has_object() to check for the existence of an object, which has the default behavior of not lazy-fetching in a partial clone, even when fetch_if_missing is set to 1. It is worth mentioning that this is the only place where there is potential for lazy-fetching and all other cases [2] are properly handled, making it safe to remove this global here. [1] See https://lore.kernel.org/git/xmqqv9sdeeif.fsf@xxxxxxxxxxxxxxxxxxxxxxxxx/ and the discussion that follows from it. [2] These cases are: - When we check objects, but we return with 0 early if the object doesn't exist. - We prefetch delta bases in a partial clone, if we don't have them (as the comment outlines). - There are some cases where we fsck objects, but lazy-fetching is already handled in fsck. Helped-by: Jonathan Tan <jonathantanmy@xxxxxxxxxx> Signed-off-by: Kousik Sanagavarapu <five231003@xxxxxxxxx> --- Changes since v3: - Changed the commit message to give a stronger reason as to why we should reduce the use of this global and in this process remove it from builtin/index-pack.c - Also made an addition to the test which I overlooked last time and without which the does not make sense builtin/index-pack.c | 11 +---------- t/t5616-partial-clone.sh | 33 +++++++++++++++++++++++++++++++++ 2 files changed, 34 insertions(+), 10 deletions(-) diff --git a/builtin/index-pack.c b/builtin/index-pack.c index 6648f2daef..8c0f36a49e 100644 --- a/builtin/index-pack.c +++ b/builtin/index-pack.c @@ -800,8 +800,7 @@ static void sha1_object(const void *data, struct object_entry *obj_entry, if (startup_info->have_repository) { read_lock(); - collision_test_needed = - has_object_file_with_flags(oid, OBJECT_INFO_QUICK); + collision_test_needed = has_object(the_repository, oid, 0); read_unlock(); } @@ -1728,14 +1727,6 @@ int cmd_index_pack(int argc, const char **argv, const char *prefix) int report_end_of_input = 0; int hash_algo = 0; - /* - * index-pack never needs to fetch missing objects except when - * REF_DELTA bases are missing (which are explicitly handled). It only - * accesses the repo to do hash collision checks and to check which - * REF_DELTA bases need to be fetched. - */ - fetch_if_missing = 0; - if (argc == 2 && !strcmp(argv[1], "-h")) usage(index_pack_usage); diff --git a/t/t5616-partial-clone.sh b/t/t5616-partial-clone.sh index f519d2a87a..41fa7130f1 100755 --- a/t/t5616-partial-clone.sh +++ b/t/t5616-partial-clone.sh @@ -644,6 +644,39 @@ test_expect_success 'repack does not loosen promisor objects' ' grep "loosen_unused_packed_objects/loosened:0" trace ' +test_expect_success 'index-pack does not lazy-fetch + when checking for sha1 collsions' ' + rm -rf server client another-remote && + + git init server && + echo "line" >server/file && + git -C server add file && + git -C server commit -am "file" && + git -C server config --local uploadpack.allowFilter 1 && + git -C server config --local uploadpack.allowAnySha1InWant 1 && + + git clone --no-checkout --filter=blob:none \ + "file://$(pwd)/server" client && + git -C client config extensions.partialClone 1 && + git -C client config remote.origin.promisor 1 && + + git clone "file://$(pwd)/server" another-remote && + + echo "new line" >server/new-file && + git -C server add new-file && + git -C server commit -am "new-file" && + HASH=$(git -C server hash-object new-file) && + + git -C another-remote pull && + + # Try to fetch so that "client" will have to do a collision-check. + # This should, however, not fetch "new-file" because "client" is a + # partial clone. + GIT_TRACE_PACKET=git -C client fetch \ + "file://$(pwd)/another-remote" main && + ! grep "want $HASH" trace +' + test_expect_success 'lazy-fetch in submodule succeeds' ' # setup test_config_global protocol.file.allow always && -- 2.25.1
