From: Jeff Hostetler <jeffh...@microsoft.com> Teach git to skip verification of the SHA1-1 checksum at the end of the index file in verify_hdr() which is called from read_index() unless the "force_verify_index_checksum" global variable is set.
Teach fsck to force this verification. The checksum verification is for detecting disk corruption, and for small projects, the time it takes to compute SHA-1 is not that significant, but for gigantic repositories this calculation adds significant time to every command. These effect can be seen using t/perf/p0002-read-cache.sh: ================ BEFORE: $ ./p0002-read-cache.sh 0002.1: read_cache/discard_cache 1000 times 0.66(0.58+0.08) AFTER: $ ./p0002-read-cache.sh 0002.1: read_cache/discard_cache 1000 times 0.30(0.28+0.01) ================ Also, using the t/perf/p0004-read-tree.sh test that I created in a parallel patch series. https://public-inbox.org/git/20170404210847.50860-1-...@jeffhostetler.com/ Signed-off-by: Jeff Hostetler <jeffh...@microsoft.com> --- builtin/fsck.c | 1 + cache.h | 2 ++ read-cache.c | 7 +++++++ t/t1450-fsck.sh | 13 +++++++++++++ 4 files changed, 23 insertions(+) diff --git a/builtin/fsck.c b/builtin/fsck.c index 1a5cacc..5512d06 100644 --- a/builtin/fsck.c +++ b/builtin/fsck.c @@ -771,6 +771,7 @@ int cmd_fsck(int argc, const char **argv, const char *prefix) } if (keep_cache_objects) { + verify_index_checksum = 1; read_cache(); for (i = 0; i < active_nr; i++) { unsigned int mode; diff --git a/cache.h b/cache.h index 80b6372..87f13bf 100644 --- a/cache.h +++ b/cache.h @@ -685,6 +685,8 @@ extern void update_index_if_able(struct index_state *, struct lock_file *); extern int hold_locked_index(struct lock_file *, int); extern void set_alternate_index_output(const char *); +extern int verify_index_checksum; + /* Environment bits from configuration mechanism */ extern int trust_executable_bit; extern int trust_ctime; diff --git a/read-cache.c b/read-cache.c index 9054369..c4205aa 100644 --- a/read-cache.c +++ b/read-cache.c @@ -1371,6 +1371,9 @@ struct ondisk_cache_entry_extended { ondisk_cache_entry_extended_size(ce_namelen(ce)) : \ ondisk_cache_entry_size(ce_namelen(ce))) +/* Allow fsck to force verification of the index checksum. */ +int verify_index_checksum; + static int verify_hdr(struct cache_header *hdr, unsigned long size) { git_SHA_CTX c; @@ -1382,6 +1385,10 @@ static int verify_hdr(struct cache_header *hdr, unsigned long size) hdr_version = ntohl(hdr->hdr_version); if (hdr_version < INDEX_FORMAT_LB || INDEX_FORMAT_UB < hdr_version) return error("bad index version %d", hdr_version); + + if (!verify_index_checksum) + return 0; + git_SHA1_Init(&c); git_SHA1_Update(&c, hdr, size - 20); git_SHA1_Final(sha1, &c); diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh index 33a51c9..fc1acb5 100755 --- a/t/t1450-fsck.sh +++ b/t/t1450-fsck.sh @@ -689,4 +689,17 @@ test_expect_success 'bogus head does not fallback to all heads' ' ! grep $blob out ' +test_expect_success 'detect corrupt index file in fsck' ' + cp .git/index .git/index.backup && + test_when_finished "mv .git/index.backup .git/index" && + echo zzzzzzzz >zzzzzzzz && + test_when_finished "rm zzzzzzzz" && + git add zzzzzzzz && + sed -e "s/zzzzzzzz/yyyyyyyy/" .git/index >.git/index.yyy && + rm .git/index && + mv .git/index.yyy .git/index && + test_when_finished "rm .git/index" && + test_must_fail git fsck --cache +' + test_done -- 2.9.3
