diff options
| author | Patrick Steinhardt <ps@pks.im> | 2022-12-20 17:52:14 +0300 |
|---|---|---|
| committer | Junio C Hamano <gitster@pobox.com> | 2022-12-25 10:18:12 +0300 |
| commit | ce54672f9b017adf60d15bc7174994b63cb29d3a (patch) | |
| tree | 65ac94dd610b018f931909c34f33424b4e57b3e1 /refs | |
| parent | bc22d845c4328f5bd896d019b3729f776ad4be4c (diff) | |
refs: fix corruption by not correctly syncing packed-refs to disk
At GitLab we have recently received a report where a repository was left
with a corrupted `packed-refs` file after the node hard-crashed even
though `core.fsync=reference` was set. This is something that in theory
should not happen if we correctly did the atomic-rename dance to:
1. Write the data into a temporary file.
2. Synchronize the temporary file to disk.
3. Rename the temporary file into place.
So if we crash in the middle of writing the `packed-refs` file we should
only ever see either the old or the new state of the file.
And while we do the dance when writing the `packed-refs` file, there is
indeed one gotcha: we use a `FILE *` stream to write the temporary file,
but don't flush it before synchronizing it to disk. As a consequence any
data that is still buffered will not get synchronized and a crash of the
machine may cause corruption.
Fix this bug by flushing the file stream before we fsync.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'refs')
| -rw-r--r-- | refs/packed-backend.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/refs/packed-backend.c b/refs/packed-backend.c index 9d704ccd3e..62b5644596 100644 --- a/refs/packed-backend.c +++ b/refs/packed-backend.c @@ -1262,7 +1262,8 @@ static int write_with_updates(struct packed_ref_store *refs, goto error; } - if (fsync_component(FSYNC_COMPONENT_REFERENCE, get_tempfile_fd(refs->tempfile)) || + if (fflush(out) || + fsync_component(FSYNC_COMPONENT_REFERENCE, get_tempfile_fd(refs->tempfile)) || close_tempfile_gently(refs->tempfile)) { strbuf_addf(err, "error closing file %s: %s", get_tempfile_path(refs->tempfile), |