Re: [PATCH v2 3/3] refs: add configuration to enable flushing of refs

On Wed, Nov 10, 2021 at 12:41:03PM +0100, Patrick Steinhardt wrote:

 
+static int sync_loose_ref(int fd)
+{
+	switch (fsync_ref_files) {
+	case FSYNC_REF_FILES_OFF:
+		return 0;
+	case FSYNC_REF_FILES_ON:
+		return git_fsync(fd, FSYNC_HARDWARE_FLUSH);
+	case FSYNC_REF_FILES_BATCH:
+		return git_fsync(fd, FSYNC_WRITEOUT_ONLY);
+	default:
+		BUG("invalid fsync mode %d", fsync_ref_files);
+	}
+}
+
+#define SYNC_LOOSE_REF_GITDIR    (1 << 0)
+#define SYNC_LOOSE_REF_COMMONDIR (1 << 1)
+
+static int sync_loose_refs_flags(const char *refname)
+{
+	switch (ref_type(refname)) {
+	case REF_TYPE_PER_WORKTREE:
+	case REF_TYPE_PSEUDOREF:
+		return SYNC_LOOSE_REF_GITDIR;
+	case REF_TYPE_MAIN_PSEUDOREF:
+	case REF_TYPE_OTHER_PSEUDOREF:
+	case REF_TYPE_NORMAL:
+		return SYNC_LOOSE_REF_COMMONDIR;
+	default:
+		BUG("unknown ref type %d of ref %s",
+		    ref_type(refname), refname);
+	}
+}
+
+static int sync_loose_refs(struct files_ref_store *refs,
+			   int flags,
+			   struct strbuf *err)
+{
+	if (fsync_ref_files != FSYNC_REF_FILES_BATCH)
+		return 0;
+
+	if ((flags & SYNC_LOOSE_REF_GITDIR) &&
+	    git_fsync_dir(refs->base.gitdir) < 0)
+		return -1;
+
+	if ((flags & SYNC_LOOSE_REF_COMMONDIR) &&
+	    git_fsync_dir(refs->gitcommondir) < 0)
+		return -1;
+
+	return 0;
+}
+

Now that I understand it better, I agree with Ævar's feedback. I think
only a single sync is needed to cover everything in .git/. 

I'd also suggest renaming 'sync_loose_refs' to something which makes
it clearer that it's the batch-flush step. Maybe s/do_batch_fsync/do_batch_objects_fsync
and s/sync_loose_refs/do_batch_refs_fsync.

Thanks
Neeraj