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

[Neeraj Singh <nksingh85@gmail.com>]

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