Re: [PATCH v12 13/13] fsmonitor: fix split-index bitmap bounds in tweak_fsmonitor()

> Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
> 
> > So the actual bug fix would be to ensure that `write_shared_index()`
> > produces a hash even if `index.skipHash=true`, because that hash is
> > needed to identify the shared index.
> 
> You're right, and I verified this. I reverted my fsmonitor.c patch
> from seen, applied the fix below in write_shared_index(), and ran
> t9210 with GIT_TEST_SPLIT_INDEX=yes on Fedora:
> 
>   Without either fix:     not ok 12, not ok 13 (BUG assertion)
>   With only skipHash fix: passed all 22 test(s)
> 
> The fsmonitor.c patch is not needed. I'll drop it from the next
> version of the series.

> Happy to submit this as a separate patch or include it in my
> series if that's helpful. Or if someone is already working on the
> skipHash + split-index interaction, I'll stay out of the way.
> 
> --- >8 ---
> 
> diff --git a/read-cache.c b/read-cache.c
> --- a/read-cache.c
> +++ b/read-cache.c
> @@ write_shared_index
>  	move_cache_to_base_index(istate);
>  	convert_to_sparse(istate, 0);
> 
> -	trace2_region_enter_printf("index", "shared/do_write_index",
> -				   the_repository, "%s", get_tempfile_path(*temp));
> -	ret = do_write_index(si->base, *temp, WRITE_NO_EXTENSION, flags);
> -	trace2_region_leave_printf("index", "shared/do_write_index",
> -				   the_repository, "%s", get_tempfile_path(*temp));
> +	/*
> +	 * The shared index is identified by the hash of its contents
> +	 * (sharedindex.<oid>).  If index.skipHash is set, do_write_index()
> +	 * would produce an all-zero hash and the shared index would not
> +	 * be found on re-read (is_null_oid() check in read_index_from()).
> +	 * Temporarily force hashing for the shared index write.
> +	 */
> +	{
> +		struct repository *r = the_repository;
> +		int save_skip_hash;
> +
> +		prepare_repo_settings(r);
> +		save_skip_hash = r->settings.index_skip_hash;
> +		r->settings.index_skip_hash = 0;
> +
> +		trace2_region_enter_printf("index", "shared/do_write_index",
> +					   the_repository, "%s", get_tempfile_path(*temp));
> +		ret = do_write_index(si->base, *temp, WRITE_NO_EXTENSION, flags);
> +		trace2_region_leave_printf("index", "shared/do_write_index",
> +					   the_repository, "%s", get_tempfile_path(*temp));
> +
> +		r->settings.index_skip_hash = save_skip_hash;
> +	}
> 
>  	if (was_full)
>  		ensure_full_index(istate);