Re: [PATCH] Prevent git from rehashing 4GBi files

From: Junio C Hamano <gitster@pobox.com>
Date: May 6, 2022, 16:36 UTC
Message-ID: <xmqqr156obxg.fsf@gitster.g>
In-Reply-To: <f3f883cb-9141-6871-0f3d-3d3293a17f5f@iee.email>

Philip Oakley <philipoakley@iee.email> writes:

Show 12 quoted lines

> This "Munge" above isn't telling the reader 'why'/'what' is going on.
> The comment should in some way highlight that a zero size result is
> special, and that we have the roll over issue when the stored in 32 bits
> - the double duty of racy vs changed in the stat data heuristic.
> Synonyms of 'munge' ?
>
>
>> + */
>> +unsigned int munge_st_size(off_t st_size) {
>> +	unsigned int sd_size = st_size;
>> +
>> +	if(!sd_size && st_size)

Style.

>> +		return 0x80000000;
>> +	else
>> +		return sd_size;
>> +}

This may treat non-zero multiple of 4GiB as "not racy", but has anybody double checked the concern Réne brought up earlier that a 4GiB file that was added and then got rewritten to 2GiB within the same second would suddenly start getting treated as not racy?

The patch (the firnal version of it anyway) needs to be accompanied by a handful of test additions to tickle corner cases like that.

Thanks, all, for working on this.