Re: [PATCH v5] Verify index file before we opportunistically update it

On Thu, Apr 10, 2014 at 05:40:55PM +0700, Duy Nguyen wrote:

verify_hdr() is a bit expensive because you need to digest the whole
index file (could big as big as 14MB on webkit). Could we get away
without it? I mean, is it enough that we pick the last 20 bytes and
compare it with istate->sha1? If we only need 20 bytes, pread() may be
better than mmap().

The chance of SHA-1 collision is small enough for us to ignore, I
think. And if a client updates the index without updating the trailing
sha-1, the index is broken and we don't have to worry about
overwriting it.

That's true, I will commit version 6 in a bit.