Re: mmap with MAP_PRIVATE is useless

From: Paolo Bonzini <bonzini@gnu.org>
Date: Feb 14, 2010, 02:11 UTC
Message-ID: <4B775BD2.3040007@gnu.org>
In-Reply-To: <7vy6iw4m6r.fsf@alter.siamese.dyndns.org>

On 02/14/2010 02:53 AM, Junio C Hamano wrote:

Show 5 quoted lines

> Back when most of these mmap calls were written by Linus and myself,
> we weren't interested in using MAP_PRIVATE, or any other trick for
> that matter, to deal with the case where the user tells git to go
> index a file, and then mucks with the file before git finishes and
> gives back control.

Eh, this one in particular (in index_fd) is quite ancient...

commit e83c5163316f89bfbde7d9ab23ca2e25604af290
Author: Linus Torvalds <torvalds@ppc970.osdl.org>
Date:   Thu Apr 7 15:13:13 2005 -0700

     Initial revision of "git", the information manager from hell

:-)

There were three mmap calls -- in read_sha1_file, read_cache and index_fd -- and all three were of the same mmap (NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0) shape.

Paolo