Re: [PATCH 1/2] Use git_open_noatime when accessing pack data

From: Jonathan Nieder <jrnieder@gmail.com>
Date: Nov 3, 2010, 17:41 UTC
Message-ID: <20101103174148.GB13377@burratino>
In-Reply-To: <7v8w1axrnp.fsf@alter.siamese.dyndns.org>

Junio C Hamano wrote:

>  (1) introduce "int git_open_ro(const char *)" to replace the current
>      git_open_noatime().  The point is that the function no longer is
>      about avoiding from smudging the inode metadata.  Instead, it becomes
>      the preferred way for us to get a read-only fd.

[...]

> We can of course do without s/git_open_noatime/git_open_ro/; and it will
> make the patch much smaller.  The rename is purely a clarification of the
> API and is optional.  It may make it easier to explain the name of the new
> function, though.

Probably a silly question, but should all readonly open()s actually use noatime? Some uses for atime:

 - tmpwatch.  That one's a bit insane, anyway, but I think it might
   work because loose objects and packs are read-only.

 - mail clients.  For this case, noatime is the right thing to do ---
   git's access does mean the mail was read.

 - listing important files, as in popularity-contest.  For this,
   noatime is also the right thing to do.

Judging from these three use cases, readonly open()s to the worktree should indeed use noatime, but open()s of .git/config, say, should not. Hmm.