From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Sixt Subject: Re: [PATCH/RFC v3 7/9] write_entry(): use fstat() instead of lstat() when file is open Date: Wed, 04 Feb 2009 15:01:08 +0100 Message-ID: <49899FA4.2020003@viscovery.net> References: <21073c1f3f6c2c81b26a632f495325f5e7a7de5a.1233751281.git.barvik@broadpark.no> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Cc: git@vger.kernel.org, Junio C Hamano To: Kjetil Barvik X-From: git-owner@vger.kernel.org Wed Feb 04 15:51:42 2009 Return-path: Envelope-to: gcvg-git-2@gmane.org Received: from vger.kernel.org ([209.132.176.167]) by lo.gmane.org with esmtp (Exim 4.50) id 1LUj6C-0008V0-Md for gcvg-git-2@gmane.org; Wed, 04 Feb 2009 15:51:33 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752173AbZBDOt4 (ORCPT ); Wed, 4 Feb 2009 09:49:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752150AbZBDOtz (ORCPT ); Wed, 4 Feb 2009 09:49:55 -0500 Received: from lilzmailso02.liwest.at ([212.33.55.13]:3677 "EHLO lilzmailso02.liwest.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751338AbZBDOtx (ORCPT ); Wed, 4 Feb 2009 09:49:53 -0500 Received: from cm56-163-160.liwest.at ([86.56.163.160] helo=linz.eudaptics.com) by lilzmailso02.liwest.at with esmtpa (Exim 4.69) (envelope-from ) id 1LUj4T-00017B-SH; Wed, 04 Feb 2009 15:49:46 +0100 Received: from [127.0.0.1] (J6T.linz.viscovery [192.168.1.96]) by linz.eudaptics.com (Postfix) with ESMTP id BFCE06D9; Wed, 4 Feb 2009 15:01:08 +0100 (CET) User-Agent: Thunderbird 2.0.0.18 (Windows/20081105) In-Reply-To: <21073c1f3f6c2c81b26a632f495325f5e7a7de5a.1233751281.git.barvik@broadpark.no> X-Spam-Score: -1.4 (-) Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: Kjetil Barvik schrieb: > Currently inside write_entry() we do an lstat(path, &st) call on a > file which have just been opened inside the exact same function. It > should be better to call fstat(fd, &st) on the file while it is open, > and it should be at least as fast as the lstat() method. ... > @@ -145,6 +146,11 @@ static int write_entry(struct cache_entry *ce, char *path, const struct checkout > } > > wrote = write_in_full(fd, new, size); > + /* use fstat() only when path == ce->name */ > + if (state->refresh_cache && !to_tempfile && !state->base_dir_len) { > + fstat(fd, &st); > + fstat_done = 1; > + } > close(fd); I've a bad gut feeling about this: It may not work as expected on Windows because there is this statement in the documentation: "The only guarantee about a file timestamp is that the file time is correctly reflected when the handle that makes the change is closed." (http://msdn.microsoft.com/en-us/library/ms724290(VS.85).aspx) We are operating on a temporary file. It could happen that the fstat() returns the time when the file was created, as opposed to when the write_in_full() was completed successfully. The fstat()ed time ends up in the index, but it can be different from what later lstat() calls report (and the file would be regarded as modified). I have the suspicion that the gain from this patch is minimal. Would you mind playing it safe and drop this patch? -- Hannes