From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 22199 invoked by alias); 22 Apr 2014 08:16:32 -0000 Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Received: (qmail 22186 invoked by uid 89); 22 Apr 2014 08:16:32 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-4.9 required=5.0 tests=AWL,BAYES_00,UNSUBSCRIBE_BODY autolearn=no version=3.3.2 X-HELO: calimero.vinschen.de Received: from aquarius.hirmke.de (HELO calimero.vinschen.de) (217.91.18.234) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Tue, 22 Apr 2014 08:16:31 +0000 Received: by calimero.vinschen.de (Postfix, from userid 500) id DBBE68E142F; Tue, 22 Apr 2014 10:16:28 +0200 (CEST) Date: Tue, 22 Apr 2014 08:16:00 -0000 From: Corinna Vinschen To: cygwin@cygwin.com Subject: Re: fstat st_size on open files on Parallels filesystem is wrong Message-ID: <20140422081628.GC2339@calimero.vinschen.de> Reply-To: cygwin@cygwin.com Mail-Followup-To: cygwin@cygwin.com References: <21333.25325.11106.958642@compute01.cs.columbia.edu> <227151856.20140421223417@yandex.ru> <21333.26515.393838.380071@compute01.cs.columbia.edu> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="Md/poaVZ8hnGTzuv" Content-Disposition: inline In-Reply-To: <21333.26515.393838.380071@compute01.cs.columbia.edu> User-Agent: Mutt/1.5.21 (2010-09-15) X-SW-Source: 2014-04/txt/msg00499.txt.bz2 --Md/poaVZ8hnGTzuv Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Content-length: 2503 On Apr 21 14:46, lennox@cs.columbia.edu wrote: > On Monday, April 21 2014, "Andrey Repin" wrote to "lennox at > cs.columbia.edu, cygwin at cygwin.com" saying: >=20 > > Greetings, lennox at cs.columbia.edu! > >=20 > > > I=E2=80=99m running cygwin64 1.7.29 in a Windows 8.1 Pro virtual mach= ine, running in > > > Parallels Desktop 9.0.24229 on Mac OS X 10.9.2. > >=20 > > > Parallels Desktop automatically mounts my Mac OS X home directory as = a Z: > > > drive in Windows. Cygwin mount reports this drive as being type "prl= sf". > >=20 > > > Unfortunately, I've discovered that if I have an open file on this > > > filesystem which has been written to, the size returned by Cygwin fst= at() on > > > the open file is wrong. A stat() of the file after it's been closed = is > > > correct. > >=20 > > > This has the consequence that emacs always thinks saved files have be= en > > > modified externally, since emacs looks at files' sizes (as well as th= eir > > > modification times) to detect external changes. This makes emacs > > > near-unusable. > >=20 > > > This problem does not occur for files in my Cygwin home directory, or= other > > > locations mounted on my Windows C: drive. > >=20 > > > I've attached a simple unit test program that illustrates the problem. > > > I've also attached my cygcheck -s -v -r output. > >=20 > > > Any ideas? Is this a Cygwin bug, a Parallels bug, or something else? > > > Glancing over the Cygwin code, I see that there are a few cases where= fstat > > > has special cases for certain filesystem types. > >=20 > > You never flushing the buffer in your test code, or I'm reading it wron= g? >=20 > This is using Posix APIs -- open() / write() -- not C APIs, fopen() / > fwrite(), so there shouldn't be a buffer? Notice that the test behaves a= s I > expect for a file on NTFS. >=20 > Adding a call to fsync() prior to the fstat() call doesn't change anythin= g. This is actually a bad sign. The problem you're describing occurs on NFS, too. If you write to the file, a subsequent call to fetch stat attributes does not return the actual size of the file, but the size at the time the handle has been opened. However, on NFS, a call to FlushFileBuffers helps to kick stat back into shape. That's the Win32 function called from fsync as well. What is Cygwin supposed to do if that doesn't work? Corinna --=20 Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Maintainer cygwin AT cygwin DOT com Red Hat --Md/poaVZ8hnGTzuv Content-Type: application/pgp-signature Content-length: 819 -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJTViVcAAoJEPU2Bp2uRE+gTSwP/1mPxk86586sUW9y4lTjkyGy 9TPNJL5cvL5dXNriFxhHAV9aERuyUjCTqH1LZ9k56CWm3qxy6Fk4ByDW7/bbA1vf s//rxW/9wYkj49+lNDNRUL0fx0dsyLRsw4glHq1X6TpjxILtn40O6DtSGPhaDU9l PmYkdFaruaI4n7iaGC054+UnLIvELlEH0dIhQBihpk4pSRxzHEg7wzg0vxhoZORQ LB0snI17FlcE9ixPlpksVMIm3wEhFsUFNSbqxeIfosSO+6u9tgHl5UeXraKLMQV3 Ko78fLBYt8NI9/yHpfr0f25gme0jFJVEFWq/InIKxCmQ2cSbpdxBqmbrmYkJ4P90 pNRPwCVxJuGO9gFzL/raH9bLF1OCl2XkUa3kAKM1kRL8T7dFltUuv150K4cQWhWk a93uN5BefdrHKXkfJrgTJM62aZRHZTwCnf3xfKZxDxzibwcs+4rjisbdHDf9bVt0 alKt+gmwASxqsMOlk1iUm0Xrmgj1XrzKTJJ2qghMcw2GKmC6guh4ichVSLCCSso/ pCzHyDR3wpeiSvNXl74wCbMRIncDVTJiRpvCiVkfWW+ouGGPLpF8aXkHG/z5O9fM 676XYFuYQwDFyMCO9/cid5H8AN5sCzSIunfFr5+GCvAjMYHIcbGaAvLQV5FSH+9/ 9Zd9IpcjR1mPaCCnIelZ =h8jA -----END PGP SIGNATURE----- --Md/poaVZ8hnGTzuv--