From: Jiaying Zhang Subject: Re: Question on fallocate/ftruncate sequence Date: Fri, 28 Aug 2009 11:42:59 -0700 Message-ID: <5df78e1d0908281142r683b902ube65288df858695d@mail.gmail.com> References: <6601abe90907200936w61ebda92reae368a2b9efac66@mail.gmail.com> <1248211771.20743.2.camel@bobble.smo.corp.google.com> <20090721215421.GM4231@webber.adilger.int> <1248304214.14463.17.camel@bobble.smo.corp.google.com> <4A67D36D.20708@redhat.com> <1248366422.27509.1.camel@bobble.smo.corp.google.com> <4A689723.7000805@redhat.com> <1248372301.31323.2.camel@bobble.smo.corp.google.com> <20090723215614.GF4231@webber.adilger.int> <1248389165.17459.3.camel@bobble.smo.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Andreas Dilger , Eric Sandeen , Curt Wohlgemuth , ext4 development To: Frank Mayhar Return-path: Received: from smtp-out.google.com ([216.239.33.17]:23479 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752032AbZH1SnN convert rfc822-to-8bit (ORCPT ); Fri, 28 Aug 2009 14:43:13 -0400 Received: from spaceape13.eur.corp.google.com (spaceape13.eur.corp.google.com [172.28.16.147]) by smtp-out.google.com with ESMTP id n7SIhCsR017680 for ; Fri, 28 Aug 2009 19:43:12 +0100 Received: from qyk34 (qyk34.prod.google.com [10.241.83.162]) by spaceape13.eur.corp.google.com with ESMTP id n7SIh9tO013390 for ; Fri, 28 Aug 2009 11:43:10 -0700 Received: by qyk34 with SMTP id 34so1338989qyk.12 for ; Fri, 28 Aug 2009 11:43:09 -0700 (PDT) In-Reply-To: <1248389165.17459.3.camel@bobble.smo.corp.google.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: Sorry for joining the conversation late. Frank and I had a discussion o= n this problem this morning. We wonder whether we can just add the checking on whether i_blocks is consistent with i_size during truncate. Here is = the patch I tried and it seems to have solved the problem. I.e., the space = reserved in fallocate(KEEP_SIZE) is now freed in the next truncate. --- git-linux/fs/attr.c 2009-05-20 18:05:55.000000000 -0700 +++ linux-2.6.30.5/fs/attr.c 2009-08-27 14:34:48.000000000 -0700 @@ -68,7 +68,8 @@ int inode_setattr(struct inode * inode, unsigned int ia_valid =3D attr->ia_valid; if (ia_valid & ATTR_SIZE && - attr->ia_size !=3D i_size_read(inode)) { + (attr->ia_size !=3D i_size_read(inode) || + attr->ia_size >> 9 < inode->i_blocks - 1)) { int error =3D vmtruncate(inode, attr->ia_size); if (error) return error; One thing I am not sure is whether adding this check in inode_setattr m= ay cause any problem in other cases. I saw inode_setattr is called at many places as well as during ftruncate. Any opinions on this proposed solut= ion? Jiaying On Thu, Jul 23, 2009 at 3:46 PM, Frank Mayhar wrote= : > On Thu, 2009-07-23 at 15:56 -0600, Andreas Dilger wrote: >> On Jul 23, 2009 =A011:05 -0700, Frank Mayhar wrote: >> > On Thu, 2009-07-23 at 12:00 -0500, Eric Sandeen wrote: >> > > Sorry I skimmed to fast, skipped over the fsck part. =A0But: >> > > >> > > # touch /mnt/test/testfile >> > > # /root/fallocate -n -l 16m /mnt/test/testfile >> > > # ls -l /mnt/test/testfile >> > > -rw-r--r-- 1 root root 0 Jul 23 12:13 /mnt/test/testfile >> > > # du -h /mnt/test/testfile >> > > 16M =A0 =A0 =A0 /mnt/test/testfile >> > > >> > > there doesn't seem to be a problem in fsck w/ block past EOF, or= am I >> > > missing something else? >> > >> > I was taking Andreas' word for it but now that you mention it, I s= ee the >> > same thing. =A0Andreas, did you have a specific case in mind? >> >> Ted and I had discussed this in the past, maybe he fixed e2fsck to n= ot >> change the file size when there are blocks allocated beyond EOF. =A0= Having >> a flag wouldn't be a terrible idea, IMHO, so that e2fsck can make a >> better decision on whether the size or the blocks count are more cor= rect. >> I'm not dead set on it. > > For the moment I'm going to table the e2fsck change and make the flag > memory-only. =A0It'll be easy enough to change this if and when you g= uys > come to an agreement about what is right. > > As for the flag itself, I'll pick a bit that doesn't conflict with > anything else and leave reconciling the already-conflicting bits to y= ou > guys. > -- > Frank Mayhar > Google, Inc. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4"= in > the body of a message to majordomo@vger.kernel.org > More majordomo info at =A0http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html