From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anton Altaparmakov Subject: Re: [patch] loop.c to use write ops for fs requiring special locking Date: Sat, 11 Mar 2006 00:36:18 +0000 (GMT) Message-ID: References: <1141231737.15117.88.camel@technetium.msp.redhat.com> <20060301140902.53350bb6.akpm@osdl.org> <1142031897.27533.40.camel@technetium.msp.redhat.com> <20060310151353.584ddfd5.akpm@osdl.org> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Robert S Peterson , linux-fsdevel@vger.kernel.org Return-path: Received: from ppsw-0.csi.cam.ac.uk ([131.111.8.130]:15534 "EHLO ppsw-0.csi.cam.ac.uk") by vger.kernel.org with ESMTP id S1750755AbWCKAgb (ORCPT ); Fri, 10 Mar 2006 19:36:31 -0500 To: Andrew Morton In-Reply-To: <20060310151353.584ddfd5.akpm@osdl.org> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Fri, 10 Mar 2006, Andrew Morton wrote: > Robert S Peterson wrote: > > On Thu, 2006-03-02 at 10:16 +0000, Anton Altaparmakov wrote: > > > It is simply that it is faster on all file systems that can use > > > prepare_write/commit_write and the "performance hungry" would have > > > complained if it were to be removed. > > (snip) > > > Anton > > > > Having heard no objections to my loop.c patch, when can I expect it to > > be integrated into the 2.6 kernel? > > When we've remembered what Al's statement meant in > http://marc.theaimsgroup.com/?t=102129995600002&r=1&w=2 > > I knew at the time, but I've forgotten. Maybe the issue went away.. The comment is that the patch put forward by Urban in the above thread replaced the use of readpage for reading with file ->read and prepare_write/commit_write for writing with file ->write without thinking about it. So he left out the entire transformation on the data which is what Al correctly complained about. I.e. Urban's patch made loop only work for a "straight" loopback mount without any changes to the data (i.e. crypto) applied to it. This is no longer relevant because my patch which is in current 2.6 kernels (can't remember when I wrote it/when it got put into 2.6) did the conversion from prepare_write/commit_write to file ->write correctly so the data transformation still happens so that crypto still works with the loop driver. To get back to Robert's patch that he is requesting to be included. I think it is fine but the flag name could perhaps be better. Perhaps "FS_AOPS_PRIVATE" or "FS_AOPS_SPECIAL" or "FS_AOPS_NEED_LOCKING" or even "FS_AOPS_REQUIRE_LOCKING" or something. "FS_REQUIRES_LOCKING" just does not mean much and certainly would not suggest to me that no-one outside the file system should use the address space operations of the file system... But maybe I am just bein picky. (-: Best regards, Anton -- Anton Altaparmakov (replace at with @) Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net WWW: http://linux-ntfs.sf.net/ & http://www-stu.christs.cam.ac.uk/~aia21/