From: =?ISO-8859-15?Q?Luk=E1=A8_Czerner?= Subject: Re: [PATCH 04/12 v2] xfs: pass LLONG_MAX to truncate_inode_pages_range Date: Mon, 16 Jul 2012 09:13:44 +0200 (CEST) Message-ID: References: <1342185555-21146-1-git-send-email-lczerner@redhat.com> <1342185555-21146-4-git-send-email-lczerner@redhat.com> <20120715231117.GD30524@devil.redhat.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Lukas Czerner , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, tytso@mit.edu, achender@linux.vnet.ibm.com To: Dave Chinner Return-path: Received: from mx1.redhat.com ([209.132.183.28]:43183 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752500Ab2GPHNv (ORCPT ); Mon, 16 Jul 2012 03:13:51 -0400 In-Reply-To: <20120715231117.GD30524@devil.redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, 16 Jul 2012, Dave Chinner wrote: > Date: Mon, 16 Jul 2012 09:11:17 +1000 > From: Dave Chinner > To: Lukas Czerner > Cc: linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, tytso@mit.edu, > achender@linux.vnet.ibm.com > Subject: Re: [PATCH 04/12 v2] xfs: pass LLONG_MAX to > truncate_inode_pages_range > > On Fri, Jul 13, 2012 at 03:19:07PM +0200, Lukas Czerner wrote: > > Currently we're passing -1 to truncate_inode_pages_range() which is > > actually really confusing since the argument is signed so we do not get > > "huge" number as one would expect, but rather just -1. To make things > > clearer and easier for truncate_inode_pages_range() just pass LLONG_MAX > > since it is actually what was intended anyway. > > > > It also makes thing easier for allowing truncate_inode_pages_range() to > > handle non page aligned regions. Moreover letting the lend argument to > > be negative might actually hide some bugs. > > > > Signed-off-by: Lukas Czerner > > Cc: Dave Chinner > > --- > > fs/xfs/xfs_fs_subr.c | 6 ++++-- > > 1 files changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/fs/xfs/xfs_fs_subr.c b/fs/xfs/xfs_fs_subr.c > > index 652b875..6e9b052 100644 > > --- a/fs/xfs/xfs_fs_subr.c > > +++ b/fs/xfs/xfs_fs_subr.c > > @@ -34,7 +34,8 @@ xfs_tosspages( > > { > > /* can't toss partial tail pages, so mask them out */ > > last &= ~(PAGE_SIZE - 1); > > - truncate_inode_pages_range(VFS_I(ip)->i_mapping, first, last - 1); > > + truncate_inode_pages_range(VFS_I(ip)->i_mapping, first, > > + last == -1 ? LLONG_MAX : last); > > The last paramter changed from (last -1) to last. so if we pass in > last = 16384, we now truncate to 16384 (first byte of page index 5) > instead of 16383 (last byte of page index 4). That's a change of > behaviour and a potential off-by one error, right? Right, this could potentially cause off-by-one errors, but as it is now I do not think this could happen. The only place where it is used with a proper range is XFS_IOC_ZERO_RANGE and you're going to convert the whole range to unwritten anyway. But it was unintended and I\ll fix it. > > > @@ -53,7 +54,8 @@ xfs_flushinval_pages( > > ret = filemap_write_and_wait_range(mapping, first, > > last == -1 ? LLONG_MAX : last); > > if (!ret) > > - truncate_inode_pages_range(mapping, first, last); > > + truncate_inode_pages_range(mapping, first, > > + last == -1 ? LLONG_MAX : last); > > Given this is also done immediately above in the function, perhaps > this should be done before anything: > > if (last == -1) > last = LLONG_MAX; > > and the parameter simply passed to the two functions without the > conditional logic? Yes, it makes sense to do this, I'll change it in the next iteration. Thanks for the review Dave. -Lukas > > Cheers, > > Dave. >