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Date: Fri, 1 Apr 2022 16:09:40 +0800 (CST) From: <wang.yi59@....com.cn> To: <david@...morbit.com> Cc: <djwong@...nel.org>, <linux-xfs@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <xue.zhihong@....com.cn>, <wang.liang82@....com.cn>, <cheng.lin130@....com.cn> Subject: Re:[PATCH] xfs: getattr ignore blocks beyond eof > On Thu, Mar 31, 2022 at 04:32:07PM +0800, wang.yi59@....com.cn wrote: > > > We do not, and have not ever tried to, hide allocation or block > > > usage artifacts from userspace because any application that depends > > > on specific block allocation patterns or accounting from the > > > filesystem is broken by design. > > > > > > If your application is dependent on block counts exactly matching > > > the file data space for waht ever reason, then what speculative > > > preallocation does is the least of your problems. > > > > > > > Thanks for your explaination. > > > > Unfortunately, the app I'm using evaluates diskusage by querying > > the changes of the backend filesystem (XFS) file before and after > > the operation. > > What application is this? > > What is it trying to use this information for? Thanks very much, Dave. I'm trying to use a new xlater(module) named 'simple-quota' in glusterfs, which collects file's diskusage by stat, for quota function. > > I'm trying to understand why someone thought this was a good idea, > and without actually being able to look up the code and see what it > is using the information for, I can't really say much more than > "this seems broken by design". > > > Without giving up the benefits of preallocation, the > > app's statistics will become obsolete and no chance to correct it > > at a small cost, because of the silence reclaim of posteof blocks. > > That is the app's problem.
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