linux-kernel - Re: [PATCH] xfs: Check for deallayed allocations before setting extsize

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Message-ID: <Zv+tfQhBdxuownfv@li-bb2b2a4c-3307-11b2-a85c-8fa5c3a69313.ibm.com>
Date: Fri, 4 Oct 2024 14:26:07 +0530
From: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
To: Christoph Hellwig <hch@...radead.org>
Cc: linux-xfs@...r.kernel.org, Ritesh Harjani <ritesh.list@...il.com>,
        linux-kernel@...r.kernel.org, "Darrick J . Wong" <djwong@...nel.org>,
        dchinner@...hat.com, Chandan Babu R <chandan.babu@...cle.com>
Subject: Re: [PATCH] xfs: Check for deallayed allocations before setting
 extsize

On Thu, Oct 03, 2024 at 07:38:11AM -0700, Christoph Hellwig wrote:
> On Thu, Oct 03, 2024 at 03:42:07PM +0530, Ojaswin Mujoo wrote:
> > Extsize is allowed to be set on files with no data in it. For this,
> > we were checking if the files have extents but missed to check if
> > delayed extents were present. This patch adds that check.
> > 
> > **Without the patch (SUCCEEDS)**
> > 
> > $ xfs_io -c 'open -f testfile' -c 'pwrite 0 1024' -c 'extsize 65536'
> 
> Can you add a testcase for this to xfstests?

Hi Christoph, actually now that we are also planning to use this for
atomic writes, we are thinking to add a generic extsize ioctl 
test to check for:

1. Setting hint on empty file should pass
2. Setting hint on a file with delayed allocation data should fail
3. Setting hint on a file with allocated data should fail
4. Setting hint on a file which is truncated to size 0 after write should pass

So that should cover this for ext4 and xfs as well.

> 
> > -	if (S_ISREG(VFS_I(ip)->i_mode) && ip->i_df.if_nextents &&
> > +	if (S_ISREG(VFS_I(ip)->i_mode) &&
> > +	    (ip->i_df.if_nextents || ip->i_delayed_blks) &&
> 
> We have two other copies of the
> 
> 	ip->i_df.if_nextents || ip->i_delayed_blks
> 
> pattern to check if there is any data on the inode in xfs_inactive and
> xfs_ioctl_setattr_xflags.  Maybe facto this into a documented helper?

Sure I can do this.

> 
> Otherwise looks good:
> 
> Reviewed-by: Christoph Hellwig <hch@....de>
> 

Thanks for the review.

Regards,
ojaswin