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Date:   Mon, 14 Oct 2019 09:18:27 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     "Darrick J. Wong" <darrick.wong@oracle.com>
Cc:     Christoph Hellwig <hch@lst.de>, linux-xfs@vger.kernel.org
Subject: Re: [PATCH 1/2] xfs: disable xfs_ioc_space for always COW inodes
Message-ID: <20191014071827.GD10081@lst.de>
References: <20191011130316.13373-1-hch@lst.de> <20191011130316.13373-2-hch@lst.de> <20191012002954.GM13108@magnolia>
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On Fri, Oct 11, 2019 at 05:29:54PM -0700, Darrick J. Wong wrote:
> On Fri, Oct 11, 2019 at 03:03:15PM +0200, Christoph Hellwig wrote:
> > If we always have to write out of place preallocating blocks is
> > pointless.  We already check for this in the normal falloc path, but
> > the check was missig in the legacy ALLOCSP path.
> 
> This function handles other things than preallocation, such as
> XFS_IOC_ZERO_RANGE and XFS_IOC_UNRESVSP, which call xfs_zero_file_space
> and xfs_free_file_space, respectively.  We don't prohibit fallocate
> from calling those two functions on an always_cow inode, so why do that
> here?

True.  I actually have a patch in my tree that switches those to
be handled in the core so that they enter XFS through ->fallocate.
It didn't make any sense to send this patch before that other change,
sorry.