Re: [PATCH 12/21] fs: xfs: Introduce FORCEALIGN inode flag

[Christoph Hellwig]

On Fri, Sep 29, 2023 at 10:27:17AM +0000, John Garry wrote:
> From: "Darrick J. Wong" <djwong@xxxxxxxxxx>
> 
> Add a new inode flag to require that all file data extent mappings must
> be aligned (both the file offset range and the allocated space itself)
> to the extent size hint.  Having a separate COW extent size hint is no
> longer allowed.
> 
> The goal here is to enable sysadmins and users to mandate that all space
> mappings in a file must have a startoff/blockcount that are aligned to
> (say) a 2MB alignment and that the startblock/blockcount will follow the
> same alignment.

This needs a good explanation of why someone would want this.