Re: [PATCH v4 3/6] xfs: implement write-stream management support

[Christoph Hellwig <hch@lst.de>]

On Fri, Jul 31, 2026 at 01:33:04PM +0530, Kanchan Joshi wrote:
> On 7/21/2026 8:38 AM, Darrick J. Wong wrote:
> >> Write streams, filestreams, and write-life-time hints are mutually exclusive;
> >> combining any two of them returns -EINVAL:
> >>    - GET_MAX reports 0 whenever xfs_inode_is_filestream() is true,
> >>      covering both mount-wide filestreams and the per-inode chattr
> >>      flag. Also when the file is on the realtime device.
> >>    - SET refuses to bind a stream to a file that already has a
> >>      write-life-time hint (fcntl F_SET_RW_HINT), is filestream, or is
> >>      on the realtime device.
> >>    - chattr refuses to set the filestream or realtime flag on a file
> >>      that already has a write stream set.
> > These special "files" that represent stream ids could be generic code
> > instaed of in xfs.  AFAICT the only thing you need from xfs is a pointer
> > from struct xfs_inode to struct (xfs_)write_stream, right?
> 
> Right. Is it fine if we come to it when everything else is settled.
> I was hoping to lift common things up when write-stream is applied on 
> another FS.

Yes, I think this really needs to move to common code.  If we can find
a hole in struct inode, moving the write_stream id to that would probably
clean that up a lot.