Re: [PATCH v4 5/6] xfs: write stream based AG placement

[Kanchan Joshi <joshi.k@samsung.com>]

On 8/19/2026 12:59 PM, Christoph Hellwig wrote:
> On Fri, Jul 17, 2026 at 06:25:37PM +0530, Kanchan Joshi wrote:
>> If AGs are fewer than write streams, write streams are distributed into
>> available AGs in round robin fashion.
> 
> I think we should just limit the number of available write streams
> to the number of AG, as otherwise we'll get into a bit of a mess.

To confirm: given above quoting, for the other two cases (i.e., Streams 
<= AGs), are you open to stream-based AG-sets modulo inode hashing (that 
you suggested to skip in previous patch)?
And is this point only for the case when Streams > AGs?

This case can happen for hw streams, but for pure software streams, we 
will not hit this case because the filesystem determines the stream 
count based on the AG count.

> And for the case of the hardware write streams query them in mkfs
> to align the AG geometry to that.

If this is only for the streams > AGs case, the filesystem can just 
clamp down to match, turning it into a 'streams = AGs' case.
And that means no changes in mkfs. Is that fine?
Related benefit is to skip tricky mkfs AG calculations right for future 
device sizes and varying stream counts.