Re: [PATCH 8/9] xfs: stop the steal (of data blocks for RT indirect blocks)

[Christoph Hellwig <hch@lst.de>]

On Tue, Feb 20, 2024 at 10:47:12AM +1100, Dave Chinner wrote:
> Ok. If you delay the ip->i_delayed_blks and quota accounting until
> after the incore extent tree updates are done, this code doesn't
> need to undo anything and can just return an error. We should also
> keep in mind that an error here will likely cause a filesystem
> shutdown when the transaction is canceled....

Yes.  However (as documented in the commit log), the only place where
I think it can actually happen is on a buffered write errors as "real"
hole punches always flush delalloc space before.

> FWIW, if we are going to do this for rt, we should probably also
> consider do it for normal delalloc conversion when the indlen
> reservation runs out due to excessive fragmentation of large
> extents. Separate patch and all that, but it doesn't really make
> sense to me to only do this for RT when we know it is also needed in
> reare cases on non-rt workloads...

Can it happen for non-RT extents?  That would assume the required new
indirect block reservation for splitting an extent would have to be
larger than the amount we punch out.