[PATCHv10 0/9] write hints with nvme fdp, scsi streams

[Johannes Thumshirn]

On 10.12.24 08:13, Christoph Hellwig wrote:
> On Thu, Dec 05, 2024 at 03:37:25PM -0500, Martin K. Petersen wrote:
>> The problem with option 2 is that when you're doing copy between two
>> different LUNs, then you suddenly have to maintain state in one kernel
>> object about stuff relating to another kernel object. I think that is
>> messy. Seems unnecessarily complex.
> 
> Generally agreeing with all you said, but do we actually have any
> serious use case for cross-LU copies?  They just seem incredibly
> complex any not all that useful.

One use case I can think of is (again) btrfs balance (GC, convert, etc) 
on a multi drive filesystem. BUT this use case is something that can 
just use the fallback read-write path as it is doing now.