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

[Johannes Thumshirn <Johannes.Thumshirn@wdc.com>]

On 11.11.24 10:41, Javier Gonzalez wrote:
> On 11.11.2024 09:37, Johannes Thumshirn wrote:
>> On 11.11.24 10:31, Javier Gonzalez wrote:
>>> On 11.11.2024 07:51, Christoph Hellwig wrote:
>>>> On Fri, Nov 08, 2024 at 05:43:44PM +0000, Javier Gonzalez wrote:
>>>>> We have been iterating in the patches for years, but it is unfortunately
>>>>> one of these series that go in circles forever. I don't think it is due
>>>>> to any specific problem, but mostly due to unaligned requests form
>>>>> different folks reviewing. Last time I talked to Damien he asked me to
>>>>> send the patches again; we have not followed through due to bandwidth.
>>>>
>>>> A big problem is that it actually lacks a killer use case.  If you'd
>>>> actually manage to plug it into an in-kernel user and show a real
>>>> speedup people might actually be interested in it and help optimizing
>>>> for it.
>>>>
>>>
>>> Agree. Initially it was all about ZNS. Seems ZUFS can use it.
>>>
>>> Then we saw good results in offload to target on NVMe-OF, similar to
>>> copy_file_range, but that does not seem to be enough. You seem to
>>> indicacte too that XFS can use it for GC.
>>>
>>> We can try putting a new series out to see where we are...
>>
>> I don't want to sound like a broken record, but I've said more than
>> once, that btrfs (regardless of zoned or non-zoned) would be very
>> interested in that as well and I'd be willing to help with the code or
>> even do it myself once the block bits are in.
>>
>> But apparently my voice doesn't count here
> 
> You are right. Sorry I forgot.
> 
> Would this be through copy_file_range or something different?
> 

Unfortunately not, brtfs' reclaim/balance path is a wrapper on top of 
buffered read and write (plus some extra things). _BUT_ this makes it 
possible to switch the read/write part and do copy offload (where possible).