Re: RWF_DONTCACHE documentation

[Jens Axboe <axboe@kernel.dk>]

On 6/3/25 12:20 AM, Johannes Thumshirn wrote:
> On 02.06.25 17:53, Jens Axboe wrote:
>> On 6/2/25 9:00 AM, Christoph Hellwig wrote:
>>> Hi Jens,
>>>
>>> I just tried to reference RWF_DONTCACHE semantics in a standards
>>> discussion, but it doesn't seem to be documented in the man pages
>>> or in fact anywhere else I could easily find.  Could you please write
>>> up the semantics for the preadv2/pwritev2 man page?
>>
>> Sure, I can write up something for the man page.
>>
> 
> Hi Jens,
> 
> Small sidetrack here. What happened to the ext4 and btrfs support of 
> RWF_DONTCACHE? I remember seeing your series having ext4 and btrfs 
> support as well but in current master only xfs is setting FOP_DONTCACHE.

The btrfs support got queued up, that's all I know on that front. For
ext4, it needed a bit of a hack [1] and there was some chatter on
converting the write side to iomap, which would eliminate the need for
that hack. The last fs patches I had on top of the core bits was:

https://git.kernel.dk/cgit/linux/log/?h=buffered-uncached-fs.11

in case you or someone else wants to pursue those parts.

[1] https://git.kernel.dk/cgit/linux/commit/?h=buffered-uncached-fs.11&id=92df0ef308d0bfbbc26a7efa1d571a506fd8fee3

-- 
Jens Axboe