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Date: Fri, 1 Nov 2024 01:03:02 +0000
From: Jaegeuk Kim <jaegeuk@kernel.org>
To: Bart Van Assche <bvanassche@acm.org>
Cc: Christoph Hellwig <hch@lst.de>, Keith Busch <kbusch@kernel.org>,
	Keith Busch <kbusch@meta.com>, linux-block@vger.kernel.org,
	linux-nvme@lists.infradead.org, linux-scsi@vger.kernel.org,
	io-uring@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	joshi.k@samsung.com, javier.gonz@samsung.com,
	Hannes Reinecke <hare@suse.de>,
	"Martin K . Petersen" <martin.petersen@oracle.com>
Subject: Re: [PATCHv10 9/9] scsi: set permanent stream count in block limits
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In-Reply-To: <f644c6b2-7549-458d-8a24-07aa44c4b4ee@acm.org>

On 10/30, Bart Van Assche wrote:
> On 10/30/24 10:14 AM, Christoph Hellwig wrote:
> > On Wed, Oct 30, 2024 at 09:59:24AM -0700, Bart Van Assche wrote:
> > > 
> > > On 10/29/24 9:55 PM, Christoph Hellwig wrote:
> > > > For the temperature hints the only public user I known is rocksdb, and
> > > > that only started working when Hans fixed a brown paperbag bug in the
> > > > rocksdb code a while ago.  Given that f2fs interprets the hints I suspect
> > > > something in the Android world does as well, maybe Bart knows more.
> > > 
> > > UFS devices typically have less internal memory (SRAM) than the size of a
> > > single zone.
> > 
> > That wasn't quite the question.  Do you know what application in android
> > set the fcntl temperature hints?
> 
> I do not know whether there are any Android apps that use the
> F_SET_(FILE_|)RW_HINT fcntls.
> 
> The only use case in Android platform code I know of is this one: Daejun
> Park, "f2fs-tools: add write hint support", f2fs-dev mailing list,
> September 2024 (https://lore.kernel.org/all/20240904011217epcms2p5a1b15db8e0ae50884429da7be4af4de4@epcms2p5/T/).
> As you probably know f2fs-tools is a software package that includes
> fsck.f2fs.
> 
> Jaegeuk, please correct me if necessary.

Yes, f2fs-tools in Android calls fcntl(fd, F_SET_RW_HINT, &hint);

> 
> Bart.
> 
>