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Date: Mon, 28 Oct 2024 12:59:32 +0100
From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <kbusch@meta.com>
Cc: 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, hch@lst.de, joshi.k@samsung.com,
	javier.gonz@samsung.com, bvanassche@acm.org,
	Keith Busch <kbusch@kernel.org>
Subject: Re: [PATCHv9 4/7] block, fs: add write hint to kiocb
Message-ID: <20241028115932.GE8517@lst.de>
References: <20241025213645.3464331-1-kbusch@meta.com> <20241025213645.3464331-5-kbusch@meta.com>
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On Fri, Oct 25, 2024 at 02:36:42PM -0700, Keith Busch wrote:
> +static u16 blkdev_write_hint(struct kiocb *iocb, struct block_device *bdev)
> +{
> +	u16 hint = iocb->ki_write_hint;
> +
> +	if (!hint)
> +		return file_inode(iocb->ki_filp)->i_write_hint;
> +
> +	if (hint > bdev_max_write_hints(bdev))
> +		return file_inode(iocb->ki_filp)->i_write_hint;
> +
> +	if (bdev_is_partition(bdev) &&
> +	    !test_bit(hint - 1, bdev->write_hint_mask))
> +		return file_inode(iocb->ki_filp)->i_write_hint;

I would have expected an error when using an invalid stream identifier.

That of course requires telling the application how many are available
through e.g. statx as requested last time.