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Date: Wed, 14 Jan 2026 13:39:54 +0100
From: Christoph Hellwig <hch@lst.de>
To: Qu Wenruo <wqu@suse.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	Christian Brauner <brauner@kernel.org>,
	"Darrick J. Wong" <djwong@kernel.org>,
	Carlos Maiolino <cem@kernel.org>, Al Viro <viro@zeniv.linux.org.uk>,
	linux-block@vger.kernel.org, linux-xfs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: bounce buffer direct I/O when stable pages are required
Message-ID: <20260114123954.GA4430@lst.de>
References: <20260114074145.3396036-1-hch@lst.de> <f5568a83-75df-4e84-8cf0-01df6dd4e810@suse.com>
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On Wed, Jan 14, 2026 at 08:22:27PM +1030, Qu Wenruo wrote:
> I guess the final reason to bounce other than falling back to buffered IO 
> is still performance, especially for AIO cases?

It is to support AIO and parallel writers, yes.

> If iomap is going to handle the page bouncing I guess we btrfs people will 
> be pretty happy to use that, without implementing our own bouncing code.

Given that btrfs runs all read completions from a workqueue I think
just setting the new IOMAP_DIO_BOUNCE flag and otherwise reverting
to the old direct I/O implementation should be all that is needed.