linux-kernel - Re: fall back from direct to buffered I/O when stable writes are required

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Message-ID: <20251112143858.GA3006@lst.de>
Date: Wed, 12 Nov 2025 15:38:58 +0100
From: hch <hch@....de>
To: Ming Lei <ming.lei@...hat.com>
Cc: hch <hch@....de>, Johannes Thumshirn <Johannes.Thumshirn@....com>,
	"Darrick J. Wong" <djwong@...nel.org>, Jan Kara <jack@...e.cz>,
	Keith Busch <kbusch@...nel.org>, Dave Chinner <david@...morbit.com>,
	Carlos Maiolino <cem@...nel.org>,
	Christian Brauner <brauner@...nel.org>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-raid@...r.kernel.org" <linux-raid@...r.kernel.org>,
	"linux-block@...r.kernel.org" <linux-block@...r.kernel.org>
Subject: Re: fall back from direct to buffered I/O when stable writes are
 required

On Wed, Nov 12, 2025 at 10:18:40PM +0800, Ming Lei wrote:
> Looks buffer overwrite is actually done by buggy software in guest side,
> why is qemu's trouble? Or will qemu IO emulator write to the IO buffer
> when guest IO is inflight?

It is ultimately caused by the guest.  But just like local software it
is in no way buggy just because you don't like the pattern.