linux-kernel - Re: [RFC PATCH 1/2] fs: introduce FALLOC_FL_FORCE

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Message-ID: <Z3wbqlfoZjisbe1x@infradead.org>
Date: Mon, 6 Jan 2025 10:06:34 -0800
From: Christoph Hellwig <hch@...radead.org>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: Christoph Hellwig <hch@...radead.org>, Theodore Ts'o <tytso@....edu>,
	Zhang Yi <yi.zhang@...weicloud.com>, linux-fsdevel@...r.kernel.org,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
	viro@...iv.linux.org.uk, brauner@...nel.org, jack@...e.cz,
	adilger.kernel@...ger.ca, yi.zhang@...wei.com,
	chengzhihao1@...wei.com, yukuai3@...wei.com, yangerkun@...wei.com,
	Sai Chaitanya Mitta <mittachaitu@...il.com>,
	linux-xfs@...r.kernel.org
Subject: Re: [RFC PATCH 1/2] fs: introduce FALLOC_FL_FORCE_ZERO to fallocate

On Mon, Jan 06, 2025 at 09:31:33AM -0800, Darrick J. Wong wrote:
> I think we should wire it up as a new FALLOC_FL_WRITE_ZEROES mode,
> document very vigorously that it exists to facilitate pure overwrites
> (specifically that it returns EOPNOTSUPP for always-cow files), and not
> add more ioctls.

That goes into a similar direction to what I'd prefer.

> (That said, doesn't BLKZEROOUT already do this for bdevs?)

Yes. But the same is true for the other fallocate modes on block
devices.