linux-ext4 - Re: [RFC PATCH v4 07/11] fs: statx add write zeroes unmap attribute

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Message-ID: <20250506050239.GA27687@lst.de>
Date: Tue, 6 May 2025 07:02:39 +0200
From: Christoph Hellwig <hch@....de>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: Christoph Hellwig <hch@....de>, Zhang Yi <yi.zhang@...weicloud.com>,
	linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
	linux-block@...r.kernel.org, dm-devel@...ts.linux.dev,
	linux-nvme@...ts.infradead.org, linux-scsi@...r.kernel.org,
	linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	tytso@....edu, john.g.garry@...cle.com, bmarzins@...hat.com,
	chaitanyak@...dia.com, shinichiro.kawasaki@....com,
	brauner@...nel.org, yi.zhang@...wei.com, chengzhihao1@...wei.com,
	yukuai3@...wei.com, yangerkun@...wei.com
Subject: Re: [RFC PATCH v4 07/11] fs: statx add write zeroes unmap attribute

On Mon, May 05, 2025 at 07:29:45AM -0700, Darrick J. Wong wrote:
> attributes_mask contains attribute flags known to the filesystem,
> whereas attributes contains flags actually set on the file.
> "known_attributes" would have been a better name, but that's water under
> the bridge. :P

Oooh.  I think I was very confused at what this patch does, and what
it does seems confused as well.

The patch adds a new flag to the STATX_ATTR_* namespace, which
historically was used for persistent on-disk flags like immutable,
not the STATX_* namespace where I assumed it, and which has no
support mask.  Which seems really odd for a pure kernel feature.
Then again it seems to follow STATX_ATTR_WRITE_ATOMIC which seems
just as wrongly place unless I'm missing something?