linux-ext4 - Re: [PATCH 3/6] fs: sort out the fallocate mode vs flag mess

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Message-ID: <20240821131428.GA22423@lst.de>
Date: Wed, 21 Aug 2024 15:14:28 +0200
From: Christoph Hellwig <hch@....de>
To: Brian Foster <bfoster@...hat.com>
Cc: Christoph Hellwig <hch@....de>, Christian Brauner <brauner@...nel.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Chandan Babu R <chandan.babu@...cle.com>,
	Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@...e.cz>,
	"Darrick J. Wong" <djwong@...nel.org>,
	Theodore Ts'o <tytso@....edu>, linux-block@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-xfs@...r.kernel.org,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 3/6] fs: sort out the fallocate mode vs flag mess

On Wed, Aug 21, 2024 at 08:43:14AM -0400, Brian Foster wrote:
> > -	if ((mode & ~FALLOC_FL_KEEP_SIZE) && IS_APPEND(inode))
> > +	if (mode != FALLOC_FL_ALLOCATE_RANGE && IS_APPEND(inode))
> >  		return -EPERM;
> 
> Unless I'm misreading, this changes semantics by enforcing that we
> cannot use KEEP_SIZE on append only files. That means one can no longer
> do a post-eof prealloc without actually changing the file size, which on
> a quick test seems to work today.

No, I think it was me misreading the old code.  And I'm a little worried
that no test cought it.