linux-ext4 - Re: [PATCH 6/6] xfs: refactor xfs_file

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Message-ID: <20240829035627.GC4023@lst.de>
Date: Thu, 29 Aug 2024 05:56:27 +0200
From: Christoph Hellwig <hch@....de>
To: Dave Chinner <david@...morbit.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>,
	Brian Foster <bfoster@...hat.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 6/6] xfs: refactor xfs_file_fallocate

On Thu, Aug 29, 2024 at 01:11:11PM +1000, Dave Chinner wrote:
> > +xfs_falloc_allocate_range(
> > +	struct file		*file,
> > +	int			mode,
> > +	loff_t			offset,
> > +	loff_t			len)
> > +{
> > +	struct inode		*inode = file_inode(file);
> > +	loff_t			new_size = 0;
> > +	int			error;
> > +
> > +	/*
> > +	 * If always_cow mode we can't use preallocations and thus should not
> > +	 * create them.
> > +	 */
> > +	if (xfs_is_always_cow_inode(XFS_I(inode)))
> > +		return -EOPNOTSUPP;
> 
> ... our preallocation operation always returns -EOPNOTSUPP for
> COW mode.
> 
> Should the zeroing code also have this COW mode check in it after
> the hole punch has run so we don't do unnecessary prealloc there?

The low-level block allocation helper just returns early without
doing work (move a bit, but not changed in behavior earlier in the
series).  So it won't actually do the prealloc.

> 
> -Dave.
> -- 
> Dave Chinner
> david@...morbit.com
---end quoted text---