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Date: Wed, 18 Sep 2024 07:10:29 +0200
From: Christoph Hellwig <hch@lst.de>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>,
	Chandan Babu R <chandan.babu@oracle.com>,
	Christian Brauner <brauner@kernel.org>, linux-xfs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 07/12] xfs: take XFS_MMAPLOCK_EXCL
 xfs_file_write_zero_eof
Message-ID: <20240918051029.GB31238@lst.de>
References: <20240910043949.3481298-1-hch@lst.de> <20240910043949.3481298-8-hch@lst.de> <20240917212427.GD182177@frogsfrogsfrogs>
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On Tue, Sep 17, 2024 at 02:24:27PM -0700, Darrick J. Wong wrote:
> Ah, ok, so we're taking the invalidate_lock so that we can't have page
> faults that might add folios (or dirty existing ones) in the mapping.
> We're the only ones who can access the page cache, and we're doing that
> so that we can zero the folios between the old EOF and the start of the
> write region.
> 
> Is that right?  Then

Yes.

We might eventually also relax this a bit to only take the look if
we actually zero anything, but for that we need to do the work to
turn the iomap iterators inside out first.