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Date:   Thu, 12 Aug 2021 14:16:03 +0100
From:   Christoph Hellwig <hch@infradead.org>
To:     "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc:     linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 8/8] iomap: Add writethrough for O_SYNC
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On Wed, Aug 11, 2021 at 03:46:47AM +0100, Matthew Wilcox (Oracle) wrote:
> For O_SYNC writes, if the filesystem has already allocated blocks for
> the range, we can avoid marking the page as dirty and skip straight to
> marking the page as writeback.

So this just optimizes O_SYNC overwrites.  How common are those for
bufered I/O?  I know databases use them a lot with direct I/O, but for
buffere I/O this seems like an odd I/O pattern.