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Date:   Wed, 18 May 2022 06:47:34 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Liang Chen <liangchen.linux@gmail.com>
Cc:     linux-fsdevel@vger.kernel.org, hch@infradead.org,
        jmoyer@redhat.com, jack@suse.cz, lczerner@redhat.com
Subject: Re: [PATCH v2] fs: Fix page cache inconsistency when mixing buffered
 and AIO DIO for bdev
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On Sat, May 07, 2022 at 12:10:33PM +0800, Liang Chen wrote:
> From: Liang Chen <liangchen.linux@gmail.com>
> 
> As pointed out in commit 332391a, mixing buffered reads and asynchronous
> direct writes risks ending up with a situation where stale data is left
> in page cache while new data is already written to disk. The same problem
> hits block dev fs too. A similar approach needs to be taken here.

What is the real issue here?  If you mix direct and buffered I/O
you generally get what you pay for.  Even more so on block devices that
don't even follow Posix file system semantics.