linux-kernel - Re: [PATCH v4 6/9] f2fs: don't allow DIO reads but not DIO writes

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Date:   Sun, 21 Aug 2022 01:53:33 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Jaegeuk Kim <jaegeuk@...nel.org>, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
        linux-xfs@...r.kernel.org, linux-api@...r.kernel.org,
        linux-fscrypt@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, Keith Busch <kbusch@...nel.org>
Subject: Re: [PATCH v4 6/9] f2fs: don't allow DIO reads but not DIO writes

On Mon, Aug 15, 2022 at 05:55:45PM -0700, Eric Biggers wrote:
> So if the zoned device feature becomes widely adopted, then STATX_DIOALIGN will
> be useless on all Android devices?  That sounds undesirable.  Are you sure that

We just need to fix f2fs to support direct I/O on zone devices.  There
is not good reason not to support it, in fact the way how zoned devices
requires appends with the Zone Append semantics makes direct I/O way
safer than how f2fs does direct I/O currently on non-zoned devices.

Until then just supporting direct I/O reads on zoned devices for f2fs
seems like a really bad choice given that it will lead to nasty cache
incoherency.