linux-ext4 - Re: [PATCH 27/27] direct-io: remove random prefetches

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Date:   Tue, 19 Apr 2022 14:55:17 +0200
From:   David Sterba <dsterba@...e.cz>
To:     Christoph Hellwig <hch@....de>
Cc:     Jens Axboe <axboe@...nel.dk>, dm-devel@...hat.com,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-um@...ts.infradead.org, linux-block@...r.kernel.org,
        drbd-dev@...ts.linbit.com, nbd@...er.debian.org,
        ceph-devel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        xen-devel@...ts.xenproject.org, linux-bcache@...r.kernel.org,
        linux-raid@...r.kernel.org, linux-mmc@...r.kernel.org,
        linux-mtd@...ts.infradead.org, linux-nvme@...ts.infradead.org,
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        target-devel@...r.kernel.org, linux-btrfs@...r.kernel.org,
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        ocfs2-devel@....oracle.com, linux-mm@...ck.org
Subject: Re: [PATCH 27/27] direct-io: remove random prefetches

On Fri, Apr 15, 2022 at 06:52:58AM +0200, Christoph Hellwig wrote:
> Randomly poking into block device internals for manual prefetches isn't
> exactly a very maintainable thing to do.  And none of the performance
> criticil direct I/O implementations still use this library function
> anyway, so just drop it.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>

That the direct io function needed a valid bdev just for the prefetch
but nothing else was one of the reasons we had to keep the latest_bdev
in btrfs, so good riddance.

You may want to add the reference to the patch that added the prefetch,
65dd2aa90aa1 ("dio: optimize cache misses in the submission path") and
also remove #include <linux/prefetch.h> as there are no more uses of
prefetch in the file.

With that

Reviewed-by: David Sterba <dsterba@...e.com>