Date:   Fri, 3 Feb 2023 06:49:24 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Dave Chinner <david@fromorbit.com>
Cc:     Marcelo Tosatti <mtosatti@redhat.com>,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Matthew Wilcox <willy@infradead.org>,
        Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
        Frederic Weisbecker <frederic@kernel.org>,
        Leonardo Bras <leobras@redhat.com>,
        Yair Podemsky <ypodemsk@redhat.com>, P J P <ppandit@redhat.com>
Subject: Re: [PATCH v3] fs/buffer.c: update per-CPU bh_lru cache via RCU
Message-ID: <20230203054924.GA22730@lst.de>
References: <Y9qM68F+nDSYfrJ1@tpad> <20230202223653.GF937597@dread.disaster.area>
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On Fri, Feb 03, 2023 at 09:36:53AM +1100, Dave Chinner wrote:
> Rather than adding more complexity to the legacy bufferhead code,
> wouldn't it be better to switch the block device mapping to use
> iomap+folios and get rid of the use of bufferheads altogether?

It's not that simple unfortunately :(  All file systems that use
buffer heads also use them on the block device for metadata.  I have
a WIP block device iomap conversion, but it still has to offer
buffer_heads similar to the legacy path in iomap to make all that
work.