linux-kernel - Re: [PATCH v3] fs/buffer.c: update per-CPU bh

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Message-ID: <20230203054924.GA22730@lst.de>
Date:   Fri, 3 Feb 2023 06:49:24 +0100
From:   Christoph Hellwig <hch@....de>
To:     Dave Chinner <david@...morbit.com>
Cc:     Marcelo Tosatti <mtosatti@...hat.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Matthew Wilcox <willy@...radead.org>,
        Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        Frederic Weisbecker <frederic@...nel.org>,
        Leonardo Bras <leobras@...hat.com>,
        Yair Podemsky <ypodemsk@...hat.com>, P J P <ppandit@...hat.com>
Subject: Re: [PATCH v3] fs/buffer.c: update per-CPU bh_lru cache via RCU

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.