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Date:   Fri, 26 May 2023 14:54:12 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Luis Chamberlain <mcgrof@kernel.org>
Cc:     hughd@google.com, akpm@linux-foundation.org, brauner@kernel.org,
        djwong@kernel.org, p.raghav@samsung.com, da.gomez@samsung.com,
        rohan.puri@samsung.com, rpuri.linux@gmail.com,
        a.manzanares@samsung.com, dave@stgolabs.net, yosryahmed@google.com,
        keescook@chromium.org, hare@suse.de, kbusch@kernel.org,
        patches@lists.linux.dev, linux-block@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC v2 0/8] add support for blocksize > PAGE_SIZE
Message-ID: <ZHC6BM+ehSC5Atv8@casper.infradead.org>
References: <20230526075552.363524-1-mcgrof@kernel.org>
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On Fri, May 26, 2023 at 12:55:44AM -0700, Luis Chamberlain wrote:
> This is an initial attempt to add support for block size > PAGE_SIZE for tmpfs.
> Why would you want this? It helps us experiment with higher order folio uses
> with fs APIS and helps us test out corner cases which would likely need
> to be accounted for sooner or later if and when filesystems enable support
> for this. Better review early and burn early than continue on in the wrong
> direction so looking for early feedback.

I think this is entirely the wrong direction to go in.

You're coming at this from a block layer perspective, and we have two
ways of doing large block devices -- qemu nvme and brd.  tmpfs should
be like other filesystems and opportunistically use folios of whatever
size makes sense.

Don't add a mount option to specify what size folios to use.