linux-kernel - Re: [RFC 00/23] Enable block size

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Message-ID: <ZQSnWUF2M1iNzGWM@casper.infradead.org>
Date:   Fri, 15 Sep 2023 19:50:01 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Pankaj Raghav <kernel@...kajraghav.com>
Cc:     linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        p.raghav@...sung.com, david@...morbit.com, da.gomez@...sung.com,
        akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        djwong@...nel.org, linux-mm@...ck.org, chandan.babu@...cle.com,
        mcgrof@...nel.org, gost.dev@...sung.com
Subject: Re: [RFC 00/23] Enable block size > page size in XFS

On Fri, Sep 15, 2023 at 08:38:25PM +0200, Pankaj Raghav wrote:
> Only XFS was enabled and tested as a part of this series as it has
> supported block sizes up to 64k and sector sizes up to 32k for years.
> The only thing missing was the page cache magic to enable bs > ps. However any filesystem
> that doesn't depend on buffer-heads and support larger block sizes
> already should be able to leverage this effort to also support LBS,
> bs > ps.

I think you should choose whether you're going to use 'bs > ps' or LBS
and stick to it.  They're both pretty inscrutable and using both
interchanagbly is worse.

But I think filesystems which use buffer_heads should be fine to support
bs > ps.  The problems with the buffer cache are really when you try to
support small block sizes and large folio sizes (eg arrays of bhs on
the stack).  Supporting bs == folio_size shouldn't be a problem.