linux-kernel - Re: [RFC v2 0/8] add support for blocksize > PAGE

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Date:   Fri, 26 May 2023 01:35:28 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     hughd@...gle.com, akpm@...ux-foundation.org, willy@...radead.org,
        brauner@...nel.org, djwong@...nel.org, p.raghav@...sung.com,
        da.gomez@...sung.com, rohan.puri@...sung.com,
        rpuri.linux@...il.com, a.manzanares@...sung.com, dave@...olabs.net,
        yosryahmed@...gle.com, keescook@...omium.org, hare@...e.de,
        kbusch@...nel.org, patches@...ts.linux.dev,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC v2 0/8] add support for blocksize > PAGE_SIZE

On Fri, May 26, 2023 at 01:28:03AM -0700, Christoph Hellwig wrote:
> On Fri, May 26, 2023 at 01:18:19AM -0700, Luis Chamberlain wrote:
> > On Fri, May 26, 2023 at 01:14:55AM -0700, Christoph Hellwig wrote:
> > > 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.
> > > 
> > > The concept of a block size doesn't make any sense for tmpfs.   What
> > > are you actually trying to do here?
> > 
> > More of helping to test high order folios for tmpfs. Swap for instance
> > would be one thing we could use to test.
> 
> I'm still not sure where the concept of a block size would come in here.

>From a filesystem perspective that's what we call it as well today, and
tmpfs implements a simple one, just that indeed this just a high order
folio support. The languge for blocksize was used before my patches for the
sb->s_blocksize and sb->s_blocksize_bits. Even for shmem_statfs()
buf->f_bsize.

I understand we should move the sb->s_blocksize to the block_device
and use the page order for address_space, but we can't negate the
existing stuff there immediately.

  Luis