linux-kernel - Re: [PATCH 02/15] fs: Introduce i_blocks_per

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Message-ID: <20191004192812.GK32665@bombadil.infradead.org>
Date:   Fri, 4 Oct 2019 12:28:12 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Dave Chinner <david@...morbit.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/15] fs: Introduce i_blocks_per_page

On Wed, Sep 25, 2019 at 06:36:50PM +1000, Dave Chinner wrote:
> I'm actually working on abstrcting this code from both block size
> and page size via the helpers below. We ahve need to support block
> size > page size, and so that requires touching a bunch of all the
> same code as this patchset. I'm currently trying to combine your
> last patch set with my patchset so I can easily test allocating 64k
> page cache pages on a 64k block size filesystem on a 4k page size
> machine with XFS....

This all makes sense ...

> > -	if (iop || i_blocksize(inode) == PAGE_SIZE)
> > +	if (iop || i_blocks_per_page(inode, page) <= 1)
> >  		return iop;
> 
> That also means checks like these become:
> 
> 	if (iop || iomap_chunks_per_page(inode, page) <= 1)
> 
> as a single file can now have multiple pages per block, a page per
> block and multiple blocks per page as the page size changes...
> 
> I'd like to only have to make one pass over this code to abstract
> out page and block sizes, so I'm guessing we'll need to do some
> co-ordination here....

Yup.  I'm happy if you want to send your patches out; I'll keep going
with the patches I have for the moment, and we'll figure out how to
merge the two series in a way that makes sense.