linux-kernel - Re: [PATCH 03/15] mm: Add file_offset_of

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Date:   Fri, 4 Oct 2019 12:39:12 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/15] mm: Add file_offset_of_ helpers

On Thu, Sep 26, 2019 at 05:02:11PM +0300, Kirill A. Shutemov wrote:
> On Tue, Sep 24, 2019 at 05:52:02PM -0700, Matthew Wilcox wrote:
> > From: "Matthew Wilcox (Oracle)" <willy@...radead.org>
> > 
> > The page_offset function is badly named for people reading the functions
> > which call it.  The natural meaning of a function with this name would
> > be 'offset within a page', not 'page offset in bytes within a file'.
> > Dave Chinner suggests file_offset_of_page() as a replacement function
> > name and I'm also adding file_offset_of_next_page() as a helper for the
> > large page work.  Also add kernel-doc for these functions so they show
> > up in the kernel API book.
> > 
> > page_offset() is retained as a compatibility define for now.
> 
> This should be trivial for coccinelle, right?

Yes, should be.  I'd prefer not to do conversions for now to minimise
conflicts when rebasing.

> > +static inline loff_t file_offset_of_next_page(struct page *page)
> > +{
> > +	return ((loff_t)page->index + compound_nr(page)) << PAGE_SHIFT;
> 
> Wouldn't it be more readable as
> 
> 	return file_offset_of_page(page) + page_size(page);
> 
> ?

Good idea.  I'll fix that up.