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Subject: Re: [PATCH v10 11/33] mm: Handle per-folio private data
To:     "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        akpm@linux-foundation.org
Cc:     linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
        Jeff Layton <jlayton@kernel.org>
References: <20210511214735.1836149-1-willy@infradead.org>
 <20210511214735.1836149-12-willy@infradead.org>
From:   Vlastimil Babka <vbabka@suse.cz>
Message-ID: <9a748624-5f07-acf2-667a-39fc271f830d@suse.cz>
Date:   Fri, 14 May 2021 17:41:28 +0200
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On 5/11/21 11:47 PM, Matthew Wilcox (Oracle) wrote:
> Add folio_get_private() which mirrors page_private() -- ie folio private
> data is the same as page private data.  The only difference is that these
> return a void * instead of an unsigned long, which matches the majority
> of users.
> 
> Turn attach_page_private() into folio_attach_private() and reimplement
> attach_page_private() as a wrapper.  No filesystem which uses page private
> data currently supports compound pages, so we're free to define the rules.
> attach_page_private() may only be called on a head page; if you want
> to add private data to a tail page, you can call set_page_private()
> directly (and shouldn't increment the page refcount!  That should be
> done when adding private data to the head page / folio).
> 
> This saves 597 bytes of text with the distro-derived config that I'm
> testing due to removing the calls to compound_head() in get_page()
> & put_page().
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Acked-by: Jeff Layton <jlayton@kernel.org>


Acked-by: Vlastimil Babka <vbabka@suse.cz>