linux-kernel - Re: [RFC PATCH 3/3] fb_defio: do not use deprecated page->mapping, index fields

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Z362xoQMxQRxYUlJ@casper.infradead.org>
Date: Wed, 8 Jan 2025 17:32:54 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Jaya Kumar <jayalk@...works.biz>, Simona Vetter <simona@...ll.ch>,
	Helge Deller <deller@....de>, linux-fbdev@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, David Hildenbrand <david@...hat.com>
Subject: Re: [RFC PATCH 3/3] fb_defio: do not use deprecated page->mapping,
 index fields

On Wed, Jan 08, 2025 at 04:18:42PM +0000, Lorenzo Stoakes wrote:
> @@ -280,7 +269,10 @@ static void fb_deferred_io_work(struct work_struct *work)
>  		struct folio *folio = page_folio(pageref->page);
>  
>  		folio_lock(folio);
> -		folio_mkclean(folio);
> +		rmap_wrprotect_file_page(fbdefio->mapping,
> +					 pageref->offset >> PAGE_SHIFT,
> +					 compound_nr(pageref->page),
> +					 page_to_pfn(pageref->page));
>  		folio_unlock(folio);

Why do we need to lock the folio?  (since this isn't necessarily a
folio)  Also, do we need compound_nr() here?  I _think_ for defio,
the number of pages allocated per object are fixed, so this should be
an fbdefio->nr_pages field?

(something that's always troubled me about compound_nr() is that it
returns 1 for tail pages and the number you actually expect for head
pages)