linux-kernel - Re: [patch 5/6] ps3: BD/DVD/CD-ROM Storage Driver

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: <1184623415.3447.48.camel@localhost.localdomain>
Date:	Mon, 16 Jul 2007 17:03:34 -0500
From:	James Bottomley <James.Bottomley@...elEye.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	Jens Axboe <jens.axboe@...cle.com>, Arnd Bergmann <arnd@...db.de>,
	linux-scsi@...r.kernel.org,
	Linux Kernel Development <linux-kernel@...r.kernel.org>,
	Alessandro Rubini <rubini@...ion.unipv.it>,
	Linux/PPC Development <linuxppc-dev@...abs.org>,
	Paul Mackerras <paulus@...ba.org>,
	Geert Uytterhoeven <Geert.Uytterhoeven@...ycom.com>
Subject: Re: [patch 5/6] ps3: BD/DVD/CD-ROM Storage Driver

On Tue, 2007-07-17 at 07:49 +1000, Benjamin Herrenschmidt wrote:
> > No ... that was the point of flush_kernel_dcache_page().  The page in
> > question is page cache backed and contains user mappings.  However, the
> > block layer has already done a flush_dcache_page() in get_user_pages()
> > and the user shouldn't be touching memory under I/O (unless they want
> > self induced aliasing problems) so we're free to assume all the user
> > cachelines are purged, hence all we have to do is flush the kernel alias
> > to bring the page up to date and make the users see it correctly.
> 
> The block layer will have done that even in the swap-out path ? (Just
> asking... I'm not very familiar with the block layer)

Er ... not really, this is the I/O path for user initiated I/O.  The
page out path, by definition, can't have any extant user mappings.  For
page out, the relevant page is flushed before its mapping is detached,
and then it can be paged to the backing store (or for anonymous pages to
the swap device) when no mappings remain.

James


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/