From: Andrew Morton <akpm@linux-foundation.org>
To: Ming Lei <ming.lei@canonical.com>
Cc: linux-kernel@vger.kernel.org,
Russell King - ARM Linux <linux@arm.linux.org.uk>,
linux-arm-kernel@lists.infradead.org,
Simon Baatz <gmbnomis@gmail.com>,
Will Deacon <will.deacon@arm.com>,
Aaro Koskinen <aaro.koskinen@iki.fi>,
Catalin Marinas <catalin.marinas@arm.com>,
FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>,
Tejun Heo <tj@kernel.org>,
"James E.J. Bottomley" <JBottomley@parallels.com>,
Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCH] lib/scatterlist.c: don't flush_kernel_dcache_page on slab page
Date: Thu, 31 Oct 2013 15:27:45 -0700 [thread overview]
Message-ID: <20131031152745.821d2b5dbe93e2ca69d45264@linux-foundation.org> (raw)
In-Reply-To: <1382977205-26268-1-git-send-email-ming.lei@canonical.com>
On Tue, 29 Oct 2013 00:20:05 +0800 Ming Lei <ming.lei@canonical.com> wrote:
> Commit b1adaf65ba03([SCSI] block: add sg buffer copy helper functions)
> introduces two sg buffer copy helpers, and calls flush_kernel_dcache_page()
> on pages in SG list after these pages are written to.
>
> Unfortunately, the commit may introduce a potential bug:
>
> - Before sending some SCSI commands, kmalloc() buffer may be
> passed to block layper, so flush_kernel_dcache_page() can
> see a slab page finally
>
> - According to cachetlb.txt, flush_kernel_dcache_page() is
> only called on "a user page", which surely can't be a slab page.
>
> - ARCH's implementation of flush_kernel_dcache_page() may
> use page mapping information to do optimization so page_mapping()
> will see the slab page, then VM_BUG_ON() is triggered.
>
> Aaro Koskinen reported the bug on ARM/kirkwood when DEBUG_VM is enabled,
> and this patch fixes the bug by adding test of '!PageSlab(miter->page)'
> before calling flush_kernel_dcache_page().
We should work out which kernel(s) need this patch. b1adaf65ba03 was
merged in 2008, so presumably some more recent patch has exposed the
problem, but I don't know what one that was.
Help me out here?
next prev parent reply other threads:[~2013-10-31 22:27 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-28 16:20 Ming Lei
2013-10-29 10:51 ` Catalin Marinas
2013-10-29 12:57 ` Simon Baatz
2013-10-31 22:27 ` Andrew Morton [this message]
2013-10-31 22:44 ` Russell King - ARM Linux
2013-10-31 22:49 ` Aaro Koskinen
2013-10-31 22:54 ` Andrew Morton
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