Messages in this thread | | | Date | Tue, 29 Oct 2013 13:57:37 +0100 | From | Simon Baatz <> | Subject | Re: [PATCH] lib/scatterlist.c: don't flush_kernel_dcache_page on slab page |
| |
On Tue, Oct 29, 2013 at 12:20:05AM +0800, Ming Lei 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(). > > Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi> > Cc: Russell King - ARM Linux <linux@arm.linux.org.uk> > Cc: linux-arm-kernel@lists.infradead.org > Cc: Simon Baatz <gmbnomis@gmail.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Aaro Koskinen <aaro.koskinen@iki.fi> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> > Cc: Tejun Heo <tj@kernel.org> > Cc: "James E.J. Bottomley" <JBottomley@parallels.com> > Cc: Jens Axboe <axboe@kernel.dk> > Signed-off-by: Ming Lei <ming.lei@canonical.com> > --- > lib/scatterlist.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/lib/scatterlist.c b/lib/scatterlist.c > index a685c8a..d16fa29 100644 > --- a/lib/scatterlist.c > +++ b/lib/scatterlist.c > @@ -577,7 +577,8 @@ void sg_miter_stop(struct sg_mapping_iter *miter) > miter->__offset += miter->consumed; > miter->__remaining -= miter->consumed; > > - if (miter->__flags & SG_MITER_TO_SG) > + if ((miter->__flags & SG_MITER_TO_SG) && > + !PageSlab(miter->page)) > flush_kernel_dcache_page(miter->page); > > if (miter->__flags & SG_MITER_ATOMIC) { > -- > 1.7.9.5 >
Tested-by: Simon Baatz <gmbnomis@gmail.com>
on top of 3.12-rc7 on Kirkwood with DEBUG_VM enabled.
- Simon
| |