On Fri, 1 Nov 2013 00:49:27 +0200 Aaro Koskinen <aaro.koski...@iki.fi> wrote:
> Hi, > > On Thu, Oct 31, 2013 at 03:27:45PM -0700, Andrew Morton wrote: > > On Tue, 29 Oct 2013 00:20:05 +0800 Ming Lei <ming....@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? > > On ARM, this problem started to appear after > 1bc39742aab09248169ef9d3727c9def3528b3f3 (ARM: 7755/1: handle user space > mapped pages in flush_kernel_dcache_page) and that was tagged for 3.2+ > stable kernels. > OK, thanks. I added Cc: <sta...@vger.kernel.org> [3.2+] to the changelog. I guess I should get this and a few other things into Linus today, as 3.12 is nigh. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
