On Fri, 17 Nov 2017 09:23:18 +0800 Miles Chen <miles.chen@xxxxxxxxxxxx> wrote: > On Thu, 2017-11-16 at 16:13 -0800, Andrew Morton wrote: > > On Fri, 17 Nov 2017 06:56:12 +0800 <miles.chen@xxxxxxxxxxxx> wrote: > > > > > From: Miles Chen <miles.chen@xxxxxxxxxxxx> > > > > > > dma-debug reports the following warning: > > > > > > [name:panic&]WARNING: CPU: 3 PID: 298 at kernel-4.4/lib/dma-debug.c:604 > > > debug _dma_assert_idle+0x1a8/0x230() > > > DMA-API: cpu touching an active dma mapped cacheline [cln=0x00000882300] > > > CPU: 3 PID: 298 Comm: vold Tainted: G W O 4.4.22+ #1 > > > Hardware name: MT6739 (DT) > > > Call trace: > > > [<ffffff800808acd0>] dump_backtrace+0x0/0x1d4 > > > [<ffffff800808affc>] show_stack+0x14/0x1c > > > [<ffffff800838019c>] dump_stack+0xa8/0xe0 > > > [<ffffff80080a0594>] warn_slowpath_common+0xf4/0x11c > > > [<ffffff80080a061c>] warn_slowpath_fmt+0x60/0x80 > > > [<ffffff80083afe24>] debug_dma_assert_idle+0x1a8/0x230 > > > [<ffffff80081dca9c>] wp_page_copy.isra.96+0x118/0x520 > > > [<ffffff80081de114>] do_wp_page+0x4fc/0x534 > > > [<ffffff80081e0a14>] handle_mm_fault+0xd4c/0x1310 > > > [<ffffff8008098798>] do_page_fault+0x1c8/0x394 > > > [<ffffff800808231c>] do_mem_abort+0x50/0xec > > > > > > I found that debug_dma_alloc_coherent() and debug_dma_free_coherent() > > > assume that dma_alloc_coherent() always returns a linear address. However > > > it's possible that dma_alloc_coherent() returns a non-linear address. In > > > this case, page_to_pfn(virt_to_page(virt)) will return an incorrect pfn. > > > If the pfn is valid and mapped as a COW page, we will hit the warning when > > > doing wp_page_copy(). > > > > > > Fix this by calculating pfn for linear and non-linear addresses. > > > > > > > It's a shame you didn't Cc Christoph, who was the sole reviewer of the > > earlier version. > > > > And it's a shame you didn't capture the result of that review > > discussion in the v3 changelog. > > > > And it's a shame that you didn't describe how this patch differs from > > earlier versions. > > > I am truly sorry about this. I was not sure if I can submit a patch > based on a linux-next patch, so I submit a new patch based on the latest > mainline kernel again. > > I know how to do this now. I will do it correctly next time. > > Is there anyway to fix this? (send another patch with v3 discussion and > the difference from earlier versions to the commit message). A complete resend is perfectly OK - I will handle the changelog modifications, etc. My point is that the Cc: line was incomplete and that the changelog is missing information, as described above. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
