On Thu, Jul 02, 2015 at 11:25:16AM +0800, Yuanhan Liu wrote: > Hi Shaohua, > > I gave it a quick test(dd if=/dev/zero of=/dev/md0) in a KVM, and > here I met a kernel oops. > > [ 14.768563] BUG: unable to handle kernel NULL pointer dereference at (null) > [ 14.769153] IP: [<c1383b13>] xor_sse_3_pf64+0x67/0x207 > [ 14.769585] *pde = 00000000 > [ 14.769822] Oops: 0000 [#1] SMP > [ 14.770092] Modules linked in: > [ 14.770349] CPU: 0 PID: 2234 Comm: md0_raid5 Not tainted 4.1.0+ #18 > [ 14.770854] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014 > [ 14.771859] task: f62c5e80 ti: f04ec000 task.ti: f04ec000 > [ 14.772287] EIP: 0060:[<c1383b13>] EFLAGS: 00010246 CPU: 0 > [ 14.772327] EIP is at xor_sse_3_pf64+0x67/0x207 > [ 14.772327] EAX: 00000010 EBX: 00000000 ECX: e2a99000 EDX: f48ae000 > [ 14.772327] ESI: f48ae000 EDI: 00000010 EBP: f04edcd8 ESP: f04edccc > [ 14.772327] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 > [ 14.772327] CR0: 80050033 CR2: 00000000 CR3: 22ac5000 CR4: 000006d0 > [ 14.772327] Stack: > [ 14.772327] c1c4d96c 00000000 00000001 f04edcf8 c1382bcf 00000000 00000002 c112d2e5 > [ 14.772327] 00000000 f04edd98 00000002 f04edd30 c138554b f6a2e028 00000001 f6f51b30 > [ 14.772327] 00000002 00000000 f48ae000 f6a2e028 00001000 f04edd40 00000002 00000000 > [ 14.772327] Call Trace: > [ 14.772327] [<c1382bcf>] xor_blocks+0x3a/0x6d > [ 14.772327] [<c112d2e5>] ? page_address+0xb8/0xc0 > [ 14.772327] [<c138554b>] async_xor+0xf3/0x113 > [ 14.772327] [<c186d954>] raid_run_ops+0xf73/0x1025 > [ 14.772327] [<c186d954>] ? raid_run_ops+0xf73/0x1025 > [ 14.772327] [<c16ce8b9>] handle_stripe+0x120/0x199b > [ 14.772327] [<c10c7df4>] ? clockevents_program_event+0xfb/0x118 > [ 14.772327] [<c10c94f7>] ? tick_program_event+0x5f/0x68 > [ 14.772327] [<c10be529>] ? hrtimer_interrupt+0xa3/0x134 > [ 14.772327] [<c16d0366>] handle_active_stripes.isra.37+0x232/0x2b5 > [ 14.772327] [<c16d0701>] raid5d+0x267/0x44c > [ 14.772327] [<c18717e6>] ? schedule_timeout+0x1c/0x14d > [ 14.772327] [<c1872011>] ? _raw_spin_lock_irqsave+0x1f/0x3d > [ 14.772327] [<c16f684a>] md_thread+0x103/0x112 > [ 14.772327] [<c10a3146>] ? wait_woken+0x62/0x62 > [ 14.772327] [<c16f6747>] ? md_wait_for_blocked_rdev+0xda/0xda > [ 14.772327] [<c108d44e>] kthread+0xa4/0xa9 > [ 14.772327] [<c1872401>] ret_from_kernel_thread+0x21/0x30 > [ 14.772327] [<c108d3aa>] ? kthread_create_on_node+0x104/0x104 > > > I dug it a while, and came up with following fix. Does it make sense > to you? > > ---- > diff --git a/crypto/async_tx/async_xor.c b/crypto/async_tx/async_xor.c > index e1bce26..063ac50 100644 > --- a/crypto/async_tx/async_xor.c > +++ b/crypto/async_tx/async_xor.c > @@ -30,6 +30,7 @@ > #include <linux/dma-mapping.h> > #include <linux/raid/xor.h> > #include <linux/async_tx.h> > +#include <linux/highmem.h> > > /* do_async_xor - dma map the pages and perform the xor with an engine */ > static __async_inline struct dma_async_tx_descriptor * > @@ -127,7 +128,7 @@ do_sync_xor(struct page *dest, struct page **src_list, unsigned int offset, > /* convert to buffer pointers */ > for (i = 0; i < src_cnt; i++) > if (src_list[i]) > - srcs[xor_src_cnt++] = page_address(src_list[i]) + offset; > + srcs[xor_src_cnt++] = kmap_atomic(src_list[i]) + offset; > src_cnt = xor_src_cnt; > /* set destination address */ > dest_buf = page_address(dest) + offset; > @@ -140,6 +141,9 @@ do_sync_xor(struct page *dest, struct page **src_list, unsigned int offset, > xor_src_cnt = min(src_cnt, MAX_XOR_BLOCKS); > xor_blocks(xor_src_cnt, len, dest_buf, &srcs[src_off]); > > + for(i = src_off; i < src_off + xor_src_cnt; i++) > + kunmap_atomic(srcs[i]); > + > /* drop completed sources */ > src_cnt -= xor_src_cnt; > src_off += xor_src_cnt; Thanks! This is the side effect of skip_copy, I think. skip_copy isn't enabled by default, so we don't hit it before, while my previous test was done with x86_64. We should see this with skip_copy enabled even without the cache patches. The patch does make sense. There are other async APIs using page_address too: async_raid6_recov.c, async_pq.c, can you please fix them? You can check them with raid6. Thanks, Shaohua -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
