Re: Null pointer oops

[Larkin Lowrey <llowrey@nuclearwinter.com>]

My swap is an LVM LV on top of a raid10 backed bcache device. I have had
a few oopses in recent months but have not been able to pin down the
cause. I have begun to suspect that the swap may be involved. The SSDs
in that raid10 are junky OCZ Agility3s. They seem to have a reputation
for periodic freezes or long pauses. Could it be that the kernel wanted
to write to the swap but couldn't because the SSDs were in a long pause
and that caused mempool_alloc to return null which then blew up the world?

Is there any reason not to put swap on top of a bcache device?

--Larkin

On 8/13/2014 4:25 PM, Slava Pestov wrote:
> Indeed it looks like iter is NULL. I see the bug is still present in
> the latest dev branch. The problem is that we're not checking the
> return value of mempoool_alloc(), which may be NULL if we pass
> GFP_NOWAIT.
>
> On Wed, Aug 13, 2014 at 2:21 PM, Larkin Lowrey
> <llowrey@nuclearwinter.com> wrote:
>> Here's the dissassembly of bch_btree_node_read_done. The offending line
>> is 207 and the instruction is at offset 76.
>>
>> --Larkin
>>
>> 199     void bch_btree_node_read_done(struct btree *b)
>> 200     {
>>    0x00000000000065b0 <+0>:     callq  0x65b5 <bch_btree_node_read_done+5>
>>    0x00000000000065b5 <+5>:     push   %rbp
>>    0x00000000000065b8 <+8>:     mov    %rsp,%rbp
>>    0x00000000000065bb <+11>:    push   %r15
>>    0x00000000000065bd <+13>:    push   %r14
>>    0x00000000000065bf <+15>:    push   %r13
>>    0x00000000000065c1 <+17>:    push   %r12
>>    0x00000000000065c3 <+19>:    mov    %rdi,%r12
>>    0x00000000000065c6 <+22>:    push   %rbx
>>
>> 201             const char *err = "bad btree header";
>>    0x0000000000006800 <+592>:   mov    $0x0,%rdx
>>
>> 202             struct bset *i = btree_bset_first(b);
>> 203             struct btree_iter *iter;
>> 204
>> 205             iter = mempool_alloc(b->c->fill_iter, GFP_NOWAIT);
>>    0x00000000000065b6 <+6>:     xor    %esi,%esi
>>    0x00000000000065c7 <+23>:    mov    0x80(%rdi),%rax
>>    0x00000000000065d5 <+37>:    mov    0xcb58(%rax),%rdi
>>    0x00000000000065dc <+44>:    callq  0x65e1 <bch_btree_node_read_done+49>
>>    0x00000000000065e9 <+57>:    mov    %rax,%r13
>>
>> 206             iter->size = b->c->sb.bucket_size / b->c->sb.block_size;
>>    0x00000000000065e1 <+49>:    mov    0x80(%r12),%rsi
>>    0x00000000000065ec <+60>:    xor    %edx,%edx
>>    0x00000000000065ee <+62>:    movzwl 0x432(%rsi),%eax
>>    0x00000000000065f5 <+69>:    divw   0x430(%rsi)
>>    0x0000000000006604 <+84>:    movzwl %ax,%eax
>>    0x0000000000006607 <+87>:    mov    %rax,0x0(%r13)
>>
>> 207             iter->used = 0;
>>    0x00000000000065fc <+76>:    movq   $0x0,0x8(%r13)
>>
>> 208
>> 209     #ifdef CONFIG_BCACHE_DEBUG
>> 210             iter->b = &b->keys;
>> 211     #endif
>> 212
>> 213             if (!i->seq)
>>    0x000000000000660b <+91>:    mov    0x10(%rbx),%rax
>>    0x000000000000660f <+95>:    test   %rax,%rax
>>    0x0000000000006612 <+98>:    je     0x6800 <bch_btree_node_read_done+592>
>>
>> 214                     goto err;
>> 215
>> 216             for (;
>>    0x000000000000664d <+157>:   cmp    %r9d,%ecx
>>    0x0000000000006650 <+160>:   jae    0x6882 <bch_btree_node_read_done+722>
>>    0x0000000000006744 <+404>:   cmp    %r9d,%r10d
>>    0x0000000000006747 <+407>:   jae    0x6898 <bch_btree_node_read_done+744>
>>
>> 217                  b->written < btree_blocks(b) && i->seq ==
>> b->keys.set[0].data->seq;
>>    0x0000000000006618 <+104>:   mov    0x80(%r12),%rsi
>>    0x0000000000006625 <+117>:   movzwl 0xc0(%r12),%edi
>>    0x000000000000662e <+126>:   mov    0x108(%r12),%r8
>>    0x0000000000006636 <+134>:   movzwl 0xde2(%rsi),%ecx
>>    0x0000000000006644 <+148>:   mov    %rdx,%r9
>>    0x0000000000006647 <+151>:   shr    %cl,%r9
>>    0x000000000000664a <+154>:   movzwl %di,%ecx
>>    0x0000000000006656 <+166>:   cmp    0x10(%r8),%rax
>>    0x000000000000665a <+170>:   jne    0x6882 <bch_btree_node_read_done+722>
>>    0x000000000000670f <+351>:   mov    %rdx,%r9
>>    0x000000000000672a <+378>:   movzwl 0xde2(%rsi),%ecx
>>    0x0000000000006738 <+392>:   shr    %cl,%r9
>>    0x000000000000674d <+413>:   mov    0x10(%r8),%rcx
>>    0x0000000000006751 <+417>:   cmp    %rcx,0x10(%rbx)
>>    0x0000000000006755 <+421>:   jne    0x6898 <bch_btree_node_read_done+744>
>>    0x0000000000006892 <+738>:   add    %r8,%rbx
>>    0x0000000000006895 <+741>:   nopl   (%rax)
>>
>> 218                  i = write_block(b)) {
>> 219                     err = "unsupported bset version";
>>    0x00000000000069c0 <+1040>:  mov    $0x0,%rdx
>>    0x00000000000069c7 <+1047>:  jmpq   0x6807 <bch_btree_node_read_done+599>
>>    0x00000000000069cc <+1052>:  nopl   0x0(%rax)
>>
>> 220                     if (i->version > BCACHE_BSET_VERSION)
>>    0x0000000000006660 <+176>:   mov    0x18(%rbx),%r10d
>>    0x0000000000006664 <+180>:   cmp    $0x1,%r10d
>>    0x0000000000006668 <+184>:   ja     0x69c0
>> <bch_btree_node_read_done+1040>
>>    0x000000000000666e <+190>:   movzwl 0x430(%rsi),%r11d
>>    0x0000000000006676 <+198>:   jmpq   0x6769 <bch_btree_node_read_done+441>
>>    0x000000000000667b <+203>:   nopl   0x0(%rax,%rax,1)
>>    0x000000000000675b <+427>:   mov    0x18(%rbx),%r10d
>>    0x000000000000675f <+431>:   cmp    $0x1,%r10d
>>    0x0000000000006763 <+435>:   ja     0x69c0
>> <bch_btree_node_read_done+1040>
>>
>> 221                             goto err;
>> 222
>> 223                     err = "bad btree header";
>> 224                     if (b->written + set_blocks(i, block_bytes(b->c)) >
>>    0x0000000000006769 <+441>:   mov    0x1c(%rbx),%eax
>>    0x000000000000676c <+444>:   mov    %r11,%rcx
>>    0x000000000000676f <+447>:   xor    %edx,%edx
>>    0x0000000000006771 <+449>:   shl    $0x9,%rcx
>>    0x0000000000006775 <+453>:   movzwl %di,%edi
>>    0x0000000000006778 <+456>:   mov    %r9d,%r9d
>>    0x000000000000677b <+459>:   and    $0x1fffe00,%ecx
>>    0x0000000000006781 <+465>:   lea    0x20(,%rax,8),%r8
>>    0x0000000000006789 <+473>:   lea    -0x1(%r8,%rcx,1),%rax
>>    0x000000000000678e <+478>:   div    %rcx
>>    0x0000000000006791 <+481>:   add    %rdi,%rax
>>    0x0000000000006794 <+484>:   cmp    %r9,%rax
>>    0x0000000000006797 <+487>:   ja     0x6800 <bch_btree_node_read_done+592>
>>
>> 225                         btree_blocks(b))
>> 226                             goto err;
>> 227
>> 228                     err = "bad magic";
>>    0x00000000000069d0 <+1056>:  mov    $0x0,%rdx
>>    0x00000000000069d7 <+1063>:  jmpq   0x6807 <bch_btree_node_read_done+599>
>>    0x00000000000069dc <+1068>:  nopl   0x0(%rax)
>>
>> 229                     if (i->magic != bset_magic(&b->c->sb))
>>    0x00000000000067aa <+506>:   cmp    %rax,0x8(%rbx)
>>    0x00000000000067ae <+510>:   jne    0x69d0
>> <bch_btree_node_read_done+1056>
>>
>> 230                             goto err;
>> 231
>> 232                     err = "bad checksum";
>>    0x00000000000067df <+559>:   mov    $0x0,%rdx
>>    0x00000000000067e6 <+566>:   jmp    0x6807 <bch_btree_node_read_done+599>
>>    0x00000000000067e8 <+568>:   nopl   0x0(%rax,%rax,1)
>>    0x00000000000067f0 <+576>:   mov    0x1c(%rbx),%eax
>>    0x00000000000067f3 <+579>:   jmpq   0x66bf <bch_btree_node_read_done+271>
>>    0x00000000000067f8 <+584>:   nopl   0x0(%rax,%rax,1)
>>
>> 233                     switch (i->version) {
>>    0x00000000000067b4 <+516>:   cmp    $0x1,%r10d
>>    0x00000000000067bb <+523>:   je     0x6680 <bch_btree_node_read_done+208>
>>
>> 234                     case 0:
>> 235                             if (i->csum != csum_set(i))
>>    0x00000000000067c1 <+529>:   lea    0x20(%rbx),%r14
>>    0x00000000000067c5 <+533>:   lea    0x8(%rbx),%rdi
>>    0x00000000000067ce <+542>:   sub    %rdi,%rsi
>>    0x00000000000067d1 <+545>:   callq  0x67d6 <bch_btree_node_read_done+550>
>>    0x00000000000067d6 <+550>:   cmp    %rax,%r15
>>    0x00000000000067d9 <+553>:   je     0x66a6 <bch_btree_node_read_done+246>
>> 236                                     goto err;
>> 237                             break;
>> 238                     case BCACHE_BSET_VERSION:
>> 239                             if (i->csum != btree_csum_set(b, i))
>>    0x000000000000669d <+237>:   cmp    %rax,%r15
>>    0x00000000000066a0 <+240>:   jne    0x67df <bch_btree_node_read_done+559>
>>    0x00000000000067b8 <+520>:   mov    (%rbx),%r15
>>
>> 240                                     goto err;
>> 241                             break;
>> 242                     }
>> 243
>> 244                     err = "empty set";
>>    0x00000000000069e0 <+1072>:  mov    $0x0,%rdx
>>    0x00000000000069e7 <+1079>:  jmpq   0x6807 <bch_btree_node_read_done+599>
>>
>> 245                     if (i != b->keys.set[0].data && !i->keys)
>>    0x00000000000066a6 <+246>:   cmp    %rbx,0x108(%r12)
>>    0x00000000000066ae <+254>:   je     0x67f0 <bch_btree_node_read_done+576>
>>    0x00000000000066b4 <+260>:   mov    0x1c(%rbx),%eax
>>    0x00000000000066b7 <+263>:   test   %eax,%eax
>>    0x00000000000066b9 <+265>:   je     0x69e0
>> <bch_btree_node_read_done+1072>
>>
>> 246                             goto err;
>> 247
>> 248                     bch_btree_iter_push(iter, i->start,
>> bset_bkey_last(i));
>>    0x00000000000066c3 <+275>:   mov    %r14,%rsi
>>    0x00000000000066c6 <+278>:   mov    %r13,%rdi
>>    0x00000000000066c9 <+281>:   callq  0x66ce <bch_btree_node_read_done+286>
>>
>> 249
>> 250                     b->written += set_blocks(i, block_bytes(b->c));
>>    0x00000000000066ce <+286>:   mov    0x80(%r12),%rsi
>>    0x00000000000066d6 <+294>:   mov    0x1c(%rbx),%eax
>>    0x00000000000066d9 <+297>:   xor    %edx,%edx
>>    0x00000000000066e3 <+307>:   movzwl 0x430(%rsi),%ecx
>>    0x00000000000066ea <+314>:   shl    $0x9,%ecx
>>    0x00000000000066ed <+317>:   movslq %ecx,%rcx
>>    0x00000000000066f0 <+320>:   lea    0x1f(%rcx,%rax,8),%rax
>>    0x00000000000066f5 <+325>:   div    %rcx
>>    0x0000000000006704 <+340>:   mov    %eax,%edi
>>    0x0000000000006706 <+342>:   add    0xc0(%r12),%di
>>    0x0000000000006712 <+354>:   mov    %di,0xc0(%r12)
>>
>> 251             }
>> 252
>> 253             err = "corrupted btree";
>>    0x00000000000069b0 <+1024>:  mov    $0x0,%rdx
>>    0x00000000000069b7 <+1031>:  jmpq   0x6807 <bch_btree_node_read_done+599>
>>    0x00000000000069bc <+1036>:  nopl   0x0(%rax)
>>
>> 254             for (i = write_block(b);
>>    0x00000000000068a1 <+753>:   cmp    %rdx,%rcx
>>    0x00000000000068a4 <+756>:   jae    0x68e5 <bch_btree_node_read_done+821>
>>    0x00000000000068e0 <+816>:   cmp    %rdx,%rcx
>>    0x00000000000068e3 <+819>:   jb     0x68c8 <bch_btree_node_read_done+792>
>>
>> 255                  bset_sector_offset(&b->keys, i) < KEY_SIZE(&b->key);
>> 256                  i = ((void *) i) + block_bytes(b->c))
>>    0x00000000000068d7 <+807>:   mov    %rcx,%rbx
>>    0x00000000000068da <+810>:   sub    %r8d,%ecx
>>
>> 257                     if (i->seq == b->keys.set[0].data->seq)
>>    0x00000000000068a6 <+758>:   mov    0x10(%r8),%rdi
>>    0x00000000000068aa <+762>:   cmp    %rdi,0x10(%rbx)
>>    0x00000000000068ae <+766>:   je     0x69b0
>> <bch_btree_node_read_done+1024>
>>    0x00000000000068b4 <+772>:   cltq
>>    0x00000000000068b6 <+774>:   mov    %rax,%r9
>>    0x00000000000068b9 <+777>:   lea    (%rbx,%rax,1),%rcx
>>    0x00000000000068bd <+781>:   neg    %r9
>>    0x00000000000068c0 <+784>:   jmp    0x68d7 <bch_btree_node_read_done+807>
>>    0x00000000000068c2 <+786>:   nopw   0x0(%rax,%rax,1)
>>    0x00000000000068c8 <+792>:   lea    (%rbx,%rax,1),%rcx
>>    0x00000000000068cc <+796>:   cmp    0x10(%rcx,%r9,1),%rdi
>>    0x00000000000068d1 <+801>:   je     0x69b0
>> <bch_btree_node_read_done+1024>
>>
>> 258                             goto err;
>> 259
>> 260             bch_btree_sort_and_fix_extents(&b->keys, iter, &b->c->sort);
>>    0x00000000000068e5 <+821>:   lea    0xc8(%r12),%r14
>>    0x00000000000068ed <+829>:   lea    0xcb60(%rsi),%rdx
>>    0x00000000000068f4 <+836>:   mov    %r13,%rsi
>>    0x00000000000068f7 <+839>:   mov    %r14,%rdi
>>    0x00000000000068fa <+842>:   callq  0x68ff <bch_btree_node_read_done+847>
>>
>> 261
>> 262             i = b->keys.set[0].data;
>>    0x0000000000006907 <+855>:   mov    0x108(%r12),%rbx
>>
>> 263             err = "short btree key";
>>    0x00000000000069ec <+1084>:  mov    $0x0,%rdx
>>    0x00000000000069f3 <+1091>:  jmpq   0x6807 <bch_btree_node_read_done+599>
>>
>> 264             if (b->keys.set[0].size &&
>>    0x00000000000068ff <+847>:   mov    0xe0(%r12),%eax
>>    0x0000000000006914 <+868>:   test   %eax,%eax
>>    0x0000000000006916 <+870>:   je     0x694d <bch_btree_node_read_done+925>
>>    0x0000000000006944 <+916>:   test   %rax,%rax
>>    0x0000000000006947 <+919>:   js     0x69ec
>> <bch_btree_node_read_done+1084>
>>
>> 265                 bkey_cmp(&b->key, &b->keys.set[0].end) < 0)
>> 266                     goto err;
>> 267
>> 268             if (b->written < btree_blocks(b))
>>    0x000000000000694d <+925>:   mov    0x80(%r12),%rax
>>    0x0000000000006955 <+933>:   movzwl 0xc0(%r12),%esi
>>    0x0000000000006965 <+949>:   movzwl 0xde2(%rax),%ecx
>>    0x000000000000696c <+956>:   shr    %cl,%rdx
>>    0x000000000000696f <+959>:   cmp    %edx,%esi
>>    0x0000000000006971 <+961>:   jae    0x6868 <bch_btree_node_read_done+696>
>>
>> 269                     bch_bset_init_next(&b->keys, write_block(b),
>>    0x000000000000698f <+991>:   mov    %r14,%rdi
>>    0x000000000000699e <+1006>:  callq  0x69a3
>> <bch_btree_node_read_done+1011>
>>    0x00000000000069a3 <+1011>:  mov    0x80(%r12),%rax
>>    0x00000000000069ab <+1019>:  jmpq   0x6868 <bch_btree_node_read_done+696>
>>
>> 270                                        bset_magic(&b->c->sb));
>> 271     out:
>> 272             mempool_free(iter, b->c->fill_iter);
>>    0x0000000000006868 <+696>:   mov    0xcb58(%rax),%rsi
>>    0x000000000000686f <+703>:   mov    %r13,%rdi
>>    0x0000000000006872 <+706>:   callq  0x6877 <bch_btree_node_read_done+711>
>>
>> 273             return;
>> 274     err:
>> 275             set_btree_node_io_error(b);
>> 276             bch_cache_set_error(b->c, "%s at bucket %zu, block %u,
>> %u keys",
>>    0x0000000000006829 <+633>:   mov    0x1c(%rbx),%r9d
>>    0x000000000000684a <+666>:   mov    %esi,%ecx
>>    0x000000000000684c <+668>:   mov    $0x0,%rsi
>>    0x0000000000006853 <+675>:   shr    %cl,%r8d
>>    0x0000000000006856 <+678>:   mov    %rax,%rcx
>>    0x0000000000006859 <+681>:   xor    %eax,%eax
>>    0x000000000000685b <+683>:   callq  0x6860 <bch_btree_node_read_done+688>
>>    0x0000000000006860 <+688>:   mov    0x80(%r12),%rax
>>
>> 277                                 err, PTR_BUCKET_NR(b->c, &b->key, 0),
>> 278                                 bset_block_offset(b, i), i->keys);
>> 279             goto out;
>> 280     }
>>    0x0000000000006877 <+711>:   pop    %rbx
>>    0x0000000000006878 <+712>:   pop    %r12
>>    0x000000000000687a <+714>:   pop    %r13
>>    0x000000000000687c <+716>:   pop    %r14
>>    0x000000000000687e <+718>:   pop    %r15
>>    0x0000000000006880 <+720>:   pop    %rbp
>>    0x0000000000006881 <+721>:   retq
>>    0x0000000000006882 <+722>:   movzwl 0x430(%rsi),%eax
>>    0x0000000000006889 <+729>:   shl    $0x9,%eax
>>    0x000000000000688c <+732>:   imul   %eax,%ecx
>>    0x000000000000688f <+735>:   movslq %ecx,%rbx
>>
>>
>> On 8/13/2014 1:45 PM, Slava Pestov wrote:
>>> Can you post the disassembly of the function?
>>>
>>> On Wed, Aug 13, 2014 at 11:35 AM, Larkin Lowrey
>>> <llowrey@nuclearwinter.com> wrote:
>>>> Thanks. Trying gdb helped me find the answer. I needed to install the
>>>> kernel-debuginfo-3.15.8-200.fc20.x86_64  package via yum.
>>>>
>>>> From addr2line:
>>>>> bch_btree_node_read_done+0x4c
>>>>> drivers/md/bcache/btree.c:207
>>>> Here'a a snippet from gdb:
>>>>
>>>>> (gdb) list *(bch_btree_node_read_done+0x4c)
>>>>> 0x65fc is in bch_btree_node_read_done (drivers/md/bcache/btree.c:207).
>>>>> 202             struct bset *i = btree_bset_first(b);
>>>>> 203             struct btree_iter *iter;
>>>>> 204
>>>>> 205             iter = mempool_alloc(b->c->fill_iter, GFP_NOWAIT);
>>>>> 206             iter->size = b->c->sb.bucket_size / b->c->sb.block_size;
>>>>> 207             iter->used = 0;
>>>>> 208
>>>>> 209     #ifdef CONFIG_BCACHE_DEBUG
>>>>> 210             iter->b = &b->keys;
>>>>> 211     #endif
>>>> This doesn't make any sense to me. If iter was null I would expect line
>>>> 206 to blow up first.
>>>>
>>>> --Larkin
>>>>
>>>> On 8/13/2014 12:41 PM, Slava Pestov wrote:
>>>>> You can try to use gdb:
>>>>>
>>>>> gdb /lib/modules/.../foo.ko
>>>>>
>>>>> list *(bch_btree_node_read_done+0x4c)
>>>>>
>>>>>
>>>>> On Wed, Aug 13, 2014 at 9:40 AM, Larkin Lowrey
>>>>> <llowrey@nuclearwinter.com> wrote:
>>>>>> This is making be feel very dumb. I've googled extensively but can't
>>>>>> figure out how to run addr2line for a module.
>>>>>>
>>>>>> I'm running Fedora 20 and the kernel did not have debugging symbols. I
>>>>>> downloaded the version with symbols but I don't know if the addresses
>>>>>> are going to be the same. Bcache is a module for me and that's where
>>>>>> things get tricky. Do you have any tips?
>>>>>>
>>>>>> --Larkin
>>>>>>
>>>>>> On 8/13/2014 12:04 AM, Kent Overstreet wrote:
>>>>>>> Any chance you could do an addr2line and get me the exact line where
>>>>>>> it happened?
>>>>>>>
>>>>>>> On Aug 12, 2014 10:02 PM, "Larkin Lowrey" <llowrey@nuclearwinter.com
>>>>>>> <mailto:llowrey@nuclearwinter.com>> wrote:
>>>>>>>
>>>>>>>     I got an oops while doing some heavy I/O. I have an md raid10 cache
>>>>>>>     device (4 SSDs) and 3 md raid5/6 backing devices. This setup has been
>>>>>>>     well behaved for about 6 months.
>>>>>>>
>>>>>>>     If this isn't a known issue is there anything I can do to provide more
>>>>>>>     useful information?
>>>>>>>
>>>>>>>     I'm running kernel 3.15.8-200.fc20.x86_64.
>>>>>>>
>>>>>>>     [210884.047249] BUG: unable to handle kernel NULL pointer
>>>>>>>     dereference at 0000000000000008
>>>>>>>     [210884.055605] IP: [<ffffffffa01625fc>]
>>>>>>>     bch_btree_node_read_done+0x4c/0x450 [bcache]
>>>>>>>     [210884.063723] PGD 0
>>>>>>>     [210884.066053] Oops: 0002 [#1] SMP
>>>>>>>     [210884.069610] Modules linked in: lp parport binfmt_misc
>>>>>>>     ipt_MASQUERADE iptable_nat nf_nat_ipv4 nf_nat xt_CHECKSUM
>>>>>>>     iptable_mangle tun bridge stp llc xt_multiport ebtable_nat
>>>>>>>     ebtables hwmon_vid ip6t_REJECT nf_conntrack_ipv6 nf_conntrack_ipv4
>>>>>>>     nf_defrag_ipv6 nf_defrag_ipv4 ip6table_filter xt_conntrack
>>>>>>>     ip6_tables nf_conntrack keyspan ezusb kvm_amd kvm crct10dif_pclmul
>>>>>>>     crc32_pclmul crc32c_intel ghash_clmulni_intel microcode serio_raw
>>>>>>>     amd64_edac_mod edac_core fam15h_power k10temp edac_mce_amd
>>>>>>>     sp5100_tco i2c_piix4 igb ptp pps_core dca shpchp acpi_cpufreq
>>>>>>>     btrfs bcache raid456 async_raid6_recov async_memcpy async_pq
>>>>>>>     async_xor async_tx xor raid6_pq raid10 i2c_algo_bit drm_kms_helper
>>>>>>>     ttm drm i2c_core mpt2sas mvsas libsas raid_class
>>>>>>>     scsi_transport_sas cpufreq_stats
>>>>>>>     [210884.140704] CPU: 5 PID: 11188 Comm: kworker/5:1 Not tainted
>>>>>>>     3.15.8-200.fc20.x86_64 #1
>>>>>>>     [210884.149069] Hardware name:  /H8DG6/H8DGi, BIOS 3.0a       07/2
>>>>>>>     [210884.155280] Workqueue: bcache cache_lookup [bcache]
>>>>>>>     [210884.160531] task: ffff880218633160 ti: ffff8800217b8000
>>>>>>>     task.ti: ffff8800217b8000
>>>>>>>     [210884.168502] RIP: 0010:[<ffffffffa01625fc>]
>>>>>>>      [<ffffffffa01625fc>] bch_btree_node_read_done+0x4c/0x450 [bcache]
>>>>>>>     [210884.179105] RSP: 0000:ffff8800217bbbe8  EFLAGS: 00010212
>>>>>>>     [210884.184806] RAX: 0000000000000400 RBX: ffff880245ec0000 RCX:
>>>>>>>     0000000000000000
>>>>>>>     [210884.192480] RDX: 0000000000000000 RSI: ffff880418380000 RDI:
>>>>>>>     0000000000000246
>>>>>>>     [210884.200075] RBP: ffff8800217bbc10 R08: 0000000000000000 R09:
>>>>>>>     0000000000000f6b
>>>>>>>     [210884.207738] R10: 0000000000000000 R11: 0000000000000400 R12:
>>>>>>>     ffff880413d06c00
>>>>>>>     [210884.215391] R13: 0000000000000000 R14: ffff8800217bbc20 R15:
>>>>>>>     ffff880413d06c00
>>>>>>>     [210884.222961] FS:  00007f73bacd6880(0000)
>>>>>>>     GS:ffff88021fd40000(0000) knlGS:0000000000000000
>>>>>>>     [210884.231516] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
>>>>>>>     [210884.237557] CR2: 0000000000000008 CR3: 0000000001c11000 CR4:
>>>>>>>     00000000000407e0
>>>>>>>     [210884.245131] Stack:
>>>>>>>     [210884.247395]  ffff880274f4d020 ffff880413d06c00
>>>>>>>     0000bfcc44a463f8 ffff8800217bbc20
>>>>>>>     [210884.255337]  ffff880413d06c00 ffff8800217bbc78
>>>>>>>     ffffffffa0162b68 0000000000000000
>>>>>>>     [210884.263256]  ffff880218633160 0000000000000000
>>>>>>>     0000000000000000 0000000000000000
>>>>>>>     [210884.271234] Call Trace:
>>>>>>>     [210884.273985]  [<ffffffffa0162b68>]
>>>>>>>     bch_btree_node_read+0x168/0x190 [bcache]
>>>>>>>     [210884.281258]  [<ffffffffa0163f69>]
>>>>>>>     bch_btree_node_get+0x169/0x290 [bcache]
>>>>>>>     [210884.288377]  [<ffffffffa01642f5>]
>>>>>>>     bch_btree_map_keys_recurse+0xd5/0x1d0 [bcache]
>>>>>>>     [210884.296311]  [<ffffffffa016dcb0>] ?
>>>>>>>     cached_dev_congested+0x180/0x180 [bcache]
>>>>>>>     [210884.303953]  [<ffffffff8135b204>] ?
>>>>>>>     call_rwsem_down_read_failed+0x14/0x30
>>>>>>>     [210884.311158]  [<ffffffffa01673f7>]
>>>>>>>     bch_btree_map_keys+0x127/0x150 [bcache]
>>>>>>>     [210884.318273]  [<ffffffffa016dcb0>] ?
>>>>>>>     cached_dev_congested+0x180/0x180 [bcache]
>>>>>>>     [210884.325826]  [<ffffffffa016e7f5>] cache_lookup+0xf5/0x1f0 [bcache]
>>>>>>>     [210884.332325]  [<ffffffff810a4af6>] process_one_work+0x176/0x430
>>>>>>>     [210884.338427]  [<ffffffff810a578b>] worker_thread+0x11b/0x3a0
>>>>>>>     [210884.344282]  [<ffffffff810a5670>] ? rescuer_thread+0x3b0/0x3b0
>>>>>>>     [210884.350447]  [<ffffffff810ac528>] kthread+0xd8/0xf0
>>>>>>>     [210884.355615]  [<ffffffff810ac450>] ? insert_kthread_work+0x40/0x40
>>>>>>>     [210884.362017]  [<ffffffff816ff93c>] ret_from_fork+0x7c/0xb0
>>>>>>>     [210884.367756]  [<ffffffff810ac450>] ? insert_kthread_work+0x40/0x40
>>>>>>>     [210884.374234] Code: 08 01 00 00 48 8b b8 58 cb 00 00 e8 bf 25 01
>>>>>>>     e1 49 8b b4 24 80 00 00 00 49 89 c5 31 d2 0f b7 86 32 04 00 00 66
>>>>>>>     f7 b6 30 04 00 00 <49> c7 45 08 00 00 00 00 0f b7 c0 49 89 45 00
>>>>>>>     48 8b 43 10 48 85
>>>>>>>     [210884.395405] RIP  [<ffffffffa01625fc>]
>>>>>>>     bch_btree_node_read_done+0x4c/0x450 [bcache]
>>>>>>>     [210884.403389]  RSP <ffff8800217bbbe8>
>>>>>>>     [210884.407171] CR2: 0000000000000008
>>>>>>>     [210884.411233] ---[ end trace 0064e6abfd068c85 ]---
>>>>>>>     [210884.416352] BUG: unable to handle kernel paging request at
>>>>>>>     ffffffffffffffd8
>>>>>>>     [210884.423871] IP: [<ffffffff810acb10>] kthread_data+0x10/0x20
>>>>>>>     [210884.429915] PGD 1c14067 PUD 1c16067 PMD 0
>>>>>>>
>>>>>>>     --Larkin
>>>>>>>
>>>>>>>     --
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>>>>>>>     linux-bcache" in
>>>>>>>     the body of a message to majordomo@vger.kernel.org
>>>>>>>     <mailto:majordomo@vger.kernel.org>
>>>>>>>     More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>>>>>
>>>>>> --
>>>>>> To unsubscribe from this list: send the line "unsubscribe linux-bcache" in
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