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Date:	Wed, 4 May 2011 10:35:59 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jens Axboe <axboe@...nel.dk>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	werner <w.landgraf@...ru>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [block IO crash] Re: 2.6.39-rc5-git2 boot crashs


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> On Tue, May 3, 2011 at 12:08 PM, Ingo Molnar <mingo@...e.hu> wrote:
> >
> > I have no smart ideas straight away - just an observation: i keep testing 
> > CONFIG_X86_ELAN=y on real hardware, and it's enabled in about 4% of my 
> > configs:
> 
> So how often do you do more than just boot?

Not very often - but 'to boot' means a certain amount of filesystem work - and 
so does the 'prepare to boot the next kernel' step.

So i took Werner's .config.zipproblem and modified it to make it bootable: 
removed CONFIG_ROOT_NFS=y and disabled CONFIG_IDE - both of which keep my box 
from booting. I've attached an updated .config.zipproblem2 file: Werner, can 
you confirm that this still fails for you?

So i booted v2.6.39-rc5-254-g5933f2a on an AMD box (which is SMP in fact, so 
should trigger races even faster):

   Kernel 2.6.39-rc5-i486-1sys+ on an i686

and started a couple of such IO-intense loops:

  FILE=bigfile.$RANDOM;
  while sync; do rm -f $FILE; dd if=/dev/urandom of=$FILE bs=1000 count=10000; done &

this creates patterns of high IO combined with periods waiting for IO to flush:

procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 8  0      0 621140   8968 346500    0    0    29   874 1044  135  0 27 71  2  0
 8  0      0 614692   8984 352904    0    0     0     0 2011  658  0 100  0  0  0
 8  0      0 608492   8992 359104    0    0     0     0 2096  709  1 99  0  0  0
 8  0      0 602016   8992 365332    0    0     0     0 2006  651  0 100  0  0  0
 8  0      0 595692   8992 371760    0    0     0     0 2005  647  0 100  0  0  0
 4  5      0 588128   9000 378080    0    0     0 31508 2031  610  0 100  0  0  0
 6  2      0 583168   9068 383664    0    0     4  7532 2256  668  0 91  0  9  0
 8  0      0 586888   9116 380212    0    0     0   456 2073  804  1 100  0  0  0
 5  3      0 620484   9408 346904    0    0     0 14932 2768 1901  0 94  1  6  0
 8  0      0 633656   9576 333392    0    0     0  6180 2369 1232  0 98  0  2  0
 8  0      0 627208   9576 339720    0    0     0     0 2004  650  0 100  0  0  0
 8  0      0 621008   9580 346032    0    0     0     0 2048  680  1 100  0  0  0
 8  0      0 614436   9588 352296    0    0     0     0 2004  657  0 100  0  0  0
 8  0      0 618652   9708 348296    0    0     0 25984 2283  816  0 92  0  7  0
 8  0      0 612424   9708 354576    0    0     0     0 2005  651  0 100  0  0  0
 8  0      0 605976   9716 360892    0    0     0     0 2004  652  0 100  0  0  0
 8  0      0 599652   9716 367208    0    0     0     0 2006  654  0 100  0  0  0
 8  0      0 593204   9720 373528    0    0     0     0 2004  652  0 100  0  0  0
 7  2      0 585764   9728 379852    0    0     0 31612 2038  649  0 100  0  0  0
 8  0      0 590104   9832 376180    0    0     4  7400 2274  920  0 98  0  2  0
 2  6      0 597288  10008 368892    0    0     0  8636 2432 1373  0 95  0  5  0
 8  0      0 627180  10208 339096    0    0     0  4324 2426 1429  0 97  0  2  0
 8  0      0 630404  10284 335480    0    0     0  6408 2202  970  1 97  0  2  0

And indeed, after a couple of minutes testing i triggered this beauty:

BUG: unable to handle kernel NULL pointer dereference at 00000008
IP: [<c14e85c0>] generic_make_request+0x86/0x3f4
*pde = 00000000 
Oops: 0000 [#1] SMP 
last sysfs file: /sys/devices/pci0000:00/0000:00:0a.0/net/eth0/address
Modules linked in:

Pid: 2969, comm: flush-8:0 Not tainted 2.6.39-rc5-i486-1sys+ #122580 System manufacturer System Product Name/A8N-E
EIP: 0060:[<c14e85c0>] EFLAGS: 00010202 CPU: 1
EIP is at generic_make_request+0x86/0x3f4
EAX: 00000000 EBX: f569e280 ECX: f6a00000 EDX: f5528000
ESI: 00000008 EDI: 00000001 EBP: f5fd7c8c ESP: f5fd7c14
 DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
Process flush-8:0 (pid: 2969, ti=f5fd6000 task=f64d0ab0 task.ti=f5fd6000)
Stack:
 f569e280 c10988af f5fd7c84 c1d74030 f6402400 f569e300 00081ddb f569e280
 c10988af f5fd7c84 f64d0ab0 0000007b 0000007b 000000d8 00000008 ffffffc1
 00000000 00000000 00000246 f6a06c80 055c08fe 00000000 c10988af 00000080
Call Trace:
 [<c10988af>] ? mempool_alloc_slab+0x13/0x15
 [<c1d74030>] ? common_interrupt+0x30/0x40
 [<c10988af>] ? mempool_alloc_slab+0x13/0x15
 [<c10988af>] ? mempool_alloc_slab+0x13/0x15
 [<c14e89f9>] submit_bio+0xcb/0xe4
 [<c10a8048>] ? inc_zone_page_state+0xe/0x88
 [<c10ed8b5>] ? bio_init+0x9/0x2e
 [<c10ee05b>] ? bio_alloc_bioset+0x3c/0x9c
 [<c10ea27a>] submit_bh+0xc6/0xe0
 [<c10eb8f3>] __block_write_full_page+0x20a/0x2df
 [<c10ed9d9>] ? bio_put+0x8/0x2c
 [<c10ea9e5>] ? end_buffer_async_read+0xd5/0xd5
 [<c10eba88>] block_write_full_page_endio+0xc0/0xc8
 [<c10ea9e5>] ? end_buffer_async_read+0xd5/0xd5
 [<c10ebaa7>] block_write_full_page+0x17/0x19
 [<c10ea9e5>] ? end_buffer_async_read+0xd5/0xd5
 [<c1156fd0>] ext3_ordered_writepage+0xc8/0x19c
 [<c11566ee>] ? bput_one+0x10/0x10
 [<c109c9ce>] __writepage+0x10/0x28
 [<c109cd96>] write_cache_pages+0x1c9/0x283
 [<c109c9be>] ? bdi_set_max_ratio+0x52/0x52
 [<c109ce86>] generic_writepages+0x36/0x49
 [<c109d994>] do_writepages+0x28/0x2b
 [<c10e5642>] writeback_single_inode+0xa6/0x18d
 [<c10e58ef>] writeback_sb_inodes+0xa6/0x10b
 [<c10e6267>] writeback_inodes_wb+0xd9/0xee
 [<c10e642b>] wb_writeback+0x1af/0x26d
 [<c1045c12>] ? try_to_del_timer_sync+0x81/0x89
 [<c103faca>] ? local_bh_disable+0x8/0x18
 [<c10e655a>] wb_do_writeback+0x71/0x181
 [<c1045dc0>] ? add_timer_on+0x95/0x95
 [<c1045cb1>] ? del_timer+0xc/0x86
 [<c10e66d8>] bdi_writeback_thread+0x6e/0x186
 [<c10e666a>] ? wb_do_writeback+0x181/0x181
 [<c1051f73>] kthread+0x67/0x6c
 [<c1051f0c>] ? kthread_worker_fn+0x114/0x114
 [<c1d74046>] kernel_thread_helper+0x6/0x10
Code: 00 c7 45 c8 00 00 00 00 8d 55 c8 89 90 f4 02 00 00 89 45 b0 8b 53 20 c1 ea 09 89 55 c0 e8 e3 8c 88 00 83 7d c0 00 74 69 8b 43 0c <8b> 40 08 8b 90 84 00 00 00 f6 c2 01 74 04 f3 90 eb f1 8b 70 7c 
EIP: [<c14e85c0>] generic_make_request+0x86/0x3f4 SS:ESP 0068:f5fd7c14
CR2: 0000000000000008
---[ end trace c45e837de578cd2f ]---
------------[ cut here ]------------

 ( the full crashlog is attached as well - hardware details can be found there
   although i doubt it matters. )

Seems to be a generic IO/BDI badness at first sight. It gives me the appearance 
of a race or boundary condition bug, not that of memory corruption.

Here's the crashing generic_make_request() function:

c14e853a <generic_make_request>:
c14e853a:	55                   	push   %ebp
c14e853b:	89 e5                	mov    %esp,%ebp
c14e853d:	57                   	push   %edi
c14e853e:	56                   	push   %esi
c14e853f:	53                   	push   %ebx
c14e8540:	83 ec 6c             	sub    $0x6c,%esp
c14e8543:	e8 08 bb 88 00       	call   c1d74050 <mcount>
c14e8548:	89 c3                	mov    %eax,%ebx
c14e854a:	65 a1 14 00 00 00    	mov    %gs:0x14,%eax
c14e8550:	89 45 f0             	mov    %eax,-0x10(%ebp)
c14e8553:	31 c0                	xor    %eax,%eax
c14e8555:	64 a1 c4 c4 38 c2    	mov    %fs:0xc238c4c4,%eax
c14e855b:	83 b8 f4 02 00 00 00 	cmpl   $0x0,0x2f4(%eax)
c14e8562:	74 23                	je     c14e8587 <generic_make_request+0x4d>
c14e8564:	8b 80 f4 02 00 00    	mov    0x2f4(%eax),%eax
c14e856a:	c7 43 08 00 00 00 00 	movl   $0x0,0x8(%ebx)
c14e8571:	8b 50 04             	mov    0x4(%eax),%edx
c14e8574:	85 d2                	test   %edx,%edx
c14e8576:	74 05                	je     c14e857d <generic_make_request+0x43>
c14e8578:	89 5a 08             	mov    %ebx,0x8(%edx)
c14e857b:	eb 02                	jmp    c14e857f <generic_make_request+0x45>
c14e857d:	89 18                	mov    %ebx,(%eax)
c14e857f:	89 58 04             	mov    %ebx,0x4(%eax)
c14e8582:	e9 8e 03 00 00       	jmp    c14e8915 <generic_make_request+0x3db>
c14e8587:	83 7b 08 00          	cmpl   $0x0,0x8(%ebx)
c14e858b:	74 02                	je     c14e858f <generic_make_request+0x55>
c14e858d:	0f 0b                	ud2    
c14e858f:	c7 45 cc 00 00 00 00 	movl   $0x0,-0x34(%ebp)
c14e8596:	c7 45 c8 00 00 00 00 	movl   $0x0,-0x38(%ebp)
c14e859d:	8d 55 c8             	lea    -0x38(%ebp),%edx
c14e85a0:	89 90 f4 02 00 00    	mov    %edx,0x2f4(%eax)
c14e85a6:	89 45 b0             	mov    %eax,-0x50(%ebp)
c14e85a9:	8b 53 20             	mov    0x20(%ebx),%edx
c14e85ac:	c1 ea 09             	shr    $0x9,%edx
c14e85af:	89 55 c0             	mov    %edx,-0x40(%ebp)
c14e85b2:	e8 e3 8c 88 00       	call   c1d7129a <_cond_resched>
c14e85b7:	83 7d c0 00          	cmpl   $0x0,-0x40(%ebp)
c14e85bb:	74 69                	je     c14e8626 <generic_make_request+0xec>
c14e85bd:	8b 43 0c             	mov    0xc(%ebx),%eax
c14e85c0:	8b 40 08             	mov    0x8(%eax),%eax
c14e85c3:	8b 90 84 00 00 00    	mov    0x84(%eax),%edx
c14e85c9:	f6 c2 01             	test   $0x1,%dl
c14e85cc:	74 04                	je     c14e85d2 <generic_make_request+0x98>
c14e85ce:	f3 90                	pause  
c14e85d0:	eb f1                	jmp    c14e85c3 <generic_make_request+0x89>
c14e85d2:	8b 70 7c             	mov    0x7c(%eax),%esi
c14e85d5:	8b b8 80 00 00 00    	mov    0x80(%eax),%edi
c14e85db:	39 90 84 00 00 00    	cmp    %edx,0x84(%eax)
c14e85e1:	75 e0                	jne    c14e85c3 <generic_make_request+0x89>
c14e85e3:	89 f0                	mov    %esi,%eax
c14e85e5:	89 fa                	mov    %edi,%edx
c14e85e7:	0f ac d0 09          	shrd   $0x9,%edx,%eax
c14e85eb:	c1 fa 09             	sar    $0x9,%edx
c14e85ee:	89 d1                	mov    %edx,%ecx
c14e85f0:	09 c1                	or     %eax,%ecx
c14e85f2:	74 32                	je     c14e8626 <generic_make_request+0xec>
c14e85f4:	8b 0b                	mov    (%ebx),%ecx
c14e85f6:	89 4d c4             	mov    %ecx,-0x3c(%ebp)
c14e85f9:	8b 4b 04             	mov    0x4(%ebx),%ecx
c14e85fc:	8b 75 c0             	mov    -0x40(%ebp),%esi
c14e85ff:	31 ff                	xor    %edi,%edi
c14e8601:	83 fa 00             	cmp    $0x0,%edx
c14e8604:	77 09                	ja     c14e860f <generic_make_request+0xd5>
c14e8606:	3b 45 c0             	cmp    -0x40(%ebp),%eax
c14e8609:	0f 82 21 02 00 00    	jb     c14e8830 <generic_make_request+0x2f6>
c14e860f:	29 f0                	sub    %esi,%eax
c14e8611:	19 fa                	sbb    %edi,%edx
c14e8613:	39 ca                	cmp    %ecx,%edx
c14e8615:	77 0f                	ja     c14e8626 <generic_make_request+0xec>
c14e8617:	0f 82 13 02 00 00    	jb     c14e8830 <generic_make_request+0x2f6>
c14e861d:	3b 45 c4             	cmp    -0x3c(%ebp),%eax
c14e8620:	0f 82 0a 02 00 00    	jb     c14e8830 <generic_make_request+0x2f6>
c14e8626:	c7 45 b4 00 00 00 00 	movl   $0x0,-0x4c(%ebp)
c14e862d:	c7 45 b8 ff ff ff ff 	movl   $0xffffffff,-0x48(%ebp)
c14e8634:	c7 45 bc ff ff ff ff 	movl   $0xffffffff,-0x44(%ebp)
c14e863b:	8b 45 c0             	mov    -0x40(%ebp),%eax
c14e863e:	89 45 9c             	mov    %eax,-0x64(%ebp)
c14e8641:	c7 45 a0 00 00 00 00 	movl   $0x0,-0x60(%ebp)
c14e8648:	8b 43 0c             	mov    0xc(%ebx),%eax
c14e864b:	89 45 98             	mov    %eax,-0x68(%ebp)
c14e864e:	89 c2                	mov    %eax,%edx
c14e8650:	8b 40 58             	mov    0x58(%eax),%eax
c14e8653:	8b 80 c8 01 00 00    	mov    0x1c8(%eax),%eax
c14e8659:	89 45 c4             	mov    %eax,-0x3c(%ebp)
c14e865c:	85 c0                	test   %eax,%eax
c14e865e:	75 33                	jne    c14e8693 <generic_make_request+0x159>
c14e8660:	89 d1                	mov    %edx,%ecx
c14e8662:	8b 33                	mov    (%ebx),%esi
c14e8664:	8b 7b 04             	mov    0x4(%ebx),%edi
c14e8667:	8d 55 d0             	lea    -0x30(%ebp),%edx
c14e866a:	89 c8                	mov    %ecx,%eax
c14e866c:	e8 27 8c c2 ff       	call   c1111298 <bdevname>
c14e8671:	89 74 24 08          	mov    %esi,0x8(%esp)
c14e8675:	89 7c 24 0c          	mov    %edi,0xc(%esp)
c14e8679:	89 44 24 04          	mov    %eax,0x4(%esp)
c14e867d:	c7 04 24 52 b5 01 c2 	movl   $0xc201b552,(%esp)
c14e8684:	e8 79 17 87 00       	call   c1d59e02 <printk>
c14e8689:	ba fb ff ff ff       	mov    $0xfffffffb,%edx
c14e868e:	e9 43 02 00 00       	jmp    c14e88d6 <generic_make_request+0x39c>
c14e8693:	f6 43 14 40          	testb  $0x40,0x14(%ebx)
c14e8697:	75 36                	jne    c14e86cf <generic_make_request+0x195>
c14e8699:	8b 4d c4             	mov    -0x3c(%ebp),%ecx
c14e869c:	8b b9 3c 02 00 00    	mov    0x23c(%ecx),%edi
c14e86a2:	39 7d c0             	cmp    %edi,-0x40(%ebp)
c14e86a5:	76 28                	jbe    c14e86cf <generic_make_request+0x195>
c14e86a7:	8b 4d 98             	mov    -0x68(%ebp),%ecx
c14e86aa:	8b 73 20             	mov    0x20(%ebx),%esi
c14e86ad:	c1 ee 09             	shr    $0x9,%esi
c14e86b0:	8d 55 d0             	lea    -0x30(%ebp),%edx
c14e86b3:	89 c8                	mov    %ecx,%eax
c14e86b5:	e8 de 8b c2 ff       	call   c1111298 <bdevname>
c14e86ba:	89 7c 24 0c          	mov    %edi,0xc(%esp)
c14e86be:	89 74 24 08          	mov    %esi,0x8(%esp)
c14e86c2:	89 44 24 04          	mov    %eax,0x4(%esp)
c14e86c6:	c7 04 24 9f b5 01 c2 	movl   $0xc201b59f,(%esp)
c14e86cd:	eb b5                	jmp    c14e8684 <generic_make_request+0x14a>
c14e86cf:	8b 55 c4             	mov    -0x3c(%ebp),%edx
c14e86d2:	8b 82 a4 01 00 00    	mov    0x1a4(%edx),%eax
c14e86d8:	a8 20                	test   $0x20,%al
c14e86da:	75 ad                	jne    c14e8689 <generic_make_request+0x14f>
c14e86dc:	8b 43 20             	mov    0x20(%ebx),%eax
c14e86df:	c1 e8 09             	shr    $0x9,%eax
c14e86e2:	0f 84 80 00 00 00    	je     c14e8768 <generic_make_request+0x22e>
c14e86e8:	8b 45 98             	mov    -0x68(%ebp),%eax
c14e86eb:	3b 40 44             	cmp    0x44(%eax),%eax
c14e86ee:	74 78                	je     c14e8768 <generic_make_request+0x22e>
c14e86f0:	8b 50 4c             	mov    0x4c(%eax),%edx
c14e86f3:	89 55 a8             	mov    %edx,-0x58(%ebp)
c14e86f6:	8b 32                	mov    (%edx),%esi
c14e86f8:	8b 7a 04             	mov    0x4(%edx),%edi
c14e86fb:	03 33                	add    (%ebx),%esi
c14e86fd:	13 7b 04             	adc    0x4(%ebx),%edi
c14e8700:	89 33                	mov    %esi,(%ebx)
c14e8702:	89 7b 04             	mov    %edi,0x4(%ebx)
c14e8705:	8b 40 44             	mov    0x44(%eax),%eax
c14e8708:	89 45 a4             	mov    %eax,-0x5c(%ebp)
c14e870b:	89 43 0c             	mov    %eax,0xc(%ebx)
c14e870e:	89 f2                	mov    %esi,%edx
c14e8710:	89 f9                	mov    %edi,%ecx
c14e8712:	8b 45 a8             	mov    -0x58(%ebp),%eax
c14e8715:	2b 10                	sub    (%eax),%edx
c14e8717:	1b 48 04             	sbb    0x4(%eax),%ecx
c14e871a:	89 55 a8             	mov    %edx,-0x58(%ebp)
c14e871d:	89 4d ac             	mov    %ecx,-0x54(%ebp)
c14e8720:	8b 45 98             	mov    -0x68(%ebp),%eax
c14e8723:	8b 38                	mov    (%eax),%edi
c14e8725:	8b 55 a4             	mov    -0x5c(%ebp),%edx
c14e8728:	8b 42 58             	mov    0x58(%edx),%eax
c14e872b:	8b 80 c8 01 00 00    	mov    0x1c8(%eax),%eax
c14e8731:	89 45 a4             	mov    %eax,-0x5c(%ebp)
c14e8734:	e9 00 00 00 00       	jmp    c14e8739 <generic_make_request+0x1ff>
c14e8739:	eb 2d                	jmp    c14e8768 <generic_make_request+0x22e>
c14e873b:	8b 35 84 4e 2a c2    	mov    0xc22a4e84,%esi
c14e8741:	85 f6                	test   %esi,%esi
c14e8743:	74 23                	je     c14e8768 <generic_make_request+0x22e>
c14e8745:	8b 46 04             	mov    0x4(%esi),%eax
c14e8748:	8b 55 a8             	mov    -0x58(%ebp),%edx
c14e874b:	8b 4d ac             	mov    -0x54(%ebp),%ecx
c14e874e:	89 54 24 04          	mov    %edx,0x4(%esp)
c14e8752:	89 4c 24 08          	mov    %ecx,0x8(%esp)
c14e8756:	89 3c 24             	mov    %edi,(%esp)
c14e8759:	89 d9                	mov    %ebx,%ecx
c14e875b:	8b 55 a4             	mov    -0x5c(%ebp),%edx
c14e875e:	ff 16                	call   *(%esi)
c14e8760:	83 c6 08             	add    $0x8,%esi
c14e8763:	83 3e 00             	cmpl   $0x0,(%esi)
c14e8766:	eb db                	jmp    c14e8743 <generic_make_request+0x209>
c14e8768:	89 d8                	mov    %ebx,%eax
c14e876a:	e8 a1 a2 c0 ff       	call   c10f2a10 <bio_integrity_enabled>
c14e876f:	85 c0                	test   %eax,%eax
c14e8771:	74 0f                	je     c14e8782 <generic_make_request+0x248>
c14e8773:	89 d8                	mov    %ebx,%eax
c14e8775:	e8 06 a4 c0 ff       	call   c10f2b80 <bio_integrity_prep>
c14e877a:	85 c0                	test   %eax,%eax
c14e877c:	0f 85 07 ff ff ff    	jne    c14e8689 <generic_make_request+0x14f>
c14e8782:	83 7d bc ff          	cmpl   $0xffffffff,-0x44(%ebp)
c14e8786:	75 06                	jne    c14e878e <generic_make_request+0x254>
c14e8788:	83 7d b8 ff          	cmpl   $0xffffffff,-0x48(%ebp)
c14e878c:	74 37                	je     c14e87c5 <generic_make_request+0x28b>
c14e878e:	e9 00 00 00 00       	jmp    c14e8793 <generic_make_request+0x259>
c14e8793:	eb 30                	jmp    c14e87c5 <generic_make_request+0x28b>
c14e8795:	8b 35 84 4e 2a c2    	mov    0xc22a4e84,%esi
c14e879b:	85 f6                	test   %esi,%esi
c14e879d:	74 26                	je     c14e87c5 <generic_make_request+0x28b>
c14e879f:	8b 46 04             	mov    0x4(%esi),%eax
c14e87a2:	8b 55 b8             	mov    -0x48(%ebp),%edx
c14e87a5:	8b 4d bc             	mov    -0x44(%ebp),%ecx
c14e87a8:	89 54 24 04          	mov    %edx,0x4(%esp)
c14e87ac:	89 4c 24 08          	mov    %ecx,0x8(%esp)
c14e87b0:	8b 4d b4             	mov    -0x4c(%ebp),%ecx
c14e87b3:	89 0c 24             	mov    %ecx,(%esp)
c14e87b6:	89 d9                	mov    %ebx,%ecx
c14e87b8:	8b 55 c4             	mov    -0x3c(%ebp),%edx
c14e87bb:	ff 16                	call   *(%esi)
c14e87bd:	83 c6 08             	add    $0x8,%esi
c14e87c0:	83 3e 00             	cmpl   $0x0,(%esi)
c14e87c3:	eb d8                	jmp    c14e879d <generic_make_request+0x263>
c14e87c5:	8b 03                	mov    (%ebx),%eax
c14e87c7:	8b 53 04             	mov    0x4(%ebx),%edx
c14e87ca:	89 45 b8             	mov    %eax,-0x48(%ebp)
c14e87cd:	89 55 bc             	mov    %edx,-0x44(%ebp)
c14e87d0:	8b 43 0c             	mov    0xc(%ebx),%eax
c14e87d3:	8b 10                	mov    (%eax),%edx
c14e87d5:	89 55 b4             	mov    %edx,-0x4c(%ebp)
c14e87d8:	83 7d c0 00          	cmpl   $0x0,-0x40(%ebp)
c14e87dc:	74 5e                	je     c14e883c <generic_make_request+0x302>
c14e87de:	8b 50 08             	mov    0x8(%eax),%edx
c14e87e1:	8b 82 84 00 00 00    	mov    0x84(%edx),%eax
c14e87e7:	a8 01                	test   $0x1,%al
c14e87e9:	74 04                	je     c14e87ef <generic_make_request+0x2b5>
c14e87eb:	f3 90                	pause  
c14e87ed:	eb f2                	jmp    c14e87e1 <generic_make_request+0x2a7>
c14e87ef:	8b 72 7c             	mov    0x7c(%edx),%esi
c14e87f2:	8b ba 80 00 00 00    	mov    0x80(%edx),%edi
c14e87f8:	39 82 84 00 00 00    	cmp    %eax,0x84(%edx)
c14e87fe:	75 e1                	jne    c14e87e1 <generic_make_request+0x2a7>
c14e8800:	89 f0                	mov    %esi,%eax
c14e8802:	89 fa                	mov    %edi,%edx
c14e8804:	0f ac d0 09          	shrd   $0x9,%edx,%eax
c14e8808:	c1 fa 09             	sar    $0x9,%edx
c14e880b:	89 d1                	mov    %edx,%ecx
c14e880d:	09 c1                	or     %eax,%ecx
c14e880f:	74 2b                	je     c14e883c <generic_make_request+0x302>
c14e8811:	8b 33                	mov    (%ebx),%esi
c14e8813:	8b 4b 04             	mov    0x4(%ebx),%ecx
c14e8816:	83 fa 00             	cmp    $0x0,%edx
c14e8819:	77 05                	ja     c14e8820 <generic_make_request+0x2e6>
c14e881b:	3b 45 c0             	cmp    -0x40(%ebp),%eax
c14e881e:	72 10                	jb     c14e8830 <generic_make_request+0x2f6>
c14e8820:	2b 45 9c             	sub    -0x64(%ebp),%eax
c14e8823:	1b 55 a0             	sbb    -0x60(%ebp),%edx
c14e8826:	39 ca                	cmp    %ecx,%edx
c14e8828:	77 12                	ja     c14e883c <generic_make_request+0x302>
c14e882a:	72 04                	jb     c14e8830 <generic_make_request+0x2f6>
c14e882c:	39 f0                	cmp    %esi,%eax
c14e882e:	73 0c                	jae    c14e883c <generic_make_request+0x302>
c14e8830:	89 d8                	mov    %ebx,%eax
c14e8832:	e8 87 e7 ff ff       	call   c14e6fbe <handle_bad_sector>
c14e8837:	e9 4d fe ff ff       	jmp    c14e8689 <generic_make_request+0x14f>
c14e883c:	8b 43 14             	mov    0x14(%ebx),%eax
c14e883f:	a9 00 10 80 00       	test   $0x801000,%eax
c14e8844:	74 1a                	je     c14e8860 <generic_make_request+0x326>
c14e8846:	8b 55 c4             	mov    -0x3c(%ebp),%edx
c14e8849:	83 ba 7c 02 00 00 00 	cmpl   $0x0,0x27c(%edx)
c14e8850:	75 0e                	jne    c14e8860 <generic_make_request+0x326>
c14e8852:	25 ff ef 7f ff       	and    $0xff7fefff,%eax
c14e8857:	89 43 14             	mov    %eax,0x14(%ebx)
c14e885a:	83 7d c0 00          	cmpl   $0x0,-0x40(%ebp)
c14e885e:	74 6d                	je     c14e88cd <generic_make_request+0x393>
c14e8860:	8b 43 14             	mov    0x14(%ebx),%eax
c14e8863:	a8 40                	test   $0x40,%al
c14e8865:	74 2d                	je     c14e8894 <generic_make_request+0x35a>
c14e8867:	8b 4d c4             	mov    -0x3c(%ebp),%ecx
c14e886a:	8b 91 a4 01 00 00    	mov    0x1a4(%ecx),%edx
c14e8870:	80 e6 40             	and    $0x40,%dh
c14e8873:	74 5c                	je     c14e88d1 <generic_make_request+0x397>
c14e8875:	a9 00 00 00 08       	test   $0x8000000,%eax
c14e887a:	74 18                	je     c14e8894 <generic_make_request+0x35a>
c14e887c:	8b 81 a4 01 00 00    	mov    0x1a4(%ecx),%eax
c14e8882:	f6 c4 40             	test   $0x40,%ah
c14e8885:	74 4a                	je     c14e88d1 <generic_make_request+0x397>
c14e8887:	8b 81 a4 01 00 00    	mov    0x1a4(%ecx),%eax
c14e888d:	a9 00 00 02 00       	test   $0x20000,%eax
c14e8892:	74 3d                	je     c14e88d1 <generic_make_request+0x397>
c14e8894:	85 db                	test   %ebx,%ebx
c14e8896:	74 45                	je     c14e88dd <generic_make_request+0x3a3>
c14e8898:	e9 00 00 00 00       	jmp    c14e889d <generic_make_request+0x363>
c14e889d:	eb 1c                	jmp    c14e88bb <generic_make_request+0x381>
c14e889f:	8b 35 fc 4e 2a c2    	mov    0xc22a4efc,%esi
c14e88a5:	85 f6                	test   %esi,%esi
c14e88a7:	74 12                	je     c14e88bb <generic_make_request+0x381>
c14e88a9:	8b 46 04             	mov    0x4(%esi),%eax
c14e88ac:	89 d9                	mov    %ebx,%ecx
c14e88ae:	8b 55 c4             	mov    -0x3c(%ebp),%edx
c14e88b1:	ff 16                	call   *(%esi)
c14e88b3:	83 c6 08             	add    $0x8,%esi
c14e88b6:	83 3e 00             	cmpl   $0x0,(%esi)
c14e88b9:	eb ec                	jmp    c14e88a7 <generic_make_request+0x36d>
c14e88bb:	89 da                	mov    %ebx,%edx
c14e88bd:	8b 45 c4             	mov    -0x3c(%ebp),%eax
c14e88c0:	ff 50 44             	call   *0x44(%eax)
c14e88c3:	85 c0                	test   %eax,%eax
c14e88c5:	0f 85 7d fd ff ff    	jne    c14e8648 <generic_make_request+0x10e>
c14e88cb:	eb 10                	jmp    c14e88dd <generic_make_request+0x3a3>
c14e88cd:	31 d2                	xor    %edx,%edx
c14e88cf:	eb 05                	jmp    c14e88d6 <generic_make_request+0x39c>
c14e88d1:	ba a1 ff ff ff       	mov    $0xffffffa1,%edx
c14e88d6:	89 d8                	mov    %ebx,%eax
c14e88d8:	e8 b8 49 c0 ff       	call   c10ed295 <bio_endio>
c14e88dd:	8b 55 b0             	mov    -0x50(%ebp),%edx
c14e88e0:	8b 82 f4 02 00 00    	mov    0x2f4(%edx),%eax
c14e88e6:	8b 18                	mov    (%eax),%ebx
c14e88e8:	85 db                	test   %ebx,%ebx
c14e88ea:	74 1c                	je     c14e8908 <generic_make_request+0x3ce>
c14e88ec:	8b 53 08             	mov    0x8(%ebx),%edx
c14e88ef:	89 10                	mov    %edx,(%eax)
c14e88f1:	85 d2                	test   %edx,%edx
c14e88f3:	75 07                	jne    c14e88fc <generic_make_request+0x3c2>
c14e88f5:	c7 40 04 00 00 00 00 	movl   $0x0,0x4(%eax)
c14e88fc:	c7 43 08 00 00 00 00 	movl   $0x0,0x8(%ebx)
c14e8903:	e9 a1 fc ff ff       	jmp    c14e85a9 <generic_make_request+0x6f>
c14e8908:	8b 4d b0             	mov    -0x50(%ebp),%ecx
c14e890b:	c7 81 f4 02 00 00 00 	movl   $0x0,0x2f4(%ecx)
c14e8912:	00 00 00 
c14e8915:	8b 45 f0             	mov    -0x10(%ebp),%eax
c14e8918:	65 33 05 14 00 00 00 	xor    %gs:0x14,%eax
c14e891f:	74 05                	je     c14e8926 <generic_make_request+0x3ec>
c14e8921:	e8 56 27 b5 ff       	call   c103b07c <__stack_chk_fail>
c14e8926:	83 c4 6c             	add    $0x6c,%esp
c14e8929:	5b                   	pop    %ebx
c14e892a:	5e                   	pop    %esi
c14e892b:	5f                   	pop    %edi
c14e892c:	5d                   	pop    %ebp
c14e892d:	c3                   	ret    

The crash is at:

  c14e85ac:       c1 ea 09                shr    $0x9,%edx
  c14e85af:       89 55 c0                mov    %edx,-0x40(%ebp)
  c14e85b2:       e8 e3 8c 88 00          call   c1d7129a <_cond_resched>
  c14e85b7:       83 7d c0 00             cmpl   $0x0,-0x40(%ebp)
  c14e85bb:       74 69                   je     c14e8626 <generic_make_request+0xec>
  c14e85bd:       8b 43 0c                mov    0xc(%ebx),%eax
* c14e85c0:       8b 40 08                mov    0x8(%eax),%eax   <==== [ **CRASH** ]
  c14e85c3:       8b 90 84 00 00 00       mov    0x84(%eax),%edx
  c14e85c9:       f6 c2 01                test   $0x1,%dl

which corresponds to:

1414	
1415		if (!nr_sectors)
1416			return 0;
1417	
1418		/* Test device or partition size, when known. */
1419		maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;   <==== [ **CRASH** ]
1420		if (maxsector) {
1421			sector_t sector = bio->bi_sector;
1422	
1423			if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {

bio->bi_bdev has become NULL?

I do not think the _cond_resched() was called, judging from stack contents. But 
we just had an IRQ:

 [<c1d74030>] ? common_interrupt+0x30/0x40

So we might have raced with block IO IRQ queue-completion/submission activites.

But maybe it was a reschedule after all, just the stack does not carry any 
traces of it anymore. IRQs do not clear ->bi_bdev, right? Unless the bio 
refcounts are wrong and an IRQ's completion actually frees the bio, right?

I've built a CONFIG_DEBUG_PAGEALLOC=y and CONFIG_SLUB_DEBUG=y kernel, maybe the 
crash triggers in a more revealing way.

Thanks,

	Ingo

View attachment "config.zipproblem2" of type "text/plain" (130545 bytes)

View attachment "crash.log" of type "text/plain" (205089 bytes)

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