linux-kernel - Re: [BUG] AS io-scheduler.

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Date:	Tue, 17 Jul 2007 03:44:00 +0200
From:	Rene Herman <rene.herman@...il.com>
To:	Chuck Ebbert <cebbert@...hat.com>
CC:	pomac@...or.com, Linux-kernel@...r.kernel.org,
	Jens Axboe <jens.axboe@...cle.com>,
	Nick Piggin <npiggin@...e.de>
Subject: Re: [BUG] AS io-scheduler.

On 07/16/2007 06:31 PM, Chuck Ebbert wrote:

>> BUG: unable to handle kernel paging request at virtual address ea86ac54
>>  printing eip:
>> c022dfec
>> *pde = 00000000
>> Oops: 0000 [#1]
>> Modules linked in: eeprom i2c_viapro vt8231 i2c_isa skge
>> CPU:    0
>> EIP:    0060:[<c022dfec>]    Not tainted VLI
>> EFLAGS: 00010082   (2.6.22.1 #26)
>> EIP is at as_can_break_anticipation+0xc/0x190
>> eax: dfcdaba0   ebx: dfcdaba0   ecx: 0035ff95   edx: cb296844
>> esi: cb296844   edi: dfcdaba0   ebp: 00000000   esp: ceff6a70
>> ds: 007b   es: 007b   fs: 0000  gs: 0033  ss: 0068
>> Process rsync (pid: 1667, ti=ceff6000 task=d59cf5b0 task.ti=ceff6000)
>> Stack: cb296844 00000001 cb296844 dfcdaba0 00000000 c022efc8 cb296844
>> 00000000 
>>        dfcffb9c c0227a76 dfcffb9c 00000000 c016e96e cb296844 00000000
>> dfcffb9c 
>>        00000000 c022af64 00000000 dfcffb9c 00000008 00000000 08ff6b30
>> c04d1ec0 
>> Call Trace:
>>  [<c022efc8>] as_add_request+0xa8/0xc0
>>  [<c0227a76>] elv_insert+0xa6/0x150
>>  [<c016e96e>] bio_phys_segments+0xe/0x20
>>  [<c022af64>] __make_request+0x384/0x490
>>  [<c02add1e>] ide_do_request+0x6ee/0x890
>>  [<c02294ab>] generic_make_request+0x18b/0x1c0
>>  [<c022b596>] submit_bio+0xa6/0xb0
>>  [<c013b7b8>] mempool_alloc+0x28/0xa0
>>  [<c016bb66>] __find_get_block+0xf6/0x130
>>  [<c016e0bc>] bio_alloc_bioset+0x8c/0xf0
>>  [<c016b647>] submit_bh+0xb7/0xe0
>>  [<c016c1f8>] ll_rw_block+0x78/0x90
>>  [<c019c85d>] search_by_key+0xdd/0xd20
>>  [<c016c201>] ll_rw_block+0x81/0x90
>>  [<c011f190>] irq_exit+0x40/0x60
>>  [<c01066e4>] do_IRQ+0x94/0xb0
>>  [<c0104bc3>] common_interrupt+0x23/0x30
>>  [<c018beca>] reiserfs_read_locked_inode+0x6a/0x490
>>  [<c018e580>] reiserfs_find_actor+0x0/0x20
>>  [<c018c33b>] reiserfs_iget+0x4b/0x80
>>  [<c018e570>] reiserfs_init_locked_inode+0x0/0x10
>>  [<c0189824>] reiserfs_lookup+0xa4/0xf0
>>  [<c0157b03>] do_lookup+0xa3/0x140
>>  [<c0159265>] __link_path_walk+0x615/0xa20
>>  [<c0168a18>] __mark_inode_dirty+0x28/0x150
>>  [<c01631c1>] mntput_no_expire+0x11/0x50
>>  [<c01596b2>] link_path_walk+0x42/0xb0
>>  [<c0159960>] do_path_lookup+0x130/0x150
>>  [<c015a190>] __user_walk_fd+0x30/0x50
>>  [<c0154766>] vfs_lstat_fd+0x16/0x40
>>  [<c01547df>] sys_lstat64+0xf/0x30
>>  [<c0103c42>] syscall_call+0x7/0xb
>>  =======================
> 
> static int as_can_break_anticipation(struct as_data *ad, struct request *rq)
> {
>         struct io_context *ioc;
>         struct as_io_context *aic;
> 
>         ioc = ad->io_context;  <======== ad is bogus
>         BUG_ON(!ioc);
> 
> 
> Call chain is:
> 
> 	as_add_request
> 	as_update_rq:
> 	        if (ad->antic_status == ANTIC_WAIT_REQ
>         	                || ad->antic_status == ANTIC_WAIT_NEXT) {
>                 	if (as_can_break_anticipation(ad, rq))
>                         	as_antic_stop(ad);
>         	}
> 
> 
> So somehow 'ad' became invalid between the time ad->antic_status was
> checked and as_can_break_anticipation() tried to access ad->io_context?

Is this similar to:

http://lkml.org/lkml/2007/6/4/50

?

Rene.
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