Re: [BUG] AS io-scheduler.

From: Chuck Ebbert
Date: Mon Jul 16 2007 - 12:32:23 EST


On 07/15/2007 11:20 AM, Ian Kumlien wrote:
> I had emerge --sync failing several times...
>
> So i checked dmesg and found some info, attached further down.
> This is a old VIA C3 machine with one disk, it's been running most
> kernels in the 2.6.x series with no problems until now.
>
> PS. Don't forget to CC me
> DS.
>
> 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?
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