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Re: XFS: Assertion failed: bp->b_bn != XFS_BUF_DADDR_NULL, file: fs/xfs/

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: XFS: Assertion failed: bp->b_bn != XFS_BUF_DADDR_NULL, file: fs/xfs/xfs_buf.c, line: 598
From: Rafał Kupka <kupson@xxxxxxxxxx>
Date: Mon, 26 Mar 2012 18:05:25 +0200
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
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On Thu, 2012-03-08 at 20:10 +0100, Rafał Kupka wrote: 
> On Wed, 2012-03-07 at 07:30 +1100, Dave Chinner wrote:

Hi,

Finally I've captured this event trace. Hope it will help.

> > Also, it might be worthwhile to capture an event trace (e.g. all the
> > xfs_buf events) to see what occurs just before the error is
> > triggered. That might tell us exactl what sequence has occurred
> > leading up to the error.
> 
> I will try to provide this information in a few days.

Kernel version - Linus tree up to:
0e6e847f "xfs: stop using the page cache to back the buffer cache"

It's uniprocessor virtual machine (KVM) with 384 MB RAM.

Full event trace is available at https://gist.github.com/2206109
(sorry for it's *.perl extension, my mistake).

Kernel log entry:
[  495.197571] XFS (vda2): I/O error occurred: meta-data dev vda2 block 0x13d80 
      ("xfs_trans_read_buf") error 5 buf count 8192
[  495.198283] XFS (vda2): xfs_imap_to_bp: xfs_trans_read_buf() returned error 
5.
[  501.540477] XFS (vda2): I/O error occurred: meta-data dev vda2 block 0x13d80 
      ("xfs_trans_read_buf") error 5 buf count 8192
[  501.543047] XFS (vda2): xfs_imap_to_bp: xfs_trans_read_buf() returned error 
5.

It's possible that this "I/O error" is caused by memory pressure?

Related trace line:
xfsdump-2498  [000] 24195.782269: xfs_buf_ioerror: dev 254:2 bno 0x13d80 len 
0x2000 hold 3 pincount 0 lock 0 error 5 flags READ|TRYLOCK|PAGES caller 
_xfs_buf_ioapply

Events related to "bno 0x13d80":
xfsdump-2498  [000] 24195.782266: xfs_buf_get: dev 254:2 bno 0x13d80 len 0x2000 
hold 2 pincount 0 lock 0 flags READ|LOCK|DONT_BLOCK caller xfs_buf_read
xfsdump-2498  [000] 24195.782266: xfs_buf_read: dev 254:2 bno 0x13d80 len 
0x2000 hold 2 pincount 0 lock 0 flags READ|LOCK|DONT_BLOCK caller 
xfs_trans_read_buf
xfsdump-2498  [000] 24195.782267: xfs_buf_iorequest: dev 254:2 bno 0x13d80 len 
0x2000 hold 2 pincount 0 lock 0 flags READ|TRYLOCK|PAGES caller _xfs_buf_read
xfsdump-2498  [000] 24195.782267: xfs_buf_hold: dev 254:2 bno 0x13d80 len 
0x2000 hold 2 pincount 0 lock 0 flags READ|TRYLOCK|PAGES caller 
xfs_buf_iorequest
xfsdump-2498  [000] 24195.782269: xfs_buf_ioerror: dev 254:2 bno 0x13d80 len 
0x2000 hold 3 pincount 0 lock 0 error 5 flags READ|TRYLOCK|PAGES caller 
_xfs_buf_ioapply
xfsdump-2498  [000] 24195.782270: xfs_buf_rele: dev 254:2 bno 0x13d80 len 
0x2000 hold 3 pincount 0 lock 0 flags READ|TRYLOCK|PAGES caller 
xfs_buf_iorequest
xfsdump-2498  [000] 24195.782985: xfs_buf_unlock: dev 254:2 bno 0x13d80 len 
0x2000 hold 2 pincount 0 lock 1 flags READ|TRYLOCK|PAGES caller xfs_buf_relse
xfsdump-2498  [000] 24195.782986: xfs_buf_rele: dev 254:2 bno 0x13d80 len 
0x2000 hold 2 pincount 0 lock 1 flags READ|TRYLOCK|PAGES caller 
xfs_trans_read_buf

Do this data put some light on this issue?

Regards,
Rafał Kupka

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