Re: Internal error xfs_sb_read_verify at line 726

[Eric Sandeen <sandeen@sandeen.net>]

On 5/6/13 2:26 PM, Markus Trippelsdorf wrote:
> On 2013.05.06 at 14:14 -0500, Eric Sandeen wrote:
>> On 5/6/13 1:30 PM, Markus Trippelsdorf wrote:
>>> On 2013.05.06 at 12:04 -0500, Eric Sandeen wrote:
>>>> On 5/6/13 6:27 AM, Markus Trippelsdorf wrote:
>>>>> Today I accidentally tried to mount my backup disk at /dev/sdc instead
>>>>> of /dev/sdc1 and this is what happened:
>>>>>
>>>>> ...
>>>>> EXT4-fs (sdc): VFS: Can't find ext4 filesystem
>>>>> FAT-fs (sdc): bogus number of reserved sectors
>>>>> FAT-fs (sdc): Can't find a valid FAT filesystem
>>>>> FAT-fs (sdc): bogus number of reserved sectors
>>>>> FAT-fs (sdc): Can't find a valid FAT filesystem
>>>>> ISOFS: Unable to identify CD-ROM format.
>>>>> XFS (sdc): bad magic number
>>>>> ffff8800db620000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>>>> ffff8800db620010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>>>> ffff8800db620020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>>>> ffff8800db620030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>>>> XFS (sdc): Internal error xfs_sb_read_verify at line 726 of file fs/xfs/xfs_mount.c.  Caller 0xffffffff8119e5cd
>>>>
>>>> This seems to be a recent regression.
>>>>
>>>> Comments above xfs_sb_quiet_read_verify() indicate that this behavior is
>>>> to be avoided:
>>>>
>>>>  * We may be probed for a filesystem match, so we may not want to emit
>>>>  * messages when the superblock buffer is not actually an XFS superblock.
>>>>
>>>> and it checks for proper magic prior to all the chattiness above int
>>>> that function.
>>>>
>>>> The superblock read is suposed to choose whether to be noisy or not,
>>>> in xfs_readsb():
>>>>
>>>
>>> The following patch fixes the issue for me:
>>>
>>>
>>> diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
>>> index f6bfbd7..db8f27f 100644
>>> --- a/fs/xfs/xfs_mount.c
>>> +++ b/fs/xfs/xfs_mount.c
>>> @@ -721,6 +721,11 @@ xfs_sb_read_verify(
>>>  	}
>>>  	error = xfs_sb_verify(bp);
>>>  
>>> +	if (error == XFS_ERROR(EWRONGFS)) {
>>> +		xfs_buf_ioerror(bp, EWRONGFS);
>>> +		return;
>>> +	}
>>> +
>>>  out_error:
>>>  	if (error) {
>>>  		XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr);
>>
>> That might make sense, I don't think we need the loudness for EWRONGFS
>> no matter how we got there.  
>>
>> But:
>>
>> Out of curiosity, what was the actual mount command you used?  It seems like
>> the auto-probing should have set the MS_SILENT flag to avoid this in
>> the first place, i.e. we should have gone down the quiet path
>> (xfs_sb_quiet_read_verify) and avoided this altogether.
>>
>> How do you reproduce this?
> 
> I power on the drive and simply run:
> 
>  # mount /dev/sdc /mnt

Interesting.  On my test box, that never even issues the mount syscall,
because it uses blkid (I guess) to probe, and finds nothing.

Which util-linux do you have?

An strace -v of the mount command might be useful.

-Eric

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