Issue with 'Unknown Error: -512'

[Garrett Cooper]

On Tue, Jul 19, 2011 at 4:58 AM, Garrett Cooper <yanegomi at gmail.com> wrote:
> On Mon, Jul 18, 2011 at 5:19 PM, Brandon Falk <falkman at gamozo.org> wrote:
>> On 7/18/2011 10:18 AM, Andriy Gapon wrote:
>>>
>>> on 18/07/2011 17:53 Brandon Falk said the following:
>>>>
>>>> Hello,
>>>>
>>>> In recent branches (confirmed with 224119) builds compiled with clang
>>>> happen to
>>>> throw 'Unknown error: -512' in a lot of places, making the system
>>>> unusable.
>>>> (Untested on gcc compiled systems). Originally I thought the problem was
>>>> with
>>>> specific programs, then I narrowed it down to file I/O, and now I've
>>>> narrowed it
>>>> down to open() with O_TRUNC. Without O_TRUNC there seems to be no issues
>>>> whatsoever. With O_TRUNC on open() it fails with that 'Unknown error:
>>>> -512' every
>>>> other time you run the program. Common issues, portsnap is affected,
>>>> making it
>>>> impossible to fetch/extract ports. As well as redirecting output in
>>>> shells eg
>>>> `echo 'hi'>  test` fails every other try. You have the same issue with
>>>> text
>>>> editors like `edit` where it fails every other save. There are no issues
>>>> with
>>>> `echo 'hi'>>  test` as there is no O_TRUNC, it only seems to be an
>>>> O_TRUNC error.
>>>>
>>>> Any tips? Otherwise I'll be looking into this today myself.
>>>
>>> Just a hint that you could try using DTrace syscall and fbt providers to
>>> see where
>>> in kernel (if in kernel) that -512 return value originates.
>>>
>>
>> Update:
>>
>> I've traced more and more into the kernel, and currently I have found the
>> following trace:
>>
>>>>> ufs_setattr() (in sys/ufs/ufs/ufs_vnops.c:507)
>> (In truncate a bunch of stuff is done, but it succeeds until VOP_SETATTR)
>>>>> vn_truncate() (in sys/kern/vfs_vnops.c:636)
>>>>> kern_openat() (in sys/kern/vfs_syscalls.c:1043)
>>>>> kern_open()   (in sys/kern/vfs_syscalls.c:1035)
>>>>> open() (in sys/kern/vfs_syscalls.c:1006)
>>
>> ufs_setattr() returns with -1 (EPERM)
>>
>> I'll continue to try to find the exact problem. A quick workaround currently
>> would probably be to use a different filesystem other than ufs, but then
>> again, I have no clue if other filesystems have the same issue.
>>
>> Hopefully that trace will help anyone who wants to help out.
>
> What UFS options do you have defined in your kernel?

    Also, what does mount say and have you tried running as root?
Thanks,
-Garrett