Issue with 'Unknown Error: -512'

[Andriy Gapon]

on 19/07/2011 03:19 Brandon Falk said the following:
> 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)

But not -512, though.

> 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.

-- 
Andriy Gapon