Re: [PATCH] vfs: Return EINVAL for default SEEK_HOLE, SEEK_DATA implementation

[Jeff Liu <jeff.liu@oracle.com>]

On 01/05 2014 08:36 AM, Josef Bacik wrote:
> 
> On 01/03/2014 05:17 PM, Andreas Dilger wrote:
>> Shouldn't this be -EOPNOTSUPP, since -EINVAL is for incorrect
>> arguments, which isn't the case here.
>>
> I think we want to be consistent with previous kernels which would
> return -EINVAL if whence wasn't set properly, hopefully breaking as few
> userspace stuff as possible.  Thanks,

It seems like that this fix would have a bit influence to man page of lseek(2)
as it suppose to:

       EINVAL whence is not valid.  Or: the resulting  file  offset  would  be
              negative, or beyond the end of a seekable device.

Where probably need an update to reflect this change regardless of whether
return -EINVAL or -EOPNOTSUPP IMHO.

Moreover, Solaris/FreeBSD use {f}pathconf(2) syscalls to detect if a file
system is support SEEK_HOLE function or not, maybe Glibc/GNULib folks would
like to couple lseek(..., SEEK_HOLE) to {f}pathconf(3) in the future, which
could make the userspace stuff a bit more flexible across different OS.

So, I gone through their man pages and in this case, seems both of them will
return -EINVAL if call to {f}pathconf(2) with _PC_MIN_HOLE_SIZE is failed:

Solaris: http://docs.oracle.com/cd/E23824_01/html/821-1463/pathconf-2.html
FreeBSD: http://www.freebsd.org/cgi/man.cgi?query=pathconf&sektion=2


Thanks,
-Jeff