[LTP] [PATCH] commands/mkswap01: Update wait_for_file function

[Stanislav Kholmanskikh <stanislav.kholmanskikh@oracle.com>]

On 02/25/2016 07:51 PM, Stanislav Kholmanskikh wrote:
>
>
> On 02/04/2016 04:17 PM, Cyril Hrubis wrote:
>> Hi!
>>>> Does actually the swapon in the verify function work? Since as far as I
>>>> can tell it actually opens the symlink in question in order to get the
>>>> swap device.
>>>>
>>>> Have you tried stracing it in case that the code waiting for the device
>>>> timeouted?
>>> I tried it with UEK.Sometimes waiting for device timeout but swapon
>>> works,i.e.:
>>>
>>> ...
>>> ...
>>>
>>> mkswap01 6 TINFO : Waiting for /dev/disk/by-label/ltp_testswap to appear
>>> mkswap01 6 TINFO : Waiting for /dev/disk/by-label/ltp_testswap to appear
>>> mkswap01 6 TINFO : Waiting for /dev/disk/by-label/ltp_testswap to appear
>>> mkswap01 6 TWARN : The file /dev/disk/by-label/ltp_testswap haven't
>>> appeared
>>> mkswap01 6 TPASS : 'mkswap -L ltp_testswap /dev/sda7 ' passed.
>>> ...
>>
>> That looks strange to me. Since if I strace 'swapon -L ltp_testswap' I
>> got:
>>
>> ...
>> stat("/dev/disk/by-label/ltp_testswap", 0x7ffef8293800) = -1 ENOENT
>> (No such file or directory)
>> ...
>>
>> Then it proceeds to exit with error. So I'm geniuely confused.
>
> Hmm, in my case swapon -L test does not fail, if there is no
> /dev/disk/by-label/test:
>
> root@skholman-m7 stas]# rm /dev/disk/by-label/test
> rm: remove symbolic link `/dev/disk/by-label/test'? y
> [root@skholman-m7 stas]# BLKID_FILE=/tmp/none strace swapon -L test &>
> /tmp/o; echo $?
> 0
> [root@skholman-m7 stas]# grep by-label /tmp/o
> stat64("/dev/disk/by-label/test", 0x7feff9b6130) = -1 ENOENT (No such
> file or directory)
> [root@skholman-m7 stas]#
>
> (but in the strace output I see that swapon tries to read some sectors
> from all available block devices)
>
> Maybe the version of libblkid plays a role here.
>
> Using 'blkid -t' simply makes wait_for_file/wait_for_device not fail if
> there is no /dev/disk/by-label/ symlink. I suppose 'blkid -t' could be
> substituted with /bin/true in my case.

My system doesn't provide /etc/blkid.conf

>
>>
>> Hmm but looking at blkid man page, it says that udev symlinks may depend
>> on settings in /etc/blkid.conf. That may be the difference after all.
>>
>> Looking at the manual page doing 'blkid -L ltp_testswap' and 'blkid -U
>> $UUID' should be the only correct solution. Does that work for you?
>>
>