[LTP] [RFC PATCH 1/2] tst_acquire_device: clear first sectors of LTP_DEV
Cyril Hrubis
chrubis@suse.cz
Mon Feb 22 11:34:08 CET 2016
Hi!
> As we see in [1] ZAP_BOOTBLOCK is defined on all archs except SPARC.
> I could not find the exact reason why it's so, but tend to think
> that it was implemented to let ext{2,3,4} be created on the first
> partition of a Sun disk label. The thing is that with Sun disk labels
> it's absolutely fine to have the first partition starting at sector 0,
> which is used by the disk label itself:
>
> ~# fdisk -lu /dev/vdiska
>
> Disk /dev/vdiska (Sun disk label): 255 heads, 63 sectors, 3916 cylinders
> Units = sectors of 1 * 512 bytes
>
> Device Flag Start End Blocks Id System
> /dev/vdiska1 0 2104515 1052257+ 1 Boot
> /dev/vdiska2 2104515 62910540 30403012+ 83 Linux native
> /dev/vdiska3 0 62910540 31455270 5 Whole disk
>
> If mkfs.ext{2,3,4} overwrote the first two sectors, then
> 'mkfs.ext{2,3,4} /dev/vdiska1' would destroy the disk label.
>
> Clearing the first 512k of LTP_DEV solves this issue. I don't expect
> it to make a noticeable impact on test execution time. 512k is fine
> to cover superblocks of all file systems supported by libblkid [2].
> Just in case.
Sounds reasonable to me. I guess that we can remove the special cases
for the force flag once this is applied as well.
--
Cyril Hrubis
chrubis@suse.cz
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