[Cluster-devel] [PATCH 2/2] mkfs.gfs2: Open the target device with O_EXCL

[Andrew Price <anprice@redhat.com>]

On 05/04/16 15:14, Bob Peterson wrote:
> In fact, we used to have O_EXCL:
>
> https://git.fedorahosted.org/cgit/cluster.git/commit/gfs2/mkfs/main_mkfs.c?h=RHEL6&id=b0db0bad3e6a8996fcaecbb93bfe9f8de97b7508
>
> I remember Ryan doing this, but I'm not sure why or how it disappeared.
> We need to chase down why O_EXCL was removed last time; whether it was just
> an oversight/mistake or whether it caused problems elsewhere.

That check_mount() function opened the device to check whether it was 
mounted and then closed it again, leaving main() to open it again 
afterwards for writing. From the commit history it looks like the 
function was just removed because it was racey, nothing related to the 
use of O_EXCL specifically, so I don't think there's anything in the 
history to suggest that it's a bad idea.

Cheers,
Andy