[Cluster-devel] [PATCH] gfs2_grow: Don't try to open an empty string

[Andrew Price <anprice@redhat.com>]

On 09/08/13 10:41, Steven Whitehouse wrote:
> Hi,
>
> On Thu, 2013-08-08 at 18:02 +0100, Andrew Price wrote:
>> sdp->device_name wasn't getting set in gfs2_grow so is_gfs2() (called
>> via check_for_gfs2()) fails to open "" and so we get an ENOENT.
>>
>> This fixes the open("") by setting sdp->device_name before passing it to
>> is_pathname_mounted(), which has been updated to make it more clear
>> which args will be modified by it.
>>
>> is_gfs2() and check_for_gfs2() have also been removed from libgfs2 as
>> these were the only places they were being called and they aren't
>> needed: superblock checking is done further along via other functions
>> calling check_sb().
>>
> Definitely an improvement over what we had before, but I wonder whether
> we can do better still. Is the fd always open before we call
> is_pathname_mounted() I wonder? If so we should be able to just pass the
> fd to it which reduces the possibility for races I think, and may also
> simplify things a bit more,

Well the problem here is that we don't know whether the path is a device 
or a mount point (gfs2_{grow,jadd} accept both) beforehand so any open 
before is_pathname_mounted() is called is going to be a guess.

I think we probably can improve on this function in the process of 
making libgfs2 more fd-centric but it'll take a bit more work so I'll 
come back to that later and push this patch independently as it solves a 
problem that's currently holding up testing.

Cheers,
Andy