Re: [PATCH 2/2 v4] btrfs-progs: optimize btrfs_scan_lblkid() for multiple calls

[Anand Jain <Anand.Jain@oracle.com>]

On 31/10/2014 17:08, Karel Zak wrote:
> On Fri, Oct 31, 2014 at 12:11:20PM +0800, Anand Jain wrote:
>> btrfs_scan_lblikd() is called by most the device related command functions.
>> And btrfs_scan_lblkid() is most expensive function and it becomes more expensive
>> as number of devices in the system increase. Further some threads call this
>
> wouldn't be possible to ask udev rather than scan all devices? I
> understand than in some cases it's necessary to have robust and
> independent solution, but for usual use-cases it would be less
> expensive to read the info from udev where we already keep track about
> all block devices and where we call libblkid.
>
> It would be possible to implement it as optional feature (#ifdev HAVE_LIBUDEV),
> the library API is very easy to use.
>
> (For example lsblk uses libblkid as fallback, the default is udev).
>
>      Karel
>
>

I might be missing something, correct me if wrong. Is there any udev API 
which gives me a list of devices which hold btrfs ? I just browsed
through there isn't any.

Anand