[systemd-devel] udev blkid check on mmcblk0boot0 and boot1

[Alan Perry]

On 2/2/21 1:55 AM, Lennart Poettering wrote:
> On Mo, 01.02.21 16:36, Alan Perry (alanp at snowmoose.com) wrote:
>> Hi, Per the udev rules, the blkid builtin is run on mmcblk*boot* 
>> devices to look for partition and filesystem. Those devices contain 
>> hardware-specific boot information and are unlikely to have anything 
>> on them that blkid would identify. Why isn't there a rule to exclude 
>> them from blkid? Is there some case that I am missing? 
> Probably noone who cares about MMC enough prepped a patch for this so 
> far. Also it probably doesn't matter too much... I mean, if blkid 
> doesn't find anything it doesn't find anything, so not much bad 
> happened? If this matters to you, and it's really clear that there is 
> unlikely anything blkid-recognizable on it, then by all means, please 
> send a PR! 

I have been looking into a problem that we occasionally see with hangs 
at boot time during the probe of
mmcblk0boot0. Doing some searching, I have seen reports of similar hangs 
over the years, so I see a
potential benefit of not doing the probe.

Is the blkid/libblkid code robust enough that it could sanely handle 
whatever hardware-specific collection of
bits representing the boot configuration that happens to be there?

I had been planning on sending a PR. As I said, the idea seemed so 
obvious to me that I wanted to confirm that
it hadn't been considered and rejected at some point in the past before 
I did.

As far as the change itself, would it be something as simple as adding:

KERNEL!="mmcblk[0-9]boot[0-9]"

before the last clause of this rule:

# probe filesystem metadata of disks
KERNEL!="sr*", IMPORT{builtin}="blkid"


alan