Hello Ryan Harper
>>
>> Hello Ryan Harper
>>>
>>> This happens in the initramfs for kernels which include bcache module. After the rootfs is
>>> mounted and we've pivoted into system boot, then the udev cold-plug replay will repeat
>>> the disk add/change events
>> I run bcache in Redhat and Centos OS, I haven't met such issue.
>> I am wondering, if udev cold-plug needs replay, it should also
>> repeat the bcache change uevent which produced in bcache device
>> registering, if so, the /dev/bcache/{by-uuid, by-label} should be
>> also generated.
>>>
Could you tell me why disk add/change events would be replayed, but bcache change events
which produced in bcache device registering would not be replayed during udev cold-plug
replay?
>>> but when the bcache register method runs a second time and
>>> finds a backing device, a bcacheN block device already has it open, so the module exits out
>>> the path of "device already registered" which prevents bcache from calling register_bdev()
>>> which is the only path where a backing device could call bch_cached_dev_run() which is
>>> responsible for emitting the KOBJ_CHANGE event which the bcache udev rules use to
>>> generate the /dev/bcache/{by-uuid, by-label} events.
>>
>> I am just worry about that, If every disk change uevents triggerd a
>> bcache device change uevents, there would be a lot of output messages
>> like "/dev/bcache/{by-uuid, by-label} has existed, and it was
>> created again..."
>
>Udev does not generate messages when it creates symlinks as far as I know.
>
>What you can see is the kernel messages when udev coldplugs devices:
>
>[2681476.651631] bcache: register_bcache() error opening
>/dev/nvme0n1p1: device already registered
>[2681477.082824] bcache: register_bcache() error opening /dev/sda3:
>device already registered
>[3283536.544468] bcache: register_bcache() error opening
>/dev/nvme0n1p1: device already registered
>[3283537.018570] bcache: register_bcache() error opening /dev/sda3:
>device already registered
>[3567850.400367] bcache: register_bcache() error opening
>/dev/nvme0n1p1: device already registered
>[3567850.855402] bcache: register_bcache() error opening /dev/sda3:
>device already registered
>
>In general, I don't think there are a large number, or frequent bcache
>CHANGE events outside of testing.
It seems OK.
>Ryan
Thanks,
Tang Junhui
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