[linux-lvm] issue about return value in _lvchange_activate_single
David Teigland
teigland at redhat.com
Tue Nov 17 15:45:16 UTC 2020
On Tue, Nov 17, 2020 at 11:52:28AM +0800, heming.zhao at suse.com wrote:
> In lvm functions, it treats "return 0" as error case.
>
> if _lvchange_activate() return ECMD_FAILED, the caller _lvchange_activate_single() think as normal:
> ```
> if (!_lvchange_activate(cmd, lv)) <== ECMD_FAILED is 5, won't enter if case.
> return_ECMD_FAILED;
Thanks for finding that. In some places 0 is the error value and in other
places ECMD_FAILED is the error value; they frequently get mixed up.
I believe this is the bug you are seeing:
https://sourceware.org/git/?p=lvm2.git;a=commit;h=aba9652e584b6f6a422233dea951eb59326a3de2
> 2. node2 change the systemid to itself
>
> ```
> [tb-clustermd2 ~]# vgchange -y --config "local/extra_system_ids='tb-clustermd1'" --systemid tb-clustermd2 vg1
> Volume group "vg1" successfully changed
> [tb-clustermd2 ~]# lvchange -ay vg1/lv1
> [tb-clustermd2 ~]# dmsetup ls
> vg1-lv1 (254:0)
This is what the LVM-activate resource agent does, except it wouldn't be
done while the LV is active on another running host. Just wanted to
clarify that, I don't think it's the point of your illustration here.
> 3. this time both sides have dm device.
> ```
> [tb-clustermd1 ~]# dmsetup ls
> vg1-lv1 (254:0)
> [tb-clustermd2 ~]# dmsetup ls
> vg1-lv1 (254:0)
> ```
For the sake of anyone looking at this later, this shouldn't happen in a
properly running cluster. (If you wanted the LV active on two hosts at
once, you'd use lvmlockd and no system ID on the VG.)
> 4. node1 executes lvchange cmds. please note the return value is 0
> ```
> [tb-clustermd1 ~]# lvchange -ay vg1/lv1 ; echo $?
> WARNING: Found LVs active in VG vg1 with foreign system ID tb-clustermd2. Possible data corruption.
> Cannot activate LVs in a foreign VG.
> 0
That's the one fixed by the commit above.
Dave
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