* [linux-lvm] issue about return value in _lvchange_activate_single
@ 2020-11-17 3:52 heming.zhao
2020-11-17 15:45 ` David Teigland
0 siblings, 1 reply; 3+ messages in thread
From: heming.zhao @ 2020-11-17 3:52 UTC (permalink / raw)
To: LVM general discussion and development, David Teigland, Zdenek Kabelac
Hello List, David & Zdenek,
I met a boring problem when executing lvchange cmd.
In lvm tools/errors.h, there are defines return values:
```
#define ECMD_PROCESSED 1
#define ENO_SUCH_CMD 2
#define EINVALID_CMD_LINE 3
#define EINIT_FAILED 4
#define ECMD_FAILED 5
```
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;
return ECMD_PROCESSED;
```
So in special condition, lvchange cmd will return successfully but cmd executing failed.
the code should be changed to:
```
diff --git a/tools/lvchange.c b/tools/lvchange.c
index f9a0b54e3..ae626a05b 100644
--- a/tools/lvchange.c
+++ b/tools/lvchange.c
@@ -1437,6 +1437,7 @@ static int _lvchange_activate_single(struct cmd_context *cmd,
{
struct logical_volume *origin;
char snaps_msg[128];
+ int rv;
/* FIXME: untangle the proper logic for cow / sparse / virtual origin */
@@ -1465,8 +1466,10 @@ static int _lvchange_activate_single(struct cmd_context *cmd,
}
}
- if (!_lvchange_activate(cmd, lv))
+ rv = _lvchange_activate(cmd, lv);
+ if (!rv || rv>1) {
return_ECMD_FAILED;
+ }
return ECMD_PROCESSED;
}
```
maybe the same problem exist in other places of lvm2 source code.
how to trigger:
there is two nodes env, node1 & node2. they share 1 iSCSI lun disk.
node1 & node2 use systemid to control the shared disk.
1. node1 already use uname to set up systemid.
```
[tb-clustermd1 ~]# pvs --foreign
PV VG Fmt Attr PSize PFree
/dev/sda vg1 lvm2 a-- 292.00m 260.00m
[tb-clustermd1 ~]# vgs --foreign -o+systemid
VG #PV #LV #SN Attr VSize VFree System ID
vg1 1 1 0 wz--n- 292.00m 260.00m tb-clustermd1
[tb-clustermd1 ~]# lvs --foreign -o+Host
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert Host
lv1 vg1 -wi-a----- 32.00m tb-clustermd1
[tb-clustermd1 ~]# dmsetup ls
vg1-lv1 (254:0)
[tb-clustermd1 ~]#
```
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)
[tb-clustermd2 ~]#
```
3. this time both sides have dm device.
```
[tb-clustermd1 ~]# dmsetup ls
vg1-lv1 (254:0)
[tb-clustermd2 ~]# dmsetup ls
vg1-lv1 (254:0)
```
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
[tb-clustermd1 ~]# dmsetup ls
vg1-lv1 (254:0)
[tb-clustermd1 ~]# lvchange -an vg1/lv1 ; echo $?
WARNING: Found LVs active in VG vg1 with foreign system ID tb-clustermd2. Possible data corruption.
0
[tb-clustermd1 ~]# dmsetup ls
No devices found
[tb-clustermd1 ~]#
```
Thanks.
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [linux-lvm] issue about return value in _lvchange_activate_single
2020-11-17 3:52 [linux-lvm] issue about return value in _lvchange_activate_single heming.zhao
@ 2020-11-17 15:45 ` David Teigland
2020-11-18 14:45 ` heming.zhao
0 siblings, 1 reply; 3+ messages in thread
From: David Teigland @ 2020-11-17 15:45 UTC (permalink / raw)
To: heming.zhao; +Cc: Zdenek Kabelac, LVM general discussion and development
On Tue, Nov 17, 2020 at 11:52:28AM +0800, heming.zhao@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
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [linux-lvm] issue about return value in _lvchange_activate_single
2020-11-17 15:45 ` David Teigland
@ 2020-11-18 14:45 ` heming.zhao
0 siblings, 0 replies; 3+ messages in thread
From: heming.zhao @ 2020-11-18 14:45 UTC (permalink / raw)
To: David Teigland; +Cc: Zdenek Kabelac, LVM general discussion and development
On 11/17/20 11:45 PM, David Teigland wrote:
> On Tue, Nov 17, 2020 at 11:52:28AM +0800, heming.zhao@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
>
I recommend to use a define (e.g. E_COMM_ERR) not magic number (ZERO) to replace return value.
>> 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
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-11-17 15:45 ` David Teigland
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