[Ovirt-devel] [RFC][PATCH v2] edit-livecd : fail on error in arbitrary code

[abhishek misra]

Hello All,

Below are David's comments on my last patch

David Huff wrote:
> I took a look at this today, I am not sure that a requirement for 'CODE'
> to touch a "fail" file is the best way to address this.
>
> I assume your script is mounting proc inside the ext filesystem, ie to
> use yum or something.  And using trap and a similar mnt function, like
> what is in edit-livecd, is not cleaning up all the mounts in this case?
>
> A fix may be to use /proc/mounts instead of df when adding the Exits in
> the mnt function.
>
> Also can you clarify the statement, "note that it may not always be
> possible to return some error code on failure in 'CODE'" I am not really
> sure what you mean here.
>
> Does this make sense?
>
> -D
>   
David, you were right about proc , I've now taken care of that in my 'CODE'

Here is another patch that tries to achieve the same without using 
'touch fail'

1.  removed compound statement ( list )
     I found that its usage does not prevent trap to come into action if 
$CODE fails (which is desired )
     but allows commands after (list) to continue executing ( which is 
not desired )

2   added addExit "cd -"
    when $CODE fails and control returns to edit-livecd script, it is 
still in $WDIR/ex
     this causes failure when trap attempts  umount

3   added EXIT=${EXIT/cd - ;/}
     we no longer need it if $CODE goes well

4  added cd -
    we need it as we removed (list)

5  removed set +/- e

Signed-off-by: Abhishek Misra <fishy at linux.vnet.ibm.com

---

--- a/edit-livecd    2009-11-10 17:23:21.000000000 +0530
+++ b/edit-livecd    2009-11-13 14:03:50.000000000 +0530
@@ -161,12 +161,11 @@ mnt "-t ext2 $WDIR/sq-w/LiveOS/ext3fs.im
 
 echo ">>> Updating CD content"
 if [ -n "$CODE" ]; then
-    (
       cd $WDIR/ex
-      set +e
+      addExit "cd -"
       eval "$CODE"
-      set -e
-    )
+      EXIT=${EXIT/cd - ;/}
+      cd -
 else
     echo "***"
     echo "*** Pausing to allow manual changes.  Press any key to continue."